Enhanced Lewis acidity on modified H-ZSM-5 catalysed 5-hydroxymethylfurfural oxidation in aqueous solvent

The primary focus of the present study is to develop a zeolite-based catalyst that enhances Lewis acidity for catalysing 5-hydroxymethylfurfural (HMF) oxidation. The study modifies the parent H-ZSM-5 (H-Z) via desilication followed by Ru impregnation. The results show that RuZS₉₀ (Ru impregnated on desilicated H-Z for 90 min) exhibits higher catalytic activity for the HMF oxidation than Ru impregnated on parent H-Z. NH₃-temperature programmed desorption (TPD) results indicate that RuZS₉₀ possesses more than 2.6 and 2.3 times higher total acidity than H-Z and RuH-Z, contributing to the higher catalytic activity. A poisoning study with potassium thiocyanate (KSCN), which passivates Lewis acidic sites, suggests that RuZS₉₀ yields no considerable oxidised furanic products, confirming the crucial role of Lewis acidic sites. The NH₃-DRIFT study further corroborates that RuZS₉₀ contains more enhanced Lewis acidic sites than the parent H-Z, playing a vital role in the oxidation of HMF.