COAL HYDROCOPROCESSING WITH TIRES AND TIRE COMPONENTS

This paper shows that the addition of rubber from old tires to dry coa l hydrogenation always has a positive effect and promotes the formatio n of oils. This is the first time that components from tire rubber hav e been coprocessed with coal in order to gain knowledge of the specifi c role played by each in coal-tire hydrocoprocessing. A subbituminous coal, typical of the northeast of Spain, which shows good conversions in dry hydrogenation at nonsevere conditions because it reaches 75% at 400 degrees C and 10 MPa for 30 min without a catalyst, was hydrocopr ocessed with rubber from old tires, and the results are reported in th is paper. The rubber used came from a mixture of old tires, which had been ground and from which the steel thread and the textile netting ha d previously been removed. The coprocessing of both materials was batc h run at 350, 375, and 400 degrees C, keeping constant the initial hyd rogen pressure, 10 MPa, and the residence time, 30 min, but varying th e ratio between both materials (1/0, 4/1, 2/1, 1/1, 1/2, 1/4, and 0/1) in the feed mixture. The influence of the feed composition was also s tudied for the first time. Despite the fact that total conversions and gas formation do not undergo significant variations in comparison wit h the ones when only coal is processed, oils conversion (43% at 350 de grees C and 45% at 400 degrees C with 20% coal-40% rubber feed) and oi ls selectivity (93% at 350 degrees C and 85% at 400 degrees C with 20% coal-40% rubber feed) show important increases, mostly when rubber-ri ch feeds are processed. Furthermore, asphalthenes formation decreases with increasing rubber percentages in the feed mixture. Results obtain ed show that the addition of rubber from old tires to coal hydrogenati on always promotes the percentage of oils formation. To enter into the coal-tire interactions, three main components from the same tire rubb er, carbon black (CB), polybutadiene (PB), and styrene-butadiene (SBR) were processed alone and with coal. In addition, polystyrene (PS) was coprocessed with coal. Conclusions show that CB catalyzes the process by promoting hydrocracking reactions, and secondary reactions, by bre aking the hydrogenation products from direct hydrogenation, primary re actions, into smaller and lighter molecules leading to gas formation. PB addition has no affect at 350 degrees C, but at 400 degrees C it si gnificantly improves total conversions (from 75% to 88%) and oils conv ersion (from 12% to 36%), giving intermediate conversions at 375 degre es C. With regard to SBR, significant improvements on results are alre ady reached at 375 degrees C. Model compounds were not used in this wo rk, but from the bulk of results obtained from the 29 different experi ments carried throughout this research, it appears that from all the p ossible interactions between radicals involved in the coal-rubber hydr ocoprocessing, those implying the alkylation of the aromatic radicals from rubber by all the radicals involved in the process are promoted.