New Catalysts for the Synthesis of Green Diesel by Deoxygenation of Vegetable oils

The thesis project focuses on the synthesis of new catalysts for the production of Green Diesel through the catalytic deoxygenation (CDO) reaction of vegetable oils. Green Diesel is a renewable hydrocarbon biofuel capable of replacing mineral diesel derived from fossil sources. Several transition metal catalysts supported on Cenospheres (FAC) and layered double hydroxides (LDH) were synthesized and tested in the CDO of vegetable oils. FACs are waste materials derived from coal combustion in power plants, and their reuse as catalyst supports offers significant environmental advantages. LDHs are synthetic green and cost-effective materials that can be a viable alternative to typical catalysts used in the CDO reaction. The catalysts were tested in the CDO of vegetable oils in a batch reactor under a hydrogen atmosphere and at different reaction conditions (time, catalyst percentage, and temperature). FAC-supported catalysts were synthesized via excess wet impregnation, while LDHs were synthesized using the co-precipitation process. Before being tested in the CDO, both catalytic systems were calcined and activated through reduction, and the most promising catalysts were characterized using ICP-MS, PXRD, FT-IR ATR, and BET-BJH techniques, while the reaction products obtained from the CDO were characterized using GC-MS, GC-FID, and FT-IR ATR. In the case of FACs, a NiMo(5/15)/FAC catalyst was developed, which achieved 100% conversion and a diesel yield of 66.2 wt%. The catalyst was also tested for multiple catalytic cycles and with different vegetable oils, showing high activity with all vegetable oils but rapid deactivation over multiple catalytic cycles. However, the catalyst's activity was fully restored after regeneration through calcination and reduction. For LDH-based catalysts, a NiMoAl (0.6) LDH was synthesized, which exhibited high activity in the CDO of rapeseed oil. With this catalyst, 100% conversion and a diesel yield of 67.1 wt% were achieved. Furthermore, this catalyst maintained its activity for at least five catalytic cycles, consistently showing 100% conversion. As evidence of its excellent catalytic properties, the NiMoAl (0.6) catalyst displayed high activity under various reaction conditions, even without reduction activation. Given the excellent results shown by this catalyst, additional LDHs were synthesized, and catalytic screening was performed. From the screening, other catalysts also proved to be particularly promising, especially a trimetallic catalyst based on Ni, W, and Al, which will be the subject of future studies. In conclusion, after three years of doctoral research, a series of economical and green catalysts have been developed that are highly efficient in the CDO of vegetable oils, representing a valid alternative to the catalysts currently used at the industrial level.