Equilibrium relationships for non-equilibrium chemical dependencies

In contrast to common opinion, it is shown that equilibrium constants determine the time-dependent behavior of particular ratios of concentrations for any system of reversible first-order reactions. Indeed, some special ratios actually coincide with the equilibrium constant at any moment in time. This is established for batch reactors, and similar relations hold for steady-state plug-flow reactors, replacing astronomic time by residence time. Such relationships can be termed time invariants of chemical kinetics

Single-route linear catalytic mechanism : a new, kinetico-thermodynamic form of the complex reaction rate

For a complex catalytic reaction with a single-route linear mechanism, a new, kinetico-thermodynamic form of the steady-state reaction rate is obtained, and we show how its symmetries in terms of the kinetic and thermodynamic parameters allow better discerning their influence on the result. Its reciprocal is equal to the sum of n terms (n is the number of complex reaction steps), each of which is the product of a kinetic factor multiplied by a thermodynamic factor. The kinetic factor is the reciprocal apparent kinetic coefficient of the i-th step. The thermodynamic factor is a function of the apparent equilibrium constants of the i-th equilibrium subsystem, which includes the (n-1) other steps. This kinetico-thermodynamic form separates the kinetic and thermodynamic factors. The result is extended to the case of a buffer substance. It is promising for distinguishing the influence of kinetic and thermodynamic factors in the complex reaction rate. The developed theory is illustrated by examples taken from heterogeneous catalysis

New invariant expressions in chemical kinetics

This paper presents a review of our original results obtained during the last decade. These results have been found theoretically for classical mass-action-law models of chemical kinetics and justified experimentally. In contrast with the traditional invariances, they relate to a special battery of kinetic experiments, not a single experiment. Two types of invariances are distinguished and described in detail: thermodynamic invariants, i.e., special combinations of kinetic dependences that yield the equilibrium constants, or simple functions of the equilibrium constants; and "mixed" kinetico-thermodynamic invariances, functions both of equilibrium constants and non-thermodynamic ratios of kinetic coefficients

Flame Synthesis of Pd-TiO2 Nanocomposite Catalyst for Oxygen Removal from CO2-rich Streams in Oxy Combustion Exhaust

Pd-TiO2 catalysts with five Pd loadings were synthesized using a flame aerosol reactor. Their initial and changed catalytic properties and kinetic characteristics during/for O2 removal with CH4 were investigated. Different Pd loadings affected the size of Pd sub-nano clusters/nanoparticles and the speciation fraction of Pd (metallic Pd, PdO and PdOx (0〈x〈1)). Increased size of Pd nanoparticles on catalysts’ surface due to sintering and the reduction of PdO to metallic Pd or/and PdOx were observed during the reaction. Fractions of the total surface area of Pd species were calculated, and correlations to the apparent reaction rate constants were established. Apparent kinetic constants were linearly proportional to fractions of total surface areas of metallic Pd or/and reduced Pd oxide were revealed, representing the intrinsic active site. The linear correlation between the O2 reaction rate and the CO2 concentration in the initial gas stream was also observed due to an autocatalytic reaction effect