Zihui Xiao

Conversion of highly concentrated cellulose to 1,2-propanediol and ethylene glycol over highly efficient CuCr catalysts

Direct hydrogenolysis of highly concentrated cellulose (up to 15 wt%) into 1,2-propanediol and ethylene glycol without the formation of coke-like precipitates could be performed over CuCr catalysts. Addition of Ca(OH)2 results in a significant increase in the EG yield.

A non-alkoxide sol–gel route to highly active and selective Cu–Cr catalysts for glycerol conversion

A non-alkoxide sol–gel route to highly active and selective Cu–Cr catalysts for glycerol conversion is presented. The addition of propylene oxide to ethanol solutions of Cr(NO3)3·9H2O and Cu(NO3)2·3H2O resulted in the formation of transparent Cu–Cr gels. The resulting gels were converted to the Cu–Cr catalysts by atmospheric drying and calcination. The Cu–Cr catalysts are characterized by X-ray diffraction (XRD), N2 physisorption, temperature-programmed reduction (TPR), and transmission electron microscopy (TEM). The results show that the surface area of the Cu–Cr catalyst is adjusted by the hydrolysis conditions, Cu/Cr molar ratio, and treatment conditions (such as gas atmosphere and final temperature). For the sample with Cu/Cr = 0.5, the surface area of Cu–Cr xerogel can reach 94 m2/g and decreased to only 31 m2/g after calcination at 500 °C. The catalysts show significant catalytic activity and selectivity in glycerol conversion, i.e. above 52% conversion of glycerol and above 88% selectivity to 1,2-propanediol at 210 °C and 4.15 MPa H2 pressure. CuCr2O4 supported Cu catalysts are much more active than Cr2O3 supported Cu catalysts. This indicates a strong interaction between Cu and CuCr2O4 that is significantly improving the effectiveness of the catalyst for glycerol conversion.

Preparation, structure and catalytic properties of magnetically separable Cu-Fe catalysts for glycerol hydrogenolysis

The Cu–Fe catalysts with stoichiometric proportion (Cu/Fe molar ratio was 0.5) were prepared by an epoxide assisted route. The structural properties of Cu–Fe catalysts were determined by X-ray diffraction (XRD), and Mossbauer spectroscopy measurements. These results indicated that a crystalline phase transformation from c-CuFe2O4 to t-CuFe2O4 occurred when elevating the calcination temperature from 500 to 600 °C. The M–H plots exhibited that all Cu–Fe catalysts had ferromagnetic nature and the saturation magnetization values monotonously increased with increasing calcination temperature irrespective of the phases composition. The significant superparamagnetic behavior was observed in the results of magnetic and Mossbauer spectroscopy measurements. The H2 temperature-programmed reduction (H2-TPR) was also conducted for examining the reducibility of Cu–Fe catalysts. The catalytic performance of Cu–Fe catalysts was examined for the hydrogenolysis reaction of glycerol. It is found that the formation of spinel CuFe2O4 greatly enhances the hydrogenolysis activity. The highest glycerol conversion (47%) was obtained over CuFe-500 catalyst, while the selectivity of 1,2-propanediol was maintained at about 92% for all catalysts.

Controlled preparation and characterization of supported CuCr2O4 catalysts for hydrogenolysis of highly concentrated glycerol

Supported Cu–Cr catalysts were prepared by a non-alkoxide sol–gel route, and characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), H2-temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) measurement. Their structures were significantly tuned by the Cu–Cr molar ratio. CuCr2O4, CuCr2O4–CuO and CuCr2O4–Cr2O3 structures were confirmed in CuCr(0.5), CuCr(4) and CuCr(0.25) catalysts, respectively. A direct interaction between CuCr2O4 and CuO or Cr2O3 in CuCr(4) and CuCr(0.25) catalyst was observed by the H2-TPR and XPS results. The catalytic performance of Cu–Cr catalysts with various structures was examined by hydrogenolysis reaction of high concentrated glycerol. Under mild conditions (2.0 MPa and 130 °C) and high concentration (100 wt%), the maximum conversion (52%) was obtained over the CuCr(0.5) catalyst, while the CuCr(4) catalyst gave the highest selectivity of 1,2-PD (up to 100%). This finding will result in the production of less waste water and lower energy consumption in the following separation steps during glycerol hydrogenolysis.

Hydrogenolysis of glycerol over HY zeolite supported Ru catalysts

Abstract An enhanced active and selective catalyst consisting of ruthenium supported on dealuminated HY zeolite has been prepared by a wet impregnation method. It was found that BET surface area of Ru/HY catalysts significantly increases after HCl treatment. This treatment also increases the concentration of strong acid sites in the catalyst. The hydrogenolysis of glycerol over 5 wt% Ru/HY catalyst was investigated at 190–220 °C, an initial H2 pressure of 3–6 MPa, and in 20 wt% glycerol aqueous solution. The results indicate that HCl treated Ru/HY catalyst shows higher activity compared with the untreated Ru/HY catalyst, and that the glycerol hydrogenolysis efficiency is influenced by the porosity and acidity of the support. A selectivity to 1,2-PDO of 81.3% at a glycerol conversion of 60.1% under 3 MPa H2 pressure and 220 °C for 10 h was achieved over the modified Ru/HY catalyst with a 1.0 mol/L HCl treatment. It has also been shown that a longer reaction time, a higher temperature and a higher H2 pressure have the positive effects on the glycerol hydrogenolysis efficiency of the enhanced Ru/HY.

In situ synthesis of Au–Pd bimetallic nanoparticles on amine-functionalized SiO2 for the aqueous-phase hydrodechlorination of chlorobenzene

Highly dispersed Au–Pd nanoparticles (NPs) with an average size of ∼3.0 nm were synthesized by in situ reduction of HAuCl4 and PdCl2 on an amine-functionalized SiO2 support. The structural and electronic properties of the Au–Pd NPs were investigated systematically using STEM-EDX, XRD, UV-vis and XPS spectroscopy. It is demonstrated that the composition of the Au–Pd NPs can be tuned by varying the ratio of Au- to Pd-containing salt in solution. In the aqueous-phase hydrodechlorination of chlorobenzene, the Au–Pd NPs showed a much higher activity and chlorine resistance than the monometallic Au and Pd counterparts. The effects of base and solvent on the activity over the supported Au–Pd NPs were also investigated.