SOLUBILITY OF CO2AND H2S IN A MIXED SOLVENT

Mixed solvents are a combination of chemical and physical solvents and have some advantages over traditional treating solvents for the removal of acid gases from gas streams. The solubility of H₂S and CO₂in a mixed solvent consisting of AMP (2-amino-2-methyl-l-propanol), sulfolane, and water has been measured at 40 and 100°C at partial pressures of the acid gas to 6000 kPa. The solubility in the mixed solvent was compared with the solubility in an aqueous solution of equivalent amine concentration. At solution loadings less than 1 mol acid gas/mol amine, the solubility of the acid gas is lower in the mixed solvent than in the corresponding amine solvent. At higher loadings, the trend is reversed and the solubility is greater in the mixed solvent. The results are rationalized in terms of the effect of the physical solvent component on the chemical reaction and physical vapor-liquid equilibria. The solubility model of Deshmukh and Mather was used to correlate the data.     

SOLUBILITY OF CO2 AND H2S IN A HINDERED AMINE SOLUTION

The solubility of H₂S and CO₂ in aqueous solutions of the sterically hindered amine, 2-amino-2-methyl-1-propanol (AMP), was determined at 40 and 100°C. Partial pressures of C)₂ ranged from approximately 2 to 6000 kPa and of H₂S from 2 to 2200 kPa. The solubility results were compared with previously reported acid gas solubilities in aqueous monoethanolamine (MEA) solutions.     

SOLUBILITY OF NITROUS OXIDE IN AQUEOUS SOLUTIONS OF METHYLDIETHANOLAMINE, DIETHANOLAMINE AND MIXTURES OF METHYLDIETHANOLAMINE AND DIETHANOLAMINE

The solubility of nitrous oxide (N₂O) in aqueous solutions of 0-50 mass % methyldiethanolamine (MDEA), 0-30 mass % diethanolamine (DEA), and 50 mass % total amine with DEA/MDEA weight ratios of 0.04413-0.5883 was measured over the temperature range 293-353 K and at N₂O partial pressures near atmospheric. The solubility data from this work were found to be in fair agreement with the literature where data were available. The N₂O solubility data for the aqueous MDEA and aqueous DEA solutions were fitted using the extended scaled-particle model proposed by Li and Mather (1994) (which was based on the work of Hu et al. (1985)). The parameter estimates obtained from these fits were then used to predict the N₂O solubility in the aqueous DEA + MDEA solutions. The model predictions were found to agree with the experimental data with an average deviation of 3.4%     

KINETIC AND STRUCTURAL STUDIES OF REGENERATION OF SULFIDED DOLOMITE IN CARBON DIOXIDE I THE FIRST CYCLE REGENERATION

(Communicated by H. L. Toor)

Half-calcined dolomite (CaCO₃ · MgO) is one of the most promising sorbents for desulfurizing fuel gas at high temperatures. For environmental reasons, the spent dolomite must be capable of regeneration for cyclic use. Regeneration by a mixed gas of H₂O/CO₂ has not met with success due mainly to the deterioration of sorbent reactivity with cycling. This research investigates an alternative method of regeneration using CO₂ alone and its application to cyclic use.

Kinetic data for first cycle regeneration are collected in a TGA system at 500 to 950°C and 1 to 21.4 atm. The effects of gas-composition, preconditioning and solid structure are also studied. The results show that regeneration by CO, is equally effective as by H₂O/CO₂ in terms of sorbenl reactivity. More significantly, the sorbent has shown a much slower deterioration upon cycling. Examination of solid structure by SEM and compositional profile of sulfur by XES reveals that the reaction proceeds topochemically above 700°C and homogeneously below 650°C. A transport-reaction model is developed and shown to agree closely with experimental results.     

MODELLING OF EQUILIBRIUM SOLUBILITY OF CO2 AND H2S IN AQUEOUS AMINO METHYL PROPANOL (AMP) SOLUTIONS

Information on acid gas solubility in solvents utilized is needed for the design of gas plants. A mathematical model for the prediction of equilibrium solubility of CO₂ and H₂S in aqueous 2-amino-2-methyl-l-propanol (AMP) solutions is presented. The equilibrium constant, K₁ governing the main amine reaction is expressed as a function of not only temperature but also acid gas partial pressure and AMP concentration. Model predictions agree favourably with experimental data.     

Impact of support oxide and Ba loading on the NOx storage properties of Pt/Ba/support catalysts: CO2 and H2O effects

A series of 1 wt.%Pt/_xBa/Support (Support = Al₂O₃, SiO₂, Al₂O₃-5.5 wt.%SiO₂ and Ce_0.7Zr_0.3O₂, x = 5–30 wt.% BaO) catalysts was investigated regarding the influence of the support oxide on Ba properties for the rapid NO_x trapping (100 s). Catalysts were treated at 700 °C under wet oxidizing atmosphere. The nature of the support oxide and the Ba loading influenced the Pt–Ba proximity, the Ba dispersion and then the surface basicity of the catalysts estimated by CO₂-TPD. At high temperature (400 °C) in the absence of CO₂ and H₂O, the NO_x storage capacity increased with the catalyst basicity: Pt/20Ba/Si < Pt/20Ba/Al5.5Si < Pt/10Ba/Al < Pt/5Ba/CeZr < Pt/30Ba/Al5.5Si < Pt/20Ba/Al < Pt/10BaCeZr. Addition of CO₂ decreased catalyst performances. The inhibiting effect of CO₂ on the NO_x uptake increased generally with both the catalyst basicity and the storage temperature. Water negatively affected the NO_x storage capacity, this effect being higher on alumina containing catalysts than on ceria–zirconia samples. When both CO₂ and H₂O were present in the inlet gas, a cumulative effect was observed at low temperatures (200 °C and 300 °C) whereas mainly CO₂ was responsible for the loss of NO_x storage capacity at 400 °C. Finally, under realistic conditions (H₂O and CO₂) the Pt/20Ba/Al5.5Si catalyst showed the best performances for the rapid NO_x uptake in the 200–400 °C temperature range. It resulted mainly from: (i) enhanced dispersions of platinum and barium on the alumina–silica support, (ii) a high Pt–Ba proximity and (iii) a low basicity of the catalyst which limits the CO₂ competition for the storage sites.     

Primary nucleation of citric acid monohydrate: influence of selected impurities

An experimental study is presented concerning solubility and primary nucleation kinetics of monohydrate citric acid from pure and selectively impure (KH₂PO₄, MgSO₄ · 7H₂O and FeSO₄ · 7H₂O) aqueous solutions. The metastable range of pure solutions is wide, ranging from 6 to 14°C, and the order of primary nucleation, equal to 2.51, is quite low. The addition of the tested impurities, which are usual fermentation aids, at concentrations lower than wt. 1%, produces negligible effects on the solubility and slightly enhances the primary nucleation rate. However, the presence of these compounds modifies the crystal habit at birth: in particular, the addition of MgSO₄ · 7H₂O and FeSO₄ · 7H₂O makes these crystals more elongated, but this effect diminishes as the crystals grow.     

Origin of transient species present on the surface of a PdO/γ-Al2O3 catalyst during the methane combustion reaction

Operando DRIFTS was applied to the study of the evolution of surface species formed on a Pd (2 wt.%)/γ-Al₂O₃ catalyst in various conditions. No differences were observed as a function of the initial oxidation state of palladium. Formates/carbonates species were identified at low temperature (<400 °C) and disappeared when CO₂ production started. These species come from the Pd-catalyzed interaction of CO with the alumina support, while CO₂ induces hydrogenocarbonates formation at low temperature (<300 °C). Their presence does not explain the inhibiting effect of CO₂ observed in CCM on Pd/γ-Al₂O₃ catalysts.     

SOLUBILITY OF CO2AND H2S IN A MIXED SOLVENT

Mixed solvents are a combination of chemical and physical solvents and have some advantages over traditional treating solvents for the removal of acid gases from gas streams. The solubility of H₂S and CO₂in a mixed solvent consisting of AMP (2-amino-2-methyl-l-propanol), sulfolane, and water has been measured at 40 and 100°C at partial pressures of the acid gas to 6000 kPa. The solubility in the mixed solvent was compared with the solubility in an aqueous solution of equivalent amine concentration. At solution loadings less than 1 mol acid gas/mol amine, the solubility of the acid gas is lower in the mixed solvent than in the corresponding amine solvent. At higher loadings, the trend is reversed and the solubility is greater in the mixed solvent. The results are rationalized in terms of the effect of the physical solvent component on the chemical reaction and physical vapor-liquid equilibria. The solubility model of Deshmukh and Mather was used to correlate the data.     

PACl: A simulation of the change in Al concentration and Al solubility in RO

Polyaluminium chloride (coagulant) is a very complex compound. The change in the ratio HCO₃/CO₂ during coagulation cause a change in pH in the subsequent RO unit (because CO₂ is not rejected by the RO membrane), and it was found that this change is constant for any given recovery, e.g. at 75% recovery, the pH change between the RO feed water and concentrate water is 0.6. The simulation of aluminium solubility and concentration along RO systems were performed assuming the presence of three aluminium species, Al₁₃⁷⁺, Al(OH)₄⁻, Al(OH)²⁺. The simulation of aluminium solubility was performed at two temperatures, 20°C to represent the summer period and 5°C to represent the winter period. Results showed that for winter (5°C) an RO feed water pH of at least 7.2 and for warm weather (20°C), a feed water pH of at least 6.7 are required respectively, to avoid scaling of aluminium on the RO membranes.

In conclusion, theoretical simulation of aluminium solubility and results of deposition factor showed that aluminium more than likely plays a role in fouling of the RO membranes and could be a reason for the frequent cleaning.     

ABSORPTION OF CO2 INTO AQUEOUS SOLUTIONS OF STERICALLY HINDERED METHYL AMINOETHANOL USING A HYDROPHOBIC MICROPOROUS HOLLOW FIBER CONTAINED CONTACTOR

The absorption of dilute CO₂ into aqueous solutions of sterically hindered 2-methyl aminoethanol (MAE) and the desorption of CO₂ from CO₂-loaded MAE solutions into N₂ stream were investigated separately for the various combinations of operational variables, using a hydrophobic microporous hollow fiber (polytetrafluoroethylene, PTFE) contained gas-liquid contactor with aqueous solutions of MAE as liquid media in the shell side at 30°C. The absorption of CO₂ in this contactor is governed by resistance in the liquid and hollow fiber phases. The resistance to diffusion in the hollow fiber phase amounts to 76-80% of the total resistance. Nevertheless, the absorption rates of CO₂ into aqueous MAE solutions in this contactor are higher than those into aqueous solutions of sterically hindered 2-amino-2-methyl-1-propanol (AMP) in the stirred tank with a plane unbroken gas-liquid interface. The process of desorption of CO₂ from CO₂-loaded MAE solutions can be regarded as being controlled by diffusion and chemical reaction in both the stagnant film of the liquid phase and the liquid-filled pore of the hollow fiber phase under the slow or intermediate reaction regime. Both absorption and desorption rates under the simultaneous absorption-desorption operation in a single unit tend to approach the respective constant values as process time elapses. The total absorption rate here seems to be almost balanced with the total desorpion rate at the constant mass transfer rate periods.     

膜吸收CO2工艺中不同吸收液对膜润湿的影响

以单乙醇胺（MEA）、二乙醇胺（DEA）和N-甲基二乙醇胺（MDEA）作为吸收液,利用聚丙烯（PP）中空纤维膜组件进行分离模拟烟气中CO₂的实验研究,考察不同吸收液的脱除效率以及长时间连续运行下的膜润湿现象。建立膜相传质阻力随时间变化模型,与实验数据拟合较好。同时将膜丝在不同吸收剂中浸泡,结合接触角、场发射扫描电镜（FE-SEM）、衰减全反射红外光谱（ATR-IR）以及热重（TG）表征分析膜性能的改变。结果表明,相同浓度下,单一吸收剂的CO₂脱除效率大小为MEA > DEA > MDEA;当吸收液为1mol/L MEA时,16天后CO₂脱除效率从93.3%下降到72.1%;而吸收液为1mol/L DEA时,脱除效率从88.3%到第16天的78%,下降约12%;理论计算得吸收液为1mol/L MEA和1mol/L DEA时,膜相传质阻力分别为10564.06s/m和4881.08s/m;浸渍时间增加,膜接触角减小,疏水性减弱,同时膜孔径变大,出现润湿现象;红外光谱和热重分析表明在MEA溶液作用下膜丝出现溶胀。     

ALKYD PAINT WASTE CHARACTERIZATION AND DISTILLATION

In the present study the characterization and distillation of alkyd paint waste have been carried out in order to establish the technical viability of organic solvents recovery and to decide upon the best environmental management for the waste stream from a paint spray-booth application in an automotive component factory. The paint is a black primer based on an alkyd resin with toluene and xylene as solvents, black carbon as pigment, fillers, and other minor components.

The paint, paint wastes, and distillation wastes have been characterized by determination of the physicochemical properties of the solid (solvents content and flash point) and determination of ecotoxicity (EC₅₀), total organic carbon (TOC), and metals concentration of the leachates. The highly volatile matter (HVM) content, determined by the weight loss at 200°C, has been used as a parameter to relate with the hazardous wastes regulations based on the characterization parameters EC₅₀, TOC, and flash point.

Distillation experiments have been performed in a simple batch mode with mixtures of paint waste, water, and additives in order to obtain high efficiencies in the recovery of volatile organic compounds and to obtain a final solid with nonhazardous behavior and good manageability qualities. A fractional factorial design (2^3-1) of experiments was carried out in order to study the influence of the distillation variables: water/paint waste ratio (2/1-3/1 (g/g)), temperature (110°-145°C), alkaline additives (Na(OH),CaO, Ca(OH)₂), and amount of other additives (wt.% of bentonite, cement, and Ca(OH)₂) on the solvent recovery, [% VOCs]_Recovery, on the residual volatile organic compounds, [% VOCs]_{Distillation Waste}, and on the total organic content (TOC) of the waste leachates. The present work shows the quantitative results of the alkyd paint waste distillation process under optimum conditions.     

CO_2在碳酸丙烯酯和胺、水混合溶剂中的溶解度

近年来,为解决碳酸丙烯酯（Propylene Carbonate简称丙碳）脱除 C风工艺中出现 的脱碳净化度低、溶剂循环量大、设备腐蚀严重等问题而相继开发了多种改型丙碳复合溶 剂,其中作者等人研制的由丙碳和适量的叔胺（MDEA）、水构成的混合溶剂,不仅脱碳 性能明显优于丙碳,而且有效地解决了设备腐蚀问题。本文研究了CO。在此混合溶剂中 的溶解度与温度和压力的关系。     

Formation of active state in vanadium–titanium oxide system regarding to reaction of oxidation of β-picoline to nicotinic acid

Binary vanadia–titania catalysts comprising 5–75 wt.% of V₂O₅ and 95–25 wt.% of TiO₂, pretreated at the temperature ranging between 300 and 700°C, were studied as heterogeneous catalysts for oxidation of β-picoline at 250°C, and inlet concentrations of the following components (vol.%): 1% of 3-picoline, 20% of oxygen, 30% of steam. Nicotinic acid, 3-pyridinecarbaldehyde and CO₂ were the reaction products. The most active state for oxidation of 3-picoline into nicotinic acid was shown to result from formation of coherent interface between V₂O₅ and TiO₂ (anatase) crystallites. This state was generated at the temperature particular for each composition and persists below the temperature of the anatase to rutile transition.     

ABSORPTION OF H2S INTO AQUEOUS METHYLDIETHANOLAMINE

The absorption of H₂S into aqueous methyldiethanolamine (MDEA) was studied experimentally over the temperature range 15 to 35°C and for MDEA concentrations from 10 to 25 wt% using a laminar liquid jet device and a stirred-cell absorber. The contact times ranged from 2 × 10^-3 to 1 × 10^-2 seconds for the jet absorber and from 6 to 38 seconds for the stirred-cell absorber. It was found that the absorption rate data for both devices could be modelled assuming an instantaneous reaction regime for the reaction between H₂S and MDEA. The experimental results were interpreted to give an estimate for the diffusion coefficient of MDEA in water. Diffusion coefficient results are consistent for the two apparatuses. A lower bound for the second-order rate constant for the reaction between H₂S and MDEA is estimated from the experimental data to be 1.4 × 10¹⁰cm³/g mole s at 25°C     

ULTRASONICATION-ASSISTED SYNTHESIS OF CALCIUM CARBONATE NANOPARTICLES

This article presents a batch carbonation method with ultrasonication to synthesize monodispersed nanoparticles of calcium carbonate (CaCO₃). The synthesis processes with and without ultrasonication were compared. The results showed that the application of ultrasonication into the synthesis caused a supersaturation of Ca²⁺ ions in the synthesis, leading to a rapid nucleation of calcium carbonate and improved the solute transfer as well as. It was also found that the effect of ultrasonication on the grain size of the nanoparticles synthesized was related to other synthesis conditions, such as initial temperature for carbonation, mass fraction of Ca(OH)₂ suspension, and CO₂ flow rate. The initial temperature applied for the carbonation was increased by at least 5°C when ultrasonication was applied. The nanoparticles formed in the presence of ultrasonication became smaller with a narrower particle size distribution at 6-12 wt.% of Ca(OH)₂ suspension or at 1.28 l/h of CO₂ consumed by per gram of Ca(OH)₂ or more.     

Enthalpy recovery of gases issued from H2 production processes: Activity and stability of oxide and noble metal catalysts in oxidation reaction under highly severe conditions

Oxidation activity and stability under reaction was investigated for a series of mixed oxide catalysts, doped or not by a precious metal (Pd, Pt). The reaction feedstock, containing CO, H₂, CH₄, CO₂ and H₂O, simulated gases issued from H₂ production processes for fuel cells. Contrarily to conventional noble metal catalysts, mixed oxide samples present generally good stability under reaction at high temperature. The activities measured for the perovskite and hexaaluminate catalysts, are however largely lower than that of the reference Pd/Al₂O₃ catalyst. High activities were obtained after impregnation of 1.1 wt.% Pd or 0.8 wt.% Pt on the hexaaluminates samples. Even if Pd/Al₂O₃ was found to present a high activity, this sample suffered from drastic deactivation at 700 °C. Better stability were obtained on perovskite. Furthermore, doping hexaaluminate by Pt led to samples with good activities and high stability. Even if better activities were obtained by doping the hexaaluminate samples by Pd, the Pd/BaAl₁₂O₁₉ strongly deactivated, as it was previously observed for the reference catalyst. Interestingly, this Pd deactivation was not observed when Pd was impregnated on the Mn substituted hexaaluminate, leading to a stable and active catalyst. This suggests that it is possible to stabilize the palladium in its oxidized form at high temperature (700 °C) on the surface of some supports.     

Review of solvent based carbon-dioxide capture technologies

Currently, a large proportion of global fossil fuel emissions originate from large point sources such as power generation or industrial processes. This trend is expected to continue until the year 2030 and beyond. Carbon capture and storage (CCS), a straightforward and effective carbon reduction approach, will play a significant role in reducing emissions from these sources into the future if atmospheric carbon dioxide (CO₂) emissions are to be stabilized and global warming limited below a threshold of 2 °C. This review provides an update on the status of large scale integrated CCS technologies using solvent absorption for CO₂ capture and provides an insight into the development of new solvents, including advanced amine solvents, amino acid salts, carbonate systems, aqueous ammonia, immiscible liquids and ionic liquids. These proposed new solvents aim to reduce the overall cost CO₂ capture by improving the CO₂ absorption rate, CO₂ capture capacity, thereby reducing equipment size and decreasing the energy required for solvent regeneration.     

Equilibrium solubility of H2S and CO2 and their mixtures in a mixed solvent

The solubility of hydrogen sulphide, carbon dioxide, and their mixtures has been measured at 40° and 100°C in a mixed solvent consisting of 20.9 wt% MDEA (methyldiethanolamine), 30.5 wt% sulfolane (tetrahydrothiophene-1, 1-dioxide), and 48.6 wt% water. The results have been compared with those for aqueous 2.0 mol/dm³ MDEA and an analogous mixed solvent, containing AMP (2-amino-2-methyl-1-propanol), which are available in the literature. These data were used to modify the solubility model of Deshmukh and Mather (1981) to account for the mixed solvent effects on the system thermodynamics. Results show that the model is useful as a first approximation in predicting acid gas solubilities; agreement with experiment was generally found to be within £15%.