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[[Image:LLNL-microreactor.jpg|right|frame|Microrreator desenvolvido no [[Laboratório Nacional de Lawrence Livermore|LLNL]] utiliza técnicas de micromaquinaria para miniaturizar o design do mesmo. Aplicações incluem processamento de combustíveis para geração de [[Hidrogênio molecular|hidrogênio]], [[Síntese química|síntese]] e estudos de biorreatores.]]
[[Image:LLNL-microreactor.jpg|right|frame|Reator químico diminuto confecionado com a técnica da [[microfabricação]]]]
 
Um '''microrreator''' é um [[reator químico]] de pequenas dimensões.
Um '''microrreator''' ou '''reator microestrutrurado''' ou '''reator microcanalizado''' é um dispositivo em que reações químicas ocorrem em um espaço de dimensões abaixo de 1 milímetro; a forma típica de tal confinamento são microcanais.<ref name=Watts>''Recent advances in synthetic micro reaction technology'' Paul Watts and Charlotte Wiles [[Chem. Commun.]], '''2007''', 443 - 467, {{DOI|10.1039/b609428g}}</ref> Microrreatores são estudados no campo da engenharia de microprocessos, juntamente com outros dispositivos — como micropermutadores de calor — em que processos físicos ocorrem. Um microrreator é, geralmente, um [[Reator químico|reator]] de fluxo contínuo (em contraste com um reator em batelada).<ref>{{citar web|último =Bhangale|primeiro =Atul|título=Enzyme-Catalyzed Polymerization of End-Functionalized Polymers in a Microreactor|url=http://pubs.acs.org/doi/abs/10.1021/ma301178k|publicado=Macromolecules}}</ref><ref>{{citar web|último =Bhangale|primeiro =Atul|título=Continuous Flow Enzyme-Catalyzed Polymerization in a Microreactor|url=http://pubs.acs.org/doi/abs/10.1021/ja111346c|obra=JACS}}</ref> Microrreatores oferecem muitas vantagens sobre reatores de dimensão convencional, incluindo vastos avanços na eficiência energética, velocidade reacional e rendimento, segurança, confiabilidade, escalabilidade, atendimento de produção de demanda e um grau deverasmente superior de [[Teoria de controle|controle]].
 
Os microrreatores estão ainda em fase de investigação e desenvolvimento. A teoria mostra que estes reatores podem usados com vantagem para reações perigosas, reações não lineares [[Reação exotérmica|exotérmicas]] em que podem ocorrer pontos quentes, e em [[Exame laboratorial|testes clínicos]] portáteis.
==História==
Microrreatores de [[Gás|fase gasosa]] têm uma longa história de estudo contudo aqueles de [[Líquido|fase líquida]] começaram a surgir no final da década de 1990.<ref name=Watts/> Um dos primeiros microrreatores com [[Trocador de energia térmica|permutadores de calor]] de alta performance foi confeccionado no início da década de 1990 pelo Departamento Central de Experimentação — ''Hauptabteilung Versuchstechnik'', HVT — do [[Forschungszentrum Karlsruhe]],<ref name=schubi01>{{citar periódico
|último1 = Schubert
|primeiro1 = K.
|último2 = Brandner
|primeiro2 = J.
|último3 = Fichtner
|primeiro3 = M.
|último4 = Linder
|primeiro4 = G.
|último5 = Schygulla
|primeiro5 = U.
|último6 = Wenka
|primeiro6 = A.
|autorlink =
|coautor=
|título= Microstructure Devices for applications in thermal and chemical process engineering
|periódico= Microscale Thermophysical Engineering
| volume = 5
|número= 1
|páginas= 17&mdash;39
|publicado= Taylor & Francis
|local=
|data=janeiro de 2001
| url =
| issn = 1556-7265
| doi = 10.1080/108939501300005358
| id =
|acessodata= }}</ref> na Alemanha, com técnicas de micromaquinaria mecânica que foram subdescobertas geradas da fabricação de [[Spray|vaporizadores]] de separação para o [[Urânio enriquecido|enriquecimento de urânio]].<ref name=schubi01/> Como a exploração em tecnologia nuclear tornou-se drasticamente reduzida na Alemanha, permutadores de calor microestruturados tornaram-se objetos de estudo devido a sua capacidade de lidar com reações químicas altamente exotérmicas e perigosas. Esse novo conceito, inicialmente conhecido por nomes como "tecnologia de microrreação" ou "engenharia de microprocessos", foi futuramente desenvolvido por diversas instituições de pesquisa. Como um exemplo de 1997 que envolveu um [[Acoplamento diazoico|azoacoplamento]] em um reator de [[pyrex]] com canais de dimensões de 90 [[Micrómetro (unidade de medida)|mícrons]] de profundidade por 190 [[Micrómetro (unidade de medida)|mícrons]] de comprimento.<ref name=Watts/>
 
Os microreatores podem ser combinados em paralelo para produzir grandes quantidades de produto. No entanto, como a reação ocorre em contentores fechados o perigo de um [[reagente]] ou produto se libertar está limitado. Como a razão área de contacto/[[volume]] é alta, o calor de reação dissipa-se rapidamente e os pontos quentes são evitados.
==Benefícios==
Utilizar microrreatores é, de certa forma, diferente de utilizar um recipiente de vidro. Estes reatores podem ser uma ferramenta valiosa nas mãos de um químico experiente ou um engenheiro de reação.
 
{{esboço-química}}
<big><math>\circ</math>Microrreatores possuem coeficientes de transporte de calor de, no mínimo, <math>\mathrm{1\ \frac{MW}{m^3\ K}}</math>a <math>\mathrm{500\ \frac{MW}{m^3\ K}\ ;}</math>enquanto que um recipiente convencional de vidro de 1 L possui <math>\mathrm{\thicksim10\ \frac{kW}{m^3\ K}.}</math> Além disso, microrreatores podem remover calor de maneira mais eficiente que outros recipientes e até mesmo reações críticas como [[Nitração|nitrações]] podem ser efetuadas com segurança a altas temperaturas.<ref>D.Roberge, L.Ducry, N.Bieler, P.Cretton, B.Zimmermann, Chem. Eng. Tech. 28 (2005) No. 3, [http://www.lonza.com/group/en/company/news/publications_of_lonza.-ParSys-0002-ParSysdownloadlist-0001-DownloadFile.pdf/1_050510_Microreactor%20Technology%20A%20Revolution%20for%20the%20Fine%20Chemical%20and%20Pharmaceutical%20Industries.pdf online available]</ref> ''Hot spots'' de temperatura assim como a duração de exposição a alta tempratura devido a exotermicidade decaem notavelmente. Ademais, microrreatores podem possibilitar melhores estudos de [[Cinética química|cinética]], devido ao gradiente de temperatura local — que afeta as taxas de reação — ser muito inferior que em qualquer recipiente de batelada. Aquecer ou resfriar um microrreator também é deverasmente mais rápido e a temperatura mínima de operação pode chegar a <math>\mathrm{-100^oC\ .}</math> Como resultado de uma transferência de calor superior, a temperatura reacional pode ser muito maior que em reatores convencionais. Muitas reações a baixas temperaturas — como química organometálica — podem ser realizadas a <math>\mathrm{-10^oC}</math> contra a faixa <math>\mathrm{-50^oC \leftrightarrow-78^oC}</math>utilizada em equipamentos e vidrarias laboratoriais.
 
[[Categoria:Material de laboratório]]
<big><math>\circ</math>Microrreatores são operados continuamente. Isso permite o processamento subsequente de intermediários instáveis e evita contratempos típicos de reatores convencionais. Especialmente na química de baixa temperatura com tempo de reação da ordem de milissegundos não são mais armazenadas por horas até o dosamento de reagentes é terminado e a próxima reação seja executada. Esse trabalho rápido poupa o decaimento de intermediários desejados e frequentemente propicia melhor seletividade.<ref>T.Schwalbe, V.Autze, G.Wille: Chimica 2002, 56, p.636, see also [http://www.mrsp.net/MRSP_Chimica_Oggi.pdf Microflow Synthesis]</ref>
 
<big><math>\circ</math>Operação contínua e misturas causam um perfil diferente de concentração quando comparado com um processo em batelada. Na batelada, um reagente A é adicionado e um reagente B é adicionado lentamente. Outrossim B encontra inicialmente um alto excesso de A. Em um microrreator, A e B são misturados quase instantaneamente e B não será exposto a um excesso de A. Essa característica pode tanto ser uma vantagem como uma desvantagem dependendo do mecanismo reacional — é importante levar em conta os diferentes perfis de concentração.
 
<big><math>\circ</math>Although a bench-top microreactor can synthesize chemicals only in small quantities, scale-up to industrial volumes is simply a process of multiplying the number of microchannels. In contrast, batch processes too often perform well on R&D bench-top level but fail at batch pilot plant level.<ref>T.Schwalbe, V.Autze, M. Hohmann, W. Stirner: Org.Proc.Res.Dev 8 (2004) p. 440ff, see also [http://www.mrsp.net/MRSP_lo-res.pdf Continuous process research and implementation from laboratory to manufacture]</ref>
 
<big><math>\circ</math>Pressurisation of materials within microreactors (and associated components) is generally easier than with traditional batch reactors. This allows reactions to be increased in rate by raising the temperature beyond the boiling point of the solvent. This, although typical Arrhenius behaviour, is more easily facilitated in microreactors and should be considered a key advantage. Pressurisation may also allow dissolution of reactant gasses within the flow stream.
 
==Problemas==
* Although there have been reactors made for handling particles, microreactors generally do not tolerate particulates well, often clogging. Clogging has been identified by a number of researchers as the biggest hurdle for microreactors being widely accepted as a beneficial alternative to batch reactors. So far, the so-called microjetreactor<ref>{{citar periódico|último =Wille|primeiro =Ch|autor2 =Gabski, H.-P |autor3 =Haller, Th |autor4 =Kim, H |autor5 =Unverdorben, L |autor6 = Winter, R |título=Synthesis of pigments in a three-stage microreactor pilot plant—an experimental technical report|periódico=Chemical Engineering Journal|ano=2003|volume=101|número=1-3|páginas=179–185|doi=10.1016/j.cej.2003.11.007}} and literature cited therein</ref> is free of clogging by precipitating products. Gas evolved may also shorten the residence time of reagents as volume is not constant during the reaction. This may be prevented by application of pressure.
* Mechanical pumping may generate a pulsating flow which can be disadvantageous. Much work has been devoted to development of pumps with low pulsation. A continuous flow solution is [[electroosmotic flow]] (EOF).
*Typically, reactions performing very well in a microreactor encounter many problems in vessels, especially when scaling up. Often, the high area to volume ratio and the uniform residence time cannot easily be scaled.
* [[Corrosion]] imposes a bigger issue in microreactors because area to volume ratio is high. Degradation of few µm may go unnoticed in conventional vessels. As typical inner dimensions of channels are in the same order of magnitude, characteristics may be altered significantly.
 
==T Reatores==
One of the simplest forms of a microreactor is a 'T' reactor. A 'T' shape is etched into a plate with a depth that may be 40 [[micrometre]]s and a width of 100 micrometres: the etched path is turned into a tube by sealing a flat plate over the top of the etched groove. The cover plate has three holes that align to the top-left, top-right, and bottom of the 'T' so that fluids can be added and removed. A solution of reagent 'A' is pumped into the top left of the 'T' and solution 'B' is pumped into the top right of the 'T'. If the pumping rate is the same, the components meet at the top of the vertical part of the 'T' and begin to mix and react as they go down the trunk of the 'T'. A solution of product is removed at the base of the 'T'.
 
==Aplicações==
[[Image:Syrris Chip.jpg|right|frame|Glass Microreactors involve microfabricated structures to allow [[flow chemistry]] to be performed at a microscale. Applications include Compound Library Generation, Process Development and Compound Synthesis]]
 
===Síntese===
Microreactors can be used to synthesise material more effectively than current batch techniques allow. The benefits here are primarily enabled by the [[mass transfer]], [[thermodynamics]], and high surface area to volume ratio environment as well as engineering advantages in handling unstable intermediates. Microreactors are applied in combination with [[photochemistry]], [[electrosynthesis]], [[multicomponent reaction]]s and [[polymerization]] (for example that of [[butyl acrylate]]). It can involve liquid-liquid systems but also solid-liquid systems with for example the channel walls coated with a [[heterogeneous catalyst]]. Synthesis is also combined with online purification of the product.<ref name=Watts/> Following [[Green Chemistry]] principles, microreactors can be used to synthesize and purify extremely reactive [[Organometallic]] Compounds for [[Atomic Layer Deposition|ALD]] and [[Chemical vapor deposition|CVD]] applications, with improved safety in operations and higher purity products.<ref>''Method of Preparing Organometallic Compounds Using Microchannel Devices'', '''2009''', Francis Joseph Lipiecki, Stephen G. Maroldo, Deodatta Vinayak Shenai-Khatkhate, and Robert A. Ware, [http://www.freepatentsonline.com/y2009/0023940.html US 20090023940]</ref><ref>''Purification Process Using Microchannel Devices'', '''2009''', Francis Joseph Lipiecki, Stephen G. Maroldo, Deodatta Vinayak Shenai-Khatkhate, and Robert A. Ware, [http://www.freepatentsonline.com/y2009/0020010.html US 20090020010]</ref>
 
In microreactor studies a [[Knoevenagel condensation]]<ref>''Knoevenagel condensation reaction in a membrane microreactor'' Sau Man Lai, Rosa Martin-Aranda and King Lun Yeung [[Chem. Commun.]], '''2003''', 218 - 219, {{DOI|10.1039/b209297b}}</ref> was performed with the channel coated with a [[zeolite]] catalyst layer which also serves to remove water generated in the reaction. The same reaction was performed in a microreactor covered by polymer brushes.<ref>F. Costantini, W. P. Bula, R. Salvio, J. Huskens, H. J. G. E. Gardeniers, D. N. Reinhoudt and W. Verboom [[J. Am. Chem. Soc.]], '''2009''',131, 1650, {{DOI|10.1021/Ja807616z}}</ref>
 
:[[Imagem:Knoevenagelmicroreactor.png|400px|Knoevenagel condensation application]]
A [[Suzuki reaction]] was examined in another study<ref>''Instantaneous Carbon-Carbon Bond Formation Using a Microchannel Reactor with a Catalytic Membrane'' Yasuhiro Uozumi, Yoichi M. A. Yamada, Tomohiko Beppu, Naoshi Fukuyama, Masaharu Ueno, and Takehiko Kitamori [[J. Am. Chem. Soc.]]; '''2006'''; 128(50) pp 15994 - 15995; (Communication) {{DOI|10.1021/ja066697r}}</ref> with a palladium catalyst confined in a [[polymer network]] of [[polyacrylamide]] and a [[triphenylphosphine|triarylphosphine]] formed by [[interfacial polymerization]]:
 
:[[Imagem:Suzukimicroreactorreaction.png|400px|Suzuki reaction application]]
 
The [[combustion]] of [[propane]] was demonstrated to occur at temperatures as low as 300&nbsp;°C in a microchannel setup filled up with an [[aluminum oxide]] lattice coated with a [[platinum]] / [[molybdenum]] catalyst:<ref>''Low temperature catalytic combustion of propane over Pt-based catalyst with inverse opal microstructure in a microchannel reactor'' Guoqing Guan, Ralf Zapf, Gunther Kolb, Yong Men, Volker Hessel, Holger Loewe, Jianhui Ye and Rudolf Zentel [[Chem. Commun.]], '''2007''', 260 - 262, {{DOI|10.1039/b609599b}}</ref>
 
:[[Imagem:PropaneCombustionInmicrochannelreactor.png|400px|Propane combustion application]]
 
''''''
 
=== Enzyme catalyzed polymer synthesis ===
''''''
Enzymes immobilized on solid supports are increasingly used for greener, more sustainable chemical transformation processes. Microreactors are used to study enzyme-catalyzed ring-opening polymerization of ε-caprolactone to polycaprolactone. A novel microreactor design developed by Bhangale et al.<ref>{{citar web|último =Atul|primeiro =Bhangale|título=Enzyme-Catalyzed Polymerization of End-Functionalized Polymers in a Microreactor|url=http://pubs.acs.org/doi/abs/10.1021/ma301178k|obra=Macromolecules}}</ref><ref>{{citar web|último =Bhangale|primeiro =Atul|título=Continuous Flow Enzyme-Catalyzed Polymerization in a Microreactor|url=http://pubs.acs.org/doi/abs/10.1021/ja111346c}}</ref> enabled to perform heterogeneous reactions in continuous mode, in organic media, and at elevated temperatures. Using microreactors, enabled faster polymerization and higher molecular mass compared to using batch reactors. It is evident that similar microreactor based platforms can readily be extended to other enzyme-based systems, for example, high-throughput screening of new enzymes and to precision measurements of new processes where continuous flow mode is preferred. This is the first reported demonstration of a solid supported enzyme-catalyzed polymerization reaction in continuous mode.
 
===Análise===
Microreactors can also enable experiments to be performed at a far lower scale and far higher experimental rates than currently possible in batch production, while not collecting the physical experimental output. The benefits here are primarily derived from the low operating scale, and the integration of the required sensor technologies to allow high quality understanding of an experiment. The integration of the required [[Chemical synthesis|synthesis]], purification and [[Analytical chemistry|analytical]] capabilities is impractical when operating outside of a microfluidic context.
 
====NMR====
 
Researchers at the Radboud University Nijmegen and Twente University, the Netherlands, have developed a microfluidic high-resolution NMR flow probe. They have shown a model reaction being followed in real-time. The combination of the uncompromised (sub-Hz) resolution and a low sample volume can prove to be a valuable tool for flow chemistry.<ref>''A Microfluidic High-Resolution NMR Flow Probe'' Jacob Bart†, Ard J. Kolkman, Anna Jo Oosthoek-de Vries, Kaspar Koch, Pieter J. Nieuwland, Hans (J. W. G.) Janssen, Jan (P. J. M.) van Bentum, Kirsten A. M. Ampt, Floris P. J. T. Rutjes, Sybren S. Wijmenga, Han (J. G. E.) Gardeniers and Arno P. M. Kentgens[[J. Am. Chem. Soc.]]; '''2009'''; 131(14) pp 5014 - 5015; {{DOI|10.1021/ja900389x}}</ref>
 
====Infrared spectroscopy====
 
Mettler Toledo and [[Bruker Optics]] offer dedicated equipment for monitoring, with [[attenuated total reflectance]] spectrometry (ATR spectrometry) in microreaction setups. The former has been demonstrated for reaction monitoring.<ref>{{citar periódico|último =Carter|primeiro =Catherine F.|autor2 =Lange, Heiko |autor3 =Ley, Steven V. |autor4 =Baxendale, Ian R. |autor5 =Wittkamp, Brian |autor6 =Goode, Jon G. |autor7 = Gaunt, Nigel L. |título=ReactIR Flow Cell: A New Analytical Tool for Continuous Flow Chemical Processing|periódico=Organic Process Research & Development|data=19 de março de 2010|volume=14|número=2|páginas=393–404|doi=10.1021/op900305v}}</ref> The latter has been successfully used for reaction monitoring<ref>{{citar periódico|último =Minnich|primeiro =Clemens B.|autor2 =Küpper, Lukas |autor3 =Liauw, Marcel A. |autor4 = Greiner, Lasse |título=Combining reaction calorimetry and ATR-IR spectroscopy for the operando monitoring of ionic liquids synthesis|periódico=Catalysis Today|ano=2007|volume=126|número=1-2|páginas=191–195|doi=10.1016/j.cattod.2006.12.007}}</ref> and determining dispersion characteristics<ref>{{citar periódico|último =Minnich|primeiro =Clemens B.|autor2 =Sipeer, Frank |autor3 =Greiner, Lasse |autor4 = Liauw, Marcel A. |título=Determination of the Dispersion Characteristics of Miniaturized Coiled Reactors with Fiber-Optic Fourier Transform Mid-infrared Spectroscopy|periódico=Industrial & Engineering Chemistry Research|data=16 de junho de 2010|volume=49|número=12|páginas=5530–5535|doi=10.1021/ie901094q}}</ref> of a microreactor.
 
==Pesquisa acadêmica==
Microreactors, and more generally, [[micro process engineering]], are the subject of worldwide academic research. A prominent recurring conference is [[IMRET]], the ''International Conference on Microreaction Technology''. Microreactors and micro process engineering have also been featured in dedicated sessions of other conferences, such as the Annual Meeting of the [[American Institute of Chemical Engineers]] ([[AIChE]]), or the [[International Symposia on Chemical Reaction Engineering]] ([[ISCRE]]). Research is now also conducted at various academic institutions around the world, e.g. at the [[Massachusetts Institute of Technology]] (MIT) in Cambridge/MA, [[University of Illinois Urbana-Champaign]], [[Oregon State University]] in Corvallis/OR, at [[University of California, Berkeley]] in Berkeley/CA in the United States, at the [[EPFL]] in Lausanne, Switzerland, at [[Eindhoven University of Technology]] in Eindhoven, at [[Radboud University Nijmegen]] in Nijmegen, Netherlands and at the LIPHT [http://www-lipht.u-strasbg.fr/Interface/index.php] of Université de Strasbourg in Strasbourg and [http://www.lgpc.fr/Objets|LGPC] of the University of Lyon, [[École supérieure de chimie physique électronique de Lyon|CPE Lyon]], France.
 
==Estrutura de mercado==
 
Depending on the application focus, there are various hardware suppliers and commercial development entities to service the evolving market. One view to technically segment market, offering and market clearing stems from the scientific and technological objective of market agents:
 
<ol type=a><li>Ready to Run (turnkey) systems are being used where the application environment stands to benefit from new chemical synthesis schemes, enhanced investigational throughput of up to approximately 10 - 100 experiments per day (depends on reaction time) and reaction subsystem, and actual synthesis conduct at scales ranging from 10 [[milligram]]s per experiment to triple digit tons per year (continuous operation of a reactor battery).</li>
<li>Modular (open) systems are serving the niche for investigations on continuous process engineering lay-outs, where a measurable process advantage over the use of standardized equipment is anticipated by chemical engineers. Multiple process lay-outs can be rapidly assembled and chemical process results obtained on a scale ranging from several grams per experiment up to approximately 100&nbsp;kg at a moderate number of experiments per day (3-15). A secondary transfer of engineering findings in the context of a plant engineering exercise (scale-out) then provides target capacity of typically single product dedicated plants. This mimics the success of engineering contractors for the petro-chemical process industry.</li>
<li>Dedicated developments. Manufacturer of microstructured components are mostly commercial development partners to scientists in search of novel synthesis technologies. Such development partners typically excel in the set-up of comprehensive investigation and supply schemes, to model a desired contacting pattern or spatial arrangement of matter. To do so they predominantly offer information from proprietary integrated modeling systems that combine computational fluid dynamics with thermokinetic modelling. Moreover, as a rule, such development partners establish the overall application analytics to the point where the critical initial hypothesis can be validated and further confined.</li></ol>
 
[[Imagem:FlowStart CloseUp.jpg|thumb|Exemplo de um sistema reator de fluxo.]]
 
==Referências==
<small>{{Reflist}}</small>
 
{{Authority control}}
[[Categoria:Reatores químicos]]
[[Categoria:Microtecnologia]]
[[Categoria:Microfluídica]]
Obtida de "https://pt.wikipedia.org/wiki/Microrreator"