改性天然丝光沸石的酸度与催化活性

在自制的微反色谱仪上,以邻二甲苯的异构化作为典型反应,用吡啶碱中毒法研究了改性天然丝光沸石催化剂的酸度及活性,得到了它们同金属离子电负性之间的关系,并排列出不同金属离子的活性顺序。探讨了离子交换度对LaHNM催化剂的酸度与活性的影响。     

NaHM催化合成甲胺反应的工艺

将一系列自制天然丝光沸石催化剂与目前国内唯一工业化的A 6催化剂及氢型合成丝光沸石催化剂进行比较,筛选出催化效果较好的催化剂NaHM,并对其进行工艺条件优化,同时考察了NaHM用于甲胺合成反应的稳定性。结果表明天然丝光沸石催化剂具有更好的二甲胺选择性;金属离子改进可强化沸石的择形效果,但同时降低甲醇转化率。改性催化剂中NaHM效果最好。该催化剂具有较好的活性稳定性,适宜的工艺条件为:t=390℃、τ(LHSV)=1 93h-1、n(N)/n(C)=1 8。此时其甲醇转化率为93 9%,二甲胺选择性为38 5%。     

改型天然丝光沸石催化酯化反应

一、前言醋酸与丁醇的酯化反应,采用硫酸为催化剂是基于酸的羧基上的氧取得质子后生成正碳离子(Ⅰ)与一个醇分子结合产生复杂的中间络合物(Ⅱ),络合物进一步发生分解,给出酯。因此,所用催化剂必须能够提供质子。天然丝光沸石经过改型后,称为氢型天然丝光沸石。氢型天然丝光沸石是提供质子的源泉,所以改型天然丝光沸石具有酯化反应的催化性能。     

镧改性丝光沸石对甲苯甲醇烷基化反应的影响

采用La离子交换法对交换度为75%和100%的氢型丝光沸石分子筛进行改性，通过XRD、SEM和FTIR等手段进行表征，并考察催化甲苯甲醇烷基化反应的性能。结果表明，与交换度为75%的氢型丝光沸石分子筛相比，离子交换法使离子交换度为100%的氢型丝光沸石骨架铝部分脱除，B酸减少，L酸略增；La的引入不破坏分子筛的骨架结构，但催化剂制备方法降低了分子筛结晶度和分子筛酸强度；La的引入可以抑制积炭和二甲苯异构化反应的发生，提高对二甲苯选择性和催化剂稳定性。     

天然丝光沸石烷烃异构化催化剂的研制——(Ⅰ)原矿粉直接加工成催化剂

采用缙云产的天然丝光沸石(NM),经铵酸法处理制得氢型天然丝光沸石(HNM),然后用离子交换法 E,浸渍法 I 及机械混合法 M 载铂或钯,制成双功能催化剂。在加压微反色谱联合装置上进行 nC_5~0/nC_6~0异构化反应,测定催化活性。实验表明,采用离子交换法载的铂或钯的催化剂,活性最高。同时还考察了粘结剂种类,原料组成及工艺条件,如温度、空速、氢烃比和压力对催化剂活性的影响等。使用0.5%Pd/HNM-E_(43)催化剂在20mL 小试加压临氢异构化反应器上进行了稳定性试验。数据表明,E_(43)催化剂具有较高的活性和良好的稳定性、也具有良好的再生性能。     

乙苯氧化脱氢制苯乙烯催化剂

制备了二氧化碳选择氧化乙苯（EB）制苯乙烯的催化剂。实验结果表明,VAPO-5分子筛是一种适宜的催化剂载体,且本身已含有高分散的活性组分钒,具有较好的催化活性。VAPO-5负载Ni、Ce、Mo后催化剂的催化效果比较好,其中负载Ni的效果最好,苯乙烯收率可达38.5％;此外,添加碱土金属助催化剂如Mg或稀土元素La后,乙苯转化率明显提高,前者的苯乙烯收率高达44.1％。     

旭化成开发耐久性沸石催化剂

日本旭化成化学公司研究人员日前开发出新型沸石催化剂。这种催化剂可以实现丁烯裂解高转化率制乙烯和丙烯,并且可以在较长时间内保持较高的活性。新型催化剂采用含钠的氢离子交换型ZSM-5/SiO2沸石。沸     

预处理条件对天然丝光沸石结构影响的研究

以提高天然丝光沸石纯度和改善孔道结构作为目标,考察了酸处理液浓度及焙烧温度等预处理条件对天然丝光沸石结构的影响.结果表明酸处理可以有效去除沸石中的金属杂质,调变沸石比表面积,提高硅铝比进而增强表面酸中心强度;焙烧可除去沸石内一些与矿物结合牢固且难与酸反应的孔道中的杂质,疏通孔道,但对沸石晶型结构影响较大,温度过高晶型被破坏;优化的预处理条件为处理液盐酸浓度1 mol/L、焙烧温度400℃.     

空速对不同Y型分子筛FCC催化剂轻柴油裂化性能的影响

通过调节进料泵速，考察了空速对轻柴油在不同沸石含量的REUSY、REHY和REY型 FCC催化剂上裂化性能的影响。结果表明，随着空速的增加，原料在不同催化剂上转化率之间的差距逐渐增大，在低沸石含量的REY催化剂上转化率下降较缓，而在高沸石含量的REUSY催化剂上转化率下降较快。其原因可能在于低沸石含量的催化剂微孔总量较少，在高空速和短接触时间，受内扩散时间的影响小于高沸石含量的催化剂，因而表观裂化转化率较高     

天然丝光沸石的化学处理及其对氨吸附动力学的影响

本文用流动重量法测定了氨在岱石口天然丝光沸石(ONM)及其两种化学处理样品——酸处理样品〔HNM(A)〕铵型沸石焙烧脱氨而得的脱阳离子型沸石(HNM)——上的吸附动力学曲线.与ONM相比,氨在HNM和HNM(A)上的吸附动力学特性均有所改善,且以HNM的吸附动力学特性为最佳.测定了40℃下氨在HNM上的吸附等温线,并用Dubinin方程进行了拟合;考察了按交换度、铵型沸石焙烧脱氨的温度和时间对氨在HNM上的吸附动力学影响;用氨程序升温脱附法(TPD)测定了不同焙烧温度下制得HNM的表面酸度,表明ONM改造成HNM后强酸中心增强.     

SYNTHESIS OF ZSM-5 FROM MODIFIED CLINOPTILOLITE AND ITS CATALYTIC ACTIVITY IN ALKYLATION OF BENZENE TO ETHYLBENZENE

ZSM-5 catalysts were prepared by utilizing clinoptilolite found in Western Anatolia in abundant amounts as a type of natural zeolite. Hydrothermal reaction was conducted with HCl-treated clinoptilolite at 180°C. After characterizing the solid products obtained by this reaction as ZSM-5 by means of XRD, IR, TGA, surface area analyzer, and chemical analysis they were tested as catalysts in benzene alkylation reaction with ethylene leading to ethylbenzene. Catalytic performance of samples prepared in this study was investigated for benzene conversion, ethylbenzene yield, and selectivity. It was found that ZSM-5(A) sample showed performance similar to that of the reference sample (ZSM-5(C)) synthesized by using patented literature information in terms of benzene conversion. When the reaction temperature was increased from 400° to 425°C ethylbenzene yield and selectivity results of ZSM-5(A) sample were improved but coke formation increased. Catalyst test results indicated the possibility of using clinoptilolite as a raw material in the synthesis of ZSM-5 catalyst for alkylation of benzene with ethylene reaction.     

EFFECT OF ZEOLITE CRYSTALLITE SIZE ON Pt/KL CATALYSTS USED FOR THE AROMATIZATION OF n-OCTANE

The effects of varying zeolite crystallite size in n-octane aromatization over Pt/KL have been studied on a series of catalysts. Various KL zeolites were synthesized via microwave-hydrothermal treatment, which allows for good control of crystallite morphology. Zeolites with different crystallite sizes were prepared by varying aging time (17–24 h), amount of barium (0–445 ppm), and seeding (0–8 wt%). The results showed that higher aging time resulted in smaller zeolite crystallite size, whereas the addition of barium resulted in larger crystallite size. Moreover, the addition of seeding reduced the crystallite size from 1.47 to 0.94 μm. Pt supported on different zeolite catalysts (Pt/KL) was prepared by vapor phase impregnation (VPI). The fresh catalysts were characterized by DRIFTS of adsorbed CO and volumetric hydrogen chemisorption. The results indicated that Pt clusters are well dispersed inside the zeolite channel in all the catalysts prepared. The aromatization of n-octane was tested on the different catalysts at 500°C and atmospheric pressure. It was found that the catalytic activity of all catalysts dropped rapidly after about 200 min on stream due to coke plugging inside the pore of the KL zeolite. It was also observed that less ethylbenzene (EB) and o-xylene (OX) were obtained as the conversion increased because both EB and OX are converted to smaller molecules such as benzene, toluene, etc., by secondary hydrogenolysis. Furthermore, the EB/OX ratio increases with zeolite crystallite size due to an enhanced preferential conversion of the larger OX molecules compared to the narrower EB as their path through the pores is restricted.     

EFFECT OF ZEOLITE CRYSTALLITE SIZE ON Pt/KL CATALYSTS USED FOR THE AROMATIZATION OF n-OCTANE

The effects of varying zeolite crystallite size in n-octane aromatization over Pt/KL have been studied on a series of catalysts. Various KL zeolites were synthesized via microwave-hydrothermal treatment, which allows for good control of crystallite morphology. Zeolites with different crystallite sizes were prepared by varying aging time (17-24 h), amount of barium (0-445 ppm), and seeding (0-8 wt%). The results showed that higher aging time resulted in smaller zeolite crystallite size, whereas the addition of barium resulted in larger crystallite size. Moreover, the addition of seeding reduced the crystallite size from 1.47 to 0.94 μm. Pt supported on different zeolite catalysts (Pt/KL) was prepared by vapor phase impregnation (VPI). The fresh catalysts were characterized by DRIFTS of adsorbed CO and volumetric hydrogen chemisorption. The results indicated that Pt clusters are well dispersed inside the zeolite channel in all the catalysts prepared. The aromatization of n-octane was tested on the different catalysts at 500°C and atmospheric pressure. It was found that the catalytic activity of all catalysts dropped rapidly after about 200 min on stream due to coke plugging inside the pore of the KL zeolite. It was also observed that less ethylbenzene (EB) and o-xylene (OX) were obtained as the conversion increased because both EB and OX are converted to smaller molecules such as benzene, toluene, etc., by secondary hydrogenolysis. Furthermore, the EB/OX ratio increases with zeolite crystallite size due to an enhanced preferential conversion of the larger OX molecules compared to the narrower EB as their path through the pores is restricted.     

乙苯液相氧化制备苯乙酮催化剂的研究进展

苯乙酮是重要的有机合成中间体,当前主要通过乙苯直接空气氧化法合成苯乙酮的技术路线存在转化率低,副产物多等不足。利用绿色催化剂由乙苯氧化直接合成苯乙酮则具有重大的潜在经济效益、社会效益和环境效益,已成为催化与有机合成等研究领域中极具挑战性的热点课题之一。较为系统地总结了乙苯液相氧化合成苯乙酮的研究工作,首先对其反应机理进行了简述,然后着重综述了用于该反应的催化体系如过渡金属化合物、过渡金属络合物、杂多化合物、分子筛以及其他化合物等。最后,对乙苯氧化合成苯乙酮反应催化体系的研究提供了一些建议和展望。     

掺杂炭纤维对乙苯脱氢催化剂性能的影响

在氮气保护及程序控温条件下,制备了具有一定孔隙的炭纤维掺杂的乙苯脱氢催化剂。通过对比表面积、孔隙度的测定,发现微孔数量随炭纤维加入量的增加而增加,炭纤维催化剂得到了活化。催化剂的扫描电镜分析、侧压强度及抗拉强度测试证明,炭纤维使催化剂的机械强度明显提高。乙苯脱氢实验表明,苯乙烯选择性随炭纤维的加量增大;乙苯的转化率则存在最大值。考虑机械强度与催化活性,加入6%炭纤维的催化剂最佳。     

乙苯脱氢过程中催化剂表面碱性研究

本文应用程序升温脱附技术(TPD),以乙酸作为分子探针,考察了无铬Fe—K系混合氧化物乙苯脱氢催化剂的表面碱性。Fe—K系催化剂表面至少存在两种强度不同的碱中心,其中强碱中心b态对乙苯催化脱氢贡献较大;而催化剂表面同时具有适当的碱强度和密度是获得较好催化性能的重要条件。研究结果还发现,乙苯脱氢反应可能类似于强碱催化的双分子消除E2反应,其中催化剂表面碱位起着类似于E2历程中强碱试剂的作用。     

短时间内系统多角度设计研制催化剂的设想

综述了新催化剂的研究现状及发展方向 .组合化学概念在催化研究领域中的引入 ,导致了新催化剂研制的技术革命 .通过对乙苯氧化脱氢模型反应分析 ,采用溶胶 -凝胶法 ,提出了在短时间内系统多角度设计研制催化剂的设想     

Oxidative Dehydrogenation of Ethylbenzene with Carbon Dioxide over Metal-Doped Titanium Oxides

Various metal-doped (Fe, V, Zr, Mg) titanium oxides were prepared by an acid-catalyzed sol–gel method and their properties as catalysts were investigated for oxidative dehydrogenation of ethylbenzene in the presence of carbon dioxide. The characterization techniques, XRD, BET, TGA were employed to analyze the features of catalyst. Fe₃Ti catalyst was found to be quite effective among the catalysts tested at 823 K, 39.8% ethylbenzene conversion and 98% styrene selectivity were acquired.     

Supported Vanadia Catalysts for Dehydrogenation of Ethylbenzene with CO2

Alumina supported vanadia catalysts (V/Al) for selective oxidehydrogenation of ethylbenzene with CO₂ were prepared by impregnation method. During preparation the effect of promoters and calcined temperature was investigated, it was found these two items had a strong influence on the activity of V/Al catalysts. Dehydrogenation reaction with CO₂ was happened in the fixed-bed reactor at 450 °C. Results showed that 15.2% ethylbenzene conversion and 99.2% styrene selectivity were acquired when V₂K/Al catalyst was used.     

Isopropylation of ethylbenzene over MCM-22 molecular sieve

MCM-22 materials (Si/Al ratios 24, 50 and 75) were synthesized and characterized. The catalytic activity was examined in the vapour phase isopropylation of ethylbenzene with isopropyl alcohol. Based on ethylbenzene conversion, the order of activity of the catalysts is found to be MCM-22(50) > MCM-22(24) = MCM-22(75). The selective formation of p-isopropyl ethylbenzene (p-IPEB) suggests that the reaction occurs mainly inside the 10-membered ring channel. The time on stream study over MCM-22(50) showed steady conversion for 6 h with nearly the same selectivity to p-isopropyl ethylbenzene (p-IPEB) and o-isopropyl ethylbenzene (p-IPEB).