Solventless transacetalization of solketal over Amberlyst catalysts into valuable bio-based chemicals

BACKGROUND: In addition to being a greener synthetic approach, the production of value-added chemicals from bio-based glycerol is highly appealing owing to its nontoxicity, renewability and availability. The current work reports solventless transacetalization of solketal with benzaldehyde in the presence of heterogeneous Amberlyst (R) catalysts (A15 dry, A15 wet, A36 and A46). RESULTS: Effects of several reaction parameters on the transacetalization of solketal also were investigated and optimized to attain maximum conversion and yield. This reaction, however, is accompanied by concurrent hydrolysis of solketal to form the side product glycerol. Of all solid acid catalysts investigated, A15 dry (10 wt%) gave the highest conversion (88%) under optimized reaction conditions of 60 degrees C, 5:1 (solketal/benzaldehyde) and 30 min duration. The A15 dry is reusable and recyclable with only 8% reduction in conversion after five consecutive cycles. The approach was extended to other aldehydes including furfural and phenylacetaldehyde to produce, respectively, a highly value-added fuel additive intermediate and hyacinth fragrance. CONCLUSION: The transacetalization of solketal with less reactive aldehyde into cyclic glycerol acetal was achieved in an efficient, feasible and green manner. A15 was the most reactive catalyst of all Amberlyst (R) catalysts investigated. This approach also provided effective utilization of waste of biodiesel production - glycerol - for transformation into value-added products. (C) 2021 Society of Chemical Industry (SCI).