Selective oxidation of alcohols over Si<Subscript>3</Subscript>N<Subscript>4</Subscript>-supported silver catalysts

Silver-containing catalysts supported on ceramic silicon nitrides and modified with Zr or Al are considered. The catalytic activities of the catalysts in the dehydrogenation and oxidative dehydrogenation of ethanol into acetaldehyde are compared. The introduction of oxygen into the reaction mixture decreases the temperature of 100% ethanol conversion to 270°C and increases the acetaldehyde selectivity to 95% for all of the catalysts. According to temperature-programmed reduction data, the simultaneous presence of Fe and Ag on the catalyst surface enhances the activity of the supported catalysts. It is hypothesized that the Ag/Fe interface plays the key role in the formation of active sites on the catalyst surface.     

过渡金属修饰对Pt/M-DMSN催化剂丙烷脱氢性能的影响

以两步法制备了一系列过渡金属(M=Fe, Co, Ni, Cu, Zn)修饰的树枝状介孔二氧化硅纳米粒子(DMSN)负载铂(Pt/M-DMSN)催化剂, 并对该系列催化剂进行了丙烷催化脱氢性能评价. X射线衍射(XRD)、 透射电子显微镜(TEM)、 紫外-可见漫反射光谱(UV-Vis DRS)和氢气程序升温还原(H₂-TPR)表征结果表明, 不同过渡金属在DMSN载体表面分散状态不同,且与Pt的相互作用程度不同. 其中Zn-DMSN载体最有利于Pt的分散, 且反应后催化剂上积碳含量最低; Pt/Fe-DMSN催化剂中Pt与载体的相互作用力较强. 通过活性评价结果可知, Pt/Fe-DMSN催化剂表现出最优的丙烷催化脱氢性能, 丙烷初始转化率为44.2%, 反应6 h后丙烷转化率仍可达36.5%.     

Role of carbon dioxide in the ethylbenzene dehydrogenation coupled with reverse water–gas shift

The dehydrogenation of ethylbenzene (EB) to styrene (ST) in the presence of carbon dioxide instead of steam is believed to be an energy-saving and environmentally friendly process. However, the reaction mechanism for this coupling system still remains unclear. Therefore, the role of carbon dioxide was investigated by means of catalytic reactions and temperature-programmed desorption (TPD) of carbon dioxide over a series of Fe and V supported catalysts as well as thermodynamic analysis. The results showed that the ethylbenzene conversion is associated with the conversion of carbon dioxide, and that there exists a synergistic effect between the ethylbenzene dehydrogenation and the reverse water–gas shift. However, the difference in the behaviour of the catalysts between the single reverse water–gas shift and the coupled ethylbenzene dehydrogenation may suggest that the catalysts are different in the reaction mechanisms for the coupled ethylbenzene dehydrogenation. Carbon dioxide can be activated through either basic sites or redox sites on the catalyst. Based on these results, the role of carbon dioxide and reaction mechanisms are proposed.     

Graphdiyne Based Atomic Catalyst:an Emerging Star for Energy Conversion

Atomic catalysts(Acs)consisting of zero-valent metal atoms anchored on supporting materials have shown promising potentials in catalysis and energy conversion due to their higher atomic utilization,higher selectivity,activity and durability toward target reactions.However,traditional single-atom catalysts are mainly composed of clusters of metal atoms,which cannot effectively solve the problems of easy migration and aggregation of metal atoms.Besides,the traditional synthesis methods still lack breakthroughs in improving the stability and accurately controlling the chemical structure and charge distribution of metal atoms,which seriously limits the understanding of structure-activity relationship and catalytic mechanism in the catalytic reaction process at the atomic level.Graphdiyne(GDY)based Acs are stabilized by incomplete charge transfer between metal atoms and supporting materials,resolving the easy migration and aggregation of traditional single atomic catalysts,which have been regarded as the next generation of catalysts.This review will start with the overview of the synthesis methods for precisely anchoring of different zero-valent transition metal atoms(e.g.,Ni,Fe,Mo and Cu)and noble metal atoms(e.g.,Pd and Ru),followed by focusing on the recent advances in the researches of the Acs toward a series of important reactions for energy conversion technologies,including the electrochemical water splitting(EWS),nitrogen reduction reaction(NRR),oxygen reduction reaction(ORR)and others.Finally,the review concludes with a perspective highlighting the promises and challenges in the further development of Acs.     

原子数精确的金属纳米团簇在电催化领域的应用研究进展

金属纳米团簇（M NCs）是由几个到数百个金属原子组成,其尺寸一般小于2 nm。金属纳米团簇在许多催化反应中表现出高的催化活性和选择性,这与金属纳米团簇具有高的比表面积、较多暴露的活性原子,以及与金属纳米粒子（M NPs）不同的电子结构有关。金属纳米团簇确定的组成和结构使其成为一种新型模型催化剂,对纳米团簇的催化性能研究有利于人们深入理解催化剂结构-性质之间的关系,更利于催化剂的理性设计与发展。结合近几年国内外和本课题组在金属纳米团簇电催化领域的研究进展和现状,本文对该领域的代表性工作进行了简要综述,并对其未来在电催化领域的应用前景和需要解决的关键问题进行了展望。     

氮掺杂碳纳米管负载的Ru和Pd催化剂上异丙醇的转化(英文)

Ru and Pd (2 wt%) loaded on pure and on Ndoped carbon nanotubes (NCNTs) were prepared and tested using the isopropyl alcohol decomposition reaction as probe reaction. The presence of nitrogen functionalities (pyridinic, pyrrolic, and quaternary nitrogen) on the nitrogen doped support induced a higher metal dispersion: Pd/NCNT (1.8 nm) Pd/CNT (4.9 nm), and Ru/NCNT (2.4 nm) Ru/CNT (3.0 nm). The catalytic activity of the supports was determined first. Isopropyl alcohol conversion produces acetone on CNTs while on NCNTs it led to both dehydration and dehydrogenation products. At 210 °C and in the presence of air, the isopropyl alcohol conversion was higher on the NCNTs (25%) than on the CNTs (11%). The Pd loaded catalysts were more active and more selective than the Ru ones. At 115 °C, the Pd catalysts were 100% selective towards acetone for a conversion of 100%, whereas the Ru catalysts led to dehydration and dehydrogenation products. The nitrogen doping induced the appearance of redox properties when oxygen is present in the reaction mixture.     

Al2O3负载Cu,Fe或Ni掺杂氧化钼催化乙苯氧化脱氢（英文）

Molybdenum-based catalysts supported on Al2O3 doped with Ni, Cu, or Fe oxide were synthesized and used in ethylbenzene dehydrogenation to produce styrene. The molybdenum oxide was sup-ported using an unconventional route that combined the polymeric precursor method (Pechini) and wet impregnation on commercial alumina. The samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, temperature-programmed reduction of H2 (H2-TPR), and thermogravimetric (TG) analysis. XRD results showed that the added metals were well dis-persed on the alumina support. The addition of the metal oxide (Ni, Cu, or Fe) of 2 wt% by wet im-pregnation did not affect the texture of the support. TPR results indicated a synergistic effect be-tween the dopant and molybdenum oxide. The catalytic tests showed ethylbenzene conversion of 28%–53% and styrene selectivity of 94%–97%, indicating that the addition of the dopant improved the catalytic performance, which was related to the redox mechanism. Molybdenum oxides play a fundamental role in the oxidative dehydrogenation of ethylbenzene to styrene by its redox and acid–base properties. The sample containing Cu showed an atypical result with increasing conver-sion during the reaction, which was due to metal reduction. The Ni-containing solid exhibited the highest amount of carbon deposited, shown by TG analysis after the catalytic test, which explained its lower catalytic stability and selectivity.     

An efficient Ag/MIL-100(Fe) catalyst for photothermal conversion of CO2 at ambient temperature

The conversion of CO₂ under mild condition is of great importance because these reactions involving CO₂ can not only produce value-added chemicals from abundant and inexpensive CO₂ feedstock but also close the carbon cycle. However, the chemical inertness of CO₂ requires the development of high-performance catalysts. Herein, Ag nanoparticles/MIL-100(Fe) composites were synthesized by simple impregnation-reduction method and employed as catalysts for the photothermal carboxylation of terminal alkynes with CO₂. MIL-100(Fe) could stabilize Ag nanoparticles and prevent them from aggregation during catalytic process. Taking the advantages of photothermal effects and catalytic activities of both Ag nanoparticles and MIL-100(Fe), various aromatic alkynes could be converted to corresponding carboxylic acid products (86%–92% yields) with 1 atm CO₂ at room temperature under visible light irradiation when using Ag nanoparticles/MIL-100(Fe) as photothermal catalysts. The catalysts also showed good recyclability with almost no loss of catalytic activity for three consecutive runs. More importantly, the catalytic performance of Ag nanoparticles/MIL-100(Fe) under visible light irradiation at room temperature was comparable to that upon heating, showing that the light source could replace conventional heating method to drive the reaction. This work provided a promising strategy of utilizing solar energy for achieving efficient CO₂ conversion to value-added chemicals under mild condition.     

正丁烷脱氢制正丁烯催化剂*

综述了对正丁烷脱氢制备正丁烯的催化剂体系,包括有氧脱氢中钒基催化剂、钼酸盐系列和焦磷酸盐系列催化剂;催化脱氢中贵金属Pt系催化剂、以ZSM-5分子筛为载体的催化剂以及膜反应器。探讨了正丁烷脱氢动力学,并在Mars-van Krevlen和 Eley-Rideal机理模型动力学基础上归纳了正丁烷氧化脱氢及直接脱氢的机理。讨论了正丁烷催化剂的影响因素,比较了各类催化剂的特点并对其进行展望,认为ZSM-5分子筛将可能成为正丁烷脱氢制正丁烯的新的研究热点。     

MIL-100(Fe) Supported Pt−Co Nanoparticles as Active and Selective Heterogeneous Catalysts for Hydrogenation of 1,3-Butadiene

Superior catalytic performance for selective 1,3-butadiene (1,3-BD) hydrogenation can usually be achieved with supported bimetallic catalysts. In this work, Pt−Co nanoparticles and Pt nanoparticles supported on metal–organic framework MIL-100(Fe) catalysts (MIL=Materials of Institut Lavoisier, PtCo/MIL-100(Fe) and Pt/MIL-100(Fe)) were synthesized via a simple impregnation reduction method, and their catalytic performance was investigated for the hydrogenation of 1,3-BD. Pt1Co1/MIL-100(Fe) presented better catalytic performance than Pt/MIL-100(Fe), with significantly enhanced total butene selectivity. Moreover, the secondary hydrogenation of butenes was effectively inhibited after doping with Co. The Pt1Co1/MIL-100(Fe) catalyst displayed good stability in the 1,3-BD hydrogenation reaction. No significant catalyst deactivation was observed during 9 h of hydrogenation, but its catalytic activity gradually reduces for the next 17 h. Carbon deposition on Pt1Co1/MIL-100(Fe) is the reason for its deactivation in 1,3-BD hydrogenation reaction. The spent Pt1Co1/MIL-100(Fe) catalyst could be regenerated at 200 °C, and regenerated catalysts displayed the similar 1,3-BD conversion and butene selectivity with fresh catalysts. Moreover, the rate-determining step of this reaction was hydrogen dissociation. The outstanding activity and total butene selectivity of the Pt1Co1/MIL-100(Fe) catalyst illustrate that Pt−Co bimetallic catalysts are an ideal alternative for replacing mono-noble-metal-based catalysts in selective 1,3-BD hydrogenation reactions.     

SO2存在下钠、钙、铁及其复合物对NO-半焦反应的催化作用

采用程序升温还原技术，在SO2存在气氛下，对钠、钙、铁及其复合物的NO-半焦催化反应性能进行了研究。结果表明，在相同条件下三种金属对NO-半焦反应的催化活性顺序为：Fe>Ca>Na。SO2可能通过参与氧传递过程来影响金属对NO-半焦反应的催化活性。SO2的浓度对负载三种不同金属半焦催化活性的影响是不同的。SO2浓度对负载钠半焦的催化活性影响最为显著。在SO2存在气氛下，负载2％钠或铁和负载3％钙的半焦具有高的NO转化活性。在SO2存在气氛下，钠－钙和钠－铁二元金属复合催化剂的活性较高，这可能是由于这两种金属间存在协同作用的缘故。     

Viable Photocatalysts under Solar‐Spectrum Irradiation: Nonplasmonic Metal Nanoparticles

Supported nanoparticles (NPs) of nonplasmonic transition metals (Pd, Pt, Rh, and Ir) are widely used as thermally activated catalysts for the synthesis of important organic compounds, but little is known about their photocatalytic capabilities. We discovered that irradiation with light can significantly enhance the intrinsic catalytic performance of these metal NPs at ambient temperatures for several types of reactions. These metal NPs strongly absorb the light mainly through interband electronic transitions. The excited electrons interact with the reactant molecules on the particles to accelerate these reactions. The rate of the catalyzed reaction depends on the concentration and energy of the excited electrons, which can be increased by increasing the light intensity or by reducing the irradiation wavelength. The metal NPs can also effectively couple thermal and light energy sources to more efficiently drive chemical transformations.     

原位合成钴/还原氧化石墨烯纳米粒子催化氨硼烷制氢

采用简单的原位还原合成方法,利用具有温和还原性能的氨硼烷作为还原剂,在室温下一步还原氧化石墨烯和氯化钴混合溶液制备了还原氧化石墨烯负载钴纳米复合材料催化剂. 利用所制备的钴/还原氧化石墨烯催化剂催化氨硼烷水解制氢,发现钴/还原氧化石墨烯具有优异的催化性能. 相对于没有负载的钴纳米粒子以及采用硼氢化钠作为还原剂制备的钴/还原氧化石墨烯催化剂,采用氨硼烷还原制备的钴/还原氧化石墨烯催化剂表现出更加优越的催化性能. 动力学测试表明,钴/还原氧化石墨烯催化氨硼烷水解反应为零级反应,同时钴/还原氧化石墨烯催化剂催化氨硼烷水解反应的活化能为27.10 kJ·mol^-1,低于大部分已报道的其它催化剂,甚至一些贵金属催化剂的活化能. 钴/还原氧化石墨烯催化剂有着稳定的循环使用性,特别是其具有的磁性使得它能够直接从溶液中通过磁力回收,极具应用前景. 这种简单有效的合成方法有望推广到其它的金属-还原氧化石墨烯纳米复合材料体系.     

四氯化碳液相催化加氢制氯仿多元金属催化剂的制备及其催化性能

以贵金属M(=Pd,Pt)为主要活性成分,掺加过渡金属Fe和Ni作为助剂,采取浸渍和氢气还原法制备了椰壳活性炭(ACcs)负载的单元金属(M/ACcs)、二元金属(M-Ni/ACcs、M-Fe/ACcs)和三元金属(M-Ni-Fe/ACcs)系列催化剂;通过CC_l4液相催化加氢制氯仿反应考察了这些催化剂的催化活性和选择性。结果表明,Pd基催化剂的催化活性明显高于Pt基催化剂,但后者对氯仿的选择性优于前者;在前5 h加氢反应时段,两系列催化剂的活性顺序为:Pd-Ni-Fe/ACcsPd-Fe/ACcsPd/ACcsPd-Ni/ACcs和Pt/ACcs≈Pt-Fe/ACcsPt-Ni/ACcsPt-Ni-Fe/ACcs;总体上,引入Fe对于催化性能的改善效果要优于Ni,Ni的单独引入则会不同程度地降低催化活性。综合考量成本、活性和选择性等因素,优选Pd-Ni-Fe/ACcs作为催化剂,在393 K下反应5 h,可实现CC_l497.6%的转化率以及接近100%氯仿的选择性。     

乙烷脱氢制乙烯技术研究进展及趋势

在碳中和及全球能源供需版图调整的背景下,乙烯生产原料轻质化成为主流趋势。乙烷脱氢制乙烯技术具有低能耗、低碳排、流程短、收率高、成本低等优势,但目前工业上主要通过乙烷蒸汽裂解法生产乙烯,其他方法工业化生产相对不成熟。本文简述了近年来乙烷脱氢制乙烯技术(包括直接催化脱氢、O₂辅助氧化脱氢、CO₂辅助氧化脱氢、化学链氧化脱氢、催化膜反应器脱氢等)工艺及催化剂的研究现状,同时介绍了其他新兴工艺及催化剂。乙烷脱氢制乙烯技术现阶段面临的挑战不仅在于开发更高效的催化剂及更低能耗的技术,更需要突破乙烷脱氢热力学平衡的限制设计合适的反应路径,其中催化膜反应器脱氢、化学链氧化脱氢工艺都具有非常广阔的市场和工业化发展前景。     

Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks

The semihydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry. Unfortunately, state-of-the-art heterogeneous catalysts hardly achieve high turnover frequencies (TOFs) simultaneously with almost full conversion, excellent selectivity, and good stability. Here, we used metal–organic frameworks (MOFs) containing Zr metal nodes (“UiO”) with tunable wettability and electron-withdrawing ability as activity accelerators for the semihydrogenation of alkynes catalyzed by sandwiched palladium nanoparticles (Pd NPs). Impressively, the porous hydrophobic UiO support not only leads to an enrichment of phenylacetylene around the Pd NPs but also renders the Pd surfaces more electron-deficient, which leads to a remarkable catalysis performance, including an exceptionally high TOF of 13835 h⁻¹, 100 % phenylacetylene conversion 93.1 % selectivity towards styrene, and no activity decay after successive catalytic cycles. The strategy of using molecularly tailored supports is universal for boosting the selective semihydrogenation of various terminal and internal alkynes.     

Dehydrogenation of ethylbenzene with nitrous oxide in the presence of mesoporous silica materials modified with transition metal oxides

The novel mesoporous templated silicas (MCM-48, SBA-15, MCF, and MSU) were used as supports for transition metal (Cu, Cr, or Fe) oxides. The catalysts were synthesized using the incipient wetness impregnation, and characterized by low-temperature N2 sorption, DRIFT, photoacoustic IR spectroscopy, UV-vis diffuse reflectance spectroscopy, and temperature-programmed desorption of ammonia. It was shown that the preparation method used results in different distributions and dimensions of the transition metal oxide clusters on the inert support surface. The prepared catalysts were tested in the reaction of oxidative dehydrogenation of ethylbenzene in the presence of nitrous oxide. The iron-containing catalysts showed the highest catalytic activity. The presence of isolated Fe3+ was found to be the most important factor influencing the ethylbenzene conversion. The undesirable effect of the increase in selectivity toward CO2 was observed for the samples with the highest concentrations of acidic surface sites.     

Reaction Mechanism of One-Step Conversion of Ethanol to 1, 3-Butadiene over Zn-Y/BEA and Superior Catalysts Screening

The one-step conversion of ethanol to 1, 3-butadiene has achieved a breakthrough with the development of beta zeolite supported dual metal catalysts. However, the reaction mechanism from ethanol to butadiene is complex and has not yet been fully elucidated, and no catalyst screening effort has been done based on central metal atoms. In this work, density functional theory (DFT) calculations were employed to study the mechanism of one-step conversion of ethanol to butadiene over Zn-Y/BEA catalyst. The results show that ethanol dehydrogenation prefers to proceed on Zn site with a reaction energy of 0.77 eV in the rate-determining step, and the aldol condensation to produce butadiene prefers to proceed on Y site with a reaction energy of 0.69 eV in the rate-determining step. Based on the mechanism revealed, six elements were selected to replace Y for screening superior combination of Zn-M/BEA (M=Sn, Nb, Ta, Hf, Zr, Ti; BEA: beta polymorph A) for this reaction. As a result, Zn-Y/BEA (0.69 eV) is proven to be the most preferring catalyst compared with the other six ones, and Zn-Zr/BEA (0.85 eV), Zn-Ti/BEA (0.87 eV), and Zn-Sn/BEA (0.93 eV) can be potential candidates for the conversion of ethanol to butadiene. This work not only provides mechanistic insights into one-step catalytic conversion of ethanol to butadiene over Zn-Y/BEA catalyst but also offers more promising catalyst candidates for this reaction.     

Recent Advances on Confining Noble Metal Nanoparticles Inside Metal-Organic Frameworks for Hydrogenation Reactions

Hydrogenation reaction is one of the pillars of the chemical industry for the synthesis of drugs and fine chemicals. To achieve high catalytic performance, it is still highly desirable for constructing novel supported metal catalysts. Different from conventional supports like metal oxides, zeolites and carbon materials, metal-organic frameworks(MOFs) as the emerging porous materials have Hexhibited great potential to host metal nanoparticles (NPs) for achieving hydrogenation reactions with high catalytic efficiency, due to their unique porous structures. Recently, many progresses have been made, and thus, it is necessary to summarize the recent progresses on confining metal NPs inside MOFs for hydrogenation reactions. In this review, we first introduced the general synthesis methods for confining noble metal NPs inside MOFs. Then, the applications of noble metal NPs/MOFs catalysts in hydrogenation reactions were summarized, and the synergistic catalytic performances among noble metal NPs, metal nodes, functional groups, and pore channels in MOFs were illustrated. Subsequently, the hydrogen spillover effect involved in the hydrogenation reactions was discussed. Finally, we provide an outlook on the future research directions and challenges of confining noble metal NPs inside MOFs for hydrogenation reactions.     

Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks

The semihydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry. Unfortunately, state‐of‐the‐art heterogeneous catalysts hardly achieve high turnover frequencies (TOFs) simultaneously with almost full conversion, excellent selectivity, and good stability. Here, we used metal–organic frameworks (MOFs) containing Zr metal nodes (“UiO”) with tunable wettability and electron‐withdrawing ability as activity accelerators for the semihydrogenation of alkynes catalyzed by sandwiched palladium nanoparticles (Pd NPs). Impressively, the porous hydrophobic UiO support not only leads to an enrichment of phenylacetylene around the Pd NPs but also renders the Pd surfaces more electron‐deficient, which leads to a remarkable catalysis performance, including an exceptionally high TOF of 13835 h^?1, 100 % phenylacetylene conversion 93.1 % selectivity towards styrene, and no activity decay after successive catalytic cycles. The strategy of using molecularly tailored supports is universal for boosting the selective semihydrogenation of various terminal and internal alkynes.