Abstract
The selective production of p-xylene and other aromatics starting from sugars and bioderived ethylene offers great promise and can eliminate the need for separation of xylene isomers, as well as decreasing dependency on fossil resources and CO2 emissions. Although the reaction is known, the microporosity of traditional commercial zeolites appears to be a limiting factor. In this work, we demonstrate for the first time that simply desilication of microporous commercial zeolites by a simple NaOH treatment can greatly enhance conversion and selectivity. The [4 + 2] Diels–Alder cycloaddition of 2,5-dimethylfuran with ethylene in a pressurised reactor was investigated using a series of H-ZSM-5 catalysts with SiO2/Al2O3 ratios 30 and 80 with increasing pore size induced by desilication. X-ray diffraction, scanning electron microscopy, 27Al magic-angle spinning nuclear magnetic resonance, temperature programmed desorption of ammonia, and nitrogen physisorption measurements were used to characterise the catalysts. The enhancement of conversion was observed for all desilicated samples compared to the untreated zeolite, and increases in temperature and ethylene pressure significantly improved both dimethylfuran conversion and selectivity to p-xylene due to the easier desorption from the zeolite’s surface and the augmented cycloaddition rate, respectively. A compromise between acidity and mesoporosity was found to be the key to enhancing the activity and maximising the selectivity in the production of p-xylene from 2,5-dimethylfuran.
Highlights
Due to diminishing quantities of fossil fuels, lignocellulosic biomass is attracting more attention as a feedstock for platform chemicals due to its large availability and economic factors [1]. One of these platform chemicals obtainable from biomass is p-xylene [2,3], a precursor in the terephthalic acid synthesis, which can be polymerised to produce polyethylene terephthalate (PET). p-Xylene is currently produced on an industrial scale from the catalytic reforming of petroleum naphtha, which is part of the benzene-toluene-xylene (BTX) fraction
We investigate the effect of increasing the pore size of ZSM-5 catalysts with differing SiO2/Al2O3 ratios by alkaline treatment and how this affects the structural catalysts with differing SiO2 /Al2 O3 ratios by alkaline treatment and how this affects the structural properties of the ZSM-5, as well as how beneficial this can be for the production of renewable properties of the ZSM-5, as well as how beneficial this can be for the production of renewable aromatics aromatics p-xylene
We have demonstrated that alkaline treatment of H-ZSM-5 is beneficial for the [4 + 2] Diels–Alder cycloaddition of DMF and ethylene when compared to the untreated parent
Summary
Due to diminishing quantities of fossil fuels, lignocellulosic biomass is attracting more attention as a feedstock for platform chemicals due to its large availability and economic factors [1]. One of these platform chemicals obtainable from biomass is p-xylene [2,3], a precursor in the terephthalic acid synthesis, which can be polymerised to produce polyethylene terephthalate (PET). Recent studies have shown that 2,5-dimethylfuran (DMF) could act as a potential feedstock for the production of p-xylene [6,7,8,9,10]. The advantage of this route is the production of the pure para isomer of xylene, removing the necessity of purifying p-xylene, as is the case in its production from
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