共查询到20条相似文献,搜索用时 62 毫秒
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为合成不同硅铝比的MCM-22分子筛,对分子筛配料中的硅铝比、碱度、模板剂和晶化助剂用量等进行了考察,并用X射线衍射、扫描电镜、电感耦合等离子体发射光谱、X射线光电子能谱仪及氮气吸脱附等手段对样品进行了表征。结果表明,以哌啶(PI)为模板剂、硼酸(BA)为晶化助剂,在n(OH-)/n(SiO2)为0.03~0.20、n(PI)/n(SiO2)大于0.03及n(BA)/n(SiO2)大于0.05的条件下,可得到硅铝比为25~500的MCM-22分子筛。与以六亚甲基亚胺为模板剂相比,以哌啶为模板剂制得的MCM-22分子筛具有更小的晶粒尺寸和更大的比表面积。 相似文献
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以三乙胺法合成SAPO-34分子筛的母液为模板剂,进行分子筛的合成研究,采用色谱对合成液中的三乙胺含量进行测定,并利用XRD、SEM、TG、XRF、NH3-TPD和N2吸附-脱附对产品进行表征。结果表明,SAPO-34分子筛合成过程中,大量三乙胺残留在母液中,产品中三乙胺含量仅为原料的5. 35%。利用母液制备的M1分子筛具有更高的结晶度,晶粒尺寸大幅减小至约1μm,比表面积和分子筛产率也大幅增加,分别为725. 85 m2·g-1和83. 36%,产生更多的介孔,有更多的硅原子进入到分子筛骨架中,使分子筛的强酸酸量及酸强度得到有效改善。探究晶种在合成过程中的作用发现,晶种能够替代部分模板剂起到结构导向作用。 相似文献
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Beta沸石分子筛是一种在化工领域应用较为广泛的催化材料。目前制备出的Beta沸石分子筛的粒径大多数是微米级,纳米级的制备研究相对薄弱。针对于此,采用单模板剂(TEAOH)或添加第二模板剂,主要有聚乙烯醇(PVA)、羧甲基纤维素钠(CMC)以及三乙醇胺(TEOA)来制备纳米级Beta沸石分子筛,探索一条适合工业大规模生产的简单可行的制备路径。 相似文献
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不添加有机模板剂,采用较廉价的硅酸钠和铝酸钠分别作为硅源和铝源,经由两步法合成粒度分布均匀且晶型较好的亚微米A型沸石。研究了经不同陈化时间后硅铝凝胶结构发生的变化及经过晶化后产物的粒径变化。结果表明:陈化时间为0~85h时,主要表现为诱导成核,在这段时期硅铝凝胶中对A型沸石成核过程有重要影响的四元环、双四元环数量显著增加,而陈化时间为85~139h主要表现为晶核的生长;随着陈化时间的延长硅铝凝胶中SiO2/Al2O3逐渐减小,且尺寸也逐渐变小;在0~85h区间,合成最终产物的平均粒径随着陈化时间延长而减小,在85h时最小,可达500nm左右;继续延长陈化时间至139h将导致小颗粒A型沸石发生团聚,且形貌也变的不规整。 相似文献
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铵型沸石分别进行微波磷、复配表面活性剂改性并处理脱硫废水中的有机物.利用正交法分别考察两沸石对有机物最佳处理条件,通过扫描电镜观测其表观形态及孔隙程度.通过加权、极差分析得出处理有机物影响因素的权重及主要影响因素,借助orign建立主要影响因素与有机物吸附率的关系.结果表明:两沸石对有机物最佳处理条件均为沸石投加量6 g、有机物浓度35 mol/L、吸附温度30℃、吸附时间5h;此时,有机物吸附率分别为85%、86.18%.沸石投加量、吸附温度分别为微波磷、复配表面活性剂改性沸石处理有机物的主要影响因素.改性铵型沸石的研制为火力发电系统低污染化处理脱硫废水提供一种新型处理材料,并对有机物的去除提供参考. 相似文献
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四丁基氢氧化馆相转移催化合成N,N—二乙基苯胺的研究 总被引:4,自引:0,他引:4
以苯胺和溴乙烷为反应原料,以四丁基氢氧化铵作相转移催化剂,采用六因素五水平正交设计实验方法,研究了合成N,N-二乙基苯胺的反应时间、反应湿度了、催化剂用量、反应物摩尔比、氢氧化纳溶液浓度及用量各反应因素对目的产物产率的影响,发现了上述各反应因素影响目的的产物产率的规律,提出了常压合成目的产物的工艺条件。 相似文献
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以苯胺和溴乙烷为原料 ,用四乙基氢氧化铵作相转移催化剂 ,在常压下合成N ,N 二乙基苯胺。研究了各反应因素对目的产物收率的影响 ,并提出了优惠工艺条件。 相似文献
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《分离科学与技术》2012,47(9):1356-1360
Adsorption of tetraalkyl ammonium hydroxide (TAAH) with mesoporous silica such as MCM-41 and MCM-48 has been investigated. The adsorption of TAAH with the mesoporous silica increases with increase in pH of the aqueous solution. The maximum adsorption amounts of TAAH with the mesoporous silica, determined by Langmuir isotherms, correspond to the relationship between the pore diameter of the mesoporous silica and the molecular size of TAAH, while no significant relationship is observed with both the specific surface area and the amount of silanol group of the mesoporous silica. Mesoporous silica having large pore diameter is applicable to the adsorptive separation of TAAH from the effluent solution. 相似文献
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Modified beta zeolites were applied as catalysts for the Fries rearrangement reaction. The properties of the modified zeolites were characterized by NH3-TPD, n-hexane and 1,2,4-trimethylbenzene adsorption. Modification with SiO2 did not block the pores of the beta zeolite but reduced the number of acid sites on the surface. However, when the beta zeolite was modified with Ce2O3, the number of acid sites determined by NH3-TPD increased, which indicated that new acid sites are created by the interaction of cerium oxide and zeolite. Modified beta zeolites and H-beta were applied as catalysts for the Fries rearrangement of phenol acetate. Reaction over H-beta has low selectivity and the catalyst is easily deactivated. SiO2 modification of the catalyst increases the selectivity of the reaction but decreases the conversion. Ce2O3-modified beta zeolites show higher catalytic activity and rearrangement selectivity in the reaction than other catalysts. The stability of the catalyst is also improved after Ce2O3 modification. About 70% selectivity and 60-80% conversion can be achieved over 16 wt% Ce2O3-modified beta zeolite. 相似文献
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Enhancement of the basic properties of the X zeolite with FAU framework has been carried out during synthesis, without further treatment such as ion-exchange or impregnation. Control of the washing stage enables retention of the optimum amount of alkaline hydroxides, which increases the basic catalytic activity of X zeolite in the alkylation of toluene. This alkaline hydroxides neither affect the FAU framework nor the silicon/aluminium molar ratio of the X zeolite. The optimum (Na + K)/Al molar ratio of the improved catalyst was 1.06 corresponding to a washing volume of 200 mL. This X zeolite presented better catalytic activity than a cesium-zeolite prepared by ion-exchange. The presence of hydroxysodalite impurity in the X zeolite increased the amount of impregnated alkaline hydroxides but not the catalytic activity. The present study shows that it is possible to increase the basic properties of the X zeolite directly in the synthesis process. 相似文献