Search

Atom economical and safe epoxidations of a variety of fatty acid methyl esters (FAMEs, including methyl oleate, methyl linolenate, methyl linoleate, and methyl soyate) under near-isothermal conditions are demonstrated using a tungsten-based Venturello catalyst and H2O2 as an oxidant under solvent-free conditions. By systematically optimizing the substrate/catalyst ratio, stirring rate, H2O2 addition rate, and external cooling rate, safe operation with minimal temperature rise was demonstrated in a semibatch reactor for each of the substrates with total selectivity toward the epoxides at complete conversion. In the case of methyl oleate epoxidation, which produces only one epoxide as product, intrinsic conversion/selectivity data obtained under near-isothermal (±0.1 °C) conditions were regressed with suitable kinetic and reactor models to obtain an activation energy of 85 ± 6.8 kJ/mol. These results provide valuable guidance for the rational design, scaleup, and safe operation of FAME epoxidation reactors.

2,5-Furandicarboxylic acid (FDCA) is a valuable nonphthalate biomass-based plastic precursor with the potential to replace terephthalic acid (TPA) in a variety of polymer applications. In this work, the Co/Mn/Br-catalyzed semicontinuous oxidation of 5-hydroxymethylfurfural (HMF) to FDCA has been demonstrated at temperatures lower than those employed in the traditional Mid-Century (MC) process. As HMF is more susceptible to side reactions (e.g., the overoxidation to CO and CO2), lower temperatures compared to the MC process are typically used to prevent substrate burning. However, lower temperatures afford a much reduced FDCA yield compared to that of TPA in p-xylene oxidation. Therefore, optimization of other operating variables such as catalyst composition, water concentration in the acetic acid solvent, and pressure is essential to maximize FDCA yield. Using such optimization, we show that the FDCA yield can be enhanced to 90% at a 1/0.015/0.5 molar ratio of Co, Mn, and Br, 7% (v/v) water, 30 bar (CO2/O...

We have shown that liquid CO2 dissolves O3 in higher concentrations compared to conventional solvents and is therefore an effective medium for the ozonolysis of unsaturated compounds. The Beer–Lambert law extinction coefficient for ozone in liquid CO2 is determined to be 3.2 ± 0.3 M–1 cm–1. Further, the Henry’s law coefficient for ozone dissolution in dense phase CO2 is determined to be on the order of 0.25 mol L–1 bar–1 in the temperature range −10 to +4 °C. Rapid ozonolysis of methyl oleate in liquid CO2 has been successfully demonstrated with the 1,2,4-trioxolanes (secondary ozonides) being the major stable product, as confirmed by NMR analysis. The product distribution is consistent with a lack of solvent cage effects due to the low polarity of liquid CO2. In addition to the inertness of liquid CO2 to ozone attack, the dominant presence of dense CO2 in the vapor phase promotes inherent process safety.

We demonstrate a continuous reactor for performing the ozonolysis of fatty acid methyl esters (FAMEs) using liquid CO2 as solvent. The fast reaction kinetics allows the use of small-volume reactors to completely convert the FAMEs, forming secondary ozonides as the primary products. The short residence times also help maximize the yields of the secondary ozonides by minimizing over-oxidation and the formation of oligomeric products. The liquid CO2 medium promotes safe reactor operation by providing an essential fraction of overall reactor cooling and by diluting the vapor phase organics. We also demonstrate a continuous stirred reactor for the safe thermal decomposition of the secondary ozonides to their corresponding acids and aldehydes. Using a lumped kinetic model for the thermal decomposition of the ozonolysis products, we estimate activation energy values of 108.6 +/- 0.6 kJ mol(-1) for the decomposition of secondary ozonides and 122 +/- 3 kJ mol(-1) for the decomposition of the undesired oligomeric species. (c) 2017 American Institute of Chemical Engineers AIChE J, 63: 2819-2826, 2017