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首页> 外文期刊>Chemistry: A European journal >Conversion of methane into C1 oxygenates by deep-UV photolysis on solid surfaces: Influence of the nature of the solid and optimization of photolysis conditions
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Conversion of methane into C1 oxygenates by deep-UV photolysis on solid surfaces: Influence of the nature of the solid and optimization of photolysis conditions

机译：通过在固体表面上进行深紫外线光解将甲烷转化为C1含氧化合物：固体性质的影响和光解条件的优化

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Deep-UV photolysis (either 165 or 185 nm) of surface hydroxy groups leads to homolytic O-H bond-cleavage with the generation of oxyl radicals that can initiate the room-temperature radical-chain methane activation. Whilst in the absence of oxygen, radical coupling reactions to give low-molecular-weight alkanes are observed in the gas phase, the presence of some oxygen quenches these radicals and increases the selectivity towards C1 oxygenates (methanol, formaldehyde, and formic acid species). The nature of the solid influences the efficiency of the photochemical process and the distribution between products in the gas and solid phases. Using Beta-, delaminated ITQ2 and ITQ6, and medium-pore ZSM5 zeolites, mesoporous MCM41 silicates, and non-porous TiO _2, we observed that confinement and porosity increased the proportion of C1 oxygenates adsorbed onto the solid and reduced the contribution of the gas-phase products. In addition, the presence of aluminum in the zeolite framework, which is responsible for the generation of acid sites, increased overoxidation of methanol and methoxy groups into formaldehyde and formic acids. For a given amount of methane and unchanged photolysis conditions, the conversion increased with the amount of the solid used as photocatalyst. In this way, methane conversions of up to 7 % were achieved for the 185 nm photolysis of methane for 1 h with a 76 MJ mol ~(-1) energy consumption.
机译：表面羟基的深紫外光解（165或185 nm）会导致均相O-H键断裂，并产生可引发室温自由基链甲烷活化的羟基自由基。在没有氧气的情况下，在气相中观察到自由基偶联反应生成低分子量的烷烃，某些氧气的存在会淬灭这些自由基并增加对C1氧化物的选择性（甲醇，甲醛和甲酸类） 。固体的性质影响光化学过程的效率以及气相和固相中产物之间的分布。使用Beta，分层的ITQ2和ITQ6以及中孔ZSM5沸石，中孔MCM41硅酸盐和无孔TiO _2，我们观察到限制和孔隙率增加了C1氧化物吸附到固体上的比例并减少了气体的贡献相产品。此外，沸石骨架中铝的存在导致酸位的产生，增加了甲醇和甲氧基过氧化为甲醛和甲酸的能力。对于给定的甲烷量和不变的光解条件，转化率随用作光催化剂的固体量的增加而增加。这样，对于185 nm的甲烷光解1 h，能量消耗为76 MJ mol〜（-1），可实现高达7％的甲烷转化率。

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