共查询到20条相似文献,搜索用时 922 毫秒
1.
Summary: Extraction of residual monomer from a latex product with supercritical carbon dioxide ((sc)CO 2) in a column was studied. Operating conditions were chosen at 35 °C and 100 bar. For reducing the residual styrene level in a polystyrene latex from 10 4 ppm to 100 ppm and from 10 4 ppm to 10 ppm, a countercurrent bubble column with latex as continuous and (sc)CO 2 as dispersed phase is suggested. Monomer partitioning was demonstrated to be a key parameter in the equipment design. Monomer transport was found to be governed by the shuttle effect, caused by Brownian motion of the latex to and from the H 2O/CO 2 interface. The drift-flux approach was followed to determine the column flooding conditions. Small column volumes are obtained. (sc)CO 2 is a promising extraction medium for residual monomer reduction in latex products. Performance towards steam stripping is better as the final residual monomer level becomes lower. 相似文献
2.
Three different porous metal organic framework (MOF) materials have been prepared with and without uncoordinated amine functionalities
inside the pores. The materials have been characterized and tested as adsorbents for carbon dioxide. At 298 K the materials
adsorb significant amount of carbon dioxide, the amine functionalised adsorbents having the highest CO 2 adsorption capacities, the best adsorbing around 14 wt% CO 2 at 1.0 atm CO 2 pressure. At 25 atm CO 2 pressure, up to 60 wt% CO 2 can be adsorbed. At high pressures the CO 2 uptake is mostly dependent on the available surface area and pore volume of the material in question. For one of the iso-structural
MOF pairs the introduction of amine functionality increases the differential adsorption enthalpy (from isosteric method) from
30 to around 50 kJ/mole at low CO 2 pressures, while the adsorption enthalpies reach the same level at increase pressures. The high pressure experimental results
indicate that MOF based solid adsorbents can have a potential for use in pressure swing adsorption of carbon dioxide at elevated
pressures. 相似文献
3.
The conversion of CO 2 into more synthetically flexible CO is an effective and potential method for CO 2 remediation, utilization and carbon emission reduction. In this paper, the reaction of carbon-carbon dioxide (the Boudouard reaction) was performed in a microwave fixed bed reactor using semi-coke (SC) as both the microwave absorber and reactant and was systematically compared with that heated in a conventional thermal field. The effects of the heating source, SC particle size, CO 2 flow rate and additives on CO 2 conversion and CO output were investigated. By microwave heating (MWH), CO 2 conversion reached more than 99% while by conventional heating (CH), the maximum conversion of CO 2 was approximately 29% at 900 °C. Meanwhile, for the reaction with 5 wt% barium carbonate added as a promoter, the reaction temperature was significantly reduced to 750 °C with an almost quantitative conversion of CO 2. Further kinetic calculations showed that the apparent activation energy of the reaction under microwave heating was 46.3 kJ/mol, which was only one-third of that observed under conventional heating. The microwave-assisted Boudouard reaction with catalytic barium carbonate is a promising method for carbon dioxide utilization. 相似文献
4.
The responses of alkylamine functionalized organic bridged polysilsesquioxanes on chemicapacitive sensors to carbon dioxide
(CO 2) are described operating at temperatures ranging from 15 to 50°C. These hybrid organic–inorganic network materials were synthesized
by the sol–gel polymerization of a mixture of a matrix monomer and functional monomer at various ratios followed by aging
and ink-jet deposition of the sol on each capacitive sensor. During exposure of the sensor to known concentrations of analyte,
the material’s capacitance was measured. From these changes in capacitance, detection limits ranging from 40 to 100 ppm were
calculated. Furthermore, a correlation was observed with increasing length of the alkyl chain in the amine monomer correlating
with an increase in CO 2 sensitivity and a decrease in water sensitivity. These materials offer a new method for CO 2 detection for building control systems or other low-power applications using low operating temperatures. 相似文献
5.
Permeability data are reported for carbon dioxide in Lexan polycarbonate at 35°C. Measurements were made for both pure carbon dioxide and for a mixed feed consisting of carbon dioxide with a 117.8-torr (0.155-atm) Partial pressure of isopentane. The effects of varying upstream CO 2 driving pressure from 1 up to 20 atm were studied. The permeability to CO 2 is reduced significantly in the presence of isopentane; however, the fractional depression of the CO 2 permeability due to the isopentane at low driving pressures is much more significant than at high CO 2 driving pressures. The well-known pressure dependence of carbon dioxide permeabilities in glassy polymers, therefore, is largely diminished by introducing isopentane to the pure carbon dioxide feed. These observations are consistent with a model for transport in glassy polymers which explains the observed trends in terms of competition between the two penetrants for microvoid sorption sites existing in the non-equilibrium glassy polymer. Exclusion of carbon dioxide from microvoid sorption sites by the more condensable isopentane preempts transport through the microvoid regions, resulting in the observed depression of the CO 2 permeability. 相似文献
6.
Through our newly-developed “chemical vapor deposition integrated process (CVD-IP)” using carbon dioxide (CO 2) as the raw material and only carbon source introduced, CO 2 could be catalytically activated and converted to a new solid-form product, i.e., carbon nanotubes (CO 2-derived) at a quite high yield (the single-pass carbon yield in the solid-form carbon-product produced from CO 2 catalytic capture and conversion was more than 30% at a single-pass carbon-base). For comparison, when only pure carbon dioxide was introduced using the conventional CVD method without integrated process, no solid-form carbon-material product could be formed. In the addition of saturated steam at room temperature in the feed for CVD, there were much more end-opening carbon nano-tubes produced, at a slightly higher carbon yield. These inspiring works opened a remarkable and alternative new approach for carbon dioxide catalytic capture to solid-form product, comparing with that of CO 2 sequestration (CCS) or CO 2 mineralization (solidification), etc. As a result, there was much less body volume and almost no greenhouse effect for this solid-form carbon-material than those of primitive carbon dioxide. 相似文献
7.
Atmospheric carbon dioxide (CO 2) has increased from 278 to 408 parts per million (ppm) over the industrial period and has critically impacted climate change. In response to this crisis, carbon capture, utilization, and storage/sequestration technologies have been studied. So far, however, the economic feasibility of the existing conversion technologies is still inadequate owing to sluggish CO 2 conversion. Herein, we report an aqueous zinc– and aluminum–CO 2 system that utilizes acidity from spontaneous dissolution of CO 2 in aqueous solution to generate electrical energy and hydrogen (H 2). The system has a positively shifted onset potential of hydrogen evolution reaction (HER) by 0.4 V compared to a typical HER under alkaline conditions and facile HER kinetics with low Tafel slope of 34 mV dec ?1. The Al–CO 2 system has a maximum power density of 125 mW cm ?2 which is the highest value among CO 2 utilization electrochemical system. 相似文献
8.
A carpet-like nanostructure of polyaniline (PANI) nanothin film functionalized with poly(ethyleneimine), PEI, was used as a miniature chemiresistor sensor for detection of CO 2 at room temperature. Good sensing performance was observed upon exposing the PEI–PANI device to 50–5000 ppm CO 2 in presence of humidity with negligible interference from ammonia, carbon monoxide, methane and nitrogen dioxide. The sensing mechanism relied on acid–base reaction, CO 2 dissolution and amine-catalyzed hydration that yielded carbamates and carbonic acid for a subsequent pH detection. The sensing device showed reliable results in detecting an unknown concentration of CO 2 in air. 相似文献
9.
A chromatographic technique is introduced based on single-walled carbon nanotubes (SWCNTs) as stationary phase for separation of Ar, CO 2 and H 2 at parts per million (ppm) levels. The efficiency of SWCNTs was compared with solid materials such as molecular sieve, charcoal, multi-walled carbon nanotubes and carbon nanofibers. The morphology of SWCNTs was optimized for maximum adsorption of H 2, CO 2 and Ar and minimum adsorption of gases such as N 2, O 2, CO and H 2O vapour. To control temperature of the gas chromatography column, peltier cooler was used. Mixtures of Ar, CO 2 and H 2 were separated according to column temperature program. Relative standard deviation for nine replicate analyses of 0.2 mL H 2 containing 10 μL of each Ar or CO 2 was 2.5% for Ar, 2.8% for CO 2 and 3.6% for H 2. The interfering effects of CO, and O 2 were investigated. Working ranges were evaluated as 40-600 ppm for Ar, 30-850 ppm for CO 2 and 10-1200 ppm for H 2. Significant sensitivity, small relative standard deviation (RSD) and acceptable limit of detection (LOD) were obtained for each analyte, showing capability of SWCNTs for gas separation and determination processes. Finally, the method was used to evaluate the contents of CO 2 in air sample. 相似文献
10.
The chemoselectivity of the palladium‐catalyzed carbonylation of amines was affected by the addition of MeOH in supercritical carbon dioxide. The results show different selectivity in supercritical carbon dioxide CO 2(sc) from that in alcohol. Methyl carbamate and its derivatives were obtained in high yields in CO 2(sc). 相似文献
11.
This work investigates by means of molecular dynamics the filling of carbon nanotubes by carbon dioxide molecules. Nanotubes of various sizes are simulated and the resulting CO 2 density calculated. The effects of various CO 2 models are also investigated. The results show that the carbon dioxide molecules have a natural tendency to fill the nanotubes and the final CO 2 concentration inside the nanotube can be approximately 100 times (depending on diameter and CO 2 model) higher than that of the external atmosphere. 相似文献
12.
Surface changes created by interaction of transversely excited atmospheric carbon dioxide (TEA CO2) laser with titanium target/implant in nitrogen and carbon dioxide gas were studied. TEA CO2 laser operated at 10.6 μm, pulse length of 100 ns and fluence of ∼17 J/cm2 which was sufficient for inducing surface modifications. Induced changes depend on the gas used. In both gases the grain structure was produced (central irradiated zone) but its forms were diverse, (N2: irregular shape; CO2: hill-like forms). Hydrodynamic features at peripheral zone, like resolidified droplets, were recorded only in CO2 gas. Elemental analysis of the titanium target surface indicated that under a nitrogen atmosphere surface nitridation occurred. In addition, irradiation in both gases was followed by appearance of plasma in front of the target. The existence of plasma indicates relatively high temperatures created above the target surface offering a sterilizing effect. 相似文献
13.
CO 2 capture by aqueous alkanolamines treating is one of the prevalent methods to reduce carbon dioxide emissions and to help environmental problems. For realizing more the thermodynamics of the CO 2–MDEA–H 2O, the PC-SAFT equation of state was used to simulate the absorption of carbon dioxide by MDEA (methyldiethanolamine). A correlation for temperature-dependent binary interaction parameter were calculated by excess enthalpy data for aqueous MDEA at low temperatures (lower than 350 K), and then this binary interaction parameter used to predict phase equilibria of ternary aqueous mixtures of MDEA with carbon dioxide. Smith–Missen algorithm and PC-SAFT EOS have been used to determine concentration of species in chemical equilibrium and physical equilibrium, respectively. In addition, for determining parameter sets of MDEA, vapor pressure and saturated liquid density data were used and different and probable association schemes were considered in parameter estimations. Results show 4(2:2, 0:0) association scheme for MDEA and 4(2:2) association scheme for water have better agreement with binary and ternary VLE experimental data. 相似文献
14.
In recent years we have focused our efforts on investigating various binary mixtures containing carbon dioxide to find the best candidate for CO 2 capture and, therefore, for applications in the field of CCS and CCUS technologies. Continuing this project, the present study investigates the phase behavior of three binary systems containing carbon dioxide and different oxygenated compounds. Two thermodynamic models are examined for their ability to predict the phase behavior of these systems. The selected models are the well-known Peng–Robinson (PR) equation of state and the General Equation of State (GEOS), which is a generalization for all cubic equations of state with two, three, and four parameters, coupled with classical van der Waals mixing rules (two-parameter conventional mixing rule, 2PCMR). The carbon dioxide + ethyl acetate, carbon dioxide + 1,4-dioxane, and carbon dioxide + 1,2-dimethoxyethane binary systems were analyzed based on GEOS and PR equation of state models. The modeling approach is entirely predictive. Previously, it was proved that this approach was successful for members of the same homologous series. Unique sets of binary interaction parameters for each equation of state, determined for the carbon dioxide + 2-butanol binary model system, based on k12– l12 method, were used to examine the three systems. It was shown that the models predict that CO 2 solubility in the three substances increases globally in the order 1,4-dioxane, 1,2-dimethoxyethane, and ethyl acetate. CO 2 solubility in 1,2-dimethoxyethane, 1.4-dioxane, and ethyl acetate reduces with increasing temperature for the same pressure, and increases with lowering temperature for the same pressure, indicating a physical dissolving process of CO 2 in all three substances. However, CO 2 solubility for the carbon dioxide + ether systems (1,4-dioxane, 1,2-dimethoxyethane) is better at low temperatures and pressures, and decreases with increasing pressures, leading to higher critical points for the mixtures. By contrast, the solubility of ethyl acetate in carbon dioxide is less dependent on temperatures and pressures, and the mixture has lower pressures critical points. In other words, the ethers offer better solubilization at low pressures; however, the ester has better overall miscibility in terms of lower critical pressures. Among the binary systems investigated, the 1,2-dimethoxyethane is the best solvent for CO 2 absorption. 相似文献
15.
The slow reaction between peroxodisulfate and formate is significantly accelerated by ascorbate at room temperature. The products of this induced oxidation, CO 2 and oxalate (C 2O 2–
4), were analyzed by several methods and the kinetics of this reaction were measured. The overall mechanism involves free radical species. Ascorbate reacts with peroxodisulfate to initiate production of the sulfate radical ion (SO –
4), which reacts with formate to produce carbon dioxide radical ion (CO –
2) and sulfate. The carbon dioxide radical reacts with peroxodisulfate to form CO 2 or self-combines to form oxalate. Competition occurring between these two processes determines the overall fate of the carbon dioxide radical species. As pH decreases, protonation of the carbon dioxide radical ion tends to favor production of CO 2. 相似文献
16.
The use of supercritical carbon dioxide as a reaction medium for polyester synthesis is hindered by the low solubility of diols in CO 2. However, it has been previously demonstrated that fluorinated compounds can exhibit greater miscibility with carbon dioxide than their hydrocarbon analogs. Therefore, the phase behavior of fluorinated diols and divinyl adipate (DVA), an activated diester, in supercritical carbon dioxide has been investigated at 323 K. The phase behavior of equimolar mixtures of DVA with the most carbon dioxide-soluble diol, 3,3,4,4,5,5,6,6-octafluorooctan-1,8-diol (OFOD), was also determined. The solubility of a polyester synthesized from DVA and 2,2,3,3-tetrafluoro-1,4-butanediol (TFBD) was found to be less CO 2-soluble than its monomers. DVA was much more soluble in CO 2 than any of the fluorinated diols, therefore, no attempt was made to fluorinate the DVA structure. Because both substrates and polyester product were soluble in carbon dioxide, the enzymatic synthesis of a fluorinated polyester from DVA and octafluorooctandiol was performed in supercritical carbon dioxide, resulting in a polymer with a weight average molecular weight of 8232 Da. 相似文献
17.
The thermodynamic equilibrium for the steam-carbon dioxide conversion of methane was studied by Gibbs energy minimization.
The degree of coke formation, the content of methane and carbon dioxide in the synthesis gas, and the synthesis gas H 2/CO ratio were plotted as functions of the molar ratios of CO 2/CH 4 and H 2O/CH 4 in the initial mixture at different temperatures and pressures. The regions of the optimum CH 4/CO 2/H 2O molar ratios for steam-carbon dioxide conversion were discovered, with no coke formation taking place in these regions.
The optimized CH 4/CO 2/H 2O molar fractions characterized by the minimum content of methane and carbon dioxide in the synthesis gas were found for each
region. 相似文献
18.
Polyamines have been used as active materials to capture carbon dioxide gas based on its well-known reaction with amines to form carbamates. This work investigates the reactions between three amino-terminated poly(amidoamine) (PAMAM) dendrimers (G1, G3 and G5) and CO 2(g) in aqueous (D 2O) and methanolic (CD 3OD) solutions. The reactions were monitored using 1H NMR spectroscopy, and yielded dendrimers with a combination of terminal carbamate and terminal ammonium groups. In aqueous media the reaction was complicated by the generation of soluble carbonate and bicarbonate ions. The reaction was cleaner in CD 3OD, where the larger G5 dendrimer solution formed a gel upon exposure to CO 2(g). All reactions were reversible, and the trapped CO 2 could be released by treatment with N 2(g) and mild heating. These results highlight the importance of the polyamine dendrimer size in terms of driving changes to the solution’s physical properties (viscosity, gel formation) generated by exposure to CO 2(g). 相似文献
19.
Fabrication of nanoscale polymer‐based devices, especially in biomedical applications, is a challenging process due to requirements of precise dimensions. Methods that involve elevated temperature or chemical adhesives are not practicable due to the fragility of the device components and associated deformation. To effectively fabricate devices for lab‐on‐a‐chip or drug delivery applications, a process is required that permits bonding at low temperatures. The use of carbon dioxide (CO 2) to assist the bonding process shows promise in reaching this goal. It is now well established that CO 2 can be used to depress the glass transition temperature ( Tg) of a polymer, allowing bonding to occur at lower temperatures. Furthermore, it has been shown that CO 2 can preferentially soften a polymer surface, which should allow for effective bonding at temperatures even below the bulk Tg. However, the impact of this effect on bonding has not been quantified, and the optimal bonding temperature and CO 2 pressure conditions are unknown. In this study, a molecular dynamics model is used to examine the atomic scale behavior of polystyrene in an effort to develop understanding of the physical mechanisms of bonding and to quantify how the process is impacted by CO 2. The final result is the identification of a range of CO 2 pressure conditions which produce the strongest bonding between PS thin films at room temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 相似文献
20.
Quartz rods coated with a thin layer of chemically modified silica gel have been used for the generation of a two-component gaseous standard mixture containing carbon monoxide and carbon dioxide. A new method based on thermal decomposition of immobilized compounds chemically bonded to the surface of silica gel has been used in the generation process. The oxalic acid moiety bonded to the glycydoxypropylsilylated surface of silica gel underwent decarbonylation and decarboxylation at 300°C, yielding carbon monoxide and carbon dioxide. On-line connection of a thermal desorber with the GC/FID enabled calibration of the detector following the process of methanization of CO and CO 2. The following amounts of CO and CO 2 were generated per unit length of the rod: 15.1 × 10 −8 Mol cm −1 (RSD = 5.71%) for CO and 34.2 × 10 −8 Mol cm −1(RSD = 5.16%) for CO 2. 相似文献
|