Enhanced acidity of MOF-808 by defect-engineered and supported-sulfuric acid in ketalization of glycerol

In this work, (metal- organic framework) MOF-808, defective MOF-808 (DF), sulfonated MOF-808 (MOF-808-SO4), and defective/sulfonated MOF-808 (MOF-808-SO4 (DF)) were synthesized, modified and assessed as catalysts for the conversion of glycerol to solketal for use as a bio-additive to fuel. We also report that zirconium-based MOF-808 (Zr) with partial defects can be fabricated using isophthalic acid ligands to improve the properties of catalysis. The characterization results confirm that MOF-808-SO4 (DF) had more acidic properties than the parent MOF-808 and MOF-808 (DF). Amongst the catalysts assessed, MOF-808-SO4 (DF) recorded the maximum conversion (about 78 % after 30 min) and selectivity (about 98 %) towards solketal. Two mechanisms have been discussed based on the kinds of acidity. In a simple recycling process, after four repetitions of catalytic reaction using the same catalyst sample was reused without any loss of activity. The correlation between the acidic properties of the catalysts and selectivity of the solketal was investigated. The correlation between the acidic properties of the catalysts and the selectivity of the solketal was investigated.