庚烯与H2S在酸性催化剂上反应机理研究I-硫醇等生成机理

 为了研究催化裂化汽油中硫化物的生成机理,在小型固定流化床(FFB)装置中考察了不同质量分数的庚烯与H₂S在固体酸催化剂上的反应.结果表明, 庚烯与H₂S的反应主要生成噻吩类硫化物、部分硫醇、少量硫醚和痕量四氢噻吩等硫化物；庚烯质量分数越高,生成硫化物的量越多; 噻吩类硫化物中生成量最大的甲基苯并噻吩的生成量也随着庚烯质量分数增加而线性增长.烯烃在催化剂B酸活性中心上吸附形成正碳离子, 正碳离子与H₂S结合生成硫醇,硫醇的生成遵循正碳离子机理.硫醇与烯烃反应生成硫醚.当反应温度为400～500℃,庚烯与H₂S反应中,生成硫醇、硫醚的反应均为放热反应,硫醇的平衡收率较低,硫醚的平衡收率更低一些.

STUDY ON REACTION MECHANISM OF HEPTENE AND H2S ON ACID CATALYSTS I: MECHANISM OF THIOLS ETC FORMATION

In order to accounting for the formation of sulfur impurity in fluid catalytic cracking (FCC) gasoline, the reaction of differernt content of heptene with H2S was investigated by solid acid catalysis on a small fixed fluid bed (FFB) units .The results showed that heptene react ing with H2S mainly transfomed into gasoline sulfur compounds including thiophenes, fractional thiols, minor sulfides or trace tetrahydrothiophenes, with higher content of heptene, more amount of sulfur resultants. Methyl benzothiophene(M-BT), the most amount of sulfur resultants,was produced by thiophenes and olefins who conduct alkylation , following protonation,cyclisation and dehydrogenation on the surface of acid catalysts. The amount of M-BT resultants increases in the proportion to the content of the content of heptene. The formation of thiols conducts through H2S binding to carbonnium ions obtained by the adsorption of olefins on the B acid site of catalysts, followed by a acid-catalyzed protolytic mechanism, which is exothermic reaction with low equilibrium conversion during the temperature of 400℃~500℃.Minor sulfids derives from the addition of thiols with olefins, which is exothermic reaction with lower equilibrium conversion during the temperature of 400℃~500℃.