Effect of Preparation Method on the Physicochemical Properties of MoVNbTe Catalyst for Propane Ammoxidation to Acrylonitrile

MoVNbTe catalyst has been found to be the most active and selective catalyst in the ammoxidation of propane to ACN, the selective oxidation of propane to acrylic acid and in the oxidative dehydrogenation of ethane to ethylene. However, in our previous work, when 0.5 mL of MoVNbTe catalyst prepared using slurry method was tested in the propane ammoxidation to ACN, it only shows 1% conversion of propane with about 55% selectivity to CAN, thus giving only 0.6% yields to ACN. The poor catalyst activity is attributed to insufficient formation of crystalline phases essential for the propane activation process. In an attempt to improve the physicochemical properties of this catalyst, several preparation methods have been used, namely hydrothermal, reflux, changing the solvent and changing the calcinations temperature. The modified catalysts have been characterized using X-Ray Diffraction （XRD） and N2 physisorption （BET）. The MoVNbTe catalyst prepared by hydrothermal method shows a remarkable improvement in the formation of crystalline phases.

Ammoxidation of Substituted Toluenes on Silica-Supported VPO Catalysts

The ammoxidation of substituted toluenes to their corresponding nitriles over silica-supported vanadium phosphorus oxide (VPO/SiO2) catalysts has been studied. the effects of carrier silica, the addition of phosphorus, the substituents and the loadings have been discussed. Compared with unsupported VPO, the VPO/SiO2 catalysts have higher catalytic activity for ammoxidation of substituted toluenes and much lower reaction temperature. XRD shows that vanadium phosphorus oxides exist as amorphous phase and disperse to a high degree on the silica surface in 10%loading catalyst. When the loadings are over 10%, the crystalline α-VOPO4 would emerge, which would decrease the yield and selectivity. Additional phosphorus can form composite oxides with vanadia and play concerted catalytic function, which increase the selectivity of nitriles remarkably. Different substituents or same substituents on different positions have different influences because of the variant electronic stability of intermediates, the hindered accessibility of methyl group or the chemisorption state of the substrate molecule on the electrophilic catalyst surface.

Effect of reduction-oxidation treatment on the properties of VSb_3W-Al_2O_3 catalyst for propane ammoxidation

VSb3W-Al2O3 catalysts for propane ammoxidation were prepared by the conventional slurry method and new slurry method,namely,the reduction-oxidation slurry method.The effect of preparation methods on the physicochemical properties of VSb3W-Al2O3 catalysts were studied by N2 adsorption,XRD,XPS and Raman spectroscopy,and their catalytic performance for the ammoxidation of propane to acrylonitrile were tested.Compared with the VSb3W-Al2O3 catalyst prepared by the conventional slurry method,the VSb3W-Al2O3 catalyst prepared by the reduction-oxidation slurry method exhibited better propane conversion and acrylonitrile selectivity.This is due to that the reduction-oxidation treatment was advantageous for obtaining low valence state vanadium and high valence state antimony to form more rutile SbVO4,which is a vital active phase for propane ammoxidation.

Sepiolite supported catalyst multicomponent metal oxide for ammoxidation of propane

Natural sepiolite was treated with HCl solution to change its surface and internal structure and the structure of sepiolite was cracked to produce SiO2 when the concentration of HCl is more than 2 mol/L. The Mo-Bi-Fe-Co-V-Sb-O/sepiolite catalyst was prepared through impregnationprecipitation method and characterized by means of X-ray diffraction, scanning electron microscopy and energy dispersive spectrum techniques. The effects of temperature, volume fractions of NH3 and O2, and space velocity of feed gas on catalytic activity were evaluated in a fixed bed reactor. The results show that propane conversion of 82% and selectivity to acrylonitrile of 38% can be obtained at 490 ℃, V（C3H8）∶V（NH3）∶V（O2）=1.00∶1.05∶2.50 and space velocity of 3 000 cm3·g-1·h-1.

Commercial Application of the XYA-5 Catalyst in Acrylonitrile Unit

The XYA-5 catalyst was first applied in commercial scale on an 80-kt/a acrylonitrile unit at the Daqing Refining and Chemical Company. Test results had shown that the once-through yield of acrylonitrile exceeded 80% with the unit consumption ofpropylene reaching 1032 kg on each ton of acrylonitrile. The product quality could be easily put under control and the distribution of reaction products was reasonable with good cleaning performance and stability of the catalyst that was suitable for use on this commercial unit.

2-Cyanopyrazine Prepared from 2-Methylpyrazine by Catalytic Ammoxidation on MoVPO Catalyst

The mechanism of 2-cyanopyrazine prepared from 2-methylpyrazine （2-MP） by catalytic ammoxidation has been explained by the theory of appropriate structure of group. A new catalyst of MoVPO was developed. The effects of catalyst promoter phosphorus and supports were investigated. The catalyst containing P, V and Mo in molar ratio of 1.4 ： 1 ： 0.02 and supported on activated alumina and prepared by impregnation method exhibits good activity and selectivity. Reaction factors such as reaction temperature, space velocity, feed composition and service life of catalyst were investigated. Optimum reaction conditions （the volume space velocity of 0.2h-1, the reaction temperature of 380 ~C and molar ratio of 1 ： 7.8 ： 8 ： 8 for 2-MP, water, oxygen and ammonia） were obtained. Selectivity of 93% and yield of 86% could be achieved under these conditions.

Monte Carlo Simulation of Propylene Selective Oxidation and Ammoxidation overβ-Bi2Mo2O9 Catalyst under Anaerobic Condition

A random walk Monte Carlo （RWMC） simulation model of catalytic particle was established on the basis of the structures of bismuth molybdate catalysts and mechanisms of catalytic reactions with propylene selective oxidation and ammoxidation. The simulation results show that rationality of the RWMC model is proved on the basis of pulse experimental data. One of the most remarkable factors affecting catalytic behavior is the transfer of bulk lattice oxygen, which decides the rate of ammonia-consuming and propylene-consuming. The selectivity of main products reaches the maximum after the reduction of catalysts to a certain degree. It is inferred that catalytic performance improves greatly if the ratio of capacity for dehydrogenation from adsorbed propylene molecule on catalytically active site of molybdenum metal-imido group （Mo=NH） to that on catalytically active site of molybdenum metal-oxo group （Mo=O） becomes much higher.

Ammoxidation of 3-Picoline over V-Mo-P Oxide Catalyst Prepared from 11-Molybdo-l-Vanado Phosphoric Acid

V-Mo-P oxide catalyst system was directly prepared from ll-molybdo-l-vanado phosphoric acid by thermal decomposition. Supported V-Mo-P oxide catalysts were prepared by wet impregnation method. Catalysts were characterized by FTIR （Fourier transform infrared）, XRD （X-ray diffraction） and TPD （temperature programmed desorption）. The catalytic activity of V-Mo-P oxide catalysts were investigated for vapour phase ammoxidation of 3-picoline. The unsupported catalyst showed 92.1% yield where as V-Mo-P oxide/HZSM-5 showed the highest yield （80.4%） amongst the supported catalysts.

STUDY ON THE POLYMERIZATION OF ACRYLONITRILE INITIATED BY POLYPROPYLENE-BASED VANADYL POLYIMIDODIACETATE——THIOUREA REDOX SYSTEM

The present paper deals with the kinetics of polymerization of acrylonitrile (AN) initialed by the redox system of polypropylene-based vanadyi polyimidodiacetate (PV)-thiourea (TU)in aqueous sulfuric acid in the temperature range from 25 to 40℃. The polymerization rate was measured by varying the concentrations of monomer, vanadyl polyimidodiacetate, thiourea and sulfuric acid. The overall rate of polymerization was summarized asRp=2.2×10~5e^(-6.560/RT) [AN]^(1.0)[PV]^(0.50)[TU]^(1.5)[H_2SO_4]^(2.0)The molecular weight of polyacrylonitrile based on the experimental data was:(?)=k 1/T [pv]^(0.50)[TU]^(1.5)[H_2SO_4]^(2.0)These results indicated that the chain radicals are terminated by combination and/or disproportionation rather than chain transfer. The cooperation effect of carboxylic groups and the macromolecular field effect of polymer supporter are the characters of vanadyl polyimidodiacetate such as the case reported in early paper.

"CAGE" VANADYL POLYCARBOXYLATE-THIOUREA COMPLEX FOR THE POLYMERIZATION OF ACRYLONITRILE

The polymerization of acrylonitrile (AN) in aqueous nitric acid initiated by ' cage ' vanadyl polycarboxylate (P=VO)-thiourea (TU) complex was investigated. The overall rate ofpolymerization isThe relationship between the induction period (τ) and the temperature of polymerization as well as the concentrations of reactants can be expressed as follows :The molecular weight of polyacrylonitrile increases with increasing monomer concentration and decreases with increasing temperature of polymerization and concentrations of vanadyl polycarboxylate and thioureaThe polymerization mechanism was proposed and discussed.

丙烯腈的合成路线及催化剂研究进展

丙烯腈是合成橡胶、合成纤维及合成塑料的原料和重要化学单体,广泛应用于汽车、航空航天、精细化学品等领域。概述了丙烯腈的工业应用、丙烯腈的合成路线,阐述了各合成路线的催化剂体系及其反应机理。

丙烯腈催化氧化催化剂性能及其中试评价

采用涂覆法制备了丙烯腈催化氧化催化剂,利用X射线衍射仪、物理吸附仪、扫描电子显微镜等仪器进行表征,考察了丙烯腈进气质量浓度、体积空速、贵金属上载量对催化剂性能的影响,并将其用于中试试验。结果表明:前驱体孔结构为狭缝孔,孔径分布集中在1~10 nm处,最可几孔径约为3.13 nm,比表面积为119.75 m^(2)/g;成型催化剂中元素Al,Pd,Pt,Ce质量分数依次为25.95%,2.03%,1.20%,27.39%;在总进气量为500 m^(3)/h,进气预热温度为400℃,进口丙烯腈最大质量浓度为3800 mg/m^(3)的条件下,出口丙烯腈质量浓度小于检出下限(0.25 mg/m^(3)),符合国家标准要求的丙烯腈排放限制(0.5 mg/m^(3))。

Influence of V/P Ratio on the Catalytic Performance of VPO/SiO_2 Catalysts for Ammoxidation of Chloro-Substituted Toluenes

A series of vanadium phosphate oxide(VPO) catalysts supported on silica(VPO/Si O2) with various mole ratios of V/P(nV:nP=1:0.8-1:3) were prepared through impregnation method. The catalytic activity was evaluated by ammoxidation reactions of several kinds of chloro-substituted toluenes(CT) in a fixed-bed reactor. The catalyst presented the best performance when nV:nP is 1:1.6. The prepared catalysts were characterized by N2 adsorption, hydrogen temperature programmed reduction(TPR) and ammonia temperature programmed desorption(TPD) and etc. The results reveal that P can decrease the bonding energy of V=O and increase the mobility of lattice oxygen which was beneficial for the improvement of the catalysts, while too much P can greatly decrease the average oxidation number of V which leads to deactivation of the catalysts. The surface acidity of the VPO/Si O2 catalysts is affected by nV:nP and the catalyst had the highest surface acidity when nV:nP is 1:1.6. The selectivity of catalysts is proportional to the surface acidity when nV:nP is lower than 1:3.0.

人工神经元网络辅助丙烷氨氧化催化剂设计

报道了利用人工神经元网络辅助丙烷氨氧化制丙烯腈催化剂设计的研究进展结果．通过筛选得到了可以拟合该反应体系的神经元网络模型，从而使丙烷转化率和丙烯腈选择性可以表示为催化剂组成的函数，利用培训后的神经元网络模型所得到的权值文件，结合作者自编的优化程序，该网络可用于预测最优的催化剂组成．实验得到丙烯腈收率和选择性可分别达到４３．０％和５６．２４％．

丙烯氨氧化催化剂研究进展

丙烯腈是重要的有机化工原料,在化学工业中广泛使用。目前,丙烯腈生产工艺主要是丙烯氨氧化法,该工艺的核心和关键问题是催化剂的研制与开发。综述了丙烯氨氧化催化剂的研究进展,包括反应机理和催化剂的发展状况,并对该催化剂的未来发展进行了展望。

丙烯氨氧化制丙烯腈的反应网络与动力学模型

采用积分式反应器,在反应温度,原料气的氧烯比较大的变化范围内,考察了丙烯氨氧化的反应特性,确定复杂反应的同络;根据 Redox 反应机理,同时引入表征催化剂表面状态特性的β,θ_(OA)和θ_(OW)等变量,建立了丙烯氨氧化反应的动力学模型,获得12个模型参数估计值均具有明确的物理意义和良好的拟合精度。

C_3烃氨氧化制丙烯腈研究进展

综述了Sohio和Petrox丙烯氨氧化制丙烯腈的工艺特点及丙烷氨氧化制丙烯腈工艺过程。介绍了C3烃氨氧化制丙烯腈的催化剂体系,其中钼铋铁系催化剂在目前丙烯氨氧化生产丙烯腈的工艺中广泛使用,钼酸盐和锑酸盐催化剂是丙烷氨氧化反应中催化性能最好的两类催化剂,最有希望应用于工业生产。总结了C3烃氨氧化制丙烯腈的反应机理,丙烯经由烯丙基中间体直接氨氧化生成丙烯腈,丙烷经氧化脱氢生成丙烯再氨氧化生成丙烯腈被认为是C3烃氨氧化生成丙烯腈的两条主要反应路径。

甲苯氨氧化合成苯甲腈VPO催化剂研究

用浸渍法制备了不同磷钒比(P/V)的VPO和VPO/硅胶催化剂,并用XRD、FTIR、TPR进行了表征,在甲苯氨氧化制苯甲腈反应中考察了其催化性能。发现P的引入破坏了V2O5的晶态结构,有效阻止活性晶粒生长。V=O与V-O-V键在P作用下向催化剂内层移动,并被高度扭曲,催化剂表面生成磷酸盐物质,晶格氧数量明显减少,钒平均氧化态下降,催化剂供氧能力减弱。活性测试表明,催化剂P/V越高,它对苯甲腈选择性也越好,其中V3+离子和O2-空位扮演了重要的角色。认为VPO催化剂中内层V=O氧化-还原中心与P-OH的B酸中心共同形成了一个复合活性中心,P/V比在1到2之间的VPO/硅胶催化剂都具有较好催化性能。在440℃时甲苯转化率达到97%,对苯甲腈的选择性达到94%,故在此温度时苯甲腈产率约为91.2%。

用NC-Ⅲ型催化剂合成间苯二腈

研究了氧比、氨比、反应温度、线速度及负荷对氨氧化制间苯二腈的ＮＣ－ Ⅲ催化剂性能的影响。在ｎ（ 间二甲苯）／ ｎ（ 氨）／ ｎ（ 氧） ＝ １／（６ ～８）／８ 、温度４１５ ～４２５ ℃、线速度０－２ ｍ／ｓ、负荷６０ ～９０ ｇ／（Ｌ·ｈ） 条件下，间苯二腈的摩尔收率达７８ ％ 。研究表明，ＮＣ－ Ⅲ催化剂适用于低氨比、高负荷条件下操作，是氨氧化制间苯二腈高性能的催化剂，可适用于间苯二腈生产装置。

丙烯腈生产技术研究进展

综述了丙烯腈生产技术现状及生产技术的新进展。着重论述了丙烷氧化法生产丙烯腈、催化剂的研制情况、生产丙烯腈的新工艺与新技术,并对我国丙烯腈的生产与消费状况进行了分析,指出了我国丙烯腈行业的发展方向和主要研究领域。