AIST develop a continuous flow process for the production of vanillin: Efficiency improved 17 times and waste cut in half

Researcher Tomohiro Ichitsuka, Leader Takayuki Ishizaka of the Continuous Synthesis Systems Engineering Group, and Leader Takashi Makino of the Chemical Reaction System Design Group at the Research Institute for Chemical Process Technology, National Institute of Advanced Industrial Science and Technology (AIST), announced that they have developed a multi-stage extraction and separation system, which is the key to establishing a production flow process that enables a continuous reaction, extraction, and separation; they have also demonstrated highly efficient and low-environmental-impact continuous production of functional chemicals. A continuous flow process for vanillin, a flavor component, was operated at the scale of a few grams per hour, demonstrating a 17-times increase in production efficiency and a 50% reduction in waste compared with the conventional batch method, which is expected to contribute to sustainable industrial production. The results were published in the October 30 issue of ACS Sustainable Chemistry & Engineering.

Pharmaceuticals and other high-value-added chemicals are called functional chemicals, and many are produced in a complex, multi-step process using the batch method, a step-by-step production method. The method is challenging due to the high environmental impact associated with waste disposal.

In contrast, the flow method is a production method in which raw materials are continuously fed into the production equipment and products are continuously collected from the outlet, resulting in a higher efficiency and waste reduction compared with those achieved by the batch method.

AIST has been operating the Flow Science & Technology Consortium (FlowST) since 2015 to promote innovation in the manufacturing process of functional chemicals through industry−government−academia collaboration. The development of basic technologies has been promoted.

This time, the focus was on extraction and separation, which are essential for producing functional chemicals. A highly efficient continuous extraction−separation system was developed that integrates extraction and separation, essential for the continuous synthesis of functional chemicals with complex chemical structures, into the flow process, allowing continuous processing in a very short time with a minimum quantity of solvent.

Specifically, a high-speed extraction−separation system using slug flow (a flow pattern in which two immiscible fluids flow alternately in a channel) was efficiently developed in multiple stages to achieve continuous extraction and separation in approximately 3 min. using a minimum amount of solvent. When used in conjunction with a flow reaction system, unreacted raw materials and extracted solvents can be recirculated for continuous target synthesis. A continuous production flow process for vanillin was demonstrated using the developed system.

The system represents a continuous production flow process consisting of four steps (first: aromatic electrophilic substitution reaction, second: purification of intermediates, third: oxidative decarboxylation reaction, and fourth: purification of vanillin), where the first and third steps are flow reaction processes, and the second and fourth steps are multistage continuous extraction processes.

With the new system, vanillin is produced continuously by continuously feeding the initial raw materials. Production efficiency was greatly improved over that of the conventional batch method, demonstrating that high-purity vanillin can be continuously produced at an overall yield of 71% and at a rate of several grams per hour. Compared with those of the batch method, the production efficiency is more than 17 times higher, and the amount of waste is reduced by approximately 50%.

Ichitsuka said, "In the development of functional chemicals, the reaction to create molecules plays the leading role, and extraction-separation has a supporting role. The key to the success of this study was to emphasize this supporting role. The excellent role of the multi-stage continuous extraction−separation system allowed the main component to be prominent, resulting in a significant improvement in production efficiency and waste reduction. In addition, because of its supporting role, it has a wide range of functions and can be combined with a variety of reactions. We plan to increase the number of demonstration cases to show continuous production."