Mechanistic Insight into the Hydrodeoxygenation of Hydroquinone over Au/a-TiO₂ Catalyst

Abstract

The mechanism and kinetic features of hydrodeoxygenation of hydroquinone over the oxygen-defective anatase (a-TiO 2 ) supported gold (Au) catalyst were studied by density functional theory calculations. The investigation of reaction pathways and energetics identified that the conversion of hydroquinone over Au 10 /a-TiO 2 (001) went through several key reaction intermediates including benzoquinone, 1,4-cyclohexanediol, and cyclohexanol. The dehydrogenation of hydroquinone to benzoquinone intermediate occurred via H-transfer on both the TiO 2 surface and Au cluster. Subsequent hydrogenation of the C C bonds of benzoquinone mainly occurs from H*−Au sites, which has relatively low barriers, indicating the facile formation of ringsaturated species. The "1,4-cyclohexanediol" pathway dominates the overall reaction in hydroquinone conversion with favorable kinetic feature due to low barriers, leading to a large amount of cyclohexane in the product. The presence of oxygen vacancies on the a-TiO 2 (001) surface is critically important as active sites to facilitate the cleavage of C−O bond of intermediate species. The interface of Au−TiO 2 also plays an important role in stabilizing reaction intermediates and promoting the H transfer between Au cluster and the adsorbed species on the TiO 2 surface.

Tuning Strong Metal‐Support Interactions for Enhancing Direct Deoxygenation of Biomass‐Lignin Derived Phenolics

“…Combination of metal and reducible metal oxide (as support or promoter) has been generally shown higher DDO activity compared with bare metal on an inert support. [14,48] However, only few studies investigated the effect of SMSI degree on the DDO activity/selectivity. In this section, we analyze the approaches of tuning degree of SMSI and their consequences on the activity and selectivity for HDO of phenolics, with particular focus on DDO toward aromatics.…”

Understanding the prototype catalyst TiO2 surface with the help of density functional theory calculation

“…The red numbers represent activation barriers (eV), while the blue numbers are reaction energies (eV). 191 the possibility of generating a transient superoxo state of O 2 as a reaction intermediate. Actually, with a combination of experimental and theoretical research, Adachi et al 196 have shown that the charge on the oxygen species can be tuned by kelvin probe force spectroscopy (KPFS) charge manipulation in a systematic manner from 4e to 2e 2À ).…”

“…Conversion of hydroquinone through different pathways. The red numbers represent activation barriers (eV), while the blue numbers are reaction energies (eV) 191 …”

“…The spillover of H* from the Au cluster to the a‐TiO 2 (001) is facile. The mechanism for the hydrodeoxygenation of hydroquinone over the Au 10 supported oxygen‐defective anatase surface is investigated by Nie et al 191 It is found that the conversion of hydroquinone proceeds through several key reaction intermediates, including benzoquinone, 1,4‐cyclohexanediol, and cyclohexanol (Figure 19). The dehydrogenation of hydroquinone involves H‐transfer on both the TiO 2 surface and the Au cluster.…”

The Journal of Physical Chemistry C Virtual Special Issue on “Energy and Catalysis in China”

“…CO oxidation on RuO 2 (110) surfaces, 85 Pt nanocatalysts, 86 Cu/Rh bimetallic catalysts, 87 Ag clusters, 88 and Ru/RuO 2 interfaces 89 is discussed. Theoretical studies on other important reactions are also included: the HER on the VS 2 monolayer 90 or black phosphorus, 91 the electrochemical CO 2 reduction reaction on h-BN nanosheets, 92 photocatalytic CO 2 reduction on silver nanoclusters, 93 CO 2 dissociation on Cu clusters, 94 the methanol-to-olefins (MTO) process on different zeolites, 95 the ORR on the two-dimensional NiTe monolayer, 96 the nitrogen reduction reaction on Ru-or Fe-supported Nb 2 C MXene, 97 NO reduction by CO on Cu 2 O(110) and Pd 1 / Cu 2 O(110), 98 NO oxidation on different oxides, 99 methane steam reforming on Ni, Pt, and Pd, 100 dry reforming of methane on the Ni/Mo alloy, 101 the B 2 O 3 -catalyzed oxidative dehydrogenation of propane, 102 the hydrodeoxygenation of hydroquinone on Au/TiO 2 , 103 the hydrogenation of CO 2 to methanol over Pt 4 /In 2 O 3 , 104 syngas conversion to ketene on ZnCr 2 O 4 , 105 the structural and optoelectronic properties of ZnSe 1−x Te x photocatalysts, 106 bimetallic salen-complex-catalyzed epoxide hydration, 107 Rh-catalyzed formaldehyde hydroformylation, 108 the peroxidase and oxidase-like properties of nanoceria in biosystems, 109 the formation of polarons in TiO 2 , HfO 2 , and BiVO 4 , 110,111 and interfacial charge transfer in Li− O 2 batteries. 112 This VSI reflects the recent progress in the experimental and theoretical development of chemical energy in mainland China.…”