Behavior of active sites on Cr-MCM-41 catalysts during the dehydrogenation of propane with CO2

Environmental problems associated with volatile organic compounds (VOCs) in the atmosphere have provided the driving force for sustained fundamental and applied research in the area of environmental remediation. Conventional methods currently used to treat VOCs include incineration, condensation, adsorption, and absorption. Incineration and condensation are cost-effective only for moderate to high VOC concentrations. Adsorption and absorption do not destroy VOCs but simply transfer them to another medium. The humid gas stream can plug the condenser and can fill up the adsorption site of the adsorbent. However, none of these methods are cost-effective for the treatment of gas streams with low to moderate concentration and having large numbers of compounds, as the recovery and reuse of the compounds is not economically feasible. A host of alternative remediation technologies, which offer a number of advantages over conventional technologies, are emerging. These include treatment of VOCs with spark-generated...

Emerging Control Technologies for Volatile Organic Compounds

Aerogels are an exceptional class of materials which are of interest for several high-performance applications thanks to their extraordinary physical properties such as extremely high porosity, high specific surface area, and extremely low density combined with very versatile synthesis approaches. Since their invention by S. Kistler, various aerogels have been explored for catalytic and photocatalytic applications, though in the recent decades, several breakthroughs regarding different aspects ranging from more efficient catalysis in organic synthesis, energy-related processes, and catalytic environmental depollution by aerogels have been made. For both, catalytic and photocatalytic performances, aerogel monoliths prepared from sol–gel approaches accompanied with an appropriate drying technique, in particular supercritical point drying, have become striking alternative catalysts or catalyst supports compared to the presently used ones prepared from traditional wet synthesis approaches. In this article, aerogels in environmental remediation processes as heterogeneous catalyst and photocatalyst for depollution of air and aqueous media are fully addressed, and recent achievement in this context is thoroughly reviewed.

Current Status, Opportunities and Challenges in Catalytic and Photocatalytic Applications of Aerogels: Environmental Protection Aspects

Transition-Metal-Substituted Titania-Loaded MCM-41 as Photocatalysts for the Degradation of Aqueous Organics in Visible Light

https://www.lehigh.edu/operando/Publications/2002%20Oxidative%20Dehydrogenation%20of%20Propane%20over%20Supported%20Chromia%20Catalysts%20-%20Influence%20of%20Oxide%20Supports%20and%20Chromia%20Loading.pdf

Oxidative Dehydrogenation of Propane over Supported Chromia Catalysts: Influence of Oxide Supports and Chromia Loading

A series of 13 bulk transition metals oxides frequently used as components of full oxidation catalysts was tested in air oxidation of n-butane and ethylacetate (EA). Co3O4, Cr2O3, CuO and MnO2,displayed the best activity, about one order of magnitude higher than the others. Chromia displayed the highest CO2 productivity. The activity and CO2 selectivity of Cr2O3 catalyst deposited on mineral supports (SiO2, Al2O3, MCM-41) depended strongly on the supports nature, texture and chromia loading. XPS, EDAX, XRD, FTIR and TPR–TPO measurements displayed two forms of Cr3+-oxide on silica-supported catalysts: bulk α-Cr2O3 nanocrystals of 10–20 nm and a monolayer of chromia surface species chemically bonded to the support: –Si–O–CrO. The chromia nanocrystals detected by XRD displayed higher activity and selectivity in complete EA oxidation due to higher redox mobility of chromium cations on their surface compared with grafted chromium silicate species. The optimized Cr2O3/SiO2 catalyst showed high efficiency in wet oxidation of amino-3-phosphonopropionic acid, comparable with the best catalysts reported in the literature.

F. Rodrigues

Papers

Supported chromia catalysts for oxidation of organic compounds