Reaction of hydrogen and carbon dioxide behind reflected shock waves

Abstract

A complementary shock tube system was used to study dilute mixtures of carbon dioxide and hydrogen in a 1:5 ratio reacting behind reflected shock waves to produce water and carbon monoxide over the temperature range 2275-3860 K. One shock tube was outfitted to record simultaneously the infrared emissions from water and carbon dioxide through interference filters centered at 3.8 and 4.2 p, respectively. In order to minimize overlapping emissions, D2 was employed instead of H2. The formation of D2O exhibited quadratic dependence with respect to reaction time. The appearance of CO2 emission 4served primarily to mark time zero for the reaction and to establish the position of equilibrium. Argon was the inert diluent. The starting reactant percentages and the reflected shock zone pressure were varied for the purpose of determining the order dependencies for D2 and the total gas density. The second shock tube was connected to a time-of-flight mass spectrometer which recorded the histories of reactants, products, and intermediates. One notable feature of the TOF experiments was the detection of a small peak at m/e 29 corresponding to the HCO radical which was formed at times previous to significant CO production when H2 was used as a reactant. Runs performed on a, CO2-D2 mixture under similar conditions revealed the presence of DCO. The mole fraction for water formation from both shock tubes was fit to the expression (1 -/D2o//b2o,eq) * exp{-k [D2]0,3[M]0,7t2), where k = l02o o±o'2 exp(-81.4 ± 2.3/RT) cm3 mol-1 s-2. The units for the activation energy are kcal mol-1. Product profiles computed from a selection of literature rate constants making up an atomic mechanism did not compare favorably with the experimental results. The .possibility of a mechanism involving vibrational excitation of the reactants prior to transition state formation is discussed.

The high temperature pyrolysis of 1,3‐butadiene: heat of formation and rate of dissociation of vinyl radical

“…The TOF apparatus, sampling procedure, and data redulction process have been described previously [20,211. The mass spect.ra1 analysis was set at 30 p s intervals over typical observation times of 750 ps.…”

The self-exchange of dinitrogen behind reflected shock waves

“…The apparatus employed herein has been described previously. 15 Isotopic nitrogen (99% enrichment) was purchased from Stohler Isotope Chemicals and was used without further purification. Linde dry grade nitrogen was twice purified by condensation onto a type 4A molecular sieve trap at 77 K. In order to achieve the high temperatures required for exchange without saturating the TOF electron multiplier, a mixture of inert gases was used as the diluent.…”

Polypeptoid Monomer Sequence and Chemical Composition as Independent Controls of Interfacial Tension and Elasticity at Air/Fluid Interfaces

“…The type of structure that forms is determined by a packing parameter, a geometric descriptor of the balance between hydrophilic head and hydrophobic tail . For example, an anionic surfactant, sodium dodecyl sulfate, transitions from spherical to ellipsoidal micelles with increasing ionic strength because of the reduction in size of the headgroup due to Debye screening from the background electrolyte . A tool to quantify the adsorption behavior of nonionic surfactants is the hydrophile–lipophile balance (HLB), originally developed to determine the type of oil/water emulsions formed using an ethylene-oxide-containing surfactant .…”

“… 11 For example, an anionic surfactant, sodium dodecyl sulfate, transitions from spherical to ellipsoidal micelles with increasing ionic strength because of the reduction in size of the headgroup due to Debye screening from the background electrolyte. 12 A tool to quantify the adsorption behavior of nonionic surfactants is the hydrophile–lipophile balance (HLB), originally developed to determine the type of oil/water emulsions formed using an ethylene-oxide-containing surfactant. 13 HLB describes the mass fraction of the hydrophilic part of a nonionic surfactant on a scale of 0 to 20, with lower values being predominantly hydrophobic polymers suitable for antifoaming agents and water-in-oil emulsions and higher values being mostly hydrophilic polymers that work well as detergents, oil-in-water emulsifiers, and solubilizing agents.…”