Valorization of bioglycerol to value added products: Sulfonated mesoporous Polydivinylbenzene (PDVB) as an efficient solid acid catalyst for room temperature synthesis of solketal
Acetalization of glycerol with acetone is very significant reaction
for synthesis of solketal (2, 2-dimethyl-4- hydroxymethyl-1,
3-dioxolane). Solketal can be used as an additive in formulation
of diesel, biodiesel and gasoline fuels. It decreases the viscosity,
improves cold properties and provides the required flash point to
the biodiesel. These oxygenated products when blended with the
diesel fuel curtail the uncontrolled emission of carbon monoxide,
particles, hydrocarbons and aldehydes. Challenge in the synthesis
of glycerol derivatives is the formation of by-product water which
hinders the catalytic activity in case of silica due to low hydrothermal
stability and commercial resins being too hydrophilic. Moreover,
the commercial resins are not characterized by well-defined pores.
Diffusion limitation and polymer swelling remain as disadvantage
despite the development of large-pore resins, low-swelling polymers.
In this work, sulfonic acid functionalized mesoporous polymer
catalyst (MP-SO3H) was prepared by post synthetic modification of
mesoporous polydivinylbenene by incorporating sulfonic acid moiety
using conc. H2SO4. The synthesized materials were characterized
by using several physicochemical techniques and their performance
was evaluated for room temperature liquid phase acetalization of
glycerol with acetone. MP-SO3H catalyst performed better than other
conventional solid acid catalysts with 94 % glycerol conversion and
98.5 % selectivity for solketal. The high activity of MP-SO3H catalyst
can be attributed due to facile diffusion of reactants and products in
the mesoporous environment together with an optimized balance of
acid functionalization. Glycerol conversion increased with increase in
the total acidity of the catalyst. Amount of acidity and surface density
of (H+) ions were found to have a direct correlation with catalyst
performance.
