Oscillatory behavior during CO oxidation over Pd supported on glass fibers: experimental study and mathematical modeling

The oscillatory behavior during CO oxidn. over Pd supported on glass fibers was studied in a recycle reactor. The properties of oscillations as a function of temp. and inlet CO concn. were investigated in detail. The peculiarity of the obsd. oscillations is their long period up to 6 h. Math. model considering oxidn.-redn. processes of the Pd was developed to describe the exptl. results. The model accounts for the obsd. reaction rate dependence on the CO inlet concn., the region of oscillations and the dependence of the oscillatory behavior upon temp. and CO inlet concn. [on SciFinder (R)

Selectivity in catalysis by hydrogen-porous membranes

The methods of controlling a catalyst's selectivity by holding its surface (and in special cases its sub-surface) layer in non-stationary states towards the reagents are discussed. This may be achieved by the use of (a) a membrane catalyst; (b) a fluid bed; (c) a riser reactor; (d) periodical changes of the process parameters or catalyst circulation between the reactor and the regenerator; (e) a chromatographic regime; (f) a self-oscillating or stochastic regime. The membrane catalyst produces a non-stationary state of the catalyst surface more easily than do the other methods and for a longer period of time. This propensity of the membrane catalyst is especially important for small-scale industrial installations and for producing ultrapure substances. The transfer of one reagent through the catalyst, for example through a palladium-based septum, increases the selectivity of the hydrogenation of triple bonds into double bonds and of, say, one double bond in a cyclic diene in comparison with normal hydrogenation by the same catalyst. Selectivity of the hydrogenation is a function of hydrogen content in the membrane catalyst. It is shown that hydrogen atoms extracted from the sub-surface layer of the membrane catalyst participate in the hydrogenation process

Selectivity in catalysis by hydrogen-porous membranes

The methods of controlling a catalyst's selectivity by holding its surface (and in special cases its sub-surface) layer in non-stationary states towards the reagents are discussed. This may be achieved by the use of (a) a membrane catalyst; (b) a fluid bed; (c) a riser reactor; (d) periodical changes of the process parameters or catalyst circulation between the reactor and the regenerator; (e) a chromatographic regime; (f) a self-oscillating or stochastic regime. The membrane catalyst produces a non-stationary state of the catalyst surface more easily than do the other methods and for a longer period of time. This propensity of the membrane catalyst is especially important for small-scale industrial installations and for producing ultrapure substances. The transfer of one reagent through the catalyst, for example through a palladium-based septum, increases the selectivity of the hydrogenation of triple bonds into double bonds and of, say, one double bond in a cyclic diene in comparison with normal hydrogenation by the same catalyst. Selectivity of the hydrogenation is a function of hydrogen content in the membrane catalyst. It is shown that hydrogen atoms extracted from the sub-surface layer of the membrane catalyst participate in the hydrogenation process