Single enzyme nanoparticle for biomimetic CO<Subscript>2</Subscript> sequestration

Nanoparticle technology is being increasingly used in environmental sciences. We prepared single enzyme nanoparticle (SEN) by modifying the surface of carbonic anhydrase (CA) with a thin layer of organic/inorganic hybrid polymer. SEN-CA appears to be improving the stability of free enzyme. CA, as ubiquitously found enzyme, is involved in gaseous CO₂ sequestration and is being looked as a promising candidate for combating global warming. We report here physical characterization of SEN-CA using transmission electron microscope (TEM), Fourier-transform infrared analysis (FTIR), X-ray diffraction analysis (XRD), and energy dispersive X-ray (EDX). Average size of SEN-CA particles appears to be in the range of 70–80 nm. We also report the effect of SEN formation on the kinetic parameters of free CA such as Michaelis–Menten constant (K _m), maximum reaction velocity (V _max), and storage stability of free CA and SEN-CA. The V _max of SEN-CA (0.02857 mmol/min/mg) and free enzyme (0.02029 mmol/min/mg) is almost similar. K _m has decreased from 6.143 mM for SEN-CA to 1.252 mM for free CA. The stabilization of CA by SEN formation results in improved the half-life period (up to 100 days). The formation of carbonate was substantiated by using gas chromatography (GC). The conversion of CO₂ to carbonate was 61 mg of CaCO₃/mg of CA and 20.8 mg of CaCO₃/mg of CA using SEN-CA and free CA, respectively.     

理论研究二氧化碳在有机吸收剂1，3-二苯胍中的氢键相互作用

如今碳捕获和储存技术已得到了迅速发展以减少对环境的二氧化碳排放. 研究发现胺基有机分子溶剂能有效地吸收二氧化碳,并通过氢键和二氧化碳形成的碳酸氢盐相互作用. 最近,实验报道了一种1,3-二苯基胍溶液,在室温条件下能捕获环境中的二氧化碳并将其转化为有价值的化学品. 然而,1,3-二苯基胍分子在溶液状态下如何与二氧化碳相互作用的机理仍不清楚. 在这项工作中,利用分子动力学方法模拟研究了溶液相中1,3-二苯基胍分子与二氧化碳的复杂作用细节. 模拟结果表明,质子化的1,3-二苯基胍分子和碳酸氢根离子倾向通过不同的双氢键模式作用形成稳定的复合物. 精确的密度泛函方法计算表明,这些双氢键复合物在热力学上相当稳定. 本研究有助于理解溶液相中1,3-二苯基胍分子中催化转化二氧化碳的机理.     

18O/16O and 13C/12C Fractionation During the Reaction of Carbonates with Phosphoric Acid: Effects of Cationic Substitution and Reaction Temperature

Abstract

The factors for ¹⁸O/¹⁶O fractionation between carbonates and CO₂ gas produced by the dissolution of the carbonates in phosphoric acid (sealed vessel method) have been investigated as a function of reaction temperature (20–90°C) and cationic substitution in the solid. Synthetic CaCO₃, Ca_0.75 Mn_0.25 CO₃, MnCO₃, BaCO₃ and SrCO₃ powders, and a natural kutnahorite sample were used as solids. The δ¹⁸O values of the gaseous CO₂ liberated by the reaction with phosphoric acid decrease with increasing temperature and seem to be a linear function of T(°K)^?2. The slopes are specific for different carbonates. No temperature-depended ¹³C/¹²C fractionation seems to exist.     

CO2 capture by Li‐functionalized silicene

CO₂ capture and storage technology is of key importance to reduce the greenhouse effect. By its large surface area and sp³ hybridization, Li‐functionalized silicene is demonstrated to be a promising CO₂ absorbent that is stable up to at least 500 K and has a very high storage capacity of 28.6 mol/kg (55.7 wt%). The adsorption energy of CO₂ on Li‐functionalized silicene is enhanced as compared to pristine silicene, to attain an almost ideal value that still facilitates easy release. In addition, the band gap is found to change sensitively with the CO₂ coverage. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Combustion processes for carbon capture

A review of the technologies for coal-based power generation closest to commercial application involving carbon capture is presented. Carbon capture and storage (CCS) developments are primarily adaptations of conventional combustion systems, with additional unit operations such as bulk oxygen supply, CO₂ capture by sorbents, CO₂ compression, and storage. They use pulverized coal combustion in entrained flow—the dominant current technology for coal-based power, or gasification in entrained flow, although similar concepts apply to other solid-gas contacting systems such as fluidized beds. Currently, the technologies have similar generation efficiencies and are associated with efficiency penalties and electricity cost increases due to operations required for carbon capture. The R&D challenges identified for the combustion scientist and engineer, with current understanding being detailed, are those of design, optimisation and operational aspects of new combustion and gasification plant, controlling the gas quality required by CCS related units and associated emission compliance, and gas separations. Fundamental research needs include fuel reactions at pressure, and in O₂/CO₂ atmospheres, as few studies have been made in this area. Laboratory results interpreted and then included in CFD models of combustion operations are necessary. Also identified, but not detailed, are combustion issues in gas turbines for IGCC and IGCC-CCS. Fundamental studies should be a component of pilot-plant and demonstrations at practical scale being planned. Concepts for new designs of combustion equipment are also necessary for the next generation of technologies. The challenges involved with the design and operation of these integrated systems, while supplying electricity on demand, are considerable.     

Computational investigation of the performance of ZIF-8 with encapsulated ionic liquids towards CO2 capture*

The effect of Ionic Liquid (IL) encapsulation in Metal Organic Frameworks (MOFs) is extensively studied towards the enhancement of the MOFs as CO₂-selective materials. The influence of the IL anion-cation pair type is investigated through the combination of two different cations, namely 1-butyl-3-methylimidazolium [bmim⁺] and 1-octyl-3-methylimidazolium [omim⁺] and three distinct anions, namely bis-trifluoromethylsulfonyl-imide [Tf₂N^?], tricyanomethanide [TCM^?], and tertracyanoborate [B(CN)₄^?], that can be encapsulated in ZIF-8, resulting in a series of ZIF hybrids (IL@ZIF-8). The study investigates the impact of the anion and the cation on the separation of CO₂ from mixtures with CH₄ and N₂. Monte Carlo simulations of adsorption of the three gases in both the pristine ZIF-8 and in ILs@ZIF-8 reveal that CO₂ capacity increases dramatically for the case of ILs@ZIF-8. Moreover, analysis of the simulations and additional density functional theory calculations show that CO₂/CH₄ (related to natural gas purification) and CO₂/N₂ (related to post-combustion CO₂ capture) mixture selectivity is affected by the distribution, composition and type of the IL pair. Moreover, the sorbent selection parameter, S, and the regenerability factor, R, are used to evaluate the performance of all IL@ZIF-8 analogues along with other known CO₂-selective materials.     

Raman Spectrum of the Split ν4 Mode of CO[dbnd] 3 Ions in Aragonite

Infrared and Raman spectra of CO^[dbnd] ₃ ions are different in the two crystallographic forms of CaCO₃ Calcite and Aragonite owing to their different site symmetries. Due to this fact, i.r. has been used to assess the reversible Calcite ← → Aragonite transformation which occurs upon grinding of CaCO₃, and much work has been done in this field in the last few years^(1-4). In the present paper data are reported on Raman spectra of Calcite and Aragonite forms of CaCO₃ produced by the above mechanical procedure.     

Nanoporous carbon microspheres as anode material for enhanced capacity of lithium ion batteries

Nanoporous carbon microspheres (NCMs) are prepared by a one-step carbonizing and activating resorcinol?formaldehyde polymer spheres (RFs) in inert and CO₂ atmosphere for anode materials of lithium-ion batteries (LIBs). Compared with RFs carbon microspheres (RF-C), after activating with hot CO₂, the NCMs with porous structure and high BET surface area of 2798.8 m² g^?1, which provides abundant lithium-ion storage site as well as stable lithium-ion transport channel. When RF-C and NCM are used to anode material for LIBs, at the same current density of 210 mA g^?1, the initial specific discharge capacity are 482.4 and 2575.992 mA h g^?1, respectively; after 50 cycles, the maintain capacity are 429.379 and 926.654 mA h g^?1, respectively. The porous spherical structure of NCM possesses noticeably lithium-ion storage capability, which exhibits high discharge capacity and excellent cycling stability at different current density. The CO₂ activating carbonaceous materials used in anode materials can tremendously enhance the capacity storage, which provides a promising modification strategy to improve the storage capacity and cyclic stability of carbonaceous anode materials for LIBs.     

CO2 dissociation on rhodium: Measurement of the specific rates on Rh(111)

The measured rates for CO₂ dissociation on Rh(111) are reported for a $\text{H}{}_2\text{CO}{}_2$ reaction mixture at a total pressure of 100 Torr and a CO₂ partial pressure of 1 Torr. The activation energy associated with the conversion of CO₂ to CO is $\text{17}\text{kcal}\text{mol}$. The reaction probabilities for CO₂ dissociation range from 10^?5 at 750 K to 10^?8 at 444 K. The probability of CO₂ dissociation on Rh(111) is shown to be on the order of 10^?11 at 300 K rather than the previously reported value near 10^?1.     

The Nanosecond Laser Flash Photolysis (LFP) Transient Spectra of Aqueous CCl4 Solution

Abstract

The Raman spectrum of polycrystalline vaterite is presented and compared to spectra of calcite and aragonite, the other two common CaCO₃ polymorphs; Raman spectroscopy easily distinguishes between these three polymorphs. An important feature of the Raman spectrum of vaterite is splitting of both the ν₁ and ν₄ peaks. The splitting of the ν1 peak implies two distinct site symmetries for the CO₃ ^?2 groups. A definitive crystal structure determination of vaterite is not yet available, but none of the three proposed structures for vaterite show such a feature.     

The 13C bicarbonate method: an inverse end product method for measuring CO2 production and energy expenditure

We reconsider the principle of the ¹³C bicarbonate (NaH¹³CO₃) method (¹³C-BM) for the determination of the CO₂ production to obtain an estimate of energy expenditure (EE). Its mathematical concept based on a three-compartmental model is related to the [¹⁵N]glycine end product method. The CO₂ production calculated by the ¹³C-BM, R_aCO₂(¹³C) is compared to the result from the indirect calorimetry, RCO₂(IC). In an interspecies comparison (dog, goat, horse, cattle, children, adult human; body mass ranging from 15 to 350?kg, resting and fasting conditions) we found an excellent correlation between the results of ¹³C-BM and IC with RCO₂(IC)?=?0.703?×?R_aCO₂(¹³C), (R²?=?0.99). The slope of this correlation corresponds to the fractional ¹³C recovery (RF(¹³C)) of ¹³C in breath CO₂ after administration of NaH¹³CO₃. Significant increase in RF(¹³C) was found in physically active dogs (0.95?±?0.14; n?=?5) vs. resting dogs (0.71?±?0.10, n?=?17; p?=?.015). The ¹³C recovery in young bulls was greater in blood CO₂ (0.81?±?0.05) vs. breath CO₂ (0.73?±?0.05, n?=?12, p?<?.001) and in ponies with oral (0.76?±?0.03, n?=?8) vs. intravenous administration of NaH¹³CO₃ (0.69?±?0.07; n?=?8; p?=?.026). We suggest considering the ¹³C-BM as a ‘stand-alone’ method to provide information on the total CO₂ production as an index of EE.     

Effect of high CO2 concentration on char formation through mineral reaction during biomass pyrolysis

O₂/CO₂ combustion has attracted considerable attention as a promising technology for CO₂ capture. Using biomass for fuel is considered carbon neutral, and O₂/CO₂ biomass combustion can mitigate the deleterious environmental effect of greenhouse. In this study, the effect of CO₂, the main component gas in O₂/CO₂ combustion, on the pyrolysis characteristics of biomass is investigated. Cellulose, lignin, and metal-depleted lignin pyrolysis experiments were performed using a thermobalance. Information on the surface chemistry of the chars was obtained by Fourier transform infrared (FTIR) spectroscopy to investigate changes in the surface chemistry during pyrolysis under different surrounding gasses. When the temperature increased to 1073 K at heating rate of 1 K s^?1, the char yield of lignin in the presence of CO₂ increased by about 10% compared with that under Ar. However, for cellulose and metal-depleted lignin, no significant difference appeared between pyrolysis under CO₂ and that under Ar. FT-IR showed that a strong peak corresponding to carbonate ions appeared in the char derived from lignin under CO₂. Therefore, salts such as Na₂CO₃ or K₂CO₃ formed during the lignin pyrolysis under CO₂. At around 1650–1770 cm^?1, a significant difference appeared in the FTIR spectra of chars formed under CO₂ and those formed under Ar. C=O groups not associated with an aromatic ring were found only in chars formed under CO₂. It was suggested that these salts affected the char formation reaction, in that the char formed during lignin pyrolysis under CO₂ had unique chemical bands that did not appear in the lignin-derived char prepared under Ar.     

Cauliflower-derived porous carbon without activation for electrochemical capacitor and CO<Subscript>2</Subscript> capture applications

Carbon materials have attracted great attention in CO₂ capture and energy storage due to their excellent characteristics such as tunable pore structure, modulated surface properties and superior bulk conductivities, etc. Biomass, provided by nature with non-toxic, widespread, abundant, and sustainable advantages, is considered to be a very promising precursor of carbons for the view of economic, environmental, and societal issues. However, the preparation of high-performance biomass-derived carbons is still a big challenge because of the multistep process for their synthesis and subsequent activation. Herein, hierarchically porous structured carbon materials have been prepared by directly carbonizing dried cauliflowers without any addition of agents and activation process, featuring with large specific surface area, hierarchically porous structure and improved pore volume, as well as suitable nitrogen content. Being used as a solid-state CO₂ adsorbent, the obtained product exhibited a high CO₂ adsorption capacity of 3.1 mmol g^?1 under 1 bar and 25 °C and a remarkable reusability of 96.7% retention after 20 adsorption/regeneration cycles. Our study reveals that choosing a good biomass source was significant as the unique structure of precursor endows the carbonized product with abundant pores without the need of any post-treatment. Used as an electrode material in electrochemical capacitor, the non-activated porous carbon displayed a fairly high specific capacitance of 228.9 F g^?1 at 0.5 A g^?1 and an outstanding stability of 99.2% retention after 5000 cycles at 5 A g^?1.

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Graphical abstract Hierarchically porous structured carbon materials are prepared by directly carbonizing dried cauliflower without any agents and process of activation for high performance of CO₂ capture and capacitor.

     

Matrix-isolation study of the vibrational spectrum and structure of the CO3− radical anion

Charge-transfer interaction processes which occur upon codeposition at 14°K of an Ar:CO₂:N₂O or an Ar:CO:O₂ mixture with an atomic beam of potassium lead to the stabilization of CO₃^? in the solid deposit. Infrared spectroscopic data require a C_2v structure for this molecule. Although the deviation of the structure from the expected D_3h symmetry may result in part from Jahn-Teller distortion, cation interactions have been found to play a significant role. Evidence is presented for the initial formation of CO₃^? with trigonal symmetry. Upon mercuryarc irradiation of the deposit, absorptions due to CO₃^?2 grow in importance.     

Bifunctional Au-nanorod@Fe3O4 nanocomposites: synthesis, characterization, and their use as bioprobes

Membrane gas separation technology has been rapidly growing for industrial applications such as air separation, carbon dioxide (CO₂) separation from natural gas production, hydrogen separation, etc. Needs for CO₂ separation are increasing as carbon capture technology has been recognized as an essential part when combating the global warming issue. Membrane gas separation technology deals with mass transport phenomena through the membrane engineered on a sub-nanoscale controlling transport properties of small gas molecules such as CO₂, N₂, O₂, H₂, etc. In this review, we will report on the recent developments in capture technologies utilizing various membranes including nano-engineered thermally rearranged (TR) polymers. TR polymer membranes show high gas permeability as well as good separation properties, especially in CO₂ separation processes such as from post-combustion flue gas and natural gas sweetening.     

Crystallization Fouling in Experimental Micro Heat Exchangers—Optical and Thermal Investigations

The intention of this work is the basic investigations of the fouling behavior in micro heat exchangers. Therefore fouling experiments with calcium carbonate (CaCO₃) in an experimental micro heat exchanger were carried out and observed with a digital microscope. The investigations included local temperature measurements confirmed by computational fluid dynamics simulation as well as optical visualization of the fouling process inside the microchannels. The detected fouling resistances R _f were in the range of 10^?5–10^?4 m₂ K W^?1. Cleaning in place was possible and also optically observed.     

1,3‐Bis(2′‐hydroxyethyl)imidazolium ionic liquids: correlating structure and properties with anion hydrogen bonding ability

A series of 1,3‐bis(2′‐hydroxyethyl)imidazolium ionic liquids is reported where ¹H NMR chemical shift values and thermal stabilities (T_d), as determined by thermogravimetric analysis, are correlated with the hydrogen bonding capability of various anions ([Cl^?], [Br^?], [CF₃CO₂^?], [NO₂^?], [MsO^?], [NO₃^?], [TfO^?], [BF₄^?], [NTf₂^?], and [PF₆^?]). Use of anions with the strongest hydrogen bonding capability, such as chloride [Cl^?], bromide [Br^?], and trifluoroacetate [CF₃CO₂^?], led to the furthest observed downfield chemical shift values in DMSO‐d₆ and the poorest thermal stabilities ([CF₃CO₂^?] < 200 °C). Thermal stabilities in excess of 350 °C and upfield chemical shift values were observed for ionic liquids, which employed the weakly coordinating triflate [OTf^?], tetrafluoroborate [BF₄^?], or bis(trifluoromethylsulfonyl)imide [NTf₂^?] anion. Optimized structures of selected ionic liquids, as determined by density functional theory calculations at the B3LYP/6‐31G + (d,p) level, indicated that the anion preferred to be located above the imidazolium ring and in close proximity to the hydroxyl groups. Calculated dissociation energies (ΔE) and a comparison of key bonding distances (C2―H, (C2)H···X, O―H, and (O)H···X) also confirmed this structural preference. Copyright © 2013 John Wiley & Sons, Ltd.     

Conference Reports

Abstract

One purpose of new land use concepts for degraded fens (organic soils with high N content) is the reduction of the mineralization process due to very high groundwater levels. However, knowledge of nitrogen mineralization process (net and gross) in degraded fen soils affected by reflooding is very small. Therefore, the objectives of our study were (a) to evaluate the suitability of ¹⁵N pool dilution method for measurements of gross mineralization rates in degraded fen soils and (b) to investigate how the reflooding of a degraded fen affects the net and gross nitrogen mineralization in a short-term incubation experiment. The usability of the ¹⁵N pool dilution method was diminished by the low recovery of the applied ¹⁵NH₄ ^? at time zero. The recovery of the added ¹⁵NH₄ ^? in the extractable soil NH₄ ^? pool was only 13.5% for the drained soil and 59.6% for the reflooded soil. However, the gross mineralization rates were similar for both soils and exceeded always the net rates substantially. The cumulative net mineralization rate was higher for the reflooded soil (1.58 μg N?cm^?3?d^?1) than for the drained soil (-0.67 μg N?cm^?3?d^?1). Differences between the two soils were also found in the nitrification intensity and the loss of ¹⁵N. This was probably one reason for the higher net mineralization rate in the reflooded soil.     

Zwei-Phononen-Absorptionsspektren und Dispersion der Schwingungszweige in Kristallen der Kalkspatstruktur

Polarized reflection spectra between 4.000 and 20 cm^?1 and absorption spectra (at temperatures of liquid helium) between 2.000 and 650 cm^?1 have been measured of the isomorphous crystals NaN0₃, CaCO₃, MgCO₃ (D _3d ⁶ ) and of CaMg (CO₃)₂ (C _3i ² ). The wavenumbers of the fundamental infrared transitions and of the two-phonon-combinations have been determined. The combinationbands show a structure, which allows some insight into the wavevector dispersion of the phonon branches of these crystals. Selection rules have been worked out for several points in the interior and on the border of the Brillouin zone. By comparison with the spectra they give evidence for the presence of critical points of the phonon-branches for wavevectors parallel to the trigonal axis of the crystal.     

SCF-Xα studies of the electronic structures of C,Si and Ge oxides

SCF-Xα scattered wave cluster MO calculations are presented for the oxyanions CO₃^?2, CO₄^?4, SiO₃^?2, SiO₄^?4, SiO₆^?8, GeO₄^?4 and GeO₆^?8. A comparison of the calculations with available X-ray spectral data shows good agreement. The MO diagrams for CO₃^?2 and CO₄^?4 are found to be quite similar, suggesting that the four coordinate oxyanion is not inherently unstable; therefore a quartz polymorph of CO₂ may become stable at high pressure. On the other hand, the valence region width of SiO₃^?2 is much smaller than that of SiO₄^?4; thus the three-coordinate Si oxyanion is expected to be highly unstable. For the Ge oxyanions the average valence region width is substantially larger in the six-coordinate than in the four-coordinate form, suggesting a preference for octahedral coordination. These observations indicate that although the valence region width is only one factor affecting the total energy of a system, it is predictive of favored coordination number according to the following principle: a change from a higher to a lower coordination number oxyanion of a given cation, Mⁿ⁺, will be favorable if the lower coordinate form has a wider valence region at its equilibrium internuclear distance.