无机方法制TS-1催化环己酮氨氧化反应

用无机方法合成了钛硅分子筛催化剂TS-1,并优化了TS-1催化环己酮氨氧化反应的条件。结果表明：无机催化剂可以取代有机催化剂。物料比、溶剂以及温度都对氨氧化反应有很大的影响。其优化的反应条件：NH。酮摩尔比为2．00,H2O2酮摩尔比为1．50,溶剂用蒸馏水且H2O酮摩尔比为7．5,反应温度为74℃。     

TS-1/H2O2催化氧化体系在超临界CO2中应用的研究

对超临界CO2条件存在时TS-1／H2O2氧化体系进行了研究。所选择的反应分别是苯乙烯的氧化和叔丁醇的氧化。实验结果表明,TS-1可以在超临界CO2中保持较高的活性和选择性,但反应结果都不如无超临界CO2存在时的情况。其中对于苯乙烯氧化反应,H2O2的有效利用率可以达到78．4％以上;而对于叔丁醇氧化,H2O2的利用率则较低。经分析认为,这是由于H2O2水溶液和超临界CO2的相容性较差,在TS-1／H2O2氧化体系中引入超临界CO2条件造成负面影响。     

TS-1催化H2O2与甲基氯丙烯环氧化

以TS-1为催化剂，以30％（质量分数）H2O2为氧化剂催化2-甲基-3-氯丙烯（MAC）环氧化，考察了溶剂种类与用量、反应温度、反应物摩尔配比及催化剂TS-1质量浓度等因素对环氧化反应的影响。结果表明，反应的最佳溶剂为甲醇；增加催化剂质量浓度和升高反应温度均有利于提高转化率和H2O2有效利用率，但同时降低了反应的选择性；从反应物摩尔配比兼顾反应的转化率和H2O2有效利用率两方面来考虑，本试验条件下选1：1为佳。     

钛硅分子筛TS-1催化烯烃环氧化反应的研究进展

TS-1催化的烯烃环氧化反应具有条件温和、环境友好、符合绿色化学理念、应用前景广阔等优点.该文首先介绍了不同介质中TS-1催化过氧化氢(H2O2)氧化脂肪烯烃反应的进展,结果表明,在甲醇等质子溶剂中,溶剂可以和Ti—OOH(钛氧活性中心)通过氢键作用形成活性中间体,实现烯烃的环氧化;同时,TS-1的酸中心易引发环氧化物开环、聚合等副反应,适量的碱性添加剂可减少酸性位点,抑制副产物生成,提高环氧化产物的选择性.其次,采用酸改性、碱改性、硅烷化改性或金属盐改性等方法可改善TS-1的催化性能.积炭是TS-1失活的主要原因,高温焙烧、原位H2O2氧化或热溶剂洗涤可基本恢复TS-1的活性.最后指出:探索TS-1新的合成与改性方法以及再生方法与TS-1活性的关系是该领域未来的发展方向.     

TS-1型钛硅分子筛催化H_2O_2/O_3降解乙酸

研究了pH=2.8条件下H2O2和TS-1对臭氧化降解乙酸效率的影响。实验结果表明,在臭氧化过程中同时加入钛硅分子筛TS-1和H2O2是乙酸得到有效降解的必要条件。H2O2与钛硅分子筛TS-1作用形成超氧物种是臭氧化效率提高的主要原因,而且臭氧在催化剂表面的吸附分解是乙酸降解的速率控制步骤。根据作用机理推导建立了乙酸降解的假零级动力学方程,其中1/CO3＊和1/khete呈线性关系,以上结论与实际实验结果有着很好的一致性。     

TS-1催化氯丙烯环氧化反应过程中的溶剂效应

研究了具有不同官能团的溶剂对TS-1催化氯丙烯环氧化反应性能的影响,发现与无溶剂的反应结果相比,含羟基的溶剂和丙酮对反应有明显的促进作用,在含氰基的乙腈溶剂中,环氧化反应效果变差。试验中还发现,溶剂分子的空间结构影响环氧化的反应速率,并且部分溶剂会与氯丙烯发生竞争性氧化,降低H2O2的有效利用率。在甲醇或丙酮溶剂中混入一定比例的乙腈可提高产物的选择性,但对提高催化剂稳定性效果不显著。     

醇溶剂中TS-1催化丙烯环氧化的本征动力学与反应机理研究

研究了在三种不同醇溶剂(甲醇、异丙醇和仲丁醇)水溶液中TS—l催化丙烯过氧化氢环氧化反应的本征动力学，反应条件为温度30～60℃，丙烯压力0．4-0．6MPa。根据实验现象和各组分在TS-1上的吸附特点建立了该反应的Eley-Rideal机理模型，环氧化反应在吸附态的H2O2分子与游离态的丙烯分子之间进行，表面反应为速度控制步骤。通过实验数据对机理模型进行了参数估值，检验结果表明拟合效果较好，平均偏差在10％以内。最后对过程进行了进一步讨论，为该过程的工业化提供了依据。     

异丙醇的O3/H2O2复合氧化动力学研究

采用停流光谱仪研究了异丙醇在T=298K和pH=3～11范围内O3 / H2O2复合氧化的反应动力学.结果表明异丙醇的O3 / H2O2复合氧化反应动力学随反应体系的pH值不同而不同.在酸性和中性条件下,反应相对于O3浓度、异丙醇浓度都为1级;在碱性条件下,异丙醇较容易被O3/H2O2复合氧化降解,总反应级数为2级,相对于O3浓度、异丙醇浓度和H2O2浓度分别为1级、0级和1级,可见异丙醇的降解速率与它的浓度无关.在T=298K,当pH值从9增大到11, 反应速率常数从3486.1(mol·L-1)-1·s-1增大到38239.2(mol·L-1)-1·s-1. 表明在酸性条件下,异丙醇的O3/H2O2复合氧化是O3分子直接攻击异丙醇的反应占主导;在碱性条件下,自由基型反应占主导.     

超微粒介孔分子筛Ti-MCM-41的制备及苯乙烯催化氧化的研究

在强酸性条件下，在60℃水浴中，以无水乙醇和异丙醇为混合溶剂，合成了nSi)：n(Ti)分子比为30的超微粒介孔分子筛蜀-MCM-41。在超微粒介孔分子筛Ti-MCM-41和H2O2作用下，对苯乙烯进行催化氧化的反应，其产物是苯乙酮和苯甲醛，并且考察了分子筛Ti-MCM-41不同用量、H2O2和苯乙烯不同分子比、反应时间及反应温度对苯乙烯转化率的影响。实验结果表明，在苯乙烯催化氧化反应中，反应的最佳温度为60℃，最佳时间是10h，最佳分子筛用量是0．6g，n(H2O2)：n(苯乙烯)分子最佳比是4：1。由于H2O2氧化后的产物是H2O2，因此，这种清洁的方法是今后有机合成发展的趋势。     

Al-TS-1催化1-己烯环氧化合成1,2-环氧己烷

以H2O2为氧化剂,Al-TS-1为催化剂催化1-己烯环氧化合成了1,2-环氧己烷。研究了Al含量和溶剂对反应的影响,筛选出较合适的催化剂Al-TS-1(SiO2/Al2O3=616)。采用甲醇为溶剂时,Al-TS-1表现出较低的催化活性和选择性;而采用乙腈为溶剂时,Al-TS-1表现出较高的催化活性和选择性。说明掺杂Al3+后,TS-1的疏水性发生了改变,乙腈溶剂的采用可能改变了反应的历程。     

Selective catalytic oxidation of aniline to azoxybenzene over titanium silicate molecular sieves

The oxidation of aniline using aqueous H₂O₂ and titanium silicates, TS-1 and TS-2 as catalysts was carried out in a batch reactor in the temperature range 333–353 K. TS-1 catalyzes aniline selectively to azoxybenzene and is superior to TS-2. The influence of different solvents, concentration of H₂O₂ and the catalyst in the reaction mixture on the conversion and product distribution has been studied. Acetonitrile is a suitable solvent in this reaction, while acetone is not. For the TS-1 catalyzed oxidation reaction,t-butyl hydroperoxide is not a suitable oxidant. At optimum conditions, a H₂O₂ efficiency of about 100% for aniline conversion is obtained with a selectivity of 97% to azoxybenzene in the product.     

Kinetics of oxidation of ammonium sulfite by rapid-mixing method

The kinetics of the reaction of oxygen with ammonium sulfite in aqueous solution have been studied by the rapid-mixing method of Hartridge and Roughton at 30°C. The rate of oxidation of ammonium sulfite was found to be approximately twice as low as that of sodium sulfite.The experimental findings showed that the reaction rate was zero order with respect to oxygen and three-halves order with respect to sulfite, and the promoting effect of cobalt ions was proportional to the square root of the total concentration of cobalt added to the reacting solution. The apparent activation energy for the overall oxidation was calculated to be 21·5 kcal per gmole.A reaction mechanism has been proposed and a rate expression derived is in good agreement with the experimental data.     

Solvent effects in the epoxidation reaction of 1-hexene with titanium silicalite-1 catalyst

The epoxidation of 1-hexene with titanium silicalite-1 (TS-1) catalyst was investigated to gain insight into the effect of the solvent on the observed reactivity. Three different solvents were examined: methanol, acetonitrile, and acetone. Kinetic data were obtained from batch reaction experiments, with an emphasis placed on gathering more accurate initial rates than those reported in the literature. The dependencies of the rates on the concentrations of 1-hexene, water, and hydrogen peroxide were determined. The adsorption behavior of 1-hexene in TS-1 in the three different solvents was determined independently by batch sorption experiments. Results showed that the solvent has a significant effect on the adsorption of 1-hexene, and hence on the reaction kinetics. Kinetic modeling incorporating experimental and simulated quaternary adsorption isotherms to describe quasi-equilibrated steps revealed that the differences in the observed reaction kinetics may be attributed mostly, but not entirely, to differences of the partitioning of 1-hexene between the bulk and intraporous phases among the three different solvents.     

Catalytic mechanism and reaction pathway of acetone ammoximation to acetone oxime over TS-1

A series of two-step reactions and several special experiments were designed and carried out to discover the reaction pathway of acetone ammoximation to acetone oxime over titanium silicalites-1 (TS-1) employing 25 wt% ammonia and 30 wt% hydrogen peroxide as the ammoximation agents. The experimental results show that the acetone oxime can form even if there is no direct contact between acetone and TS-1 catalysts, indicating the hydroxylamine route may be the most important catalytic mechanism for the reaction. HPLC, GC/MS and ion chromatography characterization results show that hydrogen peroxide can oxidize acetone oxime to acetone, nitrite and nitrate in the presence of TS-1. In addition, nitrite and nitrate can form in the reaction of H₂O₂ and NH₃ over TS-1. Based on these results, a possible overall reaction pathway of acetone ammoximation over TS-1 has been proposed.     

The role of the solvent in TS-1 chemistry: active or passive? An early study revisited

The oxidation of n-hexane with hydrogen peroxide, catalyzed by TS-1 in various solvents, is reported. The initial rate of reaction decreases in the order: t-butanol > t-butanol/water > methanol acetonitrile water, whereas the reverse trend was observed for the adsorption of n-hexane in the catalyst. A dual function is postulated for the solvent in relation to its effects on kinetics. It assists the sorption/desorption of reagents/products in TS-1 (passive role) and participates in the catalytic cycle, through interactions with polar species involved in it (active role). A mechanistic pathway for the hydroxylation of paraffinic and aromatic C–H bonds is suggested.     

Epoxidation of allyl alcohol to glycidol using titanium silicalite TS-1: effect of the reaction conditions and catalyst acidity

The epoxidation of allyl alcohol to glycidol using the titanium silicalite TS-1 with hydrogen peroxide as the oxidant is described and discussed in detail. The reaction conditions (alcohol, solvent, temperature) required to obtain 100% selectivity to glycidol are described and this selectivity has been observed at conversions of allyl alcohol of up to 20%. Addition of excess hydrogen peroxide enhances conversion but does not appear to affect selectivity to glycidol deleteriously, whereas addition of hydrogen peroxide over an extended time period is not particularly beneficial. The major side reactions are the oxidation of the alcohol solvent and the ring opening solvolysis of the glycidol that leads to the formation of alkoxy diols. Base treatment of the TS-1 using sodium azide enhances the glycidol selectivity, whereas the incorporation of Brønsted acid sites by addition of aluminium into the framework structure of TS-1 enhances the selectivity to the products of solvolysis ring opening reactions.     

Liquid‐Phase Hydrogenation of m‐phenoxybenzaldehyde to m‐phenoxybenzylalcohol Using Raney Nickel Catalyst: Reaction Kinetics

Kinetics of the liquid‐phase catalytic hydrogenation of m‐phenoxybenzaldehyde to m‐phenoxybenzyl alcohol have been investigated over the Raney nickel catalyst. Effects of hydrogen partial pressure (500‐2000 kPa), catalyst loading (1.6‐6.4 g.L^?1), m‐phenoxybenzaldehyde concentration (0.2‐0.8 mol.L^?1) and temperature (333‐363 K) on the progress of the reaction were studied. The speed of stirring > 15 rps has no effect on the initial rate of reaction. Effects of various catalysts and solvents on the hydrogenation of m‐phenoxybenzaldehyde have been investigated. The reaction was found to be first order with respect to the hydrogen partial pressure, catalyst loading and m‐phenoxybenzaldehyde concentration. Several Langmuir‐Hinshelwood type models were considered and the experimental data fitted to the model involving surface reaction, between dissociatively adsorbed hydrogen and molecularly adsorbed m‐phenoxybenzaldehyde.     

One-Step Synthesis of Isoamyl Butyrate from Isoamyl Alcohol and n-Butyraldehyde over TS-1 in Air

A one-step synthesis of isoamyl butyrate from isoamyl alcohol and n-butyraldehyde over TS-1 in air is reported. Higher aldehyde conversion and better selectivity are obtained. The mechanism of reaction over TS-1 is also investigated.     

MONOLITHIC CATALYSTS: DIFFUSIONAL MASS TRANSFER OF CO THROUGH Y-ALUMINA SUBSTRATES UNDER REACTING CONDITIONS

Experimental kinetic data have been obtained for the CO oxidation reaction over laboratory made platina-rhodium monolithic catalyst. Inert layers of y-yalumina were deposited over the active layer in order to elucidate the diffusional effects on the monolithic catalyst. A synthetic gas mixture consisting of CO₁, O₂ and N₂ was the feed of an integral tubular reactor between 180 and 370°C. A first order kinetic rate expression with respect to CO concentration, which includes an inhibition term of second order was found to fit the experimental data via a model which also accounts for diffusional resistances. The obtained kinetic and diffusional data can be used in the design of a catalytic converter with improved efficiency. The results can also be used to interpret the diffusion mechanism inside the catalyst itself and it was concluded that Knudsen diffusion mechanism prevails.