Use of a New Polymer Anchored Cu(II) Azo Complex Catalyst for the Efficient Liquid Phase Oxidation Reactions

A new polymer anchored copper(II) azo complex has been synthesized and characterized by using scanning electron microscope (SEM), thermogravimetric analysis (TGA), elemental analysis, atomic absorption spectroscopy (AAS) and spectrometric methods like diffuse reflectance spectra of solid (DRS) and Fourier transform infrared spectroscopy (FTIR). The immobilized Cu(II) catalyst shows excellent catalytic activity in oxidation of cyclohexene, styrene, benzyl alcohol and ethylbenzene in presence of tert-butylhydroperoxide (TBHP) as an oxidant. The effects of different solvents, oxidants, temperature, substrate oxidant ratio and amount of catalyst were also studied. The catalytic results reveal that the polymer-anchored Cu(II) azo complex catalyst can be recycled more than five times without appreciable loss in the catalytic activity.     

A Reusable Polymer-Anchored Palladium(II) Schiff Base Complex Catalyst for the Suzuki Cross-Coupling,Heck and Cyanation Reactions

A new polymer-anchored Pd(II) complex has been synthesized, characterized and its catalytic activity was investigated for the Suzuki cross-coupling reaction between aryl halides and arylboronic acid in the presence of K₂CO₃ as a base, for Heck olefination of aryl halides with alkenes, and for cyanation reaction of aryl iodides with K₄Fe(CN)₆ in presence of Et₃N as base. The key features of the catalyst include rapid reactions with excellent conversion without the use of phosphine ligands and total stability under the reactions conditions. The catalyst was recovered by simple filtration and reused five-times without significant loss of catalytic activity.     

MoS_2基催化剂上生物质基合成气制乙醇

生物质作为重要的可再生绿色能源,由于资源丰富,分布广泛,S、N含量低,CO_2零排放等优点,必将为实现可持续发展起到举足轻重的作用。乙醇作为一种最具潜能的汽油添加剂及化石燃料替代品,具有辛烷值高,无污染等优点。因此,催化生物质基合成气制乙醇作为可再生能源开发的途径之一,极具研究价值及工业价值。综述MoS_2基催化剂上生物质基合成气制乙醇的重要研究进展,指出利用合成气催化制乙醇的效率还有待进一步提高,尚未达到实际应用要求。改性MoS_2基催化剂对乙醇选择性较高,但烃类及CO_2副产物较多。为了促进乙醇的生成,今后合成气催化制乙醇应深入系统的研究碱金属和过渡金属共同促进的MoS_2基催化剂,并借助科学技术发展运用新方法和新思路,制备高效、稳定的催化剂。     

氯铝酸盐离子液体催化焦化碳九聚合制备苯并呋喃-茚树脂

考察了[Et3NH]Cl-2AlCl3离子液体催化焦化碳九馏分中苯并呋喃与茚的聚合反应,采用乙腈及吡啶为探针分子的红外光谱手段,研究了焦化碳九馏分中的杂质对催化活性的影响和催化反应的活性本质及反应机理,并考察了聚合反应初始温度及催化剂加入量. 结果表明,焦化碳九馏分中少量的酚类及碱性氮化物杂质是催化苯并呋喃与茚聚合反应的毒物,需对该馏分进行脱酚脱碱氮精制处理;该离子液体催化剂中的Br?nsted酸对反应具有较高的催化活性,具有反应速率快、聚合活性组分转化率高、树脂品质好的特点,在离子液体加入量1%(w)、常压、聚合起始温度45℃条件下聚合反应可在10 s内完成,苯并呋喃与茚转化率可达100%,得到软化点大于130℃、色号为2的浅黄色透明的高品质苯并呋喃-茚树脂.     

PVP相转移催化合成辛烯醛

以PVP（聚乙烯吡咯烷酮）为相转移催化剂,在常压下由正丁醛自缩合生成辛烯醛,研究了反应时间、PVP分子量及催化体系（由PVP和氢氧化钠水溶液组成）的配比等对反应转化率和目标产物选择性的影响。实验结果表明,PVP能够显著增加正丁醛在水中的溶解性,并能吸附催化体系中的OH^-进入有机相,提高反应的转化率和选择性。以PVPK25（MW=24000）为相转移催化剂时催化合成辛烯醛较为适宜条件为：在100mL0．5％的氢氧化钠水溶液中,反应组成（正丁醛质量：离子液体质量：氢氧化钠质量）配比为80：1．5：0．5,预热温度为70℃,常压反应25min,正丁醛的转化率和辛烯醛的选择性分别达到98．87％和98．59％。与目前工业上所采用的工艺相比,降低了反应温度和压力,提高了反应速率和辛烯醛选择性。     

合成乙酸异丁酯的催化剂研究进展

介绍了稀土金属氧化物、相转移催化剂、氨基磺酸、杂多酸、硫酸铁铵及无机盐等催化剂催化合成乙酸异丁酯的研究结果,其中氨基磺酸、杂多酸、硫酸铁铵、FeCl3·6H2O和CuCl2·2H2O的催化活性高,产品质量好。作者以硅胶负载四氯化锡为催化剂,合成乙酸异丁酯最佳反应条件为:乙酸为0.1mol,醇酸比为1.5∶1,催化剂用量为1.5g,反应时间为4h,反应温度150℃,最终转化率为93.87%。SnCl4/SiO2作为催化剂,活性高,选择性好,对设备无腐蚀,可重复使用。     

Investigation on catalytic distillation for ethyl acetate production with different catalytic packing structures

The catalytic packing is the core component of the catalytic distillation, and how the catalyst exists in the packing has significant influence on the process. To investigate the effect of catalyst packings on the catalytic distillation process, the classical ethyl acetate reactive distillation system was utilized, and a supported catalytic packing(SCP) was prepared in comparison with the conventional tea-bag catalytic packing(TBP). Laboratory scale experiments showed that the ethyl acetate conv...     

Trends in high pressure chemical reaction engineering

A review is given of trends in high pressure chemical reaction engineering. Besides homogeneous reactions, interest is focused mainly on heterogeneous catalytic conversion under conditions where the fluid phase is either in the liquid, gaseous, or supercritical state. The rate of catalytic surface reactions, mass transfer between catalyst and fluid phase, and/or transport processes inside porous catalysts can be influenced in manifold ways with the variation of pressure. Reaction engineering advantages for yield and selectivity of complex reactions, for in situ and inline regeneration, and for the prolongation of the lifetime of heterogeneous catalysts are discussed. Experimental techniques are also briefly summarized.     

New approach to environmentally benign epoxidation: the solid-phase-system using urea–H2O2 and recyclable dodecatungstate on apatite

On the basis of new concept using a solid disperse phase we have developed an efficient catalytic solid-phase-system for epoxidations of alkenes using urea–hydrogen peroxide (urea–H₂O₂) complex and cetylpyridinium dodecatungstate ((CetylPy)₁₀[H₂W₁₂O₄₂]) catalyst on fluorapatite (FAp). The recovered solid catalyst phase was reused to keep the catalytic activity after several times. In the conceptual idea it is a key point that in situ solid-phase-activation of the catalyst with urea–H₂O₂ proceeds to form microcrystals of the active species dispersed on the solid phase. The dispersion of the catalyst on FAp in the case of tungstic acid (H₂WO₄) was suggested by EPMA analysis. We proposed the peroxo type of species keeping the parent polyoxometalate framework as novel active species from FT-IR spectroscopic studies. FAp phase plays important roles of dispersing the active species on its surface to have high catalytic activity and of stabilizing the active species to lead to high reusability.     

Fatty acid methyl ester heterogeneous self‐metathesis in hydrophobic green solvent: Mass transfer limitations,catalyst recyclability,and stability

The role of room‐temperature ionic liquids (RTILs), [bmim][PF₆] and [bmim][Tf₂N], as reaction media regarding the catalytic activity and stability of methyltrioxorhenium (MTO) supported on ZnCl₂‐modified mesoporous Al₂O₃ has been studied for self‐metathesis of a functionalized olefin, methyl oleate. The humidity influence on the catalytic activity was probed. The catalyst recycling ability and the kinetics of the metathesis reaction using these RTILs were also investigated. It was found that the MTO‐based catalyst was efficient in viscous hydrophobic RTIL solvents. However, their high viscosity was found to increase the mass transfer limitations thus somewhat impacting the reaction kinetics. Nevertheless, better catalyst stability was reached allowing its possible recycling when used in RTIL media.     

Towards recycling purpose: Converting PET plastic waste back to terephthalic acid using pH-responsive phase transfer catalyst

Converting polyethylene terephthalate (PET) wastes to its monomer and valuable chemicals via eco-friendly chemical method is still a challenge task. Previously, phase transfer catalysts used for alkaline hydrolysis were soluble in reaction media and hardly separated after reaction. Here, we reported several pH-responsive catalysts combined alkyl quaternary ammonium units with heteropolyacid anion for achieving stepwise product/catalyst separation and catalyst recycling. The properties of homogeneous/heterogeneous transfer behavior allow catalyst to be easily separated from reaction media by adjusting of pH value. Among them, [C₁₆H₃₃N(CH₃)₃]₃PW₁₂O₄₀ (abbreviated as [CTA]₃PW) exhibits the highest activity and the most suitable pH responsive values. Such a pH triggered switchable catalytic system not only shows good performance for depolymerization of pure PET, but also some real PET wastes such as coloured trays and PE/PET complex films could be completely degraded into terephthalic acid. Additionally, the reaction kinetics and activation energy of PET alkaline hydrolysis also studied with and without pH-responsive [CTA]₃PW.     

Assessing the Recyclability of Supramolecularly Assembled Organocatalytic Species: A Theoretical Insight

Asymmetric organocatalytic synthesis is a powerful tool in organic chemistry to achieve desired stereoisomers in high purity via mild catalytic routes. The immobilization of homogeneous catalytic species onto heterogeneous phases embodies the evolution of asymmetric catalysis, since it allows the recycling of the catalyst for several runs until degradation. Previously reported non-covalent immobilization of proline-based catalysts for aldol reaction onto magnetic nanoparticles functionalized with β-cyclodextrin (MNP-β-CB) demonstrated the viability of the methodology. This paper proposes two new catalyst recycling strategies based on Cucurbit[7]uril (CB[7]) for the aldol reaction and the Robinson annulation. These recycling methodologies are conceptually different. The former relies on the homogeneous encapsulation of the catalyst in cucurbituril, CB[7] ⋅ Cat, and its recycling in the aqueous phase by extraction of the aldol product with organic solvents. The latter relies on the heterogeneous encapsulation of the catalyst as MNP-CB[7] ⋅ Cat2 system and its recycling by magnetic harvesting. Density functional theory (DFT) calculations have been employed to rationalize the thermodynamics of experimental results, and to suggest caveats and plausible improvements in view of a future catalytic design.     

Evaluation of catalytic efficiency of a triple-site phase transfer catalyst and the kinetics of dichlorocarbene addition to 5-vinyl-2-norbornene

A new triple-site phase transfer catalyst viz., 1,3,5-tris(ethylmethyleneammonium bromide)-2,4,6-trimethyl benzene (TEMABTB) was prepared by the quaternization of 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene using triethylamine and its catalytic efficiency was ascertained by following the kinetics of dichlorocarbene addition of 5-vinyl-2-norbornene. Comparative catalytic activity of various onium salts (single-, di- and tri-site) have been investigated in detail. Based on the kinetic results obtained, a plausible mechanism has been proposed.     

A new application of the yeast two-hybrid system in protein engineering

Cytochromes P450 are involved in the biosynthesis of steroid hormones in mitochondria of the adrenal gland. The electrons required for these reactions are provided via a redox chain consisting of adrenodoxin reductase (AdR) and adrenodoxin (Adx). A prerequisite for a fast and efficient electron transfer as well as high catalytic activity is the formation of functional complexes between the different redox partners. To improve the protein-protein interactions by directed evolution, we developed a new in vivo selection system. This high-throughput screening method is based on the yeast two-hybrid system. It enables a background-free screening for increased protein-protein interactions between stable and functional species including cofactor-containing proteins (FAD, [2Fe-2S], heme). The method was successfully applied for the directed evolution of Adx and selected variants were analyzed biochemically and biophysically. All analyzed proteins exhibit typical characteristics of [2Fe-2S]-cluster-type ferredoxins. Adx-dependent substrate conversion assays with different cytochromes demonstrated that the improved ability of the mutants to form complexes results in an enhanced catalytic efficiency of the cytochrome P450 system.     

非热等离子体催化转化C1分子及其催化剂研究进展

非热等离子体催化具有反应条件温和、启动快和反应器结构紧凑等特点,在C₁分子催化转化领域（如CO₂加氢、甲烷活化、水煤气变换反应和甲醇重整制氢）有着广阔的应用前景。具体来说,等离子体特有的高能电子可在气相中快速活化稳定性极强的C₁分子并生成活性物质,接着与催化剂结合发生表面化学反应,从而实现常温常压下C₁分子的高效转化。然而,等离子体与催化剂之间的协同作用机制以及催化机理极为复杂,仍有待进一步研究。本综述简单介绍了非热等离子体催化转化C₁分子的近期研究进展,重点探讨了适用于非热等离子 体的催化剂研究以及催化机理的高级原位表征。最后,提出了非热等离子体催化转化C₁分子的未来发展方向：①设计并构筑适用于非热等离子体催化的高效催化剂,并研究其构效关系;②发展高级原位表征技术,揭示活性物质的作用机理以及催化机理;③设计并构建高效的等离子体催化反应器,并建立反应器的理论模型和数值模拟方法,科学指导等离子体反应器的设计、优化和放大。     

Nano-Structured Metal Chalcogenides as Reagents for the Catalytic Carbon–Sulfur Bond Formation in Cross-Coupling Reaction

A new approach for the catalytic carbon–sulfur bond formation via cross-coupling reaction is reported. For the first time nano-structured nickel organosulfides [Ni(SAr)₂] _n were used as a source of SAr groups in catalytic cross-coupling reaction. A unique effect of morphology control of the reactivity of SAr groups in cross-coupling reaction was found. Synthesized nano-structured particles were characterized by field-emission scanning electron microscopy and their reactivity was studied by NMR in solution. Cross-coupling reaction with Cu catalyst was shown to proceed in the liquid phase and involve leaching, whereas the reaction with Pd catalyst is more complex and may involve both—homogeneous and heterogeneous pathways.     

PERFORMANCE OF A PACKED-BED REACTOR

We examined the conversion rates in a packed bed catalytic reactor with a two phase upward flow in a wide range of operating conditions. The oxidation of ethanol to acetic acid in the liquid phase on a Pd-Alumina catalyst was chosen as the test reaction.

Global reaction rates were measured by changing gas velocities, temperature, and feed concentrations of ethanol in the liquid phase. The observed rates were compared with those calculated using two models, assuming a total external wetting of the catalyst. In the first model, a “kinetic” conversion rate was calculated by neglecting any interphase mass transfer resistance. In the second model the interphase mass transfer resistance was considered and expressed by an overall coefficient evaluated from published correlations. The results show that there is an hydrodynamic influence, probably due to the mass transfer and/or to the partial effective wetting of the catalyst. Mass transfer, on the other hand, is better than that observed in other cases. A comparison with the performances of a downflow trickle-bed reactor operating at the same tested conditions showed a much smaller influence of mass transfer and hydrodynamics on the overall conversion rate for the upflow reactor.     

Oxovanadium (IV) Schiff base complex immobilized on CPS microspheres as heterogeneous catalyst for aerobic selective oxidation of ethyl benzene to acetophenone

In this work, chloromethylated crosslinked polystyrene microspheres (CMCPS microspheres) were used as starting carrier, and a new immobilized bidentate Schiff base oxovanadium (IV) complex catalyst was prepared. The chloromethyl groups of CMCPS microspheres were first transformed into aminomethyl groups via Delepine reaction with hexamethylene tetramine (HMTA) as reagent, obtaining aminomethylated (AM) microspheres AMCPS. And then the Schiff base reaction between the primary amino group of AMCPS microspheres and salicylaldehyde (SA) was allowed to be conducted, resulting in Schiff base-type resin microspheres, SAAM-CPS, on which bidentate Schiff base ligand SAAM were chemically anchored. Subsequently, the coordination reaction between the ligand SAAM of SAAM-CPS microspheres and vanadyl sulfate (VOSO₄) was carried out, obtaining a new immobilized bidentate Schiff base-type oxovanadium (IV) complex, CPS-[VO(SAAM)₂] microspheres, namely a new heterogeneous oxovanadium (IV) complex catalyst was prepared. On the basis of fully characterizing the microspheres CPS-[VO(SAAM)₂], they were used in the catalytic oxidation of ethyl benzene with molecular oxygen. The experimental results show that in the oxidation reaction of ethylbenzene with molecular oxygen as oxidant, the heterogeneous oxovanadium (IV) complex catalyst, CPS-[VO(SAAM)₂], has high catalytic activity and excellent catalytic selectivity. Under the mild conditions such as at ordinary pressure of dioxygen and at a relatively low temperature of 110 °C, ethyl benzene can be transformed to acetophenone as a single product with a yield of 43%. It was found that the reaction temperature and the used amount of the solid catalyst effect on the oxidation reaction greatly. The catalyst CPS-[VO(SAAM)₂] has excellent recycle and reuse property.     

Hydroformylation of mixed octenes catalyzed by supported rhodium-based catalyst

In order to solve the difficult separation between catalyst and products in homogeneous system, the activated carbon (AC)-supported rhodium-based catalyst (Rh/AC) was prepared. Hydroformylation of mixed octenes catalyzed by Rh/AC was studied, and compared to that catalyzed by RhCl(CO)(TPPTS)₂ [TPPTS: trisodium salt of tris(m-sulphonylphenyl) phosphine], and [Rh(CH₃COO)₂]₂-Ph₃PO (Ph₃PO: triphenyl phosphine oxide). The performance test of the catalysts showed the Rh/AC presented higher catalytic activity, selectivity and air-stability. During the recycle experiments Rh/AC could be used 4 times without significant loss of rhodium. The effects of the supports, rhodium loading and reaction conditions on the catalytic performance of Rh/AC were investigated. The results showed petroleum coke-based activated carbon with higher surface area and more basic groups was advantageous to the formation of aldehydes. The heterogeneous Rh/AC catalyst displayed higher catalytic activity and reusability.     

CuO／Ce1-xZrxO2催化分解NO的研究

NO对环境的影响日益严重,如果不有效将其消除掉,将会对环境及人的健康产生极大的危害。因此,目前各国都在研究廉价消除NO污染的方法。采用共沉淀法制备了催化剂CuO／Ce1-xZrxO2,利用XRD对其晶相进行表征,H2-TPR研究了其氧化还原能力,以NO的转化效率作为评价指标。结果表明：适当比例zr的加入以及适当比例的CuO能提高活性。