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

Numerous industrial approaches input large quantities of power to achieve a desired outcome. The question is whether that power is most efficiently transformed into process to achieve the specific purpose of heat, mass transfer, mixing etc. To optimize heat/mass transfer, small scale eddies should have maximum energy and they should be close to the interface. In contrast, optimum mixing performance is achieved by large eddies distributed uniformly over entire volume of contactor. In summary, the 'Energy budget'; i.e. how the supplied energy is distributed between eddies of different sizes is very important. Such a distribution is represented by the turbulent energy spectrum. In the current work, we utilize high speed particle image velocimetry (PIV) to record the variation of liquid velocity over a plane in time-resolved fashion. The local energy spectrum is obtained by taking FFT of velocity time series at each point in planar PIV data. A model energy spectrum by Pope ('Turbulent Flows' Cambridge University Press, 2000) was fitted to experimental spectrum giving the energy flux (equivalent to the turbulent energy dissipation rate) at each point. The salient feature of this method is the ability to calculate local energy dissipation rate without using the estimates of velocity gradients. The results obtained in current work are less susceptible to the noise in PIV velocity data. The local energy spectrum and energy dissipation rate measurements will enable us to put a close check on the energy budget in the process equipment. It will allow tailoring the turbulence to the specific application, significantly enhancing the operating efficiency.

Evaluation of local energy dissipation rate using time resolved PIV

Light-weight thermal insulating fly ash cenosphere ceramics

Underutilization of bubble column reactors due to desorption

Deformation and optics based structural design and cost optimization of cylindrical reflector system

Solid state decomposition studies of Low and High Density Polyethylene (LDPE and HDPE) have been carried out in the present work. Thermo-gravimetric analysis (TGA) is utilized to determine the degradation kinetics for pure plastic samples at different heating rates. The distribution of activation energy values and rates estimated using various Iso-conversional methods have been selected on basis of correlation coefficients. For LDPE, isoconversional method of Friedman and for HDPE Flynn Wall Ozawa methods are used to estimate the distribution of activation energies having their mean values as 256.5 and 257.2 kJ/mol respectively. The inputs from Isoconversional methods are used to determine decomposition behavior with Criado method. Model based studies performed with Criado method identifies the solid-state degradation follows contracting volume-sphere (R3) model based on lower statistical parameter values. The identified decomposition model is validated by Coats Redfern method which also results in lower statistical parameter values. This is further validated through a best fit of extent of reaction profile against temperature, substantiating the solid-state decomposition model followed by given plastic fractions.

Jyeshtharaj B. Joshi

Papers

Evaluation of local energy dissipation rate using time resolved PIV

Light-weight thermal insulating fly ash cenosphere ceramics

Underutilization of bubble column reactors due to desorption

Deformation and optics based structural design and cost optimization of cylindrical reflector system

Elucidation of Thermal Degradation Model for Low and High Density Polyethylene by Statistical Parameters