It is well known that urbanization and industrialization have resulted in the rapidly increasing emissions of volatile organic compounds (VOCs), which are a major contributor to the formation of secondary pollutants (e.g., tropospheric ozone, PAN (peroxyacetyl nitrate), and secondary organic aerosols) and photochemical smog. The emission of these pollutants has led to a large decline in air quality in numerous regions around the world, which has ultimately led to concerns regarding their impact on human health and general well-being. Catalytic oxidation is regarded as one of the most promising strategies for VOC removal from industrial waste streams. This Review systematically documents the progresses and developments made in the understanding and design of heterogeneous catalysts for VOC oxidation over the past two decades. It addresses in detail how catalytic performance is often drastically affected by the pollutant sources and reaction conditions. It also highlights the primary routes for catalyst deactivation and discusses protocols for their subsequent reactivation. Kinetic models and proposed oxidation mechanisms for representative VOCs are also provided. Typical catalytic reactors and oxidizers for industrial VOC destruction are further discussed. We believe that this Review will provide a great foundation and reference point for future design and development in this field.

/pdf/recent-advances-in-the-catalytic-oxidation-of-volatile-zw2c35dbg7.pdf

Recent Advances in the Catalytic Oxidation of Volatile Organic Compounds: A Review Based on Pollutant Sorts and Sources.

To elucidate the role of oxygen vacancy defects, various Mn-based oxides with oxygen vacancy defects are employed to the toluene oxidation, which are synthesized by adjusting solvent and double-complexation routes. The MnOx-ET catalyst shows the highest catalytic activity (T90 = 225 °C) for toluene oxidation. Compared with other Mn-based oxides, the as-prepared MnOx-ET catalyst has more surficial oxygen vacancies and good oxygen storage capacity (OSC), which is the reason on its remarkable activity for toluene oxidation. In addition, in situ DRIFTS study reveals that both lattice oxygen and adsorbed oxygen species can participate in the activation-oxidation process of toluene, which results in two reaction routes for the toluene oxidation. The rich oxygen-vacancy concentration of catalysts accelerates the key steps for the activation and generation of oxidized products. Quasi-in situ XPS results further confirm that enrich adsorbed-oxygen species as active oxygen and increasing Mn4+ concentration enhance the superior activity for toluene oxidation.

Highly efficient mesoporous MnO2 catalysts for the total toluene oxidation: Oxygen-Vacancy defect engineering and involved intermediates using in situ DRIFTS

Volatile organic compounds (VOCs) with the properties of volatility, toxicity and diffusivity pose a serious threat to human health and eco-environment. Catalytic oxidation technology has been considered as a highly efficient option for the treatment of VOCs. This review systematically summarizes the recent processes and advances on catalytic elimination of VOCs over nanoparticles catalysts. Firstly, catalytic performances of catalysts for VOC degradation are evaluated and compared on the basis of unified performance metrics. Secondly, catalytic mechanisms of VOC oxidation, based on experimental and theoretical studies, are systematically introduced. Then, catalytic reactors employed in VOC elimination processes are summarized. In particular, photothermocatalysis by integrating (thermo)catalysis with photocatalysis is also elucidated. Lastly, the perspectives to the scientific issues and challenges faced, as well as the future outlooks are proposed. Collectively, this review will provide theoretical and experimental foundation for rational fabrication and application of nanoparticles catalysts toward VOC elimination in future.

Recent advances in VOC elimination by catalytic oxidation technology onto various nanoparticles catalysts: a critical review

Adsorption/desorption kinetics and breakthrough of gaseous toluene for modified microporous-mesoporous UiO-66 metal organic framework.

The highly dispersed Pd nanoparticles supported UiO-66 catalysts were successfully prepared via ethylene glycol reduction method (Pd-U-EG). And their catalytic performances were evaluated by toluene degradation. A series of characterization methods were carried out to characterize the physicochemical properties of the samples. During the effect of high weight hourly space velocity, stability and reusability test, the catalytic activity of Pd-U-EG remains unchanged, which also indicated good catalytic performance. More importantly, water resistance test (10-20 vol.% water) indicated that Pd-U-EG had a great water resistance. The study of toluene-TPD, toluene-TPSR and in-situ DRIFTS at different temperatures under different conditions over Pd-U-EG indicated the role of H2O. The introduction of H2O at low temperature was conducive to the adsorption of toluene, but inhibited the degradation of toluene. Differently, the H2O presence at high temperature was favorable to toluene degradation. In addition, toluene degradation mechanism was also revealed.

Excellent catalytic activity and water resistance of UiO-66-supported highly dispersed Pd nanoparticles for toluene catalytic oxidation

In situ pyrolysis of Ce-MOF to prepare CeO2 catalyst with obviously improved catalytic performance for toluene combustion

Inhibitory effects of water vapor on elemental mercury removal performance over cerium-oxide-modified semi-coke

The invention discloses a preparation method of a sulfur-tolerant renewable molecular sieve for removing elemental mercury in natural gas and belongs to the technical field of preparation of molecular sieves. The method comprises the steps as follows: (1) adopting sodium aluminate and silica sol as a silicon source and an aluminum source; (2) preparing an [Ag(NH3)]OH and Pd(NH3)4Cl2 solution with certain concentration as a packaging solution; (3) synthesizing a Pd-Ag/KA molecular sieve with a microwave heating method; (4) performing high-temperature hydrogen purging reduction to successfully e prepare the KA molecular sieve with two kinds of precious metal: Ag and Pd packaged. The pore diameter of the molecular sieve prepared with the preparation method is about 3*10 m, the specific surface area can reach 240 m /g or larger, the pore structure is stable, and Ag and Pd particles are successfully packaged in a KA molecular sieve cage. The molecular sieve efficiently removes the elemental mercury in natural gas at a high temperature, can prevent the poisoning damage of H2S, and can be heated and recycled.

Preparation method of sulfur-tolerant renewable molecular sieve for removing elemental mercury in natural gas

The invention discloses a high-sulphur coal pyrolysis device and method based on secondary catalytic tempering, and belongs to the technical field of high-sulphur coal pyrolysis. High-temperature pyrolysis gas generated after pyrolysis through a pyrolytic reaction unit passes through a cyclone separator and then enters the bottom of a moving-bed reactor, high-temperature semicoke enters the moving-bed reactor from a semicoke storage tank, the high-temperature pyrolysis gas flows back and makes contact with semicoke particles in the moving-bed reactor, reducing gas contained in the pyrolysis gas reacts with sulphur in the semicoke under the high temperature condition, most sulphur in the semicoke enters a gas phase in the form of H2S, and thus the effects of dust removing and catalytic tempering of a high-temperature semicoke bed layer are achieved at the same time; after the high-temperature coal gas passes through the cyclone separator and the semicoke bed layer in sequence, fine dust in the coal gas can be completely filtered out under the high temperature condition, and thus the purpose of high-temperature dust removing is achieved. Part of heavy tar in the high-temperature pyrolysis gas is pyrolysed into light oil under the catalysis of the high-temperature semicoke, and thus the quality of pyrolysis oil is improved.

High-sulphur coal pyrolysis device and method based on secondary catalytic tempering

The invention discloses a method for preparing a silver-loaded hydrogen sulfide poisoning-resistant 4A molecular sieve from attapulgite serving as a raw material, and belongs to the technical field ofpreparation of a molecular sieve. The method comprises the following steps: firstly, pretreating the attapulgite; mixing the pretreated attapulgite and an alkali liquid and performing microwave heating; preparing a sodium aluminate solution, performing crystallization, and performing silver loading on the 4A molecular sieve obtained through crystallization through supercritical carbon dioxide; and finally obtaining the silver-loaded 4A molecular sieve. The silver-loaded 4A molecular sieve prepared by the method is applied to mercury removing experiment under the simulated natural gas atmosphere, and the 4A molecular sieve with the silver loaded quantity of 1.5 percent is selected. The silver is loaded by other loading methods, the mercury removing efficiency experiment is conducted underthe atmosphere of different H2S concentration through comparison, and the experiment proves that the silver-loaded 4A molecular sieve has high mercury removing efficiency and has H2S poisoning resistance. The silver-loaded molecular sieve can maintain high mercury removing efficiency under the atmosphere containing H2S.

Liang Peng

Papers

In situ pyrolysis of Ce-MOF to prepare CeO2 catalyst with obviously improved catalytic performance for toluene combustion

Inhibitory effects of water vapor on elemental mercury removal performance over cerium-oxide-modified semi-coke

Preparation method of sulfur-tolerant renewable molecular sieve for removing elemental mercury in natural gas

High-sulphur coal pyrolysis device and method based on secondary catalytic tempering

Method for preparing silver-loaded hydrogen sulfide poisoning-resistant 4A molecular sieve from attapulgite serving as raw material