Petroleum Residua

Processes for hydrogen gasification, hydrogen pyrolysis, or coking of coal usually produce Hquid co-products. The Hygas process produces about 6% Hquids as benzene, toluene, and xylene. Substitution of petroleum residuum for the coal-derived process oil has been used in studies of coal Hquefaction and offers promise as a lower cost technology (104). 

Seacoke A process for making tar and coke by carbonizing mixtures of coal and petroleum residuum. The tar would be used in an oil refinery and the coke would be used for generating electricity. The process was sponsored by the U.S. Office of Coal Research 1964-1969 the work was carried out by EMC Corporation, Atlantic Richfield Company, and Blaw-Knox Company. Results from the pilot plant were encouraging but the project was abandoned because the benefits were judged insufficient to justify the complexity. 

These data taken together suggest that vanadium is deposited on the catalyst in three successive forms. The initial vanadium which appears on the catalyst is primarily an isolated V02+ species, presumably associated with alumina defect sites. This is followed by the diamagnetic vanadium surface phase and finally by the vanadium sulfides. This progression is illustrated by the analysis of catalyst samples taken from different positions in a reactor which had been employed in a pilot-plant treatment of a petroleum residuum (Figure 4). Note that all of... 

In coal-oil coprocessing, coal is slurried in petroleum residuum rather than in recycle solvent, and both the coal and petroleum components are converted to high-quality fuels in the slurry reactor. This variation offers the potential for significant cost reduction by ehminating or... 

Both XANES and XPS results give the same relative ranking for the thiophenic content of any sample, recognizing the currently established accuracy of 10%. For example, either method confirms that petroleum residuum sample 1 contains the most thiophenic sulfur of those studied, and sample 3 the least. Both methods show that thiophenic sulfur concentrates in the asphaltenes prepared from residua 1 and 3, but not in the asphaltenes from residuum 2. However, the quantitative values are different. 

The use of model compounds eliminates many of the complicated and competing catalytic reactions encountered with petroleum residuum, enabling a clearer picture of the inherent reactions to be ascertained. 

The thermal effect upon 850°F+ coal extract conversion is less than would have been expected from petroleum residuum considerations. A substantial portion of the 850°F+ conversion of coal extracts is catalytic in nature. 

The classic definition of asphaltenes is based on the solution properties of petroleum residuum in various solvents. This generalized concept has been extended to fractions derived from other carbonaceous sources, such as coal and oil shale. With this extension there has been much effort to define asphaltenes in terms of chemical structure and elemental analysis as well as by the carbonaceous source. This effort is summarized by Speight and Moschope-dis (i) in their chapter in this volume along with a good summary of the current thinking. Thus, there are petroleum asphaltenes, coal tar asphaltenes, shale oil asphaltenes, tar sands bitumen asphaltenes, and so on. In this chapter I will attempt to show how these materials are special cases of an overall concept based directly on the physical chemistry of solutions and that the idea that they have a specific chemical composition and molecular weight is incorrect even for different crude oil sources. 

Figure 1. Separation of asphaltenes from petroleum residuum...

While rayon and PAN are well-defined chemical compounds, pitch produced either from distillation of coal tar or as petroleum residuum is a complex mixture of hydrocarbon and heterocyclic molecules with molecular weights ranging from 200 to over 1000. Heating such a mixture above 400°C produces condensation and polymerization... 

This article first describes the ideal reactor types, namely batch, plug flow, and completely mixed reactors. Then, the petroleum reactors are discussed based on whether the reaction occurs in the vapor, liquid, or mixed vapor-liquid phase. More specifically, the naphtha-processing reactors are examined first, then gradually moving to heavier hydrocarbons, like kerosene and distillate, that react partially in the liquid and gas phases, and finally ending with a discussion on reactors processing heavy hydrocarbons like petroleum residuum, which reacts completely in the liquid phase. 

A detailed description of a chromia-on-alumina catalyst prepared by impregnation has been given elsewhere . Another supported nonmetallic catalyst widely used commercially is cobalt molybdate-on-alumina. The preparation of this catalyst using an alumina support with controlled pore-size distribution is as follows. Silica-stabilized alumina, with greater than 50% of its surface area in 3-8 nm pores and at least 3% of the total pore volume in pores greater than 200 nm in diameter, is impregnated with an aqueous solution of cobalt and molybdenum. The finished oxysulfide catalyst was tested for hydrodesulfurization of petroleum residuum at 370°C and 100 atm for 28 days and compared with a convential cobalt-molybdate catalyst having a major portion of the surface area in 3-7 nm pores. The latter catalyst and controlled pore catalyst maintained 57 and 80% activity, respectively. 

The classic definition of asphaltenes is based on the solution properties of petroleum residuum in various solvents. Broadly speaking, asphaltenes are insoluble in paraffin solvents but soluble in aromatic solvents. Structurally, asphaltenes... 

The present study was undertaken in an effort to gain a better understanding of certain aspects of the reactions involved in the gasification of cokes deposited on catalyst substrates in these applications. Solid substrates were coked with a petroleum residuum under simulated conditions and the substrate-supported coke was then reacted with steam. Effluent gases were analyzed, and the kinetics of gasification and the effects of substrates identities and metal impregnations were examined. 

Coke (65996-77-2), the solid remains, about 70% of the coal weight. Coke is primarily used for the reduction of iron and other metal ores in blast furnaces. Coke may be generated from other sources including petroleum residuum (petroleum coke). 

Generally, asphalt can be fractionated into four important fractions saturates, aromatics, resins, and asphaltenes . The classic definition of fractions of asphalts is based on the solution properties of petroleum residuum in various solvents. A complete fractionation scheme is given in Figure 1 (1) the oil constituents are propane soluble (2) resins are n-pentane soluble but propane insoluble (3) asphaltenes are toluene soluble but n-pentane insoluble and (4) preasphaltenes are insoluble both in n-pentane and toluene. The fractionated part of oil is generally considered to be a combination of saturates and aromatics. The polarity of these four fractions increases from saturates, to aromatics, to resins, to asphdtenes. 

Most of the measurements on diffusivities of compounds in the liquid phase, in catalyst pores, have been made with small molecules. Recently Chantong and Massoth [26] measured diffusivities of non-metallic porphyrin molecules. Baltus and Anderson [27] made diffusivity measurements using narrow molecular weight fractions of a petroleum residuum. In their work tetrahydrofuran asphaltenes were separated into five fractions by gel permeation chromatography. The polystyrene equivalent average molecular weights they reported were 3000, 6000, 12000, 24000, and 48000. 

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