Gas-phase catalytic hydration of I_(2)O_(5) in the polluted coastal regions:Reaction mechanisms and atmospheric implications

Marine aerosols play an important role in the global aerosol system.In polluted coastal regions,ultra-fine particles have been recognized to be related to iodine-containing species and is more serious due to the impact of atmospheric pollutants.Many previous studies have identified iodine pentoxide(I_(2)O_(5),IP)to be the key species in new particles formation(NPF)in marine regions,but the role of IP in the polluted coastal atmosphere is far to be fully understood.Considering the high humidity and concentrations of pollutants in the polluted coastal regions,the gas-phase hydration of IP catalyzed by sulfuric acid(SA),nitric acid(NA),dimethylamine(DMA),and ammonia(A)have been investigated at DLPNO-CCSD(T)//ωB97 XD/aug-cc-pVTZ+aug-cc-pVTZ-PP with ECP28 MDF(for iodine)level of theory.The results show that the hydration of IP involves a significant energy barrier of 22.33 kcal/mol,while the pollutants SA,NA,DMA,and A all could catalyze the hydration of IP.Especially,with SA and DMA as catalysts,the hydration reactions of IP present extremely low barriers and high rate constants.It is suggested that IP is unstable under the catalysis of SA and DMA to generate iodic acid,which is the key component in NPF in marine regions.Thus,the catalytic hydration of IP is very likely to trigger the formation of iodine-containing particles.Our research provides a clear picture of the catalytic hydration of IP as well as theoretical guidance for NPF in the polluted coastal atmosphere.

Catalytic Hydration of Aromatic Alkynes to Ketones over H-MFI Zeolites

The hydration of alkyne represents the most straightforward and simplest route toward the synthesis of ketone. Herein, Brønsted acidic zeolites are explored as potential catalysts for the liquid-phase phenylacetylene hydration. The topology structure and Si/Al ratio are disclosed to be key factors controlling the catalytic activity of zeolites. Typically, H-MFI zeolite with a Si/Al molar ratio of 13 exhibits the highest catalytic activity, with turnover frequency of 6.0 h-1 at 363 K. Besides, H-MFI zeolite shows good catalytic stability and recyclability in the reaction of phenylacetylene hydration, and the substrate scope can be simply extended to other soluble aromatic alkynes. The reaction mechanism of phenylacetylene hydration is investigated by means of kinetic and spectroscopic analyses. The Markovnikov electrophilic addition of phenylacetylene by hydrated protons is established as the rate-determining step, followed by deprotonation and enol isomerization to derive acetophenone product.

Catalytic Hydrogenation of Nitrobenzene to Aniline by Ag/γ-Fe_2O_3

The Ag/γ-Fe_2O_3 nanocomposite was synthesized by solvothermal reduction method via using ferric nitrate and silver nitrate as raw materials, and ethylene glycol as the reducing agent. The composite was characterized by X-ray powder diffraction, scanning electron microscope, transmission electron microscope, and energy dispersive X-ray. The prepared Ag/γ-Fe_2O_3 was used for the catalytic hydrogenation of nitrobenzene to aniline by hydrazine hydrate. The factors such as the silver content in the catalyst, reaction time, reaction temperature and the regeneration of catalyst were investigated. The results showed that the yield of aniline reached 100% by utilizing the 1%wt（nitrobenzene） Ag/γ-Fe_2O_3 for the catalytic hydrogenation of nitrobenzene for 3 h to obtain aniline at 78 ℃, hydrazine hydrate as the hydrogen source, while the silver content in the catalyst was 3%mol.