MPa CO2 Pressure Research Articles

A novel acid catalyst based on super/subcritical CO 2 -enriched water for the efficient esterification of rosin

Rosin esters are widely applied as masticatory substances and beverage stabilizers, while classical acid-catalysed processes will lead to metal residue or environmental issues. Super/subcritical CO2–enriched high temperature liquid water (HTLW) as a green acid catalyst in the esterification reaction of rosin with glycerol was investigated. The pH of CO2–H2O binary system, as calculated based on gas–liquid equilibrium, charge balance and chemical equilibrium equations, ranged from 3.49 to 3.70 depending on the reaction conditions, indicating effective acid catalysis. Response surface methodology experiments showed the optimum conditions were 3.5 h, 3.9 MPa CO2 pressure, a rosin-to-glycerol molar ratio of 1.32 and 269°C, and an enhanced esterification yield of 94.74% was achieved, which was superior to that obtained using a ZnO catalyst. It was found that the esterification kinetics was a pseudo first-order reaction, and the enthalpy and entropy of activation were calculated using the Arrhenius–Polanyi equation. The presence of super/subcritical CO2-enriched HTLW catalyst can decrease the activation energy and significantly accelerate the reaction rate.

Swelling stress development in confined smectite clays through exposure to CO2

Recent work has shown that unconfined smectite clays swell upon exposure to supercritical (SC) CO2 due to uptake in the clay interlayer region. Such swelling behaviour is expected to cause internal stress development under geometrically confined conditions pertaining to geological storage of CO2, but this has not been widely investigated. Here, we report uniaxial compaction/swelling tests performed, using a 1-D compaction cell, on pre-pressed discs of Wyoming (Na-SWy-1) and Arizona (Ca-SAz-1) montmorillonite, as well as on smectite-bearing shale. We explore the axial (Terzaghi) effective stress generated in these materials upon exposure to 10 MPa CO2 pressure under conditions where total swelling (including poroelastic effects) is restricted to axial strains below 3%. The experiments were performed at 44 °C. In each experiment, the sample was first equilibrated with lab air (RH ≈ 40%–60% at T = 20–25 °C) at the experimental temperature and pre-compacted at ∼60 MPa axial stress to generate a dense reproducible microstructure. A lower axial normal stress of 25.9–40.9 MPa was then applied and the loading piston held in fixed position. This yielded an effective (Terzaghi) overburden stress of 9.6–24.7 MPa upon introduction of CO2 at 10 MPa, thus simulating burial depths of ∼0.8–2.0 km. Following CO2 introduction, axial swelling stresses developed rapidly, independently of the direct effect of increased pore pressure, attaining values of 7.1–12.4 MPa at equilibrium, compared with ∼2 MPa obtained using inert Ar. Experiments on Na-SWy-1 montmorillonite showed that the swelling stress generated upon exposure to CO2 decreases with increasing initial and final effective normal stress, suggesting that overburden stress suppresses swelling (stress) development in smectite, presumably by limiting the amount of CO2 uptake by the material investigated. The swelling stresses observed imply that CO2 penetration into caprocks and faults in geological storage systems will lead to an increase in effective normal stress components, which in turn will tend to promote closure of fractures and enhance sealing integrity. However, further work is needed to improve understanding of the processes underlying the swelling of smectite caused by CO2 and to evaluate any risks posed to caprock and fault integrity by swelling-induced shear stresses.

Carbon dioxide flow and interactions in a high rank coal: Permeability evolution and reversibility of reactive processes

Uncertainties exist on the efficiency of CO2 injection and storage in deep unminable coal seems due to potential reduction in the permeability of coal that is induced by CO2 adsorption into the coal matrix. In addition, there is a limited knowledge about the stability of CO2 stored in coal due to changes in gas partial pressure caused by potential leakage. This paper presents an experimental study on permeability evolution in a high rank coal from South Wales coalfield due to interaction with different types of gases. The reversibility of the processes and stability of the stored CO2 in coal are investigated via a series of core flooding experiments in a bespoke triaxial flooding setup. A comprehensive and new set of high-resolution data on the permeability evolution of anthracite coal is presented.The results show a considerable reduction of permeability above 1.5 MPa CO2 pressure that is correlated with the coal matrix swelling induced by CO2 adsorption. Notably studied in this work, the chemically-induced strain due to gas sorption into coal, that has been isolated and quantified from the mechanically-induced strain as a result of changes in effective stress conditions. The results of post-CO2 core flooding tests using helium (He), nitrogen (N2) and methane (CH4) demonstrated a degree of restoration of the initial permeability. The injection of N2 showed no significant changes in the coal permeability and reversibility of matrix swelling. The initial permeability of the coal sample was partially restored after replacing N2 by CH4. Observation of permeability evolution indicates that the stored CO2 has remained stable in coal under the conditions of the experiments.

Permeability and Mineral Composition Evolution of Primary Seal and Reservoir Rocks in Geologic Carbon Storage Conditions

It has been reported that deep saline aquifers represent the largest geologic CO2 storage resource. To better predict containment effectiveness and long-term reservoir behavior of these formations, it is important to understand the potential geochemically induced changes to the porosity and permeability of both the primary sealing formation and CO2 storage formation rocks. To investigate these potential changes, an experimental study to probe the geochemical interactions of CO2/brine/rock system under geologic CO2 storage conditions was conducted in a static reaction system. Marine shale (primary sealing formation) and Lower Tuscaloosa sandstone (CO2 storage formation) core samples taken from the Plant Daniel CO2 storage test site (Jackson County, Mississippi) were exposed to CO2-saturated brine in a batch reactor at relevant geologic storage conditions (85°C and 23.8 MPa CO2 pressure) for 6 months. X-ray diffraction, scanning electron microscopy, computed tomography, and brine chemistry analyses were performed before and after the exposure. Permeability measurements from the marine shale and sandstone core samples before and after CO2/brine exposure indicated a significant effective permeability change. Sealing marine shale permeability increased following exposure while the permeability of the sandstone from the storage formation was observed to decrease. Analysis results of the primary sealing formation sample (marine shale) at the Plant Daniel CO2 storage test site have not been reported before. The permeability decrease of the Lower Tuscaloosa sandstone sample reported in this study verifies the results reported in a previous study. These results have implications for the integrity of the primary seal in a CO2 storage setting.

Catalytic performance of zeolitic imidazolate framework ZIF-95 for the solventless synthesis of cyclic carbonates from CO2 and epoxides

The catalytic potential of a chloro-functionalized zeolitic imidazolate framework ZIF-95 was investigated for the solventless cycloaddition of carbon dioxide with epoxides. The reaction parameters were optimized and moderate set of reaction conditions (80°C and 1.2MPa CO2 pressure) were chosen for the detailed catalytic study. Eventhough ZIF-95 alone was catalytically active at higher temperatures, the addition of a co-catalyst was found beneficial to bring down the temperature required to achieve high conversions of the substrate. The synergistic effect of the catalyst and the co-catalyst was explored through the investigation of reaction mechanism. The scope of extending the catalysis for other epoxides was verified. The catalyst was successfully recovered and reused for cycloaddition up to 4 cycles.

Carbocation/Polyol Systems as Efficient Organic Catalysts for the Preparation of Cyclic Carbonates.

Carbocation/polyol systems are shown to be highly efficient catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide at 50 °C and 5 MPa CO2 pressure. The best activity was shown by the combination of crystal violet and 1,1'-bi-2-naphthol (BINOL), which could be recycled five times with no loss of activity. The presence of specific interactions between the amino groups of the carbocation and the hydroxyl protons was confirmed by NMR experiments. The Job plots for the crystal violet iodide/BINOL and brilliant green iodide/BINOL systems showed that the catalytic systems consist of one molecule of the carbocation and one molecule of BINOL. Mechanistic studies using a deuterated epoxide indicate that there was some loss of epoxide stereochemistry during the reaction, but predominant retention of stereochemistry is observed. On this basis, a catalytic cycle is proposed.

Hybrid Amine-Functionalized Graphene Oxide as a Robust Bifunctional Catalyst for Atmospheric Pressure Fixation of Carbon Dioxide using Cyclic Carbonates.

An environmentally-benign carbocatalyst based on amine-functionalized graphene oxide (AP-GO) was synthesized and characterized. This catalyst shows superior activity for the chemical fixation of CO2 into cyclic carbonates at the atmospheric pressure. The developed carbocatalyst exhibits superior activity owing to its large surface area with abundant hydrogen bonding donor (HBD) capability and the presence of well-defined amine functional groups. The presence of various HBD and amine functional groups on the graphene oxide (GO) surface yields a synergistic effect for the activation of starting materials. Additionally, this catalyst shows high catalytic activity to synthesize carbonates at 70 °C and at 1 MPa CO2 pressure. The developed AP-GO could be easily recovered and used repetitively in up to seven recycle runs with unchanged catalyst activity.

Polyaniline supported Salen complex as highly active and recyclable catalysts for copolymerization of CO2 and epoxides

A new heterogeneous catalyst, polyaniline (PANI) supported SalenCrⅢCl complex was investigated for the alternating copolymerization of cyclohexene oxide (CHO) with carbon dioxide (CO2) in the presence of [PPN]Cl (bis(triphenylphosphine)iminium chloride). The FT-IR, SEM/TEM, XRD, and XPS results indicated that SalenCrⅢCl was successfully supported on PANI. The resulted catalyst (SalenCrⅢCl-PANI) exhibited excellent catalytic performance for alternating copolymerization of CHO with CO2. Compared with the homogeneous SalenCrⅢCl, the heterogeneous salenCrⅢCl-PANI had obvious effect on microstructures of the copolymer, and the obtained polymer was found to be a linear alternating copolymer with narrower molecular weight distribution. The effects of various reaction parameters were also studied in detail, the reaction gives yield=12.91 gPolym./gSupp. Cat., Mn=12.21 kg/mol, Mw/Mn(PDI)=1.16 at 5.0 MPa CO2 pressure, 80 °C and 10 h. The SalenCrⅢCl-PANI maintained good catalytic activity and selectivity after reuse.

Synthesis of Polycarbonates by Copolymerization of Carbon Dioxide and Cyclohexene Oxide Using Schiff Base Complex as Catalyst

A novel Schiff base complex BCED–Zn has been found to be an effective catalyst for copolymerization of CO2 and cyclohexene oxide to afford alternating copolymer poly(cyclohexenylene carbonate) (PCHC), and the turnover number was up to 421.1 at 110°C and 4 MPa CO2 pressure for 24 h. The influence of the reaction conditions such as reaction time, reaction temperature and CO2 pressure was discussed and optimized. The thermal stability of PCHC was measured by thermogravimetric analysis, indicating that the 5 % weight loss temperature was about 232 °C and the maximum weight loss temperature was around 256 °C.

Aqueous carbonation of the potassium-depleted residue from potassium feldspar–CaCl2 calcination for CO2 fixation

Based on the academic thought of carbon capture and utilization, a novel process to integrate the potassium extraction from the insoluble potassium feldspar, industrial waste utilization, and the subsequent CO2 fixation using the resultant potassium-depleted residue was proposed in our previous studies. The potassium-depleted residue comprises several Ca-bearing phases, namely wollastonite (CaSiO3), pseudowollastonite (Ca3Si3O9), Cl-mayenite (Ca12Al14O32Cl2), and anorthite (CaAl2Si2O8), which are potential materials for fixation of CO2 via carbonation. In this study, carbonation of the residue was examined with focuses on the effects of reaction temperature, initial CO2 pressure, particle size of the residue, and reaction duration on the carbonation of these Ca-bearing phases. The results demonstrated that both the temperature and CO2 pressure significantly affect the carbonation, while the residue particle size has only minor influence. At 1 MPa CO2 pressure, the carbonation of these components was dominant at different reaction temperatures. Almost complete carbonation of the pseudowollastonite could be achieved at 75 °C, while significant carbonation of the wollastonite takes place above 100 °C. However, the Cl-mayenite and anorthite are incapable of carbonation even at 200 °C. Increasing the CO2 pressure to 4 MPa can lead to a distinct carbonation of the Cl-mayenite at 150 °C but the anorthite remains untouched. At 1.5 MPa CO2 pressure and 150 °C, with the increasing reaction time, the following Ca-bearing species were successively carbonated: first the pseudowollastonite in 5 min after the reaction started, the wollastonite in 5–15 min, and then simultaneously the wollastonite and the pseudowollastonite in 15–45 min, while the carbonation of Cl-mayenite do not begin even after 120 min. A priority sequence of carbonation of these Ca-bearing minerals was determined as follows: pseudowollastonite > wollastonite > Cl-mayenite > anorthite. The trend is in agreement with the results of thermodynamic calculation. Compared to the carbonation of natural wollastonite, the synthesized wollastonite contained in the potassium-depleted residue seems to be more active in carbonation.

Influence of temperature and pressure on quartz–water–CO2 contact angle and CO2–water interfacial tension

We measured water–CO2 contact angles on a smooth quartz surface (RMS surface roughness ∼40nm) as a function of pressure and temperature. The advancing water contact angle θ was 0° at 0.1MPa CO2 pressure and all temperatures tested (296–343K); θ increased significantly with increasing pressure and temperature (θ=35° at 296K and θ=56° at 343K at 20MPa). A larger θ implies less structural and residual trapping and thus lower CO2 storage capacities at higher pressures and temperatures. Furthermore we did not identify any significant influence of CO2–water equilibration on θ. Moreover, we measured the CO2–water interfacial tension γ and found that γ strongly decreased with increasing pressure up to ∼10MPa, and then decreased with a smaller slope with further increasing pressure. γ also increased with increasing temperature.

Supported imidazole as heterogeneous catalyst for the synthesis of cyclic carbonates from epoxides and CO2

Imidazole anchored onto a silica matrix, by means of a propyl linkage, is found to be an effective heterogeneous catalyst for the synthesis of cyclic carbonates from epoxides and CO2 in near quantitative yield. The versatility of this catalyst is demonstrated by using different substrates (epichlorohydrin, propylene oxide, butylene oxide and styrene oxide) for this cycloaddition reaction. These CO2 insertion reactions were typically carried out in the temperature range of 343 to 403K at 0.6MPa CO2 pressure under solvent-free conditions. Several spectroscopic methods were used to characterize the catalyst and study the integrity of the fresh and spent catalysts.

Quantitative analysis of accelerated carbonation products of the synthetic calcium silicate hydrate(C–S–H) by QXRD and TG/MS

In this study, calcium silicate hydrate(C–S–H) with CaO/SiO2 ratio of 1.5 target mixture is synthesized and C1.27SH0.76 with 93.4 % purity is obtained. The dried C–S–H was compacted at 8 MPa to 20 mm × 20 mm × 20 mm for accelerated carbonation. The carbonation products and carbonation degree of synthetic calcium silicate hydrate are characterized and quantitatively evaluated by QXRD (Rietveld refinement), mass gain method, and TG/MS analysis. After accelerated carbonation at 0.2 MPa CO2 pressure for 2 h, the carbonation degree from mass gain method is 71.5 %, and from TG/MS analysis is 78.0 %. Calcite, aragonite, vaterite, and amorphous phase exist simultaneously in the accelerated carbonated samples, accounting for 33.98, 17.13, 18.74, and 30.15 %, respectively. Two mass-loss stages were observed for calcium carbonate decomposition. The first mass-loss stage (300–660 °C range) was mainly caused by the decomposition of aragonite and vaterite, and calcite formed in the accelerated carbonation process has a relatively high decomposition temperature which is mainly centered in the 660–800 °C range.

Fluoro-functionalized polymeric ionic liquids: highly efficient catalysts for CO2cycloaddition to cyclic carbonates under mild conditions

Fluoro-functionalized polymeric ionic liquids (F-PILs) with imidazolium cations and bromide or chloride anions were designed for cycloaddition reactions of CO2 with epoxides. It was found that the fluorine content in F-PILs significantly influenced the catalytic activity of the catalysts, and F-PIL-Br showed three times higher activity for CO2 reacting with styrene oxide than non-fluorous PIL-Br. Moreover, F-PIL-Br could be extended to catalyse a broad range of reactants under 1 MPa CO2 pressure, producing a series of cyclic carbonates in excellent yields (93–99%). In addition, it showed high stability and easy recyclability.

Preparation of Terephthalic Acid (TPA) and Dioctyl Terephthalate (DOTP) by Anthracite's Alkali Oxygen Oxidation

TPA was synthesized by a two step reaction. Firstly, water-soluble coal acids (CA) was obtained by oxygen-oxidation at 260°C in all aqueous solution of potassium hydroxide, and then crud TPA was got by isomerization of the CA with the existence of CdCO3 catalyst and CO2 pressure. The optimum reaction conditions to get crude TPA were 4% amount of CdCO3 catalyst, and reacted at 420°C with initial 3.0MPa CO2 pressure. Pure TPA was obtained by a separation step and the yield of pure TPA is 37.16% (based on CA). Furthermore, DOTP was synthesized by the refined TPA and isooctanol. The influence of mole ratio of TPA and isooctanol, amount of catalyst and reaction time on the final yield of DOTP were discussed. The purity of TPA was detected by HPLC and DOTP was detected by FT-IR, 1H-NMR to get confirmatory results.

Direct Oxidative Carboxylation of Styrene to Styrene Carbonate over Cobalt-containing Mesoporous Molecular Sieves（Co-MCM-41） and Tetrabutylammonium Bromide Co-catalysts

Synthesis of cyclic carbonate from styrene and CO2gives a simple route that avoids the preliminary synthesis and isolation of epoxides. This direct synthesis route for cyclic carbonate from olefin is not only energy saving but also simple and economical. Herein,we synthesized various metal-dopped MCM-41 such as M-MCM-41( M = Co,Fe,Ni,Cu,Ti),and Co-MCM-41 catalyst showed the highest selectivity and yield to styrene epoxide among the various catalysts in the epoxidation of styrene. Then Co-MCM-41 was chosen to combine with tetrabutylammonium bromide( TBAB) to catalyze the direct oxidative carboxylation in one-pot. It was found that the Co-MCM-41 / TBAB catalysts efficiently catalyzed the direct oxidative carboxylation of styrene to styrene carbonate. An improved styrene carbonate yield of 46. 1% was obtained under mild reaction conditions of 80 ℃,7 h,and 4 MPa CO2pressure. It was found that Co-MCM-41 catalyzed the first epoxidation reaction and TBAB catalyzed the second cycloaddition reaction of CO2.

Fast CO2 Sequestration, Activation, and Catalytic Transformation Using N-Heterocyclic Olefins

N-Heterocyclic Olefin (NHO) with high electronegativity at the terminal carbon atom was found to show a strong tendency for CO2 sequestration, affording a CO2 adduct (NHO-CO2). X-ray single crystal analysis revealed the bent geometry of the binding CO2 in the NHO-CO2 adducts with an O-C-O angle of 127.7-129.9°, dependent on the substitute groups of N-heterocyclic ring. The length of the C(carboxylate)-C(NHO) bond is in the range of 1.55-1.57 Å, significantly longer than that of the C(carboxylate)-C(NHC) bond (1.52-1.53 Å) of the previously reported NHC-CO2 adducts. The FTIR study by monitoring the ν(CO2) region of transmittance change demonstrated that the decarboxylation of NHO-CO2 adducts is easier than that of the corresponding NHC-CO2 adducts. Notably, the NHO-CO2 adducts were found to be highly active in catalyzing the carboxylative cyclization of CO2 and propargylic alcohols at mild conditions (even at ambient temperature and 0.1 MPa CO2 pressure), selectively giving α-alkylidene cyclic carbonates in good yields. The catalytic activity is about 10-200 times that of the corresponding NHC-CO2 adducts at the same conditions. Two reaction paths regarding the hydrogen at the alkenyl position of cyclic carbonates coming from substrate (path A) or both substrate and catalyst (path B) were proposed on the basis of deuterium labeling experiments. The high activity of NHO-CO2 adduct was tentatively ascribed to its low stability for easily releasing the CO2 moiety and/or the desired product, a possible rate-limiting step in the catalytic cycle.

Cyclic carbonate synthesis from epoxides and CO2 over cyanocobalamin/n -Bu4 NI

The synthesis of cyclic carbonates from epoxides and carbon dioxide catalyzed by cyanocobalamin and n-Bu4NI system was achieved under 0.8?MPa CO2 pressure at 140 degrees C without organic solvents. Propylene carbonate was obtained in 99% yield within 6?h under the optimized reaction conditions. The cyanocobalamin catalyst could be recycled with water and retained moderate catalytic activity. Copyright (c) 2012 John Wiley & Sons, Ltd.

CO2 Copolymers from Epoxides: Catalyst Activity, Product Selectivity, and Stereochemistry Control

The use of carbon dioxide as a carbon source for the synthesis of organic chemicals can contribute to a more sustainable chemical industry. Because CO(2) is such a thermodynamically stable molecule, few effective catalysts are available to facilitate this transformation. Currently, the major industrial processes that convert CO(2) into viable products generate urea and hydroxybenzoic acid. One of the most promising new technologies for the use of this abundant, inexpensive, and nontoxic renewable resource is the alternating copolymerization of CO(2) and epoxides to provide biodegradable polycarbonates, which are highly valuable polymeric materials. Because this process often generates byproducts, such as polyether or ether linkages randomly dispersed within the polycarbonate chains and/or the more thermodynamically stable cyclic carbonates, the choice of catalyst is critical for selectively obtaining the expected product. In this Account, we outline our efforts to develop highly active Co(III)-based catalysts for the selective production of polycarbonates from the alternating copolymerization of CO(2) with epoxides. Binary systems consisting of simple (salen)Co(III)X and a nucleophilic cocatalyst exhibited high activity under mild conditions even at 0.1 MPa CO(2) pressure and afforded copolymers with >99% carbonate linkages and a high regiochemical control (∼95% head-to-tail content). Discrete, one-component (salen)Co(III)X complexes bearing an appended quaternary ammonium salt or sterically hindered Lewis base showed excellent activity in the selectively alternating copolymerization of CO(2) with both aliphatic epoxides and cyclohexene oxide at high temperatures with low catalyst loading and/or low pressures of CO(2). Binary or one-component catalysts based on unsymmetric multichiral Co(III) complexes facilitated the efficient enantioselective copolymerization of CO(2) with epoxides, providing aliphatic polycarbonates with >99% head-to-tail content. These systems were also very efficient in catalyzing the terpolymerization of cyclohexene oxide, propylene oxide and CO(2). The resulting terpolymer had a single glass-transition temperature and a single thermolysis peak. This Account also provides a thorough mechanistic understanding of the high activities, excellent selectivities, and unprecedented stereochemical control of these Co(III)-based catalysts in the production of CO(2) copolymers . The catalysis occurs through a cooperative monometallic mechanism, in which the Lewis acidic Co(III) ion serves as electrophile to activate then epoxide and the nucleophilic counterion or cocatalyst serves as a nucleophile to initiate polymer-chain growth. The high activity and excellent regioselectivity observed in the epoxide ring-opening reactions results from epoxide activation through the moderate electrophilicity of the Co(III) ion, the fast insertion of CO(2) into the Co-O bond, and the facile dissociation of the propagating carboxylate species from the central metal ion. The reversible intra- or intermolecular Co-O bond formation and dissociation helps to stabilize the active Co(III) species against reversion to the inactive Co(II) ion. We also describe our laboratory's recent preparation of the first crystalline CO(2)-based polymer via highly stereospecific copolymerization of CO(2) and meso-cyclohexene oxide and the selective synthesis of perfectly alternating polycarbonates from the coupling of CO(2) with epoxides bearing an electron-withdrawing group.

Mg‐Silicate Carbonation Based on an HCl‐ and NH3‐Recyclable Process: Effect of Carbonation Temperature

AbstractA new indirect mineral carbonation process is studied which could mitigate anthropogenic CO2 emissions. In this process, magnesium silicate is dissolved in HCl and the resulting MgCl2 solution is subsequently reacted with CO2 in NH3. HCl and NH3 are recovered from NH4Cl in a two‐step thermal decomposition. Carbonation is investigated from 30 °C to 180 °C at 4 MPa CO2 pressure and Mg‐carbonate morphology transformations with increasing temperature are identified. Nesquehonite (MgCO3 · 3H2O) is obtained below 70 °C, hydromagnesite (Mg5(CO3)4(OH)2 · 4H2O) is formed at 100 °C, and further temperature increase to 180 °C leads to magnesite (MgCO3) precipitation. Nesquehonite and magnesite can fix more CO2 per mole Mg than hydromagnesite.