摘要
为了研究催化裂化汽油中噻吩类含硫化合物的生成机理，分别在小型固定流化床（FFB）装置和小型流化床装置（ACE）中考察了庚烯与H2S、己硫醇在固体酸催化剂上的反应。结果表明，在固体酸催化剂上己硫醇主要分解为H2S与烯烃，转化为噻吩类含硫化合物的概率很小。因此，在庚烯与H2S反应中，噻吩及烷基噻吩的生成不是以饱和硫醇为过渡态，而是以不饱和硫醇为过渡态。烯烃在催化剂的L酸中心作用下失去负氢离子生成烯基正碳离子，烯基正碳离子与H2S结合生成不饱和硫醇，不饱和硫醇接着进行负氢离子转移、环化，并进一步脱氢生成噻吩或烷基噻吩。在400-500℃下，噻吩及烷基噻吩的生成反应是吸热反应，其平衡收率比较高。不饱和硫醇过渡态经负氢离子转移、环化后再夺氢生成四氢噻吩的反应是放热反应，平衡收率很低。固体酸催化剂提供了大量具有脱氢活性中心的L酸，且烯烃与H2S在贫氢的酸催化环境里反应只有生成具有共轭结构的五元噻吩环才是最稳定的，因此噻吩或烷基噻吩是烯烃与H2S反应的主要产物。噻吩与烯烃发生烷基化反应生成烷基噻吩，烷基噻吩在酸性催化剂表面上发生负氢离子转移、环化、脱氢反应生成甲基苯并噻吩。
In order to accounting for the formation mechanism of thiophenic compounds in fluid catalytic cracking （FCC） gasoline, the reaction of hexanethiol and the reaction of heptene with H2S were investigated over solid acid catalysts in ACE unit and FFB unit, respectively. The results showed that over solid acid catalyst hexanethiol was mainly transformed into H2S and olefins, and into thiophene with few probability, according to which, the formations of thiophene and alkylthiophenes in the reaction of heptene with H2S should be with unsaturated thiols rather than saturated thiols as the transformation state. The unsaturated thiols were produced by H2S binding to alkene carbonium ions obtained by the dehydrogenation of olefins on L acid sites of catalysts. Through the process of hydride transfer, cyclization and further dehydrogenation of unsaturated thiols, the thiophene and alkylthiophenes were formed. The formation reaction of thiophenic compounds was an endothermic reaction with higher equilibrium conversion in the temperature range of 400-500℃. Tetrahydrothiophene was formed by unsaturated thiols via hydride transfer,cyclization and hydrogen abstraction, which was an exothermic reaction with much lower equilibrium conversion. Solid acid catalyst could provide a large number of L acid sites with the dehydrogenation activity for olefins, and only 5-member thiophene ring with conjugate structure produced by the reaction of olefins with H2S in the poverty-striken acid-catalysis atmosphere was the most stable in the products, because of which thiophene and alkylthiophenes were the main products of the reaction. Alkylthiophenes were also obtained by the alkylation of thiophene with olefins. Methyl benzothiophenes were produced by hydride transfer, cyclization and dehydrogenation of alkylthiophenes on the surface of acid catalyst.
出处
《石油学报（石油加工）》
EI
CAS
CSCD
北大核心
2008年第3期243-250,共8页
Acta Petrolei Sinica(Petroleum Processing Section)
基金
国家重点基础研究发展规划"973"项目(2006CB202501)资助
关键词
庚烯
H2S
己硫醇
噻吩
烷基噻吩
四氢噻吩
甲基苯并噻吩
生成机理
heptene
H2S
hexanethiol
thiophene
alkylthiophene
tetrahydrothiophene
methyl benzothiophene
formation mechanism
