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Catalytic Longevity of Hierarchical SAPO-34/AlMCM-41 Nanocomposite Molecular Sieve In Methanol-to-Olefins Process
Combinatorial Chemistry & High Throughput Screening ( IF 1.8 ) Pub Date : 2021-05-01 , DOI: 10.2174/1386207323666200428092404
Hossein Roohollahi 1 , Rouein Halladj 1 , Sima Askari 2
Affiliation  

Introduction: SAPO-34/AlMCM-41, as a hierarchical nanocomposite molecular sieve was prepared by sequential hydrothermal and dry-gel methods studied for catalytic conversion of methanol to light olefins. Pure AlMCM-41, SAPO-34, and their physical mixture were also produced and catalytically compared. Physicochemical properties of materials were mainly investigated using XRD, N2 isothermal adsorption-desorption, FESEM, FT-IR, NH3-TPD, and TG/DTG/DTA techniques.

Methods: Micro-meso hierarchy of prepared composite was demonstrated by XRD and BET analyses. Catalytic performance of materials illustrated that the methanol conversion of the prepared composite was about 98% for 120 min, showing a higher activity than the other catalysts. The initial reaction selectivity to light olefins of the composite was also comparable with those for the other catalysts. Furthermore, the results revealed that SAPO-34/AlMCM-41 preparation decreased the concentration and strength of active acid sites of the catalyst which could beneficially affect the deposition of heavy molecular products on the catalyst. However, as observed, the prepared composite was deactivated in olefins production faster than pure SAPO-34.

Results: The small mean pore diameter of composite could be mainly responsible for its pore blockage and higher deactivation rate. Meanwhile, since the SAPO-34 prepared by dry-gel method had inherently high mesoporosity, the AlMCM-41 introduction did not promote the molecular diffusion in the composite structure.

Conclusion: The coke content was found 15.5% for deactivated composite smaller than that for the SAPO- 34 catalyst which could be due to the pore blockage and deactivation of the composite in a shorter period.



中文翻译:

多级 SAPO-34/AlMCM-41 纳米复合分子筛在甲醇制烯烃过程中的催化寿命

简介:SAPO-34/AlMCM-41 作为一种分层纳米复合分子筛,通过连续水热和干凝胶方法制备,用于甲醇催化转化为轻烯烃。还生产了纯 AlMCM-41、SAPO-34 和它们的物理混合物并进行了催化比较。材料的理化性质主要采用XRD、N2等温吸附-解吸、FESEM、FT-IR、NH3-TPD和TG/DTG/DTA技术进行研究。

方法:通过 XRD 和 BET 分析证明了制备的复合材料的微细层次结构。材料的催化性能表明,制备的复合材料在 120 分钟内甲醇转化率约为 98%,显示出比其他催化剂更高的活性。复合材料对轻质烯烃的初始反应选择性也与其他催化剂的反应选择性相当。此外,结果表明,SAPO-34/AlMCM-41 的制备降低了催化剂活性酸位的浓度和强度,这可能有益于重分子产物在催化剂上的沉积。然而,正如所观察到的,所制备的复合材料在烯烃生产中的失活速度比纯 SAPO-34 快。

结果:复合材料的平均孔径较小可能是其孔隙堵塞和失活率较高的主要原因。同时,由于干凝胶法制备的 SAPO-34 具有固有的高介孔率,AlMCM-41 的引入并没有促进复合结构中的分子扩散。

结论:发现失活复合材料的焦炭含量比 SAPO-34 催化剂小 15.5%,这可能是由于复合材料在较短的时间内发生孔堵塞和失活。

更新日期:2021-03-31
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