Effect of Precipitating Some of the More Intractable Material from a Hydrogen-Donor Solvent Coal Extract Solution on Its Hydroprocessing Behavior

Abstract

In view of the fact that the Ni/Mo γ-alumina catalysts currently used deactivate rapidly during coal liquids hydroprocessing, the feasibility of removing the more intractable material from a typical coal extract solution prepared with hydrogenated anthracene oil (HAO) was examined by precipitation with toluene both prior to and after filtration. The reductions in total conversion to pyridine solubles of only 3−4% achieved were accompanied by a decline of nearly 50% in the THF-insoluble concentrations for the modified extract solutions. As the amount of toluene added to approximately 1 kg of the coal/HAO digest was reduced below 300 cm3, the ash contents of the resultant filtered extract solutions increased toward the normal concentration of ca. 0.03% obtained without precipitation. Batchwise and continuous hydroprocessing tests conducted on the normal and modified coal extract solutions with a commercial Ni/Mo γ-alumina-supported catalyst demonstrated that the lower concentrations of THF insolubles gave rise to significant improvements in conversion for the n-hexane, toluene, and THF insolubles in the feeds. In accord with their higher surface areas and lower carbon contents, the HDS activities of catalyst samples recovered from a continuous run with feed modified by toluene addition were considerably higher than those for the corresponding samples for the normal feed.

Fractionation of Coal Extracts Prior to Hydrocracking: An Attempt to Link Sample Structure to Conversion Levels and Catalyst Fouling

“…During the hydrocracking of heavy hydrocarbon liquids, the loss of activity of supported NiMo and CoMo/γ-Al 2 O 3 catalysts is widely accepted to be “rapid”. ,,, It is commonly thought, however, that time-spans relevant to loss of activity usually extend to tens or hundreds of hours . Our experiments show this process to be rather more rapid.…”

“…So far, data from this and previous studies have shown that deposition of carbonaceous material on catalyst particles takes place rapidly and in significant amounts, relative to the mass of catalyst. We have also seen that the concentration of high mass material in the feed has a direct bearing on the amount of deposition on catalyst surfaces. , However, deposition of carbonaceous material on catalyst particles cannot be an endless sink of valuable coal extract. In steady-state systems, levels of deposition appear to stabilize within a matter of hoursor tens of hours at most.…”