Construction of porous Cu/CeO2 catalyst with abundant interfacial sites for effective methanol steam reforming

Methanol is a promising hydrogen carrier for fuel cell vehicles (FCVs) via methanol steam reforming (MSR) reaction. Ceria supported copper catalyst has attracted extensive attentions due to the extraordinary oxygen storage capacity and abundant oxygen vacancies. Herein, we developed a colloidal solution combustion (CSC) method to synthesize a porous Cu/CeO2(CSC) catalyst. Compared with Cu/CeO2 catalysts prepared by other methods, the Cu/CeO2(CSC) catalyst possesses highly dispersed copper species and abundant Cu+-Ov-Ce3+ sites at the copper-ceria interface, contributing to methanol conversion of 66.3 %, CO2 selectivity of 99.2 %, and outstanding hydrogen production rate of 490 mmol gcat-1 h-1 under 250 °C. The linear correlation between TOF values and Cu+-Ov-Ce3+ sites amount indicates the vital role of Cu+-Ov-Ce3+ sites in MSR reaction, presenting efficient ability in activation of water. Subsequently, a deep understanding of CSC method is further presented. In addition to serving as a hard template, the colloidal silica also acts as disperser between nanoparticles, enhancing the copper-ceria interactions and facilitating the generation of Cu+-Ov-Ce3+ sites. This study offers an alternative approach to synthesize highly dispersed supported copper catalysts.

Method for Surface Characterization Using Solid-State Nuclear Magnetic Resonance Spectroscopy Demonstrated on Nanocrystalline ZnO:Al

Nanoscale zinc-oxide doped with aluminum ZnO:Al is studied by different techniques targeting surface changes induced by the conditions at which ZnO:Al is used as support material in the catalysis of methanol. While it is well established that a variety of 1H and 27Al resonances can be found by solid-state NMR for this material, it was not clear yet which signals are related to species located close to the surface of the material and which to species located in the bulk. To this end, a method is suggested that makes use of a paramagnetically impregnated material to suppress NMR signals close to the particle surface in the blind sphere around the paramagnetic metal atoms. It is shown that it is important to use conditions that guarantee a stable reference system relative to which it can be established whether the coating procedure is conserving the original structure or not. This method, called paramagnetically assisted surface peak assignment, helped to assign the 1H and 27Al NMR peaks to the bulk and the surface layer defined by the blind sphere of the paramagnetic atoms. The assignment results are further corroborated by the results from heteronuclear 27Al{1H} dipolar dephasing experiments, which indicate that the hydrogen atoms are preferentially located in the surface layer and not in the particle core.

Insights into the Modifying Effect of Ga on Cu-Based Catalysts for Hydrogenation of Hydroxypivalaldehyde to Neopentyl Glycol

Cu-based catalysts, modified by gallium addition via the stepwise co-precipitation method, were studied for the liquid phase hydrogenation of hydroxypivalaldehyde (HPA) to neopentyl glycol (NPG). Through physico-chemical techniques, the effects of gallium introduction on the Cu trimetallic catalyst performance and the reaction mechanism of HPA hydrogenation were discussed. The characterization results showed that gallium introduction can influence the dispersion, reduction, and distribution of active Cu species, as well as their reactivity. Herein, the catalyst with 2 wt% gallium addition exhibited excellent catalytic performance with HPA conversion rate and NPG selectivity of 93.5% and 95.5%, at a reaction pressure of 3 MPa, temperature of 110 °C, hydrogen-aldehyde ratio (molar ratio) 10:1, and liquid space-time at a speed of 8.4 h−1. The good performance could be attributed to gallium doping tending to dynamically tune the interaction between the components, increasing Cu dispersion and the distributions of Cu+ and Cu0 species on the catalyst surfaces.