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

Mesopore-modified zeolites: preparation, characterization, and applications.

A large number of studies can be found in the literature regarding the production of new catalysts for methanol steam reforming. This work summarizes the latest developments on catalysts for this application and is divided in two main groups: copper-based and group 8–10 metal-based catalysts. In each section, the strategies proposed by several authors to enhance the performance of the catalysts are described. An overall comparison between the two groups shows that copper-based catalysts are the most active ones, while the 8–10 group catalysts present better results in terms of thermal stability and long-term stability. Very promising results were reported for both groups, enhancing the value of methanol as a hydrogen carrier for fuel cell applications.

Catalysts for methanol steam reforming—A review

Sulfur compounds represent one of the most common impurities present in the crude oil. Sulfur in liquid fuel oil leads directly to the emission of SO2 and sulfate particulate matter (SPM) that endangers public health and community property; and reduces the life of the engine due to corrosion. Furthermore, the sulfur compounds in the exhaust gases of diesel engines can significantly impair the emission control technology designed to meet NOx and SPM emission standards. The research efforts for developing conventional hydrodesulfurization and alternative desulfurization methods such as selective adsorption, biodesulfurization, oxidation/extraction (oxidative desulfurization), etc. for removing these refractory sulfur compounds from petroleum products are on the rise. Research laboratories and refineries are spending huge amounts of money in finding a viable and feasible solution to reduce sulfur to a concentration of less than 10 mg l−1. This paper reviews the current status in detail of various desulphurization techniques being studied worldwide. It presents an overview of novel emerging technologies for ultra-deep desulfurization so as to produce ultra-low-sulfur fuels.

An evaluation of desulfurization technologies for sulfur removal from liquid fuels

The application of templating methods to produce zeolite materials with hierarchical bi- or trimodal pore size distributions is reviewed with emphasis on mesoporous materials. Hierarchical zeolite materials are categorized into three distinctly different types of materials: hierarchical zeolite crystals, nanosized zeolite crystals, and supported zeolite crystals. For the pure zeolite materials in the first two categories, the additional meso- or macroporosity can be classified as being either intracrystalline or intercrystalline, whereas for supported zeolite materials, the additional porosity originates almost exclusively from the support material. The methods for introducing mesopores into zeolite materials are discussed and categorized. In general, mesopores can be templated in zeolite materials by use of solid templating, supramolecular templating, or indirect templating. In this categorization of templating methods, the nature of the interface between the zeolite crystal and the mesopore exactly when...

Templating mesoporous zeolites

The effect of the support, Al 2 O 3 , ZrO 2 , and SiO 2 , on the activity for CO oxidation of a series of CuO and CeO 2 monometallic and bimetallic catalysts was studied. The catalysts were prepared by coimpregnation of the support with the adequate amount of Cu and Ce nitrates to obtain a loading of 2% Cu and/or 8% Ce. It was found that the support has a strong influence on the activity of the different bimetallic catalysts. Interestingly, the SiO 2 supported catalyst shows the higher activity. The bimetallic supported catalysts follow the activity sequence CuO–CeO 2 /SiO 2  > CuO–CeO 2 /ZrO 2  > CuO–CeO 2 /Al 2 O 3 . In the absence of CeO 2 , the most active monometallic catalyst was the CuO/ZrO 2 system. The different degree of interaction between CuO and CeO 2 particles, induced by the support, can explain the activity results for the bimetallic catalysts.

CuO and CeO2 catalysts supported on Al2O3, ZrO2, and SiO2 in the oxidation of CO at low temperature

The activity of the various CuO species found in supported copper catalysts and the effect of the presence of reaction products, CO2 and H2O, was studied during the complete oxidation of methane. Series of copper catalysts supported on ZrO2 ,A l 2O3 and SiO2 with different metal concentrations were analyzed under identical experimental conditions of reactant concentration and temperature. The catalysts were characterized by TPR, UV–vis spectroscopy and XRD. The results show that the activity of supported CuO is closely related to the kind of Cu species formed on the different supports. It was found that the Cu species formed on ZrO2 and Al2O3 are dependent on the metal loading/support’s surface area ratio, and that the activity of highly dispersed Cu is substantially higher than that of bulk CuO. In the case of silica, only the formation of bulk CuO was detected, accounting for the low activity of CuO/SiO2 catalysts. The activity of highly dispersed Cu species formed on ZrO2 is higher than those formed over Al2O3, and it is not significantly affected by the formation of bulk CuO on the surface. On the contrary, the activity of copper species formed on alumina decreases continuously as the Cu loading is increased. Thus, for the range of copper loading studied in this work, the activity of the catalysts, per gram of loaded Cu, follows the sequence: CuO/ZrO2 > CuO/Al2O3 � CuO/SiO2. It was also found that CO2 does not inhibits the activity of the CuO/ZrO2 catalysts, while water inhibits the combustion reaction of methane, with an estimated reaction order of about � 0.2 for temperatures between 360 8C and 420 8C. # 2007 Elsevier B.V. All rights reserved.

Effect of copper species and the presence of reaction products on the activity of methane oxidation on supported CuO catalysts

http://repositorio.uchile.cl/bitstream/handle/2250/125054/Baeza_P.pdf?sequence=1

Desulfurization by adsorption with copper supported on zirconia

A hydrotreated TiO2 supported potassium catalyst, K/TiHT, was studied on the transesterification reaction of canola oil for the production of biodiesel. It was found that the calcination at different temperatures led to the transformation of the supported potassium catalyst into a titanate form of oxide. This was accompanied by a substantial increase in activity. Leaching studies found that although some potassium and titania was left in the products, the reaction mainly occurred in heterogeneous conditions. The contribution of the leached components to the activity was only minor. The recovered catalyst was then used in successive reactions producing stable conversions. A maximum conversion was achieved with the catalyst calcined at 700 °C. Optimum reaction conditions were obtained when using a catalyst loading of 6% (w/w), a methanol to oil ratio of 54:1, and a temperature of reaction of 55 °C.

Study of potassium-supported TiO2 catalysts for the production of biodiesel

The combustion of methane has been studied over 1% Pd catalysts supported on commercial silica with different hydrophobicity, prepared by chlorine free precursors. It was found that, when no water is added to the feed, the degree of hydrophobicity of the silica does not affect significantly the behavior of the catalysts. The results show that the activation and deactivation processes are similar for both catalysts. Furthermore, contrary to what is observed on Pd/Al2O3 and Pd/ZrO2 catalysts, the apparent reaction order with respect to water for Pd/SiO2 catalysts is −0.25. When water is added to the feed, however, the different hydrophobicity of the supports affects the inhibition produced by the adsorption of water on the catalytic surface. Regardless of the hydrophobicity of the support, the addition of water also speeds up the deactivation process of the Pd catalysts supported on silica.

Paulo Araya

Papers

CuO and CeO2 catalysts supported on Al2O3, ZrO2, and SiO2 in the oxidation of CO at low temperature

Effect of copper species and the presence of reaction products on the activity of methane oxidation on supported CuO catalysts

Desulfurization by adsorption with copper supported on zirconia

Study of potassium-supported TiO2 catalysts for the production of biodiesel

Methane combustion over Pd/SiO2 catalysts with different degrees of hydrophobicity