Effect of the Composition and Synthesis Procedure of Catalysts Based on CoAl Hydroxides on Their Properties in Furfural Hydrogenation.

The CoAl hydroxides with Co/Al ratios of 2 and 4 were synthesized using traditional coprecipitation and a mechanochemical method. The structural properties of the samples at all stages of catalyst preparation, the transformations occurred on the reduction of cobalt from corresponding oxides, the textural characteristics of calcined and reduced systems, and the size, morphology, and composition of particles formed after high-temperature treatments were studied in detail. It was established that the synthesis procedure of CoAl hydroxides has a significant effect on the phase composition and properties of the resulting systems. The layered double hydroxide phase was formed only when the coprecipitation method was used. The mechanochemical approach made it possible to obtain materials with a higher specific surface area. According to TEM data, the samples synthesized by coprecipitation (after oxidative and reductive treatments) had a core–shell structure, where the core included metallic Co atoms and the shell mainly consisted of CoAl spinel. The samples prepared by the mechanochemical method had highly dispersed Co nanoparticles on their surface. The catalysts based on CoAl systems prepared by the mechanochemical method were more active in the hydrogenation of furfural: its conversion reached 97% on a sample with the ratio Co/Al = 4. In this case, the selectivity for furfuryl alcohol formation on the studied catalysts was almost 100% regardless of the synthesis procedure and Co/Al ratio. [ABSTRACT FROM AUTHOR]