Questo lavoro è stato sostenuto da Celle a combustibile europee e Hydruogen impresa comune sotto BOR4STORE collaborativo progetto (accordo di sovvenzione n ° 303428) e il programma di infrastrutture H2FC (Grant Agreement No. FP7-284522).

1. Apparecchiatura <ol><li> Utilizzare un essiccamento supercritico (SCD) Apparecchiatura di base costituito da quattro componenti principali connesso con un tubo di gas ad alta pressione: la fornitura di gas, un sistema a vuoto, sensori (temperatura e pressione), e l&#39;ambiente campione (che può essere immerso in un bagno). Assicurarsi che la costruzione è di valvole di alta qualità in acciaio inox, raccordi e tubi, pressione votate almeno 10 MPa entro l&#39;intervallo di temperatura tra 80-300 K. Nota: Lo schema è mostrato in Figura 1. </li><li> Per azoto ScD (nscd) trattamenti, in modo che l&#39;alimentazione del gas è la purezza della ricerca (&gt; 99.999%) azoto gassoso dotato di un regolatore di pressione per il controllo della pressione di uscita tra 0-10 MPa. Collegare un contenitore 50 L (20 MPa) all&#39;apparato, e spurgare il sistema con azoto puro più volte prima dell&#39;uso. </li><li> Assicurarsi che il sistema di vuoto è in grado di raggiungere pressioni di vuoto fino a &lt;0,1 Pa ed è collegato all&#39;apparecchio conValvola ago sottile controllo. Preferibilmente usare una pompa di diffusione senza olio e una pompa turbo molecolare resistenza, posti in serie. </li><li> Utilizzare almeno due sensori di pressione per la misurazione della pressione durante i trattamenti SCD: un sensore di bassa pressione per la misurazione di vuoto e sensore di alta pressione per ottenere un intervallo di pressione misurabile totale tra 0,1-10 7 Pa. </li><li> Utilizzare almeno due sensori di temperatura per l&#39;accuratezza minima necessaria per eseguire trattamenti tipici SCD: un sensore a contatto termico con il campione e un sensore all&#39;interno del collettore di dosaggio gas primario per misurazioni accurate tra 77-300 K (ad esempio, tipo K) . </li><li> Verificare che il supporto del campione ha un volume interno appropriato per contenere la quantità di campione necessaria per il trattamento, ed è costruito in acciaio inossidabile. Nota: A allungate aids progettazione cilindrici in contatto termico con la vasca. </li><li> Assicurarsi che il raccordo che chiude il contenitore del campione è approprIATE per alte pressioni e ripetuto uso (ad esempio, Swagelok VCR). Collegare il contenitore volume del campione ad una valvola per l&#39;isolamento dall&#39;ambiente esterno attraverso un tubo di lunghezza appropriata (pescante) per completa immersione del supporto del campione nella vasca. </li></ol><img alt="Figura 1" src="/files/ftp_upload/52817/52817fig1.jpg" /> . Figura 1. supercritica azoto essiccazione (nscd) Apparecchiatura Una rappresentazione schematica dell&#39;apparecchiatura nscd semplificato per l&#39;uso nel tipico laboratorio: (A) a temperatura ambiente e (B) dopo l&#39;immersione del campione nel bagno. L&#39;alimentazione del gas per il processo descritto in questo lavoro è azoto, ma questo apparato generale è generalizzabile ad altri fluidi SCD con un punto critico compresa in una gamma pratica di temperatura e pressione, come il CO 2. I componenti sono etichettati per coerenza con the protocollo qui descritto. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig1highres.jpg" target="_blank">Cliccate qui per vedere una versione più grande di questa figura.</a> 2. Preparazione <ol><li> Carico 0,2-0,5 g di campione (γ-Mg (BH 4) 2, in forma di polvere, dopo la sintesi wet-chimica e metodi di essiccazione normali) nel supporto del campione in condizioni appropriate, tipicamente in atmosfera inerte come un vano portaoggetti argon, a temperatura ambiente o inferiore. Chiudere il portacampioni (raccordo F2) con una guarnizione del filtro e quindi chiudere la valvola (valvola V4). Trasferire il portacampioni all&#39;apparato e fissare (raccordo F1). </li><li> Aprire il collettore di dosaggio per aspirare via V2 ed evacuare. Aprire V3 ed evacuare. Spurgare l&#39;apparecchio con azoto tramite V1 e V2 evacuare via. Aprire V4 e evacuare il campione a temperatura ambiente fino a 24 ore, per raggiungere la pressione minima del sistema (&lt;0,1 Pa). </li><li> Installare il bagno del campione (vedi <strong&gt; Figura 2) intorno al supporto del campione. Eseguire questa alzando la vasca in posizione su una piattaforma a forbice o meccanismo simile. </li><li> Impostare il riscaldatore per il futuro desiderato temperatura del liquido (T l, vedere il punto 3.1) di 110 K, e continuano a portare l &#39;apparecchio fino a quando la temperatura si equilibra. </li></ol><img alt="Figura 2" src="/files/ftp_upload/52817/52817fig2.jpg" /> Figura 2. criogenico forno a bagno del campione. Una rappresentazione schematica (a sinistra) e la fotografia (a destra) di un ambiente criostatiche bagno termale adeguato per contenere il supporto del campione durante l&#39;elaborazione nscd, consentendo la misurazione e il controllo della temperatura del campione tra i 77-298 K. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig2highres.jpg" target="_blank">Per favore clicca qui per vedere una versione più grande di questa figura.</a> 3. supercritico azoto Esposizione <ol&gt; <li> Per NSCD trattamento di γ-Mg (BH 4) 2, (oggetto di dimostrazione in questo protocollo) seleziona una temperatura del liquido (T l) di 110 K. Ciò corrisponde ad una densità di solvente liquido moderata (~ 0,6 g ml -1) ; Regolare come necessario per l&#39;applicazione di questo protocollo per altri procedimenti di trattamento nscd (vedi nota sotto). </li><li> Chiudere l&#39;impianto al vuoto chiudendo V2. Gas aperto V1 lentamente, permettendo la pressione per aumentare nella regione liquido del diagramma di fase. Equilibrare il sistema a 2 MPa e T l. </li><li> Immergere il campione in N liquido 2 per 4 ore. </li><li> Impostare il riscaldatore a 150 K con un min -1 rampa ≤2 K. Lasciare la pressione per aumentare non superiore alla pressione nominale massima dell&#39;apparecchio (questo P max dovrebbe essere ≥10 MPa); se necessario, spurgare accuratamente la pressione in eccesso di aspirare via V2. Equilibrare il sistema a P max e 150 K. </li><li> Immergere il campione in supercritical N 2 per 1 ora. </li></ol><img alt="Figura 3" src="/files/ftp_upload/52817/52817fig3.jpg" /> Figura 3. Fase Schema di Azoto. Un diagramma di fase dettagliata di azoto, dove la densità del fluido (mostrata in scala di grigi lineare) viene calcolato utilizzando Refprop (un&#39;equazione Webb-Benedetto-Rubin modificato di stato). 41 diverse linee di densità costante sono mostrati in viola. I confini di fase solida e linee di transizione di ebollizione sono mostrati in rosso. Le linee blu indicano il confine della regione del diagramma di fase che è rilevante per l&#39;essiccazione o di estrazione lavorazione con N 2. <a href="https://www.jove.com/files/ftp_upload/52817/52817fig3highres.jpg" target="_blank">Clicca qui per vedere una versione più grande di questa figura.</a> Nota: Per l&#39;applicazione di questo protocollo per altri materiali, istituire un adeguato trattamento schem nscde scegliendo le condizioni necessarie per una efficace solvatazione delle specie bersaglio. Fare riferimento al diagramma di fase di N 2, illustrata in figura 3. Per ottenere una elevata densità del fluido in fase liquida (ad esempio, 0.8-1 g ml -1), selezionare una T l di 80-90 K. Per densità del liquido moderata (ad esempio, 0,6-0,8 g ml -1), selezionare una T l di 90-115 K. Una prova e l&#39;approccio di errore può essere necessario. 4. supercritico azoto uscita <ol><li> Rompere attenzione al sistema di vuoto mediante strozzamento V2, permettendo la pressione per diminuire più lentamente possibile. Rompere ripetutamente il sistema di tassi di vuoto più elevati necessari per conseguire un graduale declino per alto vuoto (&lt;0,1 Pa) nell&#39;arco approssimativa di tempo di 12-24 ore. </li><li> Rimuovere il bagno di campione e completamente V2 aperto di evacuare completamente il campione. Equilibrare a RT ed alto vuoto (&lt;0,1 Pa). </li><li> Degassare il campione a temperatura ambiente e &lt;0,1 Pa per 1-24 ore, come desired. </li></ol> 5. Messaggio Trattamento <ol><li> Chiudere le valvole V3 e V4, e rimuovere il supporto del campione l&#39;apparato (raccordo F1). </li><li> Trasferire il portacampione per ambiente inerte per la manipolazione, come un cassetto portaoggetti argon-riempita. Togliere il campione dal supporto (montaggio F2) e riporla in un contenitore sigillato a temperatura ambiente o inferiore. </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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Forse a causa della sua relativamente bassa temperatura critica (126 K), N 2 è stato storicamente trascurato come un efficace solvente ScD. In relazioni precedenti, 3,17,42,43 è stata solo accennato nel contesto di elaborare temperatura uguale o superiore ambiente, dove si esibisce solo il potere solvatazione modesta a causa della sua bassa densità del fluido in questa regione del suo diagramma di fase (ad eccezione a pressioni estremamente elevate 43). Il passaggio chiave nella reali...

Estrazione con fluidi supercritici (SFE) ed essiccamento (SCD) metodi sono ben stabiliti in una vasta gamma di applicazioni pratiche, soprattutto nelle industrie alimentari e del petrolio, ma anche nella sintesi chimica, analisi e trattamento dei materiali. 1-6 L&#39;uso di essiccazione o supporto di estrazione a condizioni sopra loro punti critici è spesso più veloce, pulito, e più efficiente rispetto alle tecniche tradizionali (liquidi), e ha il vantaggio di essere altamente regolabili rispetto alla potenza solvatazione del fluido da leggero aggiustamento delle condizioni operative . 3,7 Un metodo semplice ScD si compone di tre fasi fondamentali. Il primo passo è esporre il materiale solido (o forse liquido) partendo che contiene il composto di destinazione impurezza di un fluido ScD opportunamente scelto nel liquido (o quasi liquido supercritico) di fase, in cui la sua alta densità corrisponde ad un alto (e forse selettiva 7) potere solvente rispetto alle specie bersaglio. Tche secondo passo è il riscaldamento e la compressione del sistema sopra punto critico del ScD fluido prescelto in un contenitore chiuso in modo che il fluido e le sue specie bersaglio disciolte non passano un confine di fase che potrebbe provocare la separazione. Il passo finale si sta riducendo lentamente la pressione del fluido ScD per vuoto ad una temperatura superiore alla temperatura critica, permettendo la soluzione fluido contenente specie bersaglio di fuggire, di nuovo senza incontrare un confine fase o eventuali effetti negativi di tensione superficiale lungo la strada. Il materiale di partenza è lasciato impoverito di specie bersaglio e può essere sottoposto a trattamenti ripetuti, se necessario. In caso di estrazione con fluido supercritico, la specie bersaglio soluto è il prodotto desiderato, e sono raccolti da soluzione per un ulteriore uso. 8,9 In altri casi, il materiale di partenza secche o purificato è il prodotto desiderato, e le impurità estratte vengono scartati. Quest&#39;ultimo scenario, qui indicatacome l&#39;approccio ScD, è stato scoperto di essere una strategia efficace per il pretrattamento di elevata area superficiale, materiali microporosi quali strutture metallo-organici (MOF), dove i metodi tradizionali di trattamento termico sotto vuoto in molti casi non è sufficiente a chiarire i pori di tutti gli ospiti indesiderati, o provocare il collasso dei pori. anidride carbonica 10 ScD (CSCD) il trattamento è ora un processo di post-sintetico di routine per MOF, 11 che porta ad un aumento delle superfici di azoto accessibile rispetto ai materiali non trattati fino a 1.000% e 12 altri miglioramenti, come in attività catalitica. 13 Altre applicazioni fluidi supercritici sono notevoli come mezzo ampiamente accordabile per reazioni chimiche, 14-16 supercritico cromatografia fluido (SCFC) 6,17,18 e sintesi di aerogel e materiali compositi avanzati. 19- 22 Per asciugare le applicazioni, un fluido ScD viene scelta in base a due criteri: a) la vicinanza del suopunto critico alle condizioni ambientali (per comodità e per ridurre i costi energetici e la complessità dei processi) e b) il suo potere solvatazione rispetto alle specie bersaglio. L&#39;anidride carbonica (CO 2) ha dimostrato di essere una comoda fluido ScD in molte applicazioni poiché è non tossico, non infiammabile, e poco costoso, e può essere sintonizzata per esibire un elevato potere di solvatazione verso un numero di comuni specie bersaglio organiche nel suo quasi-liquido stato (a pressioni di &lt;10 MPa e temperature di 273-323 K). 1-3,7-9 Altri solventi supercritici comuni (o co-solventi) si annoverano acqua (che copre una notevole gamma di proprietà solventi tra il suo ambiente e stato supercritico 23), acetone, etilene, metanolo, etanolo, ed etano, coprendo lo spettro da polare (protici e aprotici) per non polare, ed aventi punti critici relativamente vicino alle condizioni ambientali. L&#39;anidride carbonica è di gran lunga il fluido più comune ScD utilizzato. Nei metodi cscd stabiliti, la reattivitàdel materiale di partenza non è un fattore inibitorio dal CO 2 è molto debolmente reattivo a temperature vicine suo punto critico. Tuttavia, alcune classi di materiali come cosiddetti idruri complessi (ad esempio, alanati e boroidruri) presentano sfide uniche nella maneggevolezza grazie alla loro forte reattività in presenza di acqua o CO 2 in aggiunta alla loro (forse volutamente su misura) instabilità sotto riscaldamento . 24-26 Inoltre, vi è un grande interesse internazionale in materiali quali composti stoccaggio di idrogeno ad alta densità, 27-30 e quindi anche in nanostrutturati e / o varietà porosi 31-33. Per l&#39;efficace purificazione di tali reattivi, instabili e materiali nanostrutturati, metodi SCD sono una strategia promettente. Fluido 34 Un ScD deve essere utilizzato che ha un piccolo diametro molecolare appropriato per la penetrazione in cavità strette e che ha anche un elevato potere solvatazione verso la impurità bersaglio, WHIle rimanenti non reattiva verso il materiale di partenza stessa. Qui, l&#39;uso di azoto supercritico (N 2) come fluido efficace per tale estrazione e applicazioni soprattutto essiccazione è presentato. Una metodologia specifica supercritico essiccazione azoto (nscd) è descritta di seguito per la purificazione di γ-fase boroidruro magnesio una specie bersaglio comprendono sia diborano e un composto n butile (simile ma non specificamente identificabili come n butano). Il seguente protocollo può essere facilmente modificato per estensione globale ad altri processi di essiccazione di azoto o di estrazione supercritica.

<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.

Boroidruri metalli alcalini e alcalino-terrosi sono potenziali materiali per lo stoccaggio dell&#39;idrogeno, che offrono un grande contenuto di idrogeno gassoso su decomposizione. 27,29 Altri prodotti di decomposizione come diborano sono anche talvolta stato rilevato nel gas desorbita, ma la loro origine non è a priori chiaro ; è possibile che sono prodotti della decomposizione pura fase, ma possono anche essere impurità o prodotti di reazioni di impurità residue mediante sintesi chimica. 35 L...

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

L&#39;azoto è un fluido supercritico efficace per processi di estrazione o di essiccazione a causa della sua piccola dimensione molecolare, alta densità nel regime supercritico quasi liquido, e inerzia chimica. Presentiamo un protocollo di essiccazione azoto supercritico per il trattamento di purificazione dei reattivi, materiali porosi.

Elaborazione azoto supercritica per la purificazione di reattivi materiali porosi

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

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Research

JoVE Journal

Chemistry

14.7K Views.  Empa, Swiss Federal Laboratories for Materials Science and Technology.  L'azoto è un fluido supercritico efficace per processi di estrazione o di essiccazione a causa della sua piccola dimensione molecolare, alta densità nel regime supercritico quasi liquido, e inerzia chimica. Presentiamo un protocollo di essiccazione azoto supercritico per il trattamento di purificazione dei reattivi, materiali porosi. 

Video: 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.

Sintesi e funzionalizzazione di azoto drogati Coppe nanotubi di carbonio con nanoparticelle di oro come tappi di sughero

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

Ricerca

Ingegneria

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.

Preparazione Silica Aerogel Monoliti tramite una rapida supercritica metodo di estrazione

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

Chimica

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.

Preparazione di altamente poroso Coordinamento rivestimenti polimerici su macroporosi Polymer Monoliti di avanzata Arricchimento fosfopeptidi

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.

Procedure di fumigazione di laboratorio per il controllo dei parassiti con Gas di ossido di azoto

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.

Analisi on-line dei composti contenenti azoto in matrici idrocarburi complessi

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.

Preparazione di biomassa mesoporosi carbonio con più alto azoto-/ ossigeno-chelante di adsorbimento per cu (II) attraverso pre-pirolisi forno a microonde

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.

Misurazione dei tassi potenziali di riduzione del nitrato dissimiliva all'ammonio sulla base di 14NH4/15NH4- Analisi tramite conversione sequenziale in 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.

Proprietà della superficie di sintetizzato nanoporosi carbonio e matrici di silice

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.

Sintesi dell'ammoniaca a bassa pressione

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 ...

Bioingegneria

<meta charset="utf8"></head><body>Versatile sistema domestico a microonde per la sintesi di peptidi

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>Un adattamento economico di un reattore a microonde commerciale per la sintesi di peptidi in fase solida

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

Un adattamento economico di un reattore a microonde commerciale per la sintesi di peptidi in fase solida

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

Elaborazione azoto supercritica per la purificazione di reattivi materiali porosi

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