Catalytic Hydrotreating of Crude Pongamia pinnata Oil to Bio-Hydrogenated Diesel over Sulfided NiMo Catalyst

Abstract

This work studied the catalytic activity and stability of Ni-MoS2 supported on γ-Al2O3, SiO2, and TiO2 toward deoxygenation of different feedstocks, i.e., crude Pongamia pinnata oil (PPO) and refined palm olein (RPO). PPO was used as a renewable feedstock for bio-hydrogenated diesel production via catalytic hydrotreating under a temperature of 330 °C, H2 pressure of 50 bar, WHSV of 1.5 h−1, and H2/oil (v/v) of 1000 cm3/cm3 under continuous operation. The oil yield from a Soxhlet extraction of PPO was up to 26 wt.% on a dry basis, mainly consisting of C18 fatty acids. The catalytic activity in terms of conversion and diesel yield was in the same trend as increasing in the order of NiMo/γ-Al2O3 > NiMo/TiO2 > NiMo/SiO2. The hydrodeoxygenation (HDO) activity was more favorable over the sulfided NiMo supported on γ-Al2O3 and TiO2, while a high DCO was observed over the sulfided NiMo/SiO2 catalyst, which related to the properties of the support material and the intensity of metal–support interaction. The deactivation of NiMo/SiO2 and NiMo/TiO2 occurred in a short period, due to the phosphorus and alkali impurities in PPO which were not found in the case of RPO. NiMo/γ-Al2O3 exhibited the high resistance of impure feedstock with excellent stability. This indicates that the catalytic performance is influenced by the purity of the feedstock as well as the characteristics of the catalysts.

Review of Molybdenum Disulfide Research in Slurry Bed Heavy Oil Hydrogenation

“…For example, K in the feedstock causes an increase in the electronic charge on the MoS 2 material, raises the surface alkalinity, and blocks the Mo and S edges, inhibiting the catalytic activity and limiting the access of hydrogen to the MoS 2 surface. In particular, the decrease in HDS and HDO activity and the slight decrease in hydrogenation activity are related …”

“…Zhang et al hydro-deoxidized fatty acids and triglycerides to produce diesel fuel. Based on the equilibrium constant of the reverse water-vapor transfer reaction, it is indicated that CO will be the main gaseous product of the hydrodecarbonization reaction . Comparing the variation of CO and CO 2 concentrations, it was found that the decarboxylation effect of molybdenum disulfide is slightly higher (1–5 times) than the decarbonylation effect …”

“…Based on the equilibrium constant of the reverse water-vapor transfer reaction, it is indicated that CO will be the main gaseous product of the hydrodecarbonization reaction. 39 Comparing the variation of CO and CO 2 concentrations, it was found that the decarboxylation effect of molybdenum disulfide is slightly higher (1−5 times) than the decarbonylation effect. 41 Hydrodesulfurization can be considered the most efficient technique to remove sulfur from oil, resulting in clean hydrocarbons.…”

“…In particular, the decrease in HDS and HDO activity and the slight decrease in hydrogenation activity are related. 39 …”