Loading behavior of p-toluenesulfonic acid in biochar and its application to prepare 5-hydroxymethylfurfural

Abstract

A carbon-based solid acid catalyst was prepared from papermaking sludge via calcining followed by sulfonation with p-toluenesulfonic acid. The micromorphology of several catalysts were compared via SEM, FT-IR, N2 adsorption-desorption, XPS, and UV spectrum. It was found that the micromorphologies of biochar surface modified with concentrated H2SO4, p-toluenesulfonic acid, and sulfanilic acid were different and closely related to the binding mechanism. The biochar and p-toluenesulfonic acid exhibited π-π* stacking and hydrophobic effects. The suitable pores and gaps on the biochar surface were the key to the loading of p-toluenesulfonic acid. However, no π-π* stacking and hydrophobic effects were observed between the biochar and sulfanilic acid. The amidation grafting of sulfanilic acid to the biochar surface could lift the restriction of surface pore structure. The catalytic performance of these catalysts was evaluated via fructose, glucose, and cellulose degradation to 5-hydroxymethylfurfural (HMF). The HMF yield from fructose, glucose, and cellulose was 92.9%, 60.7%, and 28.6%, respectively, with the carbon-based solid acid catalyst. The carbon-based solid acid catalyst prepared from papermaking sludge and p-toluenesulfonic acid has the following advantages: a simple process, is environmentally friendly, and has good catalytic performance; as such, it has the prospect of industrialization.