Recent developments on carbon capture and storage: An overview

Flue gas adsorption on periodic mesoporous phenylene-silica: a DFT approach

Periodic mesoporous organosilicas (PMOs) were suggested as potential adsorbents for CO2/CH4 separation because of their large affinities towards CO2 and low interaction with CH4. Herewith, we present a comprehensive computational study on the binding properties of flue gas species with the pore walls of periodic mesoporous phenylene-silica (Ph-PMO) for understanding the possible impact of other gaseous species in the CO2/CH4 separation. The calculations considered three exchange-correlation functionals (PBE, PBE-D2 and M06-2X) based on the density functional theory and the walls of the periodic mesoporous phenylene-silica were modelled within the cluster model approach. The components of the flue gas considered were the diatomic CO, H2, N2, O2 and NO molecules, the triatomic CO2, H2O, H2S and SO2 species, the tetratomic SO3 and NH3 gases and the pentatomic CH4 molecule. The calculated data demonstrate that the presence of H2O, SO2, NH3, H2S and SO3 is a significant threat to CO2 capture by Ph-PMO and suggest that the Ph-PMO material would present high selectivity for CO2 over CH4, CO, H2 or N2 adsorption. The adsorption behaviour of flue gas components in Ph-PMO can be directly related to the experimental proton affinities, basicities or even the polarizabilities of the gaseous molecules.

Effective Conversion of Amide to Carboxylic Acid on Polymers of Intrinsic Microporosity (PIM-1) with Nitrous Acid

Carboxylate-functionalised polymers of intrinsic microporosity (C-PIMs) are highly desirable materials for membrane separation applications. The recently reported method to afford C-PIMs was via an extensive base hydrolysis process requiring 360 h. Herein, a novel and effective method to convert PIM-CONH₂ to C-PIM using nitrous acid was studied. The chemical structure of C-PIM was characterised by ¹H NMR, ¹³C NMR, FTIR, elemental analysis, UV-Vis, TGA and TGA-MS. Complete conversion from amide to carboxylic acid groups was confirmed. Decarboxylation of C-PIM was also successfully studied by TGA-MS for the first time, with a loss of m/z 44 amu (CO₂) observed at the first degradation stage. TGA also revealed decreased thermal stability of C-PIM relative to PIM-CONH₂ under both N₂ and air atmosphere_. Gel permeation chromatography (GPC) analysis showed continuous molecular weight degradation of C-PIM with extended reaction time. Aromatic nitration was also observed as a side reaction in some cases.

Piperazinium-mediated crosslinked polyimide-polydimethylsiloxane (PI-PDMS) copolymer membranes: the effect of PDMS content on CO2 separation

Polyimide-polydimethylsiloxane copolymer membranes crosslinked with piperazinium were prepared for high performance CO₂ separation.

Carbon Dioxide Capture Adsorbents: Chemistry and Methods

Excess carbon dioxide (CO₂ ) emissions and their inevitable consequences continue to stimulate hard debate and awareness in both academic and public spaces, despite the widespread lack of understanding on what really is needed to capture and store the unwanted CO₂ . Of the entire carbon capture and storage (CCS) operation, capture is the most costly process, consisting of nearly 70 % of the price tag. In this tutorial review, CO₂ capture science and technology based on adsorbents are described and evaluated in the context of chemistry and methods, after briefly introducing the current status of CO₂ emissions. An effective sorbent design is suggested, whereby six checkpoints are expected to be met: cost, capacity, selectivity, stability, recyclability, and fast kinetics.

A Model to Stabilize CO2 Uptake Capacity during Carbonation-Calcination Cycles and its Case of CaO-MgO

Nowadays, capturing anthropogenic CO₂ in a highly efficient and cost-effective way is one of the most challenging issues. Herein, the key parameters to stabilize CO₂ uptake capacity have been studied based on four kinds of pure calcium oxides (CaO) prepared by a simple calcination method with four different calcium precursors. A simple ideal particle model was proposed to illustrate the uniform distribution of pure CaO, in which the CO₂ uptake capacity is positively related with surface area of CaO particles and the stability is opposite to the distance between two CaO particles after carbonation. The adsorption capacity of the best sample with a distance of 398 nm between two CaO particles after carbonation only lost 0.344% per cycle, which is originated from the low possibility of the agglomeration between neighboring particles. On the basis of the proposed model, the composite with magnesium oxide (MgO) distributed uniformly in CaO was fabricated by a simple ball milling method, which possessed an excellent stability with a decay rate of only 3.9% over 100 carbonation-calcination cycles. In this case, MgO played as inert to increase the distance between CaO particles for agglomeration prevention.

Mechanisms of absorption and desorption of CO2 by molten NaNO3-promoted MgO

We present details of the mechanism of absorption and desorption of carbon dioxide by molten NaNO₃-promoted MgO and their implications for the applications of alkali nitrate-promoted MgO absorbents with many repeated absorption and desorption cycles.

Photothermal catalytic activity of combustion synthesized LaCoxFe1−xO3 (0 ≤ x ≤ 1) perovskite for CO2 reduction with H2O to CH4 and CH3OH

A range of LaCo_xFe_1−xO₃ perovskites with different Co-doping at the B-site were successfully synthesized via a sol–gel combustion route.

Influence of phase connectivity on the relationship among capillary pressure, fluid saturation, and interfacial area in two-fluid-phase porous medium systems

Multiphase flows in porous medium systems are typically modeled at the macroscale by applying the principles of continuum mechanics to develop models that describe the behavior of averaged quantities, such as fluid pressure and saturation. These models require closure relations to produce solvable forms. One of these required closure relations is an expression relating the capillary pressure to fluid saturation and, in some cases, other topological invariants such as interfacial area and the Euler characteristic (or average Gaussian curvature). The forms that are used in traditional models, which typically consider only the relationship between capillary pressure and saturation, are hysteretic. An unresolved question is whether the inclusion of additional morphological and topological measures can lead to a nonhysteretic closure relation. Relying on the lattice Boltzmann (LB) method, we develop an approach to investigate equilibrium states for a two-fluid-phase porous medium system, which includes disconnected nonwetting phase features. A set of simulations are performed within a random close pack of 1964 spheres to produce a total of 42 908 distinct equilibrium configurations. This information is evaluated using generalized additive models to quantitatively assess the degree to which functional relationships can explain the behavior of the equilibrium data. The variance of various model estimates is computed, and we conclude that, except for the limiting behavior close to a single fluid regime, capillary pressure can be expressed as a deterministic and nonhysteretic function of fluid saturation, interfacial area between the fluid phases, and the Euler characteristic. To our knowledge, this work is unique in the methods employed, the size of the data set, the resolution in space and time, the true equilibrium nature of the data, the parametrizations investigated, and the broad set of functions examined. The conclusion of essentially nonhysteretic behavior provides support for an evolving class of two-fluid-phase flow in porous medium systems models.

Atmospheric CO2 capture by algae: Negative carbon dioxide emission path

Carbon dioxide is one of the most important greenhouse gas, which concentration increase in the atmosphere is associated to climate change and global warming. Besides CO2 capture in large emission point sources, the capture of this pollutant from atmosphere may be required due to significant contribution of diffuse sources. The technologies that remove CO2 from atmosphere (creating a negative balance of CO2) are called negative emission technologies. Bioenergy with Carbon Capture and Storage may play an important role for CO2 mitigation. It represents the combination of bioenergy production and carbon capture and storage, keeping carbon dioxide in geological reservoirs. Algae have a high potential as the source of biomass, as they present high photosynthetic efficiencies and high biomass yields. Their biomass has a wide range of applications, which can improve the economic viability of the process. Thus, this paper aims to assess the atmospheric CO2 capture by algal cultures.

Biorefineries of carbon dioxide: From carbon capture and storage (CCS) to bioenergies production

Greenhouse gas emissions have several adverse environmental effects, like pollution and climate change. Currently applied carbon capture and storage (CCS) methods are not cost effective and have not been proven safe for long term sequestration. Another attractive approach is CO2 valorization, whereby CO2 can be captured in the form of biomass via photosynthesis and is subsequently converted into various form of bioenergy. This article summarizes the current carbon sequestration and utilization technologies, while emphasizing the value of bioconversion of CO2. In particular, CO2 sequestration by terrestrial plants, microalgae and other microorganisms are discussed. Prospects and challenges for CO2 conversion are addressed. The aim of this review is to provide comprehensive knowledge and updated information on the current advances in biological CO2 sequestration and valorization, which are essential if this approach is to achieve environmental sustainability and economic feasibility.

Evaluation of photosynthetic efficacy and CO2 removal of microalgae grown in an enriched bicarbonate medium

Bicarbonate species in the aqueous phase is the primary source for CO₂ for the growth of microalgae. The potential of carbon dioxide (CO₂) fixation by Chlorella pyrenoidosa in enriched bicarbonate medium was evaluated. In the present study, effects of parameters such as pH, sodium bicarbonate concentration and inoculum size were assessed for the removal of CO₂ by C. pyrenoidosa under mixotrophic condition. Central composite design tool from response surface methodology was used to validate statistical methods in order to study the influence of these parameters. The obtained results reveal that the maximum removal of CO₂ was attained at pH 8 with sodium bicarbonate concentration of 3.33 g/l, and inoculum size of 30 %. The experimental results were statistically significant with R ² value of 0.9527 and 0.960 for CO₂ removal and accumulation of chlorophyll content, respectively. Among the various interactions, interactive effects between the parameters pH and inoculum size was statistically significant (P < 0.05) for CO₂ removal and chlorophyll accumulation. Based on the studies, the application of C. pyrenoidosa as a potential source for carbon dioxide removal at alkaline pH from bicarbonate source is highlighted.

Direct mineral carbonation of steelmaking slag for CO2 sequestration at room temperature

Rapid increase of CO2 concentration in the atmosphere has forced the international community towards adopting actions to restrain from the impacts of climate change. Moreover, in India, the dependence on fossil fuels is projected to increase in the future, implying the necessity of capturing CO2 in a safe manner. Alkaline solid wastes can be utilized for CO2 sequestration by which its disposal issues in the country could also be met. The present work focuses to study direct mineral carbonation of steelmaking slag (SS) at room temperature and low-pressure conditions (<10 bar). Direct mineral carbonation of SS was carried out in a batch reactor with pure CO2 gas. The process parameters that may influence the carbonation of SS, namely, CO2 gas pressure, liquid to solid ratio (L/S) and reaction time were also studied. The results showed that maximum sequestration of SS was attained in the aqueous route with a capacity of 82 g of CO2/kg (6 bar, L/S ratio of 10 and 3 h). In the gas-solid route, maximum sequestration capacity of about 11.1 g of CO2/kg of SS (3 bar and 3 h) was achieved indicating that aqueous route is the better one under the conditions studied. These findings demonstrate that SS is a promising resource and this approach could be further developed and used for CO2 sequestration in the country. The carbonation process was evidenced using FT-IR, XRD, SEM and TG analysis.