Preparation, characterization and catalytic performance study of La-TS-1 catalysts

Abstract

Lanthanum (La) was substituted into a titanium silicalite 1 (TS-1) framework via two different synthetic approaches, i.e., in situ hydrothermal synthesis and ultrasonic immersing methods. La inhibited Ti to enter into the TS-1 framework during in situ hydrothermal synthesis, and thus Ti erosion gave rise to poor catalytic activity for butadiene (BD) epoxidation. While catalysts prepared by an ultrasonic immersing method were testified as fine ones by mutually complementary characterization and catalytic tests. Extraframework-La and Si–OH caused by framework-La enhanced the acidity of TS-1. Adequate intensity of acidity aroused from 8 wt% La modified had activated H₂O₂ for BD epoxidation rather than promoting the solvolysis reactions of the epoxide. Moreover, interactions between framework-La and the Ti active center via O weakened the [Ti–O] bond, which facilitated active intermediate formation. As a result, H₂O₂ conversion and utilization, along with vinyloxirane (VO) yield and TON were highly promoted with appropriate content of La modified.