Fossil Hydrocarbons: Chemistry and Technology by Norbert Berkowitz • ISBN: 012091090X • Publisher: Elsevier Science & Technology Books • Pub. Date: January 1997 PREFACE The decade of 1973-1983, in which most of the Western world moved from economic turmoil and panic created by an oil crisis to blissfully "putting it all behind us", illustrates how easily we persuade ourselves to forget what should have taught us a profound lesson~and how cavalierly we face the need to secure long-term supplies of liquid fuels. The oil crisis abated not because of how we responded to it, but because the major Middle East oil producers raised output in expectation of recouping revenues that had fallen victim to the Iraq-Iran war. This generated an oil glut that halved crude oil prices and allowed us to return to the status quo ante. Laissez-faire economic policies once again allowed profligate use and/or export of diminishing indigenous reserves of gas and conventional oil. Alterna- tive sources~the heavy fossil hydrocarbons that could help us to attain reason- able energy self-sufficiency~were once again consigned to the dim recesses of our collective minds. Research and development, which outlined and some- times defined the new technologies through which self-sufficiency could be achieved, was abruptly discontinued. And development of future crude oil supplies once again became centered on distant sources over which we have little, if any, control. All this occurred, despite the demonstration by major commercial ventures (in particular, South Africa's coal-based SASOL complexes and production of "synthetic" light crudes from Alberta's oil sands) of what is technically possible and could be competitively accomplished. It is difficult to understand a mindset that allows such energy "policies"~ and, not coincidentally, reflects a deplorable disregard for macroeconomics on which all national well-being ultimately depends~as anything other than an attitude of apres mois la deluge. Even academia is not immune to that malaise. Instruction in petroleum engineering at universities and technical colleges is rarely augmented by the study of heavy fossil hydrocarbons, the existence of which is, as a rule, acknowl- xi xii Preface edged only when deemed to be relevant to instruction in rock mechanics, mining engineering, and mineral preparation. And between petroleum devotees who generally don't much care about these "other" resources and a dwindling band of professionals who do, we have thus promoted two solitudes each sustained by a technical jargon that suggests differences where few exist, and each side seemingly incapable of speaking to the other. In these circumstances, it seemed to me pertinent to draw attention to the fact that the entrenched dichotomy between petroleum hydrocarbons and coal, which in no small measure shaped popular attitudes about energy, is technically inadmissable and to observe that the heavy fossil hydrocarbonsmall much more abundant than natural gas and conventional crudes and distributed more equitably across the globemoffer attractive sources of synthetic gas and light oils even though the required conversion technologies are sometimes, as in the matter of coal liquefaction, still far from fully developed. The format of this book, which discusses the fossil hydrocarbons under common topic headings rather than by type, reflects my objectives. The first section (Chapters 1-7) thus opens with a review of indicators that support the underlying concept and then considers source materials, biosources, meta- morphic histories, host rock geology and geochemistry, classification, and molecular structure. Chapters 8-10 focus on preparation, processing, and conversion technologies. Finally, Chapter 11 examines some of the environ- mental issues that arise from production, processing, and use of fossil hydrocar- bons. Each topic is augmented by end-of-chapter notes that I deemed to be helpful, but did not want to insert into the main text (where they might have proved disruptive), and for each topic I have sought to provide a reasonably detailed bibliography for the interested reader to consult. To assist such refer- ence, I have, wherever possible, made use of English-language literature even though this might, at first glance, distort the scene and not give proper recogni- tion to the outstanding contributions made in many other countries and re- ported in other languages. Because I wanted to retain some historical flavor that traced the development of the relevant science and technologies as well as give credit where due, I have also, as far as possible, stayed with the original literature rather than cite more recent sources that added little to what had long been known. The use of the term fossil hydrocarbons in the title and throughout the text does, of course, take liberties with chemical nomenclature. But as petroleum hydrocarbons include bitumens and kerogens whose oxygen contents are no lower than those of some coals, I make no apology for such indiscretion. Nor do I apologize for overtly differentiating between preparation and processing, because the former is generally concerned with physically modifying the raw hydrocarbon and the latter changes it chemically. Preface xiii In preparing the text, I have drawn on open literature, on my lecture notes, and on what I have learned over the years from discussions with friends and colleagues. I must in this connection acknowledge my particular indebtedness to Dr. E. J. Wiggins, who served as Director of the Alberta Research Council and (later) as Board Member of AOSTRA (Alberta's Oil Sands Technology & Research Authority), as well as to colleagues at the University of AlbertamDr. A. E. Mather, Professor of Chemical Engineering; the late Dr. L. G. Hepler, Professor of Chemistry; Drs. R. G. Bentson and S. M. Farouq Ali, Professors of Petroleum Engineering; and Dr. J. M. Whiting, Professor of Mining Engi- neering. I must also thank the publisher, Academic Press, who encouraged me to undertake the writing of this book, and the Alberta Research Council's librarian, Ms. Nancy R. Aikman, who steered me to much helpful literature and thereby made my task so much easier. I would, however, be terribly remiss if I did not here also specifically express my deep gratitude to my wife for her unfailing love, support, and endurance during the many months I devoted to writing. To her I dedicate this volume. Table of Contents Preface 1 Introduction: The Family of Fossil Hydrocarbons 1 2 Origins 7 3 Host Rock Geochemistry 37 4 Classification 63 5 Composition and Chemical Properties 83 6 Physical Properties 121 7 The Molecular Structure of Heavy Hydrocarbons 155 8 Preparation 187 9 Processing 213 10 Conversion 253 11 Environmental Aspects 319 Index 343 CHAPTER 1 Introduction: The Family of Fossil Hydrocarbons Flawed classifications of living and inanimate matter are not uncommon and are usually of little concern except to the specialist. Sometimes, however, the flaws are "validated" by common usage and, in time, become counterproductive fallacies. So in the case of "petroleum": this term has come to be progressively expanded to "petroleum hydrocarbons," which include natural products as diverse as natural gas, light crudes, heavy oils, all bituminous substances, and oil-shale kerogens but which, be definition, exclude all types of coal and thereby create an untenable distinction. The venerable role that coal has played as a primary fuel since the late 12th century [111; as sources of metallurgical coke since the early 1700s; and in the mid-1700s as the trigger of an industrial revolution that changed the very course of human society all this may provide a historical perspective for sometimes setting it apart from the "petroleum hydrocarbons." But as the record also makes clear, there is little technically legitimated warrant for such dichotomy [2]. Taken for what it is popularly assumed to mean, "petroleum hydrocarbons" is a semantically questionable term even though it may be sanctioned by some dictionaries: for, although kerogens are indeed oil precursors, and bi- tuminous substances notably bitumen in oil sands2mmay represent mi- crobially and/or oxidatively altered oil residues [3], neither they nor other bituminous materials (such as tars and asphaltics) are oils, as "petroleum" implies and is commonly understood to mean [4]. However, more to the point here is the untenable implicit technical meaning of the term. Designating natural gas a variable mix of C1-C 6 alkanes as a petroleum hydrocarbon is certainly warranted by its composition, its common association with crude oil, and its descent from residual oily matter in late stages of kerogen catagene- sis. But adoption of bituminous substances and kerogens into the petroleum hydrocarbon family can only be justified if they are deemed to be, or to be chemically directly related to, oil precursors. And if so, one might ask why Numbers in square brackets refer to end-of-chapter notes. 2 Oil sands are also commonly referred to as bituminous sands or tar sands. 1 Introduction: The Family of Fossil Hydrocarbons hydrogen-rich boghead and cannel coals, which meet this criterion by closely resembling sapropelic kerogens in their origin, developmental history, and chemistry, are excluded from an otherwise all-embracing clan; and if, on reflection, they are admitted, why orphan the equally closely related and much more abundant, albeit less H-rich, humic coals? Differentiation between fossil hydrocarbons and choices among them are, of course, often necessitated by economic and/or supply constraints. But it is significant that where such need exists, choices almost always require resort to one or another of the heavy hydrocarbons, to bitumens, oil shales, or coals. In practice, differentiation is, in short, between these and what are properly termed "petroleum hydrocarbons"mi.e., natural gas and light crude oils; and where circumstances actually force resort to the "heavies," choices are always based on consideration of availability and costs [5]. Nor can it be otherwise, because fossil hydrocarbons stem from the same source materials~the entities that make up the basic fabric of living organ- isms~and consequently form a continuum of chemically related substances that extend from methane to anthracite. What differentiated the assemblages of source materials that over time developed into different hydrocarbon forms were primarily the relative proportions of the source materials; and these were determined by when and in what environments they accumulated [6]. In one form or another, organic carbon was continuously deposited from late Precambrian times, when primitive biota first appeared in ocean waters; and from early Devonian times, when terrestrial vegetation made its appearance, the locales in which organic carbon accumulated ranged therefore from alpine meadows, woodlands, and oxic swamps to disoxic lacustrine regions, paralic environments, and deep anoxic seas. Qualitatively, a hydrocarbon continuum is indicated by general connections between different hydrocarbon forms (Table 1.1). But more convincing chemi- cal linkages between them emerge when they are broadly arranged in order of increasing gravity, as in natural gasmlight oils heavy oilsmbituminous substances kerogensmsapropels~humic coals In such serial order, the continuum is mirrored in an uninterrupted, progres- sive fall of the H/C ratio from 4 in the case of methane, the principal component of natural gas, to 0.7, an average value for mature bituminous coals; and because that indicates increasing carbon aromaticity from progressive internal cyclization and dehydrogenation, it defines the nature of the transitions from gaseous to liquid, semisolid, and solid hydrocarbons. But the continuity of the fossil hydrocarbon series is also convincingly shown in other features. There is, for example, a remarkable similarity between constructs that pur- 1 Introduction: The Family of Fossil Hydrocarbons TABLE 1.1 Connections among "Petroleum Hydrocarbons" and Coals a Gaseous Bituminous fluid petroleum hydrocarbons viscous solid kerogens sapropels humic coals Waxy mineral waxes marsh gas (CH4) natural gas natural gas liquids crude oils asphalts bitumens tars cannel coals boghead coals lignites subbituminous coals bituminous coals anthracites a Adapted from R. R. F. Kinghorn, An Introduction to the Physics and Chemistry of Petroleum, Wiley & Sons, New York, 1983. port to depict average molecular structures of bituminous substances, kerogens, and coals and to show macromolecular, pseudo-crystallographic ordering in them [7]. There are pronounced behavioral similaritiesmfor instance, a close parallel between thermal degradation of kerogen (during catagenesis) and coal (during carbonization), with both yielding H-rich liquids (oils or tars) in amounts determined by their H/C ratios or hydrogen contents [8], and both leaving correspondingly H-depleted solid residues. And although the behavior of coal is profoundly influenced by its solidity and rank-dependent porosity, its responses to chemical processing to thermal cracking and hydrogenationmare much the same as those of other heavy fossil hydrocarbons. As might indeed be expected, these similarities make for interchangeability between bituminous substances, kerogen-rich oil shales and coal, and allow virtually identical processing techniques to transform any one of them into more useful, lighter members of the series. Regardless of whether the feed is a heavy oil, oil residuum, bitumen, oil shale, or coal, such transformation always entails some particular form of carbon rejection or H-additionmin one case increasing the H/C ratio by pyrolytically abstracting carbon as "coke," CO, and/or CO2, and in the other raising it by inserting externally sources H into the feed [9]. These procedures, summarized in Chapters 9 and 10, make it technically feasible to convert natural gas into an almost pure form of carbon [10] and, 1 Introduction: The Family of Fossil Hydrocarbons more important, to convert heavy oils, bituminous substances, oil shale kero- gens, or coals into light transportation fuels. They also allow transforming heavy hydrocarbons into a "substitute" or "synthetic" natural gas (SNG), or into a syngas from which an extraordinarily wide range of hydrocarbon liquids and industrial chemicals can be produced by Fischer-Tropsch techniques (see Chapter 10). The aromaticity of the feed will, as a rule, only determine the severity of processingmthat is, the extent of carbon rejection or H-addition, and in practice, this rarely means much more than selecting suitable processing regimes [ 11]. This given, questions of whether or when any of these options might be exercised can generally only be answered in light of prevailing economic circumstances. NOTES [1] Authentic documentary evidence places the first use of coal as a heating fuel in late 12th- century England, but there are indications that it was occasionally also used as such by the Roman legions in Britain during the 1st century. [2] Episodal uses of coal other than as primary fuel are a matter of record. In the mid-1800s, it began to be gasified and thereby converted into a domestic fuel gas. In the 1920s, it commenced service as a source of syngas needed for production of gasolines and diesel and aviation fuels. And by the early 1930s, it had established itself as a hydrogenation feedstock for manufacturing transportation fuels, heating oils, and high-purity carbon electrodes. These activities were mostly abandoned in the early 1950s, when abundant supplies of cheap oil and natural gas almost entirely displaced coal as anything other than a primary fuel and source of metallurgical coke, and sometimes displaced it even there. Since then, coal conversion has only attracted attention in perceived crises: in the 1960s and 1970s, coal gasification commanded wide but transient interest because projections, later proven wide of the mark, anticipated serious shortages of acceptably priced natural gas; and intensive work on trans- forming coal into liquid hydrocarbons lasted no longer than the crippling economic disloca- tions that followed the 1973 oil crisis, but were soon "remedied" by such events as the Iraq-Iran warna conflict that, by the convoluted economic policies of an international oil cartel (OPEC), caused an oversupply of oil and a consequent oil-price collapse that is likely to continue until well into the 21st century. That coal conversion can neverthelsss remain attractive is demonstrated by some 20 commercial plants in Europe and Asia that currently produce ammonia (for fertilizer use) from coal-based syngas. Parenthetically it is also worth observing that oft-repeated "technical" justifications for the dichotomy between "petroleum hydrocarbons" and coal are more contentious than real. Arguments that coal cannot meet the multifaceted needs of modern societies, or meet them as easily or conveniently as natural gas and/or petroleum, seem to ignore advances in coal processing since the mid-1940s. And the contention that coal is so much dirtier than oil and gas, and therefore environmentally "unfriendly," discounts what is required to prepare oil and gas for environmentally acceptable use, and ignores impressive advances in coal preparation (and combustion) over the past 40 or so years. [3] Although the relevant literature seems to regard all bitumens to be microbially oxidized and water-washed (see Chapter 3) and designates most heavy oils in like terms, the evidence Notes 5 for this view is not entirely satisfactory. There are, as suggested in Chapter 3, other possible mechanisms that could explain the their origins. [4] Oils are generated by thermal degradation of kerogen much as tars are thermally generated from coal, and bituminous substances are widely (but not necessarily correctly) assumed to have been microbially altered much as weathered coals were abiotically altered. In neither case can a reaction product be properly classified with its precursor. [5] That availability should often force the decision is due to a natural inequity the fact that the so-called advanced societies tend to be well endowed with heavy fossil hydrocarbons (mainly coal), but lack the abundant natural gas and crude oils that, for the most part, occur in less developed jurisdictions. [6] Particularly important in this context is that prior to Devonian times, ligninman important constituent of higher terrestrial plants that then made their first massive appearancem contributed very little to the precursor masses of fossil hydrocarbons. [7] As illustrated in Chapter 7, these constructs differ primarily in their carbon aromaticities, which increase steadily from the lighter to the heavier members of the series at the expense of aliphatic and, later, naphthenic moieties. [8] Because of the overriding importance of H for generation of hydrocarbon liquids (see Chapter 3), their yields and compositions depend on the concentration of lipids (or lipid-like matter) in the precursor; and this implies that oily matter increases and tends to become the lighter the farther its origin from an inland location. In other words, light oils originate in deep or moderately deep marine conditions, kerogens and sapropelic coals in paralic and/or lacustrine environments, and humic coals on land. [9] The many seemingly different (or differently named) processing methods turn out, on closer inspection, to be versions of basic techniques that differ in little more than operating minutiae; the rich vocabulary that characterizes petroleum preparation and processing (see Chapters 8 and 9) merely reflects the wide range of products that technical development and stimulated market demands allowed to be made from crude oil. By the same token, the much more limited process terminology relating to oil shale and coal mirrors the limited utilization of these resources. Oil shale, from which substantial quantities of (shale) oil were produced in the 19th century, is now little more than an occasional subject of a "hard look", and coal, long used as primary fuel and source of metallurgical coke, continues to be restrictively viewed as such. [10] This is, in fact, done in production of carbon blacks, which are used as pigments in printing inks, fillers for rubber tires, etc. Such carbons are characterized by small (10-1000 nm), nearly spherical particles and bulk densities as low as 0.06 g/cm 3. [11] For carbon rejection, the primary components of an "appropriate" regime are temperature, pressure, time, and, in some versions, catalysts. For hydrogenation, they are mainly tempera- ture, pressure, and a suitable catalyst. [...]... as precursor of dicyclic sesquiterpenes 2, and including sugars, starches, and celluloses, the last a dominant structural material of plants Sugars are aldehydes or ketones of polyhydric alcohols and form two groups, viz., monosaccharides (C6H1206) exemplified by glucose and fructose, and disaccharides (Ct2H22Oll) exemplified by sucrose and jS-maltose [5] By interaction of the aldehyde m C H O or ketonic... in continental wetlands and swamps is inundated by an advancing sea and covered by the silt it carries In both cases, catagenesis [18], the final phase in the evolution of a biomass into fossil hydrocarbons, progresses as a response to increasing overburden pressures and geothermal temperatures But the physical status and composition of organic matter at termination of diagenesis demands differentiation... 150~ and thereby produced a hydrocarbon mix of which 50% boiled in the gasoline/kerosine range, while the remainder consisted of distillate oils and residua Day and Erdman (1963) generated toluene, m-xylene, 2,6dimethylnaphthalene, ionene, and other aromatics by heating ]3-carotene in benzene at 120~ Heating a mix of oleic and stearic acids produced heptane and octane isomers, as well as some C7 and. .. Pteridospermeae (the forerunners of contemporary conifers and cycads) and later, from flowering and fruit plants (Angiospermae) The dominant components of these biomasses were therefore derived from celluloses and lignins rather than from lipids, and alteration by abiotic 02 and terrestrial biota was reflected in a marked preference for generating C27, C29, and C31 n-alkanes as well as small amounts of even-numbered... structure element of lignin ation by marine organisms in preference for generating C15 , C17 , and C19 n-alkanes In paralic environments that is, on suboxic continental shelves and in offshore, deltaic, and lacustrine waters in which biomasses were also shielded against oxidative attack and could putrefymalgal matter, supplemented by less lipid-rich seeds, pollen, and fungal spores from terrestrial... rocks and carbonaceous shales, as well as in oil shales, and represents a quantity of organic carbon that exceeds by two orders of magnitude the total of all known coal, oil, and gas resources However, kerogen compositions are as diverse as the biota and formative environments that produced them, and it is therefore proper to speak of kerogen in the plural A nomenclature that reflects this diversity and. .. in peat swamps and composed of small fibers and/ or fibrous matter with clearly expressed woody structures 5 Coaly kerogen~consisting of variously reworked organic material and naturally charred, oxidized, and/ or fungally degraded vegetal matter Such distinctions are important, because yields and composition of oil and/ or gas that kerogens furnish on heating depend on their H/C ratios, and therefore... amorphous, and herbaceous kerogens, collectively referred to as "sapropelic" kerogens, thus tend to deliver relatively light oils [23], whereas woody and coaly kerogensmPotoni6's humic matter [20]m furnish tars and hydrocarbon gases These aspects, and relationships between kerogen and coal, are expressed in a kerogen classification (Table 2.5.1) that shows how H/C and O/C ratios change as kerogens mature, and. .. how organic matter is affected by such changes depends on its origin or, more specifically, on its H/C or Car/C ratio SAPROPELIC KEROGENS Kerogens formed from algal, amorphous, and/ or herbaceous source materials (and, as noted earlier, collectively termed sapropelic kerogens) are characterized by a preponderance of aliphatic carbon chains randomly connected by aromatic and/ or naphthenic moieties; in... C H 2 I HOOCH2 and the fatty acidsmwhich can exist in saturated forms exemplified by palmitic (C16H3202) and stearic (C18H3602) acids or unsaturated versions such as oleic (C18H3402), linoleic (C18H3202), and linolenic (C18H3002) acids then losing mCOOH and yielding straight-chain alkanes [1] However, waxes, terpenes, and steroids belonging to the group are structurally more complex and undergo correspondingly . in paralic and/ or lacustrine environments, and humic coals on land. [9] The many seemingly different (or differently named) processing methods turn out, on closer inspection, to be versions. first glance, distort the scene and not give proper recogni- tion to the outstanding contributions made in many other countries and re- ported in other languages. Because I wanted to retain some. Oil sands are also commonly referred to as bituminous sands or tar sands. 1 Introduction: The Family of Fossil Hydrocarbons hydrogen-rich boghead and cannel coals, which meet this criterion by