Intramolecular Catalysis in Carboxylic Acid Esterification: Modeling of Single- and Multi-Acid Esterification

Abstract

Downstream processing in the biorefinery is often faced with multicomponent process streams containing carboxylic acids and alcohols. Isolation of carboxylic acids may be simplified by direct esterification with the alcohol present in the process stream. However, uncatalyzed esterification is generally slow at moderate temperature. In multicomponent mixtures, though, stronger carboxylic acids act as catalysts for the esterification of weaker carboxylic acids. Single-acid esterification of formic acid, acetic acid, and propionic acid with methanol were investigated, and a kinetic model was developed considering the intramolecular catalytic effect through acid dissociation. With the kinetic constants derived from single-acid esterification, ester formation in multi-acid esterification was predicted and verified experimentally with a maximum sum of mean square error of 8.70 × 10–4. In multi-acid esterification, the catalytic influence of formic acid on acetic acid and propionic acid esterification was shown. Due to higher equilibrium constants transesterification of methyl formate to methyl acetate and methyl propionate, respectively, is observed and predicted by the model.

Side Products in the Water-Tolerant Synthesis of Poly(oxymethylene) Dimethyl Ethers: Formation Kinetics and Implications for Process Design

“…The experimental results (see below) revealed that reaction is very fast and can be assumed to be at chemical equilibrium under the given conditions. This finding is consistent with literature. − The chemical equilibrium is modeled using mole-fraction-based chemical equilibrium constants …”

Chemically Laminating Graphene Oxide Nanosheets with Phenolic Nanomeshes for Robust Membranes with Fast Desalination

“…GO and phenolic nanomeshes can interact by strong noncovalent forces including hydrogen bonds, amphiphilic interactions, and π–π interactions. , Importantly, H 2 SO 4 treatment can induce chemical reactions between GO and phenolic nanomeshes (Figure a,b). The carboxyl groups of GO can react with the hydroxyl groups of phenolic nanomeshes to form ester groups. , Moreover, neighboring phenolic nanomeshes can join together by forming methylene bridges between benzene rings . Therefore, the ester-bonded GO-phenolic nanomesh and methylene-bonded phenolic nanomesh-phenolic nanomesh lead to a covalently jointed structure of the hybrid membranes, in which GO nanosheets are in situ stabilized.…”

“…The carboxyl groups of GO can react with the hydroxyl groups of phenolic nanomeshes to form ester groups. 33,34 Moreover, neighboring phenolic nanomeshes can join together by forming methylene bridges between benzene rings. 35 Therefore, the ester-bonded GO-phenolic nanomesh and methylene-bonded phenolic nanomesh-phenolic nanomesh lead to a covalently jointed structure of the hybrid membranes, in which GO nanosheets are in situ stabilized.…”

Irreversible Bildung von Nebenprodukten bei der Synthese von Poly(oxymethylen)dimethylethern

“…Es wird zwischen zwei Arten von Reaktionen unterschieden, die im Modell differenziert behandelt werden: zum einen schnelle Gleichgewichtsreaktionen, von denen angenommen wird, dass sie sich immer im Gleichgewicht befinden, und zum anderen langsamere kinetisch kontrollierte Reaktionen, die aber auch das chemische Gleichgewicht erreichen können. Die Ersteren sind die Reaktionen (1)–(4) 13 und die Veresterungsreaktion (11) von Ameisensäure zu Methylformiat 31, 32. Das chemische Gleichgewicht wird nach Gl.…”