Abstract
CuZn catalysts are perspective catalysts for esters hydrogenolysis, but more knowledge is needed to optimize their catalytic performance. In this work, we consider the impact of CuZn catalysts composition on their structure, activity, selectivity, and stability in esters hydrogenolysis. Four catalysts with various Cu/Zn ratio were synthesized by a co-precipitation and characterized in as-prepared, calcined, reduced, and spent state by XRF, XRD, N2 physisorption, CO2-TPD, NH3-TPD, and N2O chemisorption. XRD data revealed the effect of the composition on the size of Cu and ZnO particles. The catalytic performance was investigated using an autoclave. All catalysts exhibited high methyl hexanoate conversion about 48–60% after 3 h but their activity and selectivity were found to be dependent on Cu/Zn ratio. The conversion of methyl hexanoate and hexyl hexanoate was compared to explain the observed product selectivity. Moreover, the catalysts stability was investigated in three consecutive reaction cycles and correlated with changes in the size of constituent particles. Moreover, when different esters were tested, a slight decrease in conversion and increase in alcohol selectivity with a growth in molecule size was observed. Obtained results allow making a conclusion about the optimal composition that provides the good performance of CuZn catalysts in ester hydrogenolysis.
Highlights
The hydrogenolysis of carboxylic acid esters is a reaction of great commercial attractiveness
XRF analysis evidenced that the obtained Cu/Zn ratios in the as-prepared precursors were very close to the theoretical values estimated from the chemical composition of Catalysts 2021, 11, 1417 the corresponding reaction mixtures used for the synthesis of the samples (Table 1)
The results presented in this study contribute to the understanding of the catalytic performance of CuZn catalysts in the hydrogenolysis of carboxylic acid esters to corresponding alcohols
Summary
The hydrogenolysis of carboxylic acid esters is a reaction of great commercial attractiveness. The process of obtaining alcohols from carboxylic acid esters has been based on employing traditional and highly efficient Adkins catalysts, which include copper as an active metal and Cr2 O3 Cr-free catalysts based on noble metals, i.e., Pd [8,9], Pt [10,11], Ru [12,13], and Rh [14], demonstrate good catalytic performance in the hydrogenolysis of esters to corresponding alcohols at mild reaction conditions. Our previous research on the catalyst systems containing Cu as an active part promoted by
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