A metallosurfactant catalyst was developed to address the requirements for the utilization of low-molecular-weight carboxylic acids from dilute effluents. The catalyst Ni­(DBSA)2 combines transition-metal catalysis of nickel ions and surfactant catalysis of 4-dodecylbenzenesulfonic acid (4-DBSA). Requirements for the metallosurfactant catalyst are low water solubility, high catalytic activity in biphasic esterification, and self-assembling properties at the interface. Ni­(DBSA)2 was tested for applicability in the interfacial catalysis of esterification of dilute acetic acid with the solvent 1-octanol and resulted in an octyl acetate yield of 31.3%. Under identical reaction conditions, Ni­(DBSA)2 performed better than sulfuric acid with a yield of 1.7%. The limited catalytic performance of sulfuric acid is caused by the presence of sulfuric acid mainly in the aqueous phase. In contrast, Ni­(DBSA)2 is dissolved in the solvent and assembles at the aqueous/solvent interface where the reaction takes place. Additionally, the metallosurfactant lowers the interfacial tension between 1-octanol and deionized water by up to 75%, thus enhancing mass transfer. Compared to catalysis with 4-DBSA in emulsion, the catalytic performance of Ni­(DBSA)2 dropped by 62%, but this drawback is compensated by the complete suppression of emulsification. With Ni­(DBSA)2, the development of a catalyst was achieved, which self-enhances its catalytic performance in the interfacial catalysis through increased mass transfer area due to its surfactant properties.

Isolation of low concentrated constituents from side streams of biobased processes has recently received increased technical and economical attention. For energy efficient acid isolation reactive extraction is proposed in literature. The crucial step for efficient process application is the solvent regeneration. Alternatively to conventional reactive extraction, physical extraction with chemical conversion simplifies the technical demand. For continuous operation of heterogeneous catalyzed esterification with physical extraction the Taylor‐Couette disc contactor has proven to be applicable.

A concept for isolation of dilute low molecular weight carboxylic acids, based on surfactant-catalyst enhanced esterification, is proposed.

Emulsion‐enhanced biphasic esterification has proven to be applicable for carboxylic acid recovery from dilute aqueous process streams. The carboxylic acid is esterified with 1‐octanol in an emulsified regime with 4‐dodecylbenzenesulfonic acid (4‐DBSA) or Ni(DBSA)2 as catalyst. After phase separation, the laden solvent phase must be regenerated. This study presents a regeneration concept based on reactive distillation with transesterification of the octyl ester‐laden solvent with methanol. The regenerated solvent is reused in the extraction step.