Advancing sustainable biofuel additive production via urea-carbonylated mannose over lanthanum triflate supported on aluminum oxide catalysts

Abstract

This study reports the successful synthesis of a lanthanum triflate-supported alumina (LT/Al₂O₃) catalyst for the production of mannose carbonate via the alcoholysis of urea and D-mannose. This bifunctional catalytic system enables a solvent-free, one-pot process at a moderate temperature (140 °C), achieving high yields of mannose carbonate (69–96%) with reduced side product formation compared to conventional methods. The catalyst demonstrated a synergistic effect between the strong Lewis acid sites of La³⁺ and the high surface area of the Al₂O₃ support, leading to enhanced catalytic performance relative to unsupported lanthanum triflate. A novel synthetic pathway was proposed based on compound identification by gas chromatography-mass spectrometry (GC–MS), using spectral matching with reference mass spectral libraries. Catalyst recyclability was evaluated over five consecutive reaction cycles, with the regenerated catalyst maintaining activity and achieving an 86.54% yield through the fourth cycle. Additionally, the gasoline-mannose carbonate blend exhibited a lower maximum exhaust temperature (430 °C) compared to commercial gasoline (470 °C), indicating improved thermal efficiency attributed to the blend’s reduced viscosity. The blend also demonstrated a superior cooling effect and was able to maintain the lubricant oil at 115 °C compared to 123 °C with commercial gasoline, further supporting its potential as an energy-efficient fuel additive.

Graphical abstract