Effects of Titanocene Dichloride on the Hydrotreatment of Coal Liquids

Abstract

Deposition of trace elements on hydrotreatment catalyst is an important deactivation mechanism. Titanium is one of the trace elements usually presnet in coal liquids, presumably as an organometallic compound. In catalytic hydrotreatment process, it is found to penetrate and deposit deeply into the pores of catalysts, and is commonly blamed for deactivation of catalysts. In this thesis, in order to study the role of titanium in the hydrotreatment process, an SRC light oil was doctored with titanocene dichloride and hydrotreated in a trickle bed reactor over a commercial Ni-Mo/alumina catalyst and over glass beads. The effects of different concentrations of titanocene dichloride on the HDS, HDN, HDO and hydrogenation of the oil and on catalyst coking, pore size, surface area and titanium deposit content are measured and studied. Titanium is easily removed from the oil and deposits on the catalysts with the carbonaceous coking material. Both coking and titanium deposition on the catalyst appear to follow a parallel fouling model. Contrary to common expectations, titanocene dichloride did not deactivate the catalyst, but rather its presence in the feedstock improved the hydrotreatment activity of the catalyst. Titanium concentrations of 100 to 200 ppm appear to promote the catalyst, but high concentrations show lower activity and cause the reactor plugging.