【作者】 井维健；

【导师】 杨朝合；

【作者基本信息】 中国石油大学 ， 化学工程与技术， 2011， 硕士

【摘要】 催化裂化过程中产生的SO_x、NO_x和CO不仅会造成酸雨、光化学烟雾等诸多环境问题,而且会加剧设备腐蚀而影响催化裂化装置的长期安全运转。在诸多控制催化裂化烟气SO_x、NO_x和CO排放的方法中,助剂技术在经济、环保等方面有着独特的优势。研发能够同时消除催化裂化烟气SO_x、NO_x和CO的多功能助剂有着重要意义。首先采用酸法制备了具有尖晶石结构的MgAlCeFe复合氧化物硫转移剂,通过XRD、BET、FT-IR等分析方法对催化剂进行表征,利用固定床微型反应器和DTU-2A热分析仪评价催化剂的SO_x氧化吸附性能和还原再生性能,探讨了元素组成、制备过程和外部环境等因素对硫转移剂结构和性能的影响规律。富镁型镁铝尖晶石具有强吸附SO_x和还原性好的特性,是优异的SO_x吸附材料;氧化铈是促进SO₂氧化生成SO₃的活性组分;铁的主要作用是提高了硫转移剂的还原再生速率。活性组分之间的协同或竞争效应使硫转移剂中各组分的含量存在最优值。有机聚合物聚乙二醇可有效地增大硫转移剂的比表面积、孔容和孔径并促进活性组分的分散,优化了硫转移剂的内部结构,添加10%分子量为2000聚乙二醇的样品性能最佳。在650℃～750℃温度范围内,温度对硫转移剂SO_x饱和吸附容量的影响不明显。氧气对硫转移剂催化性能的发挥起着重要作用,在0～5%浓度范围内,硫转移剂SO_x氧化吸附性能对反应体系中氧气含量的变化是很敏感的。氢气和低碳烃类是促进硫转移剂还原再生的主要活性介质,氢气对硫酸盐的还原分解性能要明显优于丙烷等低碳烃类。温度升高促进了稳定硫酸盐和体相硫酸盐的还原分解从而提高了硫转移剂的再生速率。采用喷雾干燥成型技术生产的SFTS-1工业硫转移剂具有良好的SO_x氧化吸附性能和还原再生性能。提升管循环流化床实验表明:加入系统藏量2.5%的硫转移剂可使再生烟气中SO2的浓度降低89%。青岛石化工业试验表明:硫转移剂可有效降低催化裂化再生烟气SO_x的排放,当助剂加入量占系统藏量2.5%时,烟气中SO_x的脱除率达64.4%,且助剂的活性具有良好的稳定性;助剂的使用对催化裂化产品质量和产物分布没有不利影响,不影响催化裂化装置的正常稳定运转和产品的后续加工。同时消除催化裂化烟气SO_x、NO_x和CO多功能助剂的研究主要基于以下两种思路:向硫转移剂中添加具有NO还原和CO氧化催化功能的活性组分;研发可高效催化NO还原和CO氧化的助剂,与硫转移剂混合使用。向硫转移剂中添加10%氧化铜的催化剂具有最佳的同时消除SO_x、NO_x和CO的综合性能。催化剂NO还原反应的活性与反应体系中氧气浓度密切相关,当O₂/CO浓度比小于0.5时,催化活性良好,当O₂/CO浓度比大于0.5时,催化剂活性大大降低。镁铝尖晶石负载的具有类钙钛矿结构La_2-xSr_xCoO₄复合氧化物催化剂能高效地催化NO还原和CO氧化反应,其中x=0.8样品的活性最佳,催化剂具有良好的水热稳定性,但抗SO₂中毒性能差。更多还原

【Abstract】 Fluid catalytic cracking （FCC） unit is one of the major emission sources of SO_x, NO_x and CO in the oil refineries. Sulfer and nitrogen oxides, kown as the acid rain precursors, are harmful to our environments. They may also cause serious corrosion to the equipments of FCC regenerating systems and have an important effect on the safety, reliability and lifetime of FCC units. The addition of suitable additive to the FCC units is considered to be the most practical and economical option to reduce SO_x, NO_x and CO emissions.MgAlCeFe spinel type mixed oxides are prepared by acid method, characterized by XRD, BET, FT-IR techniques and evaluated as SO_x transfer additive. The effect of active components and preparation methods on the structure and SO_x removal activity of the additive is discussed. Moreover, the performance of SO_x removal is investigated at different reaction conditions. The MgAl spinel type mixed oxide is proven to be an excellent material for SO_x transfer additive due to its SO_x adsorption activity and reducibility of the formed sulfates. Cerium is the main active component for the oxidation of SO₂ to SO₃. Ferrum plays an essential role in the regeneration step. The content of different active components in the additive has an optimal value due to their competitive and synergistic effect. The BET surface area, pore volume and pore diameter of the additive can be improved significantly through addition of macromolecular organic material PEG. The aditive shows optimum SO_x oxidation adsorption and regeneration performance after adding 10% PEG2000. Reaction temperature has no significant influence on the SO_x uptake capacity when the temperature changes between 650℃and 750℃. The additive exhibits better SO_x adsorption performance in the presence of oxygen and the activity is very sensitive to the changes of oxygen concentration. The reduction rate of the additive is strongly influenced by the reductive mediators and the regeneration of the sulfated additive is much more efficient with hydrogen. The stable and bulk sulfate species can only be decomposed at higher reduction temperature and the additive shows better regeneration performance.SFTS-1 SO_x transfer additive produced by spray drying technique has a good SO_x adsorption and regeneration performance. The additive is evaluated on the riser circulating fluidized bed unit and the results shows that more than 89% SO₂ is removed after adding 2.5% additive. The commercial test result shows that the utilization of SO_x transfer additive in the FCC unit can reduce the emissions of SO₂ in flue gas. When the additive makes up 2.5% of the catalyst inventory, the removal efficiency of SO2 reaches 64.4% and the additive exhibits high activity and stability. The addition of SO_x transfer additive to FCC system has no significant influence on the qualities of main products, production distribution and normal operation of the FCC units.The multi-functional additive which can remove SO_x, NO_x and CO is studied on the basis of SO_x transfer additive. Copper is proven to be an active component for NO reduction and CO oxidation and the additive shows optimal performance for simultaneous removal of SO_x, NO_x and CO by introducing 10% CuO to the SO_x transfer additive. The additive shows excellent hydrothermal stability and good resistence to SO₂ posioning. The relative content of oxygen and carbon monoxide has a great influence on the NO reduction activity. The additive shows high NO reduction activity when n（O₂）/n（CO）<0.5 and the activity declines greatly when n（O₂）/n（CO）>0.5. MgAl₂O₄-supported La_2-xSr_xCoO₄ mixed oxide catalyst has a good catalytic performance for NO reduction an CO oxidation and optimum catalytic activity could be obtained when x=0.8. But the catalytic activity is greatly decreased with exposure of the catalyst to atmosphere containing 0.02% SO2.更多还原