Methanation of syngas over coral reef-like Ni/Al_2O_3 catalysts

Coral reef-like Ni/Al2O3 catalysts were prepared by co-precipitation of nickel acetate and aluminium nitrate with sodium carbonate aqueous solution in the medium of ethylene glycolye.Methanation of syngas was carried out over coral reef-like Ni/Al2O3 catalysts in a continuous flow type fixed-bed reactor.The structure and properties of the fresh and used catalysts were studied by SEM,N2 adsorption-desorption,XRD,H2-TPR,O2-TPO,TG and ICP-AES techniques.The results showed that the coral reef-like Ni/Al2O3 catalysts exhibited better activity than the conventional Ni/Al2O3-H2O catalysts.The activities of coral reef-like catalysts were in the order of Ni/Al2O3-673Ni/Al2O3-573Ni/Al2O3- 473Ni/Al2O3-773.Ni/Al2O3-673-EG catalyst showed not only good activity and improved stability but also superior resistance to carbon deposition,sintering,and Ni loss.Under the reaction conditions of CO/H2（molar ratio）=1：3,593 K,atmospheric pressure and a GHSV of 2500 h-1,CH4 selectivity was 84.7%,and the CO conversion reached 98.2%.

CO_2 hydrogenation to methanol over Cu/Zn/Al/Zr catalysts prepared by liquid reduction

Cu/Zn/Al/Zr catalysts containing Cu in three valence states(Cu2+,Cu+and Cu0)were prepared usinga liquid reduction method and subsequently calcined at different temperatures.The effects of thecalcination temperature on the catalyst structure,interactions among components,reducibility anddispersion 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 ofCO2.The results show that a large exposed Cu surface area promotes catalytic CO2conversion andthat there is a close correlation between the Cu+/Cu0ratio and the selectivity for methanol.A calcinationtemperature of573K was found to produce a Cu/Zn/Al/Zr catalyst exhibiting the maximumactivity during the synthesis of methanol.

Catalytic Oxidation of Dimethyl Ether to Dimethoxymethane over Cs Modified H_3PW_(12)O_(40)/SiO_2 Catalysts

The attractive utilization route for one-step catalytic oxidation of dimethyl ether to dimethoxymethane was successfully carried out over the H3PW12O40（40%）/SiO2 catalyst, modified by Cs, K, Ni, and V. The Cs modification of H3PW12O40（40%）/SiO2 gave the most promising result of 20% dimethyl ether conversion and 34.8% dimethoxymethane selectivity. Dimethoxymethane could be synthe- sized via methoxy groups decomposed from dimethyl ether through the synergistic effect between the acid sites and the redox sites of Cs modified H3PW12O40（40%）/SiO2.

Tuning the crystallite size of monoclinic ZrO_(2) to reveal critical roles of surface defects on m–ZrO_(2) catalyst for direct synthesis of isobutene from syngas

The effects of crystallite size on the physicochemical properties and surface defects of pure monoclinic ZrO_(2) catalysts for isobutene synthesis were studied.We prepared a series of monoclinic ZrO_(2) catalysts with different crystallite size by changing calcination temperature and evaluated their catalytic performance for isobutene synthesis from syngas.ZrO_(2) with small crystalline size showed higher CO conversion and isobutene selectivity,while samples with large crystalline size preferred to form dimethyl ether(DME)instead of hydrocarbons,much less to isobutene.Oxygen defects(ODefects)analyzed by X-ray photoelectron spectroscopy(XPS)provided evidence that more ODefectsoccupied on the surface of ZrO_(2) catalysts with smaller crystalline size.Electron paramagnetic resonance(EPR)and ultraviolet–visible diffuse reflectance(UV–vis DRS)confirmed the presence of high concentration of surface defects and Zr3+on mZrO_(2)-5.9 sample,respectively.In situ diffuse reflectance infrared Fourier transform spectroscopy(in situ DRIFTS)analysis indicated that the adsorption strength of formed formate species on catalyst reduced as the crystalline size decreased.These results suggested that surface defects were responsible for CO activation and further influenced the adsorption strength of surface species,and thus the products distribution changed.This study provides an in-depth insight for active sites regulation of ZrO_(2) catalyst in CO hydrogenation reaction.

Study of Methanol Conversion over Fe-Zn-Zr Catalyst

The methanol conversion over Fe-Zn-Zr catalyst was studied at 0.1 MPa and 280-360 ℃ The experimental results indicate that the main products of methanol conversion are methane and butane, and that other hydrocarbons are scarcely produced. All results show that propylene is most probably the olefin formed first in methanol conversion rather than ethene over Fe-Zn-Zr catalyst. Methane is formed from methoxy group, and C4 is possibly yielded on the surface from propylene through binding with a methoxy group.

Accelerating C_(2+)alcohols synthesis from syngas by simultaneous optimizations of CO dissociation and chain growth over CuCo alloy catalyst

With regard to the reaction of higheralcohol synthesis(HAS),the optimizations of activity and selectivity towards C_(2+)alcohol are restricted by the improper equilibrium in two different CO activation pathways and chain growth capacity.Herein,we find that delibrately controlling the compositions of catalysts is an effective strategy to achieve the equilibrium of CO activation pathways and promote the chain growth.As a result,the optimized Cu_(0.25)Co_(0.75) alloy catalyst can achieve a large proportion of higher alcohol in alcohol products(C_(2+)OH/MeOH=4.40),together with high CO conversion of 71.27%and space-time-yield of 147.65 g kg^(-1) h^(-1).The mechanistic studies suggest that the good performance of Cu_(0.25)Co_(0.75) catalyst is attributed to the synergistic effect between alloyed Cu and Co.