The escalating level of atmospheric carbon dioxide is one of the most pressing environmental concerns of our age. Carbon capture and storage (CCS) from large point sources such as power plants is one option for reducing anthropogenic CO(2) emissions; however, currently the capture alone will increase the energy requirements of a plant by 25-40%. This Review highlights the challenges for capture technologies which have the greatest likelihood of reducing CO(2) emissions to the atmosphere, namely postcombustion (predominantly CO(2)/N(2) separation), precombustion (CO(2)/H(2)) capture, and natural gas sweetening (CO(2)/CH(4)). The key factor which underlies significant advancements lies in improved materials that perform the separations. In this regard, the most recent developments and emerging concepts in CO(2) separations by solvent absorption, chemical and physical adsorption, and membranes, amongst others, will be discussed, with particular attention on progress in the burgeoning field of metal-organic frameworks.

Carbon Dioxide Capture: Prospects for New Materials

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

Post-combustion CO2 capture from the flue gas is one of the key technology options to reduce greenhouse gases, because this can be potentially retrofitted to the existing fleet of coal-fired power stations. Adsorption processes using solid sorbents capable of capturing CO2 from flue gas streams have shown many potential advantages, compared to other conventional CO2 capture using aqueous amine solvents. In view of this, in the past few years, several research groups have been involved in the development of new solid sorbents for CO2 capture from flue gas with superior performance and desired economics. A variety of promising sorbents such as activated carbonaceous materials, microporous/mesoporous silica or zeolites, carbonates, and polymeric resins loaded with or without nitrogen functionality for the removal of CO2 from the flue gas streams have been reviewed. Different methods of impregnating functional groups, including grafting techniques and modifying the support materials, have been discussed to en...

Post-Combustion CO2 Capture Using Solid Sorbents: A Review

Global warming resulting from the emission of greenhouse gases, especially CO2, has become a widespread concern in the recent years. Though various CO2 capture technologies have been proposed, chemical absorption and adsorption are currently believed to be the most suitable ones for post-combustion power plants. The operation of the chemical absorption process is reviewed in this work, together with the use of absorbents, such as the ionic liquid, alkanolamines and their blended aqueous solutions. The major concerns for this technology, including CO2 capture efficiency, absorption rate, energy required in regeneration, and volume of absorber, are addressed. For adsorption, in addition to physical adsorbents, various mesoporous solid adsorbents impregnated with polyamines and grafted with aminosilanes are reviewed in this work. The major concerns for selection of adsorbent, including cost, adsorption rate, CO2 adsorption capacity, and thermal stability, are compared and discussed. More effective and less energy-consuming regeneration techniques for CO2-loaded adsorbents are also proposed. Future works for both absorption and adsorption are suggested.

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A Review of CO2 Capture by Absorption and Adsorption

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Studies in Surface Science and Catalysis

Reversible adsorption of carbon dioxide on amine surface-bonded silica gel

Heavy oil molecular mixtures were investigated on the basis of single molecules resolved by atomic force microscopy. The eight different samples analyzed include asphaltenes and other heavy oil fractions of different geographic/geologic origin and processing steps applied. The collected AFM data of individual molecules provide information about the molecular geometry, aromaticity, the content of nonhexagonal rings, typical types and locations of heterocycles, occurrence, length and connectivity of alkyl side chains, and ratio of archipelago- vs island-type architectures. Common and distinguishing structural motifs for the different samples could be identified. The measured size distributions and the degree of unsaturation by scanning probe microscopy is consistent with mass spectrometry data presented herein. The results obtained reveal the complexity, properties and specifics of heavy oil fractions with implications for upstream oil production and downstream oil processing. Moreover, the identified molec...

Heavy Oil Based Mixtures of Different Origins and Treatments Studied by Atomic Force Microscopy

Opportunities of Downhole Dielectric Heating in Venezuela: Three Case Studies Involving Medium, Heavy and Extra-Heavy Crude Oil Reservoirs

A new method to evaluate the colloidal stability of crude oils and related products was developed on the basis of the evaluation of the solubility profile or solubility distribution of asphaltenes in these materials. The new method uses an on-column precipitation coupled with an evaporative light scattering detector (ELSD). The new method requires a small amount of sample, takes only 35 min to perform, and can work for asphaltene concentrations as low as 500 ppm. Using this method, different patterns for asphaltene solubility profile distributions were found depending upon the origin and processing history of the samples. Extracted asphaltenes from virgin and processed materials exhibit uni- and bimodal distributions, respectively. On-column precipitated asphaltenes usually have bimodal distributions, where the separation between the peaks is related to the colloidal stability of the asphaltenes. In general, asphaltenes from unstable materials are characterized by wider solubility profile distributions th...

Asphaltene Stability in Crude Oils and Petroleum Materials by Solubility Profile Analysis

Pipelining of heavy crudes can be facilitated by preparing oil-in-water (O/W) emulsions of the crude, but separation of the oil from the water after pipelining is problematic if conventional surfactants are used. Long-chain acetamidines are CO2-triggered switchable surfactants, being surface-active when CO2 is present but not when CO2 is absent. Unfortunately, in the presence of CO2, they stabilize water-in-oil (W/O) emulsions of heavy crude rather than the desired O/W emulsions. However, in the absence of added CO2, several compounds (Na2CO3, three of the long-chain acetamidines, and two other amidines) stabilize O/W emulsions. These low-viscosity emulsions can later be broken by the addition of CO2. The residual oil content in the recovered water is lowest if the compound used to stabilize the original emulsion was a long-chain acetamidine.

Cesar Ovalles

Papers

Reversible adsorption of carbon dioxide on amine surface-bonded silica gel

Heavy Oil Based Mixtures of Different Origins and Treatments Studied by Atomic Force Microscopy

Opportunities of Downhole Dielectric Heating in Venezuela: Three Case Studies Involving Medium, Heavy and Extra-Heavy Crude Oil Reservoirs

Asphaltene Stability in Crude Oils and Petroleum Materials by Solubility Profile Analysis

Use of CO2-Triggered Switchable Surfactants for the Stabilization of Oil-in-Water Emulsions