Investigation of methanol conversion over high-Si beta zeolites and the reaction mechanism of their high propene selectivity,Catalysis Science & Technology

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Investigation of methanol conversion over high-Si beta zeolites and the reaction mechanism of their high propene selectivity
Catalysis Science & Technology ( IF 4.4 ) Pub Date : 2017-11-09 00:00:00 , DOI: 10.1039/c7cy01804e
Xuebin Zhao _{1,

2,

3,

4,

5} , Linying Wang _{1,

2,

3,

4,

5} , Jinzhe Li _{1,

2,

3,

4,

5} , Shutao Xu _{1,

2,

3,

4,

5} , Wenna Zhang _{1,

2,

3,

4,

5} , Yingxu Wei _{1,

2,

3,

4,

5} , Xinwen Guo _{6,

7,

8,

9,

10} , Peng Tian _{1,

2,

3,

4,

5} , Zhongmin Liu _{1,

2,

3,

4,

5}

Affiliation

Large pore high-Si beta zeolites (Si/Al = 136 to 340) were synthesized by a HF-assisted method, and their catalytic performance for the conversion of methanol to propene was explored. It is demonstrated that beta zeolites with low acid density facilitate the achievement of high propene selectivity and a high propene/ethene ratio. The HF dosage in the synthesis has great influence on the Al distribution in the framework, as evidenced by ²⁷Al MAS NMR and ²⁷Al MQ MAS NMR spectroscopy, which may influence the acidity and microstructure of acid sites and lead to a remarkable catalytic lifespan. A HF/SiO₂ ratio of 0.45 is found to facilitate the synthesis of high-Si beta enriched with Al atoms located at the T9 sites; this helps the catalyst show the longest lifetime, with a propene selectivity of 49.7–58.3% at 550 °C and WHSV = 2 h⁻¹. With the aid of ¹²C/¹³C-methanol switch experiments, we elucidated that the olefin-based mechanism dominates the reaction and contributes to the formation of ethene, propene, and higher olefins. Moreover, two phenol compounds are identified in the coke species, which have not been observed previously and have been found to be detrimental to the reaction.

中文翻译：

高Siβ沸石上甲醇的转化及其高丙烯选择性反应机理的研究

利用HF辅助法合成了大孔高Siβ沸石（Si / Al = 136〜340），并探讨了其催化甲醇转化为丙烯的催化性能。已经证明，具有低酸密度的β沸石有助于实现高丙烯选择性和高丙烯/乙烯比。合成中的HF剂量对骨架中Al的分布有很大的影响，如²⁷ Al MAS NMR和²⁷ Al MQ MAS NMR光谱所证明的那样，这可能会影响酸位的酸度和微观结构，并导致显着的催化寿命。HF / SiO ₂发现0.45的比率有利于合成富含T9位点的Al原子的高Siβ；这有助于催化剂显示最长的寿命，在550°C和WHSV = 2 h ^-1时丙烯选择性为49.7-58.3％。借助¹² C / ¹³ C-甲醇转换实验，我们阐明了基于烯烃的机理主导了反应，并有助于形成乙烯，丙烯和高级烯烃。此外，在焦炭种类中鉴定出两种酚化合物，这是以前没有观察到的，并且发现对反应有害。

更新日期：2017-11-22

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