Amine degradation in aqueous amine scrubbing systems for capturing CO₂ from coal fired power plants is a major problem. Oxygen in the flue gas is the major cause of solvent deterioration, which increases the cost of CO₂ capture due to reduced capacity, reduced rates, increased corrosion, solvent makeup, foaming, and reclaiming. Degradation also produces environmentally hazardous materials: ammonia, amides, aldehydes, nitramines, and nitrosamines. Thus it is important to understand and mitigate amine oxidation in industrial CO₂ capture systems. A series of lab-scale experiments was conducted to better understand the causes of and solutions to amine oxidation. This work included determination of rates, products, catalysts, and inhibitors for various amines at various conditions. Special attention was paid to understanding monoethanolamine (MEA) oxidation, whereas oxidation of piperazine (PZ) and other amines was less thorough. The most important scientific contribution of this work has been to show that amine oxidation in real CO₂ capture systems is much more complex than previously believed, and cannot be explained by mass transfer or reaction kinetics in the absorber by itself, or by dissolved oxygen kinetics in the cross exchanger. An accurate representation of MEA oxidation in real systems must take into account catalysts present (especially Mn and Fe), enhanced oxygen mass transfer in the absorber as a function of various process conditions, and possibly oxygen carriers other than dissolved oxygen in the cross exchanger and stripper. Strategies for mitigating oxidative degradation at low temperature, proposed in this and previous work are less effective or ineffective with high temperature cycling, which is more representative of real systems. In order of effectiveness, these strategies are: selecting an amine resistant to oxidation, reduction of dissolved metals in the system, reduction of the stripper temperature, reduction of the absorber temperature, and addition of a chemical inhibitor to the system. Intercooling in the absorber can reduce amine oxidation and improve energy efficiency, whereas amine oxidation should be considered in choosing the optimal stripper temperature. In real systems, 2-amino-2-methyl-1-propanol (AMP) is expected to be the most resistant to oxidation, followed by PZ and PZ derivatives, then methyldiethanolamine (MDEA), and then MEA. MEA oxidation with high temperature cycling is increased 70% by raising the cycling temperature from 100 to 120 °C, the proposed operational temperature range of the stripper. PZ oxidation is increased 100% by cycling to 150 °C as opposed to 120 °C. Metals are expected to increase oxidation in MEA and PZ with high temperature cycling by 40 - 80%. Inhibitor A is not expected to be effective in real systems with MEA or with PZ. MDEA is also not effective as an inhibitor in MEA, and chelating agents diethylenetriamine penta (acetic acid) (DTPA) and 2,5-dimercapto-1,3,4-thiadiazole (DMcT) are only mildly effective in MEA. Although MEA oxidation in real systems cannot be significantly reduced by any known additives, it can be accurately monitored on a continuous basis by measuring ammonia production from the absorber. Ammonia production was shown to account for two-thirds of nitrogen in degraded MEA at low temperature and with high temperature cycling, suggesting that it is a reliable indicator of MEA oxidation under a variety of process conditions. A proposed system, which minimizes amine oxidation while maintaining excellent rate and thermodynamic properties for CO₂ capture would involve use of 4 m AMP + 2 m PZ as a capture solvent with the stripper at 135 °C, intercooling in the absorber, and use of a corrosion inhibitor or continuous metals removal system. Reducing (anaerobic) conditions should be avoided to prevent excessive corrosion from occurring and minimize the amount of dissolved metals. This system is expected to reduce amine oxidation by 90-95% compared with the base case 7 m MEA with the stripper at 120 °C. / text

nÃo hà / Os altos nÃveis de emissÃo de CO2 neste Ãltimo sÃculo tÃm gerado alerta e preocupaÃÃo Ãs autoridades a nÃvel mundial. Incentivos para desenvolver tecnologias de captura e armazenamento de CO2 ganham destaque nesse cenÃrio. Dentre as alternativas viÃveis para captura do referido gÃs està o processo de adsorÃÃo. A literatura à vasta nos estudos experimentais de adsorÃÃo de CO2 em diversos materiais impregnados, entretanto poucos trabalhos se dedicam ao entendimento dos fenÃmenos em nÃvel atÃmico. O presente estudo objetiva investigar a adsorÃÃo de CO2 em faujasitas do tipo X e carbonos ativados impregnados com monoetanolamina (MEA), mediante o uso de simulaÃÃo molecular. Para isso, modelos de MEA, CO2, faujasita e carbono ativado foram elaborados. Para a faujasita, construiu-se a estrutura com base nos dados cristalogrÃficos reportados na literatura. No carbono ativado, os poros foram representados pelo modelo de placas paralelas de grafeno e realizou-se o estudo em trÃs tamanhos caracterÃsticos (8,9, 18,5, 30,9 Ã) de modo a representar distintas regiÃes de adsorÃÃo e tambÃm permitir correlacionar dados com o carvÃo comercial WV-1050. A molÃcula de CO2 foi construÃda com os modelos de 3 centros (ensaios em faujasitas) e de 1 centro (ensaios em carbonos ativados). Os adsorventes foram carregados com quantidades crescentes de MEA e o impacto desta adiÃÃo foi avaliado atravÃs do levantamento de novas isotermas de CO2 utilizando-se o mÃtodo de Monte Carlo no ensemble Grande CanÃnico (GCMC). Com o modelo proposto faujasita/MEA/CO2, foi possÃvel reproduzir a tendÃncia experimental de reduÃÃo de adsorÃÃo de CO2 com aumento da concentraÃÃo de MEA, em concordÃncia com resultados experimentais apresentados na literatura. Em carbonos ativados, observou-se que os valores de CO2 adsorvidos a alta pressÃo (acima de 4 bar) sempre decaÃam com o carregamento de MEA para ambos os poros, como foi evidenciado experimentalmente em carbonos reais. No entanto, a simulaÃÃo revelou que as quantidades adsorvidas a baixa pressÃo (abaixo de 1 bar) sÃo maiores quando se adiciona monoetanolamina ao material carbonoso. Os resultados, com base nas tÃcnicas aplicadas nesse estudo, indicam que os sistemas NaX e carbono ativado modificados com MEA sÃo pouco viÃveis para captura de CO2 no que diz respeito ao critÃrio isolado de capacidade de adsorÃÃo / The high levels of CO2 emissions over the last century have generated concern and alert worldwide. Incentives to promote technologies for CO2 capture and storage are highlighted in this situation. Among the viable alternatives to capture that gas is the adsorption process. The literature contains many experimental studies of CO2 adsorption in various impregnated materials, despite that, few papers are devoted to the understanding of such phenomena at the atomic level. This study investigates the CO2 adsorption in X-faujasites and activated carbons impregnated with monoethanolamine (MEA) using molecular simulation. Thus, models of MEA, CO2, faujasite and activated carbon were proposed. For faujasite, the structure was modeled based on the crystallographic data reported in the literature. For activated carbon, the pores were represented by the slit pores model of graphene and the study was conducted in three pore sizes (8.9, 18.5, 30.9 Ã) to represent different regions of the adsorption and also allow for data correlation with the commercial activated carbon WV-1050. The CO2 molecule was modeled in the three-centers (faujasites tests) and one-center (carbons tests) models. The adsorbents were loaded with increasing amounts of monoethanolamine and the impact of this addition was evaluated through a set of simulated CO2 isotherms using the Grand Canonical Monte Carlo (GCMC) method. With the model faujasite/MEA/CO2, it was possible to reproduce the decreasing experimental CO2 adsorption with increased MEA concentration. In carbons, it was observed that the values of adsorbed CO2 at high pressure (above 4 bar) always decrease with MEA increasing loadings for both pores, as verified experimentally in real carbons. However, the simulation has shown that the amount adsorbed at low pressures (below 1 bar) is enhanced with monoethanolamine concentration in carbonaceous material. These results, considering the techniques used in this study, indicate that the activated carbon and NaX systems modified with monoethanolamine are unfeasible for capturing CO2 if adsorption capacity is the only criterion to take into account

Yes / The increasing concentration of carbon dioxide (CO2) in the atmosphere is a primary global environmental concern due to its detrimental impacts on climate change. A significant reduction in CO2 generation together with its capture and storage is an imperative need of the time. CO2 can be captured from power plants and other industries through various methods such as absorption, adsorption, membranes, physical and biological separation techniques. The most widely used systems are solvent based CO2 absorption method. The aim of this study was to analyze the effect of various random and structured packing materials in absorption column on CO2 removing efficiency. Aspen plus was used to develop the CO2 capture model for different packing materials with Monoethanolamine (MEA) solvent in order to optimize the system. It was found that the lowest re-boiler duty of 3,444 kJ/KgCO2 yield the highest rich CO2 loading of 0.475 (mole CO2/mole MEA) by using the BX type of structured packing having the highest surface area. The surface area of the different packing materials were inversely proportional to the temperature profiles along the column. Furthermore, the packing materials with higher surface areas yielded higher CO2 loading profiles and vice versa. The findings of this study and recommendation would help further research on optimization of solvent-based CO2 capturing technologies.

A monoetanolamina (MEA) é um composto bifuncional pertencente à classe dos amino-álcoois, muito utilizado em processos industriais envolvendo a remoção de gases ácidos como SO2 , CO2 e H2S. A resina Amberlite XAD-7 é uma resina não-iônica de polaridade intermediária muito utilizada em procedimentos de pré-concentração de compostos orgânicos e íons metálicos. Neste trabalho, estudou-se a interação entre a superfície da resina XAD-7 e a MEA. Massas conhecidas da resina foram colocadas em contato com soluções de MEA em concentrações conhecidas, sob agitação durante certo intervalo de tempo. A quantidade de MEA adsorvida foi calculada considerando-se a diferença entre a concentração inicial e a concentração remanescente no sobrenadante, ambas obtidas a partir de medidas de absorbância, com utilização da reação de Berthelot modificada. Modelos cinéticos de pseudo-primeira e -segunda ordens, além do modelo de difusão intra-partícula, foram aplicados aos dados experimentais obtidos no estudo cinético. Entre estes modelos aplicados, o de pseudo-segunda ordem apresentou excelente ajuste aos dados experimentais. O estudo realizado em um determinado tempo de contato e variando-se a concentração inicial de MEA forneceu resultados experimentais que foram aplicados a três modelos de isotermas (Langmuir, Freundlich e Dubinin-Radushkevich). Destes ajustes, que mostraram excelente concordância, foram obtidos diferentes parâmetros termodinâmicos que definiram algumas características do processo de adsorção. Finalmente, estudos preliminares evidenciaram a retenção de SO32- na superfície da resina XAD-7 modificada com MEA, mostrando a possibilidade da utilização da XAD- 2 7/MEA para extração de SO32- presente em soluções ou de SO2 recolhido em solução alcalina. / Monoethanolamine (MEA) is a bifunctional compound which belongs to the amino- alcohol group, and it is widely used in industrial \"sweetening process\", which is based on the acidic gas (such as SO2 , CO2 and H2S) absorption. Amberlite XAD-7 is a non-polar resin with an intermediate polarity used to pre-concentrate organic compounds and transition metals. In this work, the interaction between the resin surface and MEA was studied. Known amounts of the resin were kept in contact with aqueous solutions of MEA and shaked under a constant rotation and during some defined intervals of time. The amount of adsorbed MEA was calculated as the difference between the initial concentration and remained concentration in the supernatant solution, which was determined applying the Berthelot´s reaction and the spectrophotometry. Kinetic models of pseudo-first and -second orders and intra-particle diffusion model were applied on experimental data collected from the kinetic study. Among these methods, the pseudo-second order model fulled fit on those experimental data. The experiments carried out under a constant time, but by changing the initial MEA concentration, led to other experimental data which were applied to three different isotherm models (Langmuir, Freundlich e Dubinin-Radushkevich). Each model showed a good fit, and for each one, different thermodynamic parameters were calculated and used to describe some adsorption characteristics. Finally, preliminary studies on the retention of SO32- onto the resin surface, previously modified with MEA, showed the possibility to extract SO32- found in aqueous solutions or SO2 recovered in alkaline media.

A monoetanolamina (MEA) é um composto bifuncional pertencente à classe dos amino-álcoois, muito utilizado em processos industriais envolvendo a remoção de gases ácidos como SO2 , CO2 e H2S. A resina Amberlite XAD-7 é uma resina não-iônica de polaridade intermediária muito utilizada em procedimentos de pré-concentração de compostos orgânicos e íons metálicos. Neste trabalho, estudou-se a interação entre a superfície da resina XAD-7 e a MEA. Massas conhecidas da resina foram colocadas em contato com soluções de MEA em concentrações conhecidas, sob agitação durante certo intervalo de tempo. A quantidade de MEA adsorvida foi calculada considerando-se a diferença entre a concentração inicial e a concentração remanescente no sobrenadante, ambas obtidas a partir de medidas de absorbância, com utilização da reação de Berthelot modificada. Modelos cinéticos de pseudo-primeira e -segunda ordens, além do modelo de difusão intra-partícula, foram aplicados aos dados experimentais obtidos no estudo cinético. Entre estes modelos aplicados, o de pseudo-segunda ordem apresentou excelente ajuste aos dados experimentais. O estudo realizado em um determinado tempo de contato e variando-se a concentração inicial de MEA forneceu resultados experimentais que foram aplicados a três modelos de isotermas (Langmuir, Freundlich e Dubinin-Radushkevich). Destes ajustes, que mostraram excelente concordância, foram obtidos diferentes parâmetros termodinâmicos que definiram algumas características do processo de adsorção. Finalmente, estudos preliminares evidenciaram a retenção de SO32- na superfície da resina XAD-7 modificada com MEA, mostrando a possibilidade da utilização da XAD- 2 7/MEA para extração de SO32- presente em soluções ou de SO2 recolhido em solução alcalina. / Monoethanolamine (MEA) is a bifunctional compound which belongs to the amino- alcohol group, and it is widely used in industrial \"sweetening process\", which is based on the acidic gas (such as SO2 , CO2 and H2S) absorption. Amberlite XAD-7 is a non-polar resin with an intermediate polarity used to pre-concentrate organic compounds and transition metals. In this work, the interaction between the resin surface and MEA was studied. Known amounts of the resin were kept in contact with aqueous solutions of MEA and shaked under a constant rotation and during some defined intervals of time. The amount of adsorbed MEA was calculated as the difference between the initial concentration and remained concentration in the supernatant solution, which was determined applying the Berthelot´s reaction and the spectrophotometry. Kinetic models of pseudo-first and -second orders and intra-particle diffusion model were applied on experimental data collected from the kinetic study. Among these methods, the pseudo-second order model fulled fit on those experimental data. The experiments carried out under a constant time, but by changing the initial MEA concentration, led to other experimental data which were applied to three different isotherm models (Langmuir, Freundlich e Dubinin-Radushkevich). Each model showed a good fit, and for each one, different thermodynamic parameters were calculated and used to describe some adsorption characteristics. Finally, preliminary studies on the retention of SO32- onto the resin surface, previously modified with MEA, showed the possibility to extract SO32- found in aqueous solutions or SO2 recovered in alkaline media.

Les recherches s’inscrivent dans une prospection qui étudie la viabilité de la valorisation du CO2 d’un incinérateur de déchets industriels. Plusieurs licences commerciales existent pour le captage du CO2 dans des gaz de combustion mais il n’existe pas de référence pour le traitement de fumées d’incinérateur de déchets. Les travaux évaluent, à l’aide d’une installation pilote, la viabilité du captage du CO2 en postcombustion par absorption/désorption avec un solvant à 30 % massique en monoéthanolamine (MEA). Tout d’abord, une synthèse bibliographique identifie les verrous technologiques. Puis, le fonctionnement de l’installation est détaillé. Ensuite, une étude paramétrique a évalué les performances de captage du CO2 et la consommation énergétique du pilote. Enfin, des expériences sur une période de 5 jours ont étudié la résistance chimique du solvant face des gaz de combustion. Les travaux de recherche ont permis une première validation du procédé pour un incinérateur de déchets. / This research is part of a survey designed to establish the viability of the CO2 recovery as a raw material from an industrial waste incinerator.. Several commercial licenses are available to capture CO2 in flue gas, but there are no references for incinerators. This work studies with a pilot the post-combustion CO2 capture from incinerator flue gas using absorption/desorption process with 30 %wt monoethanolamine (MEA). A literature review identifies the technology gaps. Then, the pilot setup was described. A parametric study has evaluated the pilot performance for CO2 capture and energy consumption. Finally, Long runs (5 days) have studied the solvent chemical stability in front of incinerator flue gas. The laboratory experiments show that CO2 capture form incinerator flue gas is possible.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The reactive absorption rate of CO2 into non-aqueous solvents containing the primary amine, mono-ethanolamine (MEA) is recognised as a suitable method for measuring the effective interfacial mass transfer area of separation column internals such as random and structured packing. Currently, this method is used under conditions where the concentration of MEA in the liquid film is unaffected by the reaction and the liquid phase reaction is, therefore, assumed to obey pseudo first order kinetics with respect to CO2. Under pseudo first order conditions, the effect of surface depletion and renewal rates are not accounted for. Previous research indicated that the effective area available for mass transfer is also dependent upon the rate of surface renewal achieved within the liquid film. In order to study the effect of surface depletion and renewal rates on the effective area, a method utilising a fast reaction with appreciable depletion of the liquid phase reagent is required. The homogeneous liquid phase reaction kinetics of CO2 with MEA n-Propanol as alcoholic solvent was investigated in this study. A novel, in-situ Fourier Transform Infra-Red (FTIR) method of analysis was developed to collect real time concentration data from reaction initiation to equilibrium. The reaction was studied in a semi-batch reactor set-up at ambient conditions (T = 25°C, 30°C and 35°C, P = 1 atm (abs)). The concentration ranges investigated were [MEA]:[CO2] = 5:1 and 10:1. The concentration range investigated represents conditions of significant MEA conversion. The reaction kinetic study confirmed the findings of previous research that the reaction of CO2 with MEA is best described by the zwitterion reactive intermediate reaction mechanism. Power rate law and pseudo steady state hypothesis kinetic models (proposed in literature) were found to be insufficient at describing the reaction kinetics accurately. Two fundamentally derived rate expressions (based on the zwitterion reaction mechanism) provided a good quality model fit of the experimental data for the conditions investigated. The rate constants of the full fundamental model were independent of concentration and showed an Arrhenius temperature dependence. The shortened fundamental model rate constants showed a possible concentration dependence, which raises doubt about its applicability. The specific absorption rates (mol/m2.s) of CO2 into solutions of MEA/n-Propanol (0.2 M and 0.08 M, T = 25°C and 30°C, P = ±103 kPa) were investigated on a wetted wall experimental setup. The experimental conditions were designed for a fast reaction in the liquid film to occur with a degree of depletion of MEA in the liquid film. Both interfacial depletion and renewal of MEA may be considered to occur. The gas phase resistance to mass transfer was determined to be negligible. An increase in liquid turbulence caused an increase in the specific absorption rate of CO2 which indicated that an increase in liquid turbulence causes an increase in effective mass transfer area. Image analysis of the wetted wall gas-liquid interface confirmed the increase in wave motion on the surface with an increase in liquid turbulence. The increase in wave motion causes an increase in both interfacial and effective area. A numerical solution strategy based on a concentration diffusion equation incorporating the fundamentally derived rate expressions of this study is proposed for calculating the effective area under conditions where surface depletion and renewal rates are significant. It is recommended that the reaction kinetics of CO2 with MEA in solvents of varying liquid properties is determined and the numerical technique proposed in this study used to calculate effective area from absorption rates into these liquids. From the absorption data an effective area correlation as a function of liquid properties may be derived in future. / AFRIKAANSE OPSOMMING: Die reaktiewe absorpsie van CO2 in nie-waterige oplossings van die primêre amien, monoetanolamien (MEA) word erken as ‘n geskikte metode om die effektiewe massaoordragsarea van gepakte skeidingskolomme te bepaal. Tans word die metode gebruik onder vinnige pseudo eerste orde reaksietoestande met betrekking tot CO2. Die pseudo eersteorde aanname beteken dat die konsentrasie van MEA in die vloeistoffilm onbeduidend beïnvloed word deur die reaksie en effektief konstant bly. Onder pseudo eerste orde toestande word oppervlakverarming- en oppervlakvernuwingseffekte nie in ag geneem nie, juis as gevolg van die konstante konsentrasie van MEA in die vloeistoffilm. Daar is voorheen bevind dat oppervlakverarming en oppervlakvernuwing ‘n beduidende invloed het op die beskikbare effektiewe massaoordragsarea. Hierdie invloed kan slegs bestudeer word met ‘n vinnige reaksie in die vloeistoffilm wat gepaard gaan met beduidende oppervlakverarming van die vloeistoffase reagens. Die homogene vloeistoffase reaksiekinetika van CO2 met MEA in die alkohol oplosmiddel, n- Propanol, is in hierdie studie ondersoek. ‘n Nuwe, in-situ Fourier Transform Infra-Rooi (FTIR) metode van analiese is ontwikkel in hierdie ondersoek. Die reaksie is ondersoek in ‘n semienkelladings reaktor met MEA wat gevoer is tot die reaktor om met die opgeloste CO2 te reageer. Die FTIR metode meet spesiekonsentrasie as ‘n funksie van tyd sodat die konsentrasieprofiele van CO2, MEA en een van die soutprodukte van die reaksie gebruik kan word om verskillende reaksiesnelheidsvergelykings te modelleer. Die reaksie is ondersoek onder matige toestande (T = 25°C, 30°C and 35°C, P = 1 atm (abs)). Die konsentrasiebereik van die ondersoek was [MEA]:[CO2] = 5:1 en 10:1. Hierdie bereik is spesifiek gebruik sodat daar beduidende omsetting van MEA kon plaasvind. Die reaksiekinetieka studie het, ter ondersteuning van bestaande teorie, bevind dat die reaksie van CO2 met MEA in nie-waterige oplosmiddels soos alkohole, beskyf word deur ‘n zwitterioon reaksiemeganisme. Die bestaande reaksiesnelheids modelle (eksponensiële wet en pseudo gestadigde toestand hipotese) kon nie die eksperimentele data met genoegsame akuraatheid beskryf nie. Twee nuwe reaksiesnelheidsvergelykings, afgelei vanaf eerste beginsels en gebaseer op die zwitterioon meganisme, word voorgestel. Hierdie volle fundamentele model het goeie passings op die eksperimentele data getoon oor die volledige temperatuur en konsentrasiebereik van hierdie studie. Die reaksiekonstantes van die fundamentele model was onafhanklik van konsentrasie en tipe oplosmiddel en het ‘n Arrhenius temperatuurafhanklikheid. Die verkorte fundamentele model se reaksiekonstantes het ‘n moontlike konsentrasieafhanlikheid gewys. Dit plaas onsekerheid op die fundamentele basis van hierdie model en kan dus slegs as ‘n eerste benadering beskou word. Die spesifieke absorpsietempos (mol/m2.s) van CO2 in MEA/n-Propanol oplossings (0.2 M en 0.08 M MEA, T = 25°C and 30°C, P = ±103 kPa) is ondersoek met ‘n benatte wand (‘wetted wall’) eksperimentele opstelling. Die eksperimentele toestande is gekies sodat daar ‘n vinnige reaksie in die vloeistoffilm plaasgevind het, met beide beduidende en nie-beduidende MEA omsetting. Die doel met hierdie eksperimentele ontwerp was om die invloed van intervlakverarming en intervlakvernuwing op die spesifieke absorpsietempo te ondersoek. Gas fase weerstand was nie-beduidend onder die eksperimentele toestande nie. Beide intervlakverarming en intervlakvernuwing gebeur gelyktydig en is waargeneem vanuit die eksperimentele data. ‘n Beeldverwerkingstudie van die gas-vloeistof intervlak van die benatte wand het bevind dat daar ‘n toename in golfaksie op die vloeistof oppervlak is vir ‘n toename in vloeistof turbulensie. Hierdie golfaksie dra by tot oppervlakvernuwing en ‘n toename in effektiewe massaoordragsarea. ‘n Numeriese metode word voorgestel om die effektiewe area van beide die benatte wand en gepakte kolomme te bepaal vanaf reaktiewe absorpsietempos. Die metode gebruik die fundamentele reaksiesnelheidsvergelykings, bepaal in hierdie studie, in a konsentrasie diffusievergelyking sodat oppervlakverarming en vernuwing in ag geneem kan word. Daar word voorgestel dat die reaksiekinetika van CO2 met MEA in oplossings met verskillende fisiese eienskappe (digtheid, oppervlakspanning en viskositeit) bepaal word sodat die numeriese metode gebruik kan word om ‘n effektiewe area korrelasie as ‘n funksie van hierdie eienskappe te bepaal.

The effects of ACQ solution parameters such as copper to quat ratio, pH and copper to ligand ratio on distribution of copper complexes in solution and insoluble precipitates, and on fixation and leaching of copper in treated wood were evaluated. The distribution of ionic complexes, predicted by equilibrium speciation model (MINTEQA2), was related to laboratory fixation and leaching results at controlled ACQ solution parameters. A decrease in the relative proportion of copper in the ACQ formulation from a copper oxide (CuO) to didecyldimethylammonium carbonate (DDACb) ratio of 2:1 to 1:1 and 1:2 resulted in lower copper retention in the treated samples and substantially decreased the amount of copper leached per unit area. For monoethanolamine (Mea) based ACQ, solution parameters which favour a higher proportion of monovalent cationic complex, which consume one reactive site in wood, and the presence of insoluble carbonate precipitate of copper in wood during preservative treatment resulted in higher leach resistance compared to the neutral copper complex present at higher pH. Ammonia (NH3) based ACQ can fix more copper at high pH as there is no chelated neutral complex as in Mea based ACQ; however divalent copper-NH3 complexes may consume two sites to fix in wood. Addition of NH3 in Mea based ACQ at Cu:Mea:NH3 ratio of 1:4:6 at pH 10.6 significantly reduced copper leaching compared to 1:4:0 (without ammonia) at pH 9 due to increased divalent copper-ammonia complexes and decreased neutral copper amine complex at elevated pH. Ammonia addition with a lower proportion of Mea (1:2.5:4 at pH 10.5-10.7), significantly reduced copper leaching compared to 1:4:0 at pH 9; no reduction was observed for ammonia addition in ACQ with a higher proportion of Mea (1:4:4 at pH 10.45). The lower copper leaching from 1:2.5:4 resulted from the higher amount of divalent copper-NH3 complexes at higher pH without compromising the amount of copper precipitated at lower pH. The higher percent copper leached from tetramethylethylenediamine (Tmed) based ACQ compared to Mea and NH3 based ACQ suggested that highly stable complexes tend to stay in solution and do not result in leach resistant copper in the wood.

A substituição da água por líquidos iônicos (LI) oferece uma alternativa promissora para o desenvolvimento de processos de separação de gases, principalmente devido à significativa demanda energética em processos convencionais que utilizam soluções aquosas de aminas. Esta proposta apresenta-se interessante por aliar as propriedades dos LI à reatividade de aminas perante o CO2. A físico-química que governa as interações entre os íons dos líquidos iônicos é bastante diversa das encontradas em solventes moleculares, sendo que ainda permanecem muitas questões fundamentais acerca destes materiais. A melhor compreensão das interações estabelecidas entre aminas e LI, e dos produtos formados após a reação com CO2, pode contribuir para o desenvolvimento de processos mais eficazes que permitam a substituição da água nos processos convencionais. O presente trabalho teve como objetivo investigar soluções das aminas primárias propilamina (PA), 2-metoxietilamina (MOEN) e monoetanolamina (MEA) em líquidos iônicos imidazólicos com diferentes ânions: 1-butil-3-metilimidazólio tetrafluoroborato (BMIBF4), hexafluorofosfato (BMIPF6), bis-(trifluorometilsulfonil)imida (BMITFSI) e dicianamida (BMIN(CN)2). Para tal, foram utilizadas as espectroscopias Raman e infravermelho (IR), cujos resultados foram suportados por cálculos baseados na teoria do funcional da densidade (DFT). Os resultados mostram que o modo de estiramento assimétrico do grupo NH2 das aminas, νas(NH2), é o mais adequado para se inferir sobre o grau de agregação das aminas em solventes orgânicos e em LI. No caso das reações das aminas com CO2 nos diferentes LI, o comportamento foi similar à reação com as aminas puras, ou seja, na PA houve cristalização, na MOEN, a formação de um líquido miscível com os LI, e na MEA, a formação de um gel com a subsequente separação de fases. Em particular, no caso da reação entre MEA e CO2 em LI, além da separação de fases, foi observada a diferente solubilidade dos produtos de reação dependendo do LI em questão. Em contraste ao processo convencional que utiliza soluções aquosas de aminas para a captura do CO2, acredita-se que a separação de fases observada em LI seja uma vantagem a ser explorada, já que permitiria um menor gasto energético na recuperação da amina absorvedora, além da recuperação do solvente não volátil / The replacement of water by ionic liquids (IL) offers a promising alternative for the development of gas separation processes, mainly due to the significant energy demand in conventional processes using aqueous solutions of amines. This proposal is exciting because it combines the properties of IL with the reactivity of amines towards CO2. The physical-chemistry that governs the interactions between the ionic liquids ions is quite different from those found in molecular solvents, and many fundamental questions still remain about these materials. A better understanding of the interactions between amines and IL, and the products formed after the reaction with CO2, may contribute to the development of more efficient processes to enable the replacement of water in conventional processes. This study aimed to investigate solutions of the primary amines propylamine (PA), 2-methoxyethylamine (MOEN) and monoethanolamine (MEA) in imidazolium ionic liquids with different anions: 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4), hexafluorophosphate (BMIPF6), bis (trifluoromethylsulfonyl)imide (BMITFSI) and dicyanamide (BMIN(CN)2). For these purposes, the Raman and infrared (IR) spectroscopies were used, whose results were supported by calculations based on density functional theory (DFT). The results show that the asymmetric stretching mode of the amines group NH2, νas(NH2), are the most suitable for inferring the degree of aggregation of amines in organic solvents and IL. In the case of reactions of amines with CO2 in different IL, the behavior was similar to the reactions with neat amines, that is, it was observed crystallization with PA, the formation of a liquid miscible with IL in MOEN, and the formation of a gel-like product with subsequent phase separation in MEA. In particular, the case of the reaction between MEA and CO2 in IL, in addition to the phase separation, it was observed the different solubility of the reaction products depending on the IL concerned. In contrast to the conventional process using aqueous solutions of amines for the capture of CO2, it is believed that the phase separation observed in IL is an advantage to be exploited, since they allow lower energy consumption in the recovery of the amine absorber, besides the recovery of the non-volatile solvent.

The effects of ACQ solution parameters such as copper to quat ratio, pH and copper to ligand ratio on distribution of copper complexes in solution and insoluble precipitates, and on fixation and leaching of copper in treated wood were evaluated. The distribution of ionic complexes, predicted by equilibrium speciation model (MINTEQA2), was related to laboratory fixation and leaching results at controlled ACQ solution parameters. A decrease in the relative proportion of copper in the ACQ formulation from a copper oxide (CuO) to didecyldimethylammonium carbonate (DDACb) ratio of 2:1 to 1:1 and 1:2 resulted in lower copper retention in the treated samples and substantially decreased the amount of copper leached per unit area. For monoethanolamine (Mea) based ACQ, solution parameters which favour a higher proportion of monovalent cationic complex, which consume one reactive site in wood, and the presence of insoluble carbonate precipitate of copper in wood during preservative treatment resulted in higher leach resistance compared to the neutral copper complex present at higher pH. Ammonia (NH3) based ACQ can fix more copper at high pH as there is no chelated neutral complex as in Mea based ACQ; however divalent copper-NH3 complexes may consume two sites to fix in wood. Addition of NH3 in Mea based ACQ at Cu:Mea:NH3 ratio of 1:4:6 at pH 10.6 significantly reduced copper leaching compared to 1:4:0 (without ammonia) at pH 9 due to increased divalent copper-ammonia complexes and decreased neutral copper amine complex at elevated pH. Ammonia addition with a lower proportion of Mea (1:2.5:4 at pH 10.5-10.7), significantly reduced copper leaching compared to 1:4:0 at pH 9; no reduction was observed for ammonia addition in ACQ with a higher proportion of Mea (1:4:4 at pH 10.45). The lower copper leaching from 1:2.5:4 resulted from the higher amount of divalent copper-NH3 complexes at higher pH without compromising the amount of copper precipitated at lower pH. The higher percent copper leached from tetramethylethylenediamine (Tmed) based ACQ compared to Mea and NH3 based ACQ suggested that highly stable complexes tend to stay in solution and do not result in leach resistant copper in the wood.