No abstract

We oxidized methanol in supercritical water at 246 atm and temperatures between 500 and 589 °C. Pseudofirst-order rate constants calculated from the data led to Arrhenius parameters of A ) 10 21.3(5.3 s -1 and E a ) 78 ( 20 kcal/mol. The induction time for methanol oxidation decreased from 0.54 s at 525 °C to 0.093 s at 585 °C and the reaction products were formaldehyde, CO, and CO 2 . Formaldehyde was a primary product, while CO and CO 2 were secondary products. Formaldehyde was more reactive than methanol and its yield was always less than 24%. The temporal variation of the CO yield exhibited a maximum, whereas the CO 2 yield increased monotonically. The experimental data were consistent with a set of consecutive reactions (CH 3 OH f CH 2 O f CO f CO 2 ) with pseudo-first-order global kinetics. The experimental data were also used to validate a detailed chemical kinetics model for methanol oxidation in supercritical water. With no adjustments, this elementary reaction model quantitatively predicts the product distribution as a function of the methanol conversion, and it accurately predicts that this distribution is nearly independent of temperature. A sensitivity analysis revealed that only eight elementary reaction steps most strongly influenced the calculated species' concentrations. A reaction path analysis showed that the fastest reactions that consumed methanol involved OH attack and the resulting radicals produced formaldehyde, which was attacked by OH to form, eventually, CO. The CO was then oxidized to CO 2 via reaction with OH. This work shows that the chemistry for methanol oxidation in supercritical water at temperatures around 500-600 °C is quantitatively analogous to combustion chemistry within the same temperature range.

From July 1998 to March 1999, a study was made of a total of 27 treatment plants for the principal purpose of understanding the actual condition of endocrine disrupting chemicals (EDCs) in sewage, and the behavior of EDCs in wastewater treatment plants. The results showed actual levels of influent and effluent concentrations of EDCs in sewage. Substances detected above the minimum limit of determination were 15 for wastewater influent and 6 for effluent. Similarly, nonyl phenol ethoxylate and 17 beta-estradiol, which are highlighted as pertinent substances, were detected. It was confirmed that the reduction ratio of EDCs in treatment plants was 90% or more for almost all substances. The behavior of EDCs in general in treatment plants was also studied. As a result, the EDCs reduction effect was recognized in both the primary setting tank and biological reaction tank, though the trend varies among substances.

No abstract

We have developed a flow reactor system that smoothly gasifies glucose and glucose-lignin mixture solution at 673 K, 25.7 MPa. The reactor system consists of three continuous reactors, which are a pyrolysis reactor, an oxidation reactor, and a catalytic reactor. We have investigated the reactions that occurred in each reactor and evaluated favorable residence time. We have succeeded in achieving high gasification efficiency based on carbon up to 96% at 673 K, 25.7 MPa with total residence time of about 1 min. The main gaseous products were H 2 and CO 2 . The results indicated that this three-reactor system is promising for low-temperature (i.e., around 673 K) biomass gasification in supercritical water.