Progress in Effects of Microenvironment of Carbon‐based Catalysts on Hydrodeoxygenation of Biomass

Abstract

Carbon‐based catalysts have made significant progress in hydrodeoxygenation (HDO) of biomass. Since the HDO reaction usually carried on surface of catalyst, the interaction of reactant with catalyst is closely related to the surface microenvironment of catalyst, which may further have an impact on catalytic performance. This review will discuss the relationship between surface microenvironment of carbon support and catalytic performance and mechanism of HDO reaction during biomass upgrading. We will focus on the microenvironment effect associated with HDO reaction in carbon‐based catalysts including effects of surface microstructure and surface functionalization of carbon supports on preparation of heterogeneous catalysts and catalytic performance, respectively. Study of microenvironment may provide guidance for further development of efficient carbon‐based catalysts in biomass resource utilization.

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

“…Hydrodeoxygenation (HDO) of biobased ketones and aldehydes, such as acetophenone, benzophenone, 4-hydroxyacetophenone, vanillin, and furfural, can efficiently improve the stability of the bio-oil. Moreover, the selective HDO of the ketones and aldehydes to generate the corresponding alcohols and hydrocarbons has attracted considerable attention, , because the products have been extensively used in industry. As an example of vanillin HDO over 5% Rh/C catalyst, a below 60% yield of vanillyl alcohol was obtained under 0.69 MPa H 2 and 318 K, while the yield of vanillyl alcohol is greater than 70% under extreme conditions (3 MPa H 2 and 373 K) .…”

Sustainable biomass hydrodeoxygenation in biphasic systems

“…Currently, HDO is considered to be the better upgrading technology for biofuels in water-oil biphasic systems, mainly because: (1) during deoxygenation, the oxygen atoms are mostly removed in the form of water, which is friendly to the environment; (2) the reaction process increases the C/H ratio and decreases the O/C ratio, resulting in an increase in the stability and calorific value of the compound; and (3) the hydrodeoxygenation products are easily isolated from the reactants to different phases, effectively improving product selectivity. 102,103 For the HDO of biomass in water-oil biphasic systems, model compounds are often chosen to simplify the reaction system and facilitate the detection of intermediates and products to understand the reaction pattern and mechanism. But it is difficult to elucidate the complex reaction mechanism of the HDO of biomass in water-oil biphasic systems through the catalytic study of only one model compound, since biomass contains a great number of ethers, aldehydes, phenols, ketones and other oxygenated compounds.…”

Hydrogen Spillover‐Enhanced Heterogeneously Catalyzed Hydrodeoxygenation for Biomass Upgrading

“…[138] Moreover, apart from introducing oxygen functional groups, N-doped carbon (NC) materials are considered as promising materials for use as support in multiphase catalysis. [139] Among others, N doping improves the catalytic performance, which can be attributed to (1) the improved hydrophilicity and basicity of support, [140] which enhances the interaction between substrate and support in the reaction systems; (2) the lower dissociation energy of H 2 activation, which is due to the altered electronic structure of the carbon substrate and the modulating activity of the sp 2 carbon and metal particles; [141] and (3) N doping in the carbon structure, which can be considered as a favorable anchor point or defect for enhanced particle nucleation and particle size reduction and improved the dispersion of metal NPs, as well as enhanced support-active sites interactions. [142] The effect of N doping with CB-loaded Ni catalyst (Ni/NCB) on the catalytic activity in water-solvent-based vanillin HDO was investigated, as shown in Figure 19d.…”

“…The introduction of oxygen functional groups into carbon support can significantly increase the hydrogen storage capacity caused by spilled hydrogen on metal‐doped carbon, and the oxygen‐containing functional group promotion is attributed as follows: (1) serving as direct adsorption sites; (2) promoting the formation of spillover H atoms island structures around oxygen functional groups; [48] and (3) facilitating the diffusion and adsorption of hydrogen atoms on the support surface, [137] as shown in Figure 19c [138] . Moreover, apart from introducing oxygen functional groups, N‐doped carbon (NC) materials are considered as promising materials for use as support in multiphase catalysis [139] . Among others, N doping improves the catalytic performance, which can be attributed to (1) the improved hydrophilicity and basicity of support, [140] which enhances the interaction between substrate and support in the reaction systems; (2) the lower dissociation energy of H 2 activation, which is due to the altered electronic structure of the carbon substrate and the modulating activity of the sp 2 carbon and metal particles; [141] and (3) N doping in the carbon structure, which can be considered as a favorable anchor point or defect for enhanced particle nucleation and particle size reduction and improved the dispersion of metal NPs, as well as enhanced support‐active sites interactions [142] .…”