Critical Contribution of Mesoporosity to the Stability of Zeolitic Catalysts for Oleate Isomerization in Continuous Flow Reactor

Two types of hierarchical micro-mesoporous materials, as prepared from the zeolites with structure of 10-MR (10-membered rings) ferrierite and 12-MR faujasite Y, have been tested as catalysts of isomerization of methyl oleate in continuous flow conditions. The catalysts have been characterized by X-ray diffraction (XRD), nitrogen physisorption, transmission electron microscopy (TEM), NH3 thermal programmed desorption (TPD), and 27Al MAS NMR. The reaction products have been identified by GC–MS and MALDI–TOF/TOF–MS, quantified by GC–FID, and their cold-flow properties for use as diesel biofuel have been evaluated by differential scanning calorimetry (DSC). The preparations of catalysts by recrystallization in cetyltrimethylammonium (CTA) solution have produced different structural mesoporosity in the two kinds of zeolites, with filling of previous mesopores in faujasite and opening of a bottle-necked negative-crystal mesoporosity in ferrierite. This last type of material has remarkably improved the stability of the isomerization reactions, with 98 wt% conversion of methyl oleate and 55% selectivity of branched monoenoic fatty esters upon 8 h time-on-flow, an uncommon result among the literature available on the continuous-flow experiments. The better results obtained on ferrierite catalysts, with crystallization points on the average 8 °C lower than for faujasite catalysts, have confirmed the shape selectivity of ferrierite structure for alkene isomerization reactions.