Highly Dispersed Pd on Zeolite/Carbon Nanocomposites for Selective Hydrodeoxygenation of Biomass-Derived Molecules under Mild Conditions

Abstract

Herein, a defective zeolite–carbon (CFR@HZSM-5) nanocomposite-supported nano-scale Pd catalyst (Pd/CFR@HZSM-5) was facilely synthesized for selective “H2-free” hydrodeoxygenation (HDO) of vanillin (VL) under mild conditions. The optimal Pd/CFR@HZSM-5(2:1) catalysts show excellent activity (the 99% yield to 2-methoxy-4-methylphenol) and high turnover frequency in polymethylhydrosiloxane at 60 °C. According to spectral analysis, there is an abundant carbon defect structure on the surface of the CFR@HZSM-5 nanocomposite, which can provide unique sites for capturing Pd metal nanoparticles (NPs) and serve as active sites to promote the adsorption of substrates. The stable and high-dispersion Pd NPs are fastened with carbon atoms in the vacancy defect through strong electronic metal–support interactions, which improved the activity of VL HDO up to four times higher than that of other catalysts under mild conditions. The unique high-dispersion Pd structure and abundant surface defects of Pd/CFR@HZSM-5 catalysts are significant features to brilliant catalytic activity for biomass-derived molecule HDO. Meanwhile, the abundance of acidic sites in the composite carrier catalyst replaces the use of acidic additives in previous catalytic systems. The optimal Pd/CFR@HZSM-5(2:1) catalysts showed good recovery even after five uses. The catalytic system was also applied for various biomass HDO models under mild conditions. This methodology opens new ideas for designing catalysts with high activity and high efficiency for selective HDO of biomass under green and mild conditions.

Sustainable biomass hydrodeoxygenation in biphasic systems

“…151 For these reasons, vanillin represents a good model compound for the HDO reaction of biomass in water-oil biphasic systems. [152][153][154] Typically, vanillin HDO passes through a first hydrogenation step of the aldehyde group to form vanillyl alcohol, which subsequently undergoes HDO to p-cresol, and sometimes the formation of guaiacol and hydrocarbons is also reported. Fig.…”

Metal@hollow carbon sphere nanoreactors for sustainable biomass and CO2valorization

“…The combination of phosphorus species and defects facilitates the adsorption and dissociation of H 2 . A defective zeolite-carbon (CFR@HZSM-5) nanocomposite supported nanoscale Pd catalyst (Pd/CFR@HZSM-5) was cleverly prepared for the selective ‘hydrogen-free’ oxygenation (HDO) reaction of vanillin (VL) to MMP under mild conditions 166 (Fig. 19a–e).…”

Atom Doping Engineering of Metal/Carbon Catalysts for Biomass Hydrodeoxygenation

“…From the perspective of green chemistry and industrial applications, HDO is considered to be the most important and promising method for converting biomass into high-value chemicals . Various metal/carbon catalysts, such as Pd/C, − Pt/C, , Ru/C, , and Ni/C, − have been widely used for the transformation of biomass . Guo et al developed Ru/C catalysts for the HDO of bio-oil, and the yield of the extracted oil was in the range of 30–65 wt %.…”