Al_(2)O_(3)基羰基硫水解催化剂再生方法研究

Study on Regeneration Method of Al_(2)O_(3)-based Catalyst after Hydrolysis of Carbonyl Sulfide

羰基硫(COS)水解技术旨在将难以脱除的有机硫COS在催化剂作用下转化为易于除去的无机硫H_(2)S,该技术被认为是工业烟气有机硫间接脱除的重要手段。催化剂常因积硫及表面硫酸盐化导致中毒而失活,因此保持催化剂的活性与稳定性是COS水解技术的最大挑战,探索简单可靠的失活催化剂再生办法是提高COS水解技术实用性与经济性的重要手段。本研究根据COS水解催化剂的中毒特点,开发了“焙烧+水洗”的催化剂再生方法,用以恢复Al_(2)O_(3)基催化剂的水解催化活性。结果显示,对失活后的单纯Al_(2)O_(3)催化剂进行再生处理时,只有当焙烧温度高于650℃,催化剂水解活性能够恢复,短期内COS水解转化率高于98%,随着反应时间增加至8小时,其逐渐再次失活。对La-Al_(2)O_(3)催化剂进行再生处理时,当焙烧温度为550℃、650℃或850℃时,催化剂活性均能被彻底恢复,水解转化率8 h内保持在99.5%以上,并且随着反应时间延长不发生明显的活性下降。表征结果显示,虽然催化剂失活后由于硫沉积导致比表面积略有增大,但平均孔径减小导致传质阻碍,严重影响了催化剂活性。“焙烧+水洗”的再生方法对沉积硫的脱除效果明显,孔道结构的复原是催化剂活性恢复的主要原因。

The hydrolysis of carbonyl sulfide(COS)aims to catalytically convert the difficult organic sulfur COS into the inorganic H_(2)S that can be easily removed.This technology is considered a crucial means for indirectly organic sulfur removal from industrial flue gases.The biggest challenge of COS hydrolysis technology is to maintain the activity and stability of catalysts,which are often deactivated due to sulfur accumulation and surface sulfation poisoning.Exploring a simple and reliable method for catalyst regeneration is an essential approach to enhance the practicality and cost-effectiveness of COS hydrolysis technology.In this study,a catalyst regeneration method of“calcination+washing”has been developed for restoring the deactivated Al_(2)O_(3)-based catalysts after COS hydrolysis,according to their poisoning mechanisms.Results show that only when the calcination temperature exceeds 650℃,the activity of Al_(2)O_(3)catalyst can be restored after washing,achieving a COS conversion of over 98%in the short term.As the reaction time increases to 8 hours,the catalyst is gradually deactivated again.In the case of La-Al_(2)O_(3)catalyst,when the calcination temperature is 550℃,650℃or 850℃,the catalyst activity can be completely restored,the hydrolysis conversion rate remains above 99.5%within 8 h,and the activity does not decrease significantly with the extension of reaction time.Characterization results showed that although the surface ratio of the catalysts could be slightly increased due to deposited sulfur after deactivation,the mass transfer was hindered due to the decrease of the average pore diameter,which seriously affected the catalyst activity.The regeneration method of"roasting+washing"has obvious effect on the removal of deposited sulfur,and the recovery of pore structure is the main reason for the recovery of catalyst activity.