Vapor and Liquid Phase Hydrotreatment of Hydropyrolysis Tar with Hydrous Titanium Oxide Catalysts

摘要

Thermal decomposition of coal under hydrogen pressure (hydropyrolysis) is a possible route to chemical feedstocks and synthetic fuels. Tar yields are significantly higher than those obtained by conventional carbonization. Above about 750 sup 0 C, primary tars hydrocrack to give appreciable yields of benzene and ethane. Unfortunately, methane yields and, consequently, hydrogen consumptions are also high. However, tar vapors can be catalytically hydrotreated at about 400 sup 0 C to give distillable liquids. In early studies, the yields were low (<10% daf coal) principally because the reactors were operated at relatively low pressure (<50 bar). Recently, much higher yields of low boiling products (20 to 25% daf coal) with little methane have been obtained in a two-stage fixed-bed reactor operated up to 250 bar and using a commercial Ni-Mo/alumina catalyst. Previous work by one of the authors has demonstrated that hydrous titanium oxide (HTO) exchanged with Pd can hydrogenate polynuclear aromatic compounds at much lower temperatures and pressures than conventional Ni-Mo and Co-Mo on alumina catalysts. In the present study, HTO formulations containing Ni, Co, Mo and Pd have been used to hydrotreat tar produced by hydropyrolysis. Batch liquid-phase hydrotreatment of condensed tar was initially used to compare the activity of the catalysts. Subsequently, the catalysts were employed to hydrotreat tar vapors passed through the catalytic stage of a two-stage hydropyrolysis reactor. The results of these tests with the HTO catalysts are compared to those obtained with a commercial Ni-Mo/alumina catalyst. 9 refs., 1 tab. (ERA citation 12:044862)