Zhihua Gao

The Dehydration of Methanol to Dimethyl Ether over a Novel Slurry Catalyst

Abstract A novel slurry catalyst for dehydration of methanol was prepared by complete liquid-phase technology. Its main innovative thought lies in preparing the slurry catalysts directly from solution. The catalysts were characterized using X-ray diffraction, Brunauer–Emmett–Teller, and NH3-TPD. It was found that the main crystal phase of slurry catalyst was boehmite AlO(OH). Also, it was observed that slurry catalyst had a high surface area and pore volume. Activity tests indicated that the slurry catalyst has shown better performance compared to the commercial γ-Al2O3: the highest methanol conversion was 84.4% at the temperature of 280°C, dimethyl ether selectivity nearly reached 100%. The catalyst showed a good stability during the long-term test of 500 h.

Ethanol Synthesis from Syngas Over CuZnX (X = Ti, Si, Al, Mg) Catalysts

The catalytic performance of ethanol synthesis from CO hydrogenation over CuZnX (X = Ti, Si, Al, Mg) catalysts prepared by complete liquid phase method are studied. Among these catalysts, CuZnTi catalyst has the best ethanol selectivity about 46.6%. Characterization results show that the interaction between Cu species and metal oxides is a key factor for ethanol synthesis from syngas, which is in accordance with our previous results. CuZnTi catalyst also has good repetitive performance.Graphical Abstract

The Synthesis and Catalytic Activity of Slurry Catalyst for Methanol Dehydration to Dimethyl Ether

Abstract A series of slurry catalysts for dehydration of methanol were prepared by liquid-phase technology, in which the main innovative thought lies in preparing the slurry catalysts directly from solution. The catalysts were characterized using X-ray diffraction, Brunauer–Emmett–Teller, and temperature programmed desorption of ammonia. It was found that the main crystal phase of slurry catalysts was AlOOH. Also, it was observed that slurry catalyst had a high surface area and pore volume. Activity tests indicated that the slurry catalysts have shown better performance than the γ-Al2O3: the highest methanol conversion was 84.4%, dimethyl ether selectivity nearly reached 100%. This catalyst showed a good stability during the reaction of 500 h.

A DFT study of the catalytic pyrolysis of benzaldehyde on ZnO, γ-Al2O3, and CaO models

AbstractThe catalytic pyrolysis pathways of carbonyl compounds in coal were systematically studied using density functional theory (DFT), with benzaldehyde (C6H5CHO) employed as a coal-based model compound and ZnO, γ-Al2O3, and CaO as catalysts. The results show that the products of both pyrolysis and catalytic pyrolysis are C6H6 and CO. However, the presence of any of the catalysts changes the reaction pathway and reduces the energy barrier, indicating that these catalysts promote C6H5CHO decomposition. Graphical abstractThe presence of catalysts changes the reaction pathway and the energy barrier decreases in the order Ea (no catalyst)> Ea (CaO)> Ea (γ-Al2O3)> Ea (ZnO), indicating that these catalysts promote C6H5CHO decomposition.

DME synthesis from methanol over hydrated γ-Al2O3(110) surface in slurry bed using continuum and atomistic models

The possible paths of dimethyl ether (DME) synthesis from methanol over hydrated γ-Al2O3(110) in vacuum and liquid paraffin have been investigated by using density functional theory (DFT). Over hydrated γ-Al2O3(110), the three possible paths of methanol dehydration to DME have been investigated by the DFT method in vacuum and liquid paraffin. DME synthesis from methanol is carried out along the same pathway 2CH3OH(g) + 2* → 2CH3OH* → 2CH3O* + 2H* → CH3OCH3* + H2O* in vacuum and liquid paraffin, and the step of highest energy barrier is the reaction of 2CH3O* → CH3OCH3* + O*. The energy barrier of the step in liquid paraffin is higher than that in vacuum by 0.33eV. The surface acid strength in liquid paraffin decreases over γ-Al2O3(110) surface comparing with vacuum, showing that stronger surface acid strength benefits to DME synthesis. Our result is in consistent with the experiment results.

Ethanol synthesis from syngas over Cu/Zn/Al-B catalysts: The promoting effect of boron

ABSTRACT Ethanol synthesis from syngas was studied over Cu/Zn/Al catalysts promoted with different B contents using the complete liquid-phase technology. It is found that ethanol selectivity is strongly influenced by B content. When the B content is 6.0 wt%, the ethanol selectivity is the highest (37.6%). The characterization results indicated that a suitable B promoter prevents the growth of copper particles, strengthens the interaction between Cu and Al or Zn species, increases the relative amount of Cu2O on the catalysts surface, and keeps the balance of Cu+–Cu°.

Effect of Polyethylene Glycol on Structure and Performance of CuZnAl Slurry Catalyst

CuZnAl precursor was prepared by coprecipitation sedimentation method and modified by addi- tion of polyethylene glycol (PEG600). Slurry catalyst was then obtained by heat-treatment using com- plete-liquid phase technology. The performance of the catalysts for the direct synthesis of dimethyl ether from syngas was evaluated in a slurry reactor. Characterization of the catalysts was carried out by powder X-ray diffraction, H2 temperature-programmed reduction, temperature-programmed desorption of ammonia and X-ray photoelectron spectrometry. The results indicated that PEG600 could effectively promote the re- duction of the copper species in catalysts and improve the Cu2O dispersion. The amount of acid and the acidic distribution of catalyst were also changed due to addition of PEG600. Moreover, marked influences were found on methanol synthesis and dehydration capability when PEG600 was added in different way. A significant increase of activity was achieved when the catalyst was prepared in the condition of adding 0.5 wt% PEG600 into the solution of copper nitrate and zinc nitrate. This was attributed to the stable Cu2O with small grain size formed during the heat-treatment process.

Studies on the structure and catalytic performance of Cu-Zn-Al catalyst prepared by liquid-phase preparation technology under different heat treatment atmosphere

Abstract Cu-Zn-Al slurry catalysts were prepared using a complete liquid-phase preparation technology under different heat treatment atmospheres. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscope, and N2 adsorption-desorption. Their application in the single-step synthesis of dimethyl ether from syngas was also investigated. The results indicate that the type of heat treatment atmosphere has an influence on the Cu species and the Cu0/Cu+ ratio on the catalyst surface. Moreover, the final Cu/Zn ratio on the catalyst surface is mainly dependent on the composition and reaction environment of the catalyst and less on the type of heat treatment atmosphere. The prepared catalysts can suppress sintering of active sites at high temperatures, and the type of heat treatment atmosphere mainly affects the capability of the catalyst for methanol synthesis. The catalysts perform best using N2 as the heat treatment atmosphere.