Titanium silicalite-1 (TS-1) is used as a powerful and versatile catalysts for several industrial selective oxidation processes. It has, however, not yet made its way to technical application for the epoxidation of the unsaturated fatty acid methyl esters (FAMEs) of biodiesel with hydrogen peroxide in the liquid phase. This is mainly due to the limited access of the large FAME molecules with respect to the TS-1 micropores and due to diffusion limitations occurring in typical industrial TS-1 catalyst pellets. This presentation will highlight three examples for enhancing the accessibility and diffusion of the catalytically active Ti sites for FAME epoxidation in TS-1-based catalysts. In the first example, nanocrystals of TS-1 are applied into which an additional mesopore system is introduced to alleviate transport hindrances. The second examples reports nanosheets and pillared TS-1 catalysts with high accessibility to the Ti sites. The combination of TS-1 crystals and activated carbon beads in composite catalysts represent the third example. With a hierarchically structured micro-/mesoporous TS-1 catalyst containing less than 0.6 wt.-% Ti, an epoxide selectivity over 90 % at a FAME conversion over 90 % can be reached. The presented results proof, however, that a complex interplay of accessibility and diffusion as well as nature and surrounding of the active Ti sites is key for achieving successful and efficient biodiesel epoxidation.

Epoxidation of biodiesel over hierarchical TS-1-based catalysts: Improvement of diffusion or accessibility?

255th National Meeting (2018)

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