t-ZrO_2/SAPO-34质量比对t-ZrO_2/SAPO-34复合催化剂物化性质及其甲醇制烯烃催化性能的影响

Effects of t-ZrO_2/SAPO-34 Mass Ratio on the Physicochemical Properties and Catalytic Performance of t-ZrO_2/SAPO-34 Composite Materials in Methanol-to-Olefin Reaction

采用介孔t-ZrO_2对微孔SAPO-34分子筛进行复合改性,利用水热包覆技术制备了t-ZrO_2/SAPO-34复合催化剂,研究了t-ZrO_2/SAPO-34质量比(m(t-ZrO_2)/m(SAPO-34))对复合催化剂物化性质和甲醇制烯烃(MTO)催化性能的影响。采用X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电子显微镜(SEM)、程序升温脱附(NH_3-TPD)和N_2吸附-脱附(BET)等手段对不同复合催化剂的晶相组成、骨架结构、微观形貌、表面酸性及孔结构进行分析表征。结果表明,m(t-ZrO_2)/m(SAPO-34)对t-ZrO_2/SAPO-34复合催化剂的物化性质和催化性能影响较大。过高或过低m(t-ZrO_2)/m(SAPO-34)制得的复合催化剂中SAPO-34分子筛结晶度和骨架结构特征均有所减弱,分别呈现以介孔为主和以微孔为主的孔结构特征;当m(t-ZrO_2)/m(SAPO-34)为1/1时,制得的复合催化剂形成了包覆相结构和微-介孔层级结构(微孔比表面积113 m^2/g,介孔比表面积176 m^2/g,总比表面积289 m^2/g,总孔体积0.19cm^3/g),总酸量较大(0.344mmol/g);在常压、反应温度380℃、N_2流速20mL/min、进料空速2h^(-)的MTO反应条件下,复合催化剂表现出优越的催化性能、稳定性及反应寿命,甲醇转化率和低碳烯烃选择性分别达到100%和90.54%,催化寿命达到1130min,与单一SAPO-34分子筛相比,催化寿命延长了768min。

Microporous SAPO-34 molecular sieves were promoted by using mesoporous t-ZxO2 to prepare t-ZrO2/SAPO-34 composite catalysts.The effects of mass ratio of t-ZrO2 to SAPO-34 on the physicochemical properties and catalytic performance of the composite catalyst fabricated via hydrothermal coating route in methanol-to-olefin(MTO)process were investigated.These catalysts were extensively characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),temperature programmed desorption(NH3-TPD)and N2 adsorption-desorption(BET)techniques,to investigate their crystalline phase,skeletal structure,morphology,surface acidity and pore structure,respectively.Results indicate that various mass ratios of t-ZrO2 to SAPO-34 significantly impact on the physicochemical properties and catalytic performance of t-ZrO2/SAPO-34 composite catalyst in MTO process.The crystallinity and skeleton characteristics of SAPO-34 molecular sieve in composite catalyst are significantly weakened when the mass ratio of t-ZrO2 to SAPO-34 becomes higher or lower.As the mass ratio of 1/1,the uniformly continuous coating phase and hierarchical structure(microporous specific surface area of 113 m^2/g,mesoporous specific surface area of 176 m^2/g,total specific surface area of 289 m^2/g,the total pore volume of 0.19 cm^3/g)with total amount of acid of 0.344 mmol/g are successfully obtained in the composite catalyst,which exhibits excellent catalytic performances,stability and reaction life with methanol conversion of 100%,light olefins selectivity of 90.54%,and catalytic lifetime of 1130 min under the conditions of atmospheric pressure,reaction temperature of 380℃,nitrogen flow rate of 20 mL/min and feed speed of 2 h^-1.Compared with the single SAPO-34 molecular sieve,the catalytic lifetime of the t-Zr02/SAPO-34 composite catalyst is extended by 768 min.