脱氮吸附剂深度脱除模拟含氮油中氮化物的研究

Deep removal of nitrogen-containing compounds from vehicle fuels using denitrogenation adsorbent

将磷钨酸、甲醛气体负载于介孔分子筛SBA-15中制备脱氮吸附剂,其中SBA-15、磷钨酸、甲醛的质量比为10∶7∶3。以喹啉、吲哚和咔唑为目标氮化物,二甲苯及二甲苯和十二烷的混合液为溶剂配制模拟含氮油,考察了反应温度、氮化物类型对脱氮反应速率的影响以及磷钨酸、甲醛的脱氮机制。结果表明,磷钨酸可以有效脱除碱性氮化物和低浓度非碱性氮化物,甲醛能强化吸附剂对非碱性氮化物的选择性。在70℃、脱氮吸附剂与高浓度模拟含氮油质量比为2.0∶30.0的条件下,模拟含氮油中的氮化物在90min内可以被深度脱除。磷钨酸对碱性氮化物的脱除机制为磷钨酸和碱性氮化物间的配合作用和酸碱反应,磷钨酸对非碱性氮化物的脱除机制为氮化物和甲醛在酸催化下缩合反应生成聚合物。反应吸附剂再生回用后的脱氮能力随氮化物碱性的增强而减弱。

Highly efficient denitrogenation adsorbent was prepared by loading phosphotungstic acid （PTA） and formaldehyde gases on mesoporous molecular SBA-15. The mass ratio of SBA-15 ： PTA ： formaldehyde gases was 10 ： 7 ：3. Quinoline,indole and carbazole were used as the target nitrogen-containing compounds in vehicle fuels in which xylene or the mixture of xylene and dodecane was used as the solvents. The effect of temperature and concentration of nitrogen-containing compounds on denitrogenation rate was investigated; the deep denitrogenation mechanism of PTA and formaldehyde was also studied. The results showed that the basic nitrogen-containing compounds and non- basic compounds with low-concentration in model fuels can be deeply removed by adsorbent without loading formalde- hyde. The selectivity of the adsorbent in the removal of non-basic nitrogen-containing compounds and the reaction rate benefited from the existence of formaldehyde in the pores. Model fuels with ultra-low concentration nitrogen were obtained in 90 min at 70℃ when the mass proportion between adsorbent and model fuels containing quinoline,indole and earbazole was 2.0 ： 30.0. The mechanism of basic nitrogen-containing compounds removal by PTA was the formation of charge-transfer complexes and acid-base reaction;while the non-basic nitrogen-containing compounds were removed by the condensation reaction with formaldehyde under the control of PTA. The regenerated denitrogenation adsorbent was recycled and the efficiency declined according with the increase of the basicity of nitrogen-containing compounds.