Evaluation of hydrocracking catalysts in recycle tests

Abstract

Hydrocracking is a flexible process for the conversion of heavy feeds (vacuum gas oils, cycle oils) into naphtha, kerosine and gas oil. In hydrocracking two trends can be observed outside North America: processing of heavier feeds (whitening of the barrel) and the increased demand for middle distillates. New catalysts are being developed for these purposes. Normally, the performance of new catalysts is tested in simple, relatively cheap, once-through runs. Commercial hydrocrackers, however, often operate with recycle of unconverted feed. This implies that refrac- tory components such as polyaromatics and bulky polynaphthenes can build up in the recycle stream and, depending on the catalyst used, might adversely affect the unit performance. Therefore, recycle tests are required for catalyst development and to ensure correct performance assessment ranking of catalysts for use in commercial recycle operation. Small-scale recycle equipment has been developed at Koninklijke/Shell-Laboratorium, Amsterdam in which as little as 10 grams of catalyst can be used. Some of the concepts and applications of this small-scale recycle equipment are discussed.