Controlled Hydrodeoxygenation of Biobased Ketones and Aldehydes over an Alloyed Pd-Zr Catalyst under Mild Conditions

The substitution of green hydrogen donors for replacing high-pressure H-2 to achieve biomass derived ketone and aldehyde hydrodeoxygenation (HDO) under mild conditions has attracted widespread attention. However, it remains a considerable challenge to get rid of acid additives and control product selectivity. Herein, a series of bimetallic Pd-M/HZSM-5 catalysts (M = Zr, Mn, Zn, or La) were fabricated for controlled hydrodeoxygenation of biobased ketones and aldehydes (acetophenone, benzophenone, 4-hydroxyacetophenone, vanillin, furfural) using polymethylhydrosiloxane (PMHS) as the green H-donor, in which >99% conversion and >99% selectivity to ethylbenzene were achieved for hydrodeoxygenation of acetophenone as the probe within 3 h at 35 degrees C over the as-prepared 0.5%Pd-2.0%Zr/HZSM-5 catalyst with a Pd/Zr mass ratio of 1:4. According to characterizations of TEM-HAADF, XPS, ESR, and H-2-TPR, the Pd-Zr alloy structure was formed on the bimetallic Pd-Zr/HZSM-5 catalyst, promoting the transform of Pd-O-Zr solid solution to PdO-ZrO2 and the generation of oxygen vacancy. Moreover, the abundant of oxygen vacancies on the alloyed Pd-Zr/HZSM-5 catalysts enhance the dissociation of silanes to provide the abundance of hydrogen protons, greatly accelerating the hydrogenation of biobased ketones and aldehydes, and then the acid site of the Pd-Zr/HZSM-5 catalyst promotes the dehydration of the intermediates (alcohols) to hydrocarbons. Furthermore, the as-fabricated Pd-Zr/HZSM-5 alloy catalyst can achieve an excellent recycling capability after six uses and exhibits universality toward various biobased ketones and aldehydes at 35 degrees C. The present findings provide new insights into the design of selective HDO of biomass in a green process.

Automated summary

The study successfully fabricated a series of bimetallic Pd-M/HZSM-5 catalysts for controlled hydrodeoxygenation of biobased ketones and aldehydes using a green H-donor, achieving high conversion and selectivity. Characterizations showed the formation of the alloy structure on the catalyst surface with abundant oxygen vacancies, enhancing hydrogenation and promoting the dehydration of intermediates.