(535d) Study on Single-Step Hydrogenation of Soybean Oil for Biofuel with ZSM-5 Supported Nickel-Molybdenum Bimetallic Catalysts

In this work, the effect on different alkali treatments of zeolite ZSM-5 for Ni-Mo/ZSM-5 catalysts to the single-step hydrogenation of soybean oil for biofuels was studied. The properties of zeolite ZSM-5 as an acidic support were modified through hydrothermal and alkali treatments, prior to loading Ni-Mo bimetallic catalysts via the incipient wetness impregnation. In our conjecture, Ni serves as H₂ activation centers, diffusing activated hydrogen to other active sites through hydrogen spillover mechanisms, while molybdenum provides oxygen vacancies, enhancing selectivity towards C-O bond cleavage. The metallic oxides were firstly reduced to metallic states under hydrogen atmosphere at 550°C. The catalysts were characterized by XRD, XPS, SEM, TEM, ICP-OES, H₂-TPR, NH₃-TPD, Pyridine-IR, CO-pulse and N₂ physisorption analyzer. Unlike the commercial two-step reaction process, this study aimed to achieve hydrogenation-deoxygenation and hydrogenolysis/isomerization reactions simultaneously in one step.

The hydrotreatment of soybean oil was performed using decalin as the solvent and various catalysts in a semi-batch reactor for 6 h. The products were analyzed quantitatively by GC-FID and qualitatively by FTIR and GC-MS. The objective is to achieve the maximum yield while operating within the reaction pressure fixed at 40 bar of hydrogen, and reaction temperatures from 300°C to 350°C. (Figure 1)

Comparing catalysts with zeolite ZSM-5 supports priorly treated with different alkali concentrations, it's observed that selectivity of liquid hydrocarbon products towards higher carbon numbers increased notably with higher alkali concentrations. To attain more sustainable aviation fuel (SAF) as possible, the focus of this research work was shifted towards products with medium carbon numbers. Despite the burgeoning development of alternative energy sources, the aviation industry, reliant on high energy density fossil liquid fuels for long-distance transport, still necessitates them. Hence, ZSM-5 is subjected to hydrothermal treatment to promote the formation of MCM-41/ZSM-5 composite materials, augmenting catalyst surface area and mesopore volume. This augmentation facilitates the diffusion and reaction of triglycerides, thus improving selectivity towards medium carbon numbers. Finally, recyclability tests of the catalyst probe whether the nickel-molybdenum bimetallic catalysts retain good deoxygenation capabilities after catalysis.