CO2 capture at high temperature using calcium-based sorbents

Calcium-based sorbents synthesized from CaO, CaCO₃, and Ca(OH)₂ precursors were demonstrated as high-temperature CO₂ capture materials. The effect on CO₂ capture capability of calcium-based sorbents receiving different activations was also investigated. After proper activation, the best carbon capturing material is CaO that captured 75% of available CO₂ in nine cyclic tests and captured 61% even after 40 cyclic experiments. The correlation of the structural difference in the three activated sorbents and CO₂ conversion has been discussed. The sintering effect is presumably a major cause for activity decline of calcium-based sorbents… after cyclic carbonation/decarbonation runs.     

Reforming natural gas for CO2 pre-combustion capture in combined cycle power plant

The aim of this study is to assess the conversion of a natural gas combined cycle power plant (NGCC) using an advanced gas turbine (GE9H) for CO₂ pre-combustion capture. The natural gas is reformed in an auto-thermal reformer (ATR) either with pure oxygen or with air. After water-shift conversion of CO into CO₂ and physical CO₂ recovery, the synthesis gas contains a high fraction of H₂. It is diluted with N₂ and steam to lower its low heating value (LHV) for NO _X emission control. Oxygen purity and reforming pressure have little impact on the performances. High-pressure reforming is preferred to reduce the process size. Air reforming results in a slightly higher efficiency but in a bigger process too. The CO₂ recovery rate has a big impact on the power plant efficiency since a lot of steam is required to lower the heating value (LHV) of the synthesis gas leaving the recovery process. Two values of LHV have been assessed. Steam consumption for natural gas reforming and synthesis gas dilution are the main consuming elements. An erratum to this article can be found at     

Reduction of greenhouse gases in integrated pulp and paper mills: possibilities for CO2 capture and storage

Earlier work has shown that capturing the CO₂ from flue gases in the recovery boiler at a market pulp mill can be a cost-effective way of reducing mill CO₂ emissions. In this paper, it is investigated whether the same is valid for an integrated pulp and paper mill. Five configurations are compared, supplying the extra energy needed by a biofuel boiler, an NGCC, a heat pump or by reducing the steam demand at the mill in combination with a biofuel boiler or an NGCC. The configurations have been evaluated with energy market scenarios and the avoidance cost has been calculated. The NGCC configurations have the lowest avoidance costs in all scenarios and they also have the advantage of liberating biofuel for use in other parts of society. An erratum to this article can be found at     

Clover leaf-shaped Al2O3 extrudate as a support for high-capacity and cost-effective CO2 sorbent

Amine-functionalized clover leaf-shaped Al₂O₃ extrudates (CA) were prepared for use as CO₂ sorbent. The as-synthesized materials were characterized by N₂ adsorption, XRD, SEM and elemental analysis followed by testing for CO₂ capture using simulated flue gas containing 15.1% CO₂. The results showed that a significant enhancement in CO₂ uptake was achieved with the introduction of amines into CA materials. A remarkably high volume-based capacity of 70.1 mg/mL of sorbent of this hybrid material suggests that it can be potentially used for CO₂ capture from flue gases and other stationary sources, especially those with low CO₂ concentration. The novel adsorbent reported here performed well during prolonged cyclic operations of adsorption-desorption of CO₂.     

Effect of amine structure on CO2 capture by polymeric membranes

Abstract

Poly(amidoamine)s (PAMAMs) incorporated into a cross-linked poly(ethylene glycol) exhibited excellent CO₂ separation properties over H₂. However, the CO₂ permeability should be increased for practical applications. Monoethanolamine (MEA) used as a CO₂ determining agent in the current CO₂ capture technology at demonstration scale was readily immobilized in poly(vinyl alcohol) (PVA) matrix by solvent casting of aqueous mixture of PVA and the amine. The resulting polymeric membranes can be self-standing with the thickness above 3 μm and the amine fraction less than 80 wt%. The gas permeation properties were examined at 40 °C and under 80% relative humidity. The CO₂ separation performance increased with increase of the amine content in the polymeric membranes. When the amine fraction was 80 wt%, the CO₂ permeability coefficient of MEA containing membrane was 604 barrer with CO₂ selectivity of 58.5 over H₂, which was much higher than the PAMAM membrane (83.7 barrer and 51.8, respectively) under the same operation conditions. On the other hand, ethylamine (EA) was also incorporated into PVA matrix to form a thin membrane. However, the resulting polymeric membranes exhibited slight CO₂-selective gas permeation properties. The hydroxyl group of MEA was crucial for high CO₂ separation performance.     

The clathrate hydrate process for post and pre-combustion capture of carbon dioxide

One of the new approaches for capturing carbon dioxide from treated flue gases (post-combustion capture) is based on gas hydrate crystallization. The basis for the separation or capture of the CO(2) is the fact that the carbon dioxide content of gas hydrate crystals is different than that of the flue gas. When a gas mixture of CO(2) and H(2) forms gas hydrates the CO(2) prefers to partition in the hydrate phase. This provides the basis for the separation of CO(2) (pre-combustion capture) from a fuel gas (CO(2)/H(2)) mixture. The present study illustrates the concept and provides basic thermodynamic and kinetic data for conceptual process design. In addition, hybrid conceptual processes for pre and post-combustion capture based on hydrate formation coupled with membrane separation are presented.     

Promotional effects of carbon nanotubes on V2O5/TiO2 for NOX removal

A series of V₂O₅/TiO₂-carbon nanotube (CNT) catalysts were synthesized by sol-gel method, and their activities for NO_X removal were compared. A catalytic promotional effect was observed by adding CNTs to V₂O₅/TiO₂. The catalyst V₂O₅/TiO₂-CNTs (10 wt.%) showed an NO_X removal efficiency of 89% at 300 °C under a GHSV of 22,500 h⁻¹. Based on X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, NH₃-temperature-programmed desorption, temperature-programmed reduction, Brunauer-Emmett-Teller surface area measurements, differential scanning calorimetry, and thermogravimetric analysis, the increased acidity and reducibility, which could promote NH₃ adsorption and oxidation of NO to NO₂, respectively, contributed to this promotion.     

Pressure influences on CO2 reaction with cyclohexylamine using ionic liquid as reaction medium and catalyst

Inserting carbon dioxide (CO₂) into ammonia molecules to produce urea is a traditional CO₂ utilization method. An ionic liquid (IL), 1-butyl-3-methylimidazolium bromide ([Bmim]Br), was used as reaction medium and [Bmim]Br/KOH as catalyst. This study investigates CO₂ carbonylation of cyclohexylamine and its reaction performance in a number of low- and high-pressure CO₂/IL systems. The reaction yield was greatly increased as pressure ranges changed from 15–50 bar to 80–100 bar; the physiochemical properties of substrates and catalyst were greatly affected by CO₂ in supercritical state. The yield was improved from 69% at 30 bar to 91.6% at 100 bar, much better than a previous study result of 53.5%, but as pressures further increased, a significant decrease was observed. The reaction activation energy was calculated to be 3.942 and 4.354 kcal/mol in mild and supercritical conditions. This process shows a low threshold reaction energy and great potential for industrial applications to store CO₂ in amine molecular structures.     

Catalytic reduction of CO2 to alcohol with Cu2Se-combined graphene binary nanocomposites

Photocatalytic reduction of CO₂ over a Cu₂Se–graphene nanocatalyst has been investigated. The nanocomposite material was successfully prepared via a modified hydrothermal method. The structure and properties of the prepared composite were characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray microscopy, transmission electron microscopy, Raman spectroscopic analysis, and X-ray photoelectron spectroscopy. A synergetic effect of the combination of Cu₂Se and graphene appeared in the form of excellent photocatalytic reduction capability of CO₂. The photocatalytic efficiencies of the samples were characterized by testing for the photoreduction of CO₂ to alcohol under visible light irradiation, which produced results such as to suggest that there is a significant potential for graphene-based semiconductor hybrid materials to be used as photocatalysts for reduction of CO₂.     

A study of parameters affecting the continuous CO2 laser cuts

Abstract

This work attempts to discover, by experimentation, some of the parameters governing cutting efficiency in perspex of a continuous CO₂ laser. The experimentation took the form of taking cuts in specimen pieces with the laser. While varying the parameters of speed of cut and position of the focal plane of the laser beam relative to the surface of the perspex, all other parameters were kept constant. These experiments produced conclusive ideas of the optimum position of the focal plane and the best speeds for cutting perspex at the same time producing the best cut quality obtainable. When the theoretically predicted minimum cut width is compared with the experimentally obtained results, the agreement is found to be almost exact.     

A study of uv preionization pulsed tea CO2 laser

Abstract

A uniform volumetric discharge was obtained by means of an auxiliary UV preionization in a home‐made TEA CO₂ laser. The maximum output pulse energy of this laser system was about 12J per pulse with a pulse duration of 80 ns. The ratio of electric field to neutral particle density (E/N) in this laser was 7.6×10^‐16 V cm². The peak power and pulse shape of the laser were studied. The time delay between the predischarge and the maindischarge during the stable operation of this laser system has also been studied. It was observed that the laser was operating with uniform glow discharges when the time delayed between the predischarge and the maindischarge was in the range of 1.0 μs to 6.0 μs. The spark array used as a preionizer for producing the UV radiation in this system is new, simple, durable, and can be easily fabricated.     

Synthesis and characterization of ZrO2 hollow spheres

ZrO₂ hollow microspheres with the average diameter of about 500 nm and the shell thickness of about 50 nm were synthesized by a facile technique using carbon spheres as templates. The corresponding ZrO₂ hollow microspheres were obtained by calcining the precursors of C-Zr(OH)₄ core-shell heterostructures, which were synthesized with the precipitation of ZrCl₄ solution with aqueous ammonia on the surface of colloid carbons. SEM, XRD, TGA and BET were used to characterize the composition, morphology, size and crystal structure of synthesized products. The effects of ultrasonic dispersion and separation process on the hollow spheres were studied, and the surfactant PEG-1000 was added to tune the shell structure of synthesized ZrO₂ hollow spheres.     

A simple ultrasono-synthetic route of PbSe-graphene-TiO2 ternary composites to improve the photocatalytic reduction of CO2

The present work investigates the photocatalytic reduction of CO₂ to CH₃OH with a PbSe-G-TiO₂ photocatalyst. A heterogeneous PbSe-G-TiO₂ nanocomposite was prepared via ultra-sonication and was characterized via XRD, SEM, HRTEM, Raman, XPS, and DRS measurements. The photocatalytic efficiencies of the prepared sample were further characterized by GC for the photoreduction of CO₂ to CH₃OH under UV and visible light. The prepared PbSe-G-TiO₂ ternary nanocomposites with an optimum GO loading of 6% exhibited outstanding photocatalytic activity (4.35 µmol g^?1 h^?1) after 48 hours of reaction. This indicated that the photocatalytic efficiency was mostly dependent on the weight ratio of graphene, sacrificial material Na₂SO₃/Na₂S, and the type of reactant. This work provides an accessible way to improve the response of a graphene-based TiO₂ photocatalyst to UV/visible light and to facilitate its application in environmental remediation.     

YBa2SnO5·5, a novel ceramic substrate for YBCO and BiSCCO superconductors

YBa₂SnO_5·5 has been synthesized and sintered as single phase material for its use as substrate for both YBCO and BiSCCO superconductors. YBa₂SnO_5·5 has a complex cubic perovskite (A₂BB’O₆) structure with the lattice constanta = 8·430 Å. The dielectric constant and loss factor of YBa₂SnO_5·5 are in a range suitable for its use as substrate for microwave applications. YBa₂SnO_5·5 is found to be chemically compatible with both YBCO and BiSCCO superconductors. The thick film of YBCO screen printed on polycrystalline YBa₂SnO_5·5 substrate gave aT _c(0) of 92 K and a critical current density (J _c) of 4 × 10⁴ A/cm² at 77 K. A screen printed BiSCCO thick film on YBa₂SnO_5·5 substrate gaveT _c(0) = 110 K and current density 3 × 10³ A/cm² at 77 K.     

Preparation and application of magnetic cobalt/SiO2 core/shell nanospheres

Homogeneous SiO₂-coated cobalt nanospheres with tunable silica shell thickness from 21.7 nm to 4.5 nm were synthesized by using modified Stöber method. These nanocomposites were used as source materials to prepare SiO₂ semi-hollow and hollow nanospheres by partially and completely etching cobalt cores, respectively. A proposed formation mechanism of these Co/SiO₂ nanospheres with a core/shell structure was presented in this paper, which is also important for the rational design and synthesis of other monodisperse core/shell nanoarchitectures with uniform size and shape. Furthermore, these Co/SiO₂ nanospheres were also used as a substrate for the deposition of CdS nanocrystals to prepare magnetic luminescent Co/SiO₂/CdS nanocomposites.     

Low temperature biomimetic synthesis of the Li2ZrO3 nanoparticles containing Li6Zr2O7 and high temperature CO2 capture

Li₂ZrO₃ nanoparticles containing Li₆Zr₂O₇ were prepared by a biomimetic soft solution route and characterized with X-ray diffraction (XRD), transmission electron microscope (TEM) and nitrogen adsorption. The results show that the tetragonal Li₂ZrO₃ nanoparticles containing monoclinic Li₆Zr₂O₇ can be obtained using this simple method. The mean diameter of the nanoparticles is approximately 90 nm and the corresponding specific surface area is 23.7 m² g^− 1. Moreover, the Li₂ZrO₃ nanoparticles obtained were thermally analyzed under a CO₂ flux to evaluate their CO₂ capture capacity at high temperature. It was found that the as-prepared Li₂ZrO₃ nanoparticles would be an effective acceptor for high temperature CO₂ capture.     

Electrochemical reduction of CO2 by Cu2O-catalyzed carbon clothes

Cu₂O cubes with average edge lengths of 640 nm were prepared by a chemical reduction approach. The as-synthesized Cu₂O particles were deposited on carbon clothes for electrochemical characterizations in cyclic voltammetry (CV) and potentiostatic measurements. In 0.5 M NaOH electrolytes saturated with N₂ or CO₂, both the Cu₂O and carbon clothes were stable at the potential range of 0 to − 1.7 V. Comparisons in the current responses from the CV and potentiostatic measurements suggested the Cu₂O with notable catalytic abilities for the CO₂ reduction. The mass activity was estimated at 0.94 mA/mg. Chemical analysis from gas chromatography confirmed the methanol to be the predominant product.     

Uniform lanthanide-doped Y2O3 hollow microspheres: Controlled synthesis and luminescence properties

Lanthanide-doped uniform pure cubic phase Y₂O₃ hollow microspheres have been successfully synthesized via a facile, high yield urea-based coprecipitation route with assistant of carbon spheres templates. The diameter and shell thickness of the microspheres can be manipulated by adjusting carbon sphere templates. Under a 980 nm excitation, Yb³⁺/Er³⁺, Er³⁺, Yb³⁺/Tm³⁺-doped Y₂O₃ hollow microspheres emit bright upconversion red, green, blue light with high purity, respectively, while Eu³⁺, Eu³⁺/Tb³⁺-doped Y₂O₃ hollow microspheres exhibit intense downconversion red light under the excitation of 254 nm ultraviolet light. Especially, the 610 nm emission intensity of Eu³⁺ in the Eu³⁺/Tb³⁺-codoped Y₂O₃ hollow microspheres is almost 5 times of that in the Y₂O₃:Eu³⁺ hollow microspheres indicating the occurring of the energy transfer from Tb³⁺ to Eu³⁺ ions.     

High power single mode output CO2 laser

Abstract

While attempting to reach TEMoo single mode high output power, the transverse discharge method was adopted. The optic axis, the direction of glow discharge and gas flow velocity are all mutually orthogonal. The discharge region has a 2.3 liter medium volume, and 100 m/sec gas flow. This small signal gain exceeds 0.8/m in the local region. We also adopted a stable multi‐path cavity for coordinating the larger volume laser medium. Under auxiliary discharge, the maximum output power can reach 1500W, at an efficiency of 9%.