Huang Lin, Theng De Sheng, Zhang Lili, Chen Luwei, Wang Chuan, Borgna Armando
Heterogeneous Catalysis, Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research, 1 Pesek Road, Jurong Island, 627833 Singapore.
ACS Omega. 2019 May 3;4(5):8146-8166. doi: 10.1021/acsomega.9b00745. eCollection 2019 May 31.
We have studied unsupported, silica gel- and amorphous silica-alumina-supported catalysts derived from K salts for the vapor-phase dehydration of lactic acid (LA) to acrylic acid (AA). A catalytic study shows that the supported catalysts improve the activity and selectivity for the production of AA and decrease the selectivity for the production of propionic acid (PA). The silica-alumina-supported catalysts remain fairly stable in the catalytic performance during 90 h of reaction. The IR spectroscopic characterization combined with the catalytic study demonstrates that potassium lactate (CHKO) in situ generated from LA and a K salt is an important reaction intermediate for the production of AA and the catalytic stability is associated with the chemical stability of CHKO and the activity for the regeneration of CHKO in the catalytic cycle. On silica-alumina, CHKO is well stabilized and smoothly regenerated during the reaction, leading to the good catalytic stability. This work suggests for the first time that lactate salt acts as the true catalytic active species for the dehydration of LA to AA. We also propose a predominant reaction pathway for the vapor-phase dehydration of LA to AA with K salt catalyst systems.
我们研究了由钾盐衍生的无载体、硅胶负载和无定形硅铝负载的催化剂，用于乳酸（LA）气相脱水制丙烯酸（AA）。催化研究表明，负载型催化剂提高了AA生产的活性和选择性，并降低了丙酸（PA）生产的选择性。硅铝负载的催化剂在90小时的反应过程中催化性能保持相当稳定。红外光谱表征结合催化研究表明，由LA和钾盐原位生成的乳酸钾（CHKO）是AA生产的重要反应中间体，催化稳定性与CHKO的化学稳定性以及催化循环中CHKO再生的活性有关。在硅铝上，CHKO在反应过程中得到良好的稳定并顺利再生，从而导致良好的催化稳定性。这项工作首次表明乳酸盐是LA脱水制AA的真正催化活性物种。我们还提出了钾盐催化剂体系中LA气相脱水制AA的主要反应途径。
