Preparation of Zn-Al oxide catalyst and its catalytic performance in propylene carbonate synthesis from urea and propylene glycol on a fixed-bed reactor

作者：An, Hualiang; Ma, Yuanhui; Zhao, Xinqiang^*; Wang, Yanji

来源：Catalysis Today, 2016, 264: 136-143.

DOI：10.1016/j.cattod.2015.09.006

• Urea
• Propylene glycol
• Zn-Al oxide catalyst
• Propylene carbonate
• Reaction pathway

The synthesis of propylene carbonate (PC) from urea and propylene glycol (PG) catalyzed by Zn-Al oxide catalyst was successfully performed on a fixed -bed reactor. The appropriate conditions for the preparation of Zn-Al oxide were obtained as follows: Zn(NO3)(2) and Al(NO3)(3) as the precursors of Zn-Al oxide, NaOH and Na2CO3 aqueous solution as the precipitant, using parallel-flow precipitation method, pH = 9.5, aging at 40 degrees C for 24 h, and calcination at 500 degrees C for 4 h. The structures, compositions, and acidities of the Zn-Al oxide catalysts were characterized by means of XRD, N-2 adsorption -desorption, ICP-AES and NH3-TPD. Characterization and activity evaluation results indicate that Zn-Al oxide has an excellent catalytic performance for PC synthesis and specific surface area is the main factor influencing the catalytic performance of Zn-Al oxide. Under the suitable reaction conditions of n(PG):n(urea) = 6:1, Zn-Al oxide volume of 3 mL, reaction temperature of 140 degrees C and LHSV = 0.8 h(-1), the yield and selectivity of PC could reach 87.4% and 96.8%, respectively. Furthermore, the yield of PC was no less than 85% during the 60 h stability test, demonstrating that Zn-Al oxide catalyst exhibits a pretty stable activity. Additionally, React-IR was employed to investigate the reaction pathway for PC synthesis from urea and PG. The results show that the reaction of PC synthesis proceeds in two steps: 2-hydroxypropyl carbamate (HPC) is formed from urea and PG first and then PC is produced by elimination of an ammonia from HPC molecule.

• 出版日期2016-4-15
• 单位河北工业大学