Abstract
The co-processing of an unconventional type of Jatropha bio-oil with petroleum distillates over mesoporous alumina-supported CoMo and NiMo sulfide catalysts (denoted CoMo/gamma-Al2O3 and NiMo/gamma-Al2O3) was studied. Either a stainless-steel high-pressure batch-type reactor or an up-flow fixed-bed reaction system was used under severe reaction conditions (330-350 degrees C and 5-7 MPa), similar to the conditions of the conventional diesel hydrodesulfurization (HDS) process. To understand the catalytic performance of the mesoporous sulfide catalysts for co-processing, we prepared two series of oil feedstocks. First, model diesel oils, consisting of hydrocarbons and model molecules with various heteroatoms (sulfur, oxygen, and nitrogen) were used for the study of the reaction mechanisms. Secondly, low-grade oil feedstocks, which were prepared by dissolving of an unconventional type of Jatropha bio-oil (ca. 10 wt %) in the petroleum distillates, were used to study the practical application of the catalysts. Surface characterization by gas sorption, spectroscopy, and electron microscopy indicated that the CoMo/gamma-Al2O3 sulfide catalyst, which has a larger number of acidic sites and coordinatively unsaturated sites (CUS) on the mesoporous alumina framework, was associated with small Co-incorporated MoS2-like slabs with high stacking numbers and many active sites at the edges and corners. In contrast, the NiMo/gamma-Al2O3 sulfide catalyst, which had a lower number of acidic sites and CUS on mesoporous alumina framework, was associated with large Ni-incorporated MoS2-like slabs with smaller stacking numbers, yielding more active sites at the brims and corresponding to high hydrogenation (HYD) activity. Concerning the catalytic performance, the mesoporous CoMo/gamma-Al2O3 sulfide catalyst with large CUS number was highly active for the conventional diesel HDS process; unfortunately, it was deactivated when oxygen- and nitrogen-containing model molecules or Jatropha bio-oil were present in the oil feedstock. In contrast, the mesoporous NiMo/gamma-Al2O3 sulfide catalyst, which had a high HYD activity and low affinity for heteroatoms, was efficient in the simultaneous removal of those heteroatoms from model diesel oils, and, in particular, Jatropha bio-oil co-fed with petroleum distillates. This could allow the production of a drop-in diesel-like fuel, which would be a greener fuel and reduce the CO2 emissions and hazardous exhaust gases produced by the transport sector, reducing the burden on the environment.
