排序方式: 共有70条查询结果,搜索用时 31 毫秒
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HZSM-5分子筛焙烧脱铝的27Al MQMAS NMR研究 总被引:1,自引:0,他引:1
用29Si、27Al魔角旋转固体核磁共振(MAS NMR)结合二维多量子魔角旋转(2D MQMAS)技术对焙烧脱铝的HZSM-5分子筛中铝的配位状态进行了研究.结果表明,HZSM-5分子筛经焙烧后,在化学位移(δ)45处出现一宽峰信号,其主要来自扭曲四配位铝.通过二维三量子铝谱计算出扭曲四配位铝的四极作用常数约为5.2 MHz.对700和750 ℃焙烧样品的铝谱进行分峰拟合,发现在δ 30处又出现一个小峰,归属为非骨架五配位铝.同时,在750 ℃焙烧样品的二维多量子铝谱中直接观察到非骨架五配位铝的信号.焙烧温度低于700 ℃,脱铝不明显;高于700 ℃,引起分子筛骨架的显著脱铝.焙烧还造成部分骨架铝的信号变得“不可观测”. 相似文献
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HZSM‐5‐supported Brönsted and Lewis acidic ionic solid 1,3‐disulfoimidazolium chlorozincate materials ([dsim]2[ZnCl4]@HZSM‐5) were synthesized with various ratios (3, 6, 9, 17 and 50% w/w). The heterogeneous materials were characterized via a variety of spectroscopic techniques. Dual acidity of these materials was determined using specified techniques. These acidic solids were examined as stable heterogeneous catalysts for the Fischer indole reaction of equimolar amounts of phenylhydrazine hydrochloride and various aliphatic or aromatic ketones at 80–90°C in neat condition to produce substituted indole derivatives. The efficient 17% ionic salt‐loaded HZSM‐5 composite was easily reused for ten consecutive cycles with a slight loss of its activity. The recycled catalyst was further analysed using powder X‐ray diffraction and inductively coupled plasma optical emission spectrometric techniques. 相似文献
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水热处理对纳米HZSM-5沸石酸性质及其降低汽油烯烃性能的影响 总被引:13,自引:0,他引:13
采用水蒸气和碱性氨水蒸气在500℃下对纳米HZSM-5沸石催化剂进行了水热处理改性,并用XRD,IR,NH3-TPD和XRF对催化剂进行了表征.以降低FCC汽油(≤70℃馏分)烯烃含量为探针反应,考察了不同水热处理介质对催化剂酸性质和催化性能的影响.结果表明,经不同介质水热处理后,纳米HZSM-5沸石中约10%的Al2O3被脱除,总酸量降低,导致积炭失活的强酸中心明显减少;不同水热处理介质对催化剂的总酸量没有明显影响,而对酸中心类型分布的影响较大.水热处理改性使催化剂活性的稳定性明显改善,初始活性降低.同时,水热处理改性降低了催化剂对芳构化反应的催化活性,提高了对异构化反应的催化活性.采用氨水(0.5mol/L)蒸气处理的纳米HZSM-5催化剂其降烯烃催化活性更为稳定.在给定的反应条件下,FCC汽油的烯烃含量(φ)由65.9%降低到约26%,产物中烯烃、芳烃(主要是C7~C9芳烃)和烷烃含量分别保持在25%,19%和55%左右,辛烷值基本不变. 相似文献
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高温下,甲烷在Mo/HZSM-5分子筛上可直接生成苯[1].虽然低温下甲烷能被Mo/HZSM-5催化剂表面的—OH所活化[2],但对甲烷在高温下的活化过程知之甚少,然而这却是很重要的.我们采用原位红外光谱技术,研究了甲烷在高温下Mo/HZSM-5催化... 相似文献
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A. Marcilla M. I. Beltrán R. Navarro 《Journal of Thermal Analysis and Calorimetry》2007,87(2):325-330
The effect of regeneration conditions on
the composition of the gases evolved during the catalytic pyrolysis of low
density (LDPE) and high density polyethylene (HDPE) with HUSY and HZSM5 catalysts
has been analysed by the TG/FTIR technique. When regenerated HUSY was employed,
the evolution of the gases obtained was similar to that with fresh HUSY, indicating
that the regeneration treatment did not affect its properties. Nevertheless
with HZSM5, as the regeneration temperature was higher, the composition of
the gases gradually became more similar to that evolved in the thermal process. 相似文献
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Mohammad Shakirullah Imtiaz Ahmad Habibur Rahman M. Arsala Khan M. Ishaq Amjad Ali Shah 《中国化学会会志》2006,53(5):1059-1066
This paper demonstrates the spectral analysis of some distillates obtained from asphalt cracking in the presence of a conventional expensive catalyst, i.e., HZSM‐5, and local cheap and readily available clay, i.e., UTIMAC. Each distillate was fractionated into pentane soluble (PI) and pentane insoluble (PI) fractions based on solubility in n, pentane. Both PS and PI obtained in the case of HZSM‐5 and UTIMAC were analyzed by 1H‐NMR spectrophotometry using CDCl3 as dissolving solvent and tetramethylsilane (TMS) as internal standard. It is evident from the profiles that both catalysts caused the generation of some peaks ascribed to methylene and methene configurations in the aliphatic region. Bands corresponding to aromatic configurations were also generated. The results indicate that the cheap local catalyst used has comparable suitability with the conventional expensive catalyst in terms of asphalt cracking. 相似文献
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Mo/HZSM-5分子筛的表征和液相催化酯化活性 总被引:6,自引:0,他引:6
用XRD,IR,NH3TPD和BET等技术研究了Mo/HZSM5分子筛上Mo的体相状态和酸性;在液相酯化反应中,利用Mo/HZSM5分子筛催化合成了丙酸异戊酯和乳酸异戊酯.结果表明,Mo在Mo/HZSM5分子筛上主要以三氧化钼微晶存在,且随Mo担载量的增加,分子筛的总酸量降低,L酸中心增多,对液相催化酯化反应有较高的活性. 相似文献
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