Abstract

Oxidative conversion of methane to acetic acid at 150°С and a pressure of 6.5 MPa with the assistance of carbon monoxide on rhodium-modified ZSM-5 zeolites with different SiO₂/Al₂O₃ molar ratios was studied. A decrease in SiO₂/Al₂O₃ from 300 to 30 leads to a 2.7-fold increase in the acetic acid yield. Such behavior of the catalytic system correlates with an increase in the acidity, primarily with an increase in the density of Brønsted acid sites on the zeolite surface. Introduction of 0.1–0.5 wt % rhodium into the zeolite increases the acetic acid yield by a factor of more than 3. The highest acetic acid yield (0.53 mmol/g_cat) is attained on the zeolite with SiO₂/Al₂O₃ = 33 modified with 0.5 wt % Rh. The methane transformation to acetic acid occurs while involving both the acid sites of the zeolite and the sites formed by reactive rhodium particles.

中文翻译：

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铑改性沸石上甲烷的直接低温氧化转化为乙酸

摘要

研究了在一氧化碳的作用下，在150°C和6.5 MPa的压力下，甲烷在不同SiO ₂ / Al ₂ O ₃摩尔比的铑改性ZSM-5分子筛上的氧化转化为乙酸的过程。SiO ₂ / Al ₂ O ₃从300降低至30导致乙酸产率提高2.7倍。催化体系的这种行为与酸度的增加有关，主要与沸石表面上布朗斯台德酸位点的密度增加有关。将0.1–0.5 wt％的铑引入沸石可将乙酸收率提高3倍以上。最高乙酸收率（0.53 mmol / g _Cat在用0.5wt％的Rh改性的SiO ₂ / Al ₂ O ₃＝ 33上的沸石上达到）。甲烷向乙酸的转化同时发生在沸石的酸性位点和反应性铑颗粒形成的位点上。