Abstract:

Polyethylene hydrogenolysis can produce a variety of hydrogen hydride compounds, the product distribution is very wide, and the product selective regulation is challenging. A series of Ru/CeO₂ catalysts with different Ru particle sizes were prepared by regulating Ru loading. It was observed that the product distribution of polyethylene hydrogenolysis closely correlated with the coordination environments of metal Ru as determined by multiple techniques including TEM, in situ DRIFTS and model calculations. Characterizations and model calculations revealed that Ru nanoparticles with different particle sizes exhibited different metal dispersion, geometric structures and coordination environments. The C₂—C₄₀ alkanes selectivity of 92% was achieved by using Ru particle sizes with mean diameter of 0.85 nm where the edge/corner sites with low-coordination are dominant. The C₂—C₄₀ alkanes selectivity of 8% and the methane selectivity of 92% was obtained by using the Ru particle sizes with mean diameter of 2.75 nm where the terrace sites with highly coordinated platform sites are dominate. Combined with truncated hexagonal bipyramid model and CO-DRIFTS experiment, the selectivity of products over Ru/CeO₂ catalysts was correlated with the interaction between intermediates of polyethylene hydrogenolysis and the surface of Ru nanoparticles. Furthermore, the relation between reaction pathways in polyethylene hydrogenolysis and coordination environments of metal Ru was proposed.

Key words: degradation of waste plastic, catalyst, hydrogenation, hydrocarbons, ruthenium nanoparticles

摘要：

聚乙烯氢解可以产生多种碳氢化合物，产品分布非常宽，产物选择性调控具有一定挑战性。通过调控钌负载量制备了不同钌粒径的Ru/CeO₂催化剂，利用TEM、in situ DRIFTS和模型计算等多种技术，发现聚乙烯催化氢解的产物分布与钌金属配位环境密切相关。表征和模型计算表明，不同尺寸的钌纳米颗粒具有不同的几何结构和配位环境。钌平均粒径为0.85 nm时，低配位的边/角位点占主导，其C₂~C₄₀选择性达到92%。钌平均粒径达到2.75 nm时，高配位的平台位点占主导，C₂~C₄₀选择性仅为8%，甲烷选择性高达92%。结合截断六角双锥模型和CO-DRIFTS实验，推断Ru/CeO₂催化剂上产物的选择性可能与聚乙烯氢解中间体和钌纳米颗粒表面的相互作用有关，提出了Ru/CeO₂催化剂上聚乙烯氢解两种反应路径与配位环境的关系。

关键词: 废塑料降解, 催化剂, 加氢, 碳氢化合物, 钌纳米颗粒