活性炭催化氧化脱除汽油和柴油中噻吩类硫化物的选择性

Selectivity of oxidative desulfurization of gasoline and diesel fuel using catalytic oxidation method with activated carbon

研究了活性炭催化氧化脱除汽油和柴油中噻吩类硫化物的选择性。采用气相色谱-硫化学发光检测器(GC-SCD)分析了汽油和柴油中噻吩类硫化物的分布及浓度;以活性炭作为催化剂,以30%过氧化氢溶液为氧化剂,在甲酸存在条件下考察了汽油和柴油中噻吩类硫化物催化氧化脱除的选择性,讨论了硫化物中硫原子电子密度对硫化物氧化选择性的影响。结果表明:汽油中噻吩类硫化物主要有噻吩(T)及其烷基衍生物(Talkylated derivatives)和苯并噻吩(BT);而柴油中噻吩类硫化物主要分布有苯并噻吩(BT)及其烷基衍生物(BTalkylated derivatives)和二苯并噻吩(DBT)及其烷基衍生物(DBTalkylated derivatives);硫原子电子密度大于5.716的含3个C烷基噻吩(C3-T)、BT、BTalkylated derivatives、DBT和DBTalkylated derivatives能被催化氧化脱除,硫原子的电子密度越大,其被氧化的速率越快,被脱除的选择性也越大;被脱除选择性顺序为:DBTalkylated derivatives>DBT>BTalkylated derivatives>BT>C3-T;然而硫原子电子密度小于5.716的T,含1个烷基噻吩(C1-T)和含2个C烷基噻吩(C2-T)则不能被氧化脱除。采用此方法,能将初始硫浓度为1200μg·g-1的柴油降低至小于10μg·g-1,可将初始硫浓度为320μg·g-1的汽油降低至155μg·g-1。

In this work, the selectivities of catalytic oxidative desulfurization of gasoline and diesel fuel were investigated. The type and concentration of thiophenic sulfur in gasoline and diesel fuel were determined separately by gas chromatography with a sulfur chemiluminescence detector （GC-SCD） . With activated carbon （AC） and 30% （mass） aqueous solution of H2O2 as catalyst and oxidant respectively, the experimental studies of oxidative desulfurization of gasoline and diesel were carried out. The effect of electron densities of sulfur atom of different organic sulfur species on the oxidative selectivity was discussed. The results showed that gasoline fuel contained mainly thiophene （T） and its derivatives, such as T containing 1-methyl （C1-T）, 2-methyl （C2-T）, 3- methyl （C3-T） substituents and benzothiophene （BT）; diesel fuel contained mainly BT, BT alkylated derivatives, dibenzothiophene （DBT） and DBT alkylated derivatives. The organic sulfur species whose electron densities of sulfur atom were larger than 5. 716 could be oxidized. The higher the electron density, the higher the oxidation rate, and the higher the oxidation reactivity. The reactivity decreased in the order of DBT alkylated derivatives〉DBT〉BT alkylated derivatives〉BT〉C3-T. However, in gasoline, the T, C1-T and C2-T whose electron densities of sulfur atom were smaller than 5. 716 were difficult to be removed by the catalytic oxidation method. The use of oxidative desulfurization could reduce the concentration of total sulfur in the diesel to less than 10μg·g^-1 from original 1200/~g ~ g-1 , and make that in gasoline reduce to 155μg·g^-1 from 320μg·g^-1.