F+:Highly flammable;
78-79-5Relevant articles and documents
Oyekan,Dent
, p. 32,37 (1978)
Harding et al.
, p. 634 (1969)
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Usow et al.
, p. 2721,2724; engl.Ausg.S.2761 (1957)
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Isomerization of 1-Methylcyclobutene by Single Collision Activation at a Surface. Variation of Initial Energy
Arakawa, R.,Rabinovitch, B. S.
, p. 4772 - 4776 (1982)
The reaction probability per collision, Pc, for 1-methylcyclobutene activated at a hot seasoned fused silica surface has been measured under single collision conditions over the reactor temperature range Tr = 480-800 K.The initial thermal vibrational energy population distribution of the cyclobutene molecules was varied from Tc = 273 K to Tc 570 K.The reaction is isomerization to isoprene.Mixed samples of 1-methylcyclobutene and cyclobutene (which had been studied earlier) were used for internal comparison under the same conditions.These experiments provide a test of the relative suitability of various analytical forms for the collisional transition probability matrix P.Stochastic calculations with a Gaussian form provide the best overall fit to the data.The calculated average amount of energy (E0) transferred from the hot molecules in a vibrational down transition from the reaction threshold energy level, E0, declined from 7220 to 3890 cm-1 with increase in surface temperature from 600 to 800 K.The experimental collisional efficiency, β1, declined from 0.39 to 0.035 over the combination temperature range Tr,Tc = 600,500 to 800,293.Strong collider behavior was observed with both 1-methylcyclobutene and cyclobutene for Tr less than 450 K.
Isoprene Synthesis from Formaldehyde and Isobutylene in the Presence of Aluminum- and Niobium-Containing BEA Catalysts
Chistov, D. L.,Drozhzhin, V. R.,Ivanova, I. I.,Kots, P. A.,Ponomareva, O. A.,Rodionova, L. I.
, p. 942 - 949 (2020)
Abstract: A single-stage gas-phase synthesis of isoprene from formaldehyde and isobutylene in the presence of Al–BEA and Nb–BEA zeolite catalysts containing different amounts of aluminum and niobium has been studied. The physicochemical properties of the catalysts have been studied by low-temperature nitrogen adsorption, infrared spectroscopy of adsorbed CO, X-ray fluorescence analysis, and ammonia TPD methods. Catalytic tests have shown that, at similar formaldehyde conversion values, the isoprene selectivity is higher in the presence of the Al-containing BEA catalysts. It has been found that Al–BEA with Si/Al = 12 exhibits the highest activity in isoprene synthesis.
Bateman
, p. 1 (1947)
Uchida et al.
, p. 1118 (1971)
Mechanisms of Methylenecyclobutane Hydrogenation over Supported Metal Catalysts Studied by Parahydrogen-Induced Polarization Technique
Salnikov, Oleg G.,Burueva, Dudari B.,Kovtunova, Larisa M.,Bukhtiyarov, Valerii I.,Kovtunov, Kirill V.,Koptyug, Igor V.
, (2022/03/15)
In this work the mechanism of methylenecyclobutane hydrogenation over titania-supported Rh, Pt and Pd catalysts was investigated using parahydrogen-induced polarization (PHIP) technique. It was found that methylenecyclobutane hydrogenation leads to formation of a mixture of reaction products including cyclic (1-methylcyclobutene, methylcyclobutane), linear (1-pentene, cis-2-pentene, trans-2-pentene, pentane) and branched (isoprene, 2-methyl-1-butene, 2-methyl-2-butene, isopentane) compounds. Generally, at lower temperatures (150–350 °C) the major reaction product was methylcyclobutane while higher temperature of 450 °C favors the formation of branched products isoprene, 2-methyl-1-butene and 2-methyl-2-butene. PHIP effects were detected for all reaction products except methylenecyclobutane isomers 1-methylcyclobutene and isoprene implying that the corresponding compounds can incorporate two atoms from the same parahydrogen molecule in a pairwise manner in the course of the reaction in particular positions. The mechanisms were proposed for the formation of these products based on PHIP results.
Study on heteropolyacid-based catalysts with high activity and reusability for isoprene synthesis from formaldehyde and isobutene
Wang, Qingxue,Luo, Xu,Liu, Li,Tao, Shenghui,Xu, Shan
, p. 5371 - 5381 (2021/04/06)
Silica-supported heteropolyacid catalysts with different pore structures were synthesizedviaimpregnation method using silicalite-1 with three-dimensional MFI structure, two-dimensional hexagonal SBA-15 and amorphous silica as supports. Moreover, these catalysts were employed for the gas phase one-step synthesis of isoprene from isobutene and formaldehyde. The result showed that the activity of silicotungstic acid supported on silicalite-1 (SiW/S-1) catalysts was significantly better than that on other supports, which indicates that the three-dimensional MFI structure and suitable pore size of silicalite-1 were more conducive to the production of isoprene. Furthermore, the formation rate of isoprene over 20% SiW/S-1 catalyst reached up to 8.5 times that on the bulk silicotungstic acid catalyst, which could be attributed to the highly dispersed silicotungstic acid and the suitable acidity produced by the strong interaction between silicotungstic acid and silicalite-1. In addition, the 20 wt% SiW/S-1 catalyst exhibited excellent reusability and was reused 10 times without obvious loss of activity.
Piperazine-promoted gold-catalyzed hydrogenation: The influence of capping ligands
Barbosa, Eduardo C. M.,Camargo, Pedro H. C.,Fiorio, Jhonatan L.,Hashmi, A. Stephen K.,Kikuchi, Danielle K.,Rossi, Liane M.,Rudolph, Matthias
, p. 1996 - 2003 (2020/04/22)
Gold nanoparticles (NPs) combined with Lewis bases, such as piperazine, were found to perform selective hydrogenation reactions via the heterolytic cleavage of H2. Since gold nanoparticles can be prepared by many different methodologies and using different capping ligands, in this study, we investigated the influence of capping ligands adsorbed on gold surfaces on the formation of the gold-ligand interface. Citrate (Citr), poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), and oleylamine (Oley)-stabilized Au NPs were not activated by piperazine for the hydrogenation of alkynes, but the catalytic activity was greatly enhanced after removing the capping ligands from the gold surface by calcination at 400 °C and the subsequent adsorption of piperazine. Therefore, the capping ligand can limit the catalytic activity if not carefully removed, demonstrating the need of a cleaner surface for a ligand-metal cooperative effect in the activation of H2 for selective semihydrogenation of various alkynes under mild reaction conditions.
