甲醇制烯烃流化床内流化特性的多尺度CFD模拟

近些年，我国成功开发了以煤为原料的甲醇制烯烃(Methanol to Olefins, MTO)生产工艺和技术，带动煤制烯烃产业的快速发展，保障了国家能源安全。流化床式反应器是MTO工业生产的核心反应装置，通过计算流体力学(Computational Fluid Dynamics, CFD)方法深入认知MTO流化床内的流化特性规律具有重要的意义，它可以从理论上更加准确地指导MTO流化床的优化与放大。本工作采用基于宏观?亚网格层次的气泡EMMS曳力和传统TFM耦合计算的多尺度CFD方法，对工业尺度MTO流化床内的多相流化行为进行了三维数值模拟。模拟结果表明，该多尺度CFD方法考虑了气泡结构对气?固相间曳力的影响，能较准确地预测MTO流化床内轴向颗粒浓度的“S-型”分布规律，且得到实验数据的验证；所预测的径向颗粒浓度分布呈现出经典的“环?核”分布规律，气体/颗粒的轴向时均速度在径向上的分布也与实际情况相互佐证，表明该多尺度CFD方法显著改善了基于均匀曳力的传统TFM对于宏观流场的预测能力。下一步工作将多尺度CFD方法拓展应用于MTO流化床优化放大及反应特性的研究。     

甲醇制低碳烯烃技术研究进展

甲醇制低碳烯烃(MTO)技术提供了一种以煤制甲醇为原料生产烯烃的途径。本文重点讨论了国内外MTO工艺的发展概况、工艺流程和使用现状,介绍了催化剂研究进展和MTO工艺的反应机理,对MTO技术应用及其制约条件进行了初步分析,并根据我国的实际情况对其开发应用前景进行了展望。     

Well-defined (supra)molecular structures in zeolite methanol-to-olefin catalysis

Methanol-to-olefin (MTO) conversion on microporous silico-aluminophosphates is particularly well-suited for the application of molecular-level concepts to the development of well-defined supported catalysts. The active site of a typical MTO catalyst is a nm-size inorganic cage with an essential organic component. Opportunities for altering the selectivity of such catalysts include tailoring the organic component and modification of the cage with additional inorganic material through ship-in-a-bottle synthesis. The latter possibility has already been realized experimentally by the development of a useful and practical phosphate-modified catalyst.     

Synthesis of hierarchical ZSM-5 microspheres with superior performance for catalytic methanol-to-olefin conversion

Methanol-to-olefin (MTO) conversion on zeolites has encountered severe coke deposition and rapid deactivation. Creating different levels of porosity is essential to mitigate such issues. Herein, we demonstrate a facile and green strategy to synthesize uniform and hierarchically macro/mesoporous ZSM-5 microspheres by combining spray-freeze drying and steaming-assisted crystallization (SAC). The structure, crystallinity, and porosity of the zeolite microspheres are controlled by adjusting the water/gel mass ratio and time in the SAC process. The structure evolution during the SAC process is revealed. In the catalytic MTO reaction, the representative hierarchically porous ZSM-5 catalyst exhibits superior catalytic performance. At a very high weight hourly space velocity of 18 h⁻¹, it shows a dramatically prolonged lifetime (47 h at >99% conversion) and much-improved selectivity to ethylene and propylene compared with the conventional microporous ZSM-5 and nano-sized ZSM-5. The enhanced performance is originated from the hierarchical structure and suitable acidity of the ZSM-5 microspheres.     

t-ZrO2/SAPO-34质量比对t-ZrO2/SAPO-34复合催化剂物化性质及其甲醇制烯烃催化性能的影响

采用介孔t-ZrO2对微孔SAPO-34分子筛进行复合改性,利用水热包覆技术制备了t-ZrO2/SAPO-34复合催化剂,研究了t-ZrO2与SAPO-34质量比对复合催化剂物化性质和MTO催化性能的影响。采用XRD、FT-IR、SEM、NH3-TPD和BET等手段对不同复合催化剂的晶相组成、骨架结构、微观形貌、表面酸性及孔结构进行分析表征。结果表明,质量比对t-ZrO2/SAPO-34复合催化剂的物化性质和催化性能影响较大。过高或过低t-ZrO2:SAPO-34质量比制得复合催化剂中SAPO-34分子筛结晶度和骨架结构特征均有所减弱,分别呈现以介孔为主和以微孔为主的孔结构特征;当质量比为1:1时,制得复合催化剂形成了包覆相结构和微-介孔层级结构（微孔比表面积112.91 m2·g-1,介孔比表面积176.02 m2·g-1,总比表面积为288.93 m2·g-1,总孔容0.19 cm3·g-1）,总酸量较大（0.344 mmol/g）;在常压、反应温度380 ℃、N2流速20 mL·min-1、进料空速2 h-1MTO反应条件下,复合催化剂表现出优越催化性能、稳定性及反应寿命,甲醇转化率和低碳烯烃选择性分别达100%和90.54%,催化寿命达1130 min,与单一SAPO-34分子筛相比,催化寿命延长了768 min。     

用于甲醇制烯烃SAPO-34分子筛的研究进展

具有CHA结构的SAPO-34分子筛因其优异的理化性质被认为是甲醇制烯烃(MTO)工艺的最佳催化剂,但CHA结构中狭窄的八元环孔会限制扩散,使催化剂易于失活降低使用寿命.本文从构建多级孔结构和减小分子筛粒径入手,综述了具有优异的MTO催化性能的多级孔和纳米级SAPO-34分子筛的最新进展,分析不同制备方法对SAPO-3...     

ZSM-5分子筛在甲醇转化制烯烃领域应用的研究进

综述了ZSM-5分子筛在甲醇制烯烃反应特别是在甲醇制丙烯反应中的应用。介绍在接近工业反应条件下甲醇在ZSM-5分子筛上生成烯烃的反应机理,在较高反应温度下高碳数烯烃裂解是导致轻烯烃形成的主要反应路径;分析ZSM-5分子筛酸性及粒径对产品选择性及催化剂寿命的影响,由于ZSM-5分子筛酸性较强,直接用于甲醇制烯烃反应时低碳烯烃的选择性不高,而粒径小的ZSM-5分子筛扩散性能好,因而丙烯选择性得到提高。重点介绍小晶粒ZSM-5分子筛的研究进展,指出目前ZSM-5分子筛的研究方向一是对其进行酸性改性,二是制备酸度适中、粒径合适和具有介孔的多级结构ZSM-5分子筛。     

甲醇制烯烃原料供需及可获性分析

研究了甲醇行业和甲醇制烯烃的现状及发展趋势,对外购甲醇制烯烃项目的原料可获性进行了分析,提出了此类项目控制甲醇成本的相关建议。     

Effect of SiO2/Al2O3 ratio on the conversion of methanol to olefins over molecular sieve catalysts

A series of SAPO-34 molecular sieves with different SiO₂/Al₂O₃ ratios have been synthesized for the methanol-to-olefin (MTO) reaction. Their physico-chemical properties are characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and N₂ adsorption-desorption. The results are compared with those of the commercial HZSM-5, which show that the crystallinity and particle diameter of SAPO-34 as well as HZSM-5 increase with SiO₂/Al₂O₃ ratio. The variation of BET surface area of SAPO-34 is different from that of HZSM-5 and the sample with SiO₂/Al₂O₃ ratio of 0.4 exhibits the highest BET surface area. FT-IR spectra indicate that HZSM-5 has both Br?nsted and Lewis acid sites and Br?nsted acid sites are stronger, whereas SAPO-34 samples are dominated only by Lewis acid sites. When the SiO₂/Al₂O₃ ratio increases, propylene and butylenes become the predominant product of the MTO reaction over HZSM-5. In contrast, the main products of this reaction catalyzed by SAPO-34 are ethylene and propylene. According to the product distribution, the reaction mechanism over HZSM-5 catalysts is proposed.     

流态化技术在甲醇制低碳烯烃装置中的应用

本文总结了甲醇制低碳烯烃(MTO)的发展历程,根据MTO反应机理及反应特点,评述了各类MTO工业反应型式的适用性,认为流态化反应器和再生器之间的循环适合于MTO反应热效大、催化剂寿命短的特点。中国神华煤制油化工有限公司包头煤化工分公司1.80×106 t/d的MTO工业示范装置近3年的运行数据表明流化床技术非常适合于MTO反应。