Regeneration of a supported Nafion® catalyst for the double-bond isomerization of octadecenes

Abstract

We studied solvent-based regeneration techniques on a commercial Nafion/SiO2 catalyst (SAC-13®, BASF). The test reaction was the double-bond isomerization of octadecenes, which are used in paper sizing agents and drilling fluids. The spent catalyst deactivated from surface coverage of octadecenes and higher-molecular weight oligomers. Polar and nonpolar solvents were tested in both batch and continuous regenerations. Up to 71% of the pore volume and 67% of the surface area were recovered, in the mesoporous regime. Batch and continuous isomerization experiments showed that a threshold quantity of oligomer must be removed, otherwise the activity of the regenerated catalysts does not correlate well with residual oligomer or the acid site concentration, because some solvents could not be completely displaced. The most effective solvent was m-xylene. Some acid sites were never recovered. Diffusional limitations and faster deactivation resulted in lower turnover frequencies in regenerated catalysts, in part due to decreased pore volume and in part because residual oligomer reacted with fresh monomer, such that fewer oligomerization events were necessary to close the pores in subsequent tests.