Direct Synthesis of Hydrogen and Dimethoxylmethane from Methanol on Copper/Silica Catalysts with Optimal Cu⁺/Cu⁰ Sites

Abstract

Hydrogen is an important sustainable resource, and here we report a catalytic route for the direct production of hydrogen (with a purity of 95 %) and dimethoxylmethane (DMM) from supercritical methanol over a Cu/SiO2 catalyst prepared by deposition–precipitation with ammonia (DPA) at 240°C in a one‐pot process. The procedure starts with methanol dehydrogenation to hydrogen and formaldehyde at the interface of the Cu2O⋅SiO2–Cu0 particle mixture, and subsequently, the formaldehyde intermediate condenses with substantial methanol to form DMM in the liquid phase. The Cu0, CuO, and chrysocolla species are inactive for hydrogen generation from methanol, and the intrinsic active species for methanol decomposition is the Cu2O⋅SiO2–Cu0 nanoparticle interface, which is produced from the hydrogen reduction of Cu2Si2O5(OH)2 or from the methanol reduction of Cu−O−Si moieties. A correlation between the structure and activity on reduced Cu/SiO2 (DPA) suggested that only Cu0 was not active, but the combined Cu0 and Cu+ sites with interfaces on SiO2 with an optimal Cu+/Cu0 ratio of 1.56 were highly active for methanol dehydrogenation and subsequent condensation steps. The developed new catalytic system offers a facile and atom‐economical way to generate pure hydrogen (almost CO free) from liquid methanol that can be used in fuel cell and hydrogen‐involved biomass reactions.

Control of metal-support interactions in heterogeneous catalysts to enhance activity and selectivity

“…Copper phyllosilicates have been employed as precursor for the formation of silica-supported metal nanoparticles on reduction in H 2 , leading to high Cu loadings (~40-50 wt%) with uniform distribution and particle size. The role of the generated Cu-SiO 2 interface in these materials has been exploited, for example, in the decomposition of methanol to hydrogen and dimethoxymethane in the liquid phase 143 , where Cu + and Cu-O-Si moieties were necessary for the activity and high selectivity of the catalyst. The copper-silica interface (Cu-O-SiO x ) was recently further optimized by use of a mesoporous silica layer coating the copper phyllosilicate prior H 2 activation 144 (Fig.…”

Converting waste PET plastics into automobile fuel and antifreeze components

“…Unlike the HT and DPA methods, the Cu species of the catalyst prepared by the IM and DPU methods generated Cu 0 species after being completely reduced (Figure S2). In previous work [20][21][22] , it was proven that a mixture of Cu 2 O and Cu was the active site for methanol dehydrogenation. This could explain the low activity of Cu/SiO 2 (IM) and Cu/SiO 2 (DPU) to provide the required H 2 for DMT hydrodeoxygenation reactions.…”

Highly Selective Silica‐supported Copper Catalysts Derived from Copper Phyllosilicates in the Hydrogenation of Adipic Acid to 1,6‐hexanediol

“…It should be noted that Cu/SiO 2 ‐red showed considerable TOF value, even though it contained negligible amounts of Cu + species. The noticeable TOF value of Cu/SiO 2 ‐red implied that the C=O bond of AA can be activated not only by Cu + −Cu 0 pairs, but also by interfaces of adjacent Cu 0 and Cu 2 O …”