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研究了耐温阳离子交换树脂、γ-氧化铝、分子筛等固体酸催化剂对甲醇气相脱水制二甲醚反应的催化性能,酸碱滴定、氨程序升温脱附、X射线衍射、热重-差热分析对催化剂样进行了表征。结果表明,达到相同的甲醇转化率,催化反应温度顺序为:t(γ-氧化铝)t(树脂)t(分子筛)。以耐温阳离子交换树脂为催化剂,甲醇转化率低于70%,当反应温度高于190℃时树脂很快失活;以γ-氧化铝为催化剂,在280~380℃之间,甲醇转化率高于80%,当温度为365℃时寿命大于500 h;以分子筛为催化剂,在200~280℃之间,甲醇转化率高于85%,分子筛易积碳失活。 相似文献
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综述了CO2加氢直接制二甲醚双功能催化剂的研究进展情况,重点介绍了双功能催化剂中甲醇合成活性组分、甲醇脱水活性组分和双功能催化剂的制备方法.CuO-ZnO基复合氧化物是最常用的甲醇合成活性组分,其铜锌比、制备方法和条件及助剂等显著影响双功能催化剂的性能.由于反应体系中含有较多的水,HZSM-5分子筛比γ-Al2O3更适合作为双功能催化剂的甲醇脱水活性组分. 相似文献
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在甲醇气相脱水合成二甲醚反应中,考察了催化剂酸性及反应工艺条件对反应的影响。分子筛的Bronsted酸中心和Lewis酸中心都是甲醇脱水反应的活性中心,而强酸中心是烯烃产生的主要场所。研究表明,采用硅铝比为60的HZSM-23分子筛作为催化剂,适宜的工艺条件为:反应质量空速5 h-1,温度300℃,压力0.1MPa,甲醇转化率为97.6%,二甲醚选择性为95%。 相似文献
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双功能催化剂是一步法合成二甲醚的关键。双功能催化剂两种活性组分之间处于最佳匹配关系时,可获得较高的二甲醚收率。二甲醚合成过程中,不仅要求分子筛表面分布较多的酸活性位,而且还要有合适的酸强度。合成二甲醚过程中,优化脱水催化剂使其与甲醇合成催化剂产生"协同效应"是研究重点。为获得较高的二甲醚收率,甲醇脱水催化剂具有合适的酸性是双功能催化剂改性的一个方向。 相似文献
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以多级孔Y分子筛为酸性组分,采用孔饱和浸渍法制备了含分子筛的CoMoP/Al2O3加氢催化剂,通过X射线衍射、N2吸附-脱附、高分辨透射电镜、吡啶吸附红外光谱等表征手段对分子筛样品进行物化性质分析,并以4,6-二甲基二苯并噻吩为模型化合物,在固定床高压微反装置上考察多级孔分子筛的加入对4,6-二甲基二苯并噻吩加氢脱硫反应活性的影响。结果表明,多级孔Y分子筛较高的外表面积和介孔体积有利于提高分子筛B酸中心的可接近性。与参比剂CoMoP/Al2O3-Y相比,B酸酸量较高的多级孔Y分子筛催化剂的酸催化反应活性明显增强,总加氢脱硫反应活性提高。随着分子筛强B酸酸量的增加,含Y分子筛催化剂的甲基转移反应活性明显提高。 相似文献
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丁烯异构化催化剂进展 总被引:4,自引:0,他引:4
回顾了丁烯骨架异构化反应的热力学、催化剂的活性中心以及异构化催化剂的研究进展。热力学研究显示 ,异构化反应在低温下运行比较有利 ;活性中心的研究显示 ,中强B酸中心为异构化反应的活性位 ,强的B酸中心易诱发二聚、裂解等副反应 ,酸度和孔结构的调节相结合才能实现丁烯的选择性异构 ;催化剂异构化性能对比显示 ,FER、SAPO -11等 10元环分子筛是目前最有发展潜力的异构化催化剂。 相似文献
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《Egyptian Journal of Petroleum》2015,24(3):289-297
Catalytic dehydration of methanol to dimethyl ether (DME) was investigated using physically and chemically modified H-Mordenite and H-Beta zeolites as catalysts. Physical modification was carried out using ultrasonic wave’s energy, while chemical modification was performed through impregnation in aluminum nitrate followed by calcination. The produced solid catalysts were evaluated as selective catalysts for the dehydration of methanol to dimethyl ether at 100–250 °C performed at three different contact times. Chemical and structural characterizations of the solid catalysts were identified using XRD, FT-IR, TEM, SEM and NH3-TPD. Ultrasonication physical mixing of solids proved as useful tool of preparation, producing fine reordered crystals of nanocomposite zeolites with novel morphology. The newly ordered crystals were distinguished by their frame work structure, acidic properties, crystal and particle sizes, unit cell volume, pore opening, and favorable catalytic activity of 100% selectivity to DME at 200 °C for all contact times studied. The effects of Al2O3 on the dispersion and interaction within the nano-zeolite crystals and hence on the catalytic dehydration of methanol were verified as the major influence toward utmost selectivity. 相似文献
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含碱土金属分子筛对FCC催化剂催化性能的影响 总被引:2,自引:1,他引:1
通过在FCC催化剂中引入含碱土金属的分子筛,提高了FCC催化剂的重油转化能力和氢转移反应活性,同时催化剂还保持良好的焦碳选择性,着重考察了含碱土金属分子筛中不同碱土金属离子和分子筛类型对FCC催化剂性能的影响;从催化剂酸性质的变化对含碱土金属分子筛的作用原因进行了初步的探讨。结果表明,含Mg,Ca分子筛的FCC催化剂具有重油转化能力强,氢转移反应活性高及焦碳选择性好等特点,含Mg,Ca分子筛的引入,改进了FCC催化剂的性能,这与催化剂酸性发生变化,即总酸量以及B酸对L酸的比例增加,特别是强酸量减少,中强酸比例提高有关。 相似文献
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Abstract HZSM-5 zeolites modified by MgO, CaO, and ZnO were prepared by impregnation and bifunctional catalysts were prepared by modified HZSM-5 zeolites and JC207 catalyst (a catalyst for methanol synthesis, which has been industrialized in China). Evaluation of catalytic activity was conducted in a fixed-bed reactor. Results show, with proper basic oxide-modified zeolite, a Br?nsted acid site (strong acid sites) shift to Lewis acid site (weak acid sites). Weak and less strong acid sites on HZSM-5 zeolite are activity centers for the formation of dimethyl ether (DME), whereas strong acid sites for by products such as hydrocarbons. Consequently, the selectivity of CO2 and hydrocarbons decrease, especially with zeolite modified by CaO. 相似文献
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SulfidationofNi,MoContainingYZeolitesandReactivityforThiopheneHydrodesulfurizationCuiJun,GaoZi(DepartmentofChemistry,FudanUn... 相似文献