Potassium-Ion-Exchanged Zeolites for Sustainable Production of Acrylic Acid by Gas-Phase Dehydration of Lactic Acid

详细信息    查看全文

• 作者：Bo Yan ; Li-Zhi Tao ; Azhar Mahmood ; Yu Liang ; Bo-Qing Xu
• 刊名：ACS Catalysis
• 出版年：2017
• 出版时间：January 6, 2017
• 年：2017
• 卷：7
• 期：1
• 页码：538-550
• 全文大小：891K
• ISSN：2155-5435

文摘

Development of high-performance solid acid catalysts for chemicals and materials production from bioresourced feedstock has become an important research topic in heterogeneous catalysis for renewable energy and green chemistry. We provide herein a comprehensive study on the catalytic performance of various K⁺-exchanged zeolites (K_xNa_1-xZ_y, x = 0.90–0.98) with similar molar K/Al ratios for acrylic acid (AA) production by gas-phase dehydration of lactic acid (LA) and discuss the effects of zeolite type (Z = ZSM-22, ZSM-35, MCM-22, ZSM-11, ZSM-5, ZSM-5/ZSM-11, and β) and SiO₂/Al₂O₃ ratio (y). ZSM-5 and β are found more efficient than the other zeolites for this LA-to-AA reaction. Variation of y in the zeolite (β and ZSM-5) is shown to significantly affect the catalytic performance: not only higher AA selectivity and yield but also better catalytic stability is achieved by lowering y. A K_0.97Na_0.03ZSM-5_27 is then identified as the best-performing catalyst, offering very high AA selectivity (80–81 mol%) and yield (74–78 mol%) at 360 °C under high LA space velocity (WHSV_LA = 2.1 h^–1). This catalyst also shows a remarkable long-term stability, being capable to maintain a high AA selectivity (>70 mol%) and yield (>55 mol%) for longer than 80 h. Furthermore, an in situ calcination of the used catalyst with flowing air at 450 °C is shown to be efficient for complete catalyst regeneration. Correlating the catalyst performance with its surface acid–base property measured by NH₃- and CO₂-TPD clearly uncovers that balance between the surface acidity and basicity would be a key, besides Z and y of the zeolite, to the catalyst performance.