Ru/hierarchical HZSM-5 zeolite as efficient bi-functional adsorbent/catalyst for bulky aromatic VOCs elimination

This study focused on the elimination of bulky aromatic VOCs by adsorption/combustion in humid conditions using Ru/hierarchical HZSM-5 zeolites as adsorbent and catalyst. Compared with Ru/conventional HZSM-5 zeolite, Ru/hierarchical HZSM-5 showed increased external surface and mesoporous volume, shortened diffusion length and enhanced low-temperature reducibility. Adsorption experiments demonstrated that Ru/hierarchical HZSM-5 zeolite was a very efficient adsorbent for the removal of bulky aromatic VOCs. In addition, the catalytic activity of as-prepared composite in VOCs combustion showed good correlations with their textural characteristics. The value of turnover frequency (rTOF) of Ru/hierarchical HZSM-5 was about twice, three and four times to that of Ru/conventional HZSM-5 toward toluene, o-xylene and TMB combustion, respectively, which indicated Ru/hierarchical HZSM-5 zeolites had more significant performance for catalyzing combustion of bulkier molecule. More importantly, Ru/hierarchical HZSM-5 showed the efficient bi-functional performance during the adsorption/combustion cycling process for bulky aromatic VOCs. In addition, the good carbon balance has been kept for each cycle without the production of secondary pollutants.