Intensified shape selectivity and alkylation reaction for the two-step conversion of methanol aromatization to p-xylene

Two-step conversion of methanol to aromatics via light hydrocarbons can significantly improve the conversion stability compared with direct aromatization of methanol, but it remains a challenge to achieve a high p-xylene(PX) selectivity. Herein, silica coating was firstly used to passivate external acid sites of ZSM-5 catalyst for the aromatization of light hydrocarbons by the chemical liquid deposition method.With the increase of SiO₂ deposition, the density of the external acid site...     

基于PX选择性强化的短流程甲苯甲醇甲基化PX生产新工艺

基于改性的高硅铝ZSM-5催化剂反应动力学模型,本文探讨了甲苯甲醇甲基化反应中影响对二甲苯（PX）选择性的因素,提出了基于选择性强化的短流程甲苯甲醇甲基化PX生产工艺,并从原料利用率、能耗以及经济指标等角度,与已有工艺进行了对比分析。结果表明,在短停留时间、高甲苯/甲醇进料比、高稀释剂/甲醇进料比、较低反应温度和压力条件下,可以促使PX在二甲苯异构体中的选择性达到99.7 %以上。短流程PX生产工艺规避了二甲苯异构体的分离,具有原料利用率高、能耗低、工艺简单的特点,具有良好的经济性。当前工艺研究进一步提升了甲苯甲醇甲基化PX生产工艺的技术竞争力,利用非石油基的甲醇,有助于形成煤化工和石油化工技术互补、协调发展的新格局。     

甲苯甲醇选择性烷基化技术研究进展

近年来,甲苯甲醇选择性烷基化技术因产物中对二甲苯选择性高和产物易分离等优点备受关注。综述了国内外甲苯甲醇烷基化制对二甲苯的研究进展,包括甲苯甲醇烷基化的反应机理、工艺技术和催化剂失活研究。     

p-Selectivity of the Al-MFI substitutional series in alkylation of toluene

Al-MFI and various kinds of metallosilicates were synthesized hydrothermally under various conditions. When fumed silica was used as the Si source, we could observe a regular variation in the crystal morphology from cubic to planar shape of elongated prism as the Si/Al ratio of the Al-MFI increased. For metallosilicates the reversed variation in morphology was detected with respect to the amount of metal per unit cell. In regard to the crystal symmetry, the transition from orthorhombic to monoclinic phase took place as the Si/Al ratio changed from 63 to 99, whereas all the metallosilicates had orthorhombic phase because of the metal ions present in the non-framework. A careful XRD analysis indicated that the intensity ratio of the 8.8° 2θ peak to the 7.8° 2θ peak was strongly influenced by the morphology. It turned out that, as the peak ratio increased, the morphology tended to change from cubic to planar shape. This leads to the speculation that thep-selectivity might be related to the said peak ratio and this was confirmed by experimental data obtained from toluene alkylation.     

甲苯甲醇选择性烷基化催化剂研究进展

甲苯甲醇烷基化是生产对二甲苯的一条新工艺路线,其原料价格低廉、对二甲苯选择性高、产物分离简单,因此引起国内外学者的极大关注。活性和选择性高、稳定性好的催化剂是甲苯烷基化技术应用的关键。综述了国内外甲苯甲醇烷基化催化剂的研究进展,包括水热处理法、浸渍法、预积炭法等。指出水蒸气改性可以提高催化剂寿命,浸渍法的操作简单、重复性好,这两种方法是目前分子筛改性的常用方法。通过对分子筛改性来制备高选择性甲苯甲醇烷基化催化剂己经不再是难题,在维持较高活性和选择性的基础上,提高催化剂稳定性,使其具备工业应用价值,是未来甲苯甲醇烷基化技术研究的重点。     

甲苯和甲醇烷基化反应热力学分析与计算

甲苯甲醇烷基化制备对二甲苯是一条增产对二甲苯的新的工艺路线。文章对甲苯甲醇烷基化反应过程进行了较为详尽的热力学分析,并用Matlab语言计算得到不同温度下相关反应的Gibbs自由能、平衡常数以及产物之间的平衡关系等。结果表明,甲苯甲醇烷基化制备对二甲苯副产低碳烯烃在热力学上均能自发进行并能达到很高限度,但是对二甲苯和低碳烯烃的产率受热力学平衡限制。因此,开发高选择性的催化剂将具有广阔的应用前景。     

甲苯甲醇烷基化反应器模拟与分析

基于甲苯甲醇烷基化反应动力学,分别建立了一维拟均相固定床反应器和二维拟均相固定床反应器的数学模型。在一维拟均相固定床反应器的模拟中,可以得到甲苯转化率、各种物质的摩尔分数以及反应温度随反应器轴向的变化规律。为了更详细地了解反应器的有关行为,反应器中的传质过程、传热过程、反应过程及流体流动需同时考虑。对于二维拟均相反应器的模拟,不仅可以获得甲苯转化率、反应温度等在轴向的变化规律,而且可以获得其在反应器径向上的分布。二维反应器模拟结果显示,流体的流动对反应器的行为具有十分重要的影响。     

甲苯甲醇烷基化合成对二甲苯催化剂研究进展

甲苯甲醇烷基化是新型高选择性合成对二甲苯的方法,可以解决石化行业甲苯和甲醇过剩问题,具有较高的工业开发价值。在具有B酸中心及特殊孔结构的分子筛催化下,甲苯甲醇发生苯环上亲电取代反应得到对二甲苯。甲苯甲醇烷基化催化剂主要有Y沸石催化剂、SAPO及MCM-22和ZSM-5分子筛催化剂等,研究较多的是ZSM-5分子筛催化剂。通过对ZSM-5分子筛进行金属、非金属或复合改性后,可以显著提高烷基化反应转化率和选择性。未来研究的主要目标是获得选择性高且稳定性好的催化剂。     

Improved film evaporator for mechanistic understanding of microwave-induced separation process

Microwave-induced film evaporation separation process has been reported recently to separate the polar/nonpolar mixture. However, the efficiency of the separation is still too low for practical applications, which requires further enhancement via different strategies such as optimization design of evaporator structure. In addition the depth understanding of the separation mechanisms is great importance for better utilization of the microwave-induced separation process. To carry out these investigations, a novel microwave-induced falling film evaporation instrument was developed in this paper. The improvement of the enhancement effect of microwave-induced separation was observed based on the improved film evaporator. The systematic experiments on microwave-induced separation with different binary azeotropic mixtures (ethanol-ethyl acetate system and dimethyl carbonate (DMC)-H₂O system) were conducted based on the new evaporator. For the ethanol-ethyl acetate system, microwave irradiation shifted the direction of evaporation separation at higher ethanol content in the starting liquid mixture. Moreover, for DMC-H₂O system microwave-induced separation process broke through the limitations of the traditional distillation process. The results clearly demonstrated the microwave-induced evaporation separation process could be commendably applied to the separation of binary azeotrope with different dielectric properties. Effects of operating parameters are also investigated to trigger further mechanism understanding on the microwave-induced separation process.     

Synthesis of bifunctional ion-exchange resins through the Arbusov reaction: Effect on selectivity and kinetics

Bifunctional ion-exchange resins are synthesized from vinylbenzyl chloride—styrne copolymers. The two types of functional groups are introduced by an Arbusov reaction followed by sulfonation. The effect of ligand ratios, macroporosity, and matrix rigidity on the complexation of Eu (III) from solutions of low pH is quantified. It is found that ion complexation kinetics and selectivity are maximized with resins having both sulfonic and phosphonic acid ligands. Maximum metal ion complexation rates depend on a balance between chemical interactions (i.e., a bifunctional network interacting with a given substrate through an access and a recognition mechanism) and physical parameters (i.e., matrix porosity and rigidity). Structural integrity must be maintained through an appropriate crosslink level in order for the advantage of bifunctionality to be maintained in low-pH solutions. © 1994 John Wiley & Sons, Inc.     

Tuning the mesoscopically structured ZSM-5 nanosheets for the alkylation between toluene and methanol

Mesoscopically structured ZSM-5 nanosheets were prepared as highly active catalysts for the alkylation between toluene with methanol. The results showed that the Brønsted acid sites of ZSM-5 nanosheets were mainly distributed on the external surface in aluminum-rich zeolites owing to the charge-balance between positive quaternary ammonium cation (N⁺) in C_ph-10-6-6, Na⁺ ions and negative aluminosilicate species. In addition, it revealed that high alkalinity was easier to depolymerize the Si O Si species in Aluminum-rich synthesis gel, and the high alkalinity was required for silica-rich systems to dissolve silica species in order to finish the self-assemble process, leading to ZSM-5 nanosheets with high alkalinity presenting enhanced catalytic performance. Moreover, the optimized ZSM-5-50-2.5 was effective for the alkylation between toluene and methanol with toluene conversion of up to 50%, and it was stably operated for 48 h under the harsh conditions of WHSV = 32.5 h⁻¹ with a desired stability.     

Sorption selectivity of NaY- and KY- zeolites for xylene and toluene

The selective adsorption capacities of NaY- and KY-zeolites for xylene isonners and toluene were investigated by measuring the rate of unidirectional diffusion in a batch adsorber and the breakthrough behavior in a fixed-bed column. The sequence of sorption selectivity was found as m-xylene> toluene > p-xylene with NaY-zeolites and as the converse with KY-zeolites. The reversal of selectivity could not be explained by the molecular sieving effects but by the interactions between adsorbing molecules and cation as well as among adsorbing molecules themselves.     

室温离子液体及其在Friedel-Crafts烷基化反应中的应用

离子液体被誉为“设计者溶剂”,有着独特的性质。从离子液体的发展、特性、合成及其在Friedel-Crafts烷基化反应中的应用对其进行了介绍。     

对甲酚烷基化反应催化剂的研究进展

主要从酸性催化剂的发展历程全面综述了分子筛、固体超强酸、离子交换树脂、杂多酸、离子液体等多种酸性催化剂的优点和缺点,并总结出对甲酚在不同催化剂作用下反应产物区域选择性的结果。通过对多种催化剂的特性和反应结果对比着重介绍了离子液体催化剂,离子液体同时拥有液体酸高密度酸性和固体酸易分离不挥发的优点,在保持着浓硫酸酸性强度的同时,还具有低蒸气压、热稳定性高、对环境无污染、功能化设计的优良特性,这为今后对甲酚烷基化反应绿色催化剂的发展提供了重要的研究方向,避免了目前工业上常用液体酸催化剂存在的污染环境设备和安全隐患等重大问题。     

Anti-carbon deposition performance of twinned HZSM-5 encapsulated Ru in the toluene alkylation with methanol

Toluene methylation with methanol to produce para-xylene has been extensively and intensively studied.However,the methanol-to-hydrocarbons(MTH) side reaction in this reaction is difficult to be inhibited,which will cause a mass of carbon deposition and cover the catalyst surface,resulting in catalyst deactivation.Here,a dual-functional Ru@HZSM-5 catalyst with high para-selectivity and low carbon deposition was prepared by encapsulating Ru metal with HZSM-5.According to catalytic performance stud...     

佐米曲坦的Fischer吲哚环合工艺改进

以(S)-4-(4-氨基苄基)噁唑烷-2-酮为起始原料,经重氮化、还原制得(S)-4-(4-肼基苄基)噁唑烷-2-酮.再和4,4-二乙氧基-N,N-二甲基丁胺缩合后经回流环合制得选择性5-HT1B/1D激动剂佐米曲坦.通过比较不同的环合条件,确定在pH 3～4、回流温度下、反应5 h的条件下环合效果较好,总收率达45.3%.改进后的工艺操作简便易行.     

甲醇甲苯烷基化流化床反应器的数值模拟

利用甲醇甲苯烷基化工艺生产对二甲苯具有良好的应用前景。甲醇甲苯烷基化催化剂较易积炭失活,且反应存在明显热效应。流化床因传热传质性能好、易实现催化剂连续再生,适合用作甲醇甲苯烷基化反应器。本文采用离散颗粒模型,对甲醇甲苯烷基化流化床反应器进行了数值模拟研究,重点考察了进料比、反应压力、分段进料对反应特性的影响。结果表明,当甲苯进料量给定时：降低反应物中甲苯甲醇比可有效提升对二甲苯产率和选择性,但产物中对二甲苯和烯烃摩尔比值较低;提高反应压力可显著提升甲醇和甲苯转化率,但会降低对二甲苯选择性;在低苯醇比基础上采用甲醇分段进料方式不仅可有效提高甲苯利用率,还可灵活调节产物中对二甲苯和烯烃比率;流化床反应器气体返混不利于获得高对二甲苯选择性,且操作条件变化会造成流化床反应器内气固流动改变,导致气固接触效率或反应物局部分压发生改变,这亦将对反应转化特性造成显著影响。这些结果对于流化床反应器优化和放大具有一定的指导意义。     

间／对混甲酚的烷基化反应研究

间／对混甲酚与异丁烯在酸性催化剂条件下进行烷基化反应,将烷基化产物进行气质联用（GCMC）分析,目标产物2,6二叔丁基对甲酚与4,6-二叔丁基间甲酚含量分别为21．02％和45．95％,转化率分别为83．80％和89．12％。