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以全硅分子筛silicalite-1为硅源,利用水热晶化法合成表面富钛的钛硅分子筛CTS,采用XRD、N2吸附-脱附、IR、XRF、UV—vis、XPS、DTA—TGA和SEM等对合成的分子筛进行表征。结果表明,合成的钛硅分子筛CTS具有MFI拓扑结构,钛物种主要集中在其表面,催化性能评价表明,在苯酚羟基化探针反应中合成的钛硅分子筛CTS具有较好的活性和苯二酚选择性,重复使用次数优于常规利用硅酯为硅源合成的分子筛TS-1。 相似文献
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以十六烷基三甲基溴化铵( CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,乙二胺为碱性介质,当n(TEOS)∶n( NaAl02)∶n(CTAB)∶n(H2NCH2CH2NH2)∶n(H2O)=1∶x∶0.12∶ 3.5∶130,其中x=0.1,0.033,0.02,0.01,0.006 7时,水热法合成了Al - MCM - 41介孔分子筛.通过XRD,N2吸附-脱附,NH3 - TPD和TEM等手段对不同硅铝比(n(Si)/n(Al))的Al - MCM -41介孔分子筛进行了表征.结果表明,当n(Si)/n( Al)由150减小至30时,Al - MCM -41介孔分子筛仍具有典型的六方介孔结构特征,但当n( Si)/n(Al)=10时,样品结构有序性下降.Al - MCM - 41介孔分子筛酸量随着n( Si)/n( Al)减小而增大.将Al - MCM - 41介孔分子筛用于催化合成氯乙酸正辛酯,相同反应条件下,n( Si) /n( Al) =30的Al - MCM - 41介孔分子筛为催化剂时酯化率最高,由此表明,Al - MCM - 41介孔分子筛作为催化剂,反应酯化率不仅取决于样品酸量,也与其晶体结构相关.当Al - MCM - 41介孔分子筛用量为氯乙酸质量的3%,反应温度为120~140℃,n(氯乙酸)∶n(正辛醇)=1∶1.2时,酯化率可达94.34%. 相似文献
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以六亚甲基亚胺为模板剂,乙醇为有机辅助剂,采用动态水热法合成了一系列MCM-22分子筛,利用X射线衍射(XRD)、氨程序升温脱附(NH3-TPD)、傅里叶变换红外光谱(FT-IR)和电子扫描显微镜(SEM)等表征手段考察了乙醇辅助剂对MCM-22分子筛的结构及酸性的影响.结果表明,添加适量的乙醇可以有效调控分子筛结构性能和结晶度,分子筛的强酸位的强度适度增强,弱酸位的强度减弱,总酸量和B酸中心数增大,而L酸中心数减少,且晶粒尺寸减小,比表面积增加,但过量的乙醇会导致ZSM-5分子筛的生成.以苯和丙烯烷基化合成异丙苯为模型反应,评价对所制备的分子筛催化性能,发现添加合适的乙醇得到的MCM-22分子筛具有更高的催化活性和选择性. 相似文献
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Hierarchical zeolite ZSM-5 synthesized by applying amphiphilic organosilane as mesopore template, nanosized zeolite Beta and zeolite MCM-22 have been studied, for the first time in the conversion of mixed ethylbenzene–m-xylene feed. The effects of the channel structure, nanosizing and presence of mesopores in these zeolite materials with close Si/Al molar ratio on the catalytic activity and selectivity have been discussed. It was found that the diverse zeolites have different advantages and disadvantages in dependence on their structure and morphology. MCM-22 zeolite provides promising ethylbenzene conversion at low xylene loss with high production of the p-isomer among xylene. 相似文献
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以六亚甲基亚胺为模板剂,在动态水热合成MCM-22分子筛的过程中,加入有机辅助剂聚乙二醇2000(PEG2000),考察有机辅助剂PEG2000对MCM-22分子筛结构、酸性以及催化性能的影响。由X射线衍射谱图可以看出,合成时加入适量的PEG2000,可以得到结晶较好的MCM-22晶体,但结晶度稍微有些降低。由氮吸附脱附测试结果可以看出,适量助剂PEG2000的加入,改变了分子筛的最可几孔径分布,最可几孔径由0.556 nm提高至0.587 nm,孔容由0.35 m3/g增加到0.59 m3/g,BET比表面积由410 m2/g增加到456 m2/g。NH3-TPD方法测试样品的酸性结果显示,加入适量的PEG2000后,分子筛的强酸位得到加强。另外用合成的分子筛作为催化剂,以苯与丙烯烷基化为模型反应,考察了MCM-22分子筛的活性以及选择性,结果显示催化剂的活性有较大提高,然而对异丙苯的初始选择性降低,随着反应的进行,异丙苯的选择性却很快地增长。 相似文献
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13X微孔沸石和MCM-41介孔材料的合成及用于处理含Cd2+废水 总被引:4,自引:0,他引:4
以天津蓟县钾长石矿粉为主要原料,经选矿、煅烧、水热处理等工艺成功合成了13X微孔沸石. 以气相氧化硅、氢氧化钠、十六烷基三甲基溴化铵等为主要原料,在水热条件下合成了MCM-41有序介孔材料. 采用XRD和N2吸附-脱附等手段对合成的13X沸石和MCM-41介孔材料的物相、比表面积、孔径、孔体积等进行了分析对比. 在此基础上,对13X沸石和MCM-41介孔材料处理含Cd2+废水的效果和机理进行了对比研究,确定了不同分子筛用量、不同初始pH值、不同混合时间下13X沸石和MCM-41介孔分子筛对水中Cd2+的吸附率和吸附量. 研究发现,尽管MCM-41的比表面积和孔径远大于13X沸石,但其对水中Cd2+的处理效果却低于13X沸石,这与13X沸石和MCM-41的孔道结构类型、化学组成、表面荷电性质等有关. 相似文献
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A series of acid–base bifunctional CaO/ITQ-2 zeolite catalysts were prepared by introducing calcium into the ITQ-2 zeolite. The catalysts were characterized by X-ray diffraction, FT-IR, NH3-TPD and CO2-TPD. The characterization results proved that ITQ-2 zeolite was synthesized by delaminating the MCM-22 zeolite. After modification by CaO, the catalysts could simultaneously have alkaline and acidic sites with little structural change. We then studied the catalytic capabilities of the prepared catalysts in the phosphorylation of dodecanol to di-dodecyl phosphate (DAP). The results show that ITQ-2 catalyst has higher selectivity for DAP than MCM-22. Versus ITQ-2 zeolite, the CaO/ITQ-2 catalysts have excellent acid–base cooperativity. The conversion of phosphoric acid and the selectivity of di-dodecyl phosphate could reach 80.2% and 77.5%, respectively over 3 wt.%CaO/ITQ-2 at optimal conditions. The catalytic activity of CaO/ITQ-2 catalyst could be regenerated by roasting after four times of reusing. 相似文献
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Simone Goergen Elie Fayad Sébastien Laforge Patrick Magnoux Loïc Rouleau Joël Patarin 《Journal of Porous Materials》2011,18(5):639-650
Layered MCM-22(P) was synthesized in the presence of hexamethonium (HM) cations. Compared to zeolite EU-1 (EUO-type structure),
which crystallizes in similar conditions, its formation is favored at high HM concentrations (HM/SiO2 ≥ 0.3) and in the absence of Na2O. HM-containing MCM-22(P) was used as starting material for zeolite formation. Upon hydrothermal treatment, HM-MCM-22(P)
transforms into zeolite EU-1 and upon calcination into a MWW-type zeolite. Transformation mechanisms were studied by standard
characterization techniques such as XRD, SEM and TEM. Catalytic properties of the MWW-type zeolite obtained from this precursor
were evaluated in a m-xylene isomerization reaction. Compared to zeolite MCM-22 prepared with hexamethyleneimine, a higher catalytic activity and
an increased isomerization selectivity were observed and discussed. 相似文献
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LI Qiang ZHANG Ying DOU Tao LI Yuping WANG Shan SUN Famin 《Frontiers of Chemical Science and Engineering》2007,1(1):1
Mesoporous aluminosilicate MCM-48 containing zeolite secondary building units in the pore wall has been synthesized in alkaline media with a two-step procedure. The aluminosilicate precursors comprising zeolite secondary building units were first synthesized by carefully controlling reaction conditions and then were assembled using cotemplates of gemini surfactant [C18H37N(CH3)2(CH2)3N(CH3)2C18H37]2+ (18-3-18) and triethanolamine (TEA). X-ray Diffraction (XRD) patterns of the as-made samples indicated that highly ordered mesostructured MCM-48 was formed. Transmission Electron Microscopy (TEM) images further verified the formation of MCM-48 with uniform cubic pore channel system having the pore opening diameter of about 25 Å. Compared with the conventionally synthesized MCM-48, the as-synthesized MCM-48 sample showed an adsorption band at 520 600 cm-1 in its FT-IR spectrum, which was assigned to five-membered ring vibration from zeolite structure. This suggested the presence of zeolite building units in the pore wall. N2 adsorption data showed that the material had a much higher specific surface area (1 200 m2/g) than the conventional MCM-48(1 100 m2/g). Finally, the catalytic performance of the as-made MCM-48 was evaluated by hydrogenation dealkylation reaction of heavy aromatic hydrocarbons. Catalytic results showed that the as-made MCM-48 catalyst exhibited higher conversion than the conventional MCM-48 catalyst. The as-made mesostructured MCM-48 may have a potential catalytic application in the conversion of bulky molecules. 相似文献
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Self-bonded bodies of zeolite MCM-22 were prepared by vapor-phase transport method. The resultant materials were characterized
by means of XRD, SEM, NH3-TPD, BET, 27Al MAS NMR, Pascal 140 and Pascal 240. It was found that the bodies, prepared by aluminosilicate gel, had been transformed
into zeolite MCM-22. The zeolite bodies that were composed of MCM-22 crystal chips avoided binder accession. The total acid
sites, the specific surface area, mechanical resistance and the average pore radius of the zeolite bodies reached 1.01 × 10−3 mol/g, 486.82 m2/g, 126 N/cm and 57.93 nm, respectively. 相似文献
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对各种条件下合成的MCM-22沸石进行了表征研究。研究表明晶化时间对MCM-22沸石的层间结构有着显著的影响,晶化40 h后,其结构趋向稳定。MCM-22沸石沸石具有较高的B酸含量,强酸中心主要为B酸,MCM-22晶体呈片状结构,其结构中存在丰富的大孔。以MCM-22沸石为催化剂考察了其催化乙烯和苯的液相烷基化的反应性能。结果表明,MCM-22沸石催化剂具有优良的选择性,在低苯烯比(B/E)的反应条件下,其反应稳定性优良。在乙烯质量空速达到0.7 h~(-1),苯烯摩尔比(B/E)可以降低到2.0,乙苯选择性达到84%,二甲苯含量小于50 mg/kg。 相似文献
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MCM-22、MCM-49和MCM-56三种分子筛的合成 总被引:2,自引:1,他引:1
MWW结构分子筛是一类新型的催化材料,具有独特的10元环孔道和12元环孔穴结构,在多种反应中表现出良好的催化活性。以六亚甲基亚胺作为模板剂,合成了MCM-22、MCM-49和MCM-56三种分子筛,并详细考察了不同硅源、凝胶配比、晶化温度和晶化时间对合成过程的影响。结果表明,凝胶配比和晶化温度对分子筛物相的影响较大。以硅胶粉为硅源,无论在何种晶化时间下都不能得到MCM-56,只能合成出MCM-49。而以碱性硅溶胶为硅源,在较短的晶化时间内就可以得到MCM-56。 相似文献