Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40th anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are dee...

Fundamentals and Catalytic Applications of CeO2-Based Materials

There is increased recognition by the world’s scientific, industrial, and political communities that the concentrations of greenhouse gases in the earth’s
atmosphere, particularly CO_2, are increasing. For
example, recent studies of Antarctic ice cores to
depths of over 3600 m, spanning over 420 000 years,
indicate an 80 ppm increase in atmospheric CO_2 in
the past 200 years (with most of this increase
occurring in the past 50 years) compared to the
previous 80 ppm increase that required 10 000 years.2
The 160 nation Framework Convention for Climate
Change (FCCC) in Kyoto focused world attention on
possible links between CO2 and future climate change
and active discussion of these issues continues.3 In
the United States, the PCAST report4 “Federal
Energy Research and Development for the Challenges
of the Twenty First Century” focused attention
on the growing worldwide demand for energy and the
need to move away from current fossil fuel utilization.
According to the U.S. DOE Energy Information
Administration,5 carbon emission from the transportation
(air, ground, sea), industrial (heavy manufacturing,
agriculture, construction, mining, chemicals,
petroleum), buildings (internal heating, cooling, lighting),
and electrical (power generation) sectors of the
World economy amounted to ca. 1823 million metric
tons (MMT) in 1990, with an estimated increase to
2466 MMT in 2008-2012 (Table 1).

Catalysis Research of Relevance to Carbon Management: Progress, Challenges, and Opportunities

http://pubs.acs.org/doi/pdfplus/10.1021/cr500486u

Recent Developments in the Synthesis of Supported Catalysts

The E factor 25 years on: the rise of green chemistry and sustainability

Catalytic partial oxidation of methane has been reviewed with an emphasis on the reaction mechanisms over transition metal catalysts. The thermodynamics and aspects related to heat and mass transport is also evaluated, and an extensive table on research contributions to methane partial oxidation over transition metal catalysts in the literature is provided. Presented are both theoretical and experimental evidence pointing to inherent differences in the reaction mechanism over transition metals. These differences are related to methane dissociation, binding site preferences, the stability of OH surface species, surface residence times of active species and contributions from lattice oxygen atoms and support species. Methane dissociation requires a reduced metal surface, but at elevated temperatures oxides of active species may be reduced by direct interaction with methane or from the reaction with H, H2, C or CO. The comparison of elementary reaction steps on Pt and Rh illustrates that a key factor to produce hydrogen as a primary product is a high activation energy barrier to the formation of OH. Another essential property for the formation of H2 and CO as primary products is a low surface coverage of intermediates, such that the probability of O–H, OH–H and CO–O interactions are reduced. The local concentrations of reactants and products change rapidly through the catalyst bed. This influences the reaction mechanisms, but the product composition is typically close to equilibrated at the bed exit temperature.

A review of catalytic partial oxidation of methane to synthesis gas with emphasis on reaction mechanisms over transition metal catalysts

XRD and LRS were used to characterize both supported and unsupported catalysts derived from VO(H2PO4)2. Supported VO(H2PO4)2-derived catalysts were found to be more active but slightly less selective in butane oxidation to maleic anhydride than unsupported samples, but the difference in selectivity could be eliminated by adding a small amount of phosphorus to the supported samples. For butane oxidation, the activity of the catalysts was much enhanced by the presence of α1-VOPO4. The relative rates of oxidation of propane, butane, and pentane were consistent with alkane activation occurring predominantly at the secondary carbon.

Alkane oxidation over bulk and silica-supported VO(H2PO4)2-derived catalysts

Silica-supported vanadium oxide catalysts with different BET areas have been used in partial oxidation of methane to formaldehyde. The BET area of the silica support not only plays an important role in the activation of methane but also in promoting the degradation of reaction intermediates. A reaction scheme is proposed where HCHO and CO2 are primary products, whereas CO is a secondary product from the degradation of formaldehyde and hydrocarbons. A large BET area led to degradation of hydrocarbons to CO, whereas on low-BET-area catalysts, this side reaction is partially inhibited with the simultaneous formation of C2 hydrocarbons. The general trend observed is that the activity decreases with decreasing BET areas. Gas-phase reactivity increases the initial activation of methane, but does not increase the degradation of reaction intermediates as much as surface area does thus providing a selective activation for methane.

Partial oxidation of methane on silica-supported vanadia catalysts. the relevance of catalyst bet area and gas-phase activation

Stepwise methane to methanol conversion: Effect of copper loading on the formation of active species in copper-exchanged mordenite

Direct synthesis of Cu supported on mesoporous silica: Tailoring the Cu loading and the activity for ethanol dehydrogenation

A process for preparing copper-based, zirconia-supported catalysts, useful for obtaining ethyl acetate from ethyl alcohol The catalysts of the invention show increasing asymptotic conversion of ethyl alcohol into ethyl acetate with increasing content of low-temperature reduced copper oxide species The process for obtaining ethyl acetate comprises directing a stream 2 of fresh ethyl alcohol through a reactor 7 laden with the inventive catalyst, under reaction conditions of temperature between 180°C and 360°C, pressure between 1 and 2 atmospheres and residence time factor W/F 20 to 600 Kg-catalystmin/Kg-ethyl alcohol, obtaining a product stream 8 at the outlet of reactor 7 that is cooled in a heat exchanger system 9, where it is separated into a liquid product stream 18 and gaseous product stream 10 Stream 10 yields mainly acetaldehyde, stream 16, and hydrogen, stream 14, both streams being recyclable to reactor 7 Alternatively, acetaldehyde can be stored in tank 17 Liquid stream 18, containing desired end products and by-products, is refined in 19 and the ethyl acetate product is stored in tank 21 while the by-product stream is directed to tank 23

José Maria C. Bueno

Papers

Alkane oxidation over bulk and silica-supported VO(H2PO4)2-derived catalysts

Partial oxidation of methane on silica-supported vanadia catalysts. the relevance of catalyst bet area and gas-phase activation

Stepwise methane to methanol conversion: Effect of copper loading on the formation of active species in copper-exchanged mordenite

Direct synthesis of Cu supported on mesoporous silica: Tailoring the Cu loading and the activity for ethanol dehydrogenation

Copper-based catalysts, process for preparing same and use thereof