Chemical Recycling Process Research Articles

Study on depolymerisation of poly(trimethylene terephthalate) in supercritical methanol by GPC-HPLC-IR

The degradation behaviour of poly(trimethylene terephthalate) (PTT) in supercritical methanol was investigated to develop a chemical recycling process for waste plastics. GPC and HPLC combined with FTIR spectrometry were applied to qualitative and quantitative analysis of products. DMT, MHPT, BHPT, MHET, BHET and HEHPT were found to be the main reaction products. The yields of monomer components are strongly consistent with the bond energy differences in the repeat unit. The detailed reaction process was discussed based on the experimental data. Further investigation indicates that the complex characteristic of supercritical fluids and impurities in raw materials can result complication in products.

Methanolysis investigation of commercially available polyurethane foam

Methanolysis investigation of a model polyurethane (PUR), poly[ethylene=methylene bis(4-phenylcarbamate)], and the commercially available PUR foam, Sofran ® is reported. The methanolysis conditions were in the temperature range from 160 to 300 °C and at pressures up to 15 MPa, partly in the supercritical state of methanol. For both the PURs the decomposition percentages are over 90% at temperatures above 200 °C. Methyl carbamate was formed in the reaction mixtures by the decomposition at all temperatures studied. With the GC measurement of the carbamate, it is revealed to be decomposed into methanol and 4,4′-methylenediphenyl diisocyanate (MDI). The decomposition temperature of the carbamate was determined to be 250 °C by TG–DTA measurement. The chemical recycling process flow on PUR compounds is proposed.

Chemical Recycling of Poly(ethylene terephthalate). 2. Preparation of Terephthalohydroxamic Acid and Terephthalohydrazide

A convenient one-pot−two-step process for chemical recycling of waste PET to produce terephthalohydroxamic acid (TPHA) and terephthalohydrazide (TPHD) was proposed. Decomposition of PET pellets to ...

Degradation kinetics of polyethylene terephthalate in supercritical methanol

AbstractDegradation of polyethylene terephthalate (PET) in supercritical methanol was investigated to develop a chemical recycling process for waste plastics. Continuous kinetics analysis was applied to the experimental data. A batch reactor was used at 573 K under the estimated pressure of 20 MPa for a reaction time of 2–120 min. PET decomposed to its monomers, dimethyl terephthalate (DMT), and ethylene glycol (EG), by methanolysis in supercritical methanol. PET with a weight‐average molecular weight of about 47,000 was converted to oligomer with that of 3,000 in 300 s and with that of 1,000 in 600 s. The largest yield of DMT was 80 mol % at 7,200 s and that of EG was 60 mol % at 3,600 s. Reaction products were analyzed with size exclusion chromatography, gas chromatography‐mass spectrometry, and reversed phase liquid chromatography. The molecular‐weight distribution (MWD) of the products was obtained as a function of reaction time. The yields of monomer components of the decomposition products, including byproducts, were measured. Continuous kinetics theory was developed to analyze the decomposition behavior. The theory includes MWD change of polymer by random and specific scissions and secondary reactions for monomer components. Change of MWD and monomers as a function of time was simulated by the continuous kinetics.

226 廃 PET ボトルのケミカルリサイクル技術

New PET chemical recycling process was developed and demonstrated in the 15kg/hr pilot testing, which can recover the terephthalic acid and ethylene glycol from post-consumer PET bottles. The developed process consists of aikaline depolymerization of PET to monomers and crystalization and purification of TPA. Through the pilot testing, it was confirmed that the recycled TPA can be used for food-container according to the FDA analysis evaluation and economical feasibility study of the commercial plant showed the competitiveness to conventional material recycling plants.

２１世紀の超臨界流体利用技術 超臨界水中での廃棄物のケミカルリサイクル

A new recycling process for wastes using supercritical water has been developed. The monomers obtained from supercritical water hydrolysis are the raw material of condensation polymers such as poly(ethylene telephthalate), polyurethane and so on. This process was applied to TDI (Tolylene Diisocyanate) distillation residue. By the process with super- or sub-critical water, TDA can be obtained from the residue comprising TDI oligomers. The plant for the commercial use of the chemical recycling process for TDI residue using supercritical water was constructed at the end of 1997, and is now functioning as an environmentally friendly plant.

Degradative extrusion as a pretreating process for chemical recycling of plastics waste

AbstractChemical conversion processes can also be used for the recycling of plastics waste. The plastics, however, must be adapted to chemical recycling processes by liquefaction and dehalogenation. A reprocessing method for plastics waste has been developed, which pretreats these waste fractions by degradative extrusion. The polymers are cracked in an extruder under the influence of thermal and mechanical energy and with the introduction of degradation‐promoting additives. Decomposition products such as halogens are eliminated and recovered in a defined manner through degassing and also a sufficient reduction of the melt viscosity was carried out by molecular degradation.

Integrated energy and media supply concepts for long-term space missions

In order to minimize the operational cost of future long-term manned space missions, an integrated regenerative energy and media supply system (EMSS) for spacecraft and Space Station is proposed. Based on H 2 O 2 - technology , the first step into a regenerative EMSS could be the integration of the subsystems energy supply, environmental control and life support (ECLS) as well as attitude and orbit control (AOC). Further extension of such a system may also comprise the nutrition system including then further elements as N 2 and C. Electrolyser and fuel cell systems play an important role within EMSS as energy converter while solar dynamic energy supply systems may offer thermal energy in parallel to electricity. Simultaneous availability of thermal and electric energy including adequate storage facilities will form an optimum basis to a variety of different chemical recycling processes as well as media and energy conversion. The motivation for such a technology is presented, the technical characteristics of subsystems technology are summarized and the first approaches of possible concepts are developed. Step by step solutions seem possible so that pilot test plants of low degree of integration may be investigated already in the course of the planned Space Station.

Polyol Recovery from Rigid Polyurethane Waste

Glycolysis of rigid polyurethane foams is an efficient process for chemical recycling of waste products into raw materials. Secondary reactions leading, to some extent, to formation of amines are also involved in the process. The choice of catalyst is an important factor in selecting the type of reaction as well as the reaction rate. The best results are obtained with dipropylene glycol and potassium acetate. Reaction rates are high and a simple and easy process leads straight to raw materials that can be used without further treatment for the production of rigid methane foams. The properties of the foams are at least comparable to those of foams obtained from fresh polyols.