P改性ZSM-5纳米片催化裂解丁烯的研究

Study on catalytic cracking of butene over P-modified ZSM-5 nanosheet

制备了一系列低P负载量的P/ZSM-5纳米片分子筛,通过X射线衍射仪､低温N2吸附-脱附､NH_(3)-TPD､SEM等表征手段考察了P改性对纳米片分子筛晶型､孔结构､酸性质和形貌的影响,并将各催化剂用于催化正丁烯裂解反应。结果表明,由于P负载量较低,改性后的ZSM-5纳米片分子筛的比表面积､微孔孔容和形貌基本不变,而纳米片强酸位点的数量显著降低;P改性后可显著改善催化剂在正丁烯催化裂解中的稳定性和乙丙烯的选择性;与未改性的ZSM-5相比,当P负载量达0.45%时催化剂失活速率降低了1倍以上,且产物中乙烯､丙烯选择性可达58%左右。

A series of P/ZSM-5 molecular sieve nanosheets with low phosphorus loading are prepared via the impregnation method,and applied to catalyze the catalytic cracking of n-butene.The effects of phosphorus modification on the crystal form,pore structure,acidity and morphology of ZSM-5 nanosheets are investigated by means of X-ray diffraction,low-temperature N2 adsorption-desorption,NH_(3)-TPD,SEM and other characterization methods.The results show that due to a low loading of phosphorus,the specific surface area,micropore volume and morphology of ZSM-5 nanosheets remain basically unchanged after phosphorus modification while the number of strong acid sites on the nanosheets significantly decreases due to modification.The phosphorus modification can improve the stability of the catalyst in the catalytic cracking of n-butene and the selectivity of ethylene and propylene over the catalyst.The deactivation rate of the catalyst with a 0.45 wt.%of phosphorus loading is reduced by 50%more than that of the unmodified ZSM-5,and the selectivity of ethylene and propylene in the product can reach about 58%over the modified catalyst.