【作者】 张玲玲；

【导师】 李凤艳； 孙桂大；

【作者基本信息】 北京化工大学 ， 化学工艺， 2007， 硕士

【摘要】 本论文采用水热法制备了一系列MCM-41和硅铝复合分子筛催化剂，采用XRD、BET、IR、SEM、TEM、TG-DTA和NH3-TPD等现代分析手段对其进行了表征，以三异丙基苯为反应物对催化剂进行催化裂化性能评价。1、在本实验室条件下，水热法合成MCM-41分子筛的最佳条件为nSiO₂／nAl₂O₃=70、nCTAB／nSiO₂=0.12，pH=9、晶化温度120℃，晶化时间56h；水热法合成硅铝复合分子筛的最佳条件为nSiO₂／nAl₂O₃=90、nCTAB／nAl₂O₃=22、nTEAOH／nAl₂O₃=30、nH₂O／nAl₂O₃=1400、晶化温度120℃，晶化时间12～84h。2、N₂吸附-脱附结果显示，MCM-41分子筛具有2.8nm的均一孔径。合成的硅铝复合分子筛同时具有微孔和介孔结构，而且硅铝复合分子筛的表面积最大达到了1120m²／g，优于MCM-41分子筛的782m²／g。3、SEM照片显示MCM-41分子筛晶体呈团聚状地生长在一起，晶粒大小比较均匀，每个球状晶粒的尺寸约10μm左右。硅铝复合分子筛晶体呈团聚状地生长在一起，复合分子筛晶粒聚集，有的在大颗粒上附晶生长了小颗粒，有的晶粒聚合，晶界不再明显。4、TEM照片显示MCM-41分子筛的孔道剖面呈指纹状，孔径尺寸约2nm以上，与N₂吸附-脱附测得的2.8nm左右的孔径尺寸一致。硅铝复合分子筛表面分布着较密集的孔道，而且孔道尺寸不均一，这验证了此种硅铝复合分子筛是微孔-介孔复合的结构。5、吡啶红外光谱显示，硅铝复合分子筛与ZSM-5分子筛相比，B酸和L酸中心数量要少，强度也要低。NH₃-TPD测试结果表明硅铝复合分子筛存在弱酸和中强酸中心。随着nSiO₂／nAl₂O₃的增加，硅铝复合分子筛的酸量呈现逐渐减少的趋势。6、TG-DTA测试表明，MCM-41分子筛的骨架在780℃发生坍塌，硅铝复合分子筛的骨架坍塌发生在900℃，说明硅铝复合分子筛具有更好的热稳定性。7、HMCM-41分子筛催化裂化三异丙基苯的反应转化率可达56.1％。随着nSiO₂／nAl₂O₃的增加，转化率呈下降趋势。产物苯、间二异丙苯和对二异丙苯的选择性也随着nSiO₂／nAl₂O₃的增加而降低。硅铝复合分子筛的nSiO₂／nAl₂O₃在30～150之间变化时，三异丙基苯几乎全部发生了反应。随着nSiO₂／nAl₂O₃的增加，苯和异丙苯的选择性逐渐降低，而间二异丙苯和对二异丙苯的选择性逐渐增加。8、具有相同nSiO₂／nAl₂O₃的HZSM-5、HMCM-41、硅铝复合分子筛和机械混合分子筛，其催化裂化三异丙基苯的活性对比表明，硅铝复合分子筛的转化率最高，原料几乎全部发生裂解，且异丙苯、间二异丙苯和对二异丙苯的选择性也较高。HMCM-41的初活性为34.6％，其反应产物里有苯、对二异丙苯和间二异丙苯，选择性都不高。HZSM-5分子筛催化裂化三异丙基苯的转化率最低，仅15.9％，产物中仅有间二异丙苯。机械混合分子筛ZM1比ZM2的活性高，这可能与ZM1中ZSM-5分子筛的含量少有关。硅铝复合分子筛与机械混合分子筛的催化裂化转化率相差悬殊的结果，证明了硅铝复合分子筛的确是一种微孔-介孔复合的产物，它完全不同于HMCM-41和机械混合物，它的催化裂化性能优越于微孔分子筛、介孔分子筛和机械混合分子筛。更多还原

【Abstract】 A series of MCM-41 and Si-Al composited zeolites were synthesized byhydrothermal method and characterized by XRD, BET, IR, SEM, TEM,TG-DTA and NH₃-TPD techniques. The catalytic cracking of 1,3,5-triiso-propylbenzene were carried out over the zeolites.（1） The best synthesis conditions of MCM-41 zeolites synthesized byhydrothermal method in laboratory were nSiO₂/nAl₂O₃=70, nCTAB/nSiO₂=0．12, pH=9, crystal temperature 120℃and crystal time 56h; The bestsynthesis conditions of Si-Al composited zeolites by hydrothermal method inlaboratory were nSiO₂/nAlO₃=90, nCTAB/nAl₂O₃=22, nTEAOH/nAl₂O₃=30,nH₂O/nAl₂O₃=1400, crystal temperature 120℃and crystal time 12～84h。（2） The result of N₂ adsorption-desorption showed that MCM-41 zeolitehad symmetrical aperture of 2．8nm and Si-Al composited zeolite had bothmicropore and mesopore structure. The surface area of Si-Al compositedzeolite reached 1120m²/g, larger than 782 m²/g of MCM-41 zeolite.（3） The SEM photos showed that crystalloid of MCM-41 zeolites grew all round, the grain of crystalloid was homogeneous and the dimension of themwas nearly 10μm. The crystalloid grain of Si-Al composited zeolite assembled,small grain grew over big grain, and the aggregation of some grain made thecircumscription blurry.（4） The TEM photos showed that the aperture section of MCM-41 zeolitelike dactylogram and aperture was bigger than 2nm, which was similar to2．8nm of N₂ adsorption-desorption result. The Si-Al composited zeolite haddense aperture and inhomogeneous dimension, which validated that the Si-Alcomposited zeolite was really micro-mesopore structure.（5） Pyridine adsorbed IR showed that, the Si-Al composited zeolite hadless B and L acidic sites and weaker acidity than ZSM-5 zeolite. The result ofNH₃-TPD indicated the acidic amount of Si-Al composited zeolite decreasedgradually with the increase of nSiO₂/nAl₂O₃．（6） The TG-DTA result demonstrated that the framework of MCM-41zeolite collapsed at 780℃, while that of Si-Al composited zeolite collapsed at900℃, so the Si-Al composited zeolite had better heat stability.（7） Initial catalytic convertion of the HMCM-41 zeolite for the crackingof 1,3,5-triisopropylbenzene was 56．1%, and the convertion declined with theincrease of nSiO₂/nAl₂O₃．The selectivity of benzene, m-diisopropylbenzeneand p-diisopropylbenzene decreased with the increase of nSiO₂/nAl₂O₃．The1,3,5-triisopropylbenzene had been converted almost completely over the Si-Al composited zeolite with nSiO₂/nAl₂O₃ of 30～150．The selectivity ofbenzene and isopropylbenzene decreased and the selectivity ofm-diisopropylbenzene and p-diisopropylbenzene increased gradually with theincrease of nSiO₂/nAl₂O₃．（8） Initial catalytic activities for the cracking of 1,3,5-triisopropylbenzeneover HZSM-5, HMCM-41, Si-Al composited zeolites and mechanical mixedzeolites with same nSiO₂/nAl₂O₃ indicated that the Si-Al composited zeolitepossessed the highest activity, and almost all 1,3,5-triisopropylbenzene hadbeen converted absolutely, and the selectivity of all production were reallyhigh, which prove the Si-Al composited zeolite has pure mico-mesoporestructure, and it was different from HMCM-41 and mechanical mixed zeolites,its catalytic cracking performance was superior to micopore zeolites,mesopore zeolites and mechanical mixed zeolites. The initial convertion ofHMCM-41 was 34．6%, the selectivity of production benzene, m-diisopropyl-benzene and p-diisopropylbenzene were not high. HZSM-5 had the lowestconvertion 15．9%, and the production only had m-diisopropylbenzene. Themechanical mixed zeolites ZM1 showed higher convertion than ZM2 becausethe content of ZSM-5 in ZM1 was lower than that in ZM2．更多还原