An equipment for three-dimensional spatially resolved gas analysis

The apparatus described is able to measure three-dimensional temperature an d partial pressure distributions in gas mixtures with a spatial resolution better than 0.5 mm. The measurements are performed in a well defined lamina r gas flow in a duct of rectangular cross section. The gas mixture is sampl ed locally with a quartz tube orifice leak movable in three dimensions. Mas s spectrometry is used for partial pressure measurements. The total pressur e in the duct can be regulated in the range 50-760 Torr and the gas tempera ture can be varied between room temperature and 500 degrees C. The apparatu s is primarily designed for studies of the distribution of reactants and pr oducts over catalytic surfaces. Because of the well defined gas flow in the duct the partial pressure distributions of reactants and products over the catalytic surface can be calculated with good accuracy. By comparing calcu lated pressure distributions to measured ones the local reaction rate on th e catalytic surface as well as the pressures of reactants and products at t he surface can be obtained. As an example it is shown how the hydrogen dist ribution over a platinum surface exposed to a mixture of hydrogen, oxygen, and argon can be used to calculate the local water formation rate on the pl atinum surface. (C) 2000 American Institute of Physics. [S0034-6748(00)0140 9-X].