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Methanol is an essential chemical raw material and potential alternative energy source. In this paper, Cu based catalyst was prepared by the noble solid phase grinding method for CO2 hydrogenation to methanol. The influence of chelating agent, heating rate, calcination temperature and calcination period of the precursor on catalyst performance were studied in depth. The catalyst precursor with formic acid as a chelating agent was reduced in‐situ when calcined in nitrogen (N2) at 573 K. The formic acid was decomposed, releasing the reducing agents, CO and H2, resulting in continuous in‐situ CuO reduction to metallic Cu0. XRD, XPS, BET, TG‐DSC, H2‐TPR and other characterization techniques were employed to analyze the catalyst properties. Results revealed that CuO was successfully reduced in‐situ to Cu0 during calcination process in a nitrogen atmosphere without further reduction. The catalyst prepared by formic acid grinding (F/I−Cu/ZnO) showed highest catalytic activity compared with the conventional catalyst which was further reduced by 5% H2 (F/H−Cu/ZnO). CO2 conversion and methanol selectivity reached 33.44% and 84.26%respectively. [ABSTRACT FROM AUTHOR]

Abstract: A new synthesis method of low-temperature methanol proceeded on Cu/ZnO/Al2O3 catalysts from CO/CO2/H2 using 2-butanol as promoters. The Cu/ZnO/Al2O3 catalysts were prepared by co-impregnation of r-Al2O3 with an aqueous solution of copper nitrate and zinc nitrate. The total carbon turnover frequency (TOF), the yield and selectivity of methanol were the highest by using the Cu/ZnO/Al2O3 catalyst with copper loading of 5% and the Zn/Cu molar ratio of 1/1, which precursor were not calcined, and reduced at 493K. The activity of the catalysts increased due to the presence of the CuO/ZnO phase in the oxidized form of impregnation Cu/ZnO/Al2O3 catalysts. The active sites of the Cu/ZnO/Al2O3 catalyst for methanol synthesis are not only metallic Cu but also special sites such as the Cu–Zn site, i.e. metallic Cu and the Cu–Zn site work cooperatively to catalyze the methanol synthesis reaction. [Copyright &y& Elsevier]

Abstract: Mechanism and kinetics of catalytic process for a new low-temperature methanol synthesis on Cu/ZnO catalysts from syngas (CO/CO2/H2) using catalytically active alcohol promoters were investigated by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Two intermediate species, adsorbed formate species and alkyl formate species, were formed in this synthesis process. The adsorbed formate species easily reacted with ethanol or 2-propanol at 443K and atmospheric pressure, and the reaction rate with 2-propanol was faster than that with ethanol. Alkyl formate was readily reduced to form methanol at 443K and 1.0MPa, and the hydrogenation rate of 2-propyl formate was found to be quicker than that of ethyl formate. As a promoter, 2-propanol exhibited a higher activity than ethanol in the reaction of the low-temperature methanol synthesis. [Copyright &y& Elsevier]

Abstract: In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to study the reaction mechanism of the formate adsorbed species with ethanol to form the ethyl formate on Cu/ZnO catalyst surface in a novel low-temperature methanol synthesis process. The results indicate that the formate adsorbed species were firstly formed by CO/CO2/H2 adsorbed on Cu/ZnO catalyst, followed by rapid reaction with ethanol to form ethyl formate. It was found that the species reacted with formate adsorbed species were ethanol in gas phase rather than adsorbed ethoxy species. The reaction of the adsorbed formate species with ethanol on Cu/ZnO catalyst surface proceeded according to Rideal-type mechanism, not Langmuir–Hinshelwood mechanism. [Copyright &y& Elsevier]

Abstract: In situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) was used to clarify the reaction mechanism of a new methanol synthesis method on a Cu/MgO catalyst at 443K from syngas containing CO2 using an ethanol promoter. The adsorbed formate species were formed by exposing Cu/MgO catalyst to syngas (CO/CO2/H2), and it reacted easily with ethanol to form ethyl formate in two states: gas-phase species and physisorbed species, at low temperature. The ethyl formate was the reactive intermediate, and it was reduced easily by hydrogen atoms on Cu to form methanol at low temperature. The reaction temperature was significantly decreased due to the promotional catalytically active action of ethanol. This is a new reaction route, as ethanol used in this reaction was not consumed due to its self-regeneration by hydrogenation of ethyl formate. In order to accelerate this reaction, one must introduce a large amount of ethanol into the reaction system. [Copyright &y& Elsevier]

Abstract: In situ diffuse reflectance infrared Fourier-transform spectroscopy was used to clarify the reaction mechanism of a new methanol synthesis method on a Cu/ZnO catalyst at low temperature such as 423K from syngas containing CO2 and H2O using a 2-propanol promoter. The formate species was formed by exposing Cu/ZnO catalyst to syngas, and it easily reacted with 2-propanol to form a 2-propyl formate species at low temperature. 2-Propyl formate was then quickly reduced to form methanol and 2-propanol. The Cu/ZnO catalyst was active for all these steps while catalytically cycled 2-propanol realized a low-temperature route. [Copyright &y& Elsevier]

In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to study the reaction mechanism of a new methanol synthesis method on Cu/ZnO at low temperatures from syngas (CO/CO2/H2) using ethanol promoter. The adsorbed formate species were formed by exposing Cu/ZnO catalysts to syngas (CO/CO2/H2), and it reacted easily with ethanol in the gas phase to form ethyl formate in two states of species, gas phase and physisorbed, at low temperatures. Ethyl formate was the reactive intermediate, and it was reduced easily by hydrogen atoms on Cu to form gas-phase methanol. The reaction temperature was significantly decreased due to the catalytic action of ethanol and a new reaction route. In order to accelerate this reaction, a large amount of ethanol must be introduced into the reaction system. When there was no ethanol or little ethanol in the reaction system, this reaction was difficult to complete at a temperature as low as 443 K. [Copyright &y& Elsevier]

A novel method, that the precursor is burnt in argon without further reduction to directly prepare metallic catalyst, is developed using low-valued by-product. Rice husk not only contributed as catalyst support, but also as reductant and fuel. The XRD, TPR and TG-DTA analysis prove that Cu phase in the as-burnt catalyst is almost reduced to metallic Cu 0 . The as-prepared catalysts exhibit higher activity and methanol selectivity than those prepared by a conventional impregnation method. This method may open a new way to prepare metallic catalysts without further reduction, especially for some catalytic reactions promoted by K, Ca, Mg and Mn. [ABSTRACT FROM AUTHOR]

Abstract: A series of the as-burnt and the burnt Cu/ZnO catalysts were prepared by a sol–gel auto-combustion method using metal nitrates with the mole ratio of Cu/Zn=1/1 (noted as M, M=Cu+Zn) and citric acid (noted as CA). When the xerogels were burnt in the argon atmosphere, H2 and CH4 which were came from the decomposition of the citric acid, were the reducing agents and were used in the redox process for synthesizing metallic Cu from Cu2+ in the chelated compound. The XRD patterns revealed that all the as-burnt catalysts with different M/CA molar ratios were converted into pure Cu and ZnO species. TPR analysis of the as-burnt catalyst illustrated that almost no hydrogen was consumed. It proved that Cu2+ in the chelated compound was absolutely reduced to metallic Cu in the as-burnt catalyst. The effects of M/CA molar ratio on the properties of catalysts were studied by TG-DTA, FT-IR, Raman spectrum, XRD, SEM-EDS, BET, and N2O chemisorption techniques. The activity of the as-burnt catalysts without reduction was investigated for low-temperature methanol synthesis from syngas containing CO2 using ethanol as a promoter at 443K and 5.0MPa for 12h. The total carbon conversion increased with increasing the content of citric acid and reached a maximum for the as-burnt Cu/ZnO catalyst C0.8 with M/CA=1/0.8, and then decreased. The variation trend was in accordance with that of the copper (Cu0) surface area. Comparing with the burnt catalyst C0.8-air after reduction, the methanol selectivity of the as-burnt Cu/ZnO catalyst was much lower owing to lower hydrogenation activity of the ethyl formate. The as-burnt catalyst C0.8 was also used in continuous low-temperature methanol synthesis at 443K and 5.0MPa for 40h. The total carbon conversion was stable after 15h and no obvious deactivation during 40h reaction, but the methanol selectivity was still not high. [Copyright &y& Elsevier]

The Cu/ZnO catalyst prepared by urea hydrolysis method was investigated for low-temperature methanol synthesis from syngas containing CO 2 . Concurrently, the activity of the conventional Cu/ZnO catalyst prepared by co-precipitation method was also compared. The effects of precipitation temperature, urea content, stirring speed and the introduction of Al on the catalytic performance of Cu/ZnO were deeply studied. It was found that the total carbon conversion of the Cu/ZnO catalyst prepared by urea hydrolysis method was increased to 45.0% from 32.8%, comparing with that of the catalyst prepared by co-precipitation method. The structure, BET surface area, surface morphology of the catalyst were characterized by XRD, BET, EDX and SEM. The catalyst prepared by urea method obtained higher BET surface area and larger metallic surface area of Cu than those of the co-precipitation method. The crystals sizes of Cu by urea method were smaller than those of co-precipitation method. Surface structure prepared by urea method had needle shape, and it could increase the surface area, different from the catalyst by co-precipitation method. Both the increased BET surface area of the catalysts and the enhanced metallic surface area of Cu 0 promoted the catalyst activity for the low-temperature methanol synthesis. The deactivation of the Cu-ZnO catalysts prepared by urea method was not observed in low-temperature methanol synthesis here. [ABSTRACT FROM AUTHOR]

The Cu/ZnO catalyst prepared by supercritical phase CO 2 drying (denoted as CZS catalyst) and the conventional Cu/ZnO catalyst prepared by heating dry process (denoted as CZO catalyst) were comparatively investigated. The low-temperature methanol synthesis reaction from CO + CO 2 + H 2 using 2-butanol as solvent was conducted over the CZS and CZO catalysts at 443 K and 5.0 MPa for continuous 20 h in a flow-type reactor. It was found that the total carbon conversion of the CZS catalyst was increased from 35.1% to 46.4% and the methanol yield of the CZS catalyst was enhanced from 33.8% to 44.8%, comparing with those of the CZO catalyst. The results of kinetic analysis by in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) revealed that the reaction rate of the low-temperature methanol synthesis on CZS catalyst was faster than that on CZO catalyst at 443 K, in good accordance to the catalytic reaction performances. It was indicated that the supercritical fluid CO 2 , which was used to dry the catalyst precursor, suppressed the sintering of the Cu and ZnO particles and increased both the BET surface area of the catalysts and metallic surface area of Cu 0 , which further improved the reaction activity of the catalyst for the low temperature methanol synthesis. [ABSTRACT FROM AUTHOR]

A ZnO-ZrO 2 metal catalyst prepared by co-precipitation technique, physically combined with a modified zeolite (MeSAPO-34, Me = Zn, Zr, Mn) prepared by the hydrothermal synthesis in a granule stacking arrangement, was tested for direct CO 2 hydrogenation to light olefins. XRD, CO 2 -TPD, NH 3 -TPD, FT-IR, SEM-EDS, N 2 physisorption, HAADF and BET techniques were utilized to characterize the as-prepared catalysts samples. The series reaction phenomenon involved methanol synthesis on the ZnO-ZrO 2 catalyst and methanol-to-light olefins synthesis over the MeSAPO-34 zeolite, which afforded an avenue for precise tailoring of the two different active sites individually. We reveal that the target product selectivity in this process can be optimized by the choice and amount of basic metal embedded into the zeolite ionic structure to tune the acidity of the molecular sieve and limit secondary hydrogenation reactions. The composite (13%ZnO-ZrO 2 /Mn 0.1 SAPO-34) realized a very high CO 2 conversion of 21.3%, suppressed CO and CH 4 selectivity below 43% and 4% respectively, attained a remarkable light olefins selectivity of 61.7% at 380 °C, 2 MPa, and GHSV = 4800 h−1. The catalyst synthesis approach coupled with the tandem reactions involved open more prospects to utilizing CO 2 resources in green chemistry. [Display omitted] • Composite catalysts comprising 13%ZZ and MeSAPO-34 were prepared by granule mixing. • Tandem reactions over 13%ZZ/MnSAPO-34 catalyst enhanced target product distribution. • Optimized reaction parameters and acid density recorded highest olefins selectivity. [ABSTRACT FROM AUTHOR]