One-pot synthesis of C8aldehydes/alcohols from propylene using eco-friendly hydrotalcite supported HRhCO(PPh3)3 catalyst

Abstract

A multi-functional catalyst [HF/HT] containing a rhodium complex, HRh(CO)(PPh₃)₃ [HF] and a solid base, hydrotalcite Mg_1−xAl_x(OH₂)^x+(CO₃²⁻)_x/n·mH₂O [HT], synthesized by impregnation of [HF] onto the surface of [HT], was investigated for the one-pot synthesis of C₈ aldol derivatives (aldehydes or alcohols) from propylene. The catalyst was found to be efficient to carry out hydroformylation, aldol condensation and hydrogenation reactions in one pot. The catalytic activity of [HF/HT(X)] was studied in detail as functions of Mg/Al molar ratio (X) of [HT], amount of [HF] complex and [HT], and reaction temperature. The selectivity for 2-ethylhexanal was observed to increase upon increasing X and amount of [HT]. The highest selectivity for 2-ethylhexanol was observed for [HT] Mg/Al molar ratio of 3.5 at 250 °C. The kinetic profiles of the various products obtained were in agreement with the reaction pathway proposed to understand the role of the [HF/HT] catalyst on the formation of C₈ aldol derivatives. Thermal stability of the [HF/HT] catalyst system was also investigated.