Herein, Cu–Mg/Ti-SBA-15 catalysts were prepared through the modification of Cu and Mg to mesoporous Ti-SBA-15 zeolites with different Ti/Si ratios and used for the synthesis of isobutyraldehyde (IBA) from methanol and ethanol. The catalysts were characterized via various techniques including XRF, XRD, TEM, N2 sorption, CO2-TPD, FT-IR, and XPS. With an increase in Ti content, CuO was well dispersed accordingly, and the amounts and strength of the basic sites were reduced. However, an excess introduction of Ti led to the accumulation of single TiO2 crystals, inducing a decrease in the surface area and a deviation from the regular pattern such that the binding energies of Cu 2p, Mg 2p, and Si 2p shifted to lower values. This precisely affected the catalytic behaviors of the prepared catalysts synergistically. The catalyst stability was improved with the increasing Ti content accordingly, and over the catalyst with a Ti/Si ratio = 4/15, the IBA selectivity, after 24 h reaction, could still reach 25%, which was the best durability ever reported for IBA synthesis from methanol and ethanol. The catalytic performance test conducted using a regenerated catalyst and IR measurement of the spent catalyst indicated that carbon deposition on the catalyst surface could be depressed to some extent with the increasing Ti content.

•Ni NPs were well-dispersed on amorphous mesoporous zirconia matrix.•The catalyst showed excellent catalytic activity and good anti-coke property.•The anchoring effect suppressed the sintering of Ni particles.•The increased contact area strengthened the interaction between Ni and ZrO2.A series of mesoporous amorphous Ni–ZrO2 composite oxides with varying Ni contents were prepared by an improved co-precipitation/reflux digestion method and evaluated in the dry reforming of methane. The synthesis method enabled the preparation of uniformly sized Ni particles evenly dispersed within the porous amorphous zirconia matrix. The catalytic reaction results showed that mesoporous amorphous Ni–ZrO2-CR-15 catalyst (Ni loading of 15 wt%) exhibited the highest catalytic activity and excellent stability during the 80-h test among other studied Ni–ZrO2 catalysts. Rapid decline in the catalytic activity was observed for catalysts prepared by traditional impregnation and co-precipitation methods. The improved catalytic performance was attributed to the homogeneous distribution of the small Ni nanoparticles because of the high surface area of the amorphous structure and the strong interaction between Ni and ZrO2. Additionally, the confinement effect of the nano-amorphous structure was responsible for the superior thermal stability of the Ni nanoparticles. Furthermore, Ni–ZrO2-CR-15 catalyst displayed high resistance against carbon deposition owing to the presence of multiple interfaces between the metal and oxide support, absence of strong Lewis acid sites, and presence of different active centers for CO2 dissociation.

An efficient rhenium oxide-modified H3PW12O40/TiO2 catalyst is found for a new synthesis of dimethoxy dimethyl ether from dimethyl ether oxidation. The effects of Re loading, H3PW12O40 content and different feedstocks on the performance of Re–H3PW12O40/TiO2 were investigated. The results showed that DMM2 selectivity was significantly improved up to 60.0%, with 15.6% of DME conversion over 5% Re–20% H3PW12O40/TiO2. NH3-TPD, NH3-IR, Raman spectra, H2-TPR, XPS and TEM were used to extensively characterize the structure and surface properties of the catalysts. The introduction of H3PW12O40 significantly affected the structure and reducibility of surface rhenium oxide species, in addition to increasing the acidity of the catalyst. The increased number of Lewis acid sites and weak acid sites and the optimal ratio of Re4+/Re7+ of Re–H3PW12O40/TiO2 were favorable for the formation of DMM2 from DME oxidation. The possible reaction pathway of DME oxidation to DMM2 was proposed.

•Zr addition affects Cu dispersion and COx adsorption on the catalyst surface.•The catalyst activity strongly depends on the Cu dispersion and Cu surface area.•3% mole of Zr addition results in the best catalyst performance.A series of Cu–ZnO–Al2O3–ZrO2 catalysts with varying Zr contents was prepared as methanol synthesis catalyst by a co-precipitation method and characterized by inductively coupled plasma, N2 physisorption, N2O decomposition, H2-temperature-programmed reduction, X-ray diffraction, and H2/CO/CO2-temperature-programmed desorption. Addition of a suitable amount of ZrO2 to the Cu–ZnO–Al2O3 catalysts increased the Brunauer–Emmett–Teller surface areas and copper surface areas, and improved copper dispersion and reducibility of copper oxide. However, excessive addition of Zr resulted in larger Cu crystallite sizes after catalyst reduction. The Cu–ZnO–Al2O3–ZrO2 catalysts were mixed physically with methanol dehydration γ-Al2O3 catalyst. The resulting catalysts were examined for the catalytic synthesis of dimethyl ether from biomass-derived syngas. Activity tests were conducted in a continuous flow-type fixed-bed reactor. The Cu–ZnO–Al2O3–ZrO2/γ-Al2O3 bifunctional catalyst with 3 mol% Zr exhibited the best catalytic activity and stability. The well-dispersed copper particles with high reducibility and high Cu surface area in the bifunctional catalysts were responsible for the high catalytic performance.

•Two types of catalysts were prepared by impregnation (IP) and impregnation coprecipitation (ICP) methods.•ICP catalyst showed better performance of methanation than that of IP catalyst in slurry reactor.•ICP method is favor for the formation of small size Ni particles and more reducible NiO.•Zr doping can moderate the interaction between Ni and γ-Al2O3 support and promote the dispersion of Ni.Syngas methanation was performed at 280–330 °C in a stirred-slurry reactor with Zr-doped Ni/γ-Al2O3 catalysts. The catalysts were prepared using impregnation (IP) and impregnation–coprecipitation (ICP) methods. The catalyst 25Ni3Zr/γ-Al2O3 (ICP) had relatively high activity in syngas methanation and the water gas shift (WGS) reaction. A high CO conversion, ∼91.2%, was obtained at 325 °C under 1.5 MPa pressure, with a syngas flow of 10,000 mL g−1 h−1. However, the selectivity of CH4 over 25Ni3Zr/γ-Al2O3 (ICP) was 85.2%, which was slightly lower than that of 25Ni3Zr/γ-Al2O3 (IP), because of enhancement of the WGS reaction. The catalysts were characterized using temperature-programmed reduction, X-ray diffraction, and transmission electron microscopy; the results indicated that Ni was well dispersed on the γ-Al2O3 support by the ICP method. Zr doping improved Ni dispersion and H2-promoted dissociation of CO. Furthermore, it was found that the larger amount of reducible Ni formed using the ICP method gave a better catalytic performance.Graphical abstractThe catalyst 25N3ZA prepared by impregnation co-precipitation(ICP) shows higher activity of methanation than that of impregnation (IP), and its CO conversion of CO was as high as 91.2% at reaction conditions of 325 °C, 10,000 mL g−1 h−1 and 1.5 MPa. Superior performance can be attributed to (i) better dispersion of Ni on the γ-Al2O3 support by ICP; (ii) Zr doping improved the dispersion of Ni as well the hydrogen-promoted dissociation of CO.

The effects of Y2O3-modification to Ni/γ-Al2O3 catalysts on autothermal reforming of methane to syngas were investigated. It was found that the introduction of Y2O3 (5%, 8%, 10%) lead to significant improvement in catalytic activity and stability, and the H2/CO ratio could be adjusted via controlling the O2/CO2 ratio of the feed gas. According to the characterization results of catalysts before and after reaction, it was found that the Y2O3·γ-Al2O3 supported Ni catalysts had higher NiO reducibility, smaller Ni particle size, higher Ni dispersion and stronger basicity than those of the Ni/γ-Al2O3 catalysts. The analysis of catalysts after reaction showed that the addition of Y2O3 inhibited the Ni sintering, changed the type of coke and decreased the amount of coke on the catalysts. All the experimental results indicated that the introduction of Y2O3 to Ni/γ-Al2O3 resulted in excellent catalytic performances in autothermal reforming of methane, and Y2O3 played important roles in preventing metal sintering and coke deposition via controlling NiO reducibility, Ni particle size and dispersion, and basicity of catalysts.Graphical abstractHighlights► Ni/γ-Al2O3 catalysts were modified with different amounts of Y2O3. ► Catalysts for autothermal reforming of methane into syngas. ► The introduction of Y2O3 improves the activity and stability of the catalyst. ► Ni/Y2O3·γ-Al2O3 catalysts exhibit good activity and stability in the reaction.

The present study aims at exploring a concept which can convert coal-bed methane (containing methane, air and carbon dioxide) to synthesis gas. Without pre-separation and purification, the low-cost synthesis gas can be produced by coupling air partial oxidation and CO2 reforming of coal bed methane. For this purpose, the co-precipitated Ni–Mg–ZrO2 catalyst was prepared. It was found that the co-precipitated Ni–Mg–ZrO2 catalyst exhibited the best activity and stability at 800 °C during the reaction. The conversions of CH4 and CO2 maintained at 94.8% and 82.1% respectively after 100 h of reaction. The effect of reaction temperature was investigated. The H2/CO ratio in the product was mainly dependent on the feed gas composition. By changing O2/CO2 ratio of the feed gases, the H2/CO ratio in the off-gas varied between 0.8 and 1.8. The experimental results showed that the high thermal stability and basic properties of the catalyst, and the strong metal-support interaction played important roles in improving the activity and stability of the catalyst. With the combined reactions and the Ni–Mg–ZrO2 catalyst, the coal bed methane could be converted to synthesis gas, which can meet the need of the subsequent synthesis processes.Highlights► The co-precipitated Ni–MgO, Ni–ZrO2 and Ni–Mg–ZrO2 as catalysts. ► Catalysts for combined air partial oxidation and CO2 reforming of coal bed methane. ► The introduction of Mg improves the activity and stability of the catalyst. ► Ni–Mg–ZrO2 catalyst exhibits the best activity and stability during the reaction.

Zeolite HZSM-5 is known to be active for the catalytic conversion of methanol into hydrocarbons, but its strong acidity and narrow channels may lead to high selectivity to aromatics, thus decreasing the quality of synthesized gasoline. In this work, an HZSM-5/MnAPO-11 composite was prepared via hydrothermal synthesis, and the catalytic synthesis of high-octane gasoline from syngas was studied in flow-type fixed-bed reactors. The catalysts were characterized employing X-ray diffraction (XRD), N2 adsorption–desorption, ammonia temperature-programmed desorption (NH3-TPD), scanning electron microscopy (SEM), energy-diffusive X-ray spectroscopy (EDS), atomic absorption spectrophotometry (AAS), and Fourier transformed infrared spectroscopy (FT-IR). Compared with HZSM-5 and a mechanical mixture of HZSM-5 and MnAPO-11, the HZSM-5/MnAPO-11 composite showed the highest gasoline yield and iso-paraffin selectivity due to the presence of more mesopores and moderate acid sites. The results provide new perspectives on the synthesis and application of composite molecular sieves in the production of gasoline.

One-step dimethyl ether (DME) synthesis in slurry phase was catalyzed by a hybrid catalyst composed of a Cu-based methanol synthesis catalyst and a γ-Al2O3 methanol dehydration catalyst under reaction conditions of 260 °C and 5.0 MPa. It was found that instability of the Cu-based catalyst led to rapid deactivation of the hybrid catalyst. The stability of the Cu-based catalyst under DME synthesis conditions was compared with that under methanol synthesis conditions. The results indicated that harmfulness of water, which formed in DME synthesis, caused the Cu-based catalyst to deactivate at a high rate. Surface physical analysis, elemental analysis, XRD and XPS were used to characterize the surface physical properties, components, crystal structures and surface morphologies of the Cu-based catalysts. It was found that Cu0 was the active component for methanol synthesis and Cu2O might have less activity for the reaction. Compared with methanol synthesis process, crystallite size of Cu became bigger in DME synthesis process, but carbon deposition was less severe. It was also found that there was distinct metal loss of Zn and Al caused by hydrothermal leaching, impairing the stability of the catalyst. In slurry phase DME synthesis, a part of Cu transformed into Cu2(OH)2CO3, causing a decrease in the number of active sites of the Cu-based catalyst. And some ZnO converted to Zn5(OH)6(CO3)2, which caused the synergistic effect between Cu and ZnO to become weaker. Crystallite size growth of Cu, carbon deposition, metal loss of Zn and Al, formation of Cu2(OH)2CO3 and Zn5(OH)6(CO3)2 were important reasons for rapid deactivation of the Cu-based catalyst.

A commercial Cu-based catalyst for methanol synthesis was studied using a stirred autoclave reactor system in the present study. The synthesis reactions were conducted for different time under the same reaction conditions in order to get catalyst samples with different deactivation degrees. The composition and morphology of the catalyst samples before and after reaction were characterized by the means of temperature programmed reduction (TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), elemental analysis (EA) and nitrogen adsorption techniques. The experimental results indicated that Cu composition of the catalyst had not changed significantly during the reaction, and sintering of Cu particles of the catalysts was the main cause of the catalyst deactivation with time on stream.

The methanol conversion over Fe-Zn-Zr catalyst was studied at 0.1 MPa and 280–360 °C. 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.

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.

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/Al2O3-673> Ni/Al2O3-573> Ni/Al2O3-473> Ni/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%.

Mn-H4SiW12O40/SiO2 heteropolyacid catalysts were prepared by impregnation method from different Mn salt precursors, such as MnSO4, Mn(NO3)2, MnCl2 and Mn(CH3COO)2. The catalytic oxidation reaction of dimethyl ether (DME) to dimethoxymethane (DMM) was carried out in a continuous flow type fixed-bed reactor with a ratio of NDME/NO2 = 1:1. It is found that the sequence of catalytic activity for DMM synthesis is MnCl2-H4SiW12O40/SiO2>Mn(NO3)2-H4SiW12O40/SiO2>MnSO4-H4SiW12O40/SiO2>Mn(AC)2-H4SiW12O40/SiO2. The effects of reaction temperature (573 −633 K) on the catalysts were also investigated. With the increase of reaction temperature, the DME oxidation reaction is more exquisite over MnSO4-H4SiW12O40/SiO2 catalyst. 42.4% of DME conversion and 0.9% of DMM selectivity have also been obtained at 613 K. However, MnCl2 modified H4SiW12O40/SiO2 catalyst obtains higher DMM selectivity (37.5%, at 593 K) than other three catalysts at mild reaction conditions. H2-TPR profiles show that MnSO4 modification demonstrates stronger oxidative performance at high temperature than other catalysts, while MnCl2-H4SiW12O40/SiO2 catalyst exhibits better oxidative performance at low temperature. XRD patterns of the catalysts show that the diffraction peaks are strong and MnO2 diffraction peak is also found over the MnCl2 modified catalyst.