Reusable Heterogeneous Tungstophosphoric Acid-Derived Catalyst for Green Esterification of Carboxylic Acids

Abstract

Solid acid catalysts are environmentally friendly alternatives to the use of mineral acids in a range of applications, including the esterification of carboxylic acids. Here, a phosphorus-and nitrogen-doped, carbon-modified, fully heterogeneous solid acid catalyst was prepared by pyrolysis of a mixture of melamine and tungstophosphoric acid at 250, 500, and 750 °C under a nitrogen atmosphere provided. The structure of the different catalysts was evaluated by surface area measurements, XRD, XPS, Raman spectroscopy, elemental analysis, and electron microscopies. Pyrolysis at 500 °C created complex solid materials with larger surface area and significantly higher acidity, which can be attributed to WO 3 formation on a heteroatomic (N,P)-carbon structure. The 500 °C-treated heterogeneous catalysts showed remarkably better activity for esterification of palmitic acid and were thus applied in the esterification of a broad range of carboxylic acids with good overall yields. Furthermore, the solid acid catalyst can be easily recovered and recycled up to eight times without significant loss of activity with no leaching of species to the reaction mixture.

Tungstate-Catalyzed Bioinspired Decarboxylative Halogenation of Electron-Deficient (Hetero)Phenolic Acids

“…Protecting the carboxylic acids of 4-HBA would afford the methyl 4hydroxybenzoate (15). 45 Utilizing our previously reported approach, the bromination of 15 smoothly afforded methyl 3,5-dibromo-4-hydroxybenzoate ( 16) efficiently. After hydrolysis, the 2,6-dibromo-4-iodophenol (18) was obtained in excellent yield according to this decarboxylative iodination.…”

“…For example, the selective, sequential halogenation of 4-HBA was achieved in four steps. Protecting the carboxylic acids of 4-HBA would afford the methyl 4-hydroxybenzoate ( 15 ) . Utilizing our previously reported approach, the bromination of 15 smoothly afforded methyl 3,5-dibromo-4-hydroxybenzoate ( 16 ) efficiently.…”

Sulfonated and cross‐linked polystyrene ultrafine fibers for the esterification of palmitic acid for biodiesel production

“…Catalyst reuse is an important feature of heterogeneous catalyst because it can reduce the cost of production process. [42][43][44] For the sake of testing the reusability, we performed the PS-SA-SO 3 H catalyzed esterification of palmitic acid and methanol under optimized conditions (Table 3). After catalysis, the PS-SA-SO 3 H was readily recovered by simple filtration.…”

Homogeneous Catalysis and Heterogeneous Recycling: A Simple Zn(II) Catalyst for Green Fatty Acid Esterification

“…Among renewable resources, fatty acids (FAs) from vegetable oils occupy a relevant position due to their similarity to the aliphatic fractions of fossil materials. , For a full application of the principles of the circular economy, it is necessary that the vegetable raw material comes from waste or nonfood oils, a condition that creates a virtuous route for the sustainable production of many commodities . In fact, fatty acids are chemically versatile, thanks to the presence of the carboxylic group, suitable for esterification and transesterification reactions to obtain biodiesel − and other esters for industrial applications . The presence of one or more unsaturation is instead generally exploited in oxidative processes, such as epoxidation, dihydroxylation, and CC cleavage. − …”