Producing Pyridines via Thermocatalytic Conversion and Ammonization of Waste Polylactic Acid over Zeolites

详细信息    查看全文

• 作者：Lujiang Xu ; Qian Yao ; Zheng Han ; Ying Zhang ; Yao Fu
• 刊名：ACS Sustainable Chemistry & Engineering
• 出版年：2016
• 出版时间：March 7, 2016
• 年：2016
• 卷：4
• 期：3
• 页码：1115-1122
• 全文大小：357K
• ISSN：2168-0485

文摘

In this study, polylactic acid served as raw material to produce fine chemicals (pyridines) via a thermocatalytic conversion and ammonization (TCC-A) process. Ammonia was employed as not only carrier gas but also a reactant in this process. The thermal decomposition behavior of PLA under N₂ or NH₃ atmosphere was investigated. Different catalysts, including MCM-41, β-zeolite, ZSM-5 (Si/Al = 50) and HZSM-5 with different Si/Al ratios (Si/Al = 25, 50, 80) were also screened. Reaction temperature and residence time, which may affect the pyridines production, were investigated systematically. It was verified that all the investigated factors, including catalyst structure, catalyst acid amounts, reaction temperature, and residence time, influenced the PLA conversion and the pyridines production. The highest pyridines yield, 24.8%, was achieved by using HZSM-5 (Si/Al = 25) at around 500 °C. The catalyst regeneration tests were carried out. It demonstrated that the catalyst was stable after five regenerations and the catalytic activity did not change significantly. A possible reaction pathway from PLA to pyridines was also proposed. PLA initially thermally decomposed to form lactic acid and some byproducts such as acetaldehyde, acetone, etc., and then lactic acid, the mixture of acetaldehyde and acetone, or other byproducts reacted with ammonia to form imines and finally underwent complicated reactions to form pyridines.