Ni-based catalysts are promising non-precious catalysts for dry reforming of methane (DRM), but their development is hindered by unavoidable coke formation and metal sintering. Herein, Pr-modified Ni/Al2O3 catalysts were prepared to investigate the role of Pr in the conventional Ni/Al2O3 catalyst during DRM. The XRD, XPS, and TEM results indicate that the Pr oxide species (Pr6O11) remain stable after H2 reduction and during DRM. The TG-DSC, CO2-TPD, CO2-TPSR, and O2-TPO results indicate a significant improvement in the adsorption and activation of CO2 by Pr oxide species, as well as the suppression of the formation of graphitic carbon species. In situ DRIFTS measurements reveal the oxygen-assisted CH4 activation and the rapid transformation of CO2 to carbonate species, which restrict the carbon deposition in DRM. By contrast, the unmodified Ni/Al2O3 catalyst shows inferior catalytic stability due to the higher amount and graphitization degree of coke species. This study demonstrates that the Pr oxide species can enhance the coke resistance of Ni-based catalysts during the DRM process.

The dry reforming of methane (DRM) is a key process for valorizing CO2 and CH4, yet the catalyst longevity is limited by severe coking at low temperature. Among various catalysts studied, NiAl-based systems have been a long-standing research focus due to their inherent advantages. However, their practical application has been perpetually hampered by vulnerability to coke formation. This study investigates the effect of varying the Ni0/ Ni2+ ratio (from NiAl2O4) in a 5 wt% Ni/Al2O3 catalyst, while controlling particle size and Ni dispersion, on coke resistance under conditions where carbon formation is thermodynamically favored, i.e., 600 degrees C, CH4:CO2:N2 = 25:25:10, GHSV = 150 L gcat-1 h-1. Using in situ XANES, we established that a catalyst formulation, Ni0/ NiAl2O4/Al2O3, with 32.5% Ni0 and 67.5% Ni2+ achieves the highest performance. Comprehensive pulse experiments and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) provides insights into the reaction mechanism, wherein CHx* (* adsorbed) species from CH4 dissociation on Ni0 are rapidly oxidized by the surface O* from NiAl2O4 to form HCO3* and CO3* intermediates. Simultaneously, the CO disproportionation route to coke is suppressed. In contrast, a catalyst lacking this optimized interface readily promotes coke deposition.

The efficient hydrogenation of CO2 to methanol and dimethyl ether (DME) is a cornerstone of the circular carbon economy, yet it is constrained by the kinetically sluggish activation of H-2 on oxide catalysts. While metal-support interactions offer a lever for tuning activity, a rational strategy to precisely control the spatial distribution of active sites remains a fundamental challenge. Here, we report that the crystallinity of a common oxide support, ZrO2, can be engineered to dictate the surface enrichment of the active GaOx phase in GaOx/ZrO2 catalysts, a phenomenon we coin "crystal phase-confined surface enrichment". Through a combination of in situ spectroscopy, kinetic analysis, and DFT calculations, we demonstrate that the tetragonal ZrO2 phase selectively suppresses the bulk migration of GaOx, thereby concentrating it on the surface. This structural feature creates a highly active interface that significantly enhances H-2 activation, reducing its onset temperature by 25 K and enabling a methanol and DME selectivity of 79.5% with a CO2 conversion yield of 7.25%. Our findings establish support crystallinity engineering as a general design principle for manipulating active site distribution, propelling catalyst design from empirical tuning to predictive structure control for a wide range of heterogeneous catalytic reactions.

While the promoting effect of H2 co-feeding on light alkane dehydrogenation has been investigated, its role in long-chain alkane dehydrogenation, particularly the underlying mechanism, has not been systematically studied. Herein, we show the effect of H2 co-feeding on the evolution of surface species and the restructuring of active sites on Pt-based catalysts. During the reaction, not only carbonaceous species but also key reaction intermediates (olefinic/Pt complexes or early-stage aromatics) were observed. Based on the evolution of these surface species, the reaction can be divided into three stages: rapid coking, quasi-steady state, and surface restructuring. H2 co-feeding not only promotes olefin desorption, shortening the rapid coking stage, but also inhibits deep dehydrogenation of the intermediates. During restructuring without H2 co-feeding, the electron density of the active component decreases and its structure may transition from three-dimensional to raft-like structure, resulting in lower selectivity. In contrast, H2 co-feeding further enhances both the electron density and the alloying degree of the active component, thereby likely improving dehydrogenation activity. This work highlights the strong regulatory effect of surface adsorbates on catalytic reactions and provides deeper insight into the dehydrogenation mechanism.

Non-noble metal systems have shown promising potential as cost-effective alternatives to Pt-based catalysts in the dehydrogenation of long-chain alkanes. However, systematic studies on relevant catalytic systems remain scarce. Here, CeO2 and Co-CeO2 catalysts with varying Co contents were prepared by co-precipitation and evaluated for the dehydrogenation of dodecane in an inert atmosphere. Dual active sites associated with CeO2 and CoOx were identified, both of which exhibited a distinct induction period. In Co-CeO2 catalysts, cobalt incorporated into the CeO2 lattice as Co2+ remained stable under reactive conditions. In contrast, the excess cobalt present at high contents (>= 10%) formed Co3O4 particles that were completely reduced to Co0 due to weak metal-oxide interaction. Furthermore, we propose that Co2+ in CoOx species are the active sites. The observed induction period is attributed to the reduction of these species under the reaction atmosphere and their migration from the bulk to the surface of CeO2. The dehydrogenation activity of the CeO2 catalyst originates from its surface Ce-O Lewis acid-base pairs (Ce4+), and the observed induction period correlates with an increasing concentration of these Ce4+ sites. This study provides valuable insights for the future design of non-noble metal catalysts.

Understanding factors controlling product selectivity in CO2 hydrogenation remains a central research theme for catalytic CO2 utilization. Here, we report a composition-dependent selectivity anomaly in the In-Pd intermetallic series (viz., InPd2, InPd, In3Pd2), where In3Pd2 exhibits 100% CO selectivity via the reverse water-gas shift (RWGS) pathway, in sharp contrast to the high methanol selectivity achieved on other In-rich or Pd-rich metals or intermetallic compounds. Comprehensive characterization reveals that this anomaly arises from Pd enrichment on the surface of In3Pd2 IMC nanoparticles. The enriched Pd sites, modulated by In-to-Pd electron transfer, favor CO formation. In addition, the In-rich sites neighboring the Pd-rich islands facilitate rapid CO desorption. The resulting nanostructure on the surface of In3Pd2 IMCs renders an electronic interaction between In and Pd to promote CO formation and suppress C-H bond formation. This rationale is supported by both density functional theory (DFT) calculations and experimental evidence. These findings demonstrate that compositional control in intermetallic catalysts enables switchable CO2 hydrogenation selectivity and offers a rational approach to designing catalysts with tailored product distributions.

Engineering the metal-support interaction through controlled support reconstruction offers a promising strategy for developing durable catalysts for methane dry reforming (DRM). A series of Ni/Mgx-HAP catalysts were synthesized for methane dry reforming (DRM) by regulating the doping amount of Mg2+ in hydroxyapatite (HAP). High Mg doping (>= 20 mol.%) induced a structural reconstruction from HAP to beta-tricalcium magnesium phosphate (beta-TCMP), which significantly enhanced the metal-support interaction, promoted high dispersion and stable anchoring of Ni species, increased the strong basic sites, and strengthened CO2 adsorption and activation. Catalytic evaluation revealed that the 3Ni/Mg20-HAP catalyst exhibited excellent DRM activity and stability for up to 100 h at 700 degrees C under a high gas hourly space velocity (90,000 mL gcat revealed that Mg doping not only improved anti-coking capability by favoring the formation of amorphous carbon but also suppressed Ni sintering via strengthened metal-support interaction. Mechanistic studies elucidated that Mg doping may influence the reaction pathway by steering the formation of surface carbonate intermediates, thus promoting carbon elimination. This work demonstrates that dopant-induced support reconstruction provides an effective strategy for regulating metal anchoring in durable DRM catalysts.

[This corrects the article DOI: 10.1039/C4RA02809K.].

Against the backdrop of global energy and environmental crises, the technology of CO2 hydrogenation to produce methanol is garnering widespread attention as an innovative carbon capture and utilization solution. Bimetallic oxide catalysts have emerged as the most promising research subject in the field due to their exceptional catalytic performance and stability. The performance of bimetallic oxide catalysts is influenced by multiple factors, including the selection of carrier materials, the addition of promoters, and the synthesis process. Different types of bimetallic oxide catalysts exhibit significant differences in microstructure, surface active sites, and electronic structure, which directly determine the yield and selectivity of methanol. Although bimetallic oxide catalysts offer significant advantages over traditional copper-based catalysts, they still encounter challenges related to activity and cost. In order to enhance catalyst performance, future investigations must delve into microstructure control, surface modification, and reaction kinetics.

Correction for ‘One-pot synthesis of ordered mesoporous transition metal–zirconium oxophosphate composites with excellent textural and catalytic properties’ by Zhichao Miao et al. , New J. Chem. , 2015, 39 , 1322–1329, https://doi.org/10.1039/C4NJ01227E.

The heterogeneous ethanol carbonylation of Ni supported on activated carbon (Ni/AC) is typically associated with significant activity loss, largely due to the facile occurrence of carbon deposition and Ni loss. In this study, the chlorine-containing Ni/AC catalysts were synthesized via the incipient wetness method and exhibited superior stability compared to catalysts without chlorine. Correlation of the catalytic performance and catalyst structure revealed that chlorine addition to Ni/AC reduced the amount of carbon deposition. Moreover, it is evident that there is a robust interaction between chlorine and Ni, as evidenced by XPS and H2-TPR, which can significantly impede the Ni loss during the reaction. The results of in-situ DRIFTS and CO-TPD experiments demonstrate that the addition of chlorine impedes the adsorption of iodine species on Ni/AC catalysts, which consequently affects the adsorption capacity of CO closely associated with the product selectivity.

Dry reforming of methane (DRM), the catalytic conversion of CH4 and CO2 into syngas (H2+CO), is an important process closely correlated to the environment and chemical industry. NiAl-based catalysts have been reported to exhibit excellent activity, low cost, and environmental friendliness. At the same time, the rapid deactivation caused by carbon deposition, Ni sintering, and phase transformation exerts great challenges for its large-scale applications. This review summarizes the recent advances in NiAl-based catalysts for DRM, particularly focusing on the strategies to construct efficient and stable NiAl-based catalysts. Firstly, the thermodynamics and elementary steps of DRM, including the activation of reactants and coke formation and elimination, are summarized. The roles of Al2O3 and its mixed oxides as the support, and the influences of the promoters employed in NiAl-based catalysts over the DRM performance, are then illustrated. Finally, the design of anti-coking and anti-sintering NiAl-based catalysts for DRM is suggested as feasible and promising by tailoring the structure and states of Ni and the modification of Al-based supports including small Ni size, high Ni dispersion, proper basicity, strong metal-support interaction (SMSI), active oxygen species as well as high phase stability.

Hydrogenation of CO2 to C2+ hydrocarbons over non-noble metal catalysts is essential from environmental and economic aspects. However, increasing the selectivity of C2+ hydrocarbons is still challenging for Co-based catalysts, as their predominant selectivity is toward CH4 (>99%). Herein, this work provides insights into the mechanism of CO2 hydrogenation over a N-doped Co3O4 (CoNxOy) catalyst with a higher CO2 conversion (25%) and C2+ hydrocarbon selectivity (42 C-mol%) compared to the Co3O4 parent material (9% and 3 C-mol%, respectively). An increased concentration of oxygen vacancies and a decreased surface basicity strength in CoNxOy correlated with its enhanced catalytic performance. In situ diffuse reflectance infrared Fourier transform spectroscopy and density functional theory calculations revealed the evolution of reaction intermediates and the N-doping benefits on the CoNxOy catalyst for high activity toward C2+ hydrocarbons. The findings were consistent with a CO2 hydrogenation catalytic cycle, where CO and C2+ hydrocarbons are mainly produced through carbonate and formate reaction pathways, respectively. Overall, we found that a relatively simple nitridation procedure can enhance the catalytic activity and selectivity of cobalt oxide toward higher hydrocarbons. This methodology could be extended to improve other transition metal-based catalysts for CO2 conversion.

The oxidative dehydrogenation of ethane to ethylene (ODHE) usually suffers from the issues of ethane conversion-ethylene selectivity seesaw. Herein, a series of alumina-supported Ni and Ga catalysts with different molar ratios of Ni to Ga were synthesized by facile impregnation method constructing the Lewis acid site (LAS) strategy to obtain great ethylene selectivity (97 %). The variation of Ni:Ga ratio adjusted the ionic substitution ability, redox ability and acidity, thus regulate the chemical environment of Ni2+ to the formation of LAS(Al3+/ Ga3+)-Ni-OH structure, which was proposed to be the active site for selective oxidation of ethane to ethylene, as proved by H2-TPR, ToF-SIMS, quasi in-situ XPS and in-situ FTIR. Moreover, the probable mechanism of ODHE reaction was proposed that C2H6 molecules were mainly adsorbed on LAS sites and activated on Ni-OH site of the catalyst. The pulse test further suggested that O- was mainly associated with the generation of CO2 and Ni (2-n) + was connected with the production of CH4. It is highlighted that adjusting the Ni-related species and oxygen species on the catalyst surface are crucial to further improve the ethylene selectivity.

Gas cylinders are widely used in research laboratories, pilot plants, and manufacturing industries because of their affordability, safety, and ease of access as reliable high-pressure gas sources. This review offers a concise summary of gas cylinders, focusing on three significant topics: the categorization of gas cylinders, the color coding of gas cylinders, and the components and identification of gas cylinders. Additionally, it offers guidance on the safe storage, transportation, and use of gas cylinders as well as inspection protocols for gas cylinders in university laboratories in China. Finally, it underlines the hazards that incorrect handling of gas cylinders can cause. By spreading awareness of gas cylinders, we intend to give a more comprehensive audience access to basic knowledge about gas cylinders, lowering the incidence of accidents caused by incorrect handling.

The further improvement of methacrolein (MAL) selectivity from isobutene (IB) oxidation is crucial and challenging. In this study, based on the typical Mo–Bi–Fe–Co–K–O mixed metal oxide, the rare earth element Gd-doped, Ce-doped and CeGd co-doped catalysts were prepared by co-precipitation strategy to increase the selectivity of MAL from 47.9% to 49.8%, 64.2% and 68.6%, respectively. In order to elucidate in-depth the promoting effect of Ce and/or Gd, various characterizations were utilized including X-ray diffraction patterns (XRD), Raman, X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), O2-temperature programmed desorption (O2-TPD), H2-temperature programmed reduction (H2-TPR), CO2-temperature programmed desorption (CO2-TPD), IB-temperature programmed desorption (i-C4-TPD) and in-situ IB-Fourier transform infrared spectroscopy (IB-FTIR). Both Ce and Gd finely regulate the bulk and surface structure of the catalyst, thus altering the redox ability, oxygen mobility and storage ability and basicity. Compared with Ce, Gd addition slightly regulates the variation of Co2+/Co3+ redox couples, greatly enhances the interaction among the components on the catalyst, thus only increases the content of surface oxygen species and has little effect on their mobility. While Ce-containing catalyst performs stronger oxygen storage and migration ability, thus leading to the overproduction of surface Odefect species, which are proposed to be the active sites for the production of MAL and COx. The CeGd co-doped catalyst possesses the proper content of surface Odefect species, thus exhibits much higher MAL selectivity. Moreover, the promoting mechanism of Ce and/or Gd over IB oxidation is proposed. Therefore, this work is helpful for understanding the influence of rare earth elements on the structure of mixed metal oxides and the olefin selective oxidation reaction.

The performance of ethanol carbonylation for Ni supported on different activated carbons varies considerably. The physicochemical properties of Ni catalysts supported on different activated carbons have been investigated in detail by a series of characterization studies. Catalysts with less oxygen-containing groups and smaller pore size are demonstrated to be more effective for vapor-phase ethanol carbonylation, with higher ethanol conversion and selectivity of propionate and ethyl propionate. However, there is no clear correlation between the carbonylation activity and the initial Ni nanoparticles size of the fresh catalysts due to the re-dispersion of the Ni nanoparticles by the ethane iodide interaction during the reaction. It is also proved that the deactivation of the catalyst may be caused by the loss of the active component Ni and the deposition of oxygen-containing carbon species. In situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) showed that ethane iodide is essential for the ethanol carbonylation reaction and that carbonylation intermediates (C2H5CO-Ni-I) are formed only in the presence of ethane iodide. The mechanism of the ethanol carbonylation reaction was proposed, showing that the carbonylation of CO insertion and the elimination of ethylene production in the intermediate are competing reactions. This work has implications for the design of highly efficient alcohol carbonylation catalysts.

丙酸及丙酸乙酯是重要的化工产品和有机合成中间体.中国乙醇资源丰富,以乙醇为原料的非石油途径合成丙酸及丙酸乙酯得到了广泛研究.乙醇均相羰基化存在收率低、反应条件苛刻以及产物与催化剂分离困难等问题.目前,多数研究主要集中在乙醇羰基化多相催化剂的开发.乙醇羰基化多相催化剂分为两类:贵金属催化剂和非贵金属催化剂.该文详细介绍了两类催化剂的研究进展,重点阐述了两类催化剂的反应机理以及助剂、载体和工艺参数对催化剂性能的影响,指出了不同催化剂的优势和不足,并对催化剂应用现状进行了分析.最后展望了乙醇多相羰基化合成丙酸及丙酸乙酯的发展前景.