水热处理对MCM-22催化剂酸性、孔结构及甲苯/甲醇烷基化性能的影响

采用XRD, NH3-TPD, IR和低温氮气吸附等方法研究了分别以纯水蒸气和质量分数为6％的氨水蒸气处理MCM-22分子筛催化剂后, 其酸性和孔结构的变化, 并以甲苯、甲醇烷基化为探针反应考察了催化剂的催化性能. 研究结果表明, 在两种不同介质中和处理温度不高于400 ℃条件下, 催化剂的总酸量变化不大, 强酸中心有所增加; 处理温度高于500 ℃后, 催化剂的总酸量明显下降, 强酸中心基本消失; 经水热处理后, MCM-22分子筛催化剂中形成了孔径不均匀的二次孔, 平均孔径增大. 随着处理温度的提高, 催化剂的活性降低, 对二甲苯和邻二甲苯的选择性上升. 经500 ℃纯水蒸气处理5 h的MCM-22催化剂, 具有适宜的酸强度和酸类型分布, 有利于甲苯甲醇烷基化反应的进行, 且催化剂维持了较高的催化活性并具有一定的对位选择性(甲苯转化率和对二甲苯选择性分别29.22％和42.16％).     

H-ZSM-5分子筛催化二甲苯异构化的反应机理

采用密度泛函理论(DFT)和ONIOM方法, 研究了H-ZSM-5分子筛上二甲苯异构化机理. 描述了中间体物种和过渡态的结构. 反应物吸附和产物脱附对二甲苯异构化的反应趋势有重要影响. 反应活化能的计算结果表明, 在H-ZSM-5分子筛延伸的孔道结构中, 异构化反应沿着生成间二甲苯的方向进行. 但是较高的脱附能使生成的间二甲苯滞留在分子筛孔道中,其进一步异构化生成对二甲苯具有动力学优势. 对二甲苯产物在分子筛孔道的酸中心上可选择性生成. 在H-ZSM-5分子筛外表面, 不受延伸孔道结构的静电限制时, 二甲苯异构化生成间二甲苯产物, 其可以很容易从活性位上脱附. 非选择性异构化降低了对二甲苯的选择性. 因此, 对H-ZSM-5分子筛外表面改性能够抑制二甲苯的非选择性异构化, 因此限制了反应在分子筛孔道中进行, 提高了对二甲苯的选择性. 二甲苯异构化相对反应速率常数的计算结果也表明, 在分子筛外表面上, 生成间二甲苯的异构化反应速率较快. 升高反应温度会降低对二甲苯的选择性.     

HZSM-5,Co/ZSM-5及Ni/ZSM-5分子筛催化选择性研究(Ⅲ)——甲苯烷基化和间二甲苯异构化的量化处理

根据Kaeding等提出的以HZSM-5作催化剂的甲苯烷基化机理和Guisnet等提出的以HZSM-5作催化剂的间二甲苯异构化机理,用CNDO/2法计算了HZSM-5、Co/ZSM-5、Ni/ZSM-5通道中不同σ络合物的总能量,从理论上解释了HZSM-5和Co、Ni改性的ZSM-5催化剂提高对二甲苯选择性的原因。描述了HZSM-5通道及金属原子在催化反应中的作用。     

ZSM-5-SBA-15复合分子筛制备及甲苯甲醇烷基化性能研究

采用后合成法制备了ZSM-5-SBA-15复合分子筛,通过XRD、FT-IR、BET、NH₃-TPD及吡啶红外等手段表征催化剂的性质。结果表明,ZSM-5-SBA-15既具有微孔结构又具有介孔结构。吡啶吸附和NH₃吸脱附实验结果表明,ZSM-5微孔分子筛的引入使SBA-15介孔分子筛的酸性增强,但与ZSM-5相比,ZSM-5-SBA-15复合分子筛的酸性位没有改变,酸强度有一定的减弱。用固定床评价了该复合分子筛甲苯甲醇烷基化反应的催化性能。结果表明,与常规ZSM-5相比,ZSM-5-SBA-15表现出了较高的对位选择性。     

近临界下HZSM-5催化的甲苯歧化反应

用高压观测池通过可视观测确定了苯、甲苯和对二甲苯等二元系及三元系的临界性质以及甲苯歧化反应混合物临界性质随着反应进程的变化规律；在此基础上，分别研究了近临界区以及高温下以HZSM-5为催化剂的甲苯歧化反应。结果发现，在近临界区甲苯歧化反应的对二甲苯选择性最高，随温度的升高甲苯转化率明显增加，对二甲苯选择性下降。高温下压力对对二甲苯选择性没有影响，转化率随压力升高而提高。     

以对二甲苯氧化为对苯二甲酸为例简要综述一级C–H键活化(英文)

The oxidation of para‐xylene to terephthalic acid has been commercialised as the AMOCO process(Co/Mn/Br) that uses a homogeneous catalyst of cobalt and manganese together with a corrosive bromide compound as a promoter. This process is conducted in acidic medium at a high tempera‐ture(175–225 °C). Concerns over environmental and safety issues have driven studies to find mild‐er oxidation reactions of para‐xylene. This review discussed past and current progress in the oxida‐tion of para‐xylene process. The discussion concentrates on the approach of green chemistry in‐cluding(1) using heterogeneous catalysts with promising high selectivity and mild reaction condi‐tion,(2) application of carbon dioxide as a co‐oxidant, and(3) application of alternative promoters. The optimisation of para‐xylene oxidation was also outlined.     

杯芳烃衍生物的合成和性质的研究5

通过对特丁基杯(4)芳烃的酚羟基的选择性醚化制备了一系列一烃基,1,3-二烃基和四烃基醚,烃基分别含有缩醛、酰胺、氰基等活泼官能团。醚化反应的区域选择性主要取于使用的碱的种类和反应时间的长短。     

大孔沸石催化剂上苯与丙烯液相烷基化反应行为的研究

围绕具有工业实用价值的苯与丙烯液相烷基化制取异丙苯这一课题,对比考察了不同硅铝组成的ＨＹ型和Ｈβ型沸石的催化性能,利用烧炭试验、结炭前驱物萃取方法及色－质谱表征手段探索了沸石催化剂在烷基化反应中的结炭行为。烷基化试验结果表明,β沸石对异丙苯的选择性和催化剂稳定性都明显优于Ｙ型,其异丙苯选择性可达９６ｍｏｌ％以上。同时,提高原料苯烯比、降低反应温度或保持适当高的进料空速能够提高异丙苯的选择性。结炭催化剂的烧炭结果显示,在烷基化反应中Ｈβ比ＨＹ具有较强的抗结炭能力。结炭催化剂的溶剂萃取结果表明,反应中的液相苯能够有效地使催化剂孔道中的结炭前驱物种脱离催化剂表面,从而抑制结炭,提高催化剂的稳定性     

全氟辛基磺酸催化液态烯烃Friedel-Crafts反应的研究

烯烃的Friedel-Crafts烷基化反应(以下简称F-C烷基化反应)一般采用金属卤化物和浓硫酸作催化剂,但两种情况下的后处理都比较复杂,要消耗大量溶剂,催化剂只能一次性使用。近年来,由于苯乙烯与二甲苯反应产物为具有多种工业用途的材料"PXE",国内外相继报道使用不同的催化剂来改进该反应,这些反应各有优点,但均未提及机理和与之竞     

复合离子液体催化碳四烷基化反应性的研究

合成了一种新型的酸性离子液体催化剂——复合离子液体，该离子液体的阴离子具有双金属的配位中心。同时，研究了复合离子液体催化异丁烷与丁烯烷基化反应的规律。结果表明，在搅拌速率大于1500r/min，反应低于20℃，烃酸比2∶1~3∶1，烷烯比大于15，反应停留5min~10min，使用丁烯-2为碳四烯烃反应原料下，复合离子液体催化碳四烷基化所得烷基化油的研究法辛烷值（RON）最高可达100以上，明显优于常规氯铝酸离子液体催化所得烷基化油的质量。     

有机杂化介孔Beta分子筛的合成及在苯甲醇烷基化反应中的应用

针对沸石分子筛在苯甲醇和三甲基苯的烷基化催化反应应用中存在催化活性低及微孔孔道内大量苯甲醇自醚化副反应导致产物选择性低这一难题, 通过引入等级孔结构提高外比表面积和有机杂化修饰封堵微孔孔道的双重策略, 在大幅提升可接触的外表面活性中心数量的同时有效降低苯甲醇进入微孔孔道内发生自醚化副反应, 开发出具有高反应活性及烷基化产物选择性的有机杂化介孔Beta分子筛材料, 大幅度提升了其对苯甲醇和三甲基苯的烷基化反应的催化活性和产物的选择性, 使苯甲醇的转化率从66.8%提升到了99.7%, 烷基化产物的选择性从14.8%提高到50.7%. 本工作为开发高活性及高选择性的烷基化催化剂提供了新的思路.     

不同硅铝比的ZSM-11沸石分子筛的催化性能

合成了一系列硅铝比为31—176的ZSM-11沸石,以甲苯-甲醇烷基化、间二甲苯异构化和甲苯歧化三个反应作为探针反应,研究了它们的催化性能。将其与酸性质和晶胞参数相关联发现,低硅铝比适于甲苯歧化,中硅铝比适于间二甲苯异构化,高硅铝比适于甲苯-甲醇烷基化反应。各反应所需的酸强度为甲苯歧化>间二甲苯歧化>间二甲苯异构化>甲苯-甲醇烷基化。Na~+的存在以及用4-甲基喹啉或(CH_3)_3SiCl中毒,可抑制强酸位,明显提高甲苯-甲醇烷基化反应生成对二甲苯的选择性,尤以(CH_3)_3SiCl中毒的低Al/u.c.的NaHZSM-11最佳。     

碱酸改性ZSM-5分子筛催化剂的噻吩烷基化反应性能研究

以SiO_2/Al_2O_3物质的量比为50的HZSM-5分子筛为原粉,经过一定浓度的NaOH溶液处理后再使用柠檬酸溶液进行酸洗以制备微孔-介孔多级孔HZSM-5催化剂,并研究其在模拟油中的噻吩烷基化反应性能。结果表明,使用柠檬酸溶液进行酸洗可以清除碱处理后孔道内残余的杂质。当柠檬酸溶液浓度为0.5 mol/L时,此时得到的HZ(AC-0.5)催化剂具有适宜的孔径和酸性,因而噻吩烷基化转化率最高,达到95.6%。在HZ(AC-0.5)催化剂上以苯并噻吩作为噻吩衍生物模型化合物,异戊二烯作为烯烃模型化合物,苯作为芳烃模型化合物,分别考察噻吩烷基化反应性能,并分析不同组分的模拟油对噻吩烷基化反应转化率和选择性的影响。结果表明,噻吩烷基化的最佳反应温度是120℃,在该温度下苯并噻吩烷基化的转化率高于噻吩烷基化的转化率,当异戊二烯作为烯烃模型化合物后噻吩的转化率会升高,当苯作为芳烃模型化合物后噻吩的转化率会降低。     

Performance of HZSM-5 as Catalyst for Alkylation of Methyl naphthalene with Methanol in Supercritical Phase

The alkylation of methylnaphthalene（MN） with methanol in the presence of HZSM-5 is a promising route for producing 2,6-dimetylnaphthalene（2,6-DMN） with a high selectivity. However, the conversion of MN is very low and the catalyst will be deactivated rapidly with increasing time on stream. In this study, the effects of the reaction pressure on the reactivity, selectivity and life of the catalyst of alkylation of MN over HZSM-5 modified by BaO were investigated. It was observed that with the enhancement of pressure, the conversion of MN increased, but the selectivity of 2,6-DMN kept unchanged, which was about 40% -42%. When the alkylation was carried out under a supercritical condition, the conversion of MN was 3-6 times higher and the life of catalyst was 25-30 times longer than those at an ambient pressure. The thermogravimetric analyses of the deactivated catalysts at different reaction pressures indicate that the amount of coke deposited on the catalysts was about 10% to 12 %, and the coke-burning reactions mainly took place in a temperature range from 720 to 860 K, and the apparent activation energies of the coke-burning catalysts at 0. 1 MPa（ 10 h） and 7. 6 MPa（ 108 h） were, respectively, 65.90 and 84. 72 kJ/mol. It is concluded from tile results that the supercritical condition is advantageous to enhancing the conversion of alkylation and extraction in situ, and to transporting those high molecular-weight poly-aromatic compounds so as to extend the catalyst life successively.     

铬酸钴催化剂上苯酚和甲醇气相邻位烷基化反应

研究了具有尖晶石结构的铬酸钴及负载钾的铬酸钴催化剂上苯酚和甲醇气相邻位烷基化反应. 结果表明, 相对较高的反应温度有利于提高催化剂的反应活性和2,6-二甲酚的选择性; 随着质量空速的降低, 苯酚的转化率和2,6-二甲酚的选择性逐渐增加, 邻甲酚的选择性逐渐降低, 这表明2,6-二甲酚是邻甲酚进行连续反应的结果. 另外, 钾的引入能明显提高邻甲酚的选择性, 降低苯酚的转化率和2,6-二甲酚的选择性, 原因可能主要是由于负载钾后铬酸钴催化剂上的较强的酸中心数目明显减少所致.     

The miracle role of lattice imperfections in benzene alkylation with methanol over mordenite

Mordenite (MOR) has demonstrated potential as a catalyst for alkylation due to high variability, intrinsic porosity, and outstanding stability. However, the contact probability of benzene and methanol has been limited by typical layered structures of MOR and there is no connection between layers. Here, we report the preparedness of H-MOR via a sequential post-treatment method based on a commercial MOR. H-MOR sample had appeared lattice imperfections inferred from characterization means. The samples were tested with benezene methylation reaction. Results show that the high conversion of benzene and the high selectivity of toluene were obtained from the miracle role of lattice imperfections in the H-MOR sample. Sequentially, based on the study of all catalyst structure and physical properties, a plausible reaction mechanism for the selectivity of the desired toluene was proposed.     

Control of extremely fast competitive consecutive reactions using micromixing. Selective Friedel-Crafts aminoalkylation

Friedel-Crafts reactions of aromatic and heteroaromatic compounds with an N-acyliminium ion pool were studied. The reaction of 1,3,5-trimethylbenzene in a batch reactor gave rise to the selective formation of a monoalkylation product (69%). Presumably, the second alkylation is slower than the first alkylation because of the protonation of the monoalkylation product that decreases its reactivity. The reaction of 1,3,5-trimethoxybenzene, however, gave rise to the formation of both monoalkylation (37%) and dialkylation (32%) products. Disguised chemical selectivity due to faster reaction than mixing seems to be responsible for the lack of selectivity. The use of micromixing was found to be quite effective to solve this problem to increase the selectivity. The monoalkylation product was obtained in 92% yield together with a small amount of the dialkylation product (4%). The reaction with various aromatic and heteroaromatic compounds revealed that the low mono/dialkylation selectivity was observed only for highly reactive aromatics. In such cases, the use of micromixing was quite effective to improve the selectivity. On the basis of micromixing, the selective sequential dialkylation using two different N-acyliminium ions was achieved. CFD simulations using a laminar flow and finite-rate model are consistent with the experimental observations and clearly indicate the importance of mixing.     

ZSM-5分子筛上烷基化过程中“反向效应”的产生及其克制方法

在综述甲苯择形烷基化机理并分析产生“反效应”的原因的基础上,提出了克制的“反向效应”的设想。Ｓｂ２Ｏ３,ＴｉＣｌ４,ＳｉＣｌ４,Ｈ３ＰＯ４,Ｍｇ（Ａｃ）２等化合物对分子筛进行改性,测定改性前后分子筛的表面酸性与孔结构,关联乙基化反应结果,证实中强酸中心在乙基化反应中的重要作用,认为保持孔道的畅通是解决“反应效应”的关键。并采用了Ｋ－Ｍｇ改性,制备出对甲苯乙基化具有高初活性和高对位选择性的催化剂。     

The alkylation reaction of benzene with methanol to produce toluene: Y-C and Y-CCs catalyst

The secondary reaction of toluene is difficult to be suppressed in benzene alkylation with methanol over conventional acidic zeolite catalysts. Moreover, the formation of coke yet remains a challenging problem. In this study, Na-Y zeolites were modified with ammonium carbonate (AC), citric acid (CA) and caesium nitrate(CN) to evaluate the alkylation of benzene with methanol, which was also characterized by XRD, SEM, FT-IR, N₂ adsorption and Py-IR. For the Na-Y treated with AC-CA-CN, not only the catalytic selectivity for the alkylation of benzene with methanol was improved (the total selectivity of toluene and xylene was 97.9% and toluene selectivity was 86.4%), but also the quantity of coke was greatly decreased.     

Alkylation of isobutane with C<Subscript>4</Subscript> olefins under conventional and supercritical conditions

The solid acid alkylation of isobutane with butylenes on the ultrastable zeolite Y is studied in the temperature range from 120 to 150°C and in a pressure range of 20–120 atm. The catalyst service life becomes longer on passing from the conventional (liquid- and gas-phase) conditions of alkylation to supercritical conditions. The maximum period of complete butylene conversion at 150°C and 120 atm is 3.5 h. The composition of the reaction products is determined by the phase state of the reaction mixture, the reaction time, and the conversion of the C₄ olefins. When the alkylation is carried out under supercritical conditions, the C₈ hydrocarbon selectivity varies between 30 and 40%. Thermoanalytical data suggest that the surface of the spent catalyst contains carbon deposits indicating the formation of oligomeric and cyclic structures.