In the research of directly synthesizing H-form ZSM-5, ammonium hydroxide is commonly used as an alkali source instead of NaOH to avoid multiple ion exchange steps. However, the volatile nature and the lack of structure-directing effect of ammonium hydroxide limit its application in practical. In this study, n -butylamine (NBA) was used as the main alkali source to directly prepare HZSM-5 zeolites with SiO 2 /Al 2 O 3 ratios ranging from 40 to 300 under traditional hydrothermal conditions. The influence of the amount of NBA, ethanol, seed, and pre-crystallization on the synthesis products was investigated under the condition of SiO 2 /Al 2 O 3 = 80. Theoretical simulation suggested that n -butylamine cations (NBA + ) play the most potent directing role in the formation of the MFI structure but could lead to difficulties in removal during calcination. The addition of ethanol as the zeolite growth modifier (ZGM) could decrease the usage of NBA and reduce the difficulties in calcination, and the addition of seed provided the conditions for initiating crystallization in the system that could not spontaneously nucleate. HZSM-5 with different SiO 2 /Al 2 O 3 ratios were prepared under the optimal crystallization conditions, and the as-synthesized samples exhibited superior textural and acid properties compared to commercial zeolite. Finally, the 1 L scale-up synthesis and MTP reaction were conducted to demonstrate the practicality of this economically and environmentally-friendly synthesis strategy.
Fuwei Gan,Wen Liu,Xinbao Zhang,Maochen Qian,Shaoguo Li,Yuzhong Wang,Junjie Li,Xiangxue Zhu,Xiujie Li
Primary amines, exemplified by n-butylamine, serve as critical intermediates in the synthesis of pharmaceuticals and agrochemicals. Amination of n-butanol with ammonia over supported cobalt catalysts represents a promising synthetic route. To enhance the catalytic performance of Co-based amination catalysts, we reported an acid-treated strategy that allows for precise regulation of cobalt speciation. Among the evaluated supports, silicalite-1 demonstrated superior amination performance, attributed to its unique ability to enhance cobalt dispersion and suppress acid-induced side reactions. Through acid treatment, oversized Co3O4 nanoparticles are selectively removed, thereby preserving highly dispersed cobalt species. Under rigorous reaction conditions (WHSV = 2.5 h-1), the acid-treated catalyst achieved 90% selectivity toward n-butylamine, accompanied by improved stability compared to untreated counterparts. Mechanistic investigations revealed that well-dispersed metallic Co0 nanoparticles promoted selective C-N bond formation via efficient coupling, whereas larger cobalt domains facilitated dehydrogenation-driven carbon deposition pathways. This work establishes a clear structure-performance relationship for cobalt-based amination catalysts, offering a blueprint for sustainable amine production.
危险品化学品经营许可证（带存储）