CO2 capture and electrochemical conversion using superbasic [P66614][124Triz]

The ionic liquid trihexyltetradecylphosphonium 1,2,4-triazolide, [P66614][124Triz], has been shown to chemisorb CO2 through equimolar binding of the carbon dioxide with the 1,2,4-triazolide anion. This leads to a possible new, low energy pathway for the electrochemical reduction of carbon dioxide to formate and syngas at low overpotentials, utilizing this reactive ionic liquid media. Herein, an electrochemical investigation of water and carbon dioxide addition to the [P66614][124Triz] on gold and platinum working electrodes is reported. Electrolysis measurements have been performed using CO2 saturated [P66614][124Triz] based solutions at −0.9 V and −1.9 V on gold and platinum electrodes. The effects of the electrode material on the formation of formate and syngas using these solutions are presented and discussed.

Application of a cw quantum cascade laser CO2 analyser to catalytic oxidation reaction monitoring

Catalytic oxidation reaction monitoring has been performed for the first time with a trace gas carbon dioxide analyser based on a continuous wave (cw), thermoelectrically cooled (TEC), distributed feedback (DFB) quantum cascade laser (QCL) operating at around 2307 cm^-1. The reaction kinetics for carbon monoxide oxidation over a platinum catalyst supported on yttria-stabilised zirconia were followed by the QCL CO₂ analyser and showed that it is a powerful new tool for measuring low reaction rates associated with low surface area model catalysts operating at atmospheric pressures. A detection limit was determined of 40 ppb (1 standard deviation) for a 0.1 s average and a residual absorption standard deviation of 1.9×10^-4. © 2012 Springer-Verlag.

The addition of CO2 to four superbase ionic liquids: a DFT study

The addition of carbon dioxide to four superbase ionic liquids, [P3333][Benzim], [P3333][124Triz], [P3333][123Triz] and [P3333][Bentriz] was studied using a molecular DFT approach involving anions alone and individual ion pairs. Intermolecular bonding within the individual ion pairs is characterised by a number of weak hydrogen bonds, with the superbase anion geometrically arranged so as to maximize interactions between the heterocyclic N atoms and the cation. The pairing energies show no correlation to the observed CO2 adsorption capacity. Addition of CO2 to the anion alone clearly resulted in the formation of a covalently-bound carbamate function with the strength of binding correlated to experimental capacity. In the ion pair however the cation significantly alters the nature of the bonding such that the overall cohesive energy is reduced. Formation of a strong carbamate function occurs at the expense of weakening the interaction between anion and cation. In the more weakly absorbing ion pairs which contain [123Triz]- and [Bentriz]-, the carbamate-functionalised systems are very close in energy to adducts in which CO2 is more weakly bound, suggesting an equilibrium between the chemi- and physisorbed CO2.

Efficacy of Wind Power in Mitigation of CO2 Emission from the Irish Electrical Grid

The results in this paper are based on a data set containing system demand, wind generation and CO2 emission between Jan 2010 and Sep 2013. The data was recorded at 15 minute intervals and reflects the macroscopic operation of the Republic of Ireland's electrical grid. The data was analyzed by investigating how daily wind generation effected daily CO2 emission across multiple days with equivalent daily demand. A figure for wind turbine efficiency was determined by dividing the CO2 mitigation potential of wind power by the CO2 intensity of the grid; both in units of Tonnes of CO2 per MWh. The yearly wind power efficiency appears to have increased by 5.6% per year, now standing around 90%. Over the four years significant regularity was observed in the profiles of wind turbine efficiency against daily demand. It appears that the efficiency profile has moved in recent years so that maximum efficiency coincides with most frequent demand.

Highly CO2 sensitive extruded fluorescent plastic indicator film based on HPTS

Highly-sensitive optical fluorescent extruded plastic films are reported for the detection of gaseous and dissolved CO2. The pH-sensitive fluorescent dye used is 8-Hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS, PTS-) coated on the surface of hydrophilic fumed silica and the base is tetrabutylammonium hydroxide (TBAH). The above components are used to create an HPTS pigment (i.e. HPTS/SiO2/TBAH) with a high CO2 sensitivity (%CO2(S=1/2) = 0.16%) and fast 50% response (t50↓) = 2 s and recovery (t50↑) = 5 s times. Highly CO2-sensitive plastic films are then fabricated, via the extrusion of the HPTS pigment powder in low-density polyethylene (LDPE). As with the HPTS-pigment, the luminescence intensity (at 515 nm) and absorbance (at 475 nm) of the HPTS plastic film decreases as the %CO2 in the ambient gas phase increases. The HPTS plastic film exhibits a high CO2 sensitivity, %CO2(S=1/2), of 0.29%, but a response time ˂2 min and recovery time ˂40 min, which is slower than that of the HPTS pigment. The HPTS plastic film is very stable under ambient conditions, (with a shelf life ˃ six month when stored in the dark but under otherwise ambient conditions). Moreover, the HPTS-film is stable in water, salt solution and even in acid (pH=2), and in each of these media it can be used to detect dissolved CO2.

Effect of the Presence of MEA on the CO2 Capture Ability of Superbase Ionic Liquids

The miscibility of monoethanolamine (MEA) in five superbase ionic liquids (ILs), namely the trihexyl-tetradecylphosphonium benzotriazolide ([P66614][Bentriz]), trihexyl-tetradecylphosphonium benzimidazolide ([P66614][Benzim]), trihexyl-tetradecylphosphonium 1,2,3-triazolide ([P66614][123Triz]), trihexyl-tetradecylphosphonium 1,2,4-triazolide ([P66614][124Triz]), and trihexyl-tetradecylphosphonium imidazolide ([P66614][Im]) was determined at 295.15 K using 1H NMR spectroscopy. The solubility of carbon dioxide (CO2) in equimolar (IL + MEA) mixtures was then studied experimentally using a gravimetric technique at 295.15 K and 0.1 MPa. The effect of MEA on the CO2 capture ability of these ILs was investigated together with the viscosity of these systems in the presence or absence of CO2 to evaluate their practical application in CO2 capture processes. The effect of the presence of MEA on the rate of CO2 uptake was also studied. The study showed that the MEA can enhance CO2 absorption over the ideal values in the case of [P66614][123Triz] and [P66614][Bentriz] while in the other systems the mixtures behave ideally. A comparison of the effect of MEA addition with the addition of water to these superbase ILs showed that similar trends were observed in each case for the individual ILs studied.

Techno-Economic Feasibility of Selective CO2 Capture Processes from Biogas Streams using Ionic Liquids as Physical Absorbents

Biogas from anaerobic digestion of sewage sludge is a renewable resource with high energy content, which is formed mainly of CH4 (40-75 vol.%) and CO2 (15-60 vol.%) Other components such as water (H2O, 5-10 vol.%) and trace amounts of hydrogen sulfide and siloxanes can also be present. A CH4-rich stream can be produced by removing the CO2 and other impurities so that the upgraded bio-methane can be injected into the natural gas grid or used as a vehicle fuel. The main objective of this paper is to develop a new modeling methodology to assess the technical and economic performance of biogas upgrading processes using ionic liquids which physically absorb CO2. Three different ionic liquids, namely the 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, 1-hexyl-3-methylimidazoliumbis[(trifluoromethyl)sulfonyl]imide and trihexyl(tetradecyl)phosphonium bis[(trifluoromethyl)sulfonyl]imide, are considered for CO2 capture in a pressure-swing regenerative absorption process. The simulation software Aspen Plus and Aspen Process Economic Analyzer is used to account for mass and energy balances as well as equipment cost. In all cases, the biogas upgrading plant consists of a multistage compressor for biogas compression, a packed absorption column for CO2 absorption, a flash evaporator for solvent regeneration, a centrifugal pump for solvent recirculation, a pre-absorber solvent cooler and a gas turbine for electricity recovery. The evaluated processes are compared in terms of energy efficiency, capital investment and bio-methane production costs. The overall plant efficiency ranges from 71-86 % whereas the bio-methane production cost ranges from £6.26-7.76 per GJ (LHV). A sensitivity analysis is also performed to determine how several technical and economic parameters affect the bio-methane production costs. The results of this study show that the simulation methodology developed can predict plant efficiencies and production costs of large scale CO2 capture processes using ionic liquids without having to rely on gas solubility experimental data.

Extraction and purification of triterpenic acids from eucalypt bark

A indústria da pasta e do papel é um sector importante da economia mundial, particularmente a que assenta em espécies de Eucalyptus. No entanto, essas indústrias geram quantidades significativas de correntes secundárias de subprodutos e resíduos de biomassa que podem ser exploradas em aplicações de valor acrescentado em vez de serem queimadas para produção de energia. Um exemplo nobre pode ser a produção de ácidos triterpénicos com estruturas dos tipos lupano, oleanano e ursano, dada a sua abundância em alguns destes resíduos, em particular na casca, adotando o conceito de biorrefinaria integrada numa fábrica de pasta. Estes compostos são conhecidos pelas suas inúmeras actividades biológicas, por exemplo, antioxidante, anti-inflamatória e antitumoral, e podem encontrar aplicações em produtos de elevado valor, tais como cosméticos, nutracêuticos ou farmacêuticos. Neste sentido, o estudo das potencialidades das cascas das espécies de eucalipto mais exploradas enquanto fontes de compostos triterpénicos é um tópico relevante. Por conseguinte, foram analisados e comparados em pormenor os teores e composições em ácidos triterpénicos (TTAs) das cascas externas de várias espécies de eucalipto (E. globulus, E. grandis, E. urograndis, E. maidenii e E. nitens). Os teores dos principais TTAs identificados nestas espécies variaram entre 4.5 g/kg no E. urograndis e 21.6 g/kg no E. nitens. Observou-se que as cascas externas de Eucalyptus de zonas temperadas e Mediterrânicas, nomeadamente E. nitens e E. globulus, são mais ricas em TTAs que as espécies de regiões tropicais e subtropicais. Além disso, a casca externa do E. globulus é claramente a mais rica em ácidos com estruturas do tipo ursano enquanto a do E. nitens é a mais rica em ácidos do tipo oleanano e lupano. Estes resultados levaram-nos a estudar a extração dos TTAs da casca de Eucalyptus, bem como a sua posterior concentração e purificação, a qual foi efetuada por extração sólido-líquido convencional combinada com a precipitação de solutos, e por extração com fluidos supercríticos (SFE). No que diz respeito à primeira abordagem referida, foi desenvolvido neste trabalho um método patenteado que permite obter extratos enriquecidos em TTAs das cascas de eucalipto baseado em tecnologias disponíveis no imediato. Em relação à segunda abordagem, e de forma a apostar em processos de baixo impacto ambiental exigidos pelas biorrefinarias do futuro, a SFE surge como uma opção natural. Assim, foi efetuada a SFE da casca caduca do E. globulus com dióxido de carbono puro e modificado para recuperar a fração de TTAs, e os resultados foram comparados com os obtidos por extração em Soxhlet com diclorometano. Foram realizados estudos preliminares sobre a influência da pressão (100-200 bar), a adição de co-solvente (0, 5 e 8% m/m de etanol), e operação em múltiplos passos a fim de avaliar a aplicabilidade da alternativa supercrítica para a sua produção eficiente e selectiva. Os resultados destacaram a influência da pressão e o importante papel resumo (cont.) desempenhado pelo co-solvente neste processo, cujo efeito foi mais relevante do que o aumento da pressão em várias dezenas de bar. Este trabalho foi depois otimizado, usando o planeamento factorial de experiências e a metodologia de superfícies de resposta, para analisar a influência da temperatura (40-60 ºC), pressão (100-200 bar), e teor de etanol (0.0-5.0% m/m) na recuperação dos TTAs e respectiva concentração nos extractos. Nestes intervalos, as melhores condições de operação encontradas foram 200 bar, 40 °C e 5% de etanol, para as quais os modelos de regressão estatisticamente validados previram um rendimento de extração de 1.2% com 50% de concentração em TTAs, correspondendo ao rendimento em TTAs de 5.1 g/kg de casca e uma recuperação de 79.2% comparativamente ao valor do Soxhlet. Os TTAs livres e acetilados apresentaram tendências de extracção bastante distintas devido às suas diferentes afinidades para o CO2 causadas pelas diferentes polaridades: os derivados acetilados aproximam-se de um patamar máximo a cerca de 200 bar e 5% de etanol, enquanto a extração dos TTAs livres apresenta uma tendência sempre crescente no intervalo de condições estudado. Foram também medidas curvas cumulativas de SFE da casca do E. globulus de forma a analisar o comportamento cinético do processo em termos de rendimento total, rendimento em TTAs, rendimento em TTAs livres, rendimento em TTAs acetilados, e concentração dos TTAs nos extractos. Foi analisada a influência da pressão, temperatura, teor de co-solvente e caudal do dióxido de carbono sobre as respostas anteriores. Os dados experimentais foram modelados com os modelos Logístico, de Dessorção, de Placa Plana Simples, e de Difusão. Na globalidade, os resultados confirmaram que a pressão e o teor de etanol têm um efeito significativo sobre as curvas de extração, os rendimentos finais e as concentrações dos extratos, e mostraram a presença de limitações externas à transferência de massa em alguns ensaios. Mais uma vez, as famílias individuais de TTAs livres e acetilados apresentaram diferentes tendências de extracção. A modelação permitiu-nos confirmar não só o importante papel desempenhado pela difusão intraparticular na SFE, mas também a contribuição da resistência no filme em alguns ensaios. Após a análise de todos os resultados, foi efetuado um ensaio em duas etapas em série, possibilitando o enriquecimento do teor em TTAs no extracto devido às diferentes condições adotadas em cada etapa. Por último, um éster metílico de um ácido triterpénico do tipo oleanano - morolato de metilo - foi identificado pela primeira vez enquanto componente da casca de Eucalyptus na casca externa do Eucalyptus grandis x globulus, onde ocorre em teores elevados. A sua extração com CO2 supercrítico foi também realizada, visando a conceção de uma alternativa de extração ambientalmente benigna para este composto. A 200 bar e 60 ºC, a remoção do morolato de metilo atingiu um patamar às 6 h para 5.1 kg h-1 de CO2 / kg de casca. Em geral, e de forma semelhante à SFE da casca do E. globulus, os TTAs acetilados foram mais significativamente extraídos quando comparados com os seus ácidos livres, o que está diretamente relacionado com a natureza menos polar destas moléculas. O trabalho apresentado nesta tese é uma contribuição para a valorização de uma corrente de biomassa com baixo valor na indústria de pasta em duas vertentes complementares. Por um lado, aumentou o conhecimento da composição lipofílica das cascas de Eucalyptus spp. com interesse comercial para a produção de pasta, destacando o seu potencial enquanto fontes de ácidos triterpénicos. Por outro lado, foram desenvolvidos dois processos alternativos e facilmente integráveis numa fábrica de pasta para a sua exploração a partir da casca: um baseado em tecnologias convencionais bem estabelecidas a nível industrial, prevendo a sua aplicação a curto prazo, e um outro baseado na SFE, seguindo as tendências das futuras biorrefinarias.

Materials and concepts for CO2 lean ironmaking by pyroelectrolysis

The main purpose of this PhD thesis was to provide convincing demonstration for a breakthrough concept of pyroelectrolysis at laboratory scale. One attempted to identify fundamental objections and/or the most critical constraints, to propose workable concepts for the overall process and for feasible electrodes, and to establish the main requirements on a clearer basis. The main effort was dedicated to studying suitable anode materials to be developed for large scale industrial units with molten silicate electrolyte. This concept relies on consumable anodes based on iron oxides, and a liquid Fe cathode, separated from the refractory materials by a freeze lining (solid) layer. In addition, one assessed an alternative concept of pyroelectrolysis with electron blocking membranes, and developed a prototype at small laboratory scale. The main composition of the molten electrolyte was based on a magnesium aluminosilicate composition, with minimum liquidus temperature, and with different additions of iron oxide. One studied the dynamics of devitrification of these melts, crystallization of iron oxides or other phases, and Fe2+/Fe3+ redox changes under laser zone melting, at different pulling rates. These studies were intended to provide guidelines for dissolution of raw materials (iron oxides) in the molten electrolyte, to assess compatibility with magnetite based consumable anodes, and to account for thermal gradients or insufficient thermal management in large scale cells. Several laboratory scale prototype cells were used to demonstrate the concept of pyroelectrolysis with electron blocking, and to identify the most critical issues and challenges. Operation with and without electron blocking provided useful information on transport properties of the molten electrolyte (i.e., ionic and electronic conductivities), their expected dependence on anodic and cathodic overpotentials, limitations in faradaic efficiency, and onset of side electrochemical reactions. The concept of consumable anodes was based on magnetite and derived spinel compositions, for their expected redox stability at high temperatures, even under oxidising conditions. Spinel compositions were designed for prospective gains in refractoriness and redox stability in wider ranges of conditions (T, pO2 and anodic overpotentials), without excessive penalty for electrical conductivity, thermomechanical stability or other requirements. Composition changes were also mainly based on components of the molten aluminosilicate melt, to avoid undue contamination and to minimize the dissolution rate of consumable anodes. Additional changes in composition were intended for prospective pyroelectrolysis of Fe alloys, with additions of different elements (Cr, Mn, Ni, Ti).

Seawater acidification by CO2 in a coastal lagoon environment: Effects on life history traits of juvenile mussels Mytilus galloprovincialis

The carbonate chemistry of seawater fromthe Ria Formosa lagoon was experimentallymanipulated, by diffusing pure CO2, to attain two reduced pH levels, by−0.3 and−0.6 pH units, relative to unmanipulated seawater. After 84 days of exposure, no differences were detected in terms of growth (somatic or shell) or mortality of juvenile mussels Mytilus galloprovincialis. The naturally elevated total alkalinity of the seawater (≈3550 μmol kg−1) prevented under-saturation of CaCO3, evenunder pCO2 values exceeding 4000 μatm, attenuating the detrimental effects on the carbonate supply-side. Even so, variations in shell weight showed that net calcification was reduced under elevated CO2 and reduced pH, although the magnitude and significance of this effect varied among size-classes. Most of the loss of shell material probably occurred as post-deposition dissolution in the internal aragonitic nacre layer. Our results show that, even when reared under extreme levels of CO2- induced acidification, juvenileM. galloprovincialis can continue to calcify and grow in this coastal lagoon environment. The complex responses of bivalves to ocean acidification suggest a large degree of interspecific and intraspecific variability in their sensitivity to this type of perturbation. Further research is needed to assess the generality of these patterns and to disentangle the relative contributions of acclimation to local variations in seawater chemistry and genetic adaptation.

Effect of high CO2 and ocean acidification on photosynthesis and response to oxidative stress in seagrasses

Climate change scenarios comprise significant modifications of the marine realm, notably ocean acidification and temperature increase, both direct consequences of the rising atmospheric CO2 concentration. These changes are likely to impact marine organisms and ecosystems, namely the valuable seagrass-dominated coastal habitats. The main objective of this thesis was to evaluate the photosynthetic and antioxidant responses of seagrasses to climate change, considering CO2, temperature and light as key drivers of these processes. The methodologies used to determine global antioxidant capacity and antioxidant enzymatic activity in seagrasses were optimized for the species Cymodocea nodosa and Posidonia oceanica, revealing identical defence mechanisms to those found in terrestrial plants. The detailed analysis and identification of photosynthetic pigments in Halophila ovalis, H.stipulacea, Zostera noltii, Z marina, Z. capricorni, Cymodocea nodosa and Posidonia oceanica, sampled across different climatic zones and depths, also revealed a similarity with terrestrial plants, both in carotenoid composition and in the pigment-based photoprotection mechanisms. Cymodocea nodosa plants from Ria Formosa were submitted to the combined effect of potentially stressful light and temperature ranges and showed considerable physiological tolerance, due to the combination of changes in the antioxidant system, activation of the VAZ cycle and accumulation of leaf soluble sugars, thus preventing the onset of oxidative stress. Cymodocea nodosa plants living in a naturally acidified environment near submarine volcanic vents in Vulcano Island (Italy) showed to be under oxidative stress despite the enhancement of the antioxidant capacity, phenolics concentration and carotenoids. Posidonia oceanica leaves loaded with epiphytes showed a significant increase in oxidative stress, despite the increase of antioxidant responses and the allocation of energetic resources to these protection mechanisms. Globally, the results show that seagrasses are physiologically able to deal with potentially stressful conditions from different origins, being plastic enough to avoid stress in many situations and to actively promote ulterior defence and repair mechanisms when under effective oxidative stress.

Assemblage structure and secondary production of mesozooplankton in shallow water volcanic CO2 vents of the Azores

Dissertação de mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

Effect of elevated CO2 concentrations and irradiance on the photosynthetic performance of the seagrass Cymodocea nodosa

Dissertação de Mestrado, Biologia Marinha, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2015

Air-sea CO2 exchange in the Kuroshio and its importance to the global CO2 uptake

Senior thesis written for Oceanography 444

CO2 reduction and efficiency in road freight traffic: measures, baseline and potential

The objective of our research was to analyse the relevant logistic factors influencing energy efficiency in road freight transport, while quantifying the potential for CO2 reduction. We carried out a survey and linked fuel consumption to transport performance parameters in 50 German haulage companies during 2003. Efficiency ranges from 0.8 tkm to 26 tkm for 1 kg CO2 emissions. The results show a high potential for improvements, given a low level of efficiency in vehicle usage and load factor, scarce use of lightweight vehicle design, incorrectly selected vehicle class and a high proportion of empty runs. Efficiency measures are poorly applied.