Energy & Fuels 2009, 23, 3343–3344
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Book ReViews Process Chemistry of Petroleum Macromolecules. By Irwin A. Wiehe. Boca Raton, FL. 2008. p 456. ISBN 1-5744-4787-4.
Whether you are a believer in “peak petroleum”, the end of oil, or a long-term future that includes a mix of sources for transportation fuels, you should expect the refineries of the world to process more heavy oils, bitumens, and unconventional feedstocks over the coming decades. This shift from light sweet petroleum to heavy sour feeds is already well underway in parts of North America, Asia, and Europe. The greatest challenge that faces these refineries is the more effective conversion of the large molecules in the vacuum residue fraction to clean transportation fuels. This grand challenge is the focus of Irwin Wiehe’s book Process Chemistry of Petroleum Macromolecules. As the intellectual father of current analysis of thermal processing of heavy petroleum fractions, Wiehe’s tour through the process chemistry of heavy petroleum is a deeply personal account, combining elements of personal memoire of applied science, tutorials on basic principles, restatement of classic papers, and review of current trends in science and technology. In stating his biases early on, Wiehe makes no apology for his emphasis on practical approaches to refinery problems. His preference for the use of coking as the default technology for conversion of vacuum residue is clear from the outset. The major emphasis throughout the book is clearly on his own contributions to the literature, with several chapters devoted to restating and expanding the contents of classic papers. The opening chapters of the book present a general synopsis of petroleum refining and marketing and then describe the composition of petroleum fractions. The controversy over the maximum molecular weight of petroleum molecules is presented well, with excellent discussion of the need for data on the asphaltene fraction to be reconciled with a range of process data, including distillation and molecular-weight measurements on non-associating fractions. While the validity of extrapolating data from vapor-pressure osmometry to infinite dilution is open to debate, Wiehe points out that any of the alternatives have likely biases when applied to such complex heterogeneous mixtures of components. In presenting the chemistry of petroleum, Wiehe clearly prefers broad definitions of classes of compounds in petroleum and their reactions; therefore, readers will need to look elsewhere for more definition of molecular species and reaction pathways. The segment on chemical composition and structure ends with a restatement of Wiehe’s 1994 paper on the pendant-core model of large molecules in petroleum. The two longest chapters of the book deal with the kinetics of thermal cracking and coking and the phase behavior of asphaltenes. Encompassing almost half the length of the book, these chapters are its heart and soul. The order of these chapters is chronological, in that the role of phase behavior in kinetic modeling of thermal cracking precedes the in depth discussion of phase behavior. Given that kinetic modeling of coking was one of Wiehe’s greatest contributions, the chapter on thermal cracking is a detailed description of the kinetics of cracking and coke formation with considerable expansion of the material published previously. This chapter combines Wiehe’s 1994 paper on the phase separation kinetic model with his work with
Gould on hydrogen donors and his later conference papers. One nod to other significant contributions to the field is a brief summary of an outstanding paper by Olmstead and Freund on kinetics based on thermogravimetric analysis (TGA). Given the difficulty in obtaining this reference, a more extensive presentation of the TGA approach would have been most welcome. Wiehe’s emphasis on his own work is a strength in this chapter, giving a clarity of presentation that is invaluable to newcomers to the field. The one weakness in this section is the discussion of the assumption of phase separation during coke formation. While the observation of mesophase droplets in the quinolineinsoluble fraction of coked product is proof of a liquid-liquid phase separation, it is not necessarily the main phase separation of cracked asphaltene material that is so central to his model. Over the past decade several studies have demonstrated multiphase behavior in heavy petroleum fractions, and this literature would have bolstered Wiehe’s excellent model by providing a stronger theoretical basis. The chapter on phase behavior begins with extensive results on solubility measurements that are interpreted in terms of solubility parameters and then ends with the theoretical basis for solubility parameter relationships. Wiehe’s emphasis is on the method of analyzing and predicting compatibility rather than the theory. The wisdom of this approach is for practical applications to blending of streams, where the emphasis is on preventing any insolubility. His “oil compatibility model” is an effective method for analyzing and predicting compatible blends and operating conditions in processing petroleum fractions rather than a full model of phase behavior. Wiehe’s approach is to combine microscopic examination of samples with blending criteria based on rescaled Hildebrand solubility parameters of the oil and the flocculation point of the asphaltenes. He argues that this method is effective and conservative for determining the limits of compatibility of petroleum streams based on practical application in refineries. Those interested in models of phase behavior that predict both the onset of precipitation and the amount of precipitate will need to seek other sources. Throughout the book, Wiehe makes excellent arguments for the use of optical microscopy to observe materials suspended in residue samples and to understand solubility behavior. The issue of whether the phases observed at room temperature under the microscope are the same as at process conditions is not examined. His implicit argument is that room-temperature observations give conservative estimates of solubility in petroleum mixtures, although he mentions one contrary example in the section on de-asphalting because of critical behavior of solvent components. The book would be enhanced by addressed this gap in understanding phase behavior at refinery process conditions and identifying it as one if the key challenges for ongoing research. After the major section on phase behavior, the book includes chapters on fouling, separation of residue fractions to maximize yields, and short descriptions of the major process technologies for residue conversion. The practical advice on analysis and mitigation of fouling is invaluable and by itself worth the price of purchase. The chapter on coking contains excellent insights
10.1021/ef900392c CCC: $40.75 2009 American Chemical Society Published on Web 05/18/2009
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Energy & Fuels, Vol. 23, 2009
for anyone interested in the development of new coking processes. The one gap in the sections on coking is a discussion of several of the new processes under development during the past decade. Given the emphasis of Wiehe’s own research work and his philosophy for processing of vacuum residue fractions by thermal cracking to eliminate large aromatic groups, readers should not be surprised to find limited discussion of catalysis in this book. The discussion of the interaction of petroleum macromolecules with surfaces and interfaces is covered only briefly, and the process chemistry of supported-metal catalysts and deactivation is not mentioned at all. Consonant with the emphasis on coking technologies, the phase behavior of the macromolecules in high-pressure hydrogenation is not explored. With an emphasis on practical analysis of conversion kinetics, compatibility of refinery streams, and analysis of fouling, this book will be invaluable for engineers engaged in operation of refining units or upgraders that process vacuum residues. For anyone new to the field of conversion of vacuum residue, the tutorial aspects of the extended sections on kinetics and
Book ReViews
solubility make this text an excellent starting point, with a more accessible format and presentation than the original journal papers. Anyone engaged in research and development of technology for separation or thermal conversion of vacuum residue should read the chapters that deal with the tradeoffs in conversion of residue and Wiehe’s ideas for new directions in coking technology. Although the emphasis throughout is on petroleum materials, many aspects of processing coal and biomass liquids are closely related; therefore, the book should find a wider audience among readers who are interested in phase behavior and fouling in any thermal-processing operation. As a scientific memoire and summary of an eminent career, this volume presents numerous insights for future development of both process technology and the science of petroleum macromolecules. Murray R. Gray, UniVersity of Alberta EF900392C 10.1021/ef900392c
