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de Farias RF de Souza JM de Melo JV Airoldi C 《Journal of colloid and interface science》2000,227(1):147-151
Polyaniline deposited on As(2)O(3) surface resulted in a new material, which was characterized by infrared spectoscopy, thermogravimetry, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and cyclic voltammetry. The mass percentage of polymer deposited on oxide surface is approximately 13%. The scanning electron microscopy images as well as the X-ray diffraction patterns provided conclusive evidence that the oxide surface is coated by the polymer. The cyclic voltammograms of the polyaniline adsorbed on As(2)O(3) surface showed that the adsorbate exerts remarkable effects on redox processes on this oxide. The pure oxide exhibited two oxidation/reduction peaks at 0.25/-0.06 and 0.47/-0.25 V attributed tentatively to the processes As(2)O(3)(s)+6H(+)+6e(-)=2As(s)+3H(2)O and As(s)+3H(+)+3e(-)=AsH(3)(g), respectively. The polyaniline-coated sample exhibited a better-defined voltammogram in which the first oxidation peak of the oxide had its intensity increased about four times. Copyright 2000 Academic Press. 相似文献
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Aitala EM Amato S Anjos JC Appel JA Ashery D Banerjee S Bediaga I Blaylock G Bracker SB Burchat PR Burnstein RA Carter T Carvalho HS Costa I Cremaldi LM Darling C Denisenko K Fernandez A Gagnon P Gerzon S Gobel C Gounder K Granite D Halling AM Herrera G Hurvits G James C Kasper PA Kondakis N Kwan S Langs DC Leslie J Lichtenstadt J Lundberg B Manacero A MayTal-Beck S Meadows B de Mello Neto JR Milburn RH de Miranda JM Napier A Nguyen A d'Oliveira AB O'Shaughnessy K Peng KC Perera LP Purohit MV 《Physical review letters》1996,76(3):364-367
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Maria Inês F. Mota José Miguel Loureiro Alírio E. Rodrigues 《Separation & Purification Reviews》2016,45(3):227-259
Lignin is an underexploited side-stream of pulp and paper industry and biorefineries, being used for energy production at mill site or as low value material for dispersants or binding applications. However, an integrated process of reaction and separation can be implemented for the production of high added-value monomeric phenolic chemicals such as vanillin and syringaldehyde. In this review, the main research advances in the recovery of vanillin and syringaldehyde resulting from oxidation of lignin are addressed, covering various separation methodologies namely liquid-liquid extraction, supercritical fluid extraction, distillation, crystallization, membrane separation, and adsorption. Studies in this area started in the early years of the 20th century, but in the last decades several processes have been suggested, mainly for vanillin separation. Finding the ultimate industrially feasible process is still a necessary task and this review points out the most promising technologies and sequence of processes. 相似文献
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Cláudio M. Nunes Srinivas Doddipatla Gonçalo F. Loureiro José P. L. Roque Nelson A. M. Pereira Teresa M. V. D. Pinho e Melo Rui Fausto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(67):e202202306
Quantum mechanical tunneling of heavy-atoms and vibrational excitation chemistry are unconventional and scarcely explored types of reactivity. Once fully understood, they might bring new avenues to conduct chemical transformations, providing access to a new world of molecules or ways of exquisite reaction control. In this context, we present here the discovery of two isomeric benzazirines exhibiting differential tunneling-driven and vibrationally-induced reactivity, which constitute exceptional results for probing into the nature of these phenomena. The isomeric 6-fluoro- and 2-fluoro-4-hydroxy-2H-benzazirines ( 3-a and 3′-s ) were generated in cryogenic krypton matrices by visible-light irradiation of the corresponding triplet nitrene 3 2-a , which was produced by UV-light irradiation of its azide precursor. The 3′-s was found to be stable under matrix dark conditions, whereas 3-a spontaneously rearranges (τ1/2 ∼64 h at 10 and 20 K) by heavy-atom tunneling to 3 2-a . Near-IR-light irradiation at the first OH stretching overtone frequencies (remote vibrational antenna) of the benzazirines induces the 3′-s ring-expansion reaction to a seven-member cyclic ketenimine, but the 3-a undergoes 2H-azirine ring-opening reaction to triplet nitrene 3 2-a . Computations demonstrate that 3-a and 3′-s have distinct reaction energy profiles, which explain the different experimental results. The spectroscopic direct measurement of the tunneling of 3-a to 3 2-a constitutes a unique example of an observation of a species reacting only by nitrogen tunneling. Moreover, the vibrationally-induced sole activation of the most favorable bond-breaking/bond-forming pathway available for 3-a and 3′-s provides pioneer results regarding the selective nature of such processes. 相似文献
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JM Pakarinen H Moisio S Holopainen P Vainiotalo 《Rapid communications in mass spectrometry : RCM》1999,13(14):1485-1490
2-Methoxyethanol chemical ionization of amines, carboxylic acids and amino acids has been found to produce numerous adduct ions. The most intense adduct ions for amines are [M + H](+) and [M + 77](+), for carboxylic acids [M + 27](+), [M + 59](+) and [M + 77](+), and for amino acids [M + H](+), [M + 13](+), [M + 27](+) and [M + 77](+). Either the adduct ion [M + H](+) or [M + 77](+) was the most abundant ion found for amino acids. The proton affinities of amino acids are noticed to control the formation of the [M + H](+) and [M + 77](+) ions. The relative abundance of [M + 13](+) and [M + 27](+) ions varied for different amino acids being most intense for phenylalanine and aspartic acid. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
110.
L. Colombier W. G. Eversole R. W. Mc Lachlan J. A. de Loureiro H. Kleinmann R. Tarlet und A. Goin 《Fresenius' Journal of Analytical Chemistry》1933,93(1-2):36-38
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