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INVESTIGATION OF SELECTED POTENTIAL ENVIRONMENTAL CONTAMINANTS: ASPHALT AND COAL TAR PITCH FINAL REPORT ENVIRONMENTAL PROTECTION AGENCY OFFICE OF TOXIC SUBSTANCES WASHINGTON, D.C. SEPTEMBER

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 EPA/ INVESTIGATION OF SELECTED POTENTIAL ENVIRONMENTAL CONTAMINANTS: ASPHALT AND COAL TAR PITCH Ruth P. Trosset, Ph.D David Warshawsky, Ph.D. Constance Lee Menefee, B.S. Eula Binghara, Ph.D. Department of Environmental Health College of Medicine University of Cincinnati Cincinnati, Ohio Contract No.: Final Report September, Project Officer: Elbert L. Dage Prepared for Office of Toxic Substances U.S. Environmental Protection Agency Washington, D. C. Document is available to the public through the National Technical Information Service, Springfield, Virginia

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 NOTICE This report has been reviewed by the Office of Toxic Substances, Environmental Protection Agency, and approved for publication. Approval does not signify that the contents neces- sarily reflect the views and policies of the Environmental Pro- tection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

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 - 1 - TABLE OF CONTENTS Executive Summary Introduction Glossary 6 I. PHYSICAL AND CHEMICAL PROPERTIES 8 A. Bituminous Materials 8 B. Asphaltic Materials 11 1. Petroleum Asphalt 11 a. Composition of Crude Oil 11 b. Types of Petroleum Asphalts 12 c. Fractionation of Asphalt 13 2. Native Bitumens 22 a. Native Asphalts 22 b. Asphaltites 23 C. Coal Tar Pitch 24 1. Source 24 2. Physical Properties 29 3. Chemical Properties 30 II. ENVIRONMENTAL EXPOSURE FACTORS: ASPHALT 40 A. Production and Consumption 40 1. Quantity Produced 40 2. Market Trends 40 3. Market Prices 43 4. Producers and Distributors 43 5. Production Methods 44 B. Uses 50 1. Major Uses 50 a. Paving 50 (1) Production and Consumption 50 (2) Materials 52 (3) Process Descriptions 53 b. Roofing 55 (1) Production and Consumption 55 (2) Products and Materials 58 (3) Process Descriptions 59 2. Minor Uses 61 3. Alternatives to the Use of Asphalt 62

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 TABLE OF CONTENTS (continued) C. Environmental Contamination Potential 63 1. Controlled and Uncontrolled Emissions 63 a. Air Blowing 63 b. Roofing Mills 65 c. Hot Mix Plants 66 d. Paving 68 2. Contamination Potential of Asphalt Transport and Storage 69 3. Contamination Potential from Disposal 69 4. Environmental Contamination Potential from Use 70 5. Weathering and Microbial Degradation 71 III. ENVIRONMENTAL EXPOSURE FACTORS: COAL TAR PITCH 75 A. Production and Consumption 75 1. Quantity Produced 75 2. Market Trends 75 3. Market Prices 75 4. Producers and Distributors 81 5. Production Process 83 B. Uses 85 1. Major Uses 85 2. Minor Uses 87 C. Environmental Contamination Potential 88 1. Emissions from Production 88 a. Coke Ovens and Tar Distilleries 88 b. Graphite Manufacture 88 c. Other Production Processes 91 2. Contamination Potential from Storage, Transport and Disposal 91 3. Contamination Potential from Use 93 4. Weathering 94 IV. ANALYTICAL METHODS 96 A. Sampling 96

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 - Ill - TABLE OF CONTENTS (continued) B. Methods of Sample Analysis 99 1. Separation Schemes 99 a. Solvent Extraction and/or Precipitation 99 b. Solid-Liquid Extraction c. Distillation d. Chromatography 2. Identification iMethods a. Infrared Spectroscopy (IR) b. Fluorescence and Phosphorescence Spectroscopy c. Mass Spectrometry (MS) d. Nuclear Magnetic Resonance Spectrometry (NMR) e. Ultraviolet Spectroscopy (UV) f. Other Techniques 3. Discussion of Existing and Proposed Analytical Methods C. Monitoring V. TOXICITY AND CLINICAL STUDIES IN MAN A. Effects on Organ Systems 1. Effects of Asphalt a. Effects on the Skin b. Effects on the Respiratory System 2. Effects of Coal Tar Pitch a. Effects on the Skin b. Effects on the Eyes c. Effects on the Respiratory System d. Other Effects B. Effects of Occupational Exposure 1. Exposure to Asphalt a. Refineries b. Other 2. Exposure to Coal Tar Pitch a. Exposure during Production of Pitch b. Exposure during Use (1) Electrodes (2) Patent Fuel (Briquettes) (3) Other

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 - iv - TABLE OF CONTENTS (continued) 3. Combined Exposure to Asphalt and Coal Tar Pitch a. Roofing b. Paving 4. Prevention of Occupational Disease C. Effects of Experimental Exposure to Coal Tar Pitch D. Effects of Experimental and Therapeutic Exposure to Coal Tar Medications VI. BIOLOGICAL EFFECTS ON ANIMALS AND PLANTS A. Effects on Mammals and Birds 1. Poisonings 2. Toxicity a. Coal Tar and Pitch b. Coal Tar Medications 3. Carcinogenicity a. Introduction b. Asphalt c. Tars and Pitches Derived from Coal (I) Coal Tar (2) Heavy Tars or Pitches (3) Coal Tar Pitch (4) Coal Tar Medications (5) Other Coal-Derived Tars B. Effects on Other Animals 1. Fish 2. Invertebrates C. Effects on Vegetation D. Effects on Microorganisms E. In Vitro Studies

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 - v - TABLE OF CONTENTS (continued) Page VII. REGULATIONS AND STANDARDS A. Current Regulations 1. Environmental Protection Agency 2. Department of Transportation 3. Occupational Health Legislation in Various Countries 4. Department of Labor, Occupational Safety and Health Administration (OSHA) a. Coal Tar Pitch Volatile Standard b. Coal Tar Pitch Volatile Standard Contested 5. Department of Health, Education, and Welfare, National Institute for Occupational Safety and Health (NIOSH) a. Criteria Document: Asphalt b. Criteria Document: Coal Tar Products c. Registry of Toxic Effects of Chemical Substances B. Consensus and Similar Standards 1. National Safety Council (NSC) 2. American Conference of Governmental Industrial Hygienists (ACGIH) VIII. TECHNICAL SUMMARY IX. RECOMMENDATIONS AND CONCLUSIONS X. REFERENCES List of Information Sources

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S. Petroleum Industry 45 II-3 Employment Size of Establishments (SIC ) Paving Materials 51 II-4 The Top Ten Paving Mix Producers: 51 II-5 Suggested Mixing and Application Temperatures for Asphaltic Materials 56 II-6 Employment Size of Establishments (SIC ) Roofing Materials 57 III-l Crude Tar Production and Processing: (Pitch Production 76

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 - viii - LIST OF FIGURES Number Page Partial Classification of Bituminous Materials 9 Fractionation of Asphalt 16 Stepwise Fractionation of Various Components of Asphalt 20 Origin of Coal Tar Pitch 27 II-l Annual Domestic Sales of Asphalt by Major Markets 42 II-2 Refinery Steps in the Production of Asphalt 47 III-l Crude Coal Tar Produced and Processed in By-Product Coke Ovens 77 III Annual Pitch Production and Sales 78

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 - 1 - EXECUTIVE SUMMARY Asphalt and coal tar pitch are bituminous materials used as binders, saturants and weatherproof coatings. Although they are similar in certain physical properties, they differ markedly in origin, composition, major uses, and severity of biological effects. Asphalt Petroleum asphalt is the residue, essentially uncracked, from the fractional distillation of crude oil. Small amounts of naturally occurring asphaltic materials are also used. Commercial grades of asphalt are prepared to meet standard specifications based on physical properties. Base stocks of asphalt can be formulated from residues of distillation, solvent deasphalting, or air blowing processes. Liquid (cutback) asphalts are prepared by diluting base stocks with organic solvents. Emulsions of asphalt and water are also used. Since annual asphalt sales in the United States have averaged 31 million tons. Seventy-eight percent of the asphalt is used in paving, 17% in roofing, and 5% in miscellaneous applications, including dam linings, soil stabilizers and electrical insulation. Emissions from airblowing and from manufacture of paving and roofing materials have not been well characterized, but may contain entrained as- phalt droplets, gases, trace metals, hydrocarbons, and large quantities of particulates which may contain polynuclear aromatic hydrocarbons (PAH), several of which are carcinogens. A ninety-nine percent control level of the emissions from asphalt production and processing is possible using currently available thermal

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 - 2 - afterburners (fume incinerators) in conjunction with wet scrubbing units. Installation of paving and roofing materials may be a localized source of air pollution. Emissions can be greatly reduced by maintaining the asphalt heating kettle temperature below °C during roofing operations, and by using emulsions to replace cutback asphalts for paving. Vast surfaces of asphalt covered roads, parking lots, runways and play- grounds are subject to microbial, chemical and physical degradation, which may produce some polycyclic aromatic, heterocyclic, and metallic substances, possibly toxic or carcinogenic, in air, waterways and sediments. Limited animal skin painting and inhalation studies suggest that as- phalt may be, at most, weakly carcinogenic. Other health hazards have not been demonstrated. Few human exposure studies are available. Harmful effects from asphalt cannot be identified in exposures to mixtures of asphalt and the more bio- logically potent coal tar pitch, which have been common in paving, roofing, and weatherproofing operations. It is generally agreed that asphalt is a relatively harmless material to workers under proper working conditions (U.S. National Institute for Occupational Safety and Health, a). Present regulations limit particulate emissions from new asphalt hot mix plants and regulate effluent levels for new and existing paving and roofing point sources using tars and asphalts. The NIOSH recommended standard for occupational exposure to asphalt fumes is 5 mg airborne particulates per cubic meter of air (U.S. National Institute for Occupational Safety and Health, a). Although the OSHA standard on "coal tar pitch volatiles" has been interpreted to include asphalt, the standard has not been successfully enforced.

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 - 3 - Coal Tar Pitch Crude coal tar is a highly cracked product evolved during carbonization of coal. All coal tar pitch commercially available in the U.S. is the distil- - lation residue of by-product coke oven tar. The amount of pitch produced has declined from 2,, tons in to 1,, tons in About 62% of this pitch is used as a binder or impregnant in carbon and graphite products. The largest single carbon product market is for carbon anodes used in primary aluminum manufacture. About 17% of the pitch produced is burned as an open-hearth furnace fuel, and 7% is used for the manufacture of "tar" saturated roofing felt and for certain commercial roofs. A stable market for pitch (10, tons annually) has been its use as a binder in "clay pigeons" for skeet shooting. Pitch bonded and pitch impregnated re- fractory bricks used to line basic oxygen furnaces, blast furnaces and foundry cupolas represent a steadily growing market. Pitch can undergo the same basic processing as does asphalt, namely air blowing, dilution with coal tar solvents, or emulsification with water. Emissions from manufacturing processes using pitch may include large amounts of pitch dust as well as pitch volatiles. Air pollution control measures used for asphalt fumes can also be used to contain emmissions from pitch. Large amounts of volatiles are emitted during the production of prebaked and graphi- tized pitch-containing carbon products, a major use of pitch. During use of such materials, higher levels of emissions are generated by self-burning elec- trodes than by those that have been prebaked or graphitized before use. A large proportion of workers exposed to pitch and sunlight develop moderate to severe acute phototoxic reactions of the skin and eyes. Exposure to pitch and coal tar can cause skin cancer (U.S. National Institute for Occupa- tional Safety and Health, b). Inhalation of fumes and particulates may be

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 - 4 - related to increased incidence of lung cancer. Some cases of cancer of the bladder and certain other organs may be related to exposure to coal tar pitch. Although they do contain carcinogenic PAH, topical medications based on crude coal tar, which have been widely used for the prolonged treatment of chronic skin diseases, do not appear to have caused cancer in humans when properly used. Some attempt has been made to control worker exposure to emissions from coal tar pitch. The present standard for "coal tar pitch volatiles" (other than coke oven emissions) specifies that worker exposure to airborne con- centrations of pitch volatiles (benzene soluble fraction) shall not exceed mg per cubic meter of air (U.S. Department of Labor, ) . The cur- rent interpretation of the coal tar pitch volatile standard covers volatiles from distillation residues not only of coal, but also of other organic ma- terials including petroleum (i.e., asphalt). Because coal tar pitch vola- tiles are considered carcinogenic, the National Institute for Occupational Safety and Health (b) has recommended a standard for occupational ex- posure to coal tar products, including coal tar pitch, of mg cyclohexane solubles per cubic meter of air (the lowest detectable limit). Examination of the literature indicates that the biological effects of asphalt are probably limited. Large quantities, however, are processed and the major uses are in roofing and paving products that are permanently ex- posed to slow degradation in the environment. Coal tar pitch, on the other hand, produces acute effects in a large proportion of exposed workers as well as possible increased risk of cancer of several sites after prolonged ex- posure. The major uses of pitch involve occupational rather than environmental exposure.

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 - 5 - INTRODUCTION Asphalt and coal tar pitch are used in a variety of industrial pro- cesses and manufactured products that utilize their properties as thermoplastic, durable, cementitious, water-resistant materials. The Environmental Pro- tection Agency, Office of Toxic Substances, has requested a preliminary literature investigation of the environmental contamination potential of these two bituminous materials. This noncritical review is intended to serve as a source of information to be used in evaluation of the severity of the environmental hazard and the need for further action concerning these two materials. In this report, "asphalt" is considered to be the residue, essentially uncracked, from the fractional distillation of crude petroleum. Coal tar pitch is defined as the residual product from the distillation of crude coal tar, a cracked material, which is formed during the coking of coal. A survey of the literature since was conducted, referring to older literature when recent information was unavailable. The literature review includes composition and properties; production figures and process descriptions; contamination potential from manufacture and use,' analysis,' toxicity and carcinogenicity to humans, animals, and plants; recommended handling practices; legislation; and standards. Conclusions and recommendations based on the literature are also presented.

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 - 6 - GLOSSARY ASPHALT - A black to dark-brown solid or semisolid cementitious material in which the major constituents are bitumens. Asphalt occurs naturally (asphaltites and native asphalts) or is obtained as the residue, essentially uncracked, from the straight distillation of petroleum. BITUMEN - A mixture, completely soluble in carbon disulfide, of hydro- carbons of natural and/or pyrogenous origin and their nonmetallic deriva- tives . BITUMINOUS MATERIAL - A mixture, containing bitumen or constituting the source of bitumen, occurring as natural (asphaltite, tar sand, oil shale, petroleum) or manufactured (coal tar pitch, petroleum asphalt, wax) material. COAL TAR - A brown or black bituminous material, liquid or semisolid in consistency, obtained as the condensate in the destructive distillation (coking) of coal, and yielding substantial quantities of coal tar pitch as a residue when distilled. COAL TAR PITCH - A black or dark-brown material obtained as the residue in the partial or fractional distillation of crude coal tar. As con- trasted to petroleum asphalt, which is essentially uncracked, coal tar pitch is a highly cracked material.

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 - 7 - COAL TAR PITCH VOLATILES - The fumes from the distillation residue of coal tar. In legal use, this term refers to the volatiles from the distillation residues of coal, petroleum or other organic matter. In this report, use of this term in connection with asphalt fumes has been avoided except in discussion of the legal definitions. CRACKING - A process (e.g., pyrolysis, thermal treating, coking) whereby large molecules (as in oil or coal) are decomposed into smaller, lower boiling molecules, while reactive molecules thus formed are recombined to create large molecules (including PAH) different from those in the original stock. PETROLEUM PITCH - A cracked product resulting from pyrolysis of gas oil or fuel oil tars. Because it shares certain properties with coal tar pitch, it has been suggested as a replacement for it in some applications. This term should never be used to refer to an asphalt product. Petroleum pitch is not included within the scope of this report. Abbreviations: BaP Benzo(a)pyrene BeP Benzo(e)pyrene CTPV "Coal tar pitch volatiles" (see Glossary) PAH Polynuclear aromatic hydrocarbons PNA Polynuclear aromatic compounds, including both hydrocarbons and heterocyclics (use in this report has been avoided) PPOM Particulate polycyclic organic matter

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 - 8 - I. PHYSICAL AND CHEMICAL PROPERTIES A. Bituminous Materials Asphalt and coal tar pitch belong to a group known as bituminous materials. Bitumens are defined as mixtures of hydrocarbons and their norunetallic deri- vatives of natural or manufactured origin, which are completely soluble in carbon disulfide (Hoiberg, a,b). In British and European usage, however, the term "bitumen" is used to refer to the material known in the United States as "asphalt," Among the many ma- terials which may be considered as bituminous, only native and manufactured asphalts and manufactured coal tar pitch, as shown in Figure , will be dis- cussed in this review. Asphalt is a dark brown to black cementitious solid or semisolid material, composed predominantly of high molecular weight hydrocarbons, occurring either as a native deposit or as a component of crude petroleum, from which it is separated as a distillation residue without pyrolysis. The asphalt content of crude oils varies from 9 to 75% (Ball, ), and the nature of the asphalt varies with its parent crude. About 98% of the asphalt used in the United States is derived from crude petroleum (Miles, ). Coal tar pitch is the distillation residue of crude coal tar, which is a pyrolysis product from the high temperature carbonization (coking) of coal. Coal tar pitches, brownish black to black in color and containing at least compounds, range from viscous liquids at ordinary temperature to materials which behave as brittle solids exhibiting a characteristic conchoidal fracture (McNeil, ).

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 msliUation Gas Oil, 'icatinq OiU,ekc. cok« «n o V RESIDUE JNlWE Native A Gmharnite, Manjak Native/ Asphalts Truiidadl fLake SancU Bermurlez Cnke Asphalt .. Oil X Oil Cteosobe. ^{JkrtUjerve, OIL, ebc. FIGURE PARTIAL CLASSIFICATION OF BITUMINOUS MATERIALS

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 - 10 - Because the uses of asphalt and pitch depend largely on physical prop- erties, specifications are based on empirical tests using strictly defined procedures. Most of these tests are covered by standards of the American Society for Testing and Materials (ASTM) () and the American Associa- tion of State Highway Officials (AASHO). The Asphalt Institute (a) presents brief descriptions of tests and methods for asphalt. A few of these tests are as follows: Penetration - a measure of consistency expressed as the distance, in tenths of a millimeter, that a standard needle penetrates under known conditions of loading, time and temperature. Softening point (ring and ball,, R & B) - the temperature at which a standard weight ball sinks below the bottom of a standard ring containing asphalt. Viscosity - a measure of the consistency of asphalt at two set temperatures. Normally, the viscosity-graded asphalt cements are identified by viscosity ranges at 60 and °C.. Sixty degrees is the approximate maximum temperature used in pouring asphalt, and °C is the approximate mixing and laydown temperature for hot asphalt pavements. Flash point - the temperature to which asphalt may be safely heated without an instantaneous flash in the presence of an open flame. Ductility - the distance in air which a standard briquet at 25°C can be elongated before breaking. Solubility - a measure of purity of the asphalt, determined by dissolving the asphalt in trichloroethylene and separating the soluble and insoluble portions by filtration. Water content - generally measured by refluxing asphalt product with

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 - 11 - xylol or high-boiling-range petroleum naphtha and collecting and measuring the water condensate in a trap. Specific gravity - the ratio of the weight of a given volume of bituminous material to that of an equal volume of water at the same temperature, usually reported as 77/77°F. B. Asphaltic Materials 1. Petroleum Asphalt a. Composition of crude oil As indicated in the beginning of this chapter, the asphalt content of crude oil varies (%) and the nature of asphalt varies with its parent crude. Crude oil is a very complex mixture and no single crude oil has ever been completely defined (Rossini and Mair, , ; Rossini et al., ; Altgelt and Gouw, ). The enormous diversity of different crude oils extends from light oils to heavy types found in asphalt lakes. These variations are found not only in the viscosity, but also in the content and length of paraffinic chains, number of aromatic carbon atoms, degree of ring fusion and type and amount of hetero atoms. More than several hundred compounds have been identified in Ponca City (Oklahoma) crude oil. They have been classified into nonpolar and polar materials. The nonpolar group includes straight chain alkanes, (hexane, pentane), branched alkanes .(isooctane), cycloalkanes (butylcyclohexane), and aromatics (propylbenzene and propyltettralin). The polar group in- cludes acids such as naphthenic acids, phenols, alkylthiols, cycloalkylthiols, alkylthiophenes, pyridines, quinolines, indoles, pyrroles and porphyrins. Nickel ( ppm, Berry and Wallace, ) and vanadium ( to weight percent) are the most prominent trace metals that occur in petroleum (Atlas and Bartha, ; Yen, ). Calcium, magnesium, titanium, cobalt, tin,

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 - 12 - zinc, and iron are also metals commonly found in crude petroleum. These metals tend to accumulate in the residue. b. Types of petroleum asphalts Distillation is the primary means for separating crude petroleum fractions. Asphalt is the high-boiling residual fraction. Crude oil may be distilled first at atmospheric pressure to remove the lower boiling fractions such as gasoline or kerosine and then can be further processed by vacuum distillation, leaving a straight-run asphalt. The asphaltic residue may also be processed with liquid propane or butane. Vacuum distillation and propane deasphalting both affect the hardness of the residue. When processed from the same stock, propane deasphalted residue differs little from straight-run residue (Corbett, ; Hoiberg e_t al., ; Hoiberg, a). Straight-run asphalt accounts for 70 to 75% of all the asphalt produced. Airblown asphalts with modified properties as compared to straight run asphalt are produced from the asphalt stock by treatment with air at tempera- tures of to °C. Catalysts such as phosphorus pentoxide, ferric oxide or zinc chloride/used in concentrations from to 3%xreduce the air blowing time. The asphalt undergoes dehydrogenation and polymerization by ester formation and carbon linkage (Smith and Schweyer, ; Haley, ; Corbett, ) during these processes. The presence of dicarboxylic anhydrides in oxidized asphalts has been confirmed by infrared spectroscopy (Petersen et al., ). There is a decrease in the aromatic resin content and an increase in the asphaltene content and hydrogen bonding basicity of airblown asphalt (Harbour and Petersen, ). Air blowing results in a product with a higher softening point for given penetration than straight reduced asphalt, while catalytic air blowing produces a still higher softening point. Air blown asphalt, which accounts for 25 to 30% of asphalts used, is a

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 - 13 - viscous .material that is less susceptible to temperature change than straight run asphalt. Treatment of asphalt at high temperature (°C) and pressure ( psig) produces thermal asphalts, less than 5% of total production of asphalt, which are not commonly available because catalytic cracking for the production of gasoline has largely replaced thermal cracking. Such asphalts are characterized by a relatively high specific gravity, low viscosity and poor temperature susceptibility (little change in consistency with increased temperature). They have a lower hydrocarbon to carbon ratio than, straight run asphalts. Highly cracked residues have infrared spectra similar to those of coal tar pitches CCorbett, ; Hoiberg £t a^., ; Hoiberg, a). The vis- cosity is more susceptible to temperature change in thermal asphalts than in straight run asphalt. An elemental analysis of asphaltic residues (% by weight) shows carbon ranging from 80 to 89%, hydrogen from 7 to 12%, oxygen from 0 to 3%, sulfur from trace to 8% and nitrogen from trace to 1% (Table ). c. Fractionatipn of asphalt The high molecular weight (M.W. ) asphaltene fraction is precipi- table by n-pentane, hexane or naphtha and, despite source, appears constant in composition as determined by carbon-hydrogen analysis. Asphaltenes are solid at room temperature and show some degree of crystallinity by X-ray diffraction. The concentration of asphaltenes to a large extent determines the viscosity of asphalt (Altgelt and Harle, ; Reerink, ; Reerink and Lijzenga, ) . Maltenes, the nonprecipitated fraction, are generally considered to contain resins CM.W. ) characterized by high temperature susceptibility that are either adsorbed on activated clays or precipitated by sulfuric acid

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 TABLE I-l. ELEMENTAL ANALYSES OF ASPHALT FRACTIONS AND NATURAL ASPHALTS Softening Penet point (ring and ball) °C .ration, Elemental analyses, % by wt c,°r ratio, C H S N Oa C/H Petroleum Straight run asphaltenes petrolenes Air-blown asphaltenes petrolenes Highly cracked 50 36 asphaltenes petrolenes Native Trinidad Bermudez 88 87 80 82 .9 .9 .9 5 7 10 10 .9 .9 .7 .8 3 3 6 5 .0 .7 .8 .9 0 0 0 0 .4 .5 .8 .8 1 0 0 0 a Oxygen determined by difference Sources: Hoiberg e_t al^. ,

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 - 15 - or a solvent (acetone, isobutyl alcohol, propane). The nonprecipitable maltene fraction consists of oils (M.W. ) which may contain appreciable quantities of wax and are characterized by low temperature susceptibility. The petrolene fraction (M.W. ) boils below °C and is soluble in low-boiling saturated hydrocarbons such as n-pentane. In addition, asphalts may contain saponifiable material and acids, the content of which is determined as percent naphthenic acids in the original crude (Corbett, ; Hoiberg, a; Hoiberg ejt al_., ). Most separations of asphalt into its constitutional components rely on some type of preliminary fractionation (Figure ) prior to the use of gel permea- tion, gas-liquid, paper, gravity fed column or high performance chromatography (Couper, ; Schweyer, ). The fractions obtained are then further analyzed by use of ultraviolet spectrometry, nuclear magnetic resonance, infrared spectros- copy, electron spin resonance, atomic absorption or X-ray diffraction, as de- scribed in Chapter IV. Five principal operations (distillation, extraction, adsorption, precipi- tation and chromatography) are used in various combinations for the fractionation of asphaltic bitumens (Rostler, ; Hoiberg, a; Hoiberg £t al_., ) to produce a variety of fractions that can be classified into a few general groupings (Figure ). However, none of these fractionation methods have provided satisfactory results when used separately. Distillation Distillation is used to concentrate the asphaltenes and maltenes and to separate out the petrolenes. However, this method by itself is not useful as an analytical separation procedure for complex mixtures (Hoiberg,).

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 ASPHALT n-pentane 4- 4 Insoluble So ASPHALTENES MAL luble TENES extraction, precipitation or column chromatography 4, -J' OILS RESINS FIGURE FRACTIONATION OF ASPHALT

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 - 17 - Extraction Carbon disulfide has been used in the separation of asphalt into low boiling petrolenes and a residual fraction, while n-pentane has been used as a means of fractionating asphalt into asphaltenes and raaltenes. However, these types of extractions give only a partial separation of asphalts (Rostler, ). A more complex separation involves the Hoiberg method (Hoiberg and Garris, ) which separates the asphalt stepwise into five fractions: (1) asphaltenes (2) hard resins, (3) waxes, (4) soft resins, and (5) oils. The Traxler-Schweyer method (), a simplified Hoiberg method, consists of stepwise separation into (1) asphaltenes precipitated by n-butanol and (2) a n-butanol-soluble fraction consisting of paraffins and naphthenes. Lastly, the method of Knowles et al. () involves stepwise fractionation into-(l) asphaltenes, (2) soft and hard resins, (3) waxes and (4) paraffinic and naphthenic oils. This last method is valuable because it separates asphalts into waxes, two types of resins and two kinds of oils. Adsorption Fractionation by adsorption has involved charcoal, charcoal and sand, and various kinds of molecular sieves. Early methods consisted of heating mixtures of liquid bitumens with adsorbents such as charcoal and fuller's earth, followed by filtration. They are considered the predecessors of modern chromatographic methods, which use the principles of both solvent extraction and adsorption. Molecular sieves can still be considered to be a relatively new tool which is being incorporated into separation procedures for asphaltic bitumens (Rostler, ; Couper, ).

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 - 18 - Chroma tography A number of fractionation methods have used chromatography, either by itself or in combination with extraction and adsorption methods. Silica gel is used to separate maltenes into resins and oils and maltenes or asphal-- tenes into non-aromatics, aromatics and polar compounds. The Glasgow-Ter- mine method, which also uses silica gel, elutes two pentane fractions and one fraction each of benzene, carbon tetrachloride and ethanol, while the Hubbard-Stanfield method involves (1) precipitation of asphaltenes with n-pentane, (2) elution of oils from alumina with n-pentane and (3) elution of resins from alumina with methanol-benzene mixture. In each of these methods, however, the overlapping of components from each fraction is typi- cal for these chromatographic techniques (Rostler, ). Two elaborate methods have been attempted by Kleinschmidt () and O'Donnell (). The Kleinschmidt method involves (1) precipitation of asphaltenes with n-pentane, (2) elution of the n-pentane soluble fraction from fullers earth to obtain (a) white oils with n-pentane, (b) dark oils with methy- lene chloride/ (c) asphaltic resins with methyl ethyl ketone, ar.d (d) a black residue desorbed with a mixture of acetone and chloroform. The O'Donnell method involves molecular distillation on the basis of molecular size followed by silica gel chromatography to separate saturates, aromatics, and resins. The saturates are dewaxed followed by urea-complex formation to separate long chain paraffins, and the aromatics are separated by alumina chromatography into mono- and di-cyclic aromatics, followed by peroxide oxidation and another chromatography to separate the benzothiophene analogs.

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 - 19 - Precipitation The chemical precipitation methods, use excess amounts of reagents to remove one component or fraction from the complex mixture. One method (Rostler, ) involves the precipitation of asphaltenes by low boiling hydrocarbons, followed by precipitation with sulfuric acid. The Rostler-Sternberg method () in- volves precipitation of asphaltenes with n-pentane and selective precipitation of the nitrogen bases and acidaffins 1 and 2 by use of successive concentrations of H2SC>4 (85%, 98%, fuming (S03)). The applicability of these methods to complex mixtures is still under investigation. A more recent method by Corbett () uses n-heptane, benzene, and methanol-benzene-trichloroethylene as solvents to obtain petrolenes, asphaltenes, saturates, aromatics and polar fractions. All of the methods and combinations described above, as well as others described in reviews (Couper, ; Schweyer, ; Altgelt and Harle, ), have been used in analysis of the complex mixtures of various types of asphalts. Figure shows a composite stepwise fractionation of the various components of asphalt. Techniques such as solvent fractionation, thermal diffusion and sulfuric acid precipitation and chromatography have yielded asphaltic fractions that have been examined using infrared (Petersen et al., ) and ultraviolet specr troinetryr X-ray diffraction, nuclear magnetic resonance, electron spin reson-r ance and:atomic absorption (Couper, ). Little is known at present about polynuclear aromatic hydrocarbons (PAH) in asphalt. Wallcave et al. () have presented average concentrations of PAH in asphalt obtained from various sources (Table ). More work needs to be done in the area of PAH determinations in asphalt.

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STEPWISE FRACTIONATION OF VARIOUS COMPONENTS OF ASPHALT

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 TABLE * CONCENTRATION AVERAGES OF SEVERAL PARENT PAH IN ASPHALT (ppm) Asphalt Phenanthrene Pyrene Benz[a]- anthracene 1 2 3 4 5 6 7 8 ^35 ' ^ 38 35 Tri- phenylene Chrysene Benzo[a]- pyrene 34 27 Benzofe]- Perylene Benzofghi]- Coronene pyrene perylene - 13 39 w ' 52 15 - Trace Benzofluorenes, fluoranthene, benzo[k]fluoranthene, anthracene, picene and indeno[l,2,3-cd]pyrene are present in trace amounts. Source: Wallcave et al^v

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 - 22 - As indicated previously, some of the metals present in crude oil tend to accumulate in the asphalt. Vanadium, nickel, and iron tend to be concentrated in the asphaltene fraction (Corbett, ), Vanadium chelates have been studied in petroleum asphaltenes (Tynan and Yen, ; Wolsky and Chapman, (). Other metals are bound to polynuclear aromatic compounds containing sulfur, nitrogen and oxygen polar groups as well as naphthenic and paraffinic side chains. During air blowing, these polynuclear aromatics are converted to asphaltenes. Removing the asphaltene fraction from blown asphalt can re- move up to 97% of the organometallics. 2. Native Bitumens Native bitumens include a wide variety of natural deposits ranging in character from crude oil to sand and limestone strata impregnated with bi- tuminous material. Only a few of these materials are classified as asphalts. a. Native asphalts The native asphalts include a variety of reddish brown to black materials of semisolid, viscous-to-brittle character. They can occur in relatively pure form, with 92 to 97% soluble in carbon disulfide and only 3 to 8% mineral con- tent, as is the case for Bermudez (Venezuela) lake asphalt, or in less pure form, wi-ch a carbon disulfide-soluble fraction of 39% and a mineral content of 27%, as is the case for Trinidad lake asphalt (Table ). Trinidad lake as- phalt is dull black and semiconchoidal in fracture, with a penetration of 10 at 30°C and a softening point (R & B) of 85° c. When gas and water are driven off at °c, Trinidad asphalt loses 29% of its weight and the carbon disulfide- soluble fraction increases to 56% while the mineral content increases to 38%.

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 - 23 - Frequently, the bitumen is found in pores and crevices of sandstones, limestones or argillaceous sediments and is known as rock asphalt. The term "tar sands" has been used by geologists to designate sands impregnated with dense, viscous asphalt found in certain sedimentary structures, such as the Athabasca tar sands now being mined in Alberta, Canada (Hanson, ; Broome, ; Camp, ; Breger, ). b. Asphaltites Asphaltites are naturally occurring, dark brown to black, solid, and relatively nonvolatile bituminous substances differentiated from native as- phalts primarily by their high content of n-pentane insoluble material (asphaltene) and their high temperature of fusion, to °C (R & B). Among these are gilsonite, grahamite and manjak, all of which are in the pure state, with close to % carbon disulfide solubility and less than 5% jnineral content. Gilsonite, the native asphaltite most commonly used, is found in western Colorado and eastern Utah. It is black in color with a bright luster, a conchoidal fracture, and a penetration at 41°C of 3 to 8 with a softening point (R & B) of to °F ( to °C). Gilsonite has a car- bon content of 85 to 86%, is soluble in carbon disulfide to 98%, and has a specific gravity of to at 25°C (77°F). Grahamite is found in a single vertical fissure in a sandstone in West Virginia. It has a specific gravity of to at 77°F and a softening point (R & B) of to °F ( to °C), and a high tem- perature of fusion which distinguishes it from gilsonite. Other deposits in the United States, as well as in Mexico, Cuba and certain areas of South America, have yielded bitumens corresponding in general to the graha- mite in West Virginia, and are therefore referred to under this name.

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 - 24 - A third broad category is known as glance pitch or manjak, originally mined in Barbados, West Indies. The specific gravity at 77°F (25°C) is to , with a carbon content of 80 to 85%, a softening point (R s B) of to °F (to °C), a carbon disulfide soluble fraction of 95%, a black color and a bright to fairly bright luster with a conchoidal to hackly fracture. This asphaltite is considered an intermediate between graha- mite and gilsonite because of its specific gravity and fixed carbon (Broome, ; Hanson, ; Hoiberg ejt a^., ; Breger, ). C. Coal Tar Pitch 1. Source Coal can be described as a compact stratified mass of vegetation^ inter- spersed with smaller amounts of inorganic matter, which has been modified chemi- ically and physically by agents over time. These agents include the action of bacteria and fungi, oxidation, reduction, hydrolysis and condensation, and the effects of heat and pressure in the presence of water. The chemical properties of coal depend upon the amounts and ratios of different constituents present in the vegetation, as well as the nature and quantity of inorganic material and the changes which these constituents have undergone (Francis, ). Coal, therefore, has a rather complicated chemical structure based on carbon and hydrogen with varying amounts of oxygen, nitrogen and sulfur. Bi- tuminous coal, from which coal tar pitch is derived, contains a number of PAH, including carcinogenic benzo(a)pyrene (BaP) and benz(a)anthracene (Tye et al., ), and a variety of toxic trace elements such as antimony, arsenic, beryllium, cadmium, lead, nickel, chromium, cobalt, titanium, and vanadium (Zubovic, ). When coal is pyrolyzed, a variety of changes occur: above °C free water evaporates; above °C combined water and carbon dioxide are evolved; above °C bituminous coals soften and melt, decomposition begins, and tar

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 - 25 - and gas are evolved; at to °C most of the tar is evolved; at to °C decomposition continues and the residue turns solid; above °C the solid becomes coke and only gas is evolved; around °C no more gas is evolved and only coke remains; above °C small physical changes occur When coal undergoes carbonization, it passes through two steps of de- composition: onset of plasticity at to °C and advanced decomposition at to °C. Volatile products released at each stage undergo a series of secondary reactions as they pass through the coke before emerging from the retort. The volatiles are separated by fractional condensation or absorption into tar, ammoniacal liquor, benzole, and illuminating or heating gas (McNeil, a). The major reactions in the conversion of primary carbonization products into tars (McNeil, a) areJ 1) cracking of higher molecular weight paraffins to gaseous paraffins and olefins; 2) dehydrogenation of alkylcyclic derivatives to aromatic hydrocarbons and phenols; 3) dealkylation of aromatic, pyridine and phenol derivatives; 4) dehydroxylation of phenols; 5) synthesis of PAH by condensation of simpler structures; 6) disproportionation of PAH to both simpler and more complex structures. The temperature of carbonization and contact time with the hot coke bed and heated walls of the retort will determine the composition of tars, as well as the extent of the reactions. Tars from the different types of carbonization processes vary widely as to their composition and characteristics.

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 - 26 - The term low temperature carbonization refers to pyrolysis of coal to a final temperature of °C. The final solid product is a weak coke with high yields of tar and oil and low yield of gas. High temperature carboni- zation is pyrolysis of coal between °C and °C, with town gas as the product and coke as the by-product at the lower temperature and metallurgical coke as the product and gas as the by-product at the higher temperature CEncyclopaedia Britannica, ) . Coal tar pitch is the residue from the processing of coal tar (Figure ), Pitches or "refined tars" are obtained from the distillation of tars and rep- resent from 30 to 60% of the tar components (McNeil, a) (Table ). Distillate oils (described later) obtained by steam or vacuum distillation of pitch or pitch crystalloids or from coking of pitch are the only fractions from which pure chemical compounds are isolated. McNeil (a) has described the change in composition of tars found as the temperature increases from vacuum distillation or low temperature carboni- zation to high temperature carbonization: (a) The amounts of paraffins and naphthenes decrease and disappear, the naphthenes fading out before the paraffins. (b) The amount of phenolic material falls from about 30% to a small value. (c) The proportion of aromatic hydrocarbons increases from a low figure to over 90%. (d) The proportions of aromatic, phenolic and heterocyclic compounds containing alkyl side chains decrease markedly. (e) The proportion of condensed ring compounds containing more than three fused rings increases. (f) The yield of coal carbonized decreases from 10% to less than 5%.

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 CCM V 'Upper boiliiur point U3O"c I Includes alshamasislamicinstitute.com.pk, toluene, alshamasislamicinstitute.com.pk^lilna, a liv&tflts «hHirfrcenc. and creosote, Auctions. TfiflEDTIK ana toumattmc.. 5. IHC14 FIGURE ORIGIN OF COAL TAR PITCH i N)

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 - 28 - TABLE TYPICAL ANALYSES (PERCENT BY WEIGHT) OF TARS Coke Oven Tar Gas Works Tar Low Temperature Tar (°C) Pitch Creosote Light Oils Heavy Oils £ Source: Encyclopaedia Britannica,

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 - 29 - 2. Physical Properties Coal tar pitch is a black or brownish black shiny material ranging from a viscous liquid at ordinary temperatures (30 to 80°C) to a material which be- haves as a brittle solid exhibiting a characteristic conchoidal fracture (McNeil, a; Lauer, ). At higher temperatures the brittle solid pitch can become a viscous liquid. It has a characteristic "tarry" odor described as a combination of smells of naphthalene and phenol modified by small amounts of pyridine and thiophenol. The residue from the primary distillation can have different viscosity grades depending on how extensively the coal tar is distilled. If the dis- tillation is continued to the desired softening point, the residue is called "straight run" pitch to distinguish it from "cut-back" or "flux-back" pitch, which is a straight run pitch of harder consistency cut back to the desired softening point with tar-distillate oil (McNeil, ). Since pitch is composed of a great number of different compounds, it does not show a distinct melting or crystallizing point. Therefore, pitch is usually characterized by the softening point, which can be determined by one of several standard methods: ring and ball, cube in air, cube in water and Kramer-Sarnow (McNeil, b). Each of these methods represents the tempera- ture at which a given viscosity or softness is attained under specific con- ditions . The softer grades of pitch having softening points (R &. B) below 50°C are usually referred to as base tars or refined tars; other grades are soft pitch (50 to 75°C), medium-hard pitch (85 to 95°C), and hard pitch (above 95°C) (McNeil, S). - _

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 - 30 - In general, all pitches behave essentially as Newtonian liquids over the range of viscosities which can be measured reliably. The only departure from Newtonian flow in pitches is a slight reduction in viscosity with in- creasing shearing stress found in samples with a high content of toluene in- soluble materials. 3. Chemical Properties It has been difficult to isolate and characterize compounds from this complex bituminous material. It has been estimated that pitch contains five to ten thousand compounds, of which to have been isolated and identi- fied (McNeil, b). Among those identified have been a large number of PAH. Varying amounts of PAH are formed by secondary reactions occurring during carbonization of coal. Coal tar pitch is composed predominantly of carbon (86 to 93%) and hy- drogen (5 to 7%), with small amounts of nitrogen ( to %), oxygen, and sulfur. Nitrogen is usually present in either five- or six - membered rings or as nitrile substituent. Oxygen is present as phenolic and quinone sub- stituents, as well as in four-, five-, or six- membered rings. Sulfur is usually found in five-membered rings (McNeil, ). Analysis for certain metals in coal tar has revealed high concentrations of zinc (over yg/g) and lead (70 to 75 yg/g); concentrations of between 1 and 10 yg/g of iron, cadmium, nickel, chromium, and copper have been found (White, ). Mag- nesium, boron and vanadium have also been identified in coal tar pitch (Liggett, ). Because of the importance of pitch in various industries, a number of studies have been carried out to elucidate its structure. Most specifications for coal tar pitches include limitations of solubility in certain solvents. Different solvents are required for various specifications and the methods used vary among investigators. These differences have made it difficult to compare

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 - 31 - results (McNeil, b). Table indicates several methods which may be roughly equated. The Demann () and Broche and Nedelmann () methods divide the pitch into material insoluble in benzene (a-component), material soluble in benzene but insoluble in petroleum ether (0-component) and material soluble in petroleum ether (5-component). Adam et_ a!U () extend the above methods by separating the benzene extract into soluble and insoluble portions, by add- ing the concentrated benzene extract to 10 times its volume of petroleum ether, and by separating the a-component into pyridine soluble (€2) and pyridine in- soluble (C^) fractions. The petroleum ether soluble portion is referred to as "crystalloids" and the petroleum ether insoluble but benzene soluble por- tion is called "resinoids." Crystalloids are also defined as being soluble in hexane or similar aliphatic solvents. Dickinson () modifies the Adam, method by performing a vacuum dis- tillation on the pitch to obtain distillate oils, extracting the residue with benzene and pyridine, precipitating the benzene extract with petroleum ether and extracting the precipitate with n-hexane. Resin A is that part of the pitch soluble in n-hexane or petroleum ether; Resin B is that part of the pitch insoluble in hexane but soluble in benzene and in fractions C^ and C2- A solvent analysis method (Mallison, ) which has been widely used in Europe divides the pitch into five fractions: H-resins, M-resins, N-resins, m-oil^ and n-oils. The method is not a solvent fractionation and the fractions are not further analyzed (McNeil, b). A number of other solvent analysis or fractionation methods that have been used are toluene and tetralin solvents; carbon disulfide, pyridine, benzene, petroleum ether and diethyl ether; pyridine, xylene and decalin; and nitrobenzene and acetone.

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 - 32 - TABLE TERMINOLOGY APPLYING TO ANALOGOUS FRACTIONS AS DETERMINED BY FOUR FRACTIONATION PROCEDURES Adam et al . () ~ Cl C2 Resinoids Crystalloids Dickinson () Cl C2 Resin B + some Resin A Distillate oils + some Resin A Demann () a-Fraction B-Fraction 6 -Fraction Mallison () H-Resins M-Resins N-Resins m-Oils and n-oils Source: McNeil, 19GGL TABLE MOLECULAR WEIGHT AND HYDROGEN TO CARBON RATIO OF MEDIUM-SOFT COKE OVEN PITCH Fraction Wt. range % Reported Av. atomic Solubility mol. wt. H/C ratio Crystalloid Resinoid C2 G! Sol. petroleum ether insol. petroleum ether, soluble benzene insol. benzene to insol. pyridine, quinoline Source: McNeil, b

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 - 33 - To indicate the variability in these separations, the H-resin content is between and % while M-resin content is to % in vertical retort tars. The variations in pitches from coke ovens are H-resins to % and M-resin to %. The same kind of variability holds true for crystalloids (45 to 60%), resinoids (16 to 24%), C2 (5 to 15%) and C^ (3 to 28%) in coke oven pitch. Tars from vertical retorts contain 55 to 70% in crystalloids and less C± and resinoids while low temperature pitch contains less than 1% C± and 7u to 80% crystalloids (McNeil, b). The molecular weight and hydrogen to carbon ratio of crystalloids, re- sinoids, GI and C2 are represented in Table The overall range in mole- cular weight for coal tar is between and The C^ fraction has a much lower H/C ratio. Low temperature processes are found to have higher H/C ratios. A value of has been reported for the crystalloid fraction from continuous vertical retort pitch (Greenhow and Smith, ). The distillate oil fraction has been subjected to many analyses and is the only fraction of pitch from which pure chemical compounds can be isolated by techniques normally used, such as fractionation and chromatographic separation methods. McNeil (b) has listed compounds all boiling above °C (an arbitrary cut off value), most of which are condensed PAH and their hetero- cyclic analogs, from pitch or refined tar which is sufficiently volatile to distill without decomposition. A partial list is shown in Table PAH found in refined coal tar and in high temperature conversion process coal tar are listed in Tables and , respectively. The pitch crystalloids contain the same major components as the dis- tillate oils. They are composed of polynuclear aromatics with an average of 3 to 6 rings and with a molecular weight in the range of to Com- pounds similar to those indicated in Table are: acenaphthene, fluorene,

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 - 34 - TABLE

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 - 35 - TABLE PAH IN COAL TAR PNA Anthracene Benz [a] anthracene Benzo[b] chrysene Benzo [ j ] f luoranthene Benzo [k] f luoranthene Benzo [g , h, i] perylene Benzo [ a ] pyrene Benzo [e]pyrene Carbazole Chrysene Dibenz[a,h] anthracene Fluoranthene Perylene Phenanthrene Pyrene Concentration (g/kg) in coal tar* (1) (2) *Two samples of medicinal coal tar Source: Lijinsky et al_.,

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 - 36 - TABLE MAJOR COMPONENTS OF GERMAN HIGH-TEMPERATURE CONVERSION PROCESS COAL TAR Average Component weight percent Naphthalene Phenanthrene Fluoranthene Pyrene Acenaphthylene Fluorene Chrysene Anthracene Carbazole 2-Methylnaphthalene Diphenyleneoxide Indene Acridine 1-Methylnaphthalene Phenol m-Cresol Benzene Diphenyl Acenaphthene 2-Phenylnaphthalene Toluene Quinoline Diphenylenesulfide Thionaphthene m-Xylene o-Cresol p-Cresol Isoquinoline Quinaldine Phenanthridine 7,8-Benzoquinoline 2,3-Benzodiphenyleneoxide Indole 3,5-Dimethylphenol 2,4-Dimethylphenol Pyridine a-Picoline B-Picoline y-Picoline 2,6-Lutidine 2,4-Lutidine Source: Shults,

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 - 37 - phenanthrene, anthracene, pyrene, anthraquinone and chrysene(Hoiberg, a). The more complex part of coal tar pitch (30%), represented by C^, C2 and resinoid fractions, appears to be a continuation of a series formed from less complex, more soluble and more volatile fractions (Table ), and con- sists mostly of ring systems not highly condensed, with the majority of the rings fused to not more than three other rings (McNeil, b). Osmotic pressure measurements have given estimates of to for the molecular weight of resinoids. The oxygen, nitrogen and sulfur content is reported to be 1 to , to , and to atoms per hundred atoms/ respectively, indicating that this fraction is largely hydrocarbons (McNeil, a). The C2 fraction is different from the resinoid fraction and is considered to be a complex mixture of polynuclear compounds with 5 to 20 fused rings. Carbon in the ring is the most abundant element but oxygen, nitrogen and sulfur are also present in lesser amounts. There is a fair amount of substitution, primarily methyl and hydroxy groups, the degree of methylation increases with molecular weight, and the ring structure is not highly condensed. The Cj fraction, pyridine insoluble material, is a black infusible powder partly soluble in quinoline, appearing to have a molecular weight range of to This C± fraction is highly variable and depends on the type of coal and the means of production. It is thought to consist of dis- persed particles that vary from one to two micrometers in diameter. The particles absorb variable amounts of high molecular weight tar resins. Therefore quino- line extracts more of the resins from the dispersed material than does pyri- dine (McNeil, a; Koiberg, a).

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 - 38 - TABLE PREDOMINANT STRUCTURES IN COKE OVEN TAR Boiling Average range percent Major components (°C) of tar Single 6-membered rings Benzene Toluene Xylenes 3 Fused 6,5-ring systems Indene Hydrindene Coumarone 12 Fused 6,6-ring systems Naphthalene Methyl naphthalenes 8 Fused 6,6,5-ring systems Acenaphthene Fluorene Diphenylene Oxide Source: McNeil, a

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 - 39 - The preliminary separations described in this section are necessary precursors to chromatographic techniques, such as gel, gas-liquid, thin layer, gravity fed column, and high performance liquid. The chromatographic methods, in conjuction with other analytical tools used to characterize and identify the compounds in pitch, will be described in detail in Chapter IV.

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 - 40 - II - ENVIRONMENTAL EXPOSURE FACTORS: ASPHALT A. Production and Consumption 1. Quantity produced Asphalt sales in the United States have increased from an estimated ten million tons in to somewhat over 34 million tons in (Asphalt Insti- tute, b). Asphalt, which constitutes 9 to 75 weight-percent of crude petroleum, represented percent of United States crude oil refinery yield in , only a slight increase since (Table II-l) (Nelson, ). Currently, paving represents seventy-eight percent of the asphalt market, roofing seventeen percent, and miscellaneous uses five percent (Figure II-l) (U.S. Bureau of Mines, ). The consumption of cutback and emulsified asphalts has changed little since , but the use of asphalt cements, which accounts for eighty percent of asphalt consumed, has increased steadily to over 22 million tons (U.S. Bureau of Mines, ). Exports of asphalt were 61 thousand tons in , 62 thousand tons in , 75 thousand tons in , and 58 thousand tons in Imports of asphalt, including native asphalts, amounted to million tons in , 2 million tons in , and less than 1 million tons in (U.S. Bureau of Mines, ). 2. Market trends Between and , annual U.S. asphalt production increased from 20 thousand tons to 3 million tons (Asphalt Institute, b). Annual production is * expected to increase from the current level of 30 million tons to over 40 million tons by (Predicasts, ). Under circumstances of diminished oil supplies, asphalt will be too valuable to use as a paving binder1, and will probably be replaced by Portland -'•Personal communication, Walter Hubis, Gulf Mineral Resources, Denver, Colorado.

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 - 41 - TASLE II-l UNITED STATES ASPHALT PRODUCTION AS PERCENT OF PETROLEUM REFINERY YIELD YEAR % ASPHALT 3,3 * * * * *Estimate Source: Nelson,

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 - 42 - FIGURE II-l. ANNUAL DOMESTIC SALES OF ASPHALT BY MAJOR MARKETS 28 26 24 22 C/) £18 lie 12 10 8' 64 0 • PAVING A ROOFING • MISCELLANEOUS / A • i i i i I i i i i I i i i i YEARS Source: U. S. Bureau of Mines,

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 - 43 - cement-concrete, its only current competitor. The roofing market will con- tinue to receive its share of asphalt because no competitive substitute is available (Gerstle, ). With approximately six billion tons of asphalt covering roads, runways and parking lots of the United States, there may be a trend toward recycling aged asphalt. According to methods specified by Mendenhall ()t asphalt- aggregate mixtures can be reheated and rejuvenated without impairing the penetration characteristics or weakening the material. 3. Market prices In , the price of asphalt was nineteen dollars per ton. Until the early 's, the price per ton fluctuated between seventeen and twenty-one dollars. Between and , the price increased to twenty-eight dollars per ton and is expected to continue increasing (Krchma and Gagle, ). 4. Producers and distributors On January 1, , there were crude oil refineries in the United States with a combined distillation capacity of million barrels per day. Of these, refineries produced asphalt (U.S. Bureau of Mines, ). Economic considerations dicatate whether a petroleum residue will be processed as an asphalt product, heavy fuel oil or petroleum coke, or burned as fuel (Lewis, ). The period of greatest asphalt consumption occurs from July through October, with August as the month of greatest usage. Because production usually cannot meet demand during the peak season, asphalt is often stock- piled at the refinery or at bulk terminals which have been established to facilitate distribution to sites of paving and roofing material manufacture (Lewis, ). Asphalt is shipped from the refinery or bulk terminal by truck, barge or rail car. ' -

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 - 44 - 5. Production methods Ninety-eight percent of asphalt used in the United States is derived from crude oil (Miles, ) , although not all crudes are good, or even adequate, sources of asphalt. In general, if a crude contains a residue (fraction boiling above °C (°F)) that has an API gravity below 35 and a Watson characterization factor of less than (alshamasislamicinstitute.com.pk naphthenic than paraffinic), it may be adequate for asphalt manufacture (Gary and Handwerk, ). The following information concerning processes for the recovery and refining of asphaltic residues is based on discussions by Jones (), Gary and Handwerk (), Corbett (), Ball (), Broome (), Sterba (), Thornton (), Oglesby () and the Asphalt Institute (, b). The United States petroleum industry makes 2, products, of which are asphalts (Table II-2) (Mantell, ). Asphalts from different crude oil stocks may vary inherently in properties such as temperature susceptibility (the amount of change is viscosity with change in temperature). Properties such as durability may also be altered appreciably by processing treatment and addition of fluxing oils or blending stocks. In the refining of petroleum, crude oil is first distilled at atmospheric pressure at temperatures up to ° to °C (° to °F) in order to separate it into intermediate fractions of specific boiling ranges. After lower boiling fractions such as gasoline, kerosine, and diesel oil are removed, the remaining "reduced" crude, or straight-run residue, is further distilled under vacuum to separate gas oil and lubricating oil sidestreams. The residue withdrawn from the vacuum tower may become propane deasphalting stock or be mixed with additional atmospheric residue for further distillation under vacuum. Sidestreams from this third distillation may be used as catalytic cracking feedstocks, while the

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 - 45 - TABLE II PRODUCTS MANUFACTURED BY U.S. PETROLEUM INDUSTRY Class Number Asphalts Carbon blacks 5 Chemicals, solvents, misc. Cokes 4 Distillates (diesel fuels & light fuel oils) 27 Fuel gas 1 Gasolines 40 Gas turbine fuels 5 Greases Kerosines 10 Liquefied gases 13 Lubricating oils 1, Residual fuel oils 16 Rust preventives 65 Transformer and cable oils 12 Waxes White oils Source: Mantell,

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 - 46 - asphaltic residue is removed from the tower bottom. Steam may be used during any of these distillation steps in order to improve vaporization and minimize coke formation in the apparatus. Propane deasphalting is a process for removing resins or asphaltic components from a viscous hydrocarbon fraction in order to recover lube or catalytic cracking stocks. The charge for solvent deasphalting is derived from atmospheric or vacuum distillation bottoms that are low in asphalt content. The process consists of a countercurrent liquid-liquid extraction under temperatures and pressures determined by the nature of the charge stock. The deasphalted oil solution is withdrawn from the tower top and the propane solvent is stripped and recycled. Asphalt may be subjected to some form of thermal cracking which breaks heavy oil fractions into lighter, less viscous fractions by applying heat and pressure in the absence of a catalyst. Coking, or delayed coking, is a severe form of cracking, at temperatures exceeding °C (°F), which con- verts a heavy residue into a weak coke suitable for use in the manufacture of carbon electrodes but not in metallurgical blast furnaces. Visbreaking, at temperatures ranging from ° to °C (° to °F), is a relatively mild treatment that results in little boiling point reduction but greatly lowered viscosity. Neither coking nor visbreaking yields asphaltic residues as does "thermal cracking," a process now supplanted by catalytic cracking for the production of gasoline (Corbett, ). Thermal asphalts result from a cracking process in which a heavy oil stock is heated to ° to °C (° to °F), then discharged into a reaction vessel under pressures up to psig. The cracked products are distilled, leaving an asphaltic resi- due '(Figure }.

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 1 alshamasislamicinstitute.com.pk-< 2 3 OLA. MK toa -M^ U9UIDASIHAUS Cbp iS5*- (MC) > CMLJLSlFft) MHIflTS FIGURE II REFINERY STEPS IN THE PRODUCTION OF ASPHALT

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 - 48 - Straight-run asphalts may be "air-blown" in order to produce specification products with reduced volatile content and increased melting point (relative to the straight-run stock). The stock is preheated to Vto °C (°to °F) and air is forced through the hot flux at rates ranging from 15 to 50 cubic feet per minute per ton of asphalt charge. Air blowing is occasionally done in the presence of phosphorus pentoxide, ferric chloride or zinc chloride in order to shorten blowing time. The addition of the essentially non-recoverable "catalyst" in concentrations from to 3 percent results in a product with higher penetration for a given softening point. High ductility and improved temperature susceptibility are other advantages which lead to the use of "catalytic asphalts" in a variety of specialty base stocks. Asphalt cements make up eighty percent of the current asphalt market (U.S. Bureau of Mines, ). These are penetration grade asphalts derived from re- sidua of either vacuum distillation or propane deasphalting. They'may be air blown and may represent a mixture of base stocks. Asphalt cements, cut back with a petroleum solvent, axe either rapid-curing or medium-curing asphalts. Road oils (slow-curing) are the least uniform of the liquid asphalts and may in fact be directly distilled rather than cutback. Asphalt emulsions are normally produced from penetration asphalt cements. Depending on their intended use, asphalts may be liquefied in various ways (Oglesby, ; Day and Herbert, ; Mertens and Borgfeldt, ). Blending of cutback asphalts and emul- sified asphalts is not necessarily a refinery process (Figure II-2). Diluting an asphalt cement with a lighter petroleum distillate yields a product with lower viscosity. Upon evaporation of the solvent, the cured asphalt has approximately the same penetration grade as its parent asphalt ce- ment. The base stock may be directly blended or stored in tanks which range

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 - 49 - in size from 25, to , barrels. The stock is delivered to a blend tank and mixed with a measured volume of diluent- Rapid-curing cutbacks (RC) contain a diluent (gasoline or naphtha type) with a boiling range of ° to °C (° to °F). The base asphalt will vary from 70 to penetration in order to leave a cured asphalt of penetration. The least viscous grade (RC) can be poured at room tempera- ture. Middle-curing cutbacks (MC) use a kerosine type diluent with a boiling range of ° to °C (° to °F). This cutback is more versatile than the others, with good wetting properties on fine aggregates and a moder- ate evaporation rate. The base asphalt will vary from 70 to penetration to leave a cured residue of to penetration. MC and MC can be poured at room temperature. MC can contain as much as 40 percent by volume diluent. The most viscous grade, MC, may have as little as 18 percent solvent and usually must be warmed before use. Slow-curing asphalts (SC), often referred to as "road oils," may be refined directly to grade rather than consisting of an asphalt cement plus diluent. They are the least uniform in composition. Heavy diesel fuel, overhead gas oils or cycle stocks from other processes may be used as solvents. The lightest grade (SC) has the consistency of light syrup. The heaviest grade (SC) will scarcely deform at room temperature, and is slightly less viscous than the softest asphalt cement ( to penetration). Aqueous emulsions in which the asphalt content is 55 to" 70 percent by weight are another form of liquefied asphalt. The three emulsion grades - rapid-setting, medium-setting, and slow-setting - can be applied at normal temperatures. The asphalt cures by evaporation of the water rather than of a petroleum solvent, thus avoiding hydrocarbon emissions. Emulsions can be

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 - 50 - applied on wet aggregates and generally are ready to resist traffic damage sooner than cutbacks. The equipment needed for mixing and application is simpler and less expensive than that required for other asphalt products. Before , anionic emulsions vrere the only type commercially available. Saponified fatty and resinous acids or saponified tallow derivatives were the emulsifying agents used with an asphalt cement of to penetration. Cationic emulsions, using a quaternary ammonium compound as an emulsifying agent^ are now available and can be used with a wide variety of mineral ag- gregates. They adhere well to wet aggregates, and can be used under condi- tions of high humidity or low air temperatures. B. Uses Asphalt is a readily adhesive, highly waterproof, durable thermoplastic material, resistant to the action of most acids, alkalis and salts. These properties are utilized in a wide variety of applications. 1. Major uses a. Paving CD Production and consumption The Standard Industrial Classification (SIC) category SIC includes establishments manufacturing asphalt (in some cases, coal tar) paving mixtures as well as blocks of asphalt, coal tar, or creosoted wood. Of these , had seventy-five percent specialization (defined as the ratio of all primary products to the total of primary plus secondary products). About 10, production workers are classified under SIC (U.S. Bureau of Census, ) (Table II-3). The top ten paving mix producers according to production figures are listed in Table II The value of all paving mixtures and blocks shipments classified under SIC was $ million in , $ million in and $ million in The amount of asphalt of less than penetration consumed in by

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 - 51 - TABLE II EMPLOYMENT SIZE OF ESTABLISHMENTS (SIC ) PAVING MATERIALS Total Establishments with an average of— 1 to 4 employees 5 to 9 10 to 19 20 to 49 50 to 99 to to to to 2, 34 13 2 1 1 Source: U. S. Bureau of Census, TABLE II THE TOP TEN PAVING MIX PRODUCERS: Producer and home state The General Crushed Stone Co., Pa. L.M. Pike & Sons, Inc., N.H. The Interstate Amiesite Corp., Pa. Asphalt Products Corp., S.C. Broce Construction Co., Okla. Associated Sand & Gravel Co., Inc., Wash. Ajax Paving Industries, Mich. Western Engineering Co., la. Dickerson, Inc., N.C. Highway Materials, Inc., Pa. Plant mix tonnage 1,, 1,, 1,, , , , , , , , Source: Roads and Streets,

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 - 52 - the paving industry was 4,, tons with a delivered cost of $ million. In , 5,, tons were consumed at a cost of $ million (U.S. Bureau of Census, ). (2) Materials Currently, ninety-four percent (over million miles) of the paved surfaces, in the United States are bituminous (Oglesby, ). These bituminous surfaces range from dirt surfaces lightly sprayed with liquid asphalt to high- grade asphalt cement pavements. A finished paving mix consists of about six percent asphalt cement and ninety-four percent mineral aggregates. In addition to asphalt cement, a variety of cutback and emulsified asphalts are used to treat or finish roads (See Section II.A for descriptions of asphalt cements, cutbacks and emulsions) Approximately million tons of mineral aggregates are consumed annually for all aspects of highway construction. Slag, broken stone, gravel and sand, the aggregates most commonly used, constitute 75% by volume of a finished paving mix. Because aggregates vary greatly in composition, strength, porosity and surface roughness, specifications and tests have been developed to insure cer- tain minimum standards (Oglesby, ). Experimental pavements using asphalt-rubber mixtures have been laid in many states. Rubber enhances the coefficient of friction, improves the stability of paving mixtures, and reduces temperature susceptibility and brittleness, as well as imparting greater elasticity and extending pavement life (Oglesby, ). Other experimental pavements have been laid using an epoxy resin and asphalt binder which is resitant to wear, heat and the solvent effects of fuel (Hoiberg, ) .

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 - 53 - (3) Process descriptions Hot mix plants General information in the following section was obtained from Oglesby (). Although road surfaces can be treated with either hot or cold applied asphalt, hot treatments are the most common. It is estimated that there are pav- ing plants of all sizes in the United States; plants with a capacity of tons per hour of finished mix are common near most large cities (Puzinauskas and Corbett, ). Asphalt is loaded at the refinery or bulk terminal at elevated temperatures into steam heated tank cars, trucks or drums and transported to the hot mix plant. The asphalt, stored in large heated underground tanks, can be pumped directly to the platform on which finished asphalt-aggregate mixtures are produced. The mineral aggregates are sent through the drier, a firebrick lined steel cylinder, to drive off moisture and heat to a mixing temperature of ° to °C (° to °F). The hot aggregates are segregated by size through shaking screens. In batch-mixing processes (the most common), aggregates and the asphalt binder are mixed by revolving blades in pug mills that can reach capacities of sixteen tons or more. The finished mix is deposited into waiting'trucks and taken to the job site. High capacity plants use a process whereby hot binder is introduced directly into the drier, thus insuring continuous output of finished product. Exposure of the binder to drier conditions does not seem to accelerate its aging, and the problem of dust from fine aggregates is substantially reduced.

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 - 54 - Cold mix plants Cold mix plants are similar to hot mix plants in operation, except that the aggregates are cooled before being coated with a naphtha liquefier. The coated aggregates are mixed with hot asphalt binder to form the finished pav- ing product. Such cold mix products are not in common use. Paving In the past, all placing and leveling of hot asphalt was performed manually. Self-propelled finishing machines have largely supplanted manual operations, although small jobs, especially patching operations in cities, still rely on hand equipment. The hot aggregate-asphalt mixture, which is transported to the job site in dump trucks, is unloaded, spread and tamped, usually with one machine. Final tamping is done by large, smooth-wheeled rollers. Road mix processing, still used on side roads, is performed with a single machine that picks up aggregates, either freshly laid or pulverized from the old surface, mixes them with asphalt cement and spreads the new pavement. Surface treatment Road surfaces are treated with a pressurized distributor truck ( to gallon capacity) from which liquid asphalt is forced through a spray bar approximately twenty feet long. Several types of surface treatments may be used: 1) Dust palliatives: light slow-curing road oil or slow-setting emulsions applied at 79°C U75°F). 2) Prime (tack) coats: light medium-curing cutbacks or light road tar or slow-setting emulsions. 3) Armor coats on macadam or low quality concrete: varies with surface

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 - 55 - 4) Seal coats: Hand or crushed stone mixed with a slow-setting road oil applied to damp pavement. Slow-setting emulsions are sprayed on to rejuvenate surfaces. Proper temperatures of application, as well as ambient temperature, are fundamental to good asphalt performance. State highway departments specify minimum air temperatures for laying asphalt ranging from 0°C (32°F) to °C (60°F), the usual being °C (40°F). (Table II-5) . b. Roofing (1) Production and consumption In , there were plants in classification SIC ; which includes establishments that manufacture asphalt and coal tar saturated felts in roll or shingle form, as well as roofing cements and coatings (U.S. Office of Management and Budget, ). Of the total , had seventy-five percent or more specialization (U.S. Bureau of Census, ). (Specialization is defined as the ratio of all primary products to the total of primary plus secondary products). There were 11, production workers classified under SIC in (U.S. Bureau of Census, ) (Table II-