镍-铁双金属催化剂在乙酸水蒸气重整制氢反应中的催化性能 --铁的互补作用和甲烷及CO生成的反应路径

本文研究了镍-铁双金属催化剂在乙酸水蒸气重整制氢反应中的催化性能。研究结果显示单金属铁催化剂对乙酸重整反应活性很低,但是对一氧化碳的中温变换反应有较好的催化性能。镍单金属催化剂对乙酸水蒸气重整制氢反应有非常好的初始催化活性,但是催化剂的长期稳定性很差。镍-铁复合催化剂的低温活性（623 K）和长期稳定性（100小时）都远好于单金属催化剂。这主要是因为铁的加入可以促进镍的分散,形成更多的表面活性位同时有助与防止镍的烧结。本研究也对乙酸重整反应中的两个主要气体副产物（一氧化碳和甲烷）的反应路径进行了分析。研究发现反应温度决定一氧化碳和甲烷的反应路径。673K是一个临界温度。低于此温度,甲烷的产生主要来自于一氧化碳和二氧化碳的甲烷化,而高于673K,甲烷主要来自于乙酸的直接裂解。对于一氧化碳副产物而言,低于673K其主要来自于乙酸的裂解或者不充分的水蒸气重整反应,而高于673K产生的一氧化碳则主要来自与逆水煤气变换反应。     

镍-铁双金属催化剂在乙酸水蒸气重整制氢反应中的催化性能——铁的互补作用和甲烷及CO生成的反应路径（英文）

我们研究了镍-铁双金属催化剂在乙酸水蒸气重整制氢反应中的催化性能.研究结果显示单金属铁催化剂对乙酸重整反应活性很低,但是对一氧化碳的中温变换反应有较好的催化性能.镍单金属催化剂对乙酸水蒸气重整制氢反应有非常好的初始催化活性,但是催化剂的长期稳定性很差.镍-铁复合催化剂的低温活性(623 K)和长期稳定性(100 h)都远好于单金属催化剂.这主要是因为铁的加入可以促进镍的分散,形成更多的表面活性位同时有助与防止镍的烧结.我们也对乙酸重整反应中的两个主要气体副产物(一氧化碳和甲烷)的反应路径进行了分析.研究发现反应温度决定一氧化碳和甲烷的反应路径.673 K是一个临界温度.低于此温度,甲烷的产生主要来自于一氧化碳和二氧化碳的甲烷化,而高于673 K,甲烷主要来自于乙酸的直接裂解.对于一氧化碳副产物而言,低于673 K其主要来自于乙酸的裂解或者不充分的水蒸气重整反应,而高于673 K产生的一氧化碳则主要来自与逆水煤气变换反应.     

Ni/ZrO2催化剂上甲烷水蒸气重整反应的研究

研究了Ni/ZrO2催化剂对甲烷水蒸气重整制合成气的反应性能。考察了催化剂的还原温度、载体焙烧温度以及反应温度、原料配比和空速等对催化剂性能的影响。利用XRD、TEM、XPS等手段对催化剂的织构形貌进行了表征。研究表明，Ni/ZrO2催化剂用于甲烷水蒸气重整制合成气不仅具有较高的活性，也具有较好的稳定性。水蒸气比增加，CH4转化率增大、CO选择性下降。CH4转化率及CO选择性均随空速增大而下降。使用10%Ni/ZrO2催化剂，在650 ℃、空速1.984×104 h－1、原料气配比H2O∶CH4∶N2=2∶1∶2.67的条件下，获得CH4转化率85%、CO选择性70%的结果。     

丙烯环氧化反应中TS-1催化剂失活研究

采用丙烯气相进料，在预混段中先与双氧水的甲醇溶液混合后进入固定床反应器，考察了进料液中pH值、丙二醇单甲醚、乙硫醇以及铁锈等对丙烯环氧化连续反应中TS-1分子筛催化剂性能的影响。结果表明，进料液体pH值对催化剂的催化性能有影响，适宜的进料液体pH值在7左右；副产物丙二醇单甲醚含量的增加不会对催化剂性能产生影响；乙硫醇量的增加使环氧丙烷选择性下降，但不会引起催化剂的失活；而进料液体中铁锈的引入会导致催化剂中部分孔堵塞，使催化剂部分失活。当进料液中的pH值用0.1mol/L的氨水调节为7左右，在反应温度55℃,反应压力0.7MPa，TS-1催化剂具有较好的稳定性，经130h的连续试验考察，双氧水的转化率和环氧丙烷的选择性约为90%。     

Cr/NaZSM-5催化剂上CO2氧化丙烷脱氢反应

以亚微米级NaZSM-5为载体合成了一系列负载型Cr催化剂, 采用氮气吸附、 XRD、 UV-Vis和H2-TPR对Cr/NaZSM-5催化剂的结构和织构性质进行了表征, 并评价了催化剂在CO2气氛下的丙烷脱氢性能. 硅铝摩尔比为60, Cr质量分数为3%的催化剂具有最高的反应活性, 于550 ℃反应10 min和8 h后的丙烷转化率分别为48.3%和30.1%, 丙烯选择性则分别为86.0%和91.8%. 催化剂中的Cr6+含量和反应初活性具有良好的对应关系, 表明高Cr6+含量对催化剂表现出高的丙烷脱氢活性是至关重要的. CO2气氛下的丙烯产率明显比氮气气氛下的高, 这是由于CO2气氛下催化剂表面有较多量的Cr6+, 并且CO2可通过逆水煤气变换反应除去脱氢反应生成的氢.     

La2O3/γ-Al2O3催化剂用于二甲醚二氧化碳重整制氢

采用等体积浸渍法制备了不同负载量的La₂O₃/γ-Al₂O₃催化剂,并考察了负载量和反应温度对催化剂用于二甲醚二氧化碳重整制氢反应的性能影响。结果表明,反应温度为550℃、La₂O₃负载量为15%时,催化剂表现出最好的性能：二甲醚的转化率为100%,二氧化碳的转化率达到85.4%,产物氢气的选择性高达93.3%,一氧化碳的选择性为76.04%,副产物甲烷的选择性仅为6.3%。550 ℃时其平均积炭速率为1.387 5 mg/（g·h）。研究还利用XRD、BET、TEM、TG等方法对催化剂进行了表征。     

Pt/MgO 催化剂上甲烷部分氧化制合成气反应

用浸渍法制备了Pt/MgO催化剂,并采用X射线衍射、X射线光电子能谱、透射电子显微镜和程序升温表面反应等技术对催化剂进行了表征.考察了催化剂对甲烷部分氧化制合成气反应的催化性能.结果表明,Pt/MgO催化剂具有较高的催化活性和选择性,甲烷转化率与合成气选择性在120 h内保持稳定.以金属状态存在的Pt对甲烷分解具有较高的活性,从而使催化剂对甲烷部分氧化反应具有较高的催化活性.活性组分Pt的存在状态和分散状态非常稳定,而Pt/MgO催化剂具有较强的抗积碳能力,使得催化剂在甲烷部分氧化制合成气反应中具有较高的稳定性.     

La_2O_3/γ-Al_2O_3催化剂用于二甲醚二氧化碳重整制氢

采用等体积浸渍法制备了不同负载量的La2O3/γ-Al2O3催化剂,并考察了负载量和反应温度对催化剂用于二甲醚二氧化碳重整制氢反应的性能影响。结果表明,反应温度为550℃、La2O3负载量为15%时,催化剂表现出最好的性能:二甲醚的转化率为100%,二氧化碳的转化率达到85.4%,产物氢气的选择性高达93.3%,一氧化碳的选择性为76.04%,副产物甲烷的选择性仅为6.3%。550℃时其平均积炭速率为1.387 5 mg/(g·h)。研究还利用XRD、BET、TEM、TG等方法对催化剂进行了表征。     

P/Rh比对PPh3-Rh/SiO2催化剂上丙烯氢甲酰化反应的影响

研究了P/Kh比对PPh3-Rh/SiO2催化剂上丙烯氢甲酰化反应性能的影响.结果表明,当P/Rh比为15时,丙烯氢甲酰化反应性能最好,丙烯转化率为25.9%,产物丁醛正异比为14,转换频率为241 h-1.PPh3-Rh/SiO2催化剂的固体31P核磁共振结果表明,在合成气气氛下,物理吸附的PPh3能够溢流到Rh/S...     

焙烧方法和焙烧条件对纳米Au/HZSM-5催化剂金粒径和催化性能的影响

采用负压沉积沉淀法制备了纳米Au/HZSM-5催化剂前体,研究了深床焙烧和等离子体焙烧两种方法,以及焙烧温度和焙烧气氛对催化剂中纳米金粒径和催化性能的影响,并采用ICP、TEM、XRD、UV-vis、XPS等表征方法对催化剂金粒子进行了物化性能表征,采用合成气羰基化制乙酸甲酯反应表征催化性能。结果表明,不同焙烧方法和不同焙烧温度及气氛对负载型纳米Au/HZSM-5催化剂中金粒径、形貌、物化性质和催化性能有明显影响。其中,以等离子体焙烧方法在500℃氮气气氛下制备的纳米1.86%Au/HZSM-5催化剂中的金粒径最小,为2-5 nm。用于催化合成气羰基化制乙酸甲酯反应,原料中CO的转化率为67%,乙酸甲酯选择性可达78%。     

One-pot Synthesis of Dimethyl Carbonate in the Presence of a Two-component Catalyst

The one-pot synthesis of dimethyl carbonate（DMC） with co-production of propy-lene carbonate（PC） and propylene glycol（PG） from propylene oxide（ PO）, carbon dioxide and methanol as the starting materials was investigated. The catalyst adopted here was a mixture of tetrabutyl ammonium bromide and sodium methoxide. It was found that un- der the reaction conditions of t = 150 ℃, p =3-4 MPa and 2 h, the PO conversion could reach 100%, the DMC, PC and the PG selectivities were 49. 7%, 42. 7% and 49. 8%, respectively, and the selectivity of by-products was below 10%.     

Differences in Reactivity of Epoxides in the Copolymerisation with Carbon Dioxide by Zinc-Based Catalysts: Propylene Oxide versus Cyclohexene Oxide

The homogeneous dinuclear zinc catalyst going back to the work of Williams et al. is to date the most active catalyst for the copolymerisation of cyclohexene oxide and CO₂ at one atmosphere of carbon dioxide. However, this catalyst shows no copolymer formation in the copolymerisation reaction of propylene oxide and carbon dioxide, instead only cyclic carbonate is found. This behaviour is known for many zinc‐based catalysts, although the reasons are still unidentified. Within our studies, we focus on the parameters that are responsible for this typical behaviour. A deactivation of the catalyst due to a reaction with propylene oxide turns out to be negligible. Furthermore, the catalyst still shows poly(cyclohexene carbonate) formation in the presence of cyclic propylene carbonate, but the catalyst activity is dramatically reduced. In terpolymerisation reactions of CO₂ with different ratios of cyclohexene oxide to propylene oxide, no incorporation of propylene oxide can be detected, which can only be explained by a very fast back‐biting reaction. Kinetic investigations indicate a complex reaction network, which can be manifested by theoretical investigations. DFT calculations show that the ring strains of both epoxides are comparable and the kinetic barriers for the chain propagation even favour the poly(propylene carbonate) over the poly(cyclohexene carbonate) formation. Therefore, the crucial step in the copolymerisation of propylene oxide and carbon dioxide is the back‐biting reaction in the case of the studied zinc catalyst. The depolymerisation is several orders of magnitude faster for poly(propylene carbonate) than for poly(cyclohexene carbonate).     

Comparative kinetic studies of the copolymerization of cyclohexene oxide and propylene oxide with carbon dioxide in the presence of chromium salen derivatives. In situ FTIR measurements of copolymer vs cyclic carbonate production

The catalysis of the reaction of carbon dioxide with epoxides (cyclohexene oxide or propylene oxide) using the (salen)Cr(III)Cl complex as catalyst, where H(2)salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexenediimine (1), to provide copolymer and cyclic carbonate has been investigated by in situ infrared spectroscopy. As previously demonstrated for the cyclohexene oxide/CO(2) reaction in the presence of complex 1, coupling of propylene oxide and carbon dioxide was found to occur by way of a pathway first-order in catalyst concentration. Unlike the cyclohexene oxide/carbon dioxide reaction catalyzed by complex 1, which affords completely alternating copolymer and only small quantities of trans-cyclic cyclohexyl carbonate, under similar conditions propylene oxide/carbon dioxide produces mostly cyclic propylene carbonate. Comparative kinetic measurements were performed as a function of reaction temperature to assess the activation barrier for production of cyclic carbonates and polycarbonates for the two different classes of epoxides, i.e., alicyclic (cyclohexene oxide) and aliphatic (propylene oxide). As anticipated in both instances the unimolecular pathway for cyclic carbonate formation has a larger energy of activation than the bimolecular enchainment pathway. That is, the energies of activation determined for cyclic propylene carbonate and poly(propylene carbonate) formation were 100.5 and 67.6 kJ.mol(-1), respectively, compared to the corresponding values for cyclic cyclohexyl carbonate and poly(cyclohexylene carbonate) production of 133 and 46.9 kJ.mol(-1). The small energy difference in the two concurrent reactions for the propylene oxide/CO(2) process (33 kJ.mol(-1)) accounts for the large quantity of cyclic carbonate produced at elevated temperatures in this instance.     

季铵盐功能化的钛硅分子筛催化丙烯氧化酯化合成碳酸丙烯酯

将有机卤素季铵盐以硅烷化键合方式嫁接到钛硅分子筛上,制备了兼备催化氧化烯烃合成环氧化物和环氧化物碳酸酯化反应的新型双功能催化剂,考察了其在丙烯、过氧化氢和二氧化碳一步合成碳酸丙烯酯的催化性能.研究表明,具有大外表面积的层剥离的钛硅分子筛是一种嫁接季铵盐合适的载体,丙基三丁基卤化铵是酯化催化性能优良的功能化基团,两者的偶合使一步法催化丙烯环氧化酯化合成碳酸丙烯酯的收率达48%.该催化剂具有较好的稳定性和重复使用性能.     

Mechanistic Aspects of a Highly Active Dinuclear Zinc Catalyst for the Co‐polymerization of Epoxides and CO2

The dinuclear zinc complex reported by us is to date the most active zinc catalyst for the co‐polymerization of cyclohexene oxide (CHO) and carbon dioxide. However, co‐polymerization experiments with propylene oxide (PO) and CO₂ revealed surprisingly low conversions. Within this work, we focused on clarification of this behavior through experimental results and quantum chemical studies. The combination of both results indicated the formation of an energetically highly stable intermediate in the presence of propylene oxide and carbon dioxide. A similar species in the case of cyclohexene oxide/CO₂ co‐polymerization was not stable enough to deactivate the catalyst due to steric repulsion.     

Multiple active motifs grafted on cyclotriphosphazene core: a novel catalyst for the chemical activation of carbon dioxide

A novel catalyst having multiple triphenylphosphonium chloride motifs on a single cyclotriphosphazene molecule has been developed for the chemical activation of carbon dioxide for the production of propylene carbonate from carbon dioxide and propylene oxide. The unique structure and multiple catalytic sites on a single framework are the prime factors, resulted in the enhanced catalytic activity and afforded high product yield.     

Homopolymerization of propylene oxide and copolymerization of propylene oxide and carbon dioxide with metal salts of acetic acid

The homopolymerization of propylene oxide was first conducted at 80°C in the absence of any solvent by using various metal salts of acetic acid and it was found that Mg(OAc)₂, Cr(OAc)₃, Mn(OAc)₂, Co(OAc)₂, Ni(OAc)₂, Zn(OAc)₂, and Sn(OAc)₂ were effective for the polymerization. The copolymerization of propylene oxide and carbon dioxide was next examined by using these effective metal salts of acetic acid as catalysts. Most of these were effective also for the copolymerization. The nature of the polymer obtained was strongly dependent on the catalyst used. Co(OAc)₂ and Zn(OAc)₂ gave an alternate copolymer of propylene oxide and carbon dioxide, Mg(OAc)₂, Cr(OAc)₃, and Ni(OAc)₂ gave a random copolymer, while Sn(OAc)₂ gave a homopolymer of propylene oxide. Then the copolymerization of propylene oxide and carbon dioxide was kinetically investigated in some detail by using Co(OAc)₂ as a catalyst. On the basis of the results obtained, a plausible mechanism was proposed for both the homopolymerization of propylene oxide and copolymerization of propylene oxide and carbon dioxide.     

KOH/4A分子筛催化剂对环氧丙烷、二氧化碳和甲醇合成碳酸二甲酯反应的催化性能

 首次开发出对环氧丙烷、二氧化碳和甲醇合成碳酸二甲酯反应具有较高活性和稳定性的KOH/4A分子筛固体催化剂,考察了反应温度和催化剂活性组分KOH的负载量等因素对催化剂性能的影响. 在优化的实验条件下,环氧丙烷可以完全转化,碳酸二甲酯的收率为168%. 从实验结果推测,产物碳酸二甲酯是由环氧丙烷和二氧化碳加成生成碳酸丙烯酯,然后与甲醇发生酯交换反应生成的,甲醇对环氧丙烷和二氧化碳合成碳酸丙烯酯反应具有助催化作用.     

Stereoselective Aromatic Ring Hydrogenation over Supported Rhodium Catalysts in Supercritical Carbon Dioxide Solvent

The combination of supported rhodium metal catalysts and supercritical carbon dioxide solvent was effective for the stereoselective ring hydrogenations of aromatic compounds at low temperature. Higher solubility of hydrogen in supercritical carbon dioxide provides higher concentration of hydrogen on the rhodium surface, but lower that of the intermediate on rhodium surface, which suppresses the flipping of surface intermediate, leading to higher catalyst activities and cis selectivities to the corresponding ring‐hydrogenated products as compared with those in organic solvents.     

Catalytic Formation of Propylene Carbonate from Supercritical Carbon Dioxide/Propylene Oxide Mixture

TheuseofsupercriticalcarbondioxideasasubstitUtesolventforchemicalsynthesisisaveryattractiveareainviewofresourceutiIizationandenvironmentalproblems"'.SinceCO2,whichhasaneasilyaccessibIecriticalpointwithaTcof3l.l'CandaPcof7.3MPa,isnontoxic,nonflammableandinexpensive,itcanreplacehazardousorganicsolventandtherebyprovideavaluablepollutionpreventiontool.Assimilartoothersupercriticalfluids,SC-CO,hasgaslikediffusitivityandliquidIikedensity,andchangingpressureandtemperaturecanvaryitsphysicalpro…