Toward maximizing the selectivity of diesel-like hydrocarbons from oleic acid hydrodeoxygenation using Ni/Co-Al2O3 embedded mesoporous silica nanocomposite catalysts: An experimental and DFT approach.

[Display omitted] • M−Al 2 O 3 /SiO 2 composite catalysts are superior HDO catalysts compared to the non-modified SiO 2 based one. • Ni and NiCo based catalyst favored deCOx pathway, whereas Co one favored HDO pathway. • DFT calculations showed that NiCo bimetallic catalyst favors stronger adsorption of oleic acid. • Higher charge transfer happens from the bimetallic surface to the oleic acid. The development of an effective hydrodeoxygenation (HDO) catalyst is crucial for controlling product selectivity and catalyst stability. In this study, we synthesized monometallic (Ni and Co), as well as a bimetallic, NiCo embedded mesoporous composite catalysts using a simple one-step method involving meso -macroporous silica, boehmite, nickel acetate, and cobalt acetate. The synthesized range of catalysts (5, 10, 15 wt% Ni, 10 wt% Co, 10 wt% NiCo) were thoroughly characterized by various techniques. The characterization results showed that the present method leads to the growth of nano-catalyst on porous silica surface (M−Al 2 O 3 /SiO 2, M = Ni, Co, NiCo). These composites exhibited strong metal-support interaction, improved surface and texture properties and significant amount of weak to medium acid sites. The M−Al 2 O 3 /SiO 2 composite catalysts demonstrated improved catalytic performance in the HDO of oleic acid. At temperature of 375 °C, the conversion trend of catalysts followed the order; 10NiCo-Al 2 O 3 /SiO 2 (89%) > 10Ni-Al 2 O 3 /SiO 2 (87%) > 10Co-Al 2 O 3 /SiO 2 (85%) > 10Ni/SiO 2 (81%). Moreover, the yield of C 15 -C 18 hydrocarbons was substantially enhanced at moderate temperature compared to unmodified silica support. Time-on-stream experiments further confirmed the relative stability of the composite catalysts over a period of 20 h. Furthermore, density functional theory (DFT) ab initio calculations were performed where the adsorption of oleic acid on icosahedral monometallic M 13 (M = Co or Ni) and bimetallic N i 2 C o 2 nanocluster deposited on γ-Al 2 O 3 (1 1 0) support was investigated. The adsorption strength for the most stable conformations followed the order: N i 13 /amorphous SiO 2 > N i 2 C o 2 /Al 2 O 3 > C o 13 /Al 2 O 3 > N i 13 /Al 2 O 3. Bader charge transfer analysis indicated higher charge transfer at the interfaces of γ-Al 2 O 3 A l 2 O 3 (1 1 0) supported catalysts compared to N i 13 /amorphous SiO 2 surface. [ABSTRACT FROM AUTHOR]