Quasi-stationary chain-branched process

The second phase is a quasi-stationary chain-branched process with a quadratic radical termination, which proceeds mainly via the recombination of methyl-peroxy radicals... 

The model also revealed the importance of non-linear interactions of chains, which determine the existence of two quasi-stationary oxidation modes. The difference in reaction rate between them is about four orders of magnitude. A critical transition between these modes is taking place due to small changes in reaction parameters, e.g., pressure. This critical transition leads to a very fast increase in the oxidation rate and an abrupt transition from the low-pressure slow oxidation to the fast high-pressure stationary chain-branching process. In the latter mode, radical generation is no more determined by a slow initiation reaction, but by very fast chain-branching reactions. It is the phenomenon... 

Another general problem, the development of an algorithm for the construction of kinetic models for the quasi-stationary state of the evolution of non-equilibrium chemical system, is solved by the method of linear routes as simple cycles of a graph assigned to sets of elementary reactions and intermediate substances (see Chapter 2). A general algorithm for construction of kinetic models for the linear catalytic and un-branched radical-chain processes, including a free radical polymerization, is proposed. 

The nonlinear processes of interaction of the chains determine the existence of two quasi-stationary modes of oxidation simple chain and steady-state branched-chain modes, with a difference in the rates of lO (Fig. 5.3) and a critical transition between them upon variation of the reaction parameters, especially, the pressure (Fig. 3.2). 

It is the occurrence of a fast steady-state branched-chain reaction that enables to realize a noncatalytic gas-phase process and create a stationary technological process on its basis. The quasi-steady-state branched-chain mode provides a high rate of a noncatalytic reaction at relatively low temperatures, whereas the absence of a solid phase (catalyst) minimizes the influence of heterogeneous processes, which lead to the formation of deep oxidation products. In addition to the critical transition between the oxidation modes, other manifestations of the nonlinear nature of the process, such as cool flames, NTC region, reaction rate temperature hysteresis, and oscillatory regimes, have been observed. 

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