Jinhua Fei

A novel catalyst for DME synthesis from CO hydrogenation: 1. Activity, structure and surface properties

Abstract The effect of manganese on the dispersion, reduction behavior and active states of surfaces of γ-Al 2 O 3 supported copper catalysts was investigated by X-ray powder diffraction (XRD), temperature-programmed reduction (TPR) and XPS technologies. The relationship between the area of metallic copper and the activity of dimethyl ether (DME) synthesis from CO/H 2 was also investigated. The catalytic activity over Cu-MnO x /γ-Al 2 O 3 catalyst for CO hydrogenation is higher than that of Cu/γ-Al 2 O 3 . The adding of manganese increases the dispersion of the supported copper oxide. For the CuO/γ-Al 2 O 3 catalyst, there are two reducible copper oxide species; α- and β-peaks are attributed to the reduction of highly dispersed copper oxide species and bulk CuO species, respectively. For the CuO-MnO x /γ-Al 2 O 3 catalyst, four reduction peaks are observed. The α-peak is attributed to the reduction of high dispersed copper oxide species; β-peak is ascribed to the reduction of bulk CuO; γ-peak is ascribed to the high-dispersed CuO interacting with Mn; and δ-peak is attributed to the reduction of the manganese oxide interacting with copper oxide. XPS results showed that Cu + mostly existed on the working surface of the Cu-Mn/γ-Al 2 O 3 catalysts. Cu promoted the catalytic activity with positive charge, which was formed by means of long path exchange function between Cu O Mn. These results indicate that there are synergistic interactions between the copper and manganese oxide, which are responsible for the high activity of CO hydrogenation.

Characteristics of the Decomposition of CO2 in a Dielectric Packed-Bed Plasma Reactor

The decomposition of CO2 in a dielectric packed-bed plasma reactor has been studied. It was found that the dielectric properties and morphology of packing dielectric pellets play important roles in the reaction due to their influence on the electron energy distribution in the plasma. The acid–base properties of the packing materials also affect the reaction through the chemisorption of CO2 on basic sites of the materials. Heterogeneous reactions on the solid surfaces of the dielectric materials also play a role in the reaction, which was also confirmed through the investigation of the influence of the discharge length on the reaction. The reverse reaction of CO2 decomposition, the oxidation of CO, was also investigated to further understand the role of dielectric materials in the plasma and their effect on plasma reactions. Both the decomposition of CO2 and the oxidation of CO in non-packed or dielectric packed reactors are first-ordered.

Influence of supports on catalytic behavior of nickel catalysts in carbon dioxide reforming of toluene as a model compound of tar from biomass gasification

A series of supported Ni catalysts including Ni/MgO, Ni/γ-Al2O3, Ni/α-Al2O3, Ni/SiO2 and Ni/ZrO2 was tested in CO2 reforming of toluene as a model compound of tar from biomass gasification in a fluidized bed reactor, and characterized by the means of temperature programmed reduction with hydrogen (H2-TPR), XRD, TEM and temperature programmed oxidation (TPO). Combining the characterization results with the performance tests, the activity of catalyst greatly depended on Ni particles size, and the stability was affected by the coke composition. Both of them (Ni particle size and coke composition) were closely related to the interaction between nickel and support which would determine the chemical environment where Ni inhabited. The best catalytic performance was observed on Ni/MgO due to the strong interaction between NiO and MgO via the formation of Ni-Mg-O solid solution, and the highest dispersion of Ni particle in the basic environment.

DME synthesis from carbon dioxide and hydrogen over Cu–Mo/HZSM-5

HZSM-5 supported copper–molybdenum oxide prepared by an impregnation method has been applied for the first time in the hydrogenation of CO2. The effect of the loading of Mo, the reaction temperature and the stability of hydrogenation of CO2 were investigated. The results indicate that adding a small amount of Mo (Mo/Cu = 1/2 wt) markedly enhances the catalytic activity. The highest DME selectivity was more than 70%. The change of species on the catalyst surface due to the addition of Mo was also investigated by in situ DRIFT.

Study of CO2 Hydrogenation to Methanol over Cu-V/γ-Al2O3 Catalyst

Abstract The effect of vanadium addition to Cu/γ-Al 2 O 3 catalyst used in the hydrogenation of CO 2 to produce methanol was studied. It was found that the catalytic performance of the Cu-based catalyst improved after V addition. The influence of reaction temperature, space velocity and the molar ratio of H 2 to CO 2 on the performance of 12%Cu-6%V/γ-Al 2 O 3 catalyst were also studied. The results indicated that the best conditions for reaction were as follows: 240 °C, 3600 h −1 and a molar ratio of H 2 to CO 2 of 3:1. The results of XRD and TPR characterization demonstrated that the addition of V enhanced the dispersion of the supported CuO species, which resulted in the enhanced catalytic performance of Cu-V/γ-Al 2 O 3 binary catalyst.

DME Synthesis From CO/H2 over Cu-Mn/Ă-Al2O3 Catalyst

A γ-alumina-supported copper-manganese oxide catalyst prepared by an impregnation method was used for DME synthesis from CO/H2 (syngas). The Cu-Mn/γ-Al2O3 catalyst exhibits high catalytic activity in CO hydrogenation. The effect of the loading amount of Cu, the ratio of n(Cu)/n(Mn) and the reaction conditions on the activity and selectivity to dimethyl ether (DME) from CO/H2 (syngas) were investigated. The activity was found to increase with increasing surface area of metallic copper to some extent, but it is not a linear relationship. This indicated that the catalytic activity depends on both the metallic copper area and the synergy between the copper and manganese oxide.

Synthesis of Dimethyl Ether via Methanol Dehydration over Combined Al2O3-HZSM-5 Solid Acids

Combined Al2O3-HZSM-5 solid acids were prepared and used for methanol dehydration to dimethyl ether (DME) in a fixed-bed reactor. The physicochemical properties of the combined solid acids were characterized by X-ray diffraction, field emission scanning electron microscopy, N2 adsorption, and NH3 temperature-programmed desorption. Al2O3 was highly dispersed in Al2O3-HZSM-5 after impregnation (Al2O3-HZSM-5-IM), while a layered Al2O3-covered HZSM-5 structure solid acid was synthesized via chemical precipitation (Al2O3-HZSM-5-CP). Both the combined Al2O3-HZSM-5 solid acids prepared by impregnation and chemical precipitation have a higher surface area and more meso- and macropores. The combined Al2O3-HZSM-5 solid acids exhibit higher methanol dehydration activity than pure Al2O3 and it possesses higher stability than pure HZSM-5 at a lower temperature (235 (C) and a higher LHSV (30 h−1). The stable DME productivities for Al2O3-HZSM-5-IM and Al2O3-HZSM-5-CP at 235 (C reached 12.7 and 13.5 g/(g·h), respectively.

Low-temperature methanol synthesis catalyzed over Cu/γ-Al2O3–TiO2 for CO2 hydrogenation

A titanium-modified γ-alumina-supported CuO catalyst has been prepared and used for methanol synthesis from CO2 hydrogenation. XRD and TPR were used to characterize the phase, reduction property and particle size of the reduced catalyst. The addition of Ti to the CuO/γ-Al2O3 catalyst made the copper in the catalyst exist in much smaller crystallites and exhibit an amorphous-like structure. The adding of Ti made the reduction peak shift toward lower temperature in comparison with the CuO/γ-Al2O3 catalyst. The effect of the addition of Ti and the reaction conditions on the activity and selectivity to methanol from CO2 hydrogenation were investigated. The activity was found to increase with increasing surface area of metallic copper, but it is not a linear relationship. This indicated that the catalytic activity of the catalysts depends on both the metallic copper area and the synergy between the copper and titanium dioxide. The effect of contact time on the relative selectivity (κ=SCH30H /SCO) and selectivity of methanol were also investigated. The results indicated that methanol was formed directly from the hydrogenation of CO2.

Effect of Calcination Temperature on Characteristics and Performance of Ni/MgO Catalyst for CO2 Reforming of Toluene

Abstract A Ni/MgO catalyst for CO 2 reforming of toluene was prepared by impregnating MgO with Ni(NO 3 ) 2 . During calcination, some of the NiO diffused into the MgO and formed a solid solution structure of NiO-MgO, which was analyzed by Raman spectroscopy. In the temperature-programmed reduction with hydrogen analysis, only a small part of the Ni species in the outermost layer was reduced to metallic Ni at 700 °C. The calcination temperature played a key role in determining the subsequent catalytic activity of Ni/MgO, consequently the catalyst calcined at 600 °C had the highest activity. This catalyst also had the highest surface concentration of reduced Ni, which probably accounted for its high activity. During the reforming tests, a small amount of coke was deposited on Ni/MgO catalyst. Polyaromatic compounds were observed by Raman spectroscopy. The coke was probably responsible for the activity loss of Ni/MgO.

Combination of CO2 reforming and partial oxidation of CH4 over Ni/Al2O3 catalysts using fluidized bed reactor

The effects of the Ni loading, total feed flow rate, prereduction temperature, reaction temperature and feed gas ratio for combination of CO2 reforming and partial oxidation of CH4 over Ni/Al2O3 were investigated using a fluidized bed reactor. Methane conversion to syngas was drastically enhanced using a fluidized bed reactor over Ni/Al2O3 catalyst calcined at high temperature. The fluidized bed and the fixed bed reactor were compared and a promoting mechanism of the fluidized bed reactor was proposed.