I. S. Zaslonko

Nonisothermal effects in the process of soot formation in ethylene pyrolysis behind shock waves

The nonisothermal nature of hydrocarbon pyrolysis explains the differences in the critical temperatures of soot formation in the experimental studies of these processes. When reaction heats are taken into account, the critical temperatures become close to 1600 K for all the systems studied. The estimated standard enthalpy of carbon atom formation in the composition of soot particles is δHf, z. ≈ 11 ±6 kJ/mol. A kinetic model is proposed for soot formation in ethylene pyrolysis that describes the experimental data. The calculated temperature of soot particles may differ substantially depending on the choice of a model for energy exchange in collisions.

Kinetics of Carbon Cluster Formation in the Course of C3O2Pyrolysis

The kinetics of the formation of condensed carbon particles in the thermal decomposition of C3O2molecules behind shock waves was experimentally studied at temperatures of 1200–2500 K, pressures of ∼20–60 atm, and molar fractions of C3O2in a mixture with argon in the range 0.03–2.00%. The concentration of condensed carbon particles was measured by the absorption of laser radiation at wavelengths of 632.8 and 1064 nm. The experimental results were compared with data calculated in the framework of three different models. Two of these models (analytical) include the kinetics of the formation of the particle-size distribution function and give a simplified description of the kinetics of gas-phase reactions involving C3O2and decomposition fragments. The third model (numerical) combines detailed descriptions of the kinetics and the coagulation dynamics. Several types of condensed carbon particles were considered: carbon clusters, soot particles, and fullerenes. The transitions between various forms of condensed carbon particles were included into the kinetic scheme of the model. All main observed specific features of the growth kinetics of condensed carbon particles during C3O2pyrolysis can be described in terms of these models.

Kinetics of soot formation in tetrachloromethane pyrolysis

Kinetics of soot formation is studied in tetrachloromethane pyrolysis behind shock waves. The time dependences of macrokinetic characteristics of soot particle growth (the induction period, the soot yield, and the apparent rate constant of soot particle growth) are determined. Based on the experimental data, the quantitative model of soot formation is developed for tetrachloromethane pyrolysis behind shock waves. Special attention is paid to the thermal effects in CC14 pyrolysis.

Nonequilibrium Excitation of C2 Radicals during the Thermal Decomposition of C3 O2 behind Shock Waves

C2 concentrations and populations of the ground and the first excited vibrational levels of electronically excited C2(d3Π) radicals during the thermal decomposition of C3O2 behind shock waves were monitored by emission and absorption measurements in the (0-0) and the (1-0) Swan-bands. Experiments were carried out in mixtures of 1% C3O2+Ar and 1% C3O2+He at T=2100–3200 K and p=1.5–7.5 bar. In the whole range of conditions studied an essential nonequlilibrium of electronic and vibrational states of nascent C2 radicals was observed. For analyzing possible formation and consumption reactions of the excited C2 radicals, a convenient kinetic scheme of the C3O2 decomposition was developed, which considers both the recombinative pumping process and exchange and quenching reactions of the C2(d3Π, v=0, 1) states.

Reactions of chromium atoms with chloromethanes

The rate constants of the gas-phase reactions of the chromium atom with CC14, CHC13, and CH2Cl2 were measured behind shock waves at 800–1400 K. The results are presented in the Arrhenius form (the activation energy is given in kJ/mol):kCCl4 = 1014.32±0.36exp[-(2.0±7.5)/RT],kCHCl3 = 1014.72±0.21exp[-(18.5.±4.0)/RT, andkCH2Cl2> = 1014.33±0.16exp[-(24.1±3.1)/RT]cm3mol-1s-1.

Application of the Monte Carlo method to modeling of kinetic processes with the participation of polyatomic molecules and clusters: 1. Kinetics of energy transfer during collisions of polyatomic molecules

The Monte Carlo method was used to model the collisional energy transfer for polyatomic molecules within the framework of the statistical theory of reactions. A model describing energy transfer through the formation of a statistical collisional complex was suggested. It was assumed that the total energy of the complex was randomized in the course of collisions and statistically distributed among the internal and translational degrees of freedom. The method was verified by comparing the equilibrium distribution functions for the vibrational, rotational, and total energies of the molecule. The mean energy portion and the root-mean-square energy portion transferred per collision, as functions of the total molecular energy, were determined. The relaxation parameters of the population distribution over energy after a sharp increase in the bath-gas temperature were calculated.