Holocene reefs and sediments of Castle Harbour, Bermuda

Quantitative studies on the corals of Holocene fringing, pinnacle and knoll coral-algal reefs of Castle Harbour, Bermuda, show that only about 10% of the available reef substrate is coralcovered. Of this, about 70% of the total coral-covered area is occupied by corals belonging to the Madracis-Oculina assemblage...

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WEIRD languages have misled us too

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Dehydration Rate Measurements for tertiary-Butanol in a Variable Pressure Flow Reactor

Fundamentally, the dehydration reaction of tertiary-butanol is frequently used as an internal standard for relative rate studies of other decomposition reactions. We report here a study using radical trappers to isolate this path in tertiary-butanol pyrolysis experiments conducted in the Princeton variable pressure flow reactor between 658 and 980 K. A novel technique that determines the rate constant value by applying a global least-squares fit incorporating all experimental species (tertiary-butanol, isobutene, and water) evolution data is developed and applied to yield six rate constant values at two reaction pressures (6.1 and 18 atm) and at temperatures between 949 and 980 K. Data from previously reported studies are reanalyzed to evaluate their “absolute” uncertainties, and new Arrhenius parameters are derived based upon the present and previous measurements. The recommended rate constant (uncertainties) for the dehydration reaction is k = 2.88(0.91) × 107T2.21(0.10) s–1 exp(−62.4(0.9) kcal mol–1/RT). The new correlation is in excellent agreement with other independent experimental and theoretical studies appearing in the literature

Decomposition studies of isopropanol in a variable pressure flow reactor

Journal articleAlternatives to traditional petroleum derived transportation fuels, particularly alcohols, have been investigated increasingly over the last 5 years. Isopropanol has received little attention despite bridging the gap between smaller alcohols (methanol and ethanol) and the next generation alcohols (butyl alcohols) to be used in transportation fuels. Previous studies have shown that decomposition reactions that dehydrate are important in the high-temperature oxidation of alcohols. Here we report new data on the dehydration reaction for isopropanol (iC(3)H(7)OH -> C3H6 + H2O) in a Variable Pressure Flow Reactor at 12.5 atm pressure and temperatures from 976-1000 K. Pyrolysis experiments are performed in the presence of a radical trapper (1,3,5 trimethyl benzene or toluene) to inhibit secondary reactions of radicals with the fuel and product species. The recommended rate constant for the dehydration reaction is determined using an indirect method along with Latin Hypercube sampling to estimate uncertainties. Comparison of the rate constant data to previous works show that the reaction is considerably more rapid than the high level theoretical predictions of Bui et al. (Bui et al., J. Chem. Phys., 2002). The dehydration reaction rate for isopropanol is well described by k = 8.52 x 10(6)T(2.12) exp(-30, 667/T) with an estimated uncertainty of sigma(2)(lnA) = 0.0195.The C-C bond fission reaction is also investigated, but the insensitivity of the decomposition data to this reaction results in an uncertainty in the determined rate constants to approximately 2 orders of magnitude. Theoretical estimates lie within these experimental uncertainties.U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences - Award Number DE-SC0001198

Decomposition Studies of Isopropanol in a Variable Pressure Flow Reactor

Alternatives to traditional petroleum derived transportation fuels, particularly alcohols, have been investigated increasingly over the last 5 years. Isopropanol has received little attention despite bridging the gap between smaller alcohols (methanol and ethanol) and the next generation alcohols (butyl alcohols) to be used in transportation fuels. Previous studies have shown that decomposition reactions that dehydrate are important in the high-temperature oxidation of alcohols. Here we report new data on the dehydration reaction for isopropanol (iC3H7OH → C3H6 + H2O) in a Variable Pressure Flow Reactor at 12.5 atm pressure and temperatures from 976–1000 K. Pyrolysis experiments are performed in the presence of a radical trapper (1,3,5 trimethyl benzene or toluene) to inhibit secondary reactions of radicals with the fuel and product species. The recommended rate constant for the dehydration reaction is determined using an indirect method along with Latin Hypercube sampling to estimate uncertainties. Comparison of the rate constant data to previous works show that the reaction is considerably more rapid than the high level theoretical predictions of Bui et al. (Bui et al., J. Chem. Phys., 2002). The dehydration reaction rate for isopropanol is well described by k = 8.52 × 106T2.12 exp (− 30, 667/T) with an estimated uncertainty of σ  ln  A2 = 0.0195. The C–C bond fission reaction is also investigated, but the insensitivity of the decomposition data to this reaction results in an uncertainty in the determined rate constants to approximately 2 orders of magnitude. Theoretical estimates lie within these experimental uncertainties

Decomposition Studies of Isopropanol in a Variable Pressure Flow Reactor

Alternatives to traditional petroleum derived transportation fuels, particularly alcohols, have been investigated increasingly over the last 5 years. Isopropanol has received little attention despite bridging the gap between smaller alcohols (methanol and ethanol) and the next generation alcohols (butyl alcohols) to be used in transportation fuels. Previous studies have shown that decomposition reactions that dehydrate are important in the high-temperature oxidation of alcohols. Here we report new data on the dehydration reaction for isopropanol (iC3H7OH → C3H6 + H2O) in a Variable Pressure Flow Reactor at 12.5 atm pressure and temperatures from 976–1000 K. Pyrolysis experiments are performed in the presence of a radical trapper (1,3,5 trimethyl benzene or toluene) to inhibit secondary reactions of radicals with the fuel and product species. The recommended rate constant for the dehydration reaction is determined using an indirect method along with Latin Hypercube sampling to estimate uncertainties. Comparison of the rate constant data to previous works show that the reaction is considerably more rapid than the high level theoretical predictions of Bui et al. (Bui et al., J. Chem. Phys., 2002). The dehydration reaction rate for isopropanol is well described by k = 8.52 × 106T2.12 exp (− 30, 667/T) with an estimated uncertainty of σ  ln  A2 = 0.0195. The C–C bond fission reaction is also investigated, but the insensitivity of the decomposition data to this reaction results in an uncertainty in the determined rate constants to approximately 2 orders of magnitude. Theoretical estimates lie within these experimental uncertainties