High-temperature (> 1000'K) pyrolysis of acetaldehyde (-1 % in an atmosphere of pure nitrogen) was examined in a turbulent flow reactor which permits accurate determination of the spatial distribution of the stable species, Results show that the products in order of decreasing importance are CO, CHI, H2, C a 6 , and c2H4. Rates of formation were consistent with the Rice-Herzfeld mechanism by including reactions to explain CzH4 formation and the possible presence of ketene. A steady-state treatment of the complete mechanism indicates that the overall reaction order decreases from to 1, which is supported by the new experimental data. Using earlier low-temperature results, the rate (-81,775 f lOOO/RT) sec-l. Also, data for the ratio of rate constants for reactions CH3CHO + CH, -+ CH4 + C H 3 C 0 (4) and ZCH3 -+ C2H.5(6) were fitted to the empirical expression k l / k & / 2 = 10-13.89*0.03T6.1 exp( -1720 f 70/RT) (cm3/mole .sec)l'z and causes for the curvature are discussed. The noncatalytic effect of oxygen on acetaldehyde pyrolysis at high temperature is explained.constant for the reaction CH3CH0 -+ CH3 + CHO (1) was found as kt = 1016.s6*o.z1 exP

An adiabatic turbulent flow reactor was used to examine the pyrolysis of methanol in the temperature range 1070-1225 K at atmospheric pressure. Emphasis has been placed on determining the important initiation and termination steps and estimating rate constants for several reactions. A steady state treatment of the proposed 19-step mechanism yields a complex rate law for methanol decay. The roles of hydrogen as a promoter and methane as an inhibitor are accounted for in the proposed mechanism.

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The kinetics of pyrolysis of dimethyl ether were studied in an adiabatic flow reactor at temperatures between 790 and 950°C. The unimolecular rate constant for the initiating step CH30CH3 = CH30 + CH, was found to be k, = 2.16 X 1015e-76.@""RTse~-1. Aspects of the kinetic mechanism are discussed and a system postulated to account for the high-temperature products.

ABSTRACT"Gas-to-liquids" catalytic conversion technologies show promise for liberating stranded natural gas reserves and for achieving energy diversity worldwide. Some gas-toliquids products are used as transportation fuels and as blendstocks for upgrading crudederived fuels. Methylal(CHs-0-CHz-0-CH& also known as dimethoxymethane or DMM, is a gas-to-liquid chemical that has been evaluated for use as a diesel fuel component. Methylal contains 42% oxygen by weight and is soluble in diesel fuel. The physical and chemical properties of neat methylal and for blends of methylal in conventional diesel fuel are presented. Methylal was found to be more volatile than Y diesel fuel, and special precautions for distribution and fuel tank storage are discussed.Steady state engine tests were also performed using an unmodified Cummins 85.9 turbocharged diesel engine to examine the effect of methylal blend concentration on performance and emissions. Substantial reductions of .particulate matter emissions have been demonstrated 3r IO to 30% blends of methylal in diesel fuel. This research indicates that methylal may be an effective blendstock for diesel fuel provided design changes are made to vehicle fuel handling systems.

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The rates of peroxide formation in six model jet fuels were measured at various temperatures ranging from 43 to 120 °C with oxygen partial pressures ranging from approximately 10 to 1140 kPa. One of the fuels exhibited an increase in the rate of peroxide formation after alumina treatment, and three of the fuels showed induction periods. The results agreed with a kinetic model of the autoxidation process in that the peroxide concentration increased as the square of the stress duration. The rate of peroxide formation did not depend on the oxygen partial pressure. Arrhenius correlations of global rate constants determined from peroxide concentration time histories in accordance with the kinetic model showed that a single autoxidation mechanism explains the results obtained in the 43-120 °C temperature range. The results of this work encourage the development of a test method that predicts rate of peroxide formation at ambient conditions from data that may be obtained from more timely experiments at elevated temperatures.

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