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首页> 外文期刊>Catalysis science & technology >Boosting the turnover number of core-shell Al-ZSM-5@B-ZSM-5 zeolite for methanol to propylene reaction by modulating its gradient acid site distribution and low consumption diffusion
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Boosting the turnover number of core-shell Al-ZSM-5@B-ZSM-5 zeolite for methanol to propylene reaction by modulating its gradient acid site distribution and low consumption diffusion

机译：提高核壳的转化率Al-ZSM-5@B-ZSM-5沸石为甲醇丙烯反应通过调节其梯度酸站点分布和低消费扩散

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摘要

Herein, a specific core-shell MFI zeolite was designed for the methanol to propylene (MTP) reaction. The core-shell structure of Al-ZSM-5@B-ZSM-5 and Al-ZSM-5@silicalite-1 were easily obtained via a two-step procedure, in which Al-ZSM-5 aggregate acted as the core and B-ZSM-5 or silicalite-1 as the shell. Their core-shell structures, acidity distribution and pore properties were characterized systemically, and new insights were gained into the synergetic effect of acid property and diffusion on the MTP reaction. The Al-ZSM-5@B-ZSM-5 zeolite exhibited a superior catalytic performance with a lifetime of 350 h (WHSV = 3 h(-1)), propylene selectivity of 49% and high turnover number of 4.3 x 10(6), while for the Al-ZSM-5 core, the corresponding values were 210 h, 43% and 5.2 x 10(5), respectively. Al-ZSM-5@silicalite-1 displayed the second best performance with the values of 250 h, 45% and 2.9 x 10(6), respectively. Gradient strong acid reduction from the core to the shell via the epitaxial growth of the silicalite-1 or B-ZSM-5 shell combined with an appropriate strong/weak acid ratio plays a vital role in inhibiting the hydrogen transfer reaction and thus gives a low consumption of propylene and low coke deposition. For the hydrogen transfer reaction of alkenes to form alkanes and aromatics, strong acid sites are required. Moreover, the acid sites originally existing on the external surface of the Al-ZSM-5 core were converted into internal acid sites due to the formation of an interface zone in the core-shell zeolite, possessing micropore characteristics, which in turn improve the shape selectivity and suppress coke deposition. Especially, the Al-ZSM-5@B-ZSM-5 zeolite displayed more weak acid sites and few strong acid sites on its shell surface, which are beneficial for the low formation of external coke and also account for the highest utilization of acid sites in the MTP reaction, high propylene selectivity and long lifetime.
机译：在此,一个特定的核壳MFI沸石为甲醇丙烯(MTP)的反应。通过一个两步的过程,容易获得Al-ZSM-5总作为核心和哪一个B-ZSM-5或silicalite-1壳。核壳结构、分布和酸度孔隙性能特征系统,和新见解获得协同作用的MTP酸性质和扩散的影响的反应。一个优越的催化性能350 h (WHSV = 3 h(1)),丙烯选择性49%和高转化率的4.3 x 10 (6),而对于Al-ZSM-5核心,相应的值是210 h, 43%和5.2 x 10 (5),分别。第二个和250 h值的最佳性能,分别为45%和2.9 x 10(6)。强酸减少从核心到壳silicalite-1或通过外延生长B-ZSM-5壳加上一个合适的强/弱酸性比率起着至关重要的作用抑制氢转移反应从而给出了丙烯和低的低消费可口可乐沉积。形成烷烃和烯烃的反应芳烃、强酸网站是必需的。此外,酸最初现有网站的外部表面Al-ZSM-5核心转化为内部由于酸网站在核壳形成一个界面区沸石,具有微孔特征,进而提高选择性和形状抑制焦炭沉积。Al-ZSM-5@B-ZSM-5沸石呈现出更多的弱酸网站和一些强酸网站在其外壳低的表面,这是有益的形成的外部可口可乐也占了MTP酸利用率最高的网站反应,丙烯选择性高、长一生。

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