Este trabalho foi apoiado pelos Pilhas de Combustível e europeus empresa comum Hydruogen sob BOR4STORE colaborativa de projetos (Acordo de Subvenção No. 303428) e um programa de infra-estrutura H2FC (Acordo de Subvenção No. FP7-284522).

1. Aparelho <ol><li> Usar uma secagem super-critica (SCD) aparelho de base constituído por quatro componentes primários ligados por tubagem de gás de alta pressão: o fornecimento de gás, um sistema de vácuo, sensores (temperatura e pressão), e o ambiente de amostra (que pode ser submerso num banho). Certifique-se de que a construção é de válvulas de alta qualidade de aço inoxidável, conexões e tubos, pressão nominal de pelo menos 10 MPa na faixa de temperatura entre 80-300 K. Nota: Um esquema é mostrado na Figura 1. </li><li> Para nitrogênio ScD (nscd) tratamentos, garantir que o fornecimento de gás é a pureza de pesquisa (&gt; 99,999%) de azoto gasoso equipado com um regulador de pressão para controle de pressão de saída entre 0-10 MPa. Anexar uma garrafa de 50 L (20 MPa) para o aparelho, e purgar o sistema com nitrogênio puro várias vezes antes do uso. </li><li> Certifique-se de que o sistema de vácuo é capaz de atingir pressões de vácuo até &lt;0,1 Pa e está ligada ao aparelho com umválvula de agulha-controle fino. De preferência, use uma bomba de desbaste oil-free e uma bomba turbo molecular-arrasto, colocado em série. </li><li> Use pelo menos dois sensores de pressão para medição precisa da pressão durante os tratamentos SCD: um sensor de baixa pressão para a medição de vácuo e um sensor de alta pressão para alcançar um intervalo de pressão mensurável total entre 0,1-10 7 Pa. </li><li> Use pelo menos dois sensores de temperatura para a precisão mínimo necessário para realizar tratamentos típicos SCD: um sensor em contacto térmico com a amostra e um sensor dentro do colector de doseamento de gás primário para medições precisas entre 77-300 K (por exemplo, termopares tipo K) . </li><li> Verificar que o suporte de amostra tem um volume interno apropriado para conter a quantidade de amostra necessária para o tratamento, e é construída de aço inoxidável. Nota: A SIDA cilíndricos alongados em contacto térmico com o banho. </li><li> Certifique-se de que a montagem que fecha o recipiente da amostra é aproprIATE para altas pressões e uso repetido (por exemplo, Swagelok VCR). Ligue o volume do recipiente da amostra para uma válvula de isolamento a partir do ambiente exterior através de um comprimento adequado do tubo (o tubo de mergulho) para a completa imersão do suporte de amostras para o banho. </li></ol><img alt="Figura 1" src="/files/ftp_upload/52817/52817fig1.jpg" /> . Figura 1. supercrítico Azoto Secagem (NSCD) Aparelho Uma representação esquemática do aparelho NSCD simplificado para uso em laboratório típico: (A) à temperatura ambiente e (B), após imersão da amostra no banho. O fornecimento de gás para o processo descrito neste trabalho é azoto, mas em geral este aparelho é generalizáveis ​​a outros fluidos SCD com um ponto crítico encontra-se dentro de uma gama prática de temperatura e pressão, tal como CO 2. Os componentes estão marcados para a coerência com the protocolo aqui descrito. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig1highres.jpg" target="_blank">Por favor clique aqui para ver uma versão maior desta figura.</a> 2. Preparação <ol><li> Carga 0,2-0,5 g de amostra (γ-Mg (BH4) 2, na forma de pó, seguindo-síntese química húmida e métodos de secagem padrão) no suporte da amostra sob condições adequadas, normalmente, numa atmosfera inerte, tal como uma caixa de luvas de árgon, à temperatura ambiente ou abaixo. Feche o suporte da amostra (F2 montagem) com uma junta de filtro e, em seguida, fechar a válvula (V4 válvula). Transferir o porta-amostra para o aparelho e anexar (F1 encaixe). </li><li> Abra o colector de dosagem para aspirar via V2 e evacuar. Abrir V3 e evacuar. Purgar o aparelho com nitrogênio via V1 e V2 evacuar via. Abrir V4 e evacuar a amostra à temperatura ambiente durante até 24 horas, para atingir a pressão mínima do sistema (&lt;0,1 Pa). </li><li> Instale o banho de amostra (ver <strong&gt; Figura 2) em torno do suporte da amostra. Execute este levantando o banho em posição em um elevador de tesoura, ou mecanismo similar. </li><li> Definir o aquecedor para o futuro desejada temperatura do líquido (t l, ver passo 3.1) de 110 K, e continuar a evacuar o aparelho até que a temperatura se equilibra. </li></ol><img alt="Figura 2" src="/files/ftp_upload/52817/52817fig2.jpg" /> Figura 2. forno de banho criogénico da amostra. Uma ilustração esquemática (esquerda) e fotografia (direita) de um banho de ambiente térmico criostato apropriado para conter o suporte de amostras durante o processamento NSCD, permitindo a medição e controlo da temperatura da amostra entre 77-298 K. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig2highres.jpg" target="_blank">Por favor clique aqui para ver uma versão maior desta figura.</a> 3. Supercritical Nitrogênio Exposição <ol&gt; <li> Para NSCD processamento de γ-Mg (BH4) 2, (o objecto de demonstração neste protocolo) seleccionar uma temperatura do líquido (t l) de 110 K. Isto corresponde a uma densidade de solvente líquido moderada (~ 0,6 g ml -1) ; Ajuste conforme necessário para a aplicação do presente protocolo a outros processos de tratamento NSCD (ver nota abaixo). </li><li> Feche o sistema de vácuo, fechando V2. Borboleta aberta V1 lentamente, permitindo que a pressão aumente dentro da região de líquido da diagrama de fases. Equilibrar o sistema a 2 MPa e T l. </li><li> Mergulhe a amostra em N2 líquido durante 4 h. </li><li> Definir o aquecedor a 150 K com um min -1 rampa ≤2 K. Permitir que a pressão aumente não seja superior à pressão máxima do aparelho (esta P max deve ser ≥10 MPa); se necessário, ventilar cuidadosamente o excesso de pressão a vácuo através de V2. Equilibrar o sistema em P max e 150 K. </li><li> Mergulhe a amostra em supercritical N2 durante 1 h. </li></ol><img alt="Figura 3" src="/files/ftp_upload/52817/52817fig3.jpg" /> Figura 3. Diagrama de Fase de nitrogênio. Um diagrama de fases detalhada de azoto, em que a densidade do fluido (mostrado na escala de cinzentos linear) é calculada usando REFPROP (a equação Webb-Benedict-Rubin de estado modificado). 41 Várias linhas de densidade constante são mostrados no roxo. Os limites de fase sólida e linhas de transição de ebulição são mostrados em vermelho. As linhas azuis indicam o limite da região do diagrama de fases que é relevante para a secagem ou processamento de extração utilizando N 2. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig3highres.jpg" target="_blank">Por favor clique aqui para ver uma versão maior desta figura.</a> Nota: Para a aplicação do presente protocolo a outros materiais, estabelecer um schem tratamento adequado NSCDe escolhendo as condições necessárias para a solvatação eficaz da espécie-alvo. Consulte o diagrama de fase de N 2, mostrada na Figura 3. Para alcançar uma alta densidade do fluido na fase líquida (por exemplo, 0,8-1 g ml -1), seleccionar um t l de 80-90 K. Para densidade líquida moderada (por exemplo, 0,6-0,8 g ml -1), seleccionar um t l de 90-115 K. Uma abordagem de tentativa e erro poderá ser necessário. 4. Supercritical nitrogênio lançamento <ol><li> Rachar cuidadosamente o sistema de vácuo por estrangulamento V2, permitindo que a pressão para diminuir o mais lentamente possível. Repetidamente quebrar o sistema de vácuo para taxas mais elevadas, conforme necessário para alcançar um declínio gradual para alto vácuo (&lt;0,1 Pa) no intervalo de tempo de aproximadamente 12-24 horas. </li><li> Remover o banho de amostra e totalmente V2 aberta para evacuar completamente a amostra. Equilibre à TA e alto vácuo (&lt;0,1 Pa). </li><li> Desgaseificar a amostra à temperatura ambiente e &lt;0,1 Pa para 1-24 horas, como desired. </li></ol> 5. Publicar Tratamento <ol><li> Feche as válvulas V3 e V4, e remover o suporte de amostras do aparelho (ajuste F1). </li><li> Transferir o porta-amostra para um ambiente inerte para manuseamento, tal como uma caixa de luvas cheia de árgon. Retirar a amostra do suporte de amostras (montagem F2) e armazenar em um recipiente fechado à temperatura ambiente ou abaixo. </li></ol>

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G., Baricco, M., Bordiga, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+carbon+dioxide+recycling+by+reaction+with+&#947;-Mg(BH4)2.">Fast carbon dioxide recycling by reaction with &#947;-Mg(BH4)2.</a> Phys. Chem. Chem. Phys. 16, 22482-22486 (2014).</li><li>Paskevicius, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-Situ+X-ray+Diffraction+Study+of+&#947;-Mg(BH4)2+Decomposition.">In-Situ X-ray Diffraction Study of &#947;-Mg(BH4)2 Decomposition.</a> J. Phys. Chem. C. 116, 15321-15240 (2012).</li><li>Lemmon, E. W., Huber, M. L., McLinden, M. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NIST+standard+reference+database+23:+reference+fluid+thermodynamic+and+transport+properties.">NIST standard reference database 23: reference fluid thermodynamic and transport properties.</a> Standard Reference Data Program. , (2008).</li><li>Moquin, P. H. L., Temelli, F. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Kinetic+modeling+of+hydrolysis+of+canola+oil+in+supercritical+media.">Kinetic modeling of hydrolysis of canola oil in supercritical media.</a> J. Supercrit. Fluid. 45, 94-101 (2008).</li><li>Myers, M. N., Giddings, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultra-High-Pressure+Gas+Chromatography+in+Micro+Columns+to+2000+Atmospheres.">Ultra-High-Pressure Gas Chromatography in Micro Columns to 2000 Atmospheres.</a> Sep. Sci. 1 (6), 761-776 (1966).</li><li>McLeary, E. E., Jansen, J. C., Kapteijn, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Zeolite+based+films,+membranes+and+membrane+reactors:+Progress+and+prospects.">Zeolite based films, membranes and membrane reactors: Progress and prospects.</a> Microporous Mesoporous Mater. 90, 198-220 (2006).</li><li>Richter, B., Ravnsb&#230;k, D. B., Tumanov, N., Filinchuk, Y., Jensen, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Manganese+borohydride;+synthesis+and+characterization.">Manganese borohydride; synthesis and characterization.</a> Dalton Trans. , (2015).</li><li>Liang, S., Tilotta, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+petroleum+hydrocarbons+from+soil+using+supercritical+argon.">Extraction of petroleum hydrocarbons from soil using supercritical argon.</a> Anal. Chem. 70 (3), 616-622 (1998).</li></ol>

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Talvez devido à sua relativamente baixa temperatura crítica (126 K), N 2 historicamente tem sido negligenciado como um solvente ScD eficaz. Em relatórios anteriores, 3,17,42,43 só foi aludido no contexto de processamento temperaturas iguais ou acima da temperatura ambiente, onde ele exibe apenas o poder de solvatação modesta devido à sua baixa densidade do fluido na região de seu diagrama de fases (excepto a altíssimas pressões 43). O passo chave na realização a utilidade pr?...

Extracção com fluido supercrítico (SFE) e secagem (SCD) métodos estão bem estabelecidos em uma ampla gama de aplicações práticas, especialmente nas indústrias alimentares e de petróleo, mas também 1-6 A utilização de secagem por síntese química, análise e processamento de materiais. ou meios de extracção em condições acima seus pontos críticos é muitas vezes mais rápido, mais limpo e mais eficiente do que (líquidos) as técnicas tradicionais, e tem a vantagem adicional de ser altamente ajustável com respeito ao poder de solvatação do fluido por ligeiro ajustamento das condições de operação . Um método 3,7 ScD simples consiste em três etapas básicas. O primeiro passo é a exposição do material sólido (ou talvez líquido) de partida que contém o composto alvo impureza a um fluido ScD apropriadamente escolhido no seu estado líquido (ou quase líquido supercrítico) de fase, onde a sua elevada densidade corresponde a uma alta (e talvez selectiva 7) poder solvente em relação à espécie alvo. Tele segundo passo é o aquecimento e a compressão do sistema acima do ponto crítico do fluido ScD escolhido num recipiente fechado, de modo que o fluido e as suas espécies alvo dissolvidos não transmitir um limite de fase, que pode resultar na separação. O passo final é a redução lentamente a pressão do fluido ScD a vácuo a uma temperatura acima da temperatura crítica, permitindo que a solução de fluido contendo as espécies alvo escapar, novamente sem a ocorrência de um limite de fase ou quaisquer efeitos prejudiciais de tensão superficial ao longo do caminho. O material de partida é deixado empobrecido da espécie alvo e pode ser sujeito a tratamentos iterados se necessário. Em casos de extracção de fluido supercrítico, as espécies do soluto alvo é o produto desejado, e é recolhida a partir de solução para utilização posterior 8,9. Em outros casos, o material de partida seco ou purificada é o produto desejado, e as impurezas extraídas são descartados. Este último caso, aqui referidoscomo a abordagem ScD, foi descoberto para ser uma estratégia eficaz para o pré-tratamento de elevada área superficial, materiais microporosos, tais como estruturas metal-orgânicas (MOFs), onde os métodos tradicionais de tratamento térmico sob vácuo são, em muitos casos não é suficiente na limpeza dos poros de todos os hóspedes indesejados, ou resultar em colapso de poros. dióxido de carbono 10 ScD (CSCD) processamento é agora um processo de pós-sintética de rotina para MOFs, 11 levando a aumentos em áreas de superfície em nitrogênio acessível sobre os materiais não tratados de até 1.000% e 12 outras melhorias, tais como na actividade catalítica. 13 Outras aplicações de fluidos supercríticos são notáveis ​​como um meio largamente sintonizável para reacções químicas, 14-16 cromatografia supercrítica de fluidos (SCFC) 6,17,18 e síntese dos aerogéis e materiais compósitos avançados. 19- 22 Para aplicações de secagem, um fluido ScD é escolhido com base em dois critérios: a) a proximidade da suaponto crítico em condições ambiente (por conveniência e para reduzir os custos de energia ou a complexidade do processo) e b) o seu poder de solvatação em relação à espécie alvo. O dióxido de carbono (CO 2) provou ser um fluido ScD conveniente em muitas aplicações, uma vez que não é tóxico, não inflamável, e mais barato, e pode ser ajustado para exibir um elevado poder de solvatação para um número de espécies orgânicas alvo comum na sua quase-líquida Estado (a pressões &lt;10 MPa e temperaturas de 273-323 K). 1-3,7-9 outros solventes supercríticos comuns (ou co-solventes) incluem água (abrangendo uma gama notável de propriedades de solventes entre seu ambiente e estado supercrítico 23), acetona, etileno, metanol, etanol, e o etano, cobrindo o espectro de polar (prótico e aprótico) para não polar, e tendo pontos críticos relativamente próximo às condições ambientais. O dióxido de carbono é, de longe, o fluido ScD mais comum utilizado. Em métodos cscd estabelecidos, a reactividadedo material de partida não é um factor inibidor desde CO 2 só é muito fracamente reactivo a temperaturas próximas do seu ponto crítico. No entanto, certas classes de materiais, tais como os chamados hidretos complexos (por exemplo, boro-hidretos e alanates) apresentam grandes desafios no manuseamento devido à sua forte reactividade na presença de água ou de CO 2 para além da sua (talvez intencionalmente concebidos) instabilidade sob aquecimento 24-26. Além disso, há um grande interesse internacional em materiais tais como compostos de armazenamento de hidrogénio de alta densidade, 27-30 e, portanto, também em nanoestruturada e / ou variedades porosas 31-33. Para a purificação eficaz de tais, instável e materiais nanoestruturados reactivos, os métodos são SCD uma estratégia promissora. Um fluido de 34 ScD deve ser utilizado, que tem um diâmetro molecular pequeno apropriado para a penetração nas cavidades estreitas e que também tem um elevado poder de solvatação para o impurezas alvo, while restante não reactiva para com o próprio material de partida. Aqui, a utilização de azoto supercrítico (N2) como um fluido efectivo para tal extracção e especialmente secagem de aplicações é apresentada. Uma metodologia específica supercrítico secagem azoto (NSCD) é descrito abaixo para a purificação de boro-hidreto de magnésio de fase γ onde a espécie alvo incluem tanto diborano e um composto de n-butilo (similar a, mas não especificamente identificadas como n-butano). O protocolo a seguir podem ser facilmente modificados para a extensão global para outros processos de secagem de azoto ou de extração supercrítica.

<table><tbody><tr><td>Compressed Nitrogen Gas</td><td>Messer Schweiz AG</td><td></td><td>50 L bottle, purity &gt; 99.999%, &amp;lt;3 ppmv H&lt;sub&gt;2&lt;/sub&gt;O</td></tr><tr><td>Liquid Nitrogen</td><td>Pan Gas AG</td><td></td><td>Bulk storage, on site</td></tr><tr><td>Custom Supercritical Drying Apparatus</td><td>Empa</td><td></td><td>Swagelok (compression fitting and VCR) components</td></tr><tr><td>Custom Cryogenic Furnace Bath</td><td>Empa</td><td></td><td></td></tr><tr><td>Custom Labview Interface</td><td>Empa</td><td></td><td></td></tr></tbody></table>

supercritical nitrogen processing for the purification of reactive porous materials

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. Herein, nitrogen is presented as a novel supercritical drying fluid for specialized applications such as in the processing of reactive porous materials, where carbon dioxide and other fluids are not appropriate due to their higher chemical reactivity. Nitrogen exhibits similar physical properties in the near-critical region of its phase diagram as compared to carbon dioxide: a widely tunable density up to ~1 g ml-1, modest critical pressure (3.4 MPa), and small molecular diameter of ~3.6 &#197;. The key to achieving a high solvation power of nitrogen is to apply a processing temperature in the range of 80-150 K, where the density of nitrogen is an order of magnitude higher than at similar pressures near ambient temperature. The detailed solvation properties of nitrogen, and especially its selectivity, across a wide range of common target species of extraction still require further investigation. Herein we describe a protocol for the supercritical nitrogen processing of porous magnesium borohydride.

Boro-hidretos de metais alcalinos e alcalino-terrosos são materiais de armazenamento de hidrogénio potenciais, que proporcionam um elevado teor de hidrogénio gasoso após a decomposição. 27,29 Outros produtos de decomposição, tais como diborano, por vezes, têm também sido detectados no gás dessorvido, mas a sua origem não é, a priori, claro ; é possível que são produtos da decomposição da fase pura, mas também podem ser impurezas ou produtos de reacções de impurezas que tenham ficado de s?...

Watch this Scientific Journal Video about Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials at JoVE.com

Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

O azoto é um fluido supercrítico eficazes para os processos de extracção ou de secagem, devido ao seu pequeno tamanho molecular e de alta densidade em regime quase-líquido supercrítico, e inércia química. Nós apresentamos um protocolo de secagem azoto supercrítico para o tratamento de purificação, os materiais porosos reactivos.

Processamento de nitrogênio supercrítico para a purificação de Reativos Porous Materials

Supercritical fluid extraction and drying methods are well established in numerous applications for the synthesis and processing of porous materials. ...

supercritical-nitrogen-processing-for-purification-reactive-porous

Research

JoVE Journal

Chemistry

14.7K visualizações.  Empa, Swiss Federal Laboratories for Materials Science and Technology.  O azoto é um fluido supercrítico eficazes para os processos de extracção ou de secagem, devido ao seu pequeno tamanho molecular e de alta densidade em regime quase-líquido supercrítico, e inércia química. Nós apresentamos um protocolo de secagem azoto supercrítico para o tratamento de purificação, os materiais porosos reactivos. 

Vídeo: Supercritical Nitrogen Processing for the Purification of Reactive Porous Materials

Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

Nitrogen-doped carbon nanotubes consist of many cup-shaped graphitic compartments termed as nitrogen-doped carbon nanotube cups (NCNCs). These as-synthesized graphitic nanocups from chemical vapor deposition (CVD) method were stacked in a head-to-tail fashion held only through noncovalent interactions. Individual NCNCs can be isolated out of their stacking structure through a series of chemical and physical separation processes. First, as-synthesized NCNCs were oxidized in a mixture of strong acids to introduce oxygen-containing defects on the graphitic walls. The oxidized NCNCs were then processed using high-intensity probe-tip sonication which effectively separated the stacked NCNCs into individual graphitic nanocups. Owing to their abundant oxygen and nitrogen surface functionalities, the resulted individual NCNCs are highly hydrophilic and can be effectively functionalized with gold nanoparticles (GNPs), which preferentially fit in the opening of the cups as cork stoppers. These graphitic nanocups corked with GNPs may find promising applications as nanoscale containers and drug carriers.

We discussed the synthesis of individual graphitic nanocups using a series of techniques including chemical vapor deposition, acid oxidation and probe-tip sonication. By citrate reduction of HAuCl4, the graphitic nanocups were effectively corked with gold nanoparticles due to the chemically reactive edges of the cups.

Síntese e funcionalização de nitrogênio dopado Copas de Nanotubos de Carbono com nanopartículas de ouro como Rolhas

Nitrogen-doped carbon  nanotubes consist of many cup-shaped graphitic compartments termed as  nitrogen-doped carbon nanotube cups (NCNCs).  These ...

Engenharia

Preparing Silica Aerogel Monoliths via a Rapid Supercritical Extraction Method

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The procedure requires 15-20 min of preparation time, during which a liquid precursor mixture is prepared and poured into wells of a metal mold that is placed between the platens of a hydraulic hot press, followed by several hours of processing within the hot press. The precursor solution consists of a 1.0:12.0:3.6:3.5 x 10-3 molar ratio of tetramethylorthosilicate (TMOS):methanol:water:ammonia. In each well of the mold, a porous silica sol-gel matrix forms. As the temperature of the mold and its contents is increased, the pressure within the mold rises. After the temperature/pressure conditions surpass the supercritical point for the solvent within the pores of the matrix (in this case, a methanol/water mixture), the supercritical fluid is released, and monolithic aerogel remains within the wells of the mold. With the mold used in this procedure, cylindrical monoliths of 2.2 cm diameter and 1.9 cm height are produced. Aerogels formed by this rapid method have comparable properties (low bulk and skeletal density, high surface area, mesoporous morphology) to those prepared by other methods that involve either additional reaction steps or solvent extractions (lengthier processes that generate more chemical waste).The rapid supercritical extraction method can also be applied to the fabrication of aerogels based on other precursor recipes.

This article describes a rapid supercritical extraction method for fabricating silica aerogels. By utilizing a confined mold and hydraulic hot press, monolithic aerogels can be made in eight hours or less.

Preparação de sílica aerogel Monólitos através de um Método de extracção rápida supercrítico

A procedure for the fabrication of monolithic silica aerogels in eight hours or less via a rapid supercritical extraction process is described. The ...

Química

Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.
The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

Preparação de altamente poroso Coordenação Polymer Revestimentos em macroporosas Polymer Monólitos para o enriquecimento avançado de Fosfopeptídeos

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous ...

Procedures of Laboratory Fumigation for Pest Control with Nitric Oxide Gas

Nitric oxide (NO) is a newly discovered fumigant for postharvest pest control. This paper provides detailed protocols for conducting NO fumigation on fresh products and procedures for residue analysis and product quality evaluation. An airtight fumigation chamber containing fresh fruit and vegetables is first flushed with nitrogen (N2) to establish an ultralow oxygen (ULO) environment followed by injection of NO. The fumigation chamber is then kept at a low temperature of 2 - 5 &#176;C for a specified time period necessary to kill a target pest to complete a fumigation treatment. At the end of a fumigation treatment, the fumigation chamber is flushed with N2 to dilute NO prior to opening the chamber to ambient air to prevent the reaction between NO and O2, which produces NO2 and may damage delicate fresh products. At different times after NO fumigation, NO2 in headspace and nitrate and nitrite in liquid samples were measured as residues. Product quality was evaluated after 2 weeks of post-treatment cold storage to determine effects of NO fumigation on product quality. Keeping&#160;O2 from reacting with NO is critical to NO fumigation and is an important part of the protocols. Measuring NO levels is challenging and a practical solution is provided. Possible protocol modifications are also suggested for measuring NO levels in the fumigation chambers as well as residues. NO fumigation has the potential to be a practical alternative to methyl bromide fumigation for postharvest pest control on fresh and stored products. This publication is intended to assist other researchers in conducting NO fumigation research for postharvest pest control and accelerating the development of NO fumigation for practical applications.

This paper describes nitric oxide (NO) fumigation protocols for postharvest pest control. Fumigation chambers are flushed with nitrogen (N2) to establish ultralow oxygen conditions before NO is injected. At the end, chambers are flushed with N2 to dilute NO before exposing products to ambient air to prevent exposure to NO2.

Procedimentos de laboratório de fumigação para controle de pragas com gás de óxido nítrico

Nitric oxide (NO) is a newly discovered fumigant for postharvest pest control. This paper provides detailed protocols for conducting NO fumigation on ...

Ambiente

On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes

The shift to heavy crude oils and the use of alternative fossil resources such as shale oil are a challenge for the petrochemical industry. The composition of heavy crude oils and shale oils varies substantially depending on the origin of the mixture. In particular they contain an increased amount of nitrogen containing compounds compared to the conventionally used sweet crude oils. As nitrogen compounds have an influence on the operation of thermal processes occurring in coker units and steam crackers, and as some species are considered as environmentally hazardous, a detailed analysis of the reactions involving nitrogen containing compounds under pyrolysis conditions provides valuable information. Therefore a novel method has been developed and validated with a feedstock containing a high nitrogen content, i.e., a shale oil. First, the feed was characterized offline by comprehensive two-dimensional gas chromatography (GC &#215; GC) coupled with a nitrogen chemiluminescence detector (NCD). In a second step the on-line analysis method was developed and tested on a steam cracking pilot plant by feeding pyridine dissolved in heptane. The former being a representative compound for one of the most abundant classes of compounds present in shale oil. The composition of the reactor effluent was determined via an in-house developed automated sampling system followed by immediate injection of the sample on a GC &#215; GC coupled with a time-of-flight mass spectrometer (TOF-MS), flame ionization detector (FID) and NCD. A novel method for quantitative analysis of nitrogen containing compounds using NCD and 2-chloropyridine as an internal standard has been developed and demonstrated.

A method combining comprehensive two-dimensional gas chromatography with nitrogen chemiluminescence detection has been developed and applied to on-line analysis of nitrogen containing compounds in a complex hydrocarbon matrix.

Análise on-line de compostos contendo azoto em matrizes de hidrocarbonetos complexos

The shift to heavy crude oils and the use of alternative fossil resources such as shale oil are a challenge for the petrochemical industry. The ...

Preparation of Biomass-based Mesoporous Carbon with Higher Nitrogen-/Oxygen-chelating Adsorption for Cu(II) Through Microwave Pre-Pyrolysis

An environment-friendly technique for synthesizing biomass-based mesoporous activated carbon with high nitrogen-/oxygen-chelating adsorption for Cu(II) is proposed. Bagasse impregnated with phosphoric acid is utilized as the precursor. To pyrolyze the precursor, two separate heating modes are used: microwave pyrolysis and conventional electric-heating pyrolysis. The resulting bagasse-derived carbon samples are modified with nitrification and reduction modification. Nitrogen (N)/oxygen (O) functional groups are simultaneously introduced to the surface of activated carbon, enhancing its adsorption of Cu(II) by complexing and ion-exchange. Characterization and copper adsorption experiments are performed to investigate the physicochemical properties of four prepared carbon samples and determine which heating method favors the subsequent modification for doping of N/O functional groups. In this technique, based on analyzing data of nitrogen adsorption, Fourier transform infrared spectroscopy, and batch adsorption experiments, it is proven that microwave-pyrolyzed carbon has more defect sites and, therefore, time-saving effective microwave pyrolysis contributes more N/O species to the carbon, although it leads to a lower specific surface area. This technique offers a promising route to synthesis adsorbents with higher nitrogen and oxygen content and a higher adsorption capacity of heavy-metal ions in wastewater remediation applications.

Preparation of Biomass-based Mesoporous Carbon with Higher Nitrogen-/Oxygen-chelating Adsorption for CuII Through Microwave Pre-Pyrolysis

Here, we present a protocol to synthesize nitrogen/oxygen dual-doped mesoporous carbon from biomass by chemical activation in different pyrolysis modes followed by modification. We demonstrate that the microwave pyrolysis benefits the subsequent modification process to simultaneously introduce more nitrogen and oxygen functional groups on the carbon.

Preparação da biomassa de carbono de mesoporos com nitrogênio superior-/ oxigênio-quelantes de adsorção para Cu(II) através de pre-pirólise microondas

An environment-friendly technique for synthesizing biomass-based mesoporous activated carbon with high nitrogen-/oxygen-chelating adsorption for Cu(II) is ...

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

The importance of understanding the fate of nitrate (NO3&#8722;), which is the dominant N species transferred from terrestrial to aquatic ecosystems, has been increasing because global nitrogen loads have dramatically increased following industrialization. Dissimilatory nitrate reduction to ammonium (DNRA) and denitrification are both microbial processes that use NO3&#8722; for respiration. Compared to denitrification, quantitative determinations of the DNRA activity have been carried out only to a limited extent. This has led to an insufficient understanding of the importance of DNRA in NO3&#8722; transformations and the regulating factors of this process. The objective of this paper is to provide a detailed procedure for the measurement of the potential DNRA rate in environmental samples. In brief, the potential DNRA rate can be calculated from the 15N-labeled ammonium (15NH4+) accumulation rate in 15NO3&#8722; added incubation. The determination of the 14NH4+ and 15NH4+ concentrations described in this paper is comprised of the following steps. First, the NH4+ in the sample is extracted and trapped on an acidified glass filter as ammonium salt. Second, the trapped ammonium is eluted and oxidized to NO3&#8722; via persulfate oxidation. Third, the NO3&#8722; is converted to N2O via an N2O reductase deficient denitrifier. Finally, the converted N2O is analyzed using a previously developed quadrupole gas chromatography&#8211;mass spectrometry system. We applied this method to salt marsh sediments and calculated their potential DNRA rates, demonstrating that the proposed procedures allow a simple and more rapid determination compared to previously described methods.

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

A series of methods to determine the potential DNRA rate based on 14NH4+/15NH4+ analyses is provided in detail. NH4+ is converted into N2O via several steps and analyzed using quadrupole gas chromatography&#8211;mass spectrometry.

Medição das Taxas Potenciais de Redução de Nitrato Dissimlatório para Amônio Com base em 14NH4+/15NH4+ Análises via Conversão Sequencial para N2O

The importance of understanding the fate of nitrate (NO3&#8722;), which is the dominant N species transferred from terrestrial to aquatic ecosystems, has ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

Propriedades de superfície de carbono de Nanoporous sintetizado e matrizes de sílica

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

Ammonia Synthesis at Low Pressure

Ammonia can be synthesized at low pressure by the use of an ammonia selective absorbent. The process can be driven with wind energy, available locally in areas requiring ammonia for synthetic fertilizer. Such wind energy is often called &#34;stranded,&#34; because it is only available far from population centers where it can be directly used.
In the proposed low pressure process, nitrogen is made from air using pressure swing absorption, and hydrogen is produced by electrolysis of water. While these gases can react at approximately 400 &#176;C in the presence of a promoted conventional catalyst, the conversion is often limited by the reverse reaction, which makes this reaction only feasible at high pressures. This limitation can be removed by absorption on an ammine-like calcium or magnesium chloride. Such alkaline metal halides can effectively remove ammonia, thus suppressing the equilibrium constraints of the reaction. In the proposed absorption-enhanced ammonia synthesis process, the rate of reaction may then be controlled not by the chemical kinetics nor the absorption rates, but by the rate of the recycle of unreacted gases. The results compare favorably with ammonia made from a conventional small scale Haber-Bosch process.

Ammonia can be synthesized at low pressure by using a conventional catalyst and an ammonia selective absorbent.

Síntese de amônia a baixa pressão

Ammonia can be synthesized at low pressure by the use of an ammonia selective absorbent. The process can be driven with wind energy, available locally in ...

Bioengenharia

<meta charset="utf8"></head><body>Sistema Versátil Assistido por Microondas para Síntese de Peptídeos

An Inexpensive Adaptation of a Commercial Microwave Reactor for Solid Phase Peptide Synthesis

A home-built apparatus to perform solid phase peptide synthesis (SPPS), assisted by microwave irradiation and heating, is presented. In contrast to conventional SPPS reaction vessels, which drain solvent and byproducts via a frit located at the bottom of the vessel, the presented apparatus employs a gas dispersion tube under vacuum to remove solvent, byproducts, and excess reagents. The same gas dispersion tube supplies nitrogen gas agitation of the SPPS beads during the reaction steps of coupling and deprotection. Microwave heating is beneficial for SPPS couplings of sterically hindered residues, such as alpha-aminoisobutyric acid (Aib), an alpha,alpha-dialkylated amino acid residue. This home-built apparatus has been used to prepare, via manual Fmoc SPPS methods, heptameric and octameric peptides dominated by the Aib residue, which is notoriously difficult to couple under standard room temperature conditions and reagents. Further, typical commercial microwave SPPS reactors are dedicated exclusively to SPPS synthesis rendering them inaccessible to non-SPPS users. In contrast, the presented apparatus preserves the versatility of the microwave reactor for conventional microwave acceleration of chemical reactions, as the apparatus is trivially removed from the commercial microwave reactor.

<meta charset="utf8"></head><body>Uma adaptação barata de um reator de micro-ondas comercial para síntese de peptídeos em fase sólida

A simple, inexpensive, and novel apparatus for performing solid phase peptide syntheses in a commercial microwave reactor is presented.

Uma adaptação barata de um reator de micro-ondas comercial para síntese de peptídeos em fase sólida

A home-built apparatus to perform solid phase peptide synthesis (SPPS), assisted by microwave irradiation and heating, is presented. In contrast to ...

Processamento de nitrogênio supercrítico para a purificação de Reativos Porous Materials

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