摘要
乙烯裂解原料劣质化导致裂解汽油中氮含量显著增加,开发新型加氢脱氮(HDN)催化体系以适应高氮裂解汽油工况具有重要意义。以常用的Mo/Al_(2)O_(3)为模型催化剂,通过控制载体预处理方式来调控催化剂微观结构,并采用X射线衍射(XRD)、H2程序升温还原(H_(2)-TPR)、高分辨率透射电镜(HRTEM)、X射线光电子能谱(XPS)、吡啶红外(Py-IR)等表征手段对催化剂进行表征,系统地研究了载体预处理方式对Mo/Al_(2)O_(3)催化剂结构及HDN催化反应性能的影响。结果表明:对于Mo/Al_(2)O_(3)催化剂,载体经酸、碱预处理前后MoS_(2)活性组分均呈单层分散状态;酸、碱预处理可调变催化剂表面酸性、活性相与载体作用强度,并最终影响钼物种硫化度以及表面S和Mo物质的量之比(S/Mo比);吡啶HDN反应受加氢(HYD)和C—N氢解(CNH)共同作用:低吡啶转化率(小于20%)下HDN主要与邻近不饱和配位位点(CUS)数目有关;而吡啶转化率较高(约50%)时HDN受CUS数目和Brønsted酸(B酸)性质共同影响,即载体经碱处理得到的催化剂具有较适宜的表面S/Mo比和B酸量,有利于获得更高的吡啶转化率。上述研究成果为后续开发高效Mo基HDN催化剂提供了重要指导。
The deterioration of feedstock for ethylene production has led to a remarkable increase in nitrogen content in pyrolysis gasoline(py-gas).Developing novel hydrodenitrogenation(HDN)catalysts is therefore of great significance to process py-gas with higher nitrogen content.In this paper,we adopted commonly used Mo/Al_(2)O_(3) as model catalyst,and via various support treatment we have successfully manipulated catalysts structural properties.Catalysts were characterized by various techniques,including X-ray diffraction(XRD),H_(2)-temperature programmed reduction(H_(2)-TPR),High-resolution transmission electron microscopy(HRTEM),X-ray photoelectron spectroscopy(XPS)and Pyridine-Fourier transform infrared spectroscopy(Py-IR).We systematically investigated the effects of support treatment on structural properties of Mo/Al_(2)O_(3) catalysts and their HDN performance for py-gas.The results showed that for all Mo/Al_(2)O_(3) samples,MoS_(2) active species were well-dispersed in mono-layer state on Al_(2)O_(3) support for catalysts with and without support treatment.Citric acid and ammonia treatment could effectively modulate surface acidity and active sites-support interaction,which finally affected sulfurization of molybdenum species as well as surface S/Mo molar ratio.It was also revealed that pyridine HDN was governed by hydrogenation(HYD)and C—N hydrogenolysis(CNH)processes,which was,under lower pyridine conversion condition(less than 20%),HDN performance was mainly related with unsaturated coordination sites(CUS)amount,and under higher pyridine conversion condition(approximately 50%),HDN performance could be well-interpreted by CUS amount and Brønsted acid(B acid)property,catalyst after support alkali-treatment with proper surface S/Mo molar ratio and B acidity showed superior HDN activity.Above all,these results provide us important guidance for research and development of Mo-based HDN catalysts.
作者
王健
朱俊华
叶迎春
王万民
陈梁锋
杨为民
WANG Jian;ZHU Junhua;YE Yingchun;WANG Wanmin;CHEN Liangfeng;YANG Weimin(SINOPEC Shanghai Research Institute of Petrochemical Technology Company Limited,State Key Laboratory of Green Chemical Engineering and Industrial Catalysis,Shanghai 201208,China)
出处
《化学反应工程与工艺》
CAS
2023年第4期306-312,共7页
Chemical Reaction Engineering and Technology
关键词
裂解汽油
加氢脱氮
载体预处理
钼基催化剂
构效关系
pyrolysis gasoline
hydrodenitrogenation
support treatment
Mo-based catalyst
structureperformance relationship