含催化剂失活的反应扩散模型中的相变和交叉
Phase transitions and crossovers in reaction-diffusion models with catalyst deactivation
摘要：
催化材料的活性在操作期间通过几种机制降低，其中之一是催化位点被化学吸附的杂质或产物毒化。在这里，我们研究了在两个反应扩散模型中的中毒与随机分布的催化位点的一维晶格的影响。单分子和双分子单物种反应被认为是，在操作过程中没有反应物输入。模型显示了反应物浓度连续衰减的阶段和具有渐近非零反应物浓度和催化剂完全中毒的阶段之间的过渡。过渡边界取决于初始反应物和催化剂浓度和中毒概率。临界体系的行为类似于两物种湮灭反应，反应物浓度随时间t^{-1/4}衰减，催化位起第二物种的作用。在单分子反应中，即使当这些参数之一是10%远离临界时，观察到一个显着的交叉渐近标度。因此，浓度的有效幂律衰减可能持续很长时间，并导致反应动力学的明显变化。在双分子单组分反应中，临界标度之后是二维快速衰减，因此发现了两个交叉。
英文摘要：
The activity of catalytic materials is reduced during operation by several mechanisms, one of them being poisoning of catalytic sites by chemisorbed impurities or products. Here we study the effects of poisoning in two reaction-diffusion models in one-dimensional lattices with randomly distributed catalytic sites. Unimolecular and bimolecular single-species reactions are considered, without reactant input during the operation. The models show transitions between a phase with continuous decay of reactant concentration and a phase with asymptotic non-zero reactant concentration and complete poisoning of the catalyst. The transition boundary depends on the initial reactant and catalyst concentrations and on the poisoning probability. The critical system behaves as in the two-species annihilation reaction, with reactant concentration decaying as t^{-1/4} and the catalytic sites playing the role of the second species. In the unimolecular reaction, a significant crossover to the asymptotic scaling is observed even when one of those parameters is 10% far from criticality. Consequently, an effective power-law decay of concentration may persist up to long times and lead to an apparent change in the reaction kinetics. In the bimolecular single-species reaction, the critical scaling is followed by a two-dimensional rapid decay, thus two crossovers are found.
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