Haijun Zhao

A novel Cu–Mn/Ca–Zr catalyst for the synthesis of methyl formate from syngas

A novel catalyst comprised of Cu–Mn mixed oxides and CaO–ZrO2 solid base has contributed to a high-performance methyl formate (MF) synthesis from syngas in a slurry reactor. Cu–Mn mixed oxides and mesoporous CaO–ZrO2 solid base were prepared by complexing method and alcohothermal route, respectively, and they were characterized by N2 isotherm adsorption–desorption, XRD, SEM, TEM, XPS and CO2-TPD techniques. Under the optimum reaction conditions of 160 °C, 3 MPa, 3 : 7 for the ratio of methanol to N,N-dimethylformamide, 40 g L−1 Cu–Mn sample, and 30 g L−1 CaO–ZrO2 sample, a low CO conversion of 22.4% was obtained over Cu–Mn/Ca–Zr, whereas the MF selectivity of 82.3% was higher than that of the traditional catalyst (e.g. Cu-catalyst and NaOCH3), which was due to the synergism between Cu–Mn and CaO–ZrO2 samples.

Construction of Cu–Ce/graphene catalysts via a one-step hydrothermal method and their excellent CO catalytic oxidation performance

Cu–Ce/graphene catalysts show high dispersion of metal particles and excellent activity and stability for catalytic oxidation. In this study, a hydrothermal method was used to synthesize a series of bimetallic Cu–Ce/graphene catalysts, and the effects of the proportions of Cu and Ce on CO oxidation were investigated in detail. Indispensable characterizations such as XPS, XRD, TEM, BET, and H2-TPR were conducted to explore the effect of the Cu/Ce molar ratio and the metal valence on the activity and determine the structure–performance relationship. The results showed that bimetallic supported catalysts, such as 3Cu5Ce/graphene, 1Cu1Ce/graphene, and 5Cu3Ce/graphene, possessed significant catalytic activity. Especially, the 5Cu3Ce/graphene catalyst showed highest catalytic activity for CO oxidation, the T100 value was 132 °C, and the apparent activation energy was 68.03 kJ mol−1. Furthermore, the stability of the 5Cu3Ce/graphene catalyst was outstanding, which could be maintained for at least 12 h. Moreover, the CeO2 particles were well crystalline with the size 5–9 nm in these catalysts, and the CuO nanoparticles were well dispersed on CeO2 and graphene. Notably, the ratio of Cu/Ce in the catalyst was higher, the interaction between the Ce species and the graphene was stronger, and the Cu species were more easily reduced; this was beneficial for the oxidation of CO.

Promotion effect of oxygen-containing functional groups and Fe species on Pd@graphene for CO catalytic oxidation

In this paper, a Pd/reduced graphene oxide (Pd/RGO) catalyst was successfully synthesized by a chemical reduction method with hydrazine hydrate as a reducing agent. By controlling the amount of reducing agent, the Pd/RGO catalyst showed different surface Pd loadings and graphene interlayer spacings. The Pd/Fe@RGO catalyst was prepared by Pd supported on the Fe@RGO composite which was synthesized by a hydrothermal method. In the Pd/Fe@RGO catalyst, Pd0 species and Fe3+ species were the main active components. The addition of Fe species increased the interlayer spacing of graphene, the surface loading of Pd and the content of surface active oxygen. Thus, the Pd/Fe@RGO catalyst showed the highest catalytic activity for CO oxidation, and the T100 value was 90 °C and the apparent activation energy was 86.37 kJ mol−1. The superior catalyst at 50% conversion was stable for 510 min, and under moisture the catalyst was stable for only 300 min.

Ratio-controlled synthesis of phyllosilicate-like materials as precursors for highly efficient catalysis of the formyl group

The design and development of heterogeneous catalysts is very critical for the synthesis of various chemicals and fuels derived from superfluous biomass. The synthesis of biofuel 2-methylfuran typically derives from the conversion of the formyl group of biomass-derived furfural, because this process is very valuable in terms of the amelioration and remission of the environment and energy crisis. Herein, we designed a series of bifunctional catalysts formed in line with the spatial restriction strategy by anchoring copper nanoparticles (Cu NPs) on phyllosilicate-like structures to enhance copper dispersion and provide properly assembled Lewis acid sites to promote the hydrogenation and hydrogenolysis of the formyl group in furfural, and first applied them to the conversion of the formyl group with high efficiency. However, the modulation of the Cu–Si molar ratio is extremely critical to the possible reduction of metal consumption, full exploitation of the prerequisite metal sites and great improvement of activity. In this work, the catalyst with a Cu–Si molar ratio (actual value = 0.33) lower than that of the industrial catalyst (theoretical value = 1.0) exhibited higher yields of the intermediate furfuryl alcohol (yield = 83.4%) and the desired product 2-methylfuran (yield = 95.5%). More importantly, with the continuous increase of the Cu–Si molar ratio, it is discovered that Cu dispersion regularly decreased and the size of the Cu NPs sequentially increased, and the change of assembled Lewis acid sites surprisingly kept pace with the integrity of the layered structure, as revealed by a series of detailed characterization studies.