On the chemical effects on catalysts in the direct liquefaction of coal
1986; Elsevier BV; Volume: 12; Linguagem: Inglês
10.1016/0378-3820(86)90076-7
ISSN1873-7188
AutoresH. Charcosset, R. Bacaud, М. Бессон, A. Jeunet, Bernhard Nickel, M. Oberson,
Tópico(s)Lignin and Wood Chemistry
ResumoThe liquefaction of a highly volatile bituminous coal was studied between 350°C and 400°C, using highly dispersed and non porous catalysts, smaller than 0.05 μm in particle size (A12O3, SiO2, C ; SnO2, MoO3, Fe2O3) and two "industrial" catalysts (red mud ; NiMo/A12O3). At 350°C the hydrogenation catalysts were found to strongly promote i) the formation of preasphaltenes ; ii)also the neutralization of the residual free radicals in inertinite, which was not dissolved. These results are interpreted by activated hydrogen spillover from the surface of hydrogenation catalysts to coal entities even inertinite in direct contact with the surface of the catalyst. The results between 350°C and 400°C suggest that reaction times shorter than these used here (t = 1h at the T = f(t) level) are needed to complete the comparison of the above catalysts. The rehydrogenation of polyaromatic hydrocarbons to hydropolyaromatics in presence of hydrogenation catalysts was shown to take place in the present conditions of liquefaction. Some free radicals adsorption by any of the catalysts used, either hydrogenation or not, should be in accord with our data ; it would result in slowing down the retrogressive repolymerization reactions. In the actual conditions of liquefaction, hydrogen itself appears more important than the hydrogen donor hydroaromatics to stabilize the free radicals into coal liquids.
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