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

The fractional dispersed phase hold-up and mass transfer coefficients were measured in modified spray columns of 50 mm i.d. using an aqueous two phase system of polyethylene glycol (PEG 4000)-sodium sulphate-buffer. The mass transfer coefficients were measured for amyloglucosidase and β-galactosidase. Both co-current and countercurrent modes of operation were investigated.



The dispersed phase hold-up (ϵD) and the dispersed phase and the continuous phase mass transfer coefficients (kDa, kCa) increased with increasing dispersed phase velocity. An increase in the phase concentration of sodium sulphate and PEG was found to reduce ϵD, kDa, and kCa. The performance of the modified spray column is compared with the conventional spray column. The modifications resulted into about a ten-fold enhancement in the throughput and about a five-fold reduction in the value of the height of a transfer unit (HTU ). It has been shown that the value of HTU of the order of 1 m can be obtained. Empirical correlations for ϵD and kDa, kCa have been proposed.



Les coefficients fractionnels de retention et de transfert de matiere de la phase dispersee ont ete mesures dans des colonnes d'atomisation modifiees de 50 mm de diametre interieur a l'aide d'un systeme biphasique aqueux de polyethylene glycol (PEG 4000)-sulfate de sodium-tampon. Les coefficients de transfert de matiere ont ete mesures pour l'amyloglucosidase et β-galactosidase. Les modes de fonctionnement a cocourant et a contre-courant ont ete etudies.



La retention de phase dispersee (ϵD) et les coefficients de transfert de matiere des phases dispersee et continue (kDa, kCa) augmentent avec la vitesse de la phase dispersee. On a trouve qu'une augmentation de la concentration de phase de sulfate de sodium et de PEG conduisait a une diminution de ϵD, kDa, et kCa. La performance de la colonne d'atomisation modifiee est comparee a celle de la colonne conventionnelle. Les modifications ont permis d'ameliorer la capacite d'environ un facteur dix et de reduire la hauteur equivalente a une unite de transfert (HTU) d'environ un facteur cinq. On montre qu'une valeur de HTU de l'ordre de 1 m peut ětre obtenue. Des correlations sont proposees pour ϵD, kDa et kCa.

Enzyme mass transfer coefficient in aqueous two‐phase systems: Modified spray extraction columns

Study of the Changes in Composition of Ammonium Diuranate with Progress of Precipitation, and Study of the Properties of Ammonium Diuranate and its Subsequent Products Produced from both Uranyl Nitrate and Uranyl Fluoride Solutions

Design, optimization and optical performance study of tripod heliostat for solar power tower plant

Some design features of radial baffles in sectionalised bubble columns

In the present work, the flow pattern in pipe flow has been simulated using a low-Reynolds-number k-e model. The model has been extended to predict the heat-transfer coefficient in regions of both high and low Prandtl number. The computational fluid dynamic (CFD) approach has been shown to be superior to the conventional semiempirical approach for high turbulent Prandtl numbers and in cases where the molecular properties such as diffusivity and viscosity steeply change in the vicinity of the wall.

Jyeshtharaj B. Joshi

Papers

Enzyme mass transfer coefficient in aqueous two‐phase systems: Modified spray extraction columns

Study of the Changes in Composition of Ammonium Diuranate with Progress of Precipitation, and Study of the Properties of Ammonium Diuranate and its Subsequent Products Produced from both Uranyl Nitrate and Uranyl Fluoride Solutions

Design, optimization and optical performance study of tripod heliostat for solar power tower plant

Some design features of radial baffles in sectionalised bubble columns

CFD simulation of heat transfer in turbulent pipe flow