Catalytic ammonia decomposition over industrial-waste-supported Ru catalysts

Industrial solid wastes (fly ash and red mud) have been employed as supports for preparation of Ru-based catalysts. Physical and chemical treatments on red mud were conducted and these modified supports were also used for preparation of Ru-based catalysts. Those Ru catalysts were characterized by various techniques such as N2 adsorption, H2 adsorption, XRD, XPS, and temperature-programmed reduction (TPR), and were then tested for catalytic ammonia decomposition to hydrogen. It was found that red-mud-supported Ru catalyst exhibits higher ammonia conversion and hydrogen production than fly-ash-supported catalyst. Heat and chemical treatments of the red mud greatly improve the catalytic activity. Moreover, a combination of acid and heat treatments produces the highest catalytic conversion of ammonia.     

Complete combustion of methane over indium tin oxides catalysts

Indium tin oxide (ITO) catalysts with different In/Sn ratios have been prepared by the co-precipitation method. The catalysts were evaluated for methane combustion at different temperatures (673-873 K) with a space velocity of 30 000 h(-1). The results showed that methane could be completely oxidized at 873 K with ITO catalysts. Doping an appropriate amount of tin into In2O3 could greatly improve its activity, while the performances of Indium-doped tin oxides were worse than that of SnO2. A significant improvement of the activity was obtained on the catalyst In8Sn2, which contains 80 wt. % of indium oxide and 20 wt. % of tin oxide. Crystal defection and the amount of oxygen vacancy caused by doping were the main factors that would affect catalytic activity of ITO catalysts. The catalytic activity is strongly inhibited by the presence of a large amount of water vapor at the entire temperature range, while only the activity at low temperature (under 823 K) decreased in the presence of sulfur dioxide. By doping Sn into In2O3, its tolerance to SO2 could be enhanced due to the higher resistance of SnO2.     

Decomposition of the polycyclic nitramine explosive, CL-20, by Fe(0)

CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), C6H6N12O12, is an emerging energetic chemical that may replace RDX, but its degradation pathways are not well-known. In the present study, zerovalent iron was used to degrade CL-20 with the aim of determining its products and degradation pathways. In the absence of O2, CL-20 underwent a rapid decomposition with the concurrent formation of nitrite to ultimately produce nitrous oxide, ammonium, formate, glyoxal, and glycolate. LC/MS (ES-) showed the presence of several key products carrying important information on the initial reactions involved in the degradation of CL-20. For instance, a doubly denitrated intermediate of CL-20 was detected together with the mono- and dinitroso derivatives of the energetic chemical. Two other intermediates with [M-H]- at 392 and 376 Da, matching empirical formulas of C6H7N11O10 and C6H7N11O9, respectively, were detected. Using 15N-labeled CL-20, the two intermediates were tentatively identified as the denitrohydrogenated products of CL-20 and its mononitroso derivative, respectively. The present experimental findings suggest that CL-20 degraded via at least two initial routes: one involving denitration and the second involving sequential reduction of the N-NO2 to the corresponding nitroso (N-NO) derivatives prior to denitration and ring cleavage.     

Platinum particle size and support effects in NO(x) mediated carbon oxidation over platinum catalysts

Platinum metal was dispersed on microporous, mesoporous, and nonporous support materials including the zeolites Na-Y, Ba-Y, Ferrierite, ZSM-22, ETS-10, and AIPO-11, alumina, and titania. The oxidation of carbon black loosely mixed with catalyst powder was monitored gravimetrically in a gas stream containing nitric oxide, oxygen, and water. The carbon oxidation activity of the catalysts was found to be uniquely related to the Pt dispersion and little influenced by support type. The optimum dispersion is around 3-4% corresponding to relatively large Pt particle sizes of 20-40 nm. The carbon oxidation activity reflects the NO oxidation activity of the platinum catalyst, which reaches an optimum in the 20-40 nm Pt particle size range. The lowest carbon oxidation temperatures were achieved with platinum loaded ZSM-22 and AIPO-11 zeolite crystallites bearing platinum of optimum dispersion on their external surfaces.     

Decomposition of linoleic acid hydroperoxides

Summary Methyl 13-hydroperoxy-cis-9-trans-11-octadecadienoate (13-HPODMe) was incubated with ditert-butyl peroxyoxalate or copper(II)palmitate for 3 h at 38 °C. Numerous products were identified and quantitatively analysed. The chemical structures and the amount of products resulting from the 13-HPODMe/Cu(pal)₂ system were influenced by both the presence of oxygen and the addition of some antioxidants (-,-,-tocopherols, ascorbyl palmitate).

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Abbau von LinolsäurehydroperoxidenII. Abbau des 13-Hydroperoxy-cis-9,trans-11-octadecadiensäuremethylesters durch Radikale oder Kupferionen

Zusammenfassung 13-Hydroperoxy-cis-9,trans-11-octadecadiensäuremethylester (13-HPODMe) wurde mit di-tert-Butylperoxyoxalat oder Kupfer(II)palmitat 3 Std bei 38 °C inkubiert. Zahlreiche Produkte wurden identifiziert und quantitativ analysiert. Die chemischen Strukturen und die Mengen der Produkte, die aus dem 13-HPODMe/Cu(pal)₂-System hervorgingen, wurden becinflußt durch die Anwesenheit von Sauerstoff und durch die Zugabe einiger Antioxidantien (-,-,-Tocopherol, Ascorbylpalmitat).

     

Decomposition kinetics of dimethyl sulphide

Dimethyl sulphide is a well characterized off‐flavour in the brewing industry. The thermal re‐creation of dimethyl sulphide by the decomposition of dimethyl sulphide precursor in standardized wort is measured using pressure‐controlled boiling processes at different temperatures. The results are used for the calculation of decomposition speed constants and Arrhenius activation energies. Using these data the re‐creation of dimethyl sulphide during the wort production processes can be calculated and thereby optimized. Copyright © 2014 The Institute of Brewing & Distilling     

Enhanced productivity of electrospun polyvinyl alcohol nanofibrous mats using aqueous N,N-dimethylformamide solution and their application to lipase-immobilizing membrane-shaped catalysts

Electrospun polyvinyl alcohol (PVA) nanofibrous non-woven fabrics have been widely used for cell and enzyme immobilization. Enhancement of the productivity of the material will further enlarge the versatility of them. In this study, a mixture of water and N,N-dimethylformamide (DMF) was used as a solvent of PVA. The productivity defined as ([1 - (amount of polymer which did not come in contact with the collector)/(amount of polymer ejected from the needle for 30 min)] × 100) of electrospun PVA fibers increased from 15 to 92% by increasing the content of DMF from 0 to 10 wt%. As a potential application of the electrospun PVA fibers prepared by the enhanced production system, we encapsulated Burkholderia cepacia (formerly, Pseudomonas cepacia) lipase in the fibers by including lipase powder in the PVA solution before electrospinning, and evaluated catalytic performance of the resultant fibrous catalysts in organic solvent. The lipase encapsulated in the PVA fibers produced from a solution of water and 10 wt% DMF showed a 1.5-fold increase in initial reaction rate in the transesterification of (S)-glycidol and vinyl butyrate to produce (S)-glycidyl butyrate than that encapsulated in the PVA fibers obtained from the solvent without DMF, i.e., water. These findings demonstrate the practicality of the proposed system to enhance the productivity of electrospun PVA fibrous matrices for extended applications of the resultant fibers including the usage as carriers enclosing lipase for reactions in organic solvents.     

Decomposition of linoleic acid hydroperoxides by radicals

Summary Methyl 13-hydroperoxy-cis,trans-9,11-octa-decadienoate (LMPO) was incubated with di-t-butyl peroxyoxalate for 3 h at 38 °C. In the presence of oxygen LMPO decomposed to numerous products among which were methyl 13-oxo-trans,trans-9,11- and methyl 9-oxo-trans,trans-10,12-octadecadienoate, methyl 13-oxo-trans-9,10-epoxy-trans-11-and methyl 9-oxo-trans-12,13-epoxy-trans-10-octadecenoate, methyl 9-hydroxy-trans-12,13-epoxy-trans-10-and methyl 13-hydroxy-trans-9,10-epoxy-trans-11-octadecenoate. Flushing the reaction system with nitrogen reduced the breakdown of LMPO and altered the reaction route in such a manner that a dimethyloctadecadienoate peroxide appeared as the major product.

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Abbau von Linolsäurehydroperoxiden durch RadikaleI. Strukturen der Produkte aus dem 13-Hydroperoxy-cis,traus-9,11-octadecädiensäuremethylester

Zusammenfassung 13-Hydroperoxy-cis,trans-9,11-octadecadiensäuremethylester (LMPO) wurde mit ditert-Butylperoxyoxalat 3 Std bei 38 °C incubiert. In Gegenwart von Sauerstoff wurde das LMPO zu zahlreichen Produkten abgebaut unter denen sich befanden: Methyl-13-oxo-trans,trans-9,11- und Methyl-9-oxo-trans,trans-10,12-octadecadienoat, Methyl-13-oxo-trans-9,10-epoxy-trans-11-und Methyl-9-oxo-trans-12,13-epoxy-trans-10-octadecenoat, Methyl-9-hydroxy-trans-12,13-epoxy-trans-10-und Methyl-13-hydroxy-trans-9,10-epoxy-traps-11-octadecenoat. Begasung des Reaktionssystems mit Stickstoff minderte den LMPO-Abbau und veränderte den Reaktionsverlauf derart, daß ein Di-methyloctadecadienoat-peroxid als Hauptprodukt erschien.

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These results have been presented in part at the 14th ISF Congress in Brighton (September 17th–21st 1978)     

Regeneration of sulfur-fouled bimetallic Pd-based catalysts

Pd-based catalysts provide efficient and selective reduction of several drinking water contaminants, but their long-term application requires effective treatments for catalyst regeneration following fouling by constituents in natural waters. This studytested alumina-supported Pd-Cu and Pd-In bimetallic catalysts for nitrate reduction with H2 after sulfide fouling and oxidative regeneration procedures. Both catalysts were severely deactivated after treatment with microM levels of sulfide. Regeneration was attempted with dissolved oxygen, hydrogen peroxide, sodium hypochlorite, and heated air. Only sodium hypochlorite and heated air were effective regenerants, specifically restoring nitrate reduction rates for a Pd-In/gamma-Al2O3 catalyst from 20% to between 39 and 60% of original levels. Results from ICP-MS revealed that sodium hypochlorite caused dissolution of Cu from the Pd-Cu catalyst but that the Pd-In catalyst was chemically stable over a range of sulfide fouling and oxidative regenerative conditions. Analysis byXPS indicated that PdS and In2S3 complexes form during sulfide fouling, where sulfur is present as S2-, and that regeneration with sodium hypochlorite converts a portion of the S2- to S6+, with a corresponding increase in reduction rates. These results indicate that Pd-In catalysts show exceptional promise for being robust under fouling and regeneration conditions that may occur when treating natural waters.     

双乙酸钠在大空间下分解动力学研究

研究了在55、65、75、85、95、105、115℃的大空间条件下双乙酸钠的分解实验,确定其分解反应为零级反应,并根据不同温度下的分解速率系数求出双乙酸钠的分解动力学方程.     

Decomposition of L-malic acid by wine yeasts

46 yeasts from 5 genera were examined for ability to decompose L -malic acid in grape juice. Saccharomyces yeasts decomposed between 3 and 45%, the amount decomposed being somewhat greater in highly acid juice. Schizosaccharomyces malidevorans brought about complete decomposition with stoicheiometric yield of ethanol. Pichia and Candida growing as oxidative films also brought about some decomposition. Mixed cultures of Saccharomyces and Schizosuccharomyces were examined quantitatively. The difference between yeast and bacterial decomposition of L-malic acid is discussed, as well as the possible selection of yeast cultures for controlled deacidification in wine-making.     

Low-temperature complete combustion of a dilute mixture of methane and propane over transition-metal-doped ZrO2 catalysts: effect of the presence of propane on methane combustion

Complete combustion of dilute methane alone or a dilute mixture of methane and propane over transition-metal (viz. Mn, Co, Cr, Fe, and Ni)-doped ZrO2 (cubic) catalysts at different temperatures (523-873 K) and a space velocity of 51,000 cm3 x g(-1) x h(-1) has been investigated for controlling methane and propane emissions from exhaust gases. The catalysts are compared for their catalytic ignition temperature and activity in the combustion of propane and methane in the presence of each other. The methane combustion activity of all the catalysts is strongly influenced by the presence of propane; it is decreased markedly. In the combustion of mixed methane and propane the Mn-doped ZrO2 and Cr-doped ZrO2 catalysts show the highest activity in the combustion of methane and propane, respectively; the Ni-doped ZrO2 shows the lowest activity in both cases. In the combustion of mixed methane and propanethe propane combustion is enhanced butthe methane combustion retarded when the Cr-doped ZrO2 and Mn-doped ZrO2 catalysts in a 1:1 ratio are used together in different ways (mixed or in layers).     

Decomposition kinetics of umami component during meat cooking

We developed a kinetic model for the decomposition reaction of inosine monophosphate (IMP), which is a umami component, and obtained kinetic parameters based on the amount of IMP in an isothermal experiment. The amount of remaining IMP decreased with heating time, and its reduction rate was the highest at 40 °C. We assumed that the activity of IMP decomposition enzyme is temperature-dependent above 40 °C, and constant below 40 °C. The predicted results using this kinetic model are in good agreement with the experimental ones. Unsteady-state three-dimensional heat transfer analysis of meat during sous-vide cooking was conducted, and the distribution of remaining IMP was predicted. By the end of sous-vide cooking, the ratio of the amount of IMP in the interior of the meat decreased, whereas at the surface region, it was almost the same as the initial value, because the surface temperature reached the inactivation temperature immediately.     

H2O2在漂白体系中的无效分解特性

研究发现，金属螯合剂在无碱体系中对金属离子有良好的螯合效果；金属离子与碱共存对Ｈ２Ｏ２产生相互无关的独立分解作用和相互关联的协同分解作用，其协同分解作用远远大于各自的独立作用之和；金属螯合剂与金属离子共存于碱性体系中会产生螯合不稳定性而出现脱螯合过程：在一定的ｐＨ下，ＭｇＳＯ４和Ｎａ２ＳｉＯ３在无金属离子碱性体系中对Ｈ２Ｏ２具有良好的稳定效果。     

非均相催化剂在制备生物柴油中应用

酯交换是最常见制备生物柴油方法。为提高反应速率,通常需加入催化剂,根据催化剂在反应体系中形态,可分为均相催化剂和非均相催化剂。均相催化剂具有价廉、催化速率高等优点,但在产品后处理时往往会产生大量废酸水或废碱水,污染环境;因此,研究者非常重视非均相催化剂研究和应用。非均相催化剂克服均相催化剂缺点,可回收再利用,是一类环境友好型催化剂,近年发展十分迅速。非均相催化剂主要可分为固体碱性、固体酸性和生物酶催化剂三种;其中,固体碱性和固体酸性催化剂活性较高,使用寿命长;但固体碱性催化剂不适于低质量油脂,如高酸价地沟油。生物酶催化剂具有反应条件温和等优点;但对反应条件要求严格,易中毒失活。该文主要总结近年来国内外有关非均相催化剂催化制备生物柴油发展概况。