Vanadyl Phthalocyanine as a Low-Temperature/Low-Pressure Catalyst for the Conversion of Fructose to Methyl Levulinate.

Abstract

In this study, a vanadyl phthalocyanine was synthesized and characterized using XRD, FTIR, and XPS, confirming the successful metalation of the phthalocyanine ring. XRD analysis showed the vanadyl phthalocyanine crystallized in the P-1 crystal lattice, with unit cell parameters a = 12.058 Å, b = 12.598 Å, and c = 8.719 Å, and the lattice angels were 96.203°, 94.941°, and 68.204°. FTIR spectroscopy supported the metalation by the disappearance of the N-H stretch of the non-metalated phthalocyanine. The vanadyl phthalocyanine was tested as a heterogenous catalyst for the conversion of fructose into methyl levulinate in H₂SO₄-methanol and HCl-methanol systems. The H₂SO₄-methanol reaction system catalyzed with the vanadyl phthalocyanine, and a zeroth-order rate constant of 1.10 × 10^-6 M/s was observed, which was 1.74 times faster than sulfuric acid alone. The HCl-methanol system showed a zeroth-order of reaction with a rate constant of 2.33 × 10^-6 M/s, which was 1.3 times faster than the HCl-methanol alone. While the HCl-methanol system showed a faster reaction rate, product distribution favored methyl levulinate formation in the H₂SO₄-methanol system. The main products identified were methyl levulinate and hepta-2,4-dienoic acid methyl ester, with a minor amount of hydroxymethylfurfural formed. These results suggest that vanadyl phthalocyanine can be effectively used as a catalyst to increase the rate of fructose conversion to methyl levulinate in either H₂SO₄ or HCl-methanol.