Acid Modified H-USY Zeolite for Efficient Catalytic Transformation of Fructose to 5-Hydroxymethyl Furfural (Biofuel Precursor) in Methyl Isobutyl Ketone–Water Biphasic System

Sustainable process and efficient heterogeneous acid catalyst for the preparation of platform chemicals like 5-hydroxymethyl furfural (5-HMF) from renewable source is much in demand in the context of heterogeneous catalysis. Commercially available solid acid catalyst, H-USY zeolite was modified by treating with aqueous solution of H3PO4 and H2SO4 (10–30 wt %). Modified H-USY was completely characterized by XRD, NH3-TPD, energy dispersive analysis X-ray (EDAX), FT-IR, pyridine-IR, and NMR. Its catalytic performance was evaluated for the fructose conversion to 5-HMF in methyl isobutyl ketone (MIBK)–water system. Modified H-USY zeolite was identified to have potential in enhancement of 5-HMF yield up to 65% from 32% (parent H-USY) with minimum formation of furfural (8%). H-USY modified with 10 wt % H3PO4 (10P–Y) was found to be the best compared to other studied catalysts, namely, H-USY modified with 20 and 30 wt % H3PO4 (20 and 30P–Y) or 10–30 wt % H2SO4 (10- to 30S–Y). Best performance of 10P–Y is associated with the optimum combination of moderate acidity (both weak as well as strong), moderate dealumination of Al from extra-framework sites as well as from framework sites of H-USY, formation of new Al–O–P bonds between framework Al and elemental monomeric phosphorus, presence of Brønsted as well as Lewis acidity, and creation of mesopores. This gives new insight on a potential heterogeneous acid catalyst for the synthesis of 5-HMF.