A novel purification process for dodecanedioic acid by molecular distillation

Efficient crystallization process of dodecanedioic acid by a pneumatically agitated crystallizer

Dodecanedioic acid (DC12) is mainly prepared via microbial synthesis in industrial production, however, the refined products have many drawbacks, such as low purity, poor crystal size distribution (CSD), and heavily agglomerated character, to name a few. Therefore, the refining process is a crucial step in DC12 preparation by microbial production. In this study, a novel pneumatically agitated crystallizer for DC12 refinery by gassing crystallization was developed. A batch cooling crystallization process was developed, providing the final crystal in 82.0% yield and purity increment to 99.20% at the end of crystallization process. Optimized conditions were determined as the initial supersaturation ratio of 300:3000 (g/mL) and gassing air flow rate of 4 L/min with solution preparation temperature of 85 °C. The crystal products with significantly better morphology characteristics than the starting crude feedstocks, including crystal uniformity and color brightness, were harvested. These obtained results indicated that the pneumatically agitated crystallizer-based crystallization process without any mechanical agitation was a robust and economically feasible technique. To our knowledge, this is also the first DC12 crystallization process with sole gassing agitation for unseeded batch cooling crystallization.

Recovery of acid corn oil from the bioalcohol industry by molecular distillation

BACKGROUND

The objective of this work was to reduce the acidity of acid corn oil for its subsequent use as edible oil. Also, its tocopherols composition was determined. This oil is obtained as a by-product of corn alcohol production on an industrial scale and is currently used as a raw material in the biodiesel industry.

RESULTS

The tocopherols and fatty acids composition of acid corn oil was determined by gas chromatography, and molecular distillation experiments were carried out at different temperatures between 110 °C and 190 °C with a volumetric flow rate of 0.5 to 2 mL min^-1 and a pressure of 5 × 10^-5  atm. It was possible to reduce its acidity from 9.44% (as oleic acid) to values less than 0.3% in the residue, with distillation temperatures higher than 180 °C; also, in the distillate, the tocopherols were recovered with concentrations up to 13 360 ppm.

CONCLUSION

It was possible to decrease the acidity and purify tocopherols from acid corn oil by molecular distillation, obtaining a residue with an acidity acceptable for human consumption and a distillate with a high tocopherols content. Therefore, using molecular distillation, added value was given to a by-product of the bioalcohol industry. © 2019 Society of Chemical Industry.

Highly concentrated omega-3 fatty acid ethyl esters by urea complexation and molecular distillation

BACKGROUND

Raya liver deodorized oil contains high concentrations of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). The present study investigated the processes of urea complexation (UC) and molecular distillation (MD) to determine the most adequate operation conditions for each process, separately and together, aiming to obtain highly concentrated EPA, DPA and DHA ethyl esters with chemical indicator values permitted by the current legislation for edible oils.

RESULTS

In the second stage of MD, a concentration of 820.27 g kg^-1 in the distillate and 951.06 g kg^-1 of omega-3 fatty acid ethyl esters in the residue was obtained. The distillate showed values of free fatty acids, peroxide and p-anisidine lower than the maximum allowed for edible oils in accordance with the current legislation.

CONCLUSION

The use of UC and MD together has revealed a significant improvement in the total concentration of omega-3 fatty acid ethyl esters in the final product and good application prospects. © 2018 Society of Chemical Industry.

Improving α, ω-dodecanedioic acid productivity from n-dodecane and hydrolysate of Candida cells by membrane integrated repeated batch fermentation

The aim of the present study is to develop an effective production process for α, ω-dodecanedioic acid (DC₁₂) biosynthesis using n-dodecane and hydrolysate of Candida cells as substrates by membrane integrated repeated batch fermentation. Cells and n-dodecane were simultaneously recycled during the filtration of fermentation broth (FB) with a 150 kDa ceramic membrane under a cross-flow velocity of 4 m/s and a trans-membrane pressure of 0.2 MPa, and it was also revealed that the cells in the broth could alleviate the membrane fouling during the FB filtration. Moreover, the hydrolysate of the collected cells could be successfully used as a nitrogen source to replace 50% yeast extract for decreasing the DC₁₂ production cost. With repeated-batch culture in a membrane bioreactor, the maximal DC₁₂ productivity could be enhanced by 57.8% compared with the batch culture, meanwhile n-dodecane and cells could be recovered and used for the next fermentation cycle.

Simultaneous decolorization and deproteinization of α,ω-dodecanedioic acid fermentation broth by integrated ultrafiltration and adsorption treatments

α,ω-Dicarboxylic acids (DC) are versatile chemical intermediates with different chain length. For biosynthesis of DC, to obtain the highly pure product via crystallization, it is required to remove pigments and proteins in fermentation broth. However, a trade-off between decolorization/deproteinization ratio and DC recovery during the purification process was found, which impeded DC production by fermentation. When ultrafiltration (UF) was applied to treat α,ω-dodecanedioic acid (DC₁₂) broth, 93.4% of DC₁₂ recovery, 80.5% of decolorization ratio and 61.7% of deproteinization ratio were achieved by a PES 3 membrane. However, the membrane technology could not effectively retain the pigments or proteins with low molecular weight when a high DC₁₂ permeation was required. Meanwhile, the selected activated charcoal or macroporous resins were not good adsorbents for the present system. Furthermore, an integrated process for decolorization and deproteinization was developed. After filtration with PES3 membrane, an activated charcoal was used to remove the small proteins and pigments in the UF permeate. As a result, 91.4% of DC₁₂ recovery, 94.7% of decolorization ratio and 84.8% of deproteinization ratio were obtained by such two-stage strategy. These results would serve as a valuable guide for process design and practical operation in subsequent industrial application.

Role of oxygen supply in α, ω-dodecanedioic acid biosynthesis from n-dodecane by Candida viswanathii ipe-1: Effect of stirring speed and aeration

α, ω-Dodecanedioic acid (DC₁₂) usually serves as a monomer of polyamides or some special nylons. During the biosynthesis, oxygenation cascaded in conversion of hydrophobic n-dodecane to DC₁₂, while the oxidation of n-dodecane took place in the intracellular space. Therefore, it was important to investigate the role of oxygen supply on the cell growth and DC₁₂ biosynthesis. It was found that stirring speed and aeration influenced the dissolved oxygen (DO) concentration which in turn affected cell growth as well as DC₁₂ biosynthesis. However, the effect of culture redox potential (Orp) level on DC₁₂ biosynthesis was more significant than that of DO level. For DC₁₂ biosynthesis, the first step was to form the emulsion droplets through the interaction of n-dodecane and the cell. When the stirring speed was enhanced, slits in the surface layer of the emulsion droplets would be increased. Thus, the substances transportation by water through the slits would be intensified, leading to an enhanced DC₁₂ production. Compared with the batch culture at a lower stirring speed (400 rpm) without culture redox potential (Orp) control, the DC₁₂ concentration was increased by 5 times up to 201.3 g/L with Orp controlled above 0 mV at a higher stirring speed (800 rpm).

Methodology for predicting oily mixture properties in the mathematical modeling of molecular distillation

A methodology for predicting the thermodynamic and transport properties of a multi-component oily mixture, in which the different mixture components are grouped into a small number of pseudo components is shown. This prediction of properties is used in the mathematical modeling of molecular distillation, which consists of a system of differential equations in partial derivatives, according to the principles of the Transport Phenomena and is solved by an implicit finite difference method using a computer code. The mathematical model was validated with experimental data, specifically the molecular distillation of a deodorizer distillate (DD) of sunflower oil. The results obtained were satisfactory, with errors less than 10% with respect to the experimental data in a temperature range in which it is possible to apply the proposed method.