Abstract
Skeletal isomerization of linear unsaturated fatty acids is important in the production of branched-chain saturated fatty acids with diverse applications. This reaction can be efficiently catalyzed by ferrierite (FER) zeolite. The reaction, however, suffers from diffusion limitations in the 10-membered ring channels. Herein, we report a method for the synthesis of hierarchically porous FER zeolite via transformation of FAU precursor driven by N-methylpyrrolidine (NMP) and amphiphile 1,2-dimethyl-3-hexadecyl-1H-imidazol-3-ium bromide (C16dMImz) as the structure-directing agent (SDA) and a mesoporogen, respectively, under hydrothermal conditions. This dual-template approach allows tuning the morphological and textural properties of the mesoporous FER materials by varying the concentration of the mesoporogen in the initial gel. The optimized FER sample is characterized by a high mesoporous volume (0.19 cm3 g-1), large external surface area (∼120 m2 g-1) and reduced crystal size in the a- and c-dimensions. This implies shortened diffusional pathways in the 10-membered ring channels. These modifications led to a significantly enhanced catalytic performance of hierarchical FER zeolite in the isomerization of fatty acids in comparison with a bulk FER reference zeolite.
Highlights
The annual global production of oils and fats is estimated to be more than 160 million metric tonnes [1,2]
We developed a method for the one-pot synthesis of hierarchically porous FER zeolite via FAU reconstruction in the presence of N-methylpyrrolidine (NMP) and 1,2-dimethyl-3-hexadecyl-1H-imidazol-3-ium bromide (C16dMImz) as, respectively, nanoand mesoscale structure-directing agent (SDA)
During the first 5 days, only a minor decrease in the amount of FAU is observed by X-ray diffraction (XRD)
Summary
The annual global production of oils (mainly palm, soybean and rapeseed) and (recycled) fats is estimated to be more than 160 million metric tonnes [1,2]. It was possible to achieve a high OA conversion in combination with a good selectivity to branched-chain unsaturated fatty acids (BUFA) [3,11,12] These BUFA are the intermediates to the formation of BSFA. FER is synthesized by hydrothermal synthesis using appropriate silicon and aluminum sources and small structure directing agents (SDAs) in the form of organic molecules such as ethylenediamine [14] or pyrrolidine [15] Another approach is to prepare ferrierite using zeolite Y (FAU) as a source of silicon and aluminum. Addition of C16dMImz in the initial gel resulted in mesoporous ferrierite (Vmeso 0.09−0.28 cm g−1) with high crystallinity and different morphologies depending on the concentration of C16dMImz. Optimized hierarchically porous FER zeolite with strong Brønsted acidity displayed improved properties in the isomerization of fatty acids compared to microporous FER zeolite
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