Abstract: In this work, carbon molecular sieve (CMS) membranes were prepared based on a polymer of intrinsic microporosity, named PIM-6FDA-OH. The goal of this work was to examine the effect of the fabrication parameters of the CMS membranes on the gas separation performance of the final CMS membranes produced. Furthermore, the performance changes are reported for membranes physically aged over 7, 30, 60, and 90 days. The membranes prepared consisted of thin-film (about 3 !m thick) CMS selective layers supported by a stainless-steel tube. The experiments were split into four projects. The first project aimed to determine the effect the layer thickness had on the final performance of the produced CMS membranes. Five pairs of membranes were prepared using different coating solution concentrations, and different number of layers. The concentrations used were 5 (1 layer), 7.5 (1 layer), and 9 wt% (1, 2, and 3 layers) polymer in THF. The membranes had the same soak time of 15 minutes and pyrolysis temperature of 650 °C. The results showed that the increase in number of layers did not provide any benefits and was unnecessary. Moreover, the decrease in concentration produced membranes with higher permeances but with a greater loss in selectivity. Therefore, the 9 wt% concentration solution with one layer was chosen for the remaining experiments. The second project examined the effect of the pyrolysis temperature on the performance of the final membranes produced. All membranes were made with the 9 wt% solution and the soak time was held constant at 15 minutes. The soak temperatures tested were: 700, 750, 850, and 950. °C. The membranes pyrolyzed at temperatures above 650 °C were severely defective. This suggests that either the precursor polymer could not form defect-free thin membranes using high soak temperatures, or another potential reason is related to interfacial defect formation between the CMS layer and the porous stainless-steel support. Further experiments are required to fully understand the soak temperature effect on the formation of thin CMS films on porous supports. The third project examined the effect of the soak time (i.e. time the membranes are held isothermally at the pyrolysis temperature) on the final performance of the membranes. The same 9 wt% solution was used, and the pyrolysis temperature was 650 °C. The pyrolysis soak times were 15 minutes, 1 hour, 3 hours, and 10 hours, respectively. The results showed that as the soak time increased the membranes became denser and provided higher selectivities and lower permeances. Furthermore, the membranes with longer soak times became more size-sieving earlier during physical aging than the membranes made with shorter soak times. Physical aging was accelerated with an increase in soak time, i.e., membranes made by soaking over 10 hours reached stable permeance over time starting at day 7. The fourth project aimed to investigate the preparation process, as well as to test the performance of the membranes under different environments. Two types of polyimide precursor membranes were made, one set with the pristine polyimide and the other one with a PDMS top coating. The results showed that the membranes with PDMS had similar selectivities but far slower permeances than the CMS membranes, the membranes made without PDMS coating had much lower selectivities and permeances. CMS membranes soaked for 15 minutes and 3 hours, respectively, were tested to check the permeances of all the five gases (H2, O2, N2, CH4, and CO2) under pressure cycles from 2 to 8 bar. The membranes passed the tests and their permeances were not affected by exposing them to high pressures and back, except for the membranes soaked for 3 hours when tested with CO2.

Orientador: Carlos Alberto Luengo / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-05T03:13:34Z (GMT). No. of bitstreams: 1 Capobianco_Gino_D.pdf: 12351248 bytes, checksum: f4842f51b128dadf5f45b6fa8ce145c4 (MD5) Previous issue date: 2005 / Resumo: Este trabalho consiste no estudo de um processo híbrido para obtenção de peneiras moleculares de carbono (PMC) a partir de madeiras e ou resíduos agrícolas tais como: casca de macadâmia e mesocarpo do coco verde que são insumos de origem renovável. A seguir descrevem-se as seguintes etapas do processo: seleção e conformação da matéria-prima; carbonização e pré-ativação (envolvendo tecnologias convencionais de ativação física ou química) e finalmente a obtenção de PMC em um reator de plasma com catodo oco para ativação. O estudo incluiu o projeto e construção de equipamentos para sua implementação em uma unidade piloto, a realização dos testes operacionais, a apreciação da influência dos parâmetros de processo (monitorados com caracterizações dos precursores em cada etapa) até a obtenção das PMC. Também a avaliação de possíveis aplicações em indústrias energo intensivas (eletro-metal e químicas), realizou-se através de estudo de caso (a remoção de metais pesados nos efluentes industriais), comparando o desempenho das PMC com os de amostras comerciais disponíveis no mercado. Finalmente, para análise da viabilidade técnico-econômico-financeira, foram realizados um levantamento da evolução da exportação e importação de carvão ativado (CA) no Brasil, sua demanda e oferta, assim como aquelas dos principais consumidores (setor industrial e setores ligados ao saneamento básico e saúde). Observa-se a que o país é auto-suficiente na produção do CA convencional, entretanto a produção de CAs com características e propriedades especificas, tipo PMC, ainda é incipiente, sendo necessário à importação de 3.000 toneladas/ano. Então, para a realização dos cálculos considera-se a capacidade de atender inicialmente, até 10 % da demanda nacional, correspondente a uma planta industrial de 300 toneladas/ano. As PMC produzidas podem ser utilizadas nas mais diversas aplicações, tais como: tratamento de efluentes líquidos e gasosos, tanques de sorção para remoção e recuperação de solventes orgânicos, entre outras. Por isso este projeto insere-se, no desenvolvimento de novas tecnologias para o país / Abstract: This work is presented an study of a hybrid process to obtain carbon molecular sieves (CMS) from pine wood or agricultural residues such as macadamia shell or green coconut mesocarp, alI of them are renewable precursors. This process embraces the following stages: selection and conformation of the raw material, carbonization and pré-activation, involving conventional physical or chemical activation technologies, finally activation using the hollow cathode plasma technology to obtain the CMS. The experimental part included design and equipment construction for implementation in a pilot unit, including operational tests, studies of the influence of process parameters, monitored with characterizations of the precursors in each stage, until obtaining CMS. To evaluate possible applications in intensive energy industries such as metal-electric industries or chemistries it was developed a case study in which the CMS efficiency for the removal of heavy metaIs in the industrial effluents was compared with that obtained using samples commercially available. For analyzing the techno economic feasibility, it was obtained the historical evolution of export and import quantities of activated carbon (AC) in Brazil, the evolution of demand and offer, as well as those of main consumer sections, industrial section and those related to basic sanitation and health.Through this analysis, it was observed that the country is self-sufficient in the production of the conventional AC, however the production of AC with special characteristic and properties, like CMS, is still incipient, being needed to import around 3.000 ton/year. Thus, the calculations are for a manufacturing capacity capable to attend up to 10% of the demand, corresponding to an industrial plant with a capacity for CMS production of 300 ton/year. The produced CMS has several applications, such as: treatment of liquid and gas effluents, sorption tanks for removal and recovery of wasted organic solvents, among others. So, this whole work, may be thought as the development of a new technology for the country / Doutorado / Doutor em Planejamento de Sistemas Energéticos

It is very important today to address the impacts of climate change as its effects can be observed every day. Nowadays many scientists believe that earth's climate is changing as a result of human-caused greenhouse gas emissions such as carbon dioxide and methane. Global energy demand is also rapidly evolving. A sustainable approach that balances economic growth with social and environmental responsibility should be considered as an effective and long-term strategy. Carbon dioxide is the foremost greenhouse gas of anthropogenic origin, responsible for the majority of the earth's warming effects. It is estimated that around 60% of the global warming impact can be traced back to the release of carbon dioxide into the atmosphere. Lowering methane emissions offers a range of notable advantages in terms of energy, safety, economy, and the environment. Firstly, since methane is a potent greenhouse gas (25 times more powerful than CO2 over a 100-year period), reducing methane emissions will contribute significantly to mitigating climate change in the short term. Additionally, methane is the primary component of natural gas and biogas, which means collecting and utilizing methane can be a valuable source of clean energy that fosters local economic growth and minimizes local environmental pollution. Generating energy through methane recovery eliminates the need for traditional energy resources, thus lessening end-user and power plant CO2 and air pollutant emissions. Physical adsorption separation processes have proven to be an effective technique for simultaneous carbon dioxide capture and methane enrichment applications. The objective of this study is to conduct a thorough assessment of the adsorption separation of methane and carbon dioxide gases employing a commercially available carbon molecular sieve, CMS(C), and an activated carbon, AC(B). The accomplishment of the objective involved conducting an in-depth characterization of the adsorbents. Part of the characterization included measurements of the internal surface area and pore size distributions, as well as the measurements of the equilibrium adsorption isotherms using gravimetric techniques. These isotherms enabled detailed kinetic analyses, such as evaluating diffusivity and mass transfer coefficients at various temperatures and pressure steps. The prediction of binary isotherms were based on theoretical models, which can describe the gas mixture adsorption equilibria using pure component equilibrium data. Breakthrough curves were generated to describe the dynamic response of an adsorption column under different pressures, temperatures, and flow rates. A mechanistic model was developed utilizing gPROMS simulation software for adsorption breakthrough process and it was validated by comparing its results to the experimental breakthrough curves. Parametric studies were conducted to determine the optimal operating conditions for gas adsorption separation of CO2 and CH4 gases. By examining the data obtained from breakthrough curves, pure and predicted binary adsorption equilibria, we calculated adsorption capacities, selectivity, sorbent selection parameter (S parameter), and the adsorbent performance indicator (API). These calculations were carried out to evaluate the initial potential for gas adsorption separation of the carbon molecular sieve (CMS(C)) and the activated carbon (AC(B)) under a range of operating conditions. Increasing pressure, decreasing temperature, and reduced feed flow improved breakthrough time and adsorption capacity for both gases on these adsorbents. CMS(C) showed superior selectivity, while AC(B) had a higher API value at specific conditions. The API was considered a more practical parameter for evaluating the initial gas separation potential. CMS(C) proved to be the better choice for methane purification, achieving the longest purification time under optimal conditions. Additionally, the study explored the kinetic behavior of methane and carbon dioxide with these adsorbent materials, revealing faster carbon dioxide uptake rates and the potential advantages of activated carbon in reducing adsorption/desorption cycle times in separation processes. At a pressure of 1 atm, a temperature of 294 K, and a flow rate of 400 ml min-1, CMS(C) had the highest values of selectivity and the S parameter, while AC(B) had the highest API value at 9 atm of pressure, a temperature of 294 K, and a flow rate of 400 ml min-1. The API was considered a more practical parameter for evaluating the initial gas separation potential. CMS(C) proved to be the better choice for methane purification, achieving the longest purification time of 420 seconds at a pressure of 9 atm, a temperature of 294 K, and a flow rate of 400 ml min-1. Additionally, the study explored the kinetic behavior of methane and carbon dioxide with these adsorbent materials, revealing faster carbon dioxide uptake rates and the potential advantages of activated carbon in reducing adsorption/desorption cycle times in separation processes. The analysis of the study, when compared to existing literature, reveals a coherent and logical progression. Our results align with similar studies, validating key points such as the improvement of methane purification through reduced feed flow rates and increased pressures, enhanced adsorption separation performance at lower temperatures and pressures, the superior adsorption capacity of activated carbon over carbon molecular sieves, and the greater selectivity of carbon molecular sieves over activated carbon and faster diffusion of carbon dioxide compared to methane within the carbon porous materials.

The objective of this research was to determine an appropriate adsorbent for the separation of CH₄ from CO₂, N₂, and O₂. To screen different adsorbents for this purpose, pure component adsorption isotherms and gas mixture isotherms were measured. Adsorption isotherms are critical data for modeling adsorption processes. Thus, determining an accurate and reliable method of measuring gas adsorption isotherms is crucial. Concentration pulse chromatography can be used to measure the slope of the isotherm. In the case of pure component adsorption, the slope at different partial pressures of adsorbate can be integrated to determine the adsorption isotherm. The accuracy of the concentration pulse chromatography method was compared to that of gravimetric analysis to find an appropriate technique to obtain pure component gas adsorption isotherms by measuring CH₄ isotherms on activated carbon at 25°C and up to 6.3 atm. Isotherm results from concentration pulse chromatography were identical to gravimetric results, but the use of a sufficiently long column for concentration pulse chromatography was crucial. Afterwards, gravimetric analysis was used to determine the performance of activated carbon (AC A-C) and carbon molecular sieve (CMS A-D) adsorbents for adsorbing CO₂ and N₂. Additionally, O₂ adsorption isotherms were measured for CMS's. At 25°C and above atmospheric pressure, AC-B showed the highest CO₂ capacity and CO₂/N₂ selectivity. The isosteric heat of adsorption values of CO₂, N₂, and O₂ for the CMS's were calculated; CMS-A and CMS-C had high isosteric heat of adsorption values for CO₂, above 40 kJ mol⁻¹. Finally, the performance of activated carbon in separating a binary mixture of CO₂ and N₂ was experimentally measured by obtaining binary gas mixture adsorption isotherms using concentration pulse chromatography technique between 30-70°C and 1-5 atm total pressure. The OLC activated carbon showed selectivity for CO₂ over N₂, with the experimental results showing a slight deviation from theoretical predictions of the binary adsorption isotherms. Compared to other adsorbents in the literature, OLC had similar CO₂ and N₂ adsorption capacities but higher CO₂/N₂ selectivity.

Orientador: Antonio Carlos Luz Lisboa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-06T17:26:02Z (GMT). No. of bitstreams: 1 Mendez_ManoelOrlandoAlvarez_M.pdf: 2603376 bytes, checksum: 0c8ee135799f28f8bda8e30c0023f76d (MD5) Previous issue date: 2005 / Resumo: Materiais Carbonosos Ativados (MCA), tais como Carvões Ativados (CA) e Peneiras Moleculares de Carbono (PMC), são caracterizados por apresentar elevada área superficial específica e um grande volume de poros em sua matriz carbonosa, sendo sua principal propriedade a de adsorver moléculas tanto na fase líquida quanto na gasosa. O Brasil importa em sua totalidade peneiras moleculares produzidas a partir de precursores carbonosos, empregando-os nas mais diversas áreas de ciência e tecnologia e em vários segmentos industriais. O coque de petróleo é um resíduo com alto teor de carbono fixo e baixo teor de cinzas, e em decorrência de sua estrutura praticamente amorfa, é um material de pouco valor comercial, sendo considerado um resíduo problemático, tanto em termos ambientais quanto comerciais. Desta forma, a utilização de coque de petróleo para a produção de CAs e de PMCs torna-se atrativa para a utilização deste resíduo. O presente trabalho teve como objetivo estudar a síntese de carvões ativados através das ativações física e química de coque de petróleo proveniente da unidade de coqueamento retardado da REPLAN - PETROBRÁS, buscando avaliar as influências dos parâmetros de processo na qualidade dos CAs, tais como: concentração de agente ativante, tempo de ativação, temperatura de ativação e granulometria do coque de petróleo. A ativação física apresentou resultados insatisfatórios devido a baixa reatividade do coque de petróleo com o dióxido de carbono. Contudo, o coque de petróleo apresentou uma maior reatividade com hidróxido de potássio, permitindo desenvolver uma metodologia adequada para a ativação química do coque de petróleo com KOH, de modo a obter carvões ativados de elevada área superficial. Os resultados obtidos indicam a possibilidade de produção de carvões ativados de elevada área superficial, superiores a 2000 m2.g-1 a partir do coque de petróleo / Abstract: Activated Carbon MateriaIs (ACM), such as Activated Carbons (AC) and Carbon Molecular Sieves (CMS), are characterized by a high specific surface area em high pore volume in their carbon matrix, being their principal property to adsorb molecules in liquid and gas phase. Brazil imports all its molecular sieves, using them in several areas of science and technology and industrial segments. Petroleum coke is a high carbon content residue with low ash content, and due to its amorphous structure have low comercial value, being considered an environmental and comercial problem. In this sense, the utilization of petroleum coke to produce AC and CMS becomes an atractive utilization of this residue. The objective of the present work was to study the synthesis of activated carbon by physical and chemical processes using as raw material the petroleum coke originated from the delayed coking unit from REPLAN PETROBRAS, evaluating the infiuence of process parameters, such as activating agent concentration, activation time, activation temperature and average particle size on the AC quality. The results of physical activation of petroleum coke was not satisfactory due to the low reactivity of the petroleum coke with the carbon dioxide. However, the petroleum coke presented higher reactivity with potassium hidroxide, given the possibility to develop an adequate methodology to chemically activate petroleum coke with KOH, in order to obtain activated carbon with high specific surface area. The results indicated the possibility to produce activated carbon materiaIs from petroleum coke with surface area higher than 2000 m2 .g-l / Mestrado / Engenharia de Processos / Mestre em Engenharia Química

Orientador: Heloise de Oliveira Pastore / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T23:57:15Z (GMT). No. of bitstreams: 1 Pires_CleoThomasGabrielVilelaMenegazTeixeira_M.pdf: 3580386 bytes, checksum: d250877101383c3bfd681800ef951608 (MD5) Previous issue date: 2006 / Resumo: Desde meados do século passado as peneiras moleculares compõem uma importante classe de materiais, que revolucionou o processo de craqueamento do petróleo. Propriedades como seletividade geométrica, alta área superficial e capacidade de troca iônica dentre outras, possibilitaram a otimização de vários processos de interesse. No final da década de 80 surgiu uma nova família de peneiras moleculares, formadas a partir da polimerização de fontes de carbono no interior dos canais e cavidades dos zeólitos e subsequente remoção do molde inorgânico por extração ácida ou básica. Esses carbonos porosos bem ordenados foram testados em diversas aplicações e apresentaram resultados promissores como suportes para catalisadores em células a combustível, materiais para a produção de supercapacitores e adsorventes de vitaminas e outras moléculas de importância biológica. O presente trabalho consistiu na preparação e caracterização de peneiras moleculares de carbono a partir da polimerização de acrilonitrila, álcool furfurílico e fenol/formaldeído no interior dos canais dos zeólitos com estrutura FAU e MWW. O conjunto de resultados obtidos indica que nos processos otimizados a polimerização ocorreu apenas no interior da estrutura cristalina dos zeólitos. Os carbonos sintetizados de modo geral apresentam uma estrutura formada por anéis poliaromáticos condensados contendo grupos superficiais oxigenados ou nitrogenados. A acrilonitrila apresentou um comportamento particular quanto à difusão e polimerização no interior da estrutura MWW, formando materiais diferenciados dos análogos oxigenados / Abstract: Since the middle of the last century, molecular sieves represent an important class of materials, and revolutionized the oil cracking process, optimizing it. Furthermore many other applications referred to the structural properties, such as geometric selectivity, high superficial area and ionic exchange capacity. In the end of the 80¿, a new family of molecular sieves was reported, formed from the polymerization of carbon sources into the zeolites channels and cavities, followed by the removal of the inorganic template for acid or basic extraction. These well ordered porous carbons have been tested in diverse applications and presented promising results such as support for catalysts in fuel cells, materials for the production of supercapacitors and adsorbents of vitamins and other molecules with biological importance. The present work consists of the preparation and characterization of carbon molecular sieves from the polymerization of acrylonitrile, furfuryl alcohol and phenol/formaldehyde onto the channels of the zeolites with FAU and MWW structure. The results obtained indicate that, in the optimized processes the polymerization occurred only in the interior of the zeolites crystalline structure, or at least in its majority. The synthesized carbons, in general way, present a structure formed of condensed polyaromatics rings containing oxygenated or nitrogenated superficial groups. Acrylonitrile presented a different behavior of diffusion and polymerization in the interior of MWW structure, forming material well differentiated of the analogous oxygenated / Mestrado / Quimica Inorganica / Mestre em Química

Doctor of Philosophy / Department of Chemical Engineering / Liang T. Fan / Walter P. Walawender Jr / Carbon adsorbents, namely, activated carbons and carbon molecular sieves, can be variously applied in the purification and separation of gaseous and liquid mixtures, e.g., in the separation of nitrogen or oxygen from air; often, carbon adsorbents also serve as catalysts or catalyst supports. The formation of carbon adsorbents entails the modification of the original internal surfaces of carbonaceous substrates by resorting to a variety of chemical or physical methods, thereby augmenting the carbonaceous substrates' adsorbing capacity. The formation of carbon adsorbents proceeds randomly, which is mainly attributable to the discrete nature, mesoscopic sizes, and irregular shapes of the substrates utilized as well as to their intricate internal surface configuration. Moreover, any process of carbon-adsorbent formation may fluctuate increasingly severely with time. It is desirable that such a process involving discrete and mesoscopic entities undergoing complex motion and behavior be explored by means of the statistical framework or a probabilistic paradigm. This work aims at probabilistic analysis, modeling, and simulation of the formation of carbon adsorbents on the basis of mechanistic rate expressions. Specifically, the current work has formulated a set of linear and non-linear models of varied complexity; derived the governing equations of the models formulated; obtained the analytical solutions of the governing equations whenever possible; simulated one of the models by the Monte Carlo method; and validated the results of solution and simulation in light of the available experimental data for carbon-adsorbent formation from carbonaceous substrates, e.g., biomass or coal, or simulated data obtained by sampling them from a probability distribution. It is expected that the results from this work will be useful in establishing manufacturing processes for carbon adsorbents. For instance, they can be adopted in planning bench-scale or pilot-scale experiments; preliminary design and economic analysis of production facilities; and devising the strategies for operating and controlling such facilities.