The HZSM-5 molecular sieve catalyst for toluene selective disproportionation to p-xylene was modified using polysiloxane as modifier and was characterized by means of X-ray diffraction(XRD), low-temperature nitrogen adsorption-desorption technique and nuclear magnetic resonance(27A1 MAS NMR). The effect of silica modification on the catalytic performance of the catalyst was investigated. The results showed that with the increase of deposited silica, the catalytic activity decreased while the selectivity of p-xylene increased, the molar ratio of benzene to xylene decreased after the first modification while increased after the second deposition. After modification, the micropore volume hardly changed, while the mesopore volume reduced. The external surface and the micropores were covered by silica after first modification and the second deposition mainly resulted in the decrease of the micropore size. The structure of HZSM-5 molecular sieve was kept but the content of non-framework aluminum increased. The amount of saturated adsorption of toluene reduced by 20% after the first modification while 84% of m-xylene.%采用夹套对造粒塔内的气粒两相流体进行冷却是一个既有多相流对流换热、单相流对流换热,又有固体导热不同流体之间相互作用的复杂过程.采用分区耦合的计算方法对该过程进行模拟,获得了造粒塔和夹套内详细的温度分布.考察了冷却水入口 温度、冷却水总量和3段夹套的冷却水比例对造粒塔内温度的影响.结果表明,冷却水入口温度显著影响造粒塔内的温度,冷却水总量影响次之,3段夹套的冷却水比例对造粒塔内温度的影响较小,且3种因素对提高传热系数均无显著影响:夹套合适的操作条件为冷却水总量2 667 kg/h,冷却水入口温度310K,3段夹套的冷却水比例为5∶3∶2.
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