The increased demand for an alternative form of fuel has raised a great interest towards exploring various metabolic pathways and enzymes in several microbial species for hydrocarbon production. In recent years, cyanobacteria have emerged as an attractive microbial host and cyanobacterial metabolic pathways were targeted for engineering to produce "drop in" fuels such as propane and butane. Whilst appealing, practicalities for producing biofuels in cyanobacteria remain challenging, requiring the identification and engineering of natural biocatalysts and their integration into metabolic processes. Cyanobacterial hydrocarbon biosynthesis arises from fatty acid metabolism involving a potential enzyme, aldehyde deformylating oxygenase (ADO), which catalyses the decarbonylation of long-chain fatty aldehydes to alkanes, mainly in the conversion of octadecanal (C17H35CHO) to heptadecane (C17H36) and formate. The substrate specificity and preferences for long-chain aldehyde by ADO necessitates a detailed kinetic and structural characterisation in order to optimise/engineer this enzyme for future biotechnological applications. Thus, the main objective was to identify a potential ADO enzyme that can be optimised for shorter chain alkane production. By studying the substrate specificity and reaction kinetics of different ADO enzymes, it was found that ADO from Prochlorococcus marinus MIT 9313 (PmADO) is a potential target for short chain alkane production. The crystal structural of PmADO was solved and further GC-MS analysis was carried out to identify the chemical origin of a mixture of long-chain fatty acid in the active site, originated from E. coli cells during recombinant over-expression and purification. It was suggested that the structure-guided protein engineering for short-chain alkane production should be carried out along with the removal of this adventitious ligand from the active site in order to increase the alkane production. Four important residues present at the entrance of the ligand-binding cavity were targeted and saturated mutagenesis was performed on PmADO to identify variants that excluded the long fatty acid ligands from the active site but have specificity and higher conversion rates for shorter chain aldehydes. This identified two variants, V41Y and A134F, with the A134F variant that not only exhibiting an improved activity and turnover value of PmADO by four-fold but also improved binding affinity for butyraldehyde by 2 times. Finally the improved variants were incorporated in a host organism (E. coli) and the possibilities for the development of a microbial platform for renewable propane synthesis based on a fermentative clostridial butanol pathway were explored. Four pathways were designed namely atoB-adhE2, atoB-TPC7, nphT7-adhE2 and nphT7-TPC7 routes, which utilise CoA intermediates selected to incorporate ADO as the terminal enzyme. When PmADO was co-expressed with these pathways, the engineered E. coli host produced propane. The atoB-TPC7-ADO pathway was the most effective in producing propane (220 ± 3 μg/L). By (i) deleting competing pathways, (ii) including a previously designed A134F variant ofPmADO with an enhanced specificity towards short-chain substrates, and (iii) including a ferredoxin-based electron supply system, the propane titre was increased up to 3.40 ± 0.19 mg/L. It was also shown that the best propane producing pathways are scalable in a 250 mL flask and in a large-scale (up to 30 L) fermentor setup. This thesis focuses on the detailed kinetics and structure-guided characterisation and engineering studies on the ADO enzyme for the development of a renewable microbial biofuel platform.

abstract: Membrane-based gas separation is promising for efficient propylene/propane (C3H6/C3H8) separation with low energy consumption and minimum environment impact. Two microporous inorganic membrane candidates, MFI-type zeolite membrane and carbon molecular sieve membrane (CMS) have demonstrated excellent thermal and chemical stability. Application of these membranes into C3H6/C3H8 separation has not been well investigated. This dissertation presents fundamental studies on membrane synthesis, characterization and C3H6/C3H8 separation properties of MFI zeolite membrane and CMS membrane. MFI zeolite membranes were synthesized on α-alumina supports by secondary growth method. Novel positron annihilation spectroscopy (PAS) techniques were used to non-destructively characterize the pore structure of these membranes. PAS reveals a bimodal pore structure consisting of intracrystalline zeolitic micropores of ~0.6 nm in diameter and irregular intercrystalline micropores of 1.4 to 1.8 nm in size for the membranes. The template-free synthesized membrane exhibited a high permeance but a low selectivity in C3H6/C3H8 mixture separation. CMS membranes were synthesized by coating/pyrolysis method on mesoporous γ-alumina support. Such supports allow coating of thin, high-quality polymer films and subsequent CMS membranes with no infiltration into support pores. The CMS membranes show strong molecular sieving effect, offering a high C3H6/C3H8 mixture selectivity of ~30. Reduction in membrane thickness from 500 nm to 300 nm causes an increase in C3H8 permeance and He/N2 selectivity, but a decrease in the permeance of He, N2 and C3H6 and C3H6/C3H8 selectivity. This can be explained by the thickness dependent chain mobility of the polymer film resulting in final carbon membrane of reduced pore size with different effects on transport of gas of different sizes, including possible closure of C3H6-accessible micropores. CMS membranes demonstrate excellent C3H6/C3H8 separation performance over a wide range of feed pressure, composition and operation temperature. No plasticization was observed at a feed pressure up to 100 psi. The permeation and separation is mainly controlled by diffusion instead of adsorption. CMS membrane experienced a decline in permeance, and an increase in selectivity over time under on-stream C3H6/C3H8 separation. This aging behavior is due to the reduction in effective pore size and porosity caused by oxygen chemisorption and physical aging of the membrane structure. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2015

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Na reação de desidrogenação oxidativa de propano (ODHP), propano reage com oxigênio da superfície de metais de transição para produzir propeno e água, em temperaturas de 300-700C. Porém, o propeno pode facilmente oxidar, formando CO e CO2. Assim, busca-se catalisadores que promovam a seletividade do propeno. Compostos tipo hidrotalcitas estão sendo apontados como catalisadores de grande potencial para a reação. Portanto, o principal objetivo desse trabalho foi sintetizar precursores tipo hidrotalcitas (contendo íons Ni2+, Mg2+ e Al3+ e tereftalato, heptamolibdato e decavanadato como ânions de compensação) para serem testados na reação de desidrogenação oxidativa de propano. Esses precursores foram sintetizados com uma razão Al/(Al+Ni+Mg)=0,5, variando a razão de Ni/Mg. Além disso, realizou-se a troca iônica do tereftalato (TA) por heptamolibdato (Mo7O24) e decavanadato (V10O28). Esses compostos foram calcinados, obtendo-se assim, óxidos mistos de NiMgAl, NiMgAlMo e NiMgAlV que foram testados como catalisadores na reação de ODHP. Para a determinação das propriedades dos catalisadores foram usadas as técnicas de caracterização: DRX, TGA, volumetria de N2, TPR, Raman e FTIR e ICP. Os resultados indicaram que os materiais tipo hidrotalcita foram obtidos com sucesso. No caso dos precursores preparados por troca iônica a cristalinidade foi menor que os da série NiMgAl-TA. Estes mesmos precursores quando calcinados apresentaram áreas muito altas. Nas três séries, os precursores calcinados são constituídos por óxidos mistos como NiO, NiMoO4, Ni2V2O7 cristalinos e espécies de alumínio e magnésio não detectados na DRX. No teste catalítico de ODHP, observou-se que com o aumento da conversão diminuía a seletividade de propeno, para os óxidos mistos que não continham molibdênio. Os catalisadores da série molibdênio foram os que obtiveram melhor desempenho com altas seletividades, mesmo em altas conversões e a série de cujo precursor foi o tereftalato foi a que exibiu maiores conversões, mas com seletividades menores que da série de Mo / In the reaction of oxidative dehydrogenation of propane (ODHP), propane reacts with oxygen in the transition metal surface to produce propylene and water at temperatures of 300-700 C. However, the propylene can easily oxidize, forming CO and CO2. Thus, catalysts that promote the selectivity of propylene are being searched. Hydrotalcites type compounds are identified as potential major catalysts for the reaction. Therefore, the main objective of this work was to synthesize precursors hydrotalcites type (containing Ni2+, Mg 2+ and Al 3+ ions and terephthalate, heptamolybdate and decavanadate as compensation anions) to test in the reaction of oxidative dehydrogenation of propane.These precursors were synthesized with Al/(Ni+Mg+Al) = 0.5 for different ratios of Ni/Mg. In addition, there was the ion exchange terephthalate (TA) by heptamolybdate (Mo7O24) and decavanadate (V10O28). These compounds were calcined, to obtain NiMgAl, NiMgAlMo and NiMgAlV mixed oxides and tested as catalysts in the ODHP reaction.For determining the properties of the catalysts the following characterization techniques were used: XRD, TGA, N2 volumetry, TPR, ICP, FTIR and Raman spectroscopy. The results indicated that the hydrotalcite-like materials were successfully obtained. In the case of the precursors prepared by ion exchange crystallinity was lower than those of NiMgAl-TA series. These same precursors when calcined had very high areas. In three series, the calcined precursors are comprised by mixed oxides such as crystalline NiO, NiMoO4, Ni2V2O7 and Al an Mg species not detected by XRD. In ODHP catalytic test, it was observed that with increasing conversion the propylene selectivity decreased to the mixed oxides containing no molybdenum. The catalysts of molybdenum series were those who performed better with high selectivity even at high conversions and the terephthalate precursor series shows the highest conversions, but with lower selectivity than Mo series

Orientador: Heloise de Oliveira Pastore / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-07T11:21:16Z (GMT). No. of bitstreams: 1 Albuquerque_Angela_D.pdf: 3045566 bytes, checksum: 280ada8d591e09adc89304ad0847ca95 (MD5) Previous issue date: 2006 / Resumo: A síntese da peneira molecular vanadoaluminossilicato com estrutura MWW, [V,Al]-MCM-22, foi realizada por tratamento hidrotérmico estático. Os materiais recém sintetizados, calcinados e trocados com íons H, Na ou K foram caracterizados por diversas técnicas analíticas e espectroscópicas. Foi preparado também um material por troca iônica do [Al]-MCM-22 com íons vanadila, o VO-[Al]-MCM-22. Todos os materiais apresentaram estrutura cristalina semelhante à observada para o [Al]-MCM-22. A presença de sítios redox (pares V/ V) foi monitorada por espectroscopia no UV -Vis com refletância difusa e por espectroscopia de infravermelho com transformada de Fourier (FTlR) com adsorção de CO a 100 K. As características ácidas foram monitoradas por FTlR com adsorção de NH3 e por dessorção termoprogramada (TPD) de NH3. Em testes catalíticos na reação de desidrogenação oxidativa do propano, os vanadoaluminossilicatos apresentaram maiores valores de conversão em relação aos aluminossilicatos, com valores de seletividade semelhantes. A troca iônica com íons alcalinos pode promover modulação na acidez dos catalisadores, tomando-os mais seletivos, por diminuir a seletividade para produtos de craqueamento. / Abstract: The synthesis of the vanadoaluminosilicate molecular sieve with MWW structure, [V,AI]-MCM-22, has been performed by static hydrothermal synthesis. As-synthesized, calcined, and H, Na or K ion-exchanged materiaIs were characterized by various analytical and spectroscopical techniques. It has also been prepared a material by ion-exchanging [AI]-MCM-22 with vanadyl ions, VO-[AI]-MCM-22. AlI the materiaIs presented a crystalIine structure similar to that observed for [AI]-MCM-22. The presence of redox sites (V/ V couples) was monitored by diffuse reflectance UV-vis spectroscopy and by Fourier transform infrared spectroscopy (FTlR) with CO adsorption at 100 K. Acid characteristics were monitored by FTlR with NH3 adsorption and by thermoprogrammed NH3 desorption (TPD). When tested in the oxidative dehydrogenation of propane catalytic reaction, vanadoaluminosilicates presented higher conversion values when compared to aluminosilicates, with similar selectivity data. Ion-exchange with alkaline ions may promote modulation in the acidity of the catalysts, making them more selective by decreasing their selectivity to products of cracking reactions. / Doutorado / Quimica Inorganica / Doutor em Quimica

Orientador: Arai Augusta Bernardez Pecora / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-12T19:26:31Z (GMT). No. of bitstreams: 1 Arini_RicardoGreber_M.pdf: 5502572 bytes, checksum: c19e6a830ce67a88c8959a10cd21aef8 (MD5) Previous issue date: 2008 / Resumo: Este trabalho teve como objetivo analisar experimentalmente um sistema de refrigeração por compressão de vapor operando com o hidrocarboneto propano (R290) em substituição ao refrigerante HCFC22, visando atender as necessidades do mercado atual de refrigeração comercial, que busca alternativas que atendam à exigência de substituição gradual dos refrigerantes hidroclorofluorcarbonados (HCFC's). O estudo foi realizado em um mini-tanque de resfriamento de leite, produzido comercialmente para operar com o refrigerante 22. Foram analisadas as influências da temperatura do fluido no interior do tanque e da temperatura do ar de resfriamento do condensador sobre parâmetros de desempenho do ciclo de compressão como: pressão de condensação, pressão de evaporação, coeficiente de desempenho, efeito frigorífico, trabalho de compressão, taxa específica de transferência de calor no condensador, temperatura do refrigerante na descarga do compressor e volume específico do refrigerante na aspiração do compressor. Além da análise energética, este trabalho apresenta a análise exergética do ciclo operando com R290 em comparação com o ciclo operando com R22. As medidas experimentais foram realizadas em condições de regime permanente, verificado quando não se observaram variações significativas na temperatura do refrigerante em diversos pontos do ciclo. A temperatura do fluido do tanque e a temperatura do ar de resfriamento do condensador foram mantidas constantes através de resistências elétricas imersas na água contida no tanque e na entrada do condensador, respectivamente. A análise de resultados mostrou que é possível a substituição do refrigerante R22 pelo R290 no sistema estudado, sendo observado que o sistema operando com R290 apresentou desempenho energético equivalente ao apresentado pelo R22. Foi verificado que a eficiência exergética do sistema operando com R290 foi igual ou superior à obtida com R22. Observou-se ainda um menor consumo de energia elétrica pelo sistema nos testes de resfriamento utilizando propano como refrigerante. / Abstract: In order to meet the requirements of the commercial refrigeration market, which demands for alternatives to substitute gradually the use of refrigerants such as hydroclorofluorcarbons (HCFC's), this research had the aim to analyze experimentally a mechanical vapor-compression refrigeration system operating with hydrocarbon propane (R290) as an alternative for R22. This study was made in a small tank for milk refrigeration, commercially built to operate with the refrigerant HCFC22. It was analyzed the influences of the factors: temperature of the water inside the tank and temperature of the cooling air at the entrance of the condenser, on the performance of the compression cycle. The following parameters were determined: evaporating pressure, condensing pressure, coefficient of performance, refrigeration capacity per unit mass of refrigerant flow, compression work, rate of heat transfer per unit mass of refrigerant flow at the condenser, refrigerant discharge temperature at the compressor outlet and specific volume of the refrigerant at the compressor inlet. In order to verify which refrigerant fluid realizes the best usage of the available work, it was made, besides an energetic analysis, a comparative exergetic analysis of the cycles. The experimental measures were made at steady state conditions, verified when no significant variations of refrigerant temperatures in several parts of the cycle were observed. The water temperature inside the tank and the air temperature, at the entrance of the condenser, were kept constant by using electrical resistances. The analysis of the results showed that R290 could be used as a substitute for R 22 to the studied system. It was observed that the energetic performance of the system working with R290 was better than the obtained using R22. The exergetic efficiency of the system using R290 was equal or greater than that obtained using R22. A less electrical energy consumption was obtained in the cooling experiments using R290 as refrigerant. / Mestrado / Termica e Fluidos / Mestre em Engenharia Mecânica

Orientadores: Maria Regina Wolf Maciel, Rubens Maciel Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-14T19:21:50Z (GMT). No. of bitstreams: 1 Quirino_FilipeAugustoBarral_M.pdf: 2305218 bytes, checksum: 4442e2951234a27e439a18c7f1fcd9d6 (MD5) Previous issue date: 2009 / Resumo: A desasfaltação do petróleo é um dos principais processos primários no refino de óleo cru. O estudo do processo de desasfaltação tem merecido atenção considerável nas últimas décadas, devido ao aumento das reservas de óleos crus pesados. No Brasil, grande parte das reservas exploradas produz óleos pesados, uma vez que a crescente redução no processamento de petróleos leves aliada à crescente demanda por combustíveis e lubrificantes de melhor qualidade força a indústria nacional de petróleo a desenvolver processos novos e mais eficientes para o refino do petróleo e seus resíduos. Os asfaltenos, encontrados em grande quantidade nos petróleos pesados, devem ser removidos do óleo de modo a se obter rendimentos mais altos no processo de craqueamento catalítico e produzir um óleo desasfaltado (DAO) mais leve. A extração de asfaltenos de um resíduo de petróleo com fluido supercrítico apresenta-se como uma alternativa viável para o processo de desasfaltação de resíduo de vácuo na produção de óleo lubrificante. Neste trabalho, foi estudado um processo de desasfaltação de petróleo pesado através da extração com fluido supercrítico. Toda a problemática do equilíbrio de fases do sistema foi avaliada através da construção computacional de diagramas de fases ternários para a mistura asfalto-óleosolvente. Foi selecionado um modelo termodinâmico capaz de predizer o equilíbrio de fases na desasfaltação para as condições supercríticas do solvente. Uma unidade de desasfaltação a propano foi simulada através de simulador comercial de processos, a fim de remover asfaltenos, resinas e demais componentes pesados de um óleo cru. Simulações foram realizadas considerando processo de extração líquido-líquido e separação supercrítica. Uma análise de sensitividade foi conduzida de modo a avaliar a influência das principais variáveis operacionais no processo. A eficiência da extração e a qualidade dos produtos foram verificadas com variações sistemáticas em variáveis independentes, de modo a obter rendimentos mais elevados na remoção de asfaltenos e recuperação de frações leves, visando a otimização do processo. O estabelecimento desta plataforma de simulação e os resultados obtidos foram de fundamental importância, por não serem facilmente encontrados na literatura aberta. A avaliação computacional da planta de desasfaltação servirá de base para o projeto e operação de planta piloto, a qual validará os dados obtidos. / Abstract: Petroleum deasphalting is one of the major primary processes in crude oil refining. The study of deasphalting has gained considerable attention in the last few decades due to the increase in heavy crude oil reserves. In Brazil, the majority of the explored reserves produce heavy oils. The increasing reduction in the processing of light oils, added to the increasing demand for fuels and lube oils of better quality, force the Brazilian oil industry to develop new and upgraded processes for the refining of crude oil and their residues. Asphaltenes, which are found in large amount in heavy oils, must be removed from the oil in order to get higher yields in the fluid catalytic cracking process (FCC) and to produce lighter deasphalted oil (DAO). The extraction of asphaltenes from petroleum residues though supercritical fluid is presented as a viable alternative for the vacuum-residue deasphalting, in the lube oil production. In this work, a deasphalting process of heavy crude oil through supercritical fluid extraction was studied. All the problematic of the system phase equilibrium was evaluated through the computational construction of phase ternary diagrams for the asphalt-oil-solvent mixture. A thermodynamic model capable to predict the phase behavior in the deasphalting process for the supercritical conditions of the solvent was selected. A propane deasphalting unit was simulated using a commercial process simulator, in order to remove asphaltenes, resins and heavy components from the crude. Simulations were carried out considering liquid-liquid extraction and supercritical separation. A sensitivity analysis was carried out in order to evaluate the influence of the main operational variables on this process. The efficiency of the extraction and the product quality was verified with systematic variations in the independent variables, in order to obtain higher yields in asphaltene removal and in light oil fractions recovery, aiming the process optimization. The establishment of this kind of simulation as well as the obtained results was very important because they are not easily found in the open literature. The computational evaluation of the deasphalting plant will serve as basis for operation and design of a pilot plant, which can validate the simulation data. / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

The maximum theoretical energy efficiency of fuel cells is much larger than those of the steam-power-turbine cycles that are currently used for generating electrical power. Similarly, direct hydrocarbon fuel cells, DHFCs, can theoretically be much more efficient than hydrogen fuel cells. Unfortunately the current densities (overall reaction rates) of DHFCs are substantially smaller than those of hydrogen fuel cells. The problem is that the exchange current density (catalytic reaction rate) is orders of magnitude smaller for DHFCs. Other work at the University of Ottawa has been directed toward the development of polymer electrolytes for DHFCs that operate above the boiling point of water, making corrosion rates much slower so that precious metal catalysts are not required. Propane (liquefied petroleum gas, LPG) was the hydrocarbon chosen for this research partly because infrastructure for its transportation and storage in rural areas already exists. In this work nickel based catalysts, an inexpensive replacement for the platinum based catalysts used in conventional fuel cells, were examined using density functional theory, DFT. The heats of propane adsorption for 3d metals, when plotted as a function of the number of 3d electrons in the metal atom, had the shape of a volcano plot, with the value for nickel being the peak value of the volcano plot. Also the C-H bond of the central carbon atom was longer for propane adsorbed on nickel than when adsorbed on any of the other metals, suggesting that the species adsorbed on nickel was less likely to desorb than those on other metals. The selectivity of the propyl radical reaction was examined. It was found that propyl radicals

<p>The recent surge in shale gas production led to increases in alkane resources across the United States. One promising approach to convert the alkanes to higher value products is through dehydrogenation and oligomerization processes. This conversion to alkenes, if done in small modular units near the shale wells further aids in the ease of transportation and distribution of the final products. However, having highly selective processes is a major hindrance to improve the economic feasibility of the modular processes. Theoretical studies are of great significance to analyze detailed reaction mechanisms and identify the reaction pathways that leads to unselective product formations. These studies further enable the search for selective catalysts for any given chemistry based on descriptor analysis. Therefore, in this work Density Function Theory and Ab-initio Molecular Dynamics methods are used in conjunction with microkinetic modeling analyses to investigate the complex reaction networks involved in the shale gas conversion. Specifically, the work focuses on propane dehydrogenation (PDH) on alloy surfaces along with ethylene oligomerization on zeolite catalysts.</p><p> A major part of thesis is focused on finding selective and stable alloy catalysts for PDH chemistry. The initial work focused on understanding the selectivity, activity, and stability differences between 1:1 intermetallic alloys (PdIn) and the pure metal surfaces. This combined experimental and computational study shed light on the important role of step surfaces in understanding the activity trends across alloys. Through a detailed microkinetic analysis and simplified rate expression analysis, a novel selectivity descriptor in terms of effective barriers for propane C-H bond breaking and propyne C-C bond breaking was derived for propylene formation. This newly proposed descriptor showed greater fidelity for predicting the trends in experimental selectivities for a small set of Pd alloys than the previously proposed selectivity descriptors. Building upon these insights, a high throughput screening framework using graph-theory algorithms and python-based databasing has been developed to identify trends across a larger set of alloy combinations. The framework helped us identify a novel set of alloys that have not been explored until now for this chemistry. These alloy combinations were then experimentally tested and shown to have high selectivities for propylene formation and along with stabilities close to benchmark Pt-Sn catalysts. Detailed transition state analysis on terraces shows that the undesired C-C bond breaking pathways involves larger surface atom ensembles (4-5 atoms) while the C-H bond breaking involves smaller surface atom ensembles (1-2 atoms). This led to the conclusion that the site-isolation of active metal atoms is important to increase the selectivities for propylene formation. More importantly the combination of detailed mechanistic and screening studies using graph-theory methods shows a generalized framework towards finding new catalysts spaces for complex chemistries.</p><p>The work on ethylene oligomerization on the other hand is focused on understanding the role of mobility of active Ni species in the zeolites towards isomerization and deactivation reaction mechanisms. For this specific project, we have used state-of-the-art AIMD methods, including potential of mean force calculations, for accurate estimation of free energies for the reaction intermediates and transition states. The thermodynamic and kinetic analyses show that the reaction pathways involving mobile intermediates have the highest rates towards butene formations even under pressures lower than 1 bar. Further the isomerization step is found to be feasible on Ni-ethyl complex in agreement with experiments. Finally, the mobile complexes were shown to dimerize through alkyl bridged complexes and the generated complex has higher barriers for C-C bond formation than the isolated complex indicating that these are likely pathways for catalyst deactivation. This mechanistic understanding paves the way for fine-tuning the reaction conditions as well as ways in which the active site can be speciated inside the zeolitic frameworks to increase the selectivity towards 1-butene and reduce deactivation.</p>

To date there exists a great deal of energetic and economic inefficiency in the separation of olefins from paraffins because the principal means of achieving industrial purity requirements is accomplished with very energy intensive cryogenic distillation. Mitigation of the severe energy intensity of the propylene/propane separation has been identified as one of seven chemical separations which can change the landscape of global energy use, and membranes have been targeted as an emerging technology because they offer scalability and lower capital and operating costs. The focus of this work was to evaluate a new direction of material development for the very industrially relevant propylene/propane separation using membranes. The objective was to develop a rational design approach for generating highly selective membranes using a relatively new platform of materials known as polyimides of intrinsic microporosity (PIM-PIs), the prospects of which have never been examined for the propylene/propane separation. Structurally, PIMs comprise relatively inflexible macromolecular architectures integrating contortion sites that help disrupt packing and trap microporous free volume elements (< 20 Å). To date most of the work reported in the literature on this separation is based on conventional low free volume 6FDA-based polyimides which in the best case show moderate C3H6/C3H8 selectivities (<20) with C3H6 permeabilities too low to garner industrial interest. Due to propylene and propane’s relatively large molecular size, we hypothesized that the use of more open structures can provide greater accessibility to the pores necessary to enhance membrane sieving and flux. It has been shown for numerous key gas separations that introduction of microporosity into a polymer structure can defy the notorious permeability/selectivity tradeoff curve and induce simultaneous boosts in both permeability and selectivity. The cornerstone approach to designing state of the art high performance PIM-PI membranes for the light gas separations involving maximizing the intra-segmental rigidity of the polymer chain was applied to the C3H6/C3H8 separation. A study regarding a stepwise maximization of intra-molecular rigidity and its effects on C3H6/C3H8 permeation was evaluated by conducting systematic structural modifications to high performance PIM-PIs. State of the art increases in performance were observed in pure-gas measurements as there were significant increases in C3H6/C3H8 selectivity and C3H6 permeability upon doing so. However, mixed-gas measurements showed that there were 65% losses in selectivity due to competitive sorption and mainly plasticization. Based on the conclusions drawn, a fundamental departure from conventional PIM design principles was used, instead emphasizing enhancing inter-chain interactions by introduction of a flexible diamine and functionalization with hydroxyl groups to attempt to immobilize the polymer chains. In doing so, the polymer chains may be able to pack more efficiently and upon sub-Tg annealing cause a microstructural reorganization to form a coplanarized configuration due to the combination of inter-chain charge transfer complexes (CTC) and hydrogen bonding networks. This approach successfully mitigated plasticization, but more importantly resulted in a tightening of the microstructure, especially in the ultra-microporous range (<7 Å) thereby yielding significant boosts in C3H6/C3H8 selectivity. Based on the PIM platform and novel polymer design approach thereof, the C3H6/C3H8 upper bound was thrust to new limits and led to the generation of the most selective solution processable polymers reported for the C3H6/C3H8 separation. Although the PIM platform has redefined the polymer upper bound, the permeability/selectivity tradeoff still endures, as the C3H6 permeabilities were on the order of 1 to 3.5 Barrer for the most selective polymers. To bridge that gap in permeability, several different approaches were taken. For the first time attempted for C3H6/C3H8 separation, high temperature heating of a PIM-PI to form thermally-rearranged and carbon molecular sieve membranes was employed. The TR membrane showed increased C3H6 permeability and about 50% losses in C3H6/C3H8 selectivity, while the CMS membrane formed at 600 oC showed modest gains in C3H6/C3H8 selectivity with significant improvements in C3H6 permeability. Finally, hybrid nanocomposite membranes incorporating a metal-organic framework structure into a PIM-PI matrix was used. ZIF-8, which has demonstrated high diffusive selectivities for C3H6/C3H8, was dispersed within the polymer, since previous work by the Koros group indicated that its incorporation into polyimide matrices can facilitate major improvements in both C3H6/C3H8 selectivity and C3H6 permeability compared to the respective neat polymer. Focus was directed towards attempting to improve polymer/nanoparticle adhesion by enhancing the interactions between the polymer and filler particles to mitigate the interfacial defects notorious in mixed-matrix membranes (MMM). To do so, ZIF-8 was dispersed into one of the best performing hydroxyl functionalized PIM-PI for the C3H6/C3H8 separation. The highest loaded mixed-matrix membrane in a glassy polymer to date of 65% (w/w) was achieved. The membranes showed pure-gas selectivities ranging from 34 with 10 Barrer at 30% loading to 43 with 38 Barrer at 65% loading. Strong performance and plasticization resistance were sustained in mixed-gas experiments even to feed pressures approaching the vapor pressure of the C3H6/C3H8 mixture, as selectivities well over 20 were achieved with high permeabilities, thereby demonstrating the potential commercial viability. Based on the work reported in this dissertation, we hope to help lay a framework to be able to tailor membrane performance and future membrane design to meet the demands of the different applications of the propylene/propane separation and hence show that there can be a marketplace for membranes in the separation. These include the debottlenecking of cryogenic distillation towers for production of polymer-grade propylene (99.5%) to reduce the associated extensive energy load, production of chemical-grade propylene (92-95% propylene), or for the recovery and recycling of olefins from reactor purges of petrochemical processes.

A significant part of the environmental impact of a heat pump isgenerally related to the direct emission of the refrigerant fluid during thelife time of the machine. Although the Montreal Protocol has alreadylargely secured its status as a success story by cutting the ozone deplentationrefrigerants drastically, we still have to deal with the challengesresulting from climate change.Natural refrigerants such as Propane permits to design more ecofriendlysystem without sacrificing the performance of the machine. Thethesis work is part of a European project called Next Generation of HeatPumps working with Natural fluids (NxtHPG) whose primary aim is thedevelopment of heat pumps working with Natural refrigerant that aresafe, reliable, with high efficiency and high capacity. Royal Institute oftechnology (KTH) is one of the partner of the project and responsiblefor the experimental campaign of two large propane heat pumps: an airsource heat pump (Case 1 ) and a ground source heat pump suitablefor boreholes (Case 2 ). Few cases in literature report on studies aboutlarge capacity heat pumps using propane as refrigerant.This thesis project focuses on the experimental evaluation of theCase 2 from an energy point view. The safety issues about the use of flammable refrigerant, i.e propane, are briefly reported; however theyare not considered strictly part of the thesis work since they are coveredin other phases of NxtHPG project. Experimental tests for Case 1 werenot conducted during this thesis work because of delays in the prototypedelivery from the manufacturer. However, concerns about the hydraulicloop of the test rig of both the heat pumps was identified and a newdesign was suggested and implemented.During the experimental campaign for Case 2 a significant numberof tests were performed according to a specific text matrix definedfrom the EN 14285 standard. A simple heat pump model has beenused to evaluate the overall performance of the machine from the directmeasurements. The heat pump components (compressors, condenser,evaporator, expansion valve) have been analysed in details by definingspecific analysis model for each one. The results have been comparedwith the manufacture expectation.The prototypes demonstrated to have potentially very good performance,since in the first set of tests the machine behaved as expectedby the IMST-ART software. On the other hand, a drop of the unitefficiency and capacity have been registered during the experimentalcampaign for similar working condition. Two different explanations areinvestigated to clarify the strange phenomenon. The first hypothesisconsiders minor internal damage in the compressor, as check valve leakage;consequence of the use of the compressor in a tandem layout. Itgenerates a back-flow in the non working compressor. The second explanationregards inert gas infiltration in the system. On the otherhand they are not able to explain entirely the system issues and theyneed to be confirmed by the manufacturer analysis of the open compressor.The further improvements, proposed and discussed with themanufacture companies involved, can help to solve the question markson the strange system behaviour during the future work. The nextexperimental campaign for Case 1 that will start on April 2015.The software IMST-ART, used to predict the performance of theheat pump, is demonstrated to be a fast and useful tool. The model ofthe software for propane as refrigerant and brazed plate heat exchangerpredicts adequately the experimental measurement. / Una parte significativa dell’impatto ambientale relativo a una pompadi calore è legato alle emissioni dirette di refrigerante durante ilperiodo di vita della macchina. Nonostante l’accordo di Montreal siagià stato considerato come un successo storico per il drastico taglio deirefrigeranti dannosi per lo strato di ozono, bisogna ancora fronteggiarele sfide relative al cambiamento climatico.Refrigeranti naturali, come il Propano, permettono di realizzaremacchine più ambientalmente compatibili senza però sacrificare le prestazionidella macchina stessa. Questo lavoro di tesi fa parte di unprogetto Europeo chiamato Next Generation of Heat Pumps workingwith Natural fluids (NxtHPG), in cui obiettivo primario è quello di svilupparepompe di calore che lavorano con fluidi Naturali che allo stessotempo siano sicure, affidabili, con elevata efficienza e taglia.Royal Institute of technology (KTH) è uno dei partner del progettoe anche responsabile della campagna sperimentale di due pompe dicalore a propano di grossa taglia: una pompa ad aria Case 1 e unageotermicaCase 2. Sono pochi gli esempi in letteratura che riguardanolo studio di macchine di questo tipo di grande taglia, questo costituiscela novità del lavoro.Il lavoro di tesi presentato è incentrato principalmente sulla valutazionesperimentale da un punto di vista energetico di Case 2. Leproblematiche legate alla sicurezza legate all’utilizzo di refrigeranti infiammabili,quale è il propano, sono solo citate; d’altra parte non sonoconsiderate strettamente facenti parte del lavoro di tesi in quando altrefasi del progetto NxtHPG sono incentrate su questo argomento.Misure sperimentali per Case 1 non sono state condotte durante illavoro di tesi a causa di ritardi nella consegna dei prototipi da parte dell’aziendaproduttrice. Ad ogni modo sono stati individuate problematichelegate ai circuiti idraulici dell’installazione sperimentale di entrambele pompe di calore e successivamente risolte con l’implementazione diuna nuova proposta di circuito idraulico.Durante la campagna sperimentale di Case 2, sono stati svolti undiscreto numero di misurazioni secondo una ben specifica test matrixderivata dalla normativa europea EN 14285. Un semplice modello dipompa di calore è stato utilizzato per la valutazione delle prestazionigenerali della macchina a partire dalle misurazioni dirette. I componenti della pompa di calore, quali compressore, condensatore, evaporatore,valvola di espansione, sono state analizzati separatamente definendouno specifico modello per ognuno di essi e comparato con i risultatiattesi dai produttori.Il prototipo di Case 2 dimostra avere ottime potenzialità come prestazioni,in quanto, durante il primo set di test, il comportamento dellamacchina era in linea con le previsioni del software IMST-ART. D’altraparte, durante la campagna sperimentale, si è evidenziato un fortecalo delle prestazioni nonostante le condizioni di funzionamento fosseropressoché simili. Per spiegare questa anomalia, due differenti ipotesisono state formulate. La prima assume la presenza di di deterioramentiminori nel compressore, come perdite nella valvola di non ritorno (checkvalve), conseguente ad l’utilizzo in configurazione tandem. Si genererebbeun flusso riverso di refrigerante nel compressore non funzionante.La seconda ipotesi riguarda infiltrazione di gas inerte all’interno dellamacchina. D’altra parte tali ipotesi non sono in grado di spiegareinteramente le problematicità nel sistema e hanno necessità di essereconfermate dall’analisi a compressore aperto da parte della aziendaproduttrice.Successivi perfezionamento dei prototipi sono stati proposti e discussicon le aziende produttrici coinvolte, e questo permetterebbe dirispondere ai punti di domanda riguardo lo strano comportamento delsistema. La prossima campagna sperimentale per Case 2 inizierà adAprile 2015. Il software IMST-ART, usato per predire le performancedella pompa di calore, ha dimostrato essere uno strumento veloce e utile.Il modello implementato nel software per il propano e per gli scambiatoridi calore a piatti predice adeguatamente le misure sperimentali. / Next Generation of Heat Pumps working with Natural fluids (NxtHPG)