Alternative Way to Generate DPC Monomers for PC Production
The conventional PC production process is interfacial polymerization. By using this process, bisphenol-A and phosgene are polymerized in two phases, i.e. organic and aqueous phase. In 2015, Asahi Kasei started building a pilot plant at the Mizushima site, in order to test the newly developed production process for DPC diphenyl carbonate using dialkyl carbonate (DRC). According to the company, they have been successful, not only in reducing energy consumption by applying CO2 as a safe raw material, dispensing with phosgene. What is more, CO2 emissions were diminished, as well.
In a joint project with „New Energy and Industrial Technology Development Organization“ (NEDO) of Japan, plastics producers Asahi Kasei Corp. in Kurashiki, Okayama, Japan developed and tested a new process to generate diphenyl carbonate (DPC). DPC is a type of monomer that is used at the company’s site in Mizushima (Kurashiki, Okayama, Japan). Together with dialkyl carbonate (DRC), the monomer serves for polycarbonate (PC) production.
The process proved to be reliable and feasible in more than 1000 hours of continuous operation, according to supplier information. The company says that the newly developed process reduces energy consumption and CO2 emissions if compared to the conventional process. At the same time, CO2 as a safe raw material, is applied.
Data and Facts of the Pilot Plant
- Project period: business years 2014–2016
- DPC capacity: 1,000 tonnes/year
- Site: Asahi Kasei Corp., Mizushima site (near the city of Kurashiki, located in Okayama prefecture, Japan)
The pilot plant is part of the NEDO project, of the program for strategic and innovative technologies of energy saving (2014–2016) and of the effort to develop a process to produce chemicals by using CO2 .
Asahi Kasei is constantly working to improve economics and energy efficiency, most of all by focusing on commercialization: They use this strategy in order to develop a technology for reliable production, by optimizing operating conditions and production facilities. Evaluation of the new process is due to further step up the licensing business, which Asahi Kasei had developed along with its new PC production process without phosgene (i.e. PC production using DPC instead of phosgene, melt polymerization of bisphenol-A and DPC). Globally, this licensing business is used by enterprises in China, Korea, Taiwan, Russia and Saudi-Arabia, for example.
Findings, Data and Facts on the Process
The DRC process for DPC applies a method that includes the development of catalysts with a high catalytic activity and stability. The catalysts served to produce DRC from CO2 and alcohol, and, in a following step, produce DPC from DRC and phenol. Asahi Kasei states that they evaluated in continuous operation the feasibility of the DRC process for DPC production. This was done to evaluate the catalyst cycle as well as the catalytic performance for both steps, i.e. for the DRC step (producing DRC out of CO2 and alcohol) and for the DPC step (generating DPC out of DRC and phenol). Likewise, they evaluated reactor performance as well as the system applied to recycle the non-reacted raw materials.