负载型Fe_2O_3对乙苯脱氢反应的催化性能

以正硅酸乙酯(TEOS)为硅源,分别以十六烷基三甲基溴化铵(CTAB)和P123为模板剂通过溶胶凝胶法、水热合成法合成出MCM-41、Al-MCM-41、SBA-15介孔分子筛,然后将其作为催化剂载体负载Fe2O3,应用到乙苯催化脱氢制苯乙烯的反应中,考察了不同负载量对乙苯脱氢反应性能的影响,探讨了催化剂的活性保持时间。结果表明,将介孔分子筛作为催化剂载体负载Fe2O3应用到乙苯脱氢反应,当负载量为60%时乙苯的转化率和苯乙烯的选择性均最高。当n Si/n Al为60时,Fe2O3/Al-MCM-41催化性能最好。Fe2O3/SBA-15所持续的活性时间最长。     

乙苯CO_2脱氢规整结构催化剂

以堇青石蜂窝陶瓷为第一载体、γ-Al2O3为第二载体,制备了用于乙苯CO2脱氢的Fe系催化剂。研究发现,当Fe2O3负载量为10%时,Fe2O3/γ-Al2O3催化剂对于乙苯CO2脱氢反应活性最佳;添加适量碱金属、碱土金属和稀土元素氧化物为助剂改善Fe2O3/γ-Al2O3催化剂性能,催化剂活性明显提高,稳定性也有所增加。通过与传统颗粒催化剂比较,采用规整结构γ-Al2O3涂层堇青石负载的Fe系催化剂,乙苯转化率和苯乙烯选择性均有明显提高,反应温度为600℃、反应压力为常压、EB∶CO2为1∶10(摩尔比)、乙苯液时体积空速为1.0 h-1时,乙苯转化率可达85%,苯乙烯选择性为98%。     

纳米碳材料负载金属催化剂研究取得重要研究进展

积炭是催化剂在催化反应过程中普遍发生的现象，尤其是在乙苯直接脱氢体系中，反应物乙苯分子在金属氧化物催化剂表面很容易快速的产生积炭，导致催化剂的失活。近期，中科院金属所沈阳材料科学国家（联合）实验室催化材料研究部刘洪阳副研究员和苏党生研究员，利用乙苯直接脱氢过程反应中的积炭过程，巧妙的设计了一种钯／碳复合催化剂（Pd／C）。     

锂对二氧化碳气氛下乙苯脱氢催化剂铁(Fe)/活性炭(AC)的促进作用

研究了助剂Li对CO2气氛下活性炭负载的Fe氧化物(Fe/AC)催化剂上的乙苯脱氢性能的影响和CO2的作用。助剂Li的添加提高了Fe/AC催化剂在CO2气氛下的乙苯脱氢活性和稳定性;CO2气氛下的苯乙烯收率明显高于N2气氛下,表明CO2显著促进了乙苯脱氢反应。     

格尔伯特醇制备中镍铝合金与氢氧化钾的协同效应

分别以氢氧化钾为提供碱活性中心的催化剂,镍铝合金为提供金属脱氢活性中心的催化剂,催化癸醇合成二十碳格尔伯特醇反应,考察碱催化活性中心、金属催化脱氢活性中心、以及金属催化脱氢与碱催化活性中心同时存在对格尔伯特反应的影响。结果表明:只有碱催化活性中心存在,与金属催化脱氢与碱催化活性中心同时存在,格尔伯特反应机制不同;金属催化脱氢与碱催化中心之间存在协同效应,碱性活性中心存在的条件下,有利于金属催化醇脱氢生成相应的醛;而仅有金属活性中心时,在常压和液相条件下,醇脱氢生成醛的反应难以实现。     

乙苯脱氢催化剂的研制及工艺条件的评选

本文研究了无铬Fe-K系混合氧化物乙苯脱氢催化剂。考察了不同氧化物作为第四组份、Fe_2O_3/K_2O、不同载体以及催化剂焙烧温度对催化剂性能的影响,同时还考察了反应工艺条件对催化反应的影响。评选出的Fe_2O_2-K_2O-R_1-R_2/MgO催化剂具有较好的催化性能和寿命、在经280hr连续反应后,该催化剂上乙苯脱氢反应仍具有52％的高产率。     

乙苯催化脱氢制苯乙烯催化剂的开发研究进展

乙苯催化脱氢制苯乙烯的工业催化剂,四十年代中期为ZnO和MgO体系,因其活性、选择性欠佳而为后来开发的Fe-Cr-K体系所取代。七十年代特别是八十年代以来,一些高强度、长寿命、高选择性的新型催化剂相继问世,其中尤以不含Cr的高效催化剂国外已于七十年代工业化,并获得了巨大的经济效益。 催化剂开发研究 对乙苯催化脱氢制苯乙烯催化剂的开发研究,就当前来看,美国开发的Fe_2O_3系仍占有重要地位。其反应温度均在600℃     

铁酸盐系列丁烯氧化脱氢催化剂研究进展

综述了铁酸盐系列催化剂(Fe系催化剂)在丁烯氧化脱氢反应中的应用研究进展,介绍了Fe系催化剂的活性中心和氧化脱氢机理,分析了催化剂的失活原因,详述了助剂对Fe系催化剂催化性能的影响,并对Fe系催化剂的发展方向进行了展望。开发出高反应活性、高选择性和高强度的新一代Fe系丁烯氧化脱氢制丁二烯的高效催化剂,是今后的主要研究方向,同时,开发资源利用率高、低投资、低生产成本和废水量少的丁烯氧化脱氢工艺也非常关键。     

乙烯基降冰片烯异构化研究(Ⅰ)——(Na-NaOH)/(γ-Al_2O_3)体系催化剂研究

文章介绍了乙烯基降冰片烯异构化用的超强碱催化剂研究成果。本研究中开发出高碱强度、高碱量的超强碱催化剂——(Na—NaOH)/(γ-Al_2O_3)体系催化剂。其碱强度H-和碱量超过目前已报道的世界上最强的超强碱催化剂——日本住友化学公司超强碱催化剂碱强度和碱量,呈现出优异的催化性能。其乙烯基降冰片烯转化率达到99.6％以上,乙叉降冰片烯选择性达到99.84％以上。     

燃煤式乙苯脱氢炉

苯乙烯是石油化工的主要产品之一,工业上可采用乙苯脱氢、乙苯共氧化、苯乙烯抽提等方法制得。采用乙苯催化脱氢生产苯乙烯的工艺路线已有近40年的历史,此方法所采用的反应器有绝热型和等温型两大类。我国生产苯乙烯的厂家绝大多数采用的是列管等温型反应器。乙苯脱氢反应是一个强吸热反应。采用铁钾系催化剂反应温度一般为560℃～580℃,列     

引入ZnO对Fe-K系乙苯脱氢催化剂性能的影响

用BET、XRD、XPS、Mssbauer以及乙苯脱氢反应等手段详细考察了添加ZnO对Fe-K系催化剂性能的影响。实验结果表明，ZnO的引入加强了主催化剂Fe₂O₃和助催化剂K₂O间的相互作用，使稳定晶相KFe₁₁O₁₇的形成温度降低了50℃以上，从而有利于提高样品的耐水性能和机械强度。同时，ZnO的加入进一步促进了Fe³⁺/Fe²⁺电子对之间的转化，使样品的脱氢温度降低6～13℃，脱氢活性和选择性亦得到提高。     

Amorphous porous MxTi mixed oxides as catalysts for the oxidative dehydrogenation of ethylbenzene

The properties of different metal‐oxide‐doped porous titanium oxides as catalysts for the oxidative dehydrogenation of ethylbenzene were investigated. Amorphous porous mixed oxides based on the amorphous titania matrix with selected metal ion centers as active sites have been prepared by an acid‐catalyzed sol–gel method. The dehydrogenation of ethylbenzene was studied in a continuous gas phase flow reactor under different reaction temperatures at ambient pressure. Among the 23 catalysts studied the amorphous porous AM‐Cr₅Ti mixed oxide is the most promising catalyst. At 350 °C a 75% selectivity to styrene at a 29% conversion of ethylbenzene was obtained. BET, HRTEM, XRD, GC, MS, TGA and optical microscopy were employed to characterize the fresh and used AM‐Cr₅Ti catalyst. This revised version was published online in August 2006 with corrections to the Cover Date.     

An integrated surface science approach towards metal oxide catalysis

The function of a metal oxide catalyst was investigated by an integrated approach, combining a variety of surface science techniques in ultrahigh vacuum with batch reactor conversion measurements at high gas pressures. Epitaxial FeO(111), Fe₃O₄(111) and α‐Fe₂O₃(0001) films with defined atomic surface structures were used as model catalysts for the dehydrogenation of ethylbenzene to styrene, a practized selective oxidation reaction performed over iron‐oxide‐based catalysts in the presence of steam. Ethylbenzene and styrene adsorb onto regular terrace sites with their phenyl rings oriented parallel to the surface, where the π‐electron systems interact with Lewis acidic iron sites exposed on Fe₃O₄(111) and α‐Fe₂O₃(0001). The reactant adsorption energies observed on these films correlate with their catalytic activities at high pressures, which indicates that the surface chemical properties do not change significantly across the pressure gap. Atomic defects were identified as catalytically active sites. Based on the surface spectroscopy results a new mechanism was proposed for the ethylbenzene dehydrogenation, where the upward tilted ethyl group of flat adsorbed ethylbenzene is dehydrogenated at Brønsted basic oxygen sites located at defects and the coupling of the phenyl ring to Fe³⁺ terrace sites determines the reactant adsorption–desorption kinetics. The findings are compared to kinetic measurements over polycrystalline catalyst samples, and an extrapolation of the reaction mechanism found on the model systems to technical catalysts operating under real conditions is discussed. The work demonstrates the applicability of the surface science approach also to complex oxide catalysts with implications for real catalysts, provided suitable model systems are available.     

High Performance of Fe–K Oxide Catalysts for Dehydrogenation of Ethylbenzene to Styrene with an aid of ppm-order Pd

Styrene is manufactured industrially through catalytic dehydrogenation of ethylbenzene on Fe–K oxide-based catalysts. It was invented by Süd-Chemie Group that the activity of the industrial ethylbenzene dehydrogenation catalysts (Styromax) based on the oxides of Fe and K is highly promoted by the addition of small amount (hundreds ppm-order) of precious metals such as Pd. The present work is intended to elucidate the role of Pd on the Fe–K catalyst empirically by use of a periodical pulse technique from a mechanistic point of view. The oxidative dehydrogenation was faster than the simple dehydrogenation, and it proceeded by consuming the surface lattice oxygen in the catalyst. The lattice oxygen was subsequently supplied from steam. Palladium added to the Fe–K oxide catalysts was found to enhance the rate of regeneration (supplying) of the lattice oxygen, although it hardly changed the rate of dehydrogenation of ethylbenzene or consumption of surface lattice O^2? anions. This study demonstrated that steam works not only as a diluent but also as a reactant to form hydrogen and lattice oxygen.     

粘结剂含量对铁系乙苯脱氢催化剂的影响

考察了粘结剂含量对铁系乙苯脱氢制苯乙烯催化剂的影响,采用X射线衍射(XRD)、M(o)ssbauer谱和H2程序升温还原（H2-TPR）等方法对催化剂进行了表征.结果表明,不含粘结剂催化剂的机械强度和活性均较低,添加粘结剂后,可以较大幅度地提高催化剂的机械强度和活性,当粘结剂含量为4.0％时,催化剂的机械强度和活性较好...     

The oxidative dehydrogenation of ethylbenzene to styrene

The results of a kinetic study of the oxidative dehydrogenation of ethylbenzene to styrene over an organic catalyst (pyrolyzed polymerized acrylonitrile) are reported. The reaction is found to be second order in ethylbenzene and zero order in oxygen with an activation energy of 76.5 kJ/mol. The rate equation is: \documentclass{article}\pagestyle{empty}\begin{document}$ - r(mol/\min .g\,catalyst) = 3.2 \times 10^9 \exp [ - 76,500/RT] \cdot C_{EtB}^2 \cdot C_{O_2 }^0 $\end{document} where R = 8.31 J/niol.K and concentration (CEtB) is expressed as mol/L. The catalyst is more active than conventional metal oxide catalysts and appears to be quite stable under reaction conditions. The results suggest that, using the PPAN catalyst, it may be possible to reduce the operating temperature of the oxidative dehydrogenation of ethylbenzene to about 250-300°C, thereby avoiding some of the problems of the present high temperature process.     

VxTi复合氧化物催化剂用于二氧化碳气氛乙苯脱氢的研究

采用溶胶-凝胶法制备了以TiO₂为基体的VxTi复合氧化物催化剂，该催化剂用于乙苯二氧化碳低温氧化脱氢制苯乙烯反应。考察了活性组分含量和焙烧温度对催化剂活性的影响。结果表明，活性金属钒的添加有助于提高脱氢反应性能，但存在一适量值，摩尔分数超过5%，催化脱氢活性下降。通过XRD分析发现，不同焙烧温度制备的VxTi催化剂中TiO₂的晶相不同，随着温度的升高，TiO₂的晶相将由锐钛矿型转变为金红石晶相。TiO₂锐钛矿型晶相有利于苯乙烯选择性的提高，而金红石晶相则不利于催化剂的脱氢反应。     

CO2 utilization as an oxidant in the dehydrogenation of ethylbenzene to styrene over MnO2-ZrO2 catalysts

MnO₂-ZrO₂ binary oxide catalytic system was applied for the effective utilization of CO₂ as an oxidant in the ethylbenzene dehydrogenation (EBD) to styrene monomer (SM). MnO₂-ZrO₂ oxides were prepared by co-precipitation method and characterized as solid solution mixture having surface area more than 100² g⁻¹. 10% MnO₂-ZrO₂ mixed oxide catalyst exhibited conversion of 73% with the selectivity of 98% at 650 °C. The MnO₂-ZrO₂ binary oxides were X-ray amorphous whereas the individual oxides (MnO₂ and ZrO₂) having much lower surface areas were crystalline in nature. As a result, MnO₂-ZrO₂ binary oxides exhibited greatly elevated catalytic activity for the conversion of ethylbenzene (EB) than those of individual oxides in the presence of CO₂. However, in the absence of CO₂ poor catalytic activity and stabilities were observed. Gradual enhancement of activities were demonstrated in the higher CO₂ to EB ratios. Hence, CO₂ had a profound role as a soft oxidant by improving both activity and stability in the EBD over MnO₂-ZrO₂ mixed oxide catalysts.     

Dehydrogenation of Ethylbenzene to Styrene in the Presence of CO2 over Calcined Hydrotalcite-Like Compounds as Catalysts

Calcined hydrotalcite-like compounds were effective catalysts for the dehydrogenation of ethylbenzene in the presence of CO₂ as an oxidant. X-ray diffraction patterns suggested that the catalyst components are distributed uniformly. The activity (areal rate) of Fe(1)/Al(2)/Zn(6) oxide catalyst (molar ratios in parentheses) was the highest among the catalysts tested.