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Curt Wentrup - One of the best experts on this subject based on the ideXlab platform.

  • flash Vacuum Pyrolysis
    2018
    Co-Authors: Curt Wentrup
    Abstract:

    Flash Vacuum Pyrolysis (FVP) allows the generation, direct observation, and in many cases isolation of reactive intermediates and unusual molecules such as carbenes, nitrenes, free radicals, and cumulenes. Detailed characterization of unstable species is achieved in conjunction with matrix isolation or gas‐phase spectroscopic techniques. In addition, FVP has many important applications in organic synthesis, where reactions are often initiated by extrusion of small molecules (eg, N2, CO, CO2, or SO2), or by elimination (eg, HCl, CH3COOH, HNCO, or isobutene), or by (retro)pericyclic reaction. These reactions are chemoselective, stereospecific, and usually proceed via the lowest activation energy paths to the products, which are often formed in high yields. Photochemistry is often complementary to Pyrolysis, and the two methods in combination are powerful tools in investigations of chemical reactions.

  • flash Vacuum Pyrolysis techniques and reactions
    Angewandte Chemie, 2017
    Co-Authors: Curt Wentrup
    Abstract:

    Flash Vacuum Pyrolysis (FVP) had its beginnings in the 1940s and 1950s, mainly through mass spectrometric detection of pyrolytically formed free radicals. In the 1960s many organic chemists started performing FVP experiments with the purpose of isolating new and interesting compounds and understanding Pyrolysis processes. Meanwhile, many different types of apparatus and techniques have been developed, and it is the purpose of this review to present the most important methods as well as a survey of typical reactions and observations that can be achieved with the various techniques. This includes preparative FVP, chemical trapping reactions, matrix isolation, and low temperature spectroscopy of reactive intermediates and unstable molecules, the use of online mass, photoelectron, microwave, and millimeterwave spectroscopies, gas-phase laser Pyrolysis, pulsed Pyrolysis with supersonic jet expansion, very low pressure Pyrolysis for kinetic investigations, solution-spray and falling-solid FVP for involatile compounds, and Pyrolysis over solid supports and reagents. Moreover, the combination of FVP with matrix isolation and photochemistry is a powerful tool for investigations of reaction mechanism.

  • flash Vacuum Pyrolysis of azides triazoles and tetrazoles
    Chemical Reviews, 2017
    Co-Authors: Curt Wentrup
    Abstract:

    Flash Vacuum Pyrolysis (FVP) of azides is an extremely valuable method of generating nitrenes and studying their thermal rearrangements. The nitrenes can in many cases be isolated in low-temperature matrices and observed spectroscopically. NH and methyl, alkyl, aralkyl, vinyl, cyano, aryl and N-heteroaryl, acyl, carbamoyl, alkoxycarbonyl, imidoyl, boryl, silyl, phosphonyl, and sulfonyl nitrenes are included. FVP of triazoloazines generates diazomethylazines and azinylcarbenes, which often rearrange to the energetically more stable arylnitrenes. N2 elimination from monocyclic 1,2,3-triazoles can generate iminocarbenes, 1H-azirines, ketenimines, and cyclization products, and 1,2,4-triazoles are precursors of nitrile ylides. Benzotriazoles are preparatively useful precursors of cyanocyclopentadienes, carbazoles, and aza-analogues. FVP of 5-aryltetrazoles can result in double N2 elimination with formation of arylcarbenes or of heteroarylcarbenes, which again rearrange to arylnitrenes. Many 5-substituted and 2...

  • rearrangements of 4 quinolylcarbene 3 quinolylcarbene and 2 quinolylcarbene to 1 naphthylnitrene and cyanoindenes by falling solid flash Vacuum Pyrolysis
    Journal of Organic Chemistry, 2016
    Co-Authors: Nigel Aylward, Jurgen Becker, David Kvaskoff, Curt Wentrup
    Abstract:

    The relationship between 4-quinolylcarbene 17, 3-quinolylcarbene 21, 2-quinolylcarbene 25, and 1-naphthylnitrene 35 has been explored experimentally and computationally. The diazomethylquinolines generated from (5-tetrazolyl)quinolines or 1,2,3-triazolo[1,5-a]quinoline by conventional flash Vacuum Pyrolysis (FVP) were observed by IR spectroscopy. The carbenes were generated by falling solid flash Vacuum Pyrolysis (FS-FVP). 4-Quinolylcarbene 17 was found to rearrange to 3-quinolylcarbene 21 and then to 2-quinolylcarbene 25, and finally via 1-naphthylnitrene 35 to 1-cyanoindene 36, which then isomerizes to 3- and 2-cyanoindenes 12 and 13. The thermal rearrangement of 2-quinolylcarbene to 1-naphthylnitrene was verified by ESR spectroscopy. The reaction mechanism has been elucidated with the help of calculations of the structures and energies of the quinolylcarbenes and 1-naphthylnitrene and the intervening aza-benzobicyclo[4.1.0]heptatrienes, aza-benzocycloheptatetraenes, and aza-benzocycloheptatrienylidenes and the transition states connecting them at the B3LYP/6-31G* level. The nonobserved 1,2-hydrogen shifts in aza-benzocycloheptatetraenes/aza-benzocycloheptatrienylidenes are found to have very high activation barriers.

  • Rearrangements of 4‑Quinolylcarbene, 3‑Quinolylcarbene, and 2‑Quinolylcarbene to 1-Naphthylnitrene and Cyanoindenes by Falling Solid Flash Vacuum Pyrolysis
    2016
    Co-Authors: Nigel Aylward, David Kvaskoff, Jürgen Becker, Curt Wentrup
    Abstract:

    The relationship between 4-quinolylcarbene 17, 3-quinolylcarbene 21, 2-quinolylcarbene 25, and 1-naphthylnitrene 35 has been explored experimentally and computationally. The diazomethylquinolines generated from (5-tetrazolyl)­quinolines or 1,2,3-triazolo­[1,5-a]­quinoline by conventional flash Vacuum Pyrolysis (FVP) were observed by IR spectroscopy. The carbenes were generated by falling solid flash Vacuum Pyrolysis (FS-FVP). 4-Quinolylcarbene 17 was found to rearrange to 3-quinolylcarbene 21 and then to 2-quinolylcarbene 25, and finally via 1-naphthylnitrene 35 to 1-cyanoindene 36, which then isomerizes to 3- and 2-cyanoindenes 12 and 13. The thermal rearrangement of 2-quinolylcarbene to 1-naphthylnitrene was verified by ESR spectroscopy. The reaction mechanism has been elucidated with the help of calculations of the structures and energies of the quinolylcarbenes and 1-naphthylnitrene and the intervening aza-benzobicyclo[4.1.0]­heptatrienes, aza-benzocycloheptatetraenes, and aza-benzocycloheptatrienylidenes and the transition states connecting them at the B3LYP/6-31G* level. The nonobserved 1,2-hydrogen shifts in aza-benzocycloheptatetraenes/aza-benzocycloheptatrienylidenes are found to have very high activation barriers

Weifeng Song - One of the best experts on this subject based on the ideXlab platform.

  • using Vacuum Pyrolysis and mechanical processing for recycling waste printed circuit boards
    Journal of Hazardous Materials, 2010
    Co-Authors: Laishou Long, Sheng Zhong, Weifeng Song
    Abstract:

    Abstract The constant growth in generation of waste printed circuit boards (WPCB) poses a huge disposal problem because they consist of a heterogeneous mixture of organic and metallic chemicals as well as glass fiber. Also the presence of heavy metals, such as Pb and Cd turns this scrap into hazardous waste. Therefore, recycling of WPCB is an important subject not only from the recovery of valuable materials but also from the treatment of waste. The aim of this study was to present a recycling process without negative impact to the environment as an alternative for recycling WPCB. In this work, a process technology containing Vacuum Pyrolysis and mechanical processing was employed to recycle WPCB. At the first stage of this work, the WPCB was pyrolyzed under Vacuum in a self-made batch pilot-scale fixed bed reactor to recycle organic resins contained in the WPCB. By Vacuum Pyrolysis the organic matter was decomposed to gases and liquids which could be used as fuels or chemical material resources, however, the inorganic WPCB matter was left unaltered as solid residues. At the second stage, the residues obtained at the first stage were investigated to separate and recover the copper through mechanical processing such as crushing, screening, and gravity separation. The copper grade of 99.50% with recovery of 99.86% based on the whole WPCB was obtained. And the glass fiber could be obtained by calcinations in a muffle furnace at 600 °C for 10 min. This study had demonstrated the feasibility of Vacuum Pyrolysis and mechanical processing for recycling WPCB.

  • using Vacuum Pyrolysis and mechanical processing for recycling waste printed circuit boards
    Journal of Hazardous Materials, 2010
    Co-Authors: Laishou Long, Sheng Zhong, Shuiyu Sun, Wencan Dai, Jingyong Liu, Weifeng Song
    Abstract:

    The constant growth in generation of waste printed circuit boards (WPCB) poses a huge disposal problem because they consist of a heterogeneous mixture of organic and metallic chemicals as well as glass fiber. Also the presence of heavy metals, such as Pb and Cd turns this scrap into hazardous waste. Therefore, recycling of WPCB is an important subject not only from the recovery of valuable materials but also from the treatment of waste. The aim of this study was to present a recycling process without negative impact to the environment as an alternative for recycling WPCB. In this work, a process technology containing Vacuum Pyrolysis and mechanical processing was employed to recycle WPCB. At the first stage of this work, the WPCB was pyrolyzed under Vacuum in a self-made batch pilot-scale fixed bed reactor to recycle organic resins contained in the WPCB. By Vacuum Pyrolysis the organic matter was decomposed to gases and liquids which could be used as fuels or chemical material resources, however, the inorganic WPCB matter was left unaltered as solid residues. At the second stage, the residues obtained at the first stage were investigated to separate and recover the copper through mechanical processing such as crushing, screening, and gravity separation. The copper grade of 99.50% with recovery of 99.86% based on the whole WPCB was obtained. And the glass fiber could be obtained by calcinations in a muffle furnace at 600 degrees C for 10 min. This study had demonstrated the feasibility of Vacuum Pyrolysis and mechanical processing for recycling WPCB.

Keqiang Qiu - One of the best experts on this subject based on the ideXlab platform.

  • study on delacquer used beverage cans by Vacuum Pyrolysis for recycle
    Environmental Science & Technology, 2013
    Co-Authors: Keqiang Qiu
    Abstract:

    So far, conventional processes that have been employed to delacquer the paints decorated on used beverage cans (UBCs) are less than satisfactory in economic and environmental effect. Therefore, a new method combining Vacuum Pyrolysis with dilute sulfuric acid leaching to delacquer the paints was investigated. The results of Vacuum Pyrolysis showed that the decoating rate increased with the increase of temperature and the paints were almost 100% removed from UBCs under the following conditions: temperature of 650 °C, holding time of 20 min, and residual gas pressure lower than 0.1 kPa. The Pyrolysis oil was mainly composed of phenol and 2-methy-phenol analyzed by GC-MS. The delacquered UBCs were subsequently leached with 5% H2SO4 for 60 s and TiO2 was recovered by calcining the residuals in muffle furnace at 450 °C for 15 min. This innovative technology offers an effective method to delacquer paints from UBCs, which obtains excellent stripping effect and avoids the production of toxic substances generated in direct combustion process. Furthermore, the Pyrolysis oil can be reused as chemical feedstock in other fields.

  • Vacuum Pyrolysis and hydrometallurgical process for the recovery of valuable metals from spent lithium ion batteries
    Journal of Hazardous Materials, 2011
    Co-Authors: Liang Sun, Keqiang Qiu
    Abstract:

    Abstract Spent lithium-ion batteries contain lots of strategic resources such as cobalt and lithium together with other hazardous materials, which are considered as an attractive secondary resource and environmental contaminant. In this work, a novel process involving Vacuum Pyrolysis and hydrometallurgical technique was developed for the combined recovery of cobalt and lithium from spent lithium-ion batteries. The results of Vacuum Pyrolysis of cathode material showed that the cathode powder composing of LiCoO 2 and CoO peeled completely from aluminum foils under the following experimental conditions: temperature of 600 °C, Vacuum evaporation time of 30 min, and residual gas pressure of 1.0 kPa. Over 99% of cobalt and lithium could be recovered from peeled cobalt lithium oxides with 2 M sulfuric acid leaching solution at 80 °C and solid/liquid ratio of 50 g L −1 for 60 min. This technology offers an efficient way to recycle valuable materials from spent lithium-ion batteries, and it is feasible to scale up and help to reduce the environmental pollution of spent lithium-ion batteries.

Alan R Aitken - One of the best experts on this subject based on the ideXlab platform.

  • flash Vacuum Pyrolysis of benzylidene halides benzotrihalides and aryl halides over magnesium
    Journal of Analytical and Applied Pyrolysis, 2017
    Co-Authors: Alan R Aitken, Philip K G Hodgson, Adebayo O Oyewale
    Abstract:

    Abstract Flash Vacuum Pyrolysis at 600 °C through glass wool coated with freshly sublimed magnesium is examined as a preparative method for dehalogenative coupling in organic synthesis. Substituted benzylidene chlorides give predominantly the corresponding stilbenes and in some cases these are readily isolated in pure form. With an ortho -halogen substituent, additional cyclisation gives phenanthrenes but the method is not compatible with the presence of several reactive groups. An ortho- methoxy substituent leads to unexpected formation of mono- and dimethyl products. With 1,4-bis(dihalomethyl)benzenes, halogenated polymers are deposited directly from the gas phase via generation of halogenated p -xylylenes. The 1,2- and 1,3-isomers lead respectively to benzocyclobutadiene, isolated as a dimer, and to pyrene. The 1,4-bis(trihalomethyl)benzenes give more highly halogenated polymers directly from the gas phase via halogenated p -xylylenes. While halobenzenes generally give the corresponding benzenes and biphenyls, 1,2-dihalobenzenes additionally produce triphenylene in preparatively useful yield by a process not involving intermediacy of free benzyne.

  • syntheses of combretastatins d 1 d 2 and d 4 via ring contraction by flash Vacuum Pyrolysis
    Journal of Organic Chemistry, 2017
    Co-Authors: Marina Harras, Wolfgang Milius, Alan R Aitken, Rainer Schobert
    Abstract:

    We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash Vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash Vacuum Pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO2 and CO2.

  • Syntheses of Combretastatins D‑1, D‑2, and D‑4 via Ring Contraction by Flash Vacuum Pyrolysis
    2016
    Co-Authors: Marina Harras, Wolfgang Milius, Alan R Aitken, Rainer Schobert
    Abstract:

    We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash Vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash Vacuum Pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]­metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO2 and CO2

  • recent advances in the synthesis of heterocyclic compounds using flash Vacuum Pyrolysis
    Advances in Heterocyclic Chemistry, 2015
    Co-Authors: Alan R Aitken, Youcef Boubalouta
    Abstract:

    Abstract Applications of flash Vacuum Pyrolysis to the synthesis of heterocyclic compounds published between 2000 and 2015 are described in six major sections with 150 literature references. The emphasis is on methods suitable for preparation of stable heterocyclic products in multi-gram quantities. Consideration of the relatively few reports of synthesis of three- and four-membered rings is followed by the largest single section on the synthesis of five-membered rings, mainly those containing one or two nitrogen atoms. A further major section discusses synthesis of six-membered ring products, again predominantly containing nitrogen, before the final shorter sections on seven-membered, eight-membered, and larger rings.

  • flash Vacuum Pyrolysis of stabilised phosphorus ylides part 13 1 extrusion of ph3p from sulfinyl ylides and reactivity of the resulting sulfinyl carbenes
    Journal of The Chemical Society-perkin Transactions 1, 1998
    Co-Authors: Alan R Aitken, Drysdale, Martin James, Bruce M Ryan
    Abstract:

    Six α-sulfinyl phosphorus ylides 6 have been prepared and are found upon flash Vacuum Pyrolysis at 500 °C to undergo mainly extrusion of Ph3P to give thioesters, presumably by 1,2-oxygen transfer in the initially formed sulfinyl carbenes; for α-arylsulfinyl ylides loss of Ph3PO to give additional products is also observed.

Su Shiung Lam - One of the best experts on this subject based on the ideXlab platform.

  • microwave Vacuum Pyrolysis of waste plastic and used cooking oil for simultaneous waste reduction and sustainable energy conversion recovery of cleaner liquid fuel and techno economic analysis
    Renewable & Sustainable Energy Reviews, 2019
    Co-Authors: Wan Adibah Wan Mahari, Wanxi Peng, Nyuk Ling, Su Shiung Lam, Cheng Tung Chong, Howard A Chase, Zhenling Liew, Suzana Yusup, Eilhann E Kwon
    Abstract:

    Abstract Microwave Vacuum Pyrolysis was examined and compared to conventional Pyrolysis for its technical and economic feasibility in co-processing of waste plastic and used cooking oil simultaneously to generate fuel product. The Pyrolysis demonstrated beneficial process features with respect to high heating rate (29 °C/min) to provide fast heating, high process temperature for extensive cracking (581 °C), short process time (20 min), and low electrical energy consumption (0.38 kWh). The combined use of microwave Vacuum Pyrolysis and activated carbon reaction bed produced up to 84 wt% yield of liquid oil, containing light hydrocarbons and higher heating value (49 MJ/kg) than diesel and gasoline, hence showing great promise for application as fuel. The use of activated carbon reaction bed showed beneficial effect in creating a reduction environment that prevented the oxidation or formation of oxygenated by-products. A positive synergistic effect between waste plastic and used cooking oil was also observed. The liquid oil obtained from this Pyrolysis approach presented a low oxygen and nitrogen content, and free of sulphur, showing ‘cleaner’ properties with respect to reduced char residues, sludge formation, corrosiveness, degradation of oil quality, and emission of undesired SOx and NOx during its utilization in combustion process. The techno-economic analysis indicated that this Pyrolysis approach showed low production cost (USD 0.25/L compared to USD 0.523/L of diesel price in Malaysia). Our results demonstrate that microwave Vacuum Pyrolysis is potentially economically feasible and show promise as a sustainable approach for energy conversion in providing improved process features and production of cleaner liquid fuel.

  • microwave Vacuum Pyrolysis conversion of waste mushroom substrate into biochar for use as growth medium in mushroom cultivation
    Journal of Chemical Technology & Biotechnology, 2019
    Co-Authors: Wai Lun Nam, Xue Yee Phang, Rock Keey Liew, Xie Yi Lee, Nyuk Ling, Su Shiung Lam, Peter Ny Yek, Mohd Hnb Rosli
    Abstract:

    BACKGROUND: Spent mushroom substrate (SMS), largely produced as an agriculture waste from mushroom cultivation, was transformed into biochar via microwave Vacuum Pyrolysis under different ratios of SMS to microwave absorbent (1:1, 1:2, and 1:3). The biochar was then examined for its potential to be re‐used in mushroom cultivation as a growth medium added to conventional mushroom baglog (plastic bag with mushroom seeds and culture substrates containing rice straw, sawdust, lime and water), with emphasis on its ability to form mycelium – a fungus that grows into mushroom from its seeds. RESULT: The Pyrolysis generated up to 36 wt% biochar yield with a large adsorption area (up to 215 m² g‐¹) and less water (4 wt%), indicating that many adsorption sites are available on which mushroom seeds, nutrient and water can be adsorbed onto in order to form mycelium (and subsequently mushroom). The biochar added to grow mushroom in baglog recorded a higher water retention percentage (up to 59%), a higher mycelium colonization length in 8 days (6.3 cm), coverage area (up to 259 cm²) and total mycelium growth volume (317 cm³), and resulted in a higher yield of mushroom (200 g month‐¹) than that recorded for the conventional baglog without biochar (160 g month‐¹). CONCLUSION: The results indicated that biochar produced from SMS using microwave Vacuum Pyrolysis shows great potential in retaining water and nutrient that in turn promotes the formation of mycelium that leads to increased growth of mushroom in its cultivation. © 2018 Society of Chemical Industry

  • production of bio fertilizer from microwave Vacuum Pyrolysis of palm kernel shell for cultivation of oyster mushroom pleurotus ostreatus
    Science of The Total Environment, 2018
    Co-Authors: Wai Lun Nam, Xue Yee Phang, Rock Keey Liew, Nyuk Ling, Mohd Haqqi Nazilli Bin Rosli, Su Shiung Lam
    Abstract:

    Microwave Vacuum Pyrolysis of palm kernel shell (PKS) was performed to produce biochar, which was then tested as bio-fertilizer in growing Oyster mushroom (Pleurotus ostreatus). The Pyrolysis approach produced biochar containing a highly porous structure with a high BET surface area of up to 270m2/g and low moisture content (≤10wt%), exhibiting desirable adsorption properties to be used as bio-fertilizer since it can act as a housing that provides many sites on which living microorganisms (mycelium or plant-growth promoting bacteria) and organic nutrients can be attached or adsorbed onto. This could in turn stimulate plant growth by increasing the availability and supply of nutrients to the targeted host plant. The results from growing Oyster mushroom using the biochar recorded an impressive growth rate and a monthly production of up to about 550g of mushroom. A shorter time for mycelium growth on one whole baglog (21days) and the highest yield of Oyster mushroom (550g) were obtained from cultivation medium added with 20g of biochar. Our results demonstrate that the biochar-based bio-fertilizer produced from microwave Vacuum Pyrolysis of PKS shows exceptional promise as growth promoting material for mushroom cultivation.