A study of the oxidehydration of 1,2-propanediol to propanoic acid with bifunctional catalysts

Abstract

The gas-phase oxidehydration (ODH) of 1,2-propanediol to propionic acid has been studied as an intermediate step in the multi-step transformation of biosourced glycerol into methylmethacrylate. The reaction involves the dehydration of 1,2-propanediol into propionaldehyde, which occurs in the presence of acid active sites, and a second step of oxidation of the aldehyde to the carboxylic acid. The two reactions were carried out using a cascade strategy and multifunctional catalysts, made of W-Nb-O, W-V-O and W-Mo-V-O hexagonal tungsten bronzes, the same systems which are also active and selective in the ODH of glycerol into acrylic acid. Despite the similarities of reactions involved, the ODH of 1,2-propanediol turned out to be less selective than glycerol ODH, with best yield to propanoic acid no higher than 13%, mainly because of the parallel reaction of oxidative cleavage, occurring on the reactant itself, which led to the formation of C 1-C 2 compounds.

Continuous-Flow Methyl Methacrylate Synthesis over Gallium-Based Bifunctional Catalysts

“…The same patent also describes a variant of the same process where dimethoxymethane is used in place of FAL as a safer reactant. Other strategies toward biobased MMA involve its synthesis from itaconic acid and the synthesis of MP from a renewable building block such as the glycerol co-produced during biodiesel production, either through a multistep catalytic process , or by means of fermentation and esterification.…”

Continuous Flow Upgrading of Selected C2–C6Platform Chemicals Derived from Biomass

“…Cavani and colleagues reported up to 86% yield in propanal upon reacting an aqueous feed of 1,2-PDO in the presence of O 2 /N 2 as the carrier gas, over a catalytic bed of WNb oxides operated at 240 °C (Table 2, entry 5). 153 Vogel and coworkers alternatively evaluated the reaction in sub-and supercritical water and in the presence of a homogeneous catalyst. 150 ZnSO 4 (400 ppm) was loaded in the aqueous feed of 1,2-PDO, and the mixture was superheated for 1 min at 360 °C and 340 bar in a continuous flow reactor, affording 90% yield in 21.…”

“…156 Cavani and propanal and its subsequent oxidation toward propanoic acid. 153 Such catalysts are efficient for the analog one-pot dehydration of glycerol into acrolein, followed by its subsequent oxidation into acrylic acid (see Section 2.3.9). However, a maximum yield of only 13% in propanoic acid was obtained.…”

“…It is mainly produced at an industrial level from the hydroformylation of ethylene with CO and H 2 over rhodium catalysts and therefore relies on non-renewable fossil resources . Alternatively, 21 could be produced from the continuous flow catalyzed dehydration of propanediols. ,,− …”

“…With 1,2-PDO as the substrate, aqueous solutions were typically reacted in the gas-phase over solid acid catalysts loaded in fixed-bed reactors (Figure ). As propanal formed, it often reversibly reacted with the diol substrate to yield the ketal condensation product 22 and water. − Utilization of water as the solvent was thus appropriate to inhibit the formation of side-product 22 . , Representative catalysts and optimized conditions for the gas-phase dehydration of 1,2-PDO are reported in Table . Deactivation was often associated with strong acid sites that tend to trigger coking. , …”