Halloysite functionalized with dendritic moiety containing vitamin B1 hydrochloride as a bio-based catalyst for the synthesis of 5-hydroxymthylfurfural

Abstract

Using halloysite clay and vitamin B1 hydrochloride, a novel acidic halloysite-dendrimer catalytic composite has been developed for conversion of fructose to 5-hydroxymthylfurfural. To grow the dendritic moiety on halloysite, it was first functionalized and then reacted with melamine, epichlorohydrin and vitamin B1 hydrochloride respectively. Then, the resulting composite was treated with ZnCl₂ to furnish Lewis acid sites. Similarly, dendritic moiety of generation 2 was also grafted on halloysite and the activity of both catalysts for conversion of fructose to 5-hydroxymthylfurfural was investigated to disclose the role of dendrimer generation. For the best catalytic composite, the reaction variables were optimized via RSM and it was revealed that use of 0.035 g catalyst per 0.1 g fructose at 95°C furnished HMF in 96% yield in 105 min. Kinetic studies also underlined that Ea was 22.85 kJ/mol. The thermodynamic parameters of \({\varDelta \text{H}}^{\ne }\), \({\varDelta \text{S}}^{\ne }\) and \({\varDelta \text{G}}^{\ne }\), were calculated to be 23 kJ/mol, − 129.2 J/mol and 72.14 kJ/mol, respectively. Notably, the catalyst exhibited good recyclability and hot filtration approved heterogeneous nature of catalysis.