Effect of modifying host oil on coprocessing

摘要

The world's supply of petroleum crudes is becoming heavier in nature so that the amount of vacuum bottoms has been steadily increasing. Coprocessing of coal with these resids (1,000 F+) is an attractive way of obtaining useful distillates from these readily available cheap materials. The objective of this work is to pretreat the host oil in ways that would improve its performance in coprocessing with coal. The following are examples of some ways in which heavy oil could be made into a better host oil: converting aromatic structures to hydroaromatics capable of donating hydrogen to coal, cracking the heavy oil to lower molecular weight material that would be a better solvent, and removing metals, sulfur, and nitrogen. The work reported here used a Venezuelan oil obtained from the Corpus Christi refinery of Citgo. Two coals, Illinois No. 6 and Wyodak subbituminous, were coprocessed with host oils. The authors have found that mild pretreatment of a Citgo resid (1,000 F) using either Mo naphthenate or Mo/Fe(sub 2)O(sub 3)/SO(sub 4), as well as a pretreatment using the homogeneous catalyst Co(sub 2)(CO)(sub 8) under synthesis gas can increase the available (donatable) hydrogen content of the resid. When these pretreated oils were thermally (no added catalyst) coprocessed with an Illinois No. 6 coal, about 90 wt% of the coal (maf) was converted to soluble products. This high coal conversion was realized even at a high coal loading of 50 wt%. The products from coprocessing coal and oil were equally split between high boiling material, mostly asphaltenes, and distillate. Distillate yields appeared to be affected by the concentration of coal in the feed, with maximum yields at coal loadings below 50 wt%.