RESUMEN
This study focuses on increasing the selectivity to methyl lactate from sugars using stannosilicates as heterogeneous catalyst. All groupâ I ions are found to have a promoting effect on the resulting methyl lactate yield. Besides, the alkali ions can be added both during the preparation of the catalyst or directly to the solvent mixture to achieve the highest reported yield of methyl lactate (ca. 75 %) from sucrose at 170 °C in methanol. The beneficial effect of adding alkali to the reaction media applies not only to highly defect-free Sn-Beta prepared through the fluoride route, but also to materials prepared by post-treatment of dealuminated commercial Beta zeolites, as well as ordered mesoporous stannosilicates, in this case Sn-MCM-41 and Sn-SBA-15. These findings open the door to the possibility of using other preparation methods or different Sn-containing silicates with equally high methyl lactate yields as Sn-Beta.
Asunto(s)
Lactatos/química , Metales Alcalinos/química , Dióxido de Silicio/química , Sacarosa/química , Estaño/química , Catálisis , Sales (Química) , Zeolitas/químicaRESUMEN
Methanol, ethanol, and i-propanol were converted under methanol-to-gasoline (MTH)-like conditions (400 degrees C, 1-20 bar) over zeolite H-ZSM-5. For methanol and ethanol, the catalyst lifetimes and conversion capacities are comparable, but when i-propanol is used as the reactant, the catalyst lifetime is increased dramatically. In fact, the total conversion capacity (calculated as the total amount of alcohol converted before deactivation in g(alcohol)/g(zeolite)) is more than 25 times higher for i-propanol compared to the lower alcohols. Furthermore, when i-propanol is used as the reactant, the selectivity toward alkanes and aromatics declines rapidly over time on stream, and at 20 bar of pressure the liquid product mixture consists almost exclusively of C(4)-C(12) alkenes after approximately a third of the full reaction time. This discovery could open a new route to hydrocarbons via i-propanol from syn-gas or biobased feedstocks.