The glycerol conversion into acrolein using zeolites still faces several challenges and their overcoming depends on the full understanding of the physical and chemical characteristics of the catalytic system. The main tasks to be cooperatively explored by us with Prof. Sievers Research group are: (1) The micropores of the zeolites impose diffusional constraints for glycerol to reach the active sites and, therefore, hierarchical zeolites seem to be an option for improving catalytic performance. (2) The Brønsted acid sites of the zeolites lead not only to the formation of acrolein, but also to coked molecules of polyaromatics and polyethers; a chance to interfere in coke formation is to deal with acid sites densities (we have evidences that coke is prone to formation in neighboring acid sites). (3) Strong Brønsted acid sites also lead to coke and consequently catalyst deactivation. (4) The hierarchical structure of the zeolite is beneficial in preventing coke as blocking of pores. We have evidence that the synthesis procedure we mentioned in the original proposal, based on organosilanes and emulsion as structure directing agents, is a worthy approach to obtain well-defined materials to perform the four tasks mentioned. In conclusion, to correlate them we need complete physical and chemical characterization of the catalysts and to gain knowledge of the catalyst performance. More particularly, we need to elucidate the relevant surface chemistry, which will be done by means of in-situ infrared spectroscopy under reaction conditions. Additionally, by means of this characterization technique we can also obtain information regarding the surface acidity, the character of the acid sites (Brønsted or Lewis type) and how these sites interfere in the zeolites performance and coke formation.
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