Study of the catalytic behaviors of concentrated heteropolyacid solution. I. A novel catalyst for isobutane alkylation with butenes

A novel liquid acid catalyst, composed of heteropolyacid and acetic acid for the alkylation of isobutane with butenes is reported. The conditions for the formation of catalytic active phase as well as its catalytic behaviors in alkylation of isobutane with butenes have been studied. It was found that acetic acid, as a solvent, exerts a synergistic effect on the acid strength of heteropolyacid, and the contents of crystal water in HPAs have influence over the formation of active phase and the catalytic activity. This novel catalyst is comparable to the sulfuric acid in catalytic activity.     

Ab initio calculations on the mechanism of isobutane and 2-butene alkylation reaction catalyzed by hydrofluoric acid

Ab initio method was employed to determine the mechanism of alkylation reaction of 2-butene with isobutane. The results indicated that 2-butene is rapidly protonated to form sec-butyl carbonium ion, which then reacts with isobutane to form tert-butyl carbonium ion. The resulting carbonium ion is then deprotonated to form isobutene that reacts rapidly with tert-butyl carbonium ion to form trimethylpentane (TMP) carbonium ion. Finally, the TMP⁺ carbonium ion is converted to TMP via the hydride transfer process. The transition states of the interactions were obtained by using the SCAN method (a calculation key word for potential energy surface) first and then the intrinsic reaction coordinates were traced using the Gaussian program. In addition, the energy changes and geometric parameters of the interactions were analyzed. The computed results indicated that the energy barriers are close to or less than zero for the interaction of isobutane with protonated 2-butene or for the interaction of tert-butyl carbonium ion with isobutene, suggesting rapid reaction steps of the carbonium ions. The 2,2,3-TMP is kinetically controlled, while the formation of 2,2,4-TMP is controlled by reaction equilibrium. The calculated results were in good agreement with the experimental results.     

Mathematical model for the process of benzene alkylation by higher olefines

In this work, we considered the results on the modeling of the industrial catalytic alkylation process, one of the terminal stages in the production of linear alkyl benzene sulfonates (LAS) used as the basis for the synthesis of synthetic detergents. Taking into account the experimental data obtained under regular operational conditions of alkylation unit at the Linear Alkyl Benzene and Linear Alkyl Benzene Sulfonates (LAB-LAS) Plant of OOO Kirishinefteorgsintez (OOO KINEF), we developed a scheme of chemical reactions for the purpose of creating the kinetic model for the alkylation process. The kinetic parameters of this model were identified by solving the inverse kinetic problem under the lack of necessary experimental data, so we had to reduce the number of estimated kinetic parameters with the use of thermodynamic data. The software model of this process permitted us to calculate quite precisely the material and heat balances of the reactor and also to study the influence of changes in different technological parameters on the effectiveness of the process.     

混酸法制取高浓度富过磷酸钙工艺条件的试验研究

介绍采用硫酸、磷酸混合分解磷矿粉制高浓度富过磷酸钙〔w(P2 O5有效)～ 34%〕的试验过程 ,研究混酸用量、混酸浓度、混酸温度、磷酸替代率等工艺条件对磷矿分解率的影响 ,经正交试验 ,确定了制备的最佳工艺条件 :混酸w(H3 PO4+H2 SO4) 6 6 %～ 6 9% ,混酸温度 70～ 80℃ ,磷酸替代率 5 0 %～ 5 4 % ,混酸用量为理论酸用量的 93%～ 97%。并对影响料浆固化及成品质量的有关因素展开了讨论     

Enhancement of catalytic activity of the ammonium/potassium salt of 12-molybdophosphoric acid by iron ion addition for the oxidation of isobutane to methacrylic acid

The oxidation of isobutane to methacrolein and methacrylic acid was carried out over potassium/ammonium salts of 12-molybdophosphoric acid (Keggin-type heteropoly compounds), with overall selectivity to the desired products higher than 50%. The addition of iron to the catalyst composition led to a substantial enhancement of the catalytic activity, with an increase in the yield to the desired products, even though the selectivity decreased. The catalysts all have a secondary cubic structure, and are stable in the reaction environment. No trace of structural decomposition was found in spent catalysts. It was found that the addition of iron led to a substantial increase in the catalyst acidity and it is proposed that the Lewis acidity might play a role in the activation of the paraffin.     

电石法制VCM装置转化工段存在的工艺缺陷及技改措施

10万t／a以上生产规模的电石法制VCM装置的转化工段主要由30多台两两串联的转化器构成．生产运行中存在着第二级转化器催化负荷过小的工艺缺陷，通过加大原料气进口流量、改变乙炔／氯化氢进料配比等技术措施．可以实现转化工段在原来生产能力基础上再提高10％的目的。该技改措施切实可行．对10万t／a以上生产规模的新老厂均适用。     

盐酸解析工艺在PVC废酸治理中的应用

介绍了将盐酸解析工艺应用于PVC副产废酸治理的生产技术 ,解析出的HCl气体作为合成VCM的原料气 ,每年回收量超过 1 80 0t,回收率达到 85 % ;产生的经济效益约 1 5 9.8万元 a;可节约水资源90 0 0m3 a。同时 ,治理了废酸和CaCl2 排放造成的水污染及H2 S对大气的污染。     

A simplified model for catalyzed isobutane autoxidation: implications for the mechanism of catalysis by halogenated porphyrin complexes

A simple kinetic model shows that a radical-chain mechanism can account for the high activity and selectivity found for oxidation of isobutane tot-butanol catalyzed by highly halogenated metalloporphyrins.     

UASB-BIOFOR工艺处理柠檬酸废水

采用UASB-BIOFOR滤池组合工艺处理柠檬酸废水,对操作步骤及注意事项进行了详细介绍.实验结果表明,该组合工艺对柠檬酸废水处理效果良好,系统出水能够达到国家《污水综合排放标准》(GB 8978-1996)中的一级标准.     

磷石膏制酸新工艺热力学分析

磷石膏是磷肥工业的排放废渣,文中提出了用氢气、一氧化碳或甲烷替代焦炭处理磷石膏的工艺构想,采用热力学软件对这4个过程的能耗进行了计算与分析,结果表明,新的磷石膏处理工艺过程能耗比传统的磷石膏制酸联产水泥工艺过程降低30%左右,且3个新工艺过程的能耗较为接近。通过对用甲烷部分氧化得到的还原性气体处理磷石膏新工艺与传统工艺的原料成本估算,发现前者的原料成本略低于后者,该新工艺构想前景广阔。     

高钛高炉渣酸浸液沸腾水解制备偏钛酸的过程动力学研究

攀枝花钢铁厂高炉冶炼产生的水淬高钛高炉渣经浓硫酸焙烧、稀硫酸浸取后获得富含Ti⁴⁺的浸取液,通过沸腾水解法可将浸取液中的可溶性Ti⁴⁺转化成H₂TiO₃沉淀。为探究酸浸液沸腾水解制备H₂TiO₃的过程动力学行为,研究了底液pH和水解温度在不同反应时间下对Ti⁴⁺水解率的影响,并采用Avrami模型和生长动力学模型模拟水解过程,结果显示Ti⁴⁺的水解过程更符合Avrami动力学模型,证明H₂TiO₃的形成速率主要由颗粒形核过程控制。通过Arrhenius方程拟合计算得到的水解反应的表观活化能为197 930 J/mol,并获得了水解过程的半经验式动力学方程。     

磷石膏转氨法制硫酸技术原理与过程评价

以贵州瓮福磷石膏为原料,探讨了碳酸铵循环法利用磷石膏制取硫酸的改进工艺。通过热重、气相质谱连用技术分析了转氨法关键步骤--硫酸氨分解特征,并指导确定了分解温度以避免不利副反应的发生。通过优化实验,使磷石膏与碳酸铵复分解反应制备硫酸铵的转化率达到92.93%。而硫酸铵与氧化铁固相反应的实验结果表明:420℃,1h时,氨气回收率达86.57%;700℃,1h时,SO₃回收率达到93.75%,两步法工艺可以较好的实现氮和硫元素的回收循环。磷石膏转氨法制硫酸,一次性资源消耗和CO₂排放量较低,副产品经济价值较高,环境相容性较好,具有更好的工业化前景。     

硫铁矿山酸性废水治理工艺设计

主要介绍了硫铁矿山酸性废水的产生机理及处理方法,分析与比较了HDS(高密度污泥处理工艺)处理方法与其他方法的区别及优势,给出了HDS处理工艺的流程.废水经处理后可达到<污水综合排放标准>GB8978-1996中一级排放标准的要求.     

Concentration of mixed acid by electrodialysis for the intensification of absorption process in acrylic acid production

The absorption process in acrylic acid production was water-intensive. The concentration of acrylic acid before distillation process was low, which induced to large amount of wastewater and enormous energy consumption.In this work, a new method was proposed to concentrate the side stream of absorption column and thus increase the concentration in bottom product by electrodialysis. The influence of operating conditions on concentration rate and specific energy consumption were investigated by a laboratory-scale device. When the voltage drop was 1 V·cP~(-1)(1 cP=10~(-3) Pa·s), flow velocity was 3 cm·s~(-1) and the temperature was 35 °C, the concentration rates of acrylic acid and acetic acid could be 203.3% and 156.6% in the continual-ED process. Based on the experimental data, the absorption process combined with ED was simulated, in which the diluted solution from ED process was used as spray water and the concentrated solution was feed back to the absorption column. The results shown that the flow rate of spray water was decreased by 37.1%, and the acrylic acid concentration at the bottom of the tower was increased by 4.56%. The ions exchange membranes before and after use 1200 h were tested by membrane surface morphology(scanning electron microscope), membrane chemical groups(infrared spectra), ion exchange capacity, and membrane area resistance, which indicated the membrane were stable in the acid system. This method provides new method for energy conservation and emission reduction in the traditional chemical industry.     

A continuous process for the recovery of lactic acid by reactive distillation

Separation and purification of lactic acid from the fermentation broth are difficult because of its non‐volatile nature and the presence of other organic acids. Esterification of lactic acid with methanol followed by hydrolysis of the separated methyl lactate is an effective technique for this purpose. A continuous process for recovery is proposed and various aspects are evaluated through simulation and experiments. In the proposed route, a vapor stream containing methyl lactate is removed from a two‐phase CSTR, used for esterification, operated under boiling conditions. The ester thus separated from the aqueous solution is further hydrolyzed in a reactive distillation column. Continuous removal of the volatile component (i.e. methanol) from the reaction zone increases conversion, thus pure lactic acid is obtained from the bottom of reactive distillation column. The results obtained in the experiments are compared with the simulation results. Further simulation studies were performed to obtain the suitable operating conditions for higher conversion and concentration of lactic acid. Copyright © 2006 Society of Chemical Industry     

织金磷矿在盐酸中的酸解工艺研究

设计了一个4因素5水平正交实验,对磷矿石的盐酸酸解工艺进行了研究,确定了织金磷矿的最佳盐酸酸解工艺.利用正交实验结果分析了酸比、酸质量分数、温度、粒度4种因素对磷矿石中P2O5浸取率的影响.同时得出最佳酸解条件:酸比105％,液固比260％,温度45℃,粒度200目,此时磷矿石中的P2O5的浸取率可以达到98.74％.     

盐酸作吸收剂用于气态膜法从废水中脱除/回收氨氮

考察了盐酸作吸收剂时用气态膜技术从水溶液中脱氨的可行性,鉴于盐酸的挥发性,着重考察了不同料液氨水浓度下气态膜过程可以稳定操作时所对应的吸收液中盐酸的临界浓度。在此基础上,研究了料液氨氮浓度、料液流速、吸收液流速、吸收液盐酸浓度和操作温度等操作参数对膜传质性能的影响,并考察了该工艺的长期操作稳定性。实验结果证明,气态膜脱氨过程可采用一定浓度的稀盐酸溶液作为吸收剂,并可通过向吸收液中不断添加浓盐酸的方式得到浓度为>15%的氯化铵溶液。在料液浓度为2000 mg/L、吸收液盐酸浓度为2%、操作温度为25 ℃的操作条件下,中空纤维膜组件持续稳定运行了650 h以上,总传质系数保持在4.25×10?6 m/s左右。用盐酸作吸收剂时废水中氨氮可脱至15 mg/L以下,符合国家环保标准。这表明采用盐酸作吸收液用气态膜法从废水中脱除回收富集氨氮是可行的。     

三聚氰胺净化湿法磷酸第二阶段反应动力学

研究了三聚氰胺结晶法净化湿法磷酸生产磷酸钠盐的第二阶段反应过程动力学特征，测定了反应过程的动力学数据。在液固反应扩散传质控制条件下，确定了反应过程的动力学方程为１－３（１－ＸＢ）Ｂ２３＋２（１－ＸＢ）＋ｋ∫ｔ０ＣＡＬｄｔ。式中ｋ符合Ａｒｈｅ－ｎｉｕｓ关系：ｋ＝６．１０×１０－３ｅｘｐ［－５．５２９／（ＲＴ）］。对模型的检验结果表明所得动力学模型的置信度在９５％以上。     

XPS and EXAFS study of supported PtSn catalysts obtained by surface organometallic chemistry on metals: Application to the isobutane dehydrogenation

In this work, well defined alumina and silica supported Pt and PtSn catalysts were prepared by surface organometallic reactions and were characterized by TEM, XPS and EXAFS. These catalysts were tested in the catalytic dehydrogenation of isobutane. XPS results show that tin is found under the form of Sn(0) and Sn(II,IV), being the percentage of Sn(0) lower for alumina supported than for silica supported catalysts. Tin modified platinum catalysts, always show a decrease of approximately 1 eV in the BE of Pt, what would be indicative of an electron charge transfer from tin to platinum. When the concentration of Sn(0) is high enough, in our case Sn(0)/Pt ∼ 0.3, EXAFS experiments demonstrated the existence of a PtSn alloy diluting metallic Pt atoms, for both PtSn/γ-Al₂O₃ and PtSn/SiO₂. This PtSn alloy seems to be not active in the dehydrogenation reaction; however, it is very important for selectivity and stability, inhibiting cracking and coke formation reactions. The ensemble of our catalytic, XPS and EXAFS results, show that bimetallic PtSn/γ-Al₂O₃ catalysts, prepared via SOMC/M techniques, can be submitted to several sequential reaction–regeneration cycles, recovering the same level of initial activity each time and that the nature of the catalytic surface remains practically without modifications.