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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Reaction Mechanism for m-Xylene Oxidation in the Claus Process by Sulfur Dioxide
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Reaction Mechanism for m-Xylene Oxidation in the Claus Process by Sulfur Dioxide

机译：克劳斯过程中二氧化硫氧化间二甲苯的反应机理

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摘要

In the Claus process, the presence of aromatic contaminants such benzene, toluene, and xylenes (BTX), in the H2S feed stream has a detrimental effect on catalytic reactors, where BTX form soot particles and clog and deactivate the catalysts. Among BTX, xylenes are proven to be most damaging contaminant for catalysts. BTX oxidation in the Claus furnace, before they enter catalyst beds, provides a solution to this problem. A reaction kinetics study on m-xylene oxidation by SO2, an oxidant present in Claus furnace, is presented. The density functional theory is used to study the formation of m-xylene radicals (3-methylbenzyl, 2,6-dimethylphenyl, 2,4-dimethylphenyl, and 3,5-dimethylphenyl) through H-abstraction and their oxidation by SO2. The mechanism begins with SO2 addition on the radicals through an O-atom rather than the S-atom with the release of 180.0-183.1 kJ/mol of reaction energies. This exothermic reaction involves energy barriers in the range 3.9-5.2 kJ/mol for several m-xylene radicals. Thereafter, O-S bond scission takes place to release SO, and the O-atom remaining on aromatics leads to CO formation. Among four m-xylene radicals, the resonantly stabilized 3-methylbenzyl exhibited the lowest SO2 addition and SO elimination rates. The reaction rate constants are provided to facilitate Claus process simulations to find conditions suitable for BTX oxidation.
机译：在克劳斯方法中，H2S进料流中芳族污染物（如苯，甲苯和二甲苯（BTX））的存在对催化反应器产生不利影响，在催化反应器中，BTX会形成烟尘颗粒并使催化剂堵塞并使催化剂失活。在BTX中，二甲苯被证明是催化剂最具破坏性的污染物。在克劳斯熔炉中的BTX氧化进入催化剂床之前，可以解决该问题。提出了克劳斯炉中存在的氧化剂SO2对间二甲苯氧化的反应动力学研究。密度泛函理论用于研究通过H吸收形成的间二甲苯基（3-甲基苄基，2,6-二甲基苯基，2,4-二甲基苯基和3,5-二甲基苯基）及其被SO2氧化的方法。该机理始于通过O原子而不是S原子在自由基上添加SO2，并释放180.0-183.1 kJ / mol反应能量。对于几个间二甲苯基团，该放热反应涉及在3.9-5.2kJ / mol范围内的能垒。此后，发生O-S键断裂以释放SO，并且残留在芳族化合物上的O原子导致CO的形成。在四个间二甲苯自由基中，共振稳定的3-甲基苄基化合物显示最低的SO2添加和SO消除速率。提供反应速率常数以促进克劳斯过程模拟，以找到适合BTX氧化的条件。

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