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

Effect of bubble on the pressure spectra of oscillating grid turbulent flow at low Taylor-Reynolds number

Study of crystal growth and effect of temperature and mixing on properties of sodium diuranate

The present paper is concerned with the modelling of continuous and semi-batch reactors where the rate controlling step is associated with the solid phase. When the solid phase is continuous, the conversion depends upon the solid phase concentration profiles and the solid phase axial dispersion. It has been shown that the concentration profiles strongly depend upon the construction and design of the inlet and outlet. Several possibilities of the design of end connections have been analysed and their role in deciding the concentration profiles has been brought out. Sedimentation-diffusion model has been used to predict the concentration profiles. The solid phase dispersion coefficient depends upon column diameter, superficial gas and liquid velocities, particle size and density, fractional phase hold-ups and the rise velocity of a bubble. The extent of contribution of these variables has been analysed on the basis of the energy balance and a unique correlation has been proposed for the solid phase axial dispersion coefficient. A criterion has been developed to predict the condition under which the solid phase concentration becomes uniform throughout the reactor. It has been pointed out that the particle settling velocity in a three phase sparged reactor (VR ) is markedly different from the terminal settling velocity (Vs.) and the hindered settling velocity in solid-liquid dispersions. The value of VR is the most important variable to affect the solid phase concentration profile and mixing. A treatise on the effect of various variables on VR is presented. In order to put the resistance (associated with the solid phase) in a proper perspective, the conversion-time relationships were analysed for a single reacting particle. Several reaction mechanisms were considered. For instance, (i) gas-liquid mass transfer controlled, (ii) solid-liquid mass transfer controlled, (iii) mass transfer with chemical reaction in solid-liquid and gasliquid films, (iv) ash diffusion controlled, (v) surface reaction controlled, (vi) simultaneous reaction and diffusion within the particle, (vii) bubbles reacting in the solid-liquid film and many other mechanisms have been considered and conversion-time relationships have been derived. A classification of reaction mechanisms has been presented on the basis of conversion-time relationship. The solid phase conversion in a continuous reactor has been found on the basis of exit age distribution and conversion-time relationship for single particles. Performance charts have been constructed showing the relationship between conversion and the solid phase Peclet number, residence time and the time required for complete conversion for a single particle. These charts 283 Vol 3, Not. 3 A4.1985 Modelling of Three Phase Sparged Reactors have been constructed for a wide range of variables and are expected to be useful for design engineers. A discussion has been presented on co-current versus counter-current operation and the effects of superficial gas and liquid velocities, particle settling velocity on solid phase conversion. A systematic procedure has been presented for using the performance charts for complex situations such as those involving dissolving particles. Gas-liquid-solid iluidized beds and spouted beds are operated in a semibatch manner. In this case the solid phase is batch whereas the gas phase is continuous. Generalized models have been developed for two situations: (i) resistance associated with the solid-liquid film and (ii) resistance associated with the gas-liquid film. These generalized models have been simplified for different limiting conditions. In order to prove the validity of these models, experimental data on carbonation of lime have been analysed. The effects of solid loading, superficial gas velocity, partial pressure of carbon dioxide have been considered. The carbonation was found to proceed through a constant rate period and a falling rate period. The theoretical predictions were found to agree with the experimental findings. A comparison between the semi-batch and continuous modes of operation has been presented. It has been shown that the semi-batch mode of operation is likely to be advantageous in a variety of situations and a few examples of industrial importance have been worked out. Specific recommendations have been made for the future work.

Modelling of Three Phase Sparged Reactors

• Liquid phase exfoliation of graphite was assessed. • Variables affecting physicochemical properties and exfoliation rate were summarized. • The step-wise mechanism have been discussed to understand the rate-limiting step. • The role of graphene and its derivatives upon epoxy based coatings and composite were explored. • At the end, the challenges and future roadmap have been mentioned. The present review paper emphasizes liquid-phase exfoliation (LPE) of graphene and its derivatives with the focus mainly on electrochemical exfoliation, mechanical exfoliation, and chemical exfoliation. A careful analysis of literature data on the above processes has been carried out in this review, which gives an insight into rate-controlling factors in LPE. The mechanism for each exfoliation process has been discussed. Based on these inputs, the scale-up methodology is proposed. Reduced GO (rGO) are synthesized by mainly two routes i.e. thermal and chemical. The scope and limitation of both routes are discussed in brief. Further, the applications of functionalized graphene and GO in the polymer matrix composite have been elucidated. How the bonding of the epoxy group with the functional group present on graphene affects the strength and permeation properties of epoxy composites have been explained in this review. The advantages of modifications of graphene are discussed in detail to understand the mechanism for industrial development. A future roadmap has been proposed based on the existing knowledge gap. 

Jyeshtharaj B. Joshi

Papers

Effect of bubble on the pressure spectra of oscillating grid turbulent flow at low Taylor-Reynolds number

Study of crystal growth and effect of temperature and mixing on properties of sodium diuranate

Modelling of Three Phase Sparged Reactors

Exfoliated graphene and its derivatives from liquid phase and their role in performance enhancement of epoxy matrix composite

Modelling of Three Phase Sparged Catalytic Reactors