Over the past several years, cerium oxide and CeO2-containing materials have come under intense scrutiny as catalysts and as structural and electronic promoters of heterogeneous catalytic reactions. Recent developments regarding the characterization of ceria and CeO2-containing catalysts are critically reviewed with a special focus towards catalyst interaction with small molecules such as hydrogen, carbon monoxide, oxygen, and nitric oxide. Relevant catalytic and technological applications such as the use of ceria in automotive exhaust emission control and in the formulation of SO x reduction catalysts is described. A survey of the use of CeO2-containing materials as oxidation and reduction catalysts is also presented.

Catalytic Properties of Ceria and CeO2-Containing Materials

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

Advanced oxidation processes (AOP) for water purification and recovery

Since the time of the industrial revolution, the atmospheric CO(2) concentration has risen by nearly 35 % to its current level of 383 ppm. The increased carbon dioxide concentration in the atmosphere has been suggested to be a leading contributor to global climate change. To slow the increase, reductions in anthropogenic CO(2) emissions are necessary. Large emission point sources, such as fossil-fuel-based power generation facilities, are the first targets for these reductions. A benchmark, mature technology for the separation of dilute CO(2) from gas streams is via absorption with aqueous amines. However, the use of solid adsorbents is now being widely considered as an alternative, potentially less-energy-intensive separation technology. This Review describes the CO(2) adsorption behavior of several different classes of solid carbon dioxide adsorbents, including zeolites, activated carbons, calcium oxides, hydrotalcites, organic-inorganic hybrids, and metal-organic frameworks. These adsorbents are evaluated in terms of their equilibrium CO(2) capacities as well as other important parameters such as adsorption-desorption kinetics, operating windows, stability, and regenerability. The scope of currently available CO(2) adsorbents and their critical properties that will ultimately affect their incorporation into large-scale separation processes is presented.

Adsorbent Materials for Carbon Dioxide Capture from Large Anthropogenic Point Sources

Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.

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Carbon capture and storage (CCS): the way forward

Simultaneous measurement of phase velocities in dispersed two-phase flows has been carried out using a laser Doppler velocimeter. For this purpose, axial and radial components of instantaneous velocity and the cross-correlation of these two components were measured. The dispersed phase has been isolated on the basis of threshold values of crosscorrelation. The method accurately predicts the number, size, and slip velocity of the dispersed phase (bubbles and particles) in dilute dispersions. In dense gas-liquid dispersions, a procedure has been given for the estimation of local fractional gas hold-up and the individual phase velocities.

Hydrodynamic characterization of dispersed two-phase flows by laser doppler velocimeter

Simulation of NOx gas absorption under adiabatic condition and comparison with plant data

Effect of agitator design on hydrodynamics and power consumption in mechanically agitated gas-liquid reactors

The purpose of this work was to establish the pyrolysis kinetics of agricultural biomass residues (mustard husk (MH), cotton stalk (CS), and groundnut shell (GNS)) using thermogravimetric analysis (TGA). TGA is carried out at different heating rates (5, 10, 30, and 50 K/min) under inert conditions in the temperature range of 303–1173 K. The iso-conversional methods of Friedman, Kissinger-Akahira-Sunose, and Flynn-Wall-Ozawa were used to estimate the activation energy of the decomposition process. The Criado method, Coats-Redfern Method, and Direct Differential methods were used to model the kinetics, with the latter two methods providing a closer fit with the experimental data. The kinetics of thermal degradation were separately studied for three temperature zones represented as drying, active, and passive zones. The results of Coats-Redfern and Direct Differential methods showed that (i) the nth-order reaction model is applicable for all the samples with order of reaction in the active zone being around ~ 2.0–3.0, ~ 2.5–3.0, and ~ 3.0 for MH, CS, and GNS, respectively, and (ii) the D-3 model is applicable for all the samples in the passive zone.

Jyeshtharaj B. Joshi

Papers

Hydrodynamic characterization of dispersed two-phase flows by laser doppler velocimeter

Simulation of NOx gas absorption under adiabatic condition and comparison with plant data

Effect of agitator design on hydrodynamics and power consumption in mechanically agitated gas-liquid reactors

Kinetic modelling for thermal decomposition of agricultural residues at different heating rates

Kinetics of reverse water‐gas shift reaction over Pt/Al2O3 catalyst