Search

A poly( N -vinyl-2-pyrrolidone) (PVP)-assisted wet impregnation method has been developed for preparing highly-dispersed supported Ni/SBA15-PVP (1/X) catalysts, in which 1/X indicates the molar ratio of PVP polymer to Ni. XRD and TEM results of as-prepared samples showed that PVP addition could dramatically promote the dispersion of NiO on SBA-15, with the n PVP /n Ni ratios in the range of 1/5000–1/1000. Whereas, severe sintering of NiO could be observed on Ni/SBA15-PVP (1/X) catalysts prepared with no PVP (1/X = 0), insufficient PVP (1/X = 1/7500) or superabundant PVP (1/X = 1/100). These catalysts were employed to catalyze the carbon dioxide reforming of methane (CRM) reaction, and the optimized Ni/SBA15-PVP (1/X) catalysts (1/X = 1/5000–1/1000) exhibited much better stability than others during the 25 h test. Besides, the role of PVP addition during the preparation process was illustrated detailedly with Raman, 1 H NMR, UV–vis, FTIR, and TPO characterizations. PVP would interact with Ni(NO 3 ) 2 . 6H 2 O to form complexes through the coordination of the oxygen and nitrogen atoms in the ring of PVP, with Ni 2+ , NO 3 − and H 2 O from the precursor during the drying step. Moreover, this complex could improve the stabilization, inhibit the redistribution and affect the decomposition behavior of the precursor, which ultimately led to a significantly improvement of the NiO dispersion on SBA-15 support. [ABSTRACT FROM AUTHOR]

Abstract: Sm2O3 doped ZrO2-based catalysts (Sm2O3–ZrO2 composite oxide) were prepared by co-precipitation and their physical properties (texture and structure) and chemical properties (acid–base and redox) were characterized with the methods of N2 adsorption–desorption isotherm, powder X-ray diffraction, Raman spectroscopy, NH3 and CO2 temperature programmed desorption and H2 temperature programmed reduction. The catalytic performances of the catalysts (activity and selectivities) were evaluated in the CO hydrogenation to isobutene and isobutane (isosynthesis) under the reaction conditions of 673K, 5.0MPa, and 650h−1. The relationship between the catalytic performance and the physical/chemical properties of Sm2O3–ZrO2 catalysts were also examined. The catalytic activity and selectivity of the Sm2O3–ZrO2 catalysts varied with Sm2O3 doping. The physical properties of the catalysts, such as cumulative pore volumes, average pore diameters and crystal sizes had some influences on the activity and selectivity in the isosynthesis. CO conversion increased with an increase in the amount of the acidic sites on the surface of Sm2O3–ZrO2 catalysts, while iso-C4 percentage in total hydrocarbons increased with an increase in the amount of the basic sites. The addition of Sm2O3 into ZrO2 enhanced the reducibility of Sm2O3–ZrO2 catalysts. The highest CO conversion (21.6%) and C4 selectivity (41.8%) were obtained over the catalyst that had a maximum amount of H2 consumptions (57.7μmolg−1) in the TPR measurement for Sm2O3–ZrO2 catalysts. A coordination of the acid–base properties and the redox property may play important role for the improvement of the catalytic performances of the isosynthesis. [Copyright &y& Elsevier]

Enhancement of methanol selectivity in the products of the direct selective oxidation of methane with CH4-O2-NO in a gas-phase reaction was examined using a Cu-ZnO/SiO2 catalyst. Two types of Cu-ZnO/SiO2 catalysts were prepared with different compositions: 3:7:90 (denoted as CZS-1) and 5:5:90 (CZS-2) as the weight percent ratios of CuO:ZnO:SiO2. Both CH3OH and CH2O were observed as C1-oxygenates at 550 °C in the gas-phase selective oxidation of CH4 in CH4-O2-NO without a catalyst, but then only CH3OH was observed in the presence of the CZS-1, in addition to the direct gas-phase selective oxidation of methane. The catalyst temperature was 250 °C and the reaction pressure was 0.4 MPa. CH3OH, CO and CO2 selectivities increased and CH2O selectivity decreased in the presence of the Cu-ZnO/SiO2, in comparison to the values in the absence of the catalyst. We, therefore, suggested that three reactions: i.e. the hydrogenation reaction of CH2O, the dissociation reaction of CH2O, and the WGSR, progressed simultaneously on the Cu-ZnO/SiO2 catalyst in CH4-O2-NO.Since the selectivity of CH3OH did not vary during the variation of reaction temperatures from 150 °C up to 350 °C over the Cu-ZnO/SiO2 catalyst, we assumed that SiO2 was a favorable support to enhance the selectivity of CH3OH in a wider catalyst temperature region. [Copyright &y& Elsevier]

Gas phase partial oxidation of methane to methanol has been carried out in a specially designed reactor. A comparatively high yield of methanol (ca. 7–8%, methanol selectivity of 60% at methane conversion 13%) was obtained over a quite wide temperature range of more than 40 °C at 5.0 MPa and CH4/O2/N2=100/10/10 (ml/min). The effects of the total flow rate, CH4/O2 ratio and pressure were examined and the superiority of the new reactor is discussed. [Copyright &y& Elsevier]

The trans-esterification of glycerol and dimethyl carbonate (DMC) for the synthesis of glycerol carbonate was investigated over a series of Li-La 2 O 3 catalysts with different Li contents under mild reaction conditions. Li-La 2 O 3 catalysts were prepared by simple precipitation and impregnation methods, and characterized using ICP, XRD, BET, XPS, CO 2 -TPD and TEM techniques. It was found that the basicity of La 2 O 3 was obviously changed and the interaction between Li and La 2 O 3 occurred after doping Li component, and the catalytic activity of Li-La 2 O 3 was highly relevant to the strength and content of basic sites on the catalysts. Li doping influenced the crystal phase growth of La 2 O 3 , and also changed the exposed crystal planes of the Li-La 2 O 3 catalysts. The highest catalytic performance was obtained over 3.50Li-La 2 O 3 catalyst calcined at 600 °C for 5 h. The glycerol conversion of 94.4% and glycerol carbonate selectivity of 92.1% were obtained over this catalyst under the proper reaction conditions of 85 °C, 3 h, and the molar ratio of glycerol and DMC being 1/3 with using 0.1 g 3.50Li-La 2 O 3 catalyst. [ABSTRACT FROM AUTHOR]

Abstract: RhCl3 was immobilized to diphenylphosphinopropyl (–PrPPh2)-modified mesoporous silica SBA-15 through a multi-step-assembly process. The prepared catalyst was characterized with reference to bulky and surface properties by X-ray diffraction (XRD), infrared spectroscopy (FT-IR), isothermal nitrogen sorption analysis and X-ray photoelectron spectroscopy (XPS). The metal content was determined by inductive coupling plasma-atomic emission spectroscopy (ICP-AES). The prepared rhodium-immobilized catalyst was employed in hydroformylation of several higher olefins of different lengths (C6, C8, and C10), different Csitions (terminal or internal) or different structures (linear or branched). The substrate influences on the activity and recycling stability of the immobilized catalyst were investigated and are discussed. Shorter linear olefin substrates were more easily activated with higher catalyst specific activity, while the catalyst showed recycling stability in hydroformylation of longer and branched olefin substrates. For comparison, PPh3 was externally added to immobilize RhCl3 to –PrPPh2-modified SBA-15. The immobilized catalyst so prepared showed a more flexible immobilizing structure and revealed a promoted turnover number of substrates. [Copyright &y& Elsevier]

Pd-Re/SBA-15 catalysts with different Pd precursors were prepared by the impregnation method. N 2 adsorption-desorption, XRD, H 2 -TPR, TEM and NH 3 -TPD were used to characterize the physical and chemical properties of the catalysts. Pd-Re catalysts with different precursors showed different activities in the reaction of glycerol hydrogenolysis. 5Pd-5Re/SBA-15 with PdCl 2 as Pd precursor had higher activity than those with Pd(NO 3 ) 2 and Pd(OAc) 2 as precursors. The existence of Cl could affect the particle sizes, reduction behaviors and the acid properties of Pd-Re catalysts. [ABSTRACT FROM AUTHOR]

The synthesis of glycerol carbonylation with CO 2 to glycerol carbonate over CeO 2 catalyst was investigated. CeO 2 with different morphologies was prepared by traditional precipitation (TP), hydrothermal (TH) and citrate sol-gel (SG) methods, and the reaction of glycerol with CO 2 was carried out in the presence of a dehydrating agent and solvent. The effect of preparation methods of CeO 2 and reaction parameters on the activity and selectivity of the catalysts were examined. The structures, morphologies and surface properties of the catalysts were characterized by XRD, TEM, BET, CO 2 -TPD, H 2 -TPR, Raman and XPS. CeO 2 exhibited high catalytic activity for the formation of glycerol carbonate under mild reaction conditions. The carbonylation of glycerol was influenced by the redox property of CeO 2 . The effects of different types of dehydrating agent and solvent were also studied. The dehydrating agent (2-cyanopyridine) and solvent (Dimethyl Formamide(DMF)) contributed to the increase of glycerol conversion and the yield of glycerol carbonate. The yield of glycerol carbonate could reach as high as 78.9%, and the catalysts could be easily regenerated by calcination at 400 °C for 5 h without loss of activity after 5 recycling times. The proper reaction conditions were 150 °C, 4 MPa and 5 h. [ABSTRACT FROM AUTHOR]

Highlights: [•] ·Ru catalysts with HZSM5(X) were used during glycerol hydrogenolysis. [•] ·As the acid amount increased, the glycerol conversion and CH4 selectivity increased. [•] ·The acid amount and acid strength of HZSM5(X) affected the C C bond cleavage. [•] ·Loading Ru on HZSM5(X) could modulate the acidity and decrease CH4 selectivity. [ABSTRACT FROM AUTHOR]