Etsu Yamada

Alkali-catalyzed methanolysis of polycarbonate. A study on recycling of bisphenol A and dimethyl carbonate

Alkali-catalyzed methanolysis of poly[2,2-bis(4-hydroxyphenyl)propane carbonate] (PC) in a mixed solvent of methanol (MeOH) and toluene or dioxane was studied. Treatment of PC pellets (1.27 g) in 2 ml MeOH with a catalytic amount of NaOH (8.5 mol% per one ester unit of PC) at 60°C for 330 min yielded only 7% bisphenol A (BPA). However, in a mixed solvent of MeOH (1 ml) and toluene (1 ml), the analogous treatment for 70 min completely depolymerized PC to give free bisphenol A (96%) in a solid form and dimethyl carbonate (DMC) (100%) in solution. Characteristics of the catalysis are discussed together with the pseudo-first kinetic feature of the depolymerization. Reaction conditions were investigated for the purpose of recycling PC plastics in the form of bisphenol A and DMC.

Alkali decomposition of poly(ethylene terephthalate) with sodium hydroxide in nonaqueous ethylene glycol : A study on recycling of terephthalic acid and ethylene glycol

Pellets of poly(ethylene terephthalate) (PET; 0.48–1.92 g) were heated in anhydrous ethylene glycol (EG; 5 mL) with 2-equivs of NaOH at 150°C for 80 min or 180°C for 15 min to convert them quantitatively to disodium terephthalate (Na2-TPA) and EG. The disodium salt was precipitated quantitatively in pure state from the EG solution and separated readily. The other product EG, being the same component to the solvent, remains in the solution and can be obtained after distillation as a part of the solvent. The rate of decomposition was significantly accelerated by the addition of ethereal solvents to EG, such as dioxane, tetrahydrofuran, and dimethoxyethane. The reaction system is simple; no water and no extra reagent other than NaOH and EG are used. A few recycling systems of PET can be designed on the basis of the present alkali decomposition reaction.

Destruction of PCDDs and PCDFs. A convenient method using alkali-metal hydroxide in 1,3-dimethyl-2-imidazolidinone (DMI)

Abstract Complete and easy-to-use chemical destruction of PCDDs and PCDFs (10–12,000 ppb), which were extracted from urban incineration fly-ash, was achieved by employing an improved alkali-metal hydroxide method in a novel aprodc polar solvent DMI (1,3-dimethyl2-imidazolidinone), a commercially available highly inert solvent under strongly basic conditions. The destruction reagent can be easily prepared by dissolving 0.5 g NaOH or KOH in 10 cm 3 DMI, to which was added a hexane solution (1 cm 3 ) of PCDDs and PCDDs (initial concentration > 30 ppm) extracted from fly-ash (30 g). Warming the solution at 90°C for 0.5 h, in the absence or presence (5%) of water, realized the highly efficient destruction (>99.99%) of the hazardous organohalogen compounds.

Py-GC/MS analysis of sediments from Lake Biwa, Japan: characterization and sources of humic acids

Humic substances extracted and purified from bottom sediments of northern Lake Biwa, Japan, in November 2012 and 2013 were characterized using elemental analysis, Fourier-transform infrared spectroscopy, hydrogen-1 nuclear magnetic resonance (1H NMR) analysis, and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The infrared (IR) bands in the spectra of humic acids showed the presence of amide linkages and polysaccharides. Results of 1H NMR analysis showed that the humic acids contained approximately twice the number of aliphatic protons as those in the Japanese soil standards used for comparison. Results of the Py-GC/MS analysis, which evaluates pyrolysis temperature dependency of the amount of pyrolysis products, showed that the generation of pyrolysis products in humic acids also differed from that in Japanese soil standards but was similar to that of phytoplankton in Lake Biwa. This analysis method is the first to provide extensive information about the chemical structure of humic substances; conventional Py-GC/MS provides limited information for a single temperature. Data suggest that humic acids in lake sediments are related to chemical characteristics of phytoplankton. Results shed new light on the origins of humic substances in deep-water-lake sediments and provide insights into material recycling in such sediments.