Auepattana-Aumrung Chanon, Márquez Victor, Wannakao Sippakorn, Jongsomjit Bunjerd, Panpranot Joongjai, Praserthdam Piyasan
Center of Excellence On Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok, 10330, Thailand.
SCG Chemicals, Co., Ltd., 1 Siam Cement Road, Bangsue, Bangkok, 10800, Thailand.
Sci Rep. 2020 Aug 12;10(1):13643. doi: 10.1038/s41598-020-70568-z.
The Na-ZSM-5 catalysts (SiO/AlO molar ratio = 20, 35, and 50) were prepared by rapid crystallization method to investigate their performance in butene cracking reaction. The XRD, XRF, NH-TPD, FT-IR, TPO, UV-Vis, and H, Al, Si MAS NMR techniques were used to identify the physical and chemical properties of Na-ZSM-5 catalysts. The silanol group (Si-OH) was the main acid site of Na-ZSM-5, and it was proposed to be the active site for the butene cracking reaction. The butene conversion and coke formation were associated with the abundance of silanol groups over the Na-ZSM-5 catalyst. The dealumination, resulting in the deformation of tetrahedral framework aluminum species was a key factor for Na-ZSM-5 catalyst deactivation, because of the Si-O-Al bond breaking and formation of Si-O-Si bond. The stability of the Si-O-Al bond was linked to the molar number of sodium since the Na atom interacts with the Si-O-Al bond to form Si-ONa-Al structure, which enhances the stability of the silanol group. Therefore, the Si-ONa-Al in zeolite framework was an essential structure to retain the catalyst stability during the reaction. The Na-ZSM-5 with the lowest SiO/AlO molar ratio showed the best performance in this study resulting the highest propylene yield and catalyst stability.
采用快速结晶法制备了Na-ZSM-5催化剂（SiO/AlO摩尔比分别为20、35和50），以研究其在丁烯裂解反应中的性能。采用XRD、XRF、NH-TPD、FT-IR、TPO、UV-Vis和H、Al、Si MAS NMR技术对Na-ZSM-5催化剂的物理化学性质进行了表征。硅醇基（Si-OH）是Na-ZSM-5的主要酸性位点，被认为是丁烯裂解反应的活性位点。丁烯转化率和焦炭生成与Na-ZSM-5催化剂上硅醇基的数量有关。脱铝导致四面体骨架铝物种变形是Na-ZSM-5催化剂失活的关键因素，这是由于Si-O-Al键的断裂和Si-O-Si键的形成。Si-O-Al键的稳定性与钠的摩尔数有关，因为Na原子与Si-O-Al键相互作用形成Si-ONa-Al结构，从而提高了硅醇基的稳定性。因此，沸石骨架中的Si-ONa-Al是反应过程中保持催化剂稳定性的重要结构。在本研究中，SiO/AlO摩尔比最低的Na-ZSM-5表现出最佳性能，丙烯产率和催化剂稳定性最高。
