甲烷液相部分氧化合成甲醇过程研究

Study of Catalysis Oxidation of Methane to Methanol in Liquid Phase

以碘系列化合物为催化剂,在发烟硫酸溶剂中进行了甲烷液相选择性氧化制取甲醇。考察了催化剂种类、用量、反应温度、发烟硫酸浓度等工艺条件对反应收率的影响,探讨了甲烷液相选择性氧化的催化机理以及发烟硫酸中 SO3 含量的作用。实验结果表明,甲烷液相部分氧化的最佳催化剂为 I2,最佳的工艺条件为催化剂浓度为0.099 mol?L?1、反应温度 473K、发烟硫酸(SO350%(wt))、反应时间 3h。 在此条件下,甲烷转化的转化率可达 82.65%,选择性可达 70.43%。机理研究表明,甲烷在部分氧化反应中首先转化为硫酸单甲酯,然后进一步水解得到甲醇, 反应遵循亲电取代机理。发烟硫酸中的游离 SO3的作用就在于提供较好的亲电环境、反应的氧源以及亲核试剂。

The selective oxidation of methane in oleum was catalyzed by the iodine compounds. The effect of the catalysts kinds, catalyst concentration, reaction temperature and the amount of SO3 in oleum on the conversion of methane and the yield of methanol were investigated. The mechanism of reaction in oluent was studied and the functions of oluent were also discussed. Among the tested catalysts, I2 showed the highest activity and selectivity. Under the optimal reaction condition, that is, the concentration of I2 is 0.099 mol&middotL-1, reaction temperature is 473 K, pressure of methane is 3.4 MPa, reaction time is for 3 h, the content of sulfur trioxide in oleum is about 50%, the 82.65% conversion of methane and the 70.43% yield of methanol could be obtained. The mechanism analysis shows that methane is transformed into methyl bisulfate firstly, then the methyl bisulfate is hydrolyzed into methanol. The oxidation of methane follows the mechanism of electrophilic displacement intermediate. The SO3 of oluent is the key element in the oxidation of methane and the functions of strong acid are supplying the electrophilic surrounding, being the source of oxidant and the nucleophile to product a stable intermediate.