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Energy & Fuels 1988,2, 628-633
asphaltene and produces lower molecular weight, heptane-soluble products.
Conclusions 1. Asphaltene reacts thermally to maltenes, gases, and lower molecular weight, more hydrogen-deficient asphaltenes. The reacted asphaltene can then undergo further thermal degradation to produce coke (the aromatic, asphaltenic core stripped of its peripheral substituents) or catalytic upgrading to maltenes. The coke and maltene fractions crack to lighter products via secondary reactions. 2. The effect of reaction environment can be summarized as follows. Thermal reactions in the absence of an effective hydrogen donor lead to high asphaltene conversions and high yields of coke. In the presence of a hydrogen donor, asphaltene is converted more slowly but also more selectively to maltenes: the ultimate yield of coke is expected to be comparable to that from neat pyrolysis. Addition of a hydrotreating catalyst produces intermediate
reaction rates and maintains high selectivities to maltenes, even at high conversions. 3. The reduction in asphaltene molecular weight during thermolysis suggests that catalytic reactions (e.g., HDS and HDM) will substantially follow thermal degradation. However, a proportion of the vanadium in asphaltenes remains in thermally stable, high-molecular-weight moieties; thus, complete demetalation will require catalysts with pores large enough to accommodate these compounds.
Acknowledgment. This work was supported in part by the Phillips Petroleum Co. and the Center for Catalytic Science and Technology of the University of Delaware. Registry No. Tetralin, 119-64-2;toluene, 108-88-3; methane, 74-82-8; ethene, 74-85-1; ethane, 74-84-0; hydrogen sulfide, 7783-06-4; propene, 115-07-1;carbon dioxide, 124-38-9;propane, 74-98-6; isobutane, 75-28-5; butane, 106-97-8; octane, 111-65-9; decane, 124-18-5; dodecane, 112-40-3; tetradecane, 629-59-4; hexanedecane, 544-76-3;octadecane, 593-45-3;eicosane, 112-95-8; docosane, 629-97-0; tetracosane, 646-31-1.
Particle Size Reduction Studies on Green River Oil Shale G. Brons* and M. Siskin* Corporate Research Laboratories, Exxon Research and Engineering Company, Annandale, New Jersey 08801 Received December 30, 1987. Revised Manuscript Received March 11, 1988
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Green River oil shale (GROS) containing -20 wt % organic material is a hard, nonporous rock that has a compressive strength of 10000 psi and a pore volume of 0.005 mL/g. Experiments were carried out by mildly agitating large shale particles in various aqueous solutions at 60 OC to soften and/or create porosity in the shale by swelling the clays and/or kerogen. The experiments were followed by quantifying the degree of comminution and softening that took place. Three main products were obtained in each case: (1) unchanged large particles, (2) slightly reduced particles, and (3) fines (-100 mesh). Elemental analysis of each of these products showed little differences in composition. The effect of each solvent was directionally the same as the effect of each solvent on the swelling of illite, the major clay mineral in GROS. Larger particles produced more fines via a mechanical (attrition) mechanism, but the major mechanism in all of the particle size reductions (comminution) is swelling and weakening of the inorganic matrix, which alters the hardness of the shale as evidenced by non-Gaussian particle size distribution curves.
Introduction Green River oil shale containing -20 wt % organic material is a hard, nonporous rock that has a compressive strength of loo00 psi1 and a pore volume of -0.005 mL/gS2 Coals, in comparison, possess much larger pore volumes3 and have compressive strengths that average between 300-3000 psi.* It is desirable to decrease the compressive strength and increase the porosity of Green River oil shale to facilitate chemical conversion. We therefore undertook a screening study to determine if simple pretreatment of the raw shale with solvents that swell the kerogen and/or clays could be used to facilitate the creation of porosity (1) Baughman, G.L. Synthetic Fuels Data Handbook; Cameron Eneineers: Denver. CO. 1978: DD 33-36. (2) Dinneen, G.U.’Presen%d at the American Society of Mechanical Engineers Meeting, New York, 1972. (3) Gan, H.; Nandi, S. P.; Walker, P. L. Fuel 1972, 51, 272. (4) Baughman, G. L. Fuel 1972,51, 168-171.
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or softening of the particles by creating stresses at the organic-mineral interfaces. Chan and Yen5 contacted several shales with ammonia, ammonium hydroxide, and hydrazine hydrate for 24 h at room temperature. The more loosely packed shales, obtained from shallow burial depths, were more susceptible to chemically induced fracturing. Hydrazine caused more extensive fracturing than ammonia or ammonium hydroxide, and with the ammonia only, the extent of fracture increased with reaction time. On the basis of their X-ray scattering studies, the authors dismissed the possibility that the fracturing effect might be the result of claymineral interactions. However, intercalation of the compound could expand the clay layers and cause weakening of the bonding forces between them so that subsequent (5) Chan, M.; Yen, T. F. Fuel 1981, 60, 1174 and references cited therein.
0 1988 American Chemical Society
Energy & Fuels, Vol. 2, No. 5, 1988 629
Particle Size Reduction Studies 100
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dolvent S p t e m l A MethanoWater (1385 V/V) 0 1M(NH,),S0,/NH40H (pH 10.0) 0 0.4N HzSO, 0 2M(NH4),SOa (0.1 Wt.% CO-730) 0 2M(NH,)2S04/H,S04 (pH 2.5) 0 Water Methanol 0 2M(NH4)*S04 A 4M(NH4)2S04(14 Vol.% Methanol) 0 4M(NH4),SO4 Q3 Toluene
53.0
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lnltlal Particle SI0 -20 Mesh A -30 Mesh 0 -40 Mesh 0 -60 Mash 0 -80 Mesh
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Volume H Methanol In Water
Figure 2. Particle size reduction of 10/20 mesh Green River oil shale after treatment at 60 "C for 41 h with methanol/water
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sulfate alone. Also, when 15 vol % methanol was added to either 4 M ammonium sulfate or water, 50% more reduction was observed over either solution alone. The concentration of methanol in water was studied in more detail (Figure 2). These methanol-water solutions yielded the most particle size reduction. The solutions containing from 15 to 50 vol % methanol in water reduced -30 wt % of the original 10/20 mesh shale to particles
