SAPO-34的改性及其在合成气制低碳烯烃中的应用

Modification of SAPO-34 and its application in syngas conversion to light olefins

摘要:

对金属氧化物与分子筛组成的双功能催化剂中的分子筛进行改性，可进一步提高合成气制低碳烯烃（STO）反应性能。采用水热法合成不同金属Me（Ce、Zn、Zr）及不同Zr掺杂量改性的SAPO-34分子筛，并与GaZrOx金属氧化物物理混合制备GaZrOx/SAPO-34双功能催化剂，考察其催化STO反应性能。采用XRD、TEM、SEM-EDS、BET、FTIR、NH3-TPD、XPS对分子筛表征发现，不同金属改性的分子筛均合成了具有CHA结构的SAPO-34，掺杂Zr提高了分子筛的相对结晶度，减小了颗粒尺寸。Zr掺杂量为1.0%（n(ZrO2)与n(Al2O3)的物质的量比为1:100）时合成的1.0%ZrSP-34分子筛颗粒尺寸最小，平均粒径为0.53 μm，且强酸量适中（1.34 mmol/g）；掺杂2% Zr时导致多余的Zr以ZrO2形式存在于分子筛表面，覆盖了强酸中心。与未改性的SAPO-34相比，采用掺杂1.0% Zr合成的1.0%ZrSP-34制备GaZrOx/1.0%ZrSP-34双功能催化剂，可使CO转化率从14.2%增加到21.2%，低碳烯烃选择性从71.0%提高至82.4%，且该催化剂反应60 h后未出现明显失活。

关键词:合成气;低碳烯烃;分子筛改性;颗粒尺寸;酸性质

Abstract:

The catalytic performance of syngas to light olefins (STO) can be further enhanced by zeolite modification in bifunctional catalyst composed of metal oxide and zeolite. In this work, SAPO-34 zeolites were hydrothermally synthesized by modification of different metals Me (Ce, Zn, Zr) and various Zr doping contents, after physically mixed with GaZrOx metal oxide, the catalytic performance of prepared GaZrOx/SAPO-34 for STO was studied. XRD, TEM, SEM-EDS, BET, FT-IR, NH3-TPD and XPS were selected to characterize the zeolites. It is found that the synthesized SAPO-34 samples all possess CHA structure, the doping of Zr increased the relative crystallinity and reduced the particle sizes of the zeolites. When the doping content of Zr is 1.0% (n(ZrO2)：n(Al2O3) = 1 : 100), the synthesized 1.0%ZrSP-34 zeolite exhibits the smallest particle size, with an average particle size of 0.53 μm and a moderate amount of strong acid (1.34 mmol/g). The doping of 2% Zr results in the formation of ZrO2 on the surface of zeolite, covering the strong acid center. Compared with the unmodified SAPO-34 sample, the 1.0%ZrSP-34 prepared by doping of 1.0% Zr combined with GaZrOx enhanced the CO conversion from 14.2% to 21.2%, with the selectivity of light olefins improved from 71.0% to 82.4%, moreover, this catalyst shows almost no deactivation after a reaction time of 60 h.

Key words:syngas; light olefins; zeolite modification, particle size, acidity