Enhanced performance of oxidation of rosalva (9-decen-1-ol) to costenal (9-decenal) on porous silicon-supported silver catalyst in a microstructured reactor

Abstract

The use of metal-assisted HF chemical etching as a convenient technique to produce a few microns thick porous layer in silicon microchannels was demonstrated. Gas phase selective oxidation of rosalva to its aldehyde (costenal) was performed in glass/silicon microstructured reactors at temperatures of 375-475 °C on silver catalyst which was deposited on both porous and flat silicon surface by sputter-coating. The effects of temperature (375-475 °C), rosalva concentration (1.17%-3.43%), O2 to rosalva ratio (0.5-20) and residence time on the reaction were investigated. The reactivity of rosalva on the porous silicon supported silver was 5.7-6.4 times higher than on the thin film silver catalyst at 450 °C. Furthermore, activation energy for the porous silicon supported silver was lower. Isothermal conditions in the microreactors allowed high conversion and selectivity to be achieved in a wide range of temperature and oxygen concentration. At typical reaction conditions (1.75% rosalva, O2/rosalva = 3, residence time 18 ms and 450 °C), conversion of 97% and selectivity of 95% to costenal was achieved, corresponding to a turnover frequency of 268 h-1.