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Cu/Zn/Al/Zr catalysts containing Cu in three valence states (Cu2+, Cu+and Cu0) were prepared using a liquid reduction method and subsequently calcined at different temperatures. The effects of the calcination temperature on the catalyst structure, interactions among components, reducibility and dispersion of Cu species, surface properties and exposed Cu surface area were systematically investigated. These materials were also applied to the synthesis of methanol via the hydrogenation of CO2. The results show that a large exposed Cu surface area promotes catalytic CO2conversion and that there is a close correlation between the Cu+/Cu0ratio and the selectivity for methanol. A calcination temperature of 573 K was found to produce a Cu/Zn/Al/Zr catalyst exhibiting the maximum activity during the synthesis of methanol.

A new preparation method for MoO3–SnO2catalysts precipitated by HNO3was developed to selectively synthesize industrially useful chemicals formaldehyde and methyl formate viaoxidation of environmentally friendly feedstock dimethyl ether. By adjusting the structure of MoO3–SnO2, the selectivity to formaldehyde and methyl formate can reach as high as 95.0% and 82.4%, respectively, under different conditions. The conclusion has been drawn, based on the experimental results, that the formation of tetrahedral molybdenum oxide species and SnMoO4species favors the reaction of dimethyl ether to formaldehyde, and that the formation of MoOxdomains favors the direct oxidation reaction of dimethyl ether to formaldehyde. The XRD and Raman results suggest that the formation of tetrahedral molybdenum oxide species has a positive correlation with the high selectivity to formaldehyde and indicates that the formation of the MoOxdomains favors the high selectivity to methyl formate. The XPS results of the MoO3–SnO2catalysts with different SnO2contents demonstrate that formaldehyde is not readily desorbed from Mo1Sn2 and Mo1Sn3 because the electron-poor Mo cations of the domains supported on the surface of the catalysts strengthen their affinity for binding electron-donating dimethyl ether-derived intermediates and formaldehyde, which favors the subsequent reaction of formaldehyde to methyl formate. These interesting findings reveal that tetrahedral molybdenum oxide species and MoOxdomains play an important role in the selective oxidation of dimethyl ether to formaldehyde and methyl formate, and give insight into the rational design of the MoO3–SnO2catalyst structure for dimethyl ether oxidation in future studies.

The hydrothermal synthesis method was adopted to prepare a highly active Ga2O3–Al2O3catalyst (GA-HS), which displayed superior catalytic performance for dehydrogenation of propane to propylene in the presence of CO2(DHP-CO2). The highest propane conversion on GA-HS was 35.2%, which was much higher than that from the catalysts prepared using the grind-mixture method (8.7%) or coprecipitation method (26.2%). Moreover, propylene selectivity over the GA-HS catalyst was higher than that over the other catalysts in a period of 9 h of reaction. These catalysts were characterized by N2physical adsorption, ICP-AES, XRD, TGA, TEM, SEM, DRIFT, Py-FTIR, NH3-TPD, XPS, 27Al MAS NMR and 71Ga MAS NMR techniques. The characterization data indicated that the hydrothermal treatment increased the surface area, expanded the pore size and promoted the formation of more tetrahedral Ga ions and the generation of more medium-strong Lewis acid sites. Furthermore, this catalyst mainly displayed an amorphous sponge-like morphology as well as a new morphology whereby some pieces were covered with amorphous nanoparticles. The superior activity of GA-HS was attributed to the higher surface area of this catalyst and the larger amount of tetrahedral Ga ions (Ga3+and probably Gaδ+δ< 2) related to the medium-strong Lewis acid sites.

To improve the selectivity of 1,2-propandiol (PDO) by modifying the structure and morphology of the MoO3/SnO2catalyst, orthorhombic (α), monoclinic (β) and hexagonal (h) MoO3crystalline phases were prepared to investigate the rational design requirements of the MoO3–SnO2structure that are beneficial for the reaction of glycol dimethyl ether (DMET) to PDO. With an increase in the reaction temperature, the highest PDO selectivity of the oxidation reaction of glycol dimethyl ether to 1,2-propandiol was always obtained over the h-MoO3–SnO2catalyst and the lowest PDO selectivity was always obtained over the β-MoO3–SnO2catalyst. The MoO3bulk structure, the interaction between SnO2and MoO3and the surface properties of these three catalysts could account for this distinctive difference. Hexagonal MoO3is dispersed more homogeneously over the h-MoO3–SnO2catalyst due to the hexagonal crystalline tunnel structure existing in the h-MoO3–SnO2catalyst, and the weak interaction between MoO3and SnO2; besides, the more hydrated surface of the h-MoO3–SnO2catalyst can lead to more Brønsted acid sites being present on the catalyst surface and favor the dissociation of the C–O bond in DMET and association of the C–C bond to form PDO with the assistance of the redox and basic sites, which can explain why the highest PDO was obtained over the h-MoO3–SnO2catalyst. The lattice strain and oxygen vacancies in the β-MoO3–SnO2catalyst, induced by the substitution of Sn4+ions with the smaller sized Mo6+ions, enhance the oxidation ability of the β-MoO3–SnO2catalyst, and consequently more CH3O· can be formed and transformed to formaldehyde (FA) and methyl formate (MF), which can explain why the total selectivity of FA and MF was highest while the selectivity of PDO was lowest over the β-MoO3–SnO2catalyst at the same time. These findings are pretty significant for further investigation of the rational design of the MoO3–SnO2catalyst structure, applied to the conversion of DMET to PDO.

A new and efficient Ti(SO4)2-modified carbon nano-tube (CNTs) catalyst was designed and prepared for the selective oxidation of dimethyl ether (DME). The modification effects of Ti(SO4)2on the catalytic performance of CNTs were examined in a continuous flow-type fixed-bed reactor. The influences of SO42−content, calcination temperature and different feedstocks on DME selective oxidation were further investigated. It is found that dimethoxy dimethyl ether (DMM2) selectivity in the product was significantly improved up to 89.4% from 6.1% when 40% SO42−was used to modify the CNTs, and more importantly, there was no COxproduction in the reaction. The SO42−content and calcination temperature obviously affected the distribution and existing form of sulfate species and further influenced the acid and redox functions of the Ti(SO4)2/CNTs catalyst. The 40% SO42−/CNTs catalyst calcined at 240 °C exhibited the highest selectivity to DMM2. The structure, surface properties and morphology of the catalysts were deeply characterized by XRD, NH3-TPD, BET, XPS, H2-TPR-MS, TEM, TEM-EDS, O2-TPD-MS and DME-TPSR-MS. The modification of Ti(SO4)2not only increased the amount of weak acid sites, but also enhanced the redox properties of CNTs to activate O2over the defect sites of CNTs. The formation pathway of DMM2from DME oxidation was proposed and dimethoxymethane (DMM) could be the intermediate for DME oxidation to DMM2. The present CNTs modified by Ti(SO4)2with excellent catalytic performance can replace noble metal oxide catalysts and may be potential alternatives to conventional catalysts for DME selective oxidation to diesel oxygenate additives.

MgAl hydrotalcite synthesized via co-precipitation method from magnesium and aluminum nitrates was calcined to produce Mg 4 AlO 5.5 mixed oxides. The oxides were modified by introducing LiNO 3 and applied to the synthesis of glycerol carbonate from glycerol and dimethyl carbonate. The research results indicated that LiNO 3 /Mg 4 AlO 5.5 was an efficient catalyst for the synthesis of glycerol carbonate. The full conversion of glycerol and 96.28% yield of glycerol carbonate were obtained after reacting at 80 °C for 1.5 h in the presence of LiNO 3 /Mg 4 AlO 5.5 . The structure and properties of the catalysts were studied by means of XRD, TGA, BET, CO 2 -TPD and Hammett indicator method. It was found that the basic strength and the basicity of the catalysts were enhanced after addition of LiNO 3 . Over Mg 4 AlO 5.5 oxides, LiNO 3 was easily converted to LiAlO 2 which constituted new strong basic sites. Too high basic strength and basicity of catalysts may improve the conversion of glycerol at the cost of GC selectivity reduction. [ABSTRACT FROM AUTHOR]

A simple method for the preparation of a Ga/ZSM-5 catalyst for propane aromatization was established by formic acid impregnation and in situtreatment. The catalyst prepared by this novel method showed remarkably superior activity of propane aromatization. Under the conditions T= 540 °C, P= 100 kPa, WHSV = 6000 ml g−1·h−1and with a N2/C3H8molar ratio of 2, the highest propane conversion and selectivity to BTX (benzene, toluene and xylene) achieved on H–Ga/SNSA catalyst was 53.6% and 58.0%, respectively, much higher than that of the catalyst prepared using the traditional impregnation method (38.8% and 48.2%). The catalysts were characterized by nitrogen physical adsorption, ICP-AES, DRIFT, py-FTIR, NH3-TPD, H2-TPR, XPS and 27Al MAS NMR techniques. The characterization data indicated that this facile methodology enhanced the dispersion of the Ga species and promoted the formation of highly dispersed (GaO)+species, which could exchange with the acidic protons (Brønsted acid sites) of the zeolite framework, contributing to the strong Lewis acidity. The super catalytic behavior was attributed to the synergistic effect between the strong Lewis acid sites generated by the (GaO)+species and the Brønsted acid sites.

Abstract: The promotional effects of Sm2O3 on Mn-H4SiW12O40/SiO2 for dimethyl ether (DME) direct-oxidation to dimethoxymethane (DMM) were investigated. The results showed that Sm2O3 introduction could significantly improve the activity of Mn-H4SiW12O40/SiO2 for DMM formation, and DMM selectivity was remarkably increased from 36.3% to 60.3% when the Sm2O3 content was 1%. The catalysts were characterized by ICP-AES, XRD, NH3-TPD, Pyridine-IR and XPS. The Sm2O3 introduction enhanced the number of Lewis acid sites and weak acid sites and also increased the amount of Mn4+ species of Mn-H4SiW12O40/SiO2, which is favorable for the formation of DMM. [Copyright &y& Elsevier]

Abstract: The conversion of syngas to aromatics via dimethyl ether was investigated over MnCl2 modified HZSM-5 zeolites. The results demonstrated that 2%MnCl2 modified HZSM-5 (SiO2/Al2O3 =38) exhibited higher p-xylene selectivity than other catalysts and further decreased 1,2,4,5-tetramethylbenzene selectivity. The CO conversion was obviously increased after 5%MnCl2 modification to HZSM-5. The catalysts were characterized by XRD, BET, XPS, FT-IR, NH3-TPD, SEM, element analysis and O2-TPO. The loading amount of MnCl2 affected the adsorption and reaction of DME molecules on zeolites. Appropriate amount of MnCl2 introduction could adjust the acidity and pore volume of HZSM-5 to increase p-xylene selectivity and CO conversion. [Copyright &y& Elsevier]

Abstract: Fe–Mn–V–K catalysts for the synthesis of light olefins from CO hydrogenation were prepared by a specially controlled degradation method. The effect of the V content on the structure and the catalytic performance of the catalysts were investigated in a continuously stirred tank slurry reactor. Mössbauer spectra (MES) results show that the incorporation of V with appropriate contents can improve the dispersion of the α-Fe2O3 phase. CO hydrogenation results indicate that a small addition of V can improve the product distribution. The addition can also increase the selectivity to light olefins by inhibiting the secondary hydrogenation reaction of the initial olefin. The best catalytic performance was obtained at the Fe/Mn/V molar ratio of 3/1/0.2. The total C2–C4 content in all hydrocarbons and O/P in the C2–C4 fraction were 49.15wt% and 3.95, respectively. [Copyright &y& Elsevier]

Herein, we successfully synthesized well crystallized La0.7Sr0.3CoO3perovskite nanoparticles confined in the mesopores of a SiO2support. This perovskite exhibited extremely high NOxadsorbability for lean-burn exhausts, as well as improved stability in reducing atmospheres.