Zhangfeng Zhou

Cu/SiO2 Catalysts Prepared by the Sol-Gel Method for Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Abstract A series of Cu/SiO2 catalysts for the hydrogenation of dimethyl oxalate to ethylene glycol were prepared by the sol-gel method. Under optimized hydrogenation conditions, dimethyl oxalate conversion and ethylene glycol selectivity were found to reach 99.9% and 95.0%, respectively, upon varying the copper loading between 15% and 25%. The prepared catalysts were characterized by N2-physisorption, transmission electron microscopy, X-ray diffraction, H2-temperature-programmed reduction, N2O titration, and X-ray photoelectron spectroscopy. The results show that when the copper loading was increased under the same experimental conditions the factors that mostly affect the activities of the catalysts prepared by the sol-gel method are encapsulation and agglomeration. The encapsulation of silica is strong and it becomes the major factor when w(Cu) ≤ 10% while agglomeration among the copper species on the catalyst surface becomes more serious and is a major factor when w(Cu) > 10%. These two factors influence the surface structure, the morphology of the copper species, and the chemicals surroundings the catalysts and as a result the performance of the catalysts is affected too.

Canted antiferromagnetic behaviours in isostructural Co(II) and Ni(II) frameworks with helical lvt topology

The hydrothermal reaction of the versatile ligand 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (Hmtpo), and cobalt/nickel acetate afforded two isostructural Co(II) and Ni(II) frameworks [M(mtpo)2(H2O)]n (M = Co (1Co) or Ni (2Ni)). Both of them consist of heterochiral helical meshes fused together into a non-interpenetrated lvt topological network containing only planar four-coordinate nodes. The frameworks can be rationalized to a rare 6-c crs net if the water-donated hydrogen-bonds are considered. Two isomorphous complexes exhibit spin-canted antiferromagnetism, with the critical temperature Tc of ca. 3.0 K for 1Co and 19 K for 2Ni. The additional magnetic measurements (after the removal of guest molecules), IR, TGA and XRPD of the complexes were also discussed.

Inert Can Be Advantageous: Advisable Reconstruction and Application of Palladium Chloride for the Preferential Oxidation of the Hydrogen Impurity in Carbon Monoxide Streams

Preferential oxidation of the H2 impurity in CO streams is crucial for the catalytic conversion of CO into ethylene glycol. It is uncertain as to whether H2 can overthrow the dominance of CO and finally lead the reaction. Not only is this a typical research issue, but it is also extremely critical for practical applications. So far, no catalyst has shown selectivity higher than 50 % owing to competitive adsorption of CO. In this work, we report a PdClx‐based catalyst that can readily overcome the challenge mentioned above. Over this catalyst, the selectivity of H2 oxidation is promoted by more than 40 % relative to that over the conventional Pd/Al2O3 catalyst and reaches a value of 87 %. The turnover frequency of undesired CO oxidation is inhibited by at least one order of magnitude. We found that the reconstructed palladium chloride was highly selective to this reaction by facile inhibition of the adsorption and oxidation of CO.

Recent progress in improving the stability of copper-based catalysts for hydrogenation of carbon–oxygen bonds

The quickly increasing demand for sustainable energy and materials requires researchers to develop highly efficient and stable catalytic materials for the hydrogenation of carbon–oxygen bonds into chemicals and fuels. Cu-based catalysts have been attracting tremendous attention in gas-phase catalytic reactions, such as the water-gas shift, CO oxidation and NOx reduction reactions. In particular, the C–O bond hydrogenation reaction is an economical and environmentally friendly way to produce alcohols. However, the instability of Cu-based catalysts has become a great challenge for industrial application. The majority of publications discuss the instability of Cu-based catalysts for reactions involving the hydrogenation of dimethyl oxalate, methyl acetate, furfural, or CO2 to alcohols. This review briefly summarizes the roots of Cu-based catalyst deactivation and introduces five strategies for improving their stability, as well as the evolution of copper species during preparation and reaction and a novel Cu-based catalyst technology.