Coupled Gas Phase Research Articles

New approaches on gas phase molecular absorption spectrometry detection in gas chromatography.

A hyphenated technique for coupling a spectrophotometric detector to a gas chromatograph with a packed column is described. The packed column was connected directly to the flow cell (path length 1 cm) which was placed in a UV-visible molecular absorption spectrophotometer with diode array detector. This detection system was employed for separating and determining benzene, toluene, 1,4-xylene, 1,2-xylene and mesitylene. Molecular absorption spectra of all the separated compounds have also been obtained. A new possibility for coupling capillary gas chromatography and gas phase molecular absorption spectrometry is currently being tested. In this new case, two fibre optics are used and the measurement is performed in the capillary column.

Coupled Electrocatalysis and Gas Phase Diffusion in a Stabilized‐Zirconia Tubular Flow Oxygen Pump

A tubular electrochemical reactor constructed from a 10 mole percent electrolyte tube with porous Au electrodes on its inner and outer surfaces was operated as an oxygen pump in the temperature range 650°–850°C. Gas mixtures with different content were circulated through the inside cathodic wall of the tube, where was electrochemically reduced and pumped out through the outer anodic wall of the tube to an annular chamber. The current‐overpotential behavior of the cell was found to be dominated by catalytic rate processes at the cathode. The electrochemical kinetics can be described by a modified Butler‐Volmer expression. The behavior of the tubular flow reactor in the integral mode of operation was studied by numerically solving the convective‐diffusion equation of change for molecules in the gas phase, incorporating both radial and axial diffusion and electrochemical reaction on the tube wall. The finite‐difference method of successive over‐relaxation was used to solve the governing mass‐transfer equation. When the axial change in concentration at the tube wall is accounted for, the computed integrated currents agree very well with the experimentally measured values, allowing the prediction of total ionic current and fractional reactant conversion for a given set of flow and physical variables. Under certain conditions, axial diffusion is found to be quite pronounced, with concentration disturbances penetrating the region well upstream of the inlet to the reaction zone , and significantly decreasing the concentrations at from values in the entering feed stream.

Kinetic analysis of coupled gas phase oxidation reaction of secondary alcohols on iridium

Kinetics of partial gas phase oxidation of 2-butanol (B) and 4-methyl-2-pentanol (M) to ketones on Ir/C catalyst at 150 °C has been studied. In single reactions alcohol B was 4-7times more reactive than alcohol M, in competitive reactions the latter was twice as reactive as the former. Separate treatment of rate data for single and competitive reactions of both alcohols showed that each set could be described by nearly the same set of equations on 99% confidence level, including, of course, very different kinetic models. Confrontation of the kinetics of single and competitive reactions (comparison of the values of corresponding constants of rate equations) and the analysis of relative reactivities revealed the unfitness of Langmuir-Hinshelwood and redox models in this case. A model taking into account nonhomogeneity of the surface and a model derived on the basis of a chain mechanism would be able to describe better and in consistent way the kinetics of single and competitive reactions as well as the observed inversion of the reactivity of studied alcohols.

Oxidation in High Temperature Petrogenesis

A study has been made of a variety of metamorphic and magmatic rocks to determine how oxidative processes are reflected in their mineral assemblages. In this study particular attention is paid to solid solutions. Field and experimental evidence agree with theory as to the responses of ferromagnesian solid solution to compositional changes of the coupled gas phase. Typical of these responses are the increases shown by the ratios Fe 2 O 3 /FeO and MgO/(MgO + FeO) with increasing P O2 . Attention is also directed to the consequences of the normally low values of P O2 /P H2O to gaseous transport by bodily flow and diffusion in regional metamorphism. Examples of oxidative and related processes are drawn from regionally metamorphosed Fe formation of Quebec and the Lake Superior region, from numerous contact metamorphic deposits, from the extrusives of the San Juan region of Colorado, and from other magmatic provinces. A thermodynamic unity of response to oxidative processes is shown by these different rock types.