Atmospheric Oxidation Rate Program

Howard, P. 1993. Atmospheric Oxidation Rate Program , Syracuse Research Corporation, 6225 Running Ridge Road, N. Syracuse, NY 13212-2509. 

AOPWIN Atmospheric oxidation rate prediction program... 

A variety of methods have been recently reviewed [23] and several new methods have been published since then [24]. There is one program, the atmospheric oxidation rate prediction program or AOPWIN - part of the EPI Suite software - that will calculate the hydroxyl radical and ozone rate constants and atmospheric half-lives (with selected oxidant concentrations) [23,25]. The program uses the method of Atkinson and coworkers [26]... 

One method used often relies on structure-reactivity relationships (Atkinson, 1986,1987, 1988 Kwok and Atkinson, 1995). This empirical estimation method has been shown to provide good agreement (generally to within a factor of 2) between experimentally measured and calculated room temperature rate constants for 90% of 485 organic compounds (Kwok and Atkinson, 1995). It is the basis of the Syracuse Research Corporation s "Atmospheric Oxidation Program" [see Meylan and Howard (1993) for a discussion of an earlier version of this program]. The general approach of this estimation method has been described (Atkinson, 1986,1987,1988 Kwok and Atkinson, 1995). 

Similarly, the most recent version of the Atmospheric Oxidation Program (version 1.8) gives agreement of the calculated and experimental room temperature rate constants to within a factor of 2 for 90% of 647 organic compounds, with a standard deviation of 0.242 log units (i.e., a factor of 1.75) (Meylan, 1997). However, extrapolation of this estimation method to organic compounds outside of the database used for its development and testing lacks reliability and is not recommended. 

Results of an experimental program in which aluminum particles were burned with steam and mixtures of oxygen and argon in small-scale atmospheric dump combustor are presented. Measurements of combustion temperature, radiation intensity in the wavelength interval from 400 to 800 nm, and combustion products particle size distribution and composition were made. A combustion temperature of about 2900 K was measured for combustion of aluminum particles with a mixture of 20%(wt.) O2 and 80%(wt.) Ar, while a combustion temperature of about 2500 K was measured for combustion of aluminum particles with steam. Combustion efficiency for aluminum particles with a mean size of 17 yum burned in steam with O/F) / 0/F)st 1-10 and with residence time after ignition estimated at 22 ms was about 95%. A Monte Carlo numerical method was used to estimate the radiant heat loss rates from the combustion products, based on the measured radiation intensities and combustion temperatures. A peak heat loss rate of 9.5 W/cm was calculated for the 02/Ar oxidizer case, while a peak heat loss rate of 4.8 W/cm was calculated for the H2O oxidizer case. 

Temperature programmed oxidation (TPO) was performed by burning the obtained coked catalyst in 1%02 in an He atmosphere. The heating rate was 10°C/min. CO2 produced was measured using a gas chromatograph equipped with a TCD and an on-line gas sampling valve. 

Pig. 7.8 Temperature dependence of CH3OH conversion during temperature-programmed start-up over the Cu/ZnO/Al2C>3 catalyst in different initial states (o), oxidized ( ), reduced ( ), reduced + air exposed. Atmospheric pressure, feed ratio O2/CH3OH = 0.3, heating rate = O.lK/min (after Ref. 152). 

Vapour-phase oxidation of IBA was carried out in a continuous-flow laboratoiy reactor, at atmospheric pressure. The standard feed composition was IBA 2%, O2 20%, H2O 4%. liie toted flow rate was 60 mL/min and the amount of catalyst used was 1 g (approximately 1 mL). The reaction products, kept at 200C to prevent condensation, were analysed by gas chromatography a GP 10% SP-1200/1% H3PO4 on Chromosorb WAW was used to separate IBA, propylene, acetone and MAA, with oven temperature programmed om 40 to lOOC (FID) a Carbosieve S column was utilized for analysis of CO and CO2, with oven temperature programmed from 40C to 200C (TCD). All the catalysts were kept under reaction environment for approximately 50-70 hours along this period, after an initial unstable behavior, no deactivation phenomena were observed. 

Studies of the homomolecular and heterolytic exchange processes are generally in the form of the measurement of rates under isothermal conditions. However, studies have also been made of temperature programmed isotopic exchange, in which the oxide is subjected to a temperature ramp under the reaction atmosphere, and the partial pressures of various isotopic oxygen species is determined as a function of temperature (e.g., Refs. 20-21). The photoactivation of oxygen exchange has also been reported in a number of studies which have been performed under UV irradiation (e.g.. Refs. 18, 22, 23). 

For oxidation onset temperature measurements (temperature ramp) at 13.6 atmospheres pressure setting, a 10°C/min heating rate was used. The sample temperature was programmed to increase at a rate of 10°C/min from 100°C to 320°C. After the test was completed, the inlet valve on the cell was closed, and the pressure was released by opening the pressure-release valve. 

The experimental samples used were fused iron catalyst, which contain promoters such as AI2O3, K2O, CaO, Si02 and used the different iron oxides as precursors. First, samples were reduced for 96 h in pure hydrogen (99.9999%) at atmospheric pressure. The H2 flow rate was 270ml min. Temperature-program steps were as follows 450°C for 72h, 475°C for 12h and 500°C for 12 h with temperature ramp for all stages of 10 ml min C... 

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