CeY分子筛中有效脱硫物种活性位的构建及其吸附机理研究

以不同焙烧温度和Ce负载量的CeY分子筛为研究对象,运用XRD及N_2吸附表征其织构性质;运用吡啶吸附红外光谱法剖析了分子筛中活性位的化学属性;采用固定床评价其对噻吩模拟油的吸附脱硫性能及芳烃和烯烃对噻吩脱除的影响;并结合红外光谱和GC-SCD技术分析了其脱硫机制。结果表明,CeY样品经150℃焙烧后,其超笼中具备高含量的B酸和Ce羟基化物种活性位,两者协同增强了噻吩低聚反应能力,进而提高了其吸附穿透硫容量(18.45 mg (S)/g);而提升焙烧温度和Ce负载量会严重降低其有效活性位的数量,削弱了噻吩低聚反应能力,其吸附穿透硫容量显著减小(4.03 mg (S)/g)。当加入烯烃和芳烃后,CeY-12.3-150吸附剂对含低浓度(质量分数)1-己烯(1.0%)和苯(0.1%)的噻吩模拟油依旧保持较高吸附穿透硫容量;但随两者含量的持续增加,其硫容量急剧下降。其主要分别归因于噻吩烷基化反应的发生及“S-H”键的作用模式。

Fabrication of effective desulfurization species active sites in the CeY zeolites and the adsorption desulfurization mechanisms

A series of CeY zeolites with different cerium loadings and calcined at different temperatures were prepared and used as the adsorbent for the desulfurization of thiophene containing model oil. The CeY zeolites were characterized by XRD, N₂ sorption, FT-IR spectroscopy and GC-SCD and GC-MSD techniques. The effects of aromatics and olefins on the adsorption desulfurization performance were investigated and the active species and reaction mechanism for the adsorption desulfurization on CeY zeolites were probed. The results indicate that the CeY zeolite calcined at 150 ℃ is provided with a large number of Brönsted acid sites and hydroxylated cerium species in the supercages, which can synergistically promote the thiophene oligomerization and then enhance the sulfur breakthrough adsorption capacity (18.45 mg (S)/g). However, a further increase in the calcination temperature and cerium loading may greatly reduce the number of active sites for the adsorption desulfurization and suppress the thiophene oligomerization reaction, leading to a significant decrease in the sulfur breakthrough adsorption capacity (4.03 mg (S)/g). For the thiophene model oils containing low concentration of 1-hexene (< 1.0%) or benzene (< 0.1%), the CeY-12.3-150 zeolite (with a cerium loading of 12.3% and calcined at 150 ℃) also exhibits a relatively high sulfur breakthrough adsorption capacity. However, a further increase in the content of 1-hexene or benzene in the feed may lead to a sharp decrease in the sulfur breakthrough adsorption capacity, due to the alkylation of thiophene and the adsorption mode of "S-H" bonding.