Abstract: Conversion of saturated straight-chain alkanes generated in the deep desulfurization process of fluid catalytic cracking (FCC) gasoline and the coal-to-oil processes into aromatics via alkane aromatization is an important non-petroleum route for the preparation of aromatics that effectively improves the quality of oil. The aromatization technology of C2−C5 light hydrocarbons is relatively mature and has been used in industry. However, for the aromatization of ${\rm{C}}_6^+ $n-alkanes, the aromatics yield is still very low due to the complex reaction process and the competition of various elemental reactions. In addition, the catalysts usually suffer from rapid deactivation. In this work, we summarize the recent advances in the aromatization of ${\rm{C}}_6^+ $n-alkanes. The reaction mechanism of aromatization of ${\rm{C}}_6^+ $ alkanes and the effects of the dispersion of metal sites, electronic state, and acidity, morphology and pore structure of the support on the catalytic performance are discussed in detail.
Abstract: Fischer-Tropsch synthesis (FTS) is the key technology of indirect coal liquefaction. Iron-based catalysts are commonly used. Due to the complexity of phase transition and the difficulty of in-situ characterization, density functional theory (DFT) has become a necessary means to study the adsorption and reaction of surface species on iron-based catalysts. In this review, the formation of different iron carbide phases and the adsorption properties of surface species were discussed based on the surface chemical properties of iron-carbon compounds. Then, the elementary reactions involved in the current DFT calculation research are briefly described. The research of chain initiation, chain growth, and chain termination under different mechanisms is summarized. Combined with the experimental research progress, the regulation mechanism of the promoters on the structure and performance of iron-based catalysts was reviewed. Finally, the existing problems of iron-based catalysts are summarized. The role of surface carbon in the reactions and the effects of various phases are prospected combined with recent results.
Abstract: Synthesis gas (CO + H2) conversion into clean fuels and chemicals through Fischer-Tropsch Synthesis (FTS) is an important way to clean utilization of coal and ensure China energy security. Investigation of FTS reaction mechanism at the molecular level, including of activation of synthesis gas on catalyst surface, the chain growth via CnHx* and CnHxOy*, as well as the chain termination into alkanes, olefins, alcohols, and acids, is the key to the regulation of FTS products, the rational design and development of high-performance catalysts. It is also a hot and difficult point in catalysis science. To study FTS reaction mechanism, intermediate detection, modeling compound addition, steady-state kinetics based on reaction mechanism, steady-state isotope transient kinetic analysis (SSITKA), first-principles calculations, and reaction networks, etc. have been applied to reveal the mechanism of synthesis gas conversion. This paper systematically summarizes the research results of reaction mechanism over the past century, proposes a reasonable route map for FTS reaction, and gives a prospection of the research on FTS mechanism.
Abstract: Chinese energy structure is rich in coal and less in oil, and the development of efficient and clean utilization of coal resources is a key development direction in China. Coal can be used to synthesize dimethyl oxalate (DMO) after carbonylation by synthesis gas, and DMO can further be hydrogenated to obtain oxygen-containing chemicals with high added value, such as methyl glycolate (MG), ethylene glycol (EG), ethanol (EO), etc. Among them, MG can prepare degradable materials polyglycolic acid (PGA), EG can synthesize polyethylene glycol (PEG), and EO can synthesize ethyl acetate (EAC), which have wide application prospects. This paper focuses on DMO hydrogenation reactions, analyzes the research status of catalysts used in each hydrogenation process, focuses on the regulation of catalyst composition, catalytic mechanism and new catalyst preparation technology, analyzes the problems and challenges in the development of DMO hydrogenation catalysts, and points out the application bottlenecks and future development trends of hydrogenation products and downstream products.
Abstract: Dimethyl carbonate (DMC) is a widely used environment-friendly green chemical, and the direct synthesis of DMC from CO2 and CH3OH has become one of the research focuses on the clean conversion of CO2 in recent years. The design of efficient and stable catalysts and reaction processes to promote the conversion of CO2 is the key to realize the direct synthesis of DMC in industry. In this paper, the research progress of catalytic systems for the direct synthesis of DMC from CO2 and CH3OH is reviewed and the reaction mechanism of different types of catalysts is summarized, mainly including the ionic liquid catalyst, alkali metal carbonate catalyst, transition metal oxide catalyst, etc. The operation principle of various dehydrating agents and their promoting effect on the production of DMC are expounded, while the advantages and disadvantages of different catalytic-dehydration systems are analyzed. It is predicted that the development of efficient and stable catalysts and membrane materials with strong permeability to water as well as the construction and implementation of new dehydration processes will be the focus of future research on the direct synthesis of DMC from CO2 and CH3OH.
Abstract: Electrocatalytic CO2 reduction (Electrocatalytic CO2 Reduction, ECR) can realize the storage and utilization of renewable energy and convert CO2 into high-value chemicals. It is an important way of energy utilization under the background of "carbon peaking and carbon neutrality goals", with significant economic and environmental benefits. High efficiency catalyst is the core of ECR process. Single-atom catalysts are ideal for ECR because of the theoretical 100% utilization of active components. Carbon materials have the advantages of high surface area and excellent conductivity, which is quite suitable for electrocatalysis. Herein, by classifying according to the different interaction between the single atomic active center and the carbon support, we reviewed the preparation, structure, properties and action mechanism of single-atom catalysts supported on representative carbon materials in the past decade. We hope it would provide inspirations and ideas for the future investigations.
Abstract: This paper reviews the latest progress in the field of CO2 electrocatalytic reduction to formate in the past five years. The reaction mechanism of CO2 electroreduction to formate and the types of catalysts used in this process are introduced, including metal catalysts, atomic dispersion catalysts, metal oxide catalysts, carbon materials, and composite material catalysts. The main factors affecting product selectivity, catalytic activity and stability are analyzed in detail from the perspectives of catalyst, electrolyte, reaction atmosphere and electrolytic cell. In view of the current research status of carbon dioxide electroreduction to formate, it is proposed to innovate on nanomaterials and composites, explore the active site and reaction path with the help of in-situ characterization technology, and guide the design and synthesis of efficient catalysts, improve the electrochemical reactor module to improve the catalytic efficiency and other issues can be regarded as the future research focus and development direction.
Abstract: The catalytic performance of zeolites is closely related to their framework structure and a clear understanding of such a structure-performance relationship is of great significance in revealing catalytic reaction mechanism as well as in developing efficient zeolite catalysts. Herein, ZSM-11 and ZSM-5 zeolites with similar morphology, crystal size, textural properties and acidity were hydrothermally synthesized; the effects of their differences in the 10-ring channels on the catalytic performance in the conversion of methanol to olefins (MTO) were investigated by using various characterization techniques. The results indicate that in comparison with the straight channel of ZSM-11, the sinusoidal channel of ZSM-5 has stronger diffusion resistance, which promotes the hydrogen-transfer in higher olefins, leads to forming more polymethylbenzene species and then raises the contribution of aromatic-based cycle. In contrast, ZSM-11 with straight channel can reduce the formation of polymethylbenzene species and enhance the alkene-based cycle. As a result, compared with ZSM-5-60 with similar morphology and acidity, ZSM-11-60 as a catalyst in MTO exhibits longer lifetime (98.3 h vs. 65.4 h) and higher selectivity to propene (34.6% vs. 27.4%). The insight shown in this work helps to have a better understanding of the relation between zeolite structure and catalytic performance in MTO and is then beneficial to the development of better catalysts and processes for MTO.
Abstract: Shifting products of Fischer-Tropsch Synthesis (FTS) from paraffins to value-added higher alcohols receives great attention but remains great challenge. Herein, metal oxides of Mn, Zn, La and Zr are investigated as promoters to tune the activity and product distributions of Co/AC catalyst for syngas conversion. It is found that these promoters show different promotion effect on CO dissociation rate, the formation of Co2C phase and the alcohols selectivity. The formed Co2C/Co0 constitutes the dual active site for higher alcohols synthesis. The strongest CO dissociation rate is observed for Zn-promoted Co/AC catalyst, resulting in the highest activity and space-time yield (STY) of alcohols. The Mn promoter is most conducive to the formation of Co2C, but slightly decreases the activity. The similar CO dissociation rate and CO conversion are obtained over both Zr- and La-promoted Co/AC catalysts, but the Zr-promoted Co/AC catalyst exhibits the highest alcohols selectivity due to the function balance between CO non-dissociative insertion and CO dissociation.
Abstract: A flexible polymer (DP) was prepared by in-situ covalent assembly of dual-amino-functionalized ionic liquids and terephthalaldehyde. A core-shell composite (MIL-101@DP) was constructed by coating DP on the surface of metal-organic frame material MIL-101 (Cr) by post-synthesis modification, and was applied to catalyze the cycloaddition reaction of CO2 and epichlorohydrin (ECH). MIL-101@DP retains the advantage of high specific surface area and high porosity of MIL-101 (Cr), and combines the nucleophilic site Cl− and Lewis acidic site Cr3 + . Under the synergistic interaction of Lewis acid sites and Lewis base sites, MIL-101@DP could efficiently catalyze activity the conversion of CO2 and ECH reaction (ECH conversion rate can reach 99%) at atmospheric pressure, 80 ℃, 24 h and without cocatalyst. The activity did not decrease significantly after four cycles.
Abstract: nCo-Al2O3 catalysts with different Co contents (n=2%, 5%, 10%, 15%, 20%) were prepared by a sol-gel approach. The effect of Co content on the nCo-Al2O3 catalyst structure and performance in the oxidative dehydrogenation of ethylbenzene to styrene by CO2 was investigated. The results showed that the isolated Co2 + ions on the nCo-Al2O3 catalysts had a positive influence on the catalytic activity, where the isolated tetrahedral Co2 + species were considered as the active sites. Co contents on the Co-Al2O3 catalyst greatly affected the structure of Co species and the catalytic performance. The isolated tetrahedral Co2 + species are preferentially generated on the resultant nCo-Al2O3 catalyst when the content of Co (n) is less than 10%; as a result, an increase of Co content here leads to the formation of more isolated Co2 + sites and then improves the catalytic activity of nCo-Al2O3 in the dehydrogenation of ethylbenzene. When Co content exceeded 10%, crystalline Co3O4 particles were obtained on the formed catalyst, which resulted in the decline of the isolated Co2 + sites and catalytic activity. Among various nCo-Al2O3 catalysts, 10Co-Al2O3 exhibited the best catalytic performance, with 64.4% conversion rate for ethylbenzene and 99.3% selectivity for styrene at 550 ℃. This catalyst remained stable without obvious deactivation for 30 h of reaction, which suggests that the isolated Co2 + species as active sites presented excellent structural stability and excellent anti-coke deposition.
Abstract: In this paper, the steam reforming reactions of the hydrogen-rich biomass pyrolysis gas and methane (CH4) were compared. The influence mechanism of hydrogen-rich biomass pyrolysis gas components on the reforming reaction of CH4 and other low hydrocarbons was discussed, and the catalytic effect of Ni/γ-Al2O3 catalyst was revealed. H2 could provide a reductive atmosphere to maintain the dynamic balance of the highly active Ni0 on the catalyst surface, so as to improve its catalytic activity. At the same time, biomass pyrolysis gas could inhibit the conversion of transition carbon to graphitic carbon, reducing the influence of carbon deposition on the catalytic activity of Ni/γ-Al2O3. In addition, the influence of operating conditions such as reaction temperature, the ratio of steam and carbon (S/C), as well as space velocity on the steam reforming reaction of hydrogen-rich pyrolysis gas was investigated. The increase of reaction temperature and S/C ratio effectively promoted the steam reforming of CH4 and inhibited the production of carbon deposition. With the increase of space velocity, the competitiveness of CH4 steam reforming reaction was weakened, whereas that of water gas shift reaction and CH4 dry reforming was increased. Hence, the transformation of CH4 was inhibited. This paper cound lay a foundation for the research on the mechanism of biomass pyrolysis gas steam reforming reaction and the development of high-efficiency catalysts.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
