16033-71-9Relevant academic research and scientific papers
Epoxidation of propylene with nitrous oxide on Rb2SO4-modified iron oxide on silica catalysts
Moens, Bart,De Winne, Hendrik,Corthals, Steven,Poelman, Hilde,De Gryse, Roger,Meynen, Vera,Cool, Pegie,Sels, Bert F.,Jacobs, Pierre A.
, p. 86 - 100 (2007)
The catalytic activity of alkaline and earth alkaline-modified silica-supported metal oxide was investigated for epoxidizing propylene with nitrous oxide. Iron oxide gave the best results, and surprisingly chromium oxide also produced propylene oxide (PO). Unmodified iron oxide catalyst showed low oxidation activity and produced propanal (57% selectivity) in concert with small amounts of acrolein, allyl alcohol, and acetone. After modification, the oxidation rate increased significantly, with PO the principal product. PO selectivities up to 85-90% and space-time yields of 0.25-0.53 mmol PO g-1 h-1 were obtained over supported iron oxide modified with Rb2SO4. A high throughput composition study revealed that other alkali and earth alkali salts were less effective modifiers. Isopropanol decomposition demonstrated that Rb2SO4 severely reduced the acidity of the catalyst. As a result of the neutralization, PO isomerization was drastically reduced. Accordingly, when feeding PO instead of propylene with N2O over the catalyst, a similar reduction of consecutive PO reactions was observed on Rb2SO4 modification. Despite the excellent epoxidation results, a catalytic process remains infeasible due to the restricted service time of the catalyst. Thermogravimetric analyses of a spent catalyst showed carbonaceous residues, suggesting that cokes deactivate the catalyst. Feeding PO indicates that PO itself is a source of cokes. Catalyst regeneration is possible without significant loss of performance. UV-vis DRS and EPR were used to determine the local environment of Fe3+ in the (un)promoted iron oxide catalyst; the findings suggest well-dispersed distorted tetrahedral Fe3+ sites for epoxidation activity. Fe dispersion is ruled by the promoter salts, with both anions and cations being essential. Along with the structural influences, inspection of the catalytic data in concert with XPS and Raman analyses provides evidence of a direct (electronic) promoter effect on the catalytic activity.
Understanding the effect of postsynthesis ammonium treatment on the catalytic activity of Au/Ti-SBA-15 catalysts for the oxidation of propene
Sacaliuc-Parvulescu, Elena,Friedrich, Heiner,Palkovits, Regina,Weckhuysen, Bert M.,Nijhuis, T. Alexander
, p. 43 - 53 (2008)
Postsynthesis ammonium treatment induces a substantial increase in the catalytic activity of Au/Ti-SBA-15 catalysts for the direct vapor-phase epoxidation of propylene using hydrogen and oxygen. The PO formation rate of a calcined Au/Ti-SBA-15 catalyst prepared by this method increased from 4.3 mgPO h-1 g-1cat to 37.2 mgPO h-1 g-1cat at 200 °C compared with a catalyst prepared in an identical manner without this treatment. The catalysts were characterized by XRD, N2-sorption, UV-vis-NIR DRS, 29Si MAS NMR, FT-IR spectroscopy, and TEM to gain insight into the relationship between ammonia treatment and catalyst activity. 29Si MAS NMR measurements proved that the ammonium nitrate solution caused hydrolysis of {triple bond, long}Si{single bond}O{single bond}Si{triple bond, long} or {triple bond, long}Ti{single bond}O{single bond}Si{triple bond, long} bonds, resulting in a Ti-SBA-15 surface with a greater amount of surface hydroxyl groups. FT-IR measurements indicated the presence of amine species that favor the homogeneous deposition of Au nanoparticles. This was confirmed by TEM measurements showing greater metal dispersion for NH4NO3-treated Au/Ti-SBA-15 materials.
Study of the Temperature Dependence of the Reaction of the Nitrate Radical with Propene
Canosa-Mas, Carlos E.,Smith, Stuart J.,Waygood, Steven J.,Wayne, Richard P.
, p. 3473 - 3478 (1991)
Rate constants have been determined for the reaction of NO3 with propene from room temperature up to T = 553 K.Allowance was made in analysing experimental data for probable secondary reactions.The Arrhenius plot shows some curvature at the higher temperatures, which we suggest can be explained by the abstraction of an allylic H atom followed by chain reactions involving fast radical-radical processes.The rate constant at T = 298 K was found to be (0.93 +/- 0.12) * 10-14 cm3 molecule-1s-1.We propose the following Arrhenius expression, in units of cm3 molecule-1s-1, for the addition step in the temperature range T = 298-423 K .For the abstraction reaction of an allylic H atom, we present arguments that suggest Arrhenius parameters of A = 6.8*10-13 cm3molecule-1s-1 and E = 18 kJ mol-1.
CHLORINATION AND CYCLODEHYDRATION OF 1,2-DIOLS WITH THE "TRIPHENYLPHOSPHINE-TETRACHLOROMETHANE-POTASSIUM CARBONATE" REAGENT
Barry, Carey N.,Evans, Slayton A.
, p. 661 - 664 (1983)
The yields of the epoxides obtained from the reaction of 1,2-diols with the "triphenylphosphine-tetrachloromethane-potassium carbonate reagent" range from 27-85percent depending on the relative concentration of triphenylphosphine and diol.In the absence of heterogeneous potassium carbonate, reactions of 1,2-diols with triphenylphosphine-tetrachloromethane give largely 1,2-chlorohydrins.
Reactions of Oxygenated Radicals in the Gas Phase. Part 5. Reactions of Methylperoxyl Radicals and Alkenes
Selby, Keith,Waddington, David J.
, p. 65 - 67 (1980)
The reactions of methylperoxyl radicals with alkenes have been studied at 410 K.The peroxyl radicals were generated by the oxidation of methyl radicals formed during the thermal oxidation of di-t-butyl peroxide.Rate constants for reaction (18) have been determined: k(18)(ethylene) = 1.2+/-0.7 and k(18)(2-methylpropene) = 9.8 +/- 1.6 dm3 mol-1s-1 at 410 K.CH3O2. + >C=C +/- CH3O. (18) An estimate for an activation energy of the abstraction reaction between t-butoxyl radicals and 2-methylpropene is given.
Lewis acid property and catalytic performance of MoO3/SiO 2 for propylene epoxidation by CHP: Effects of precipitant pH value and rare earth additive
Shen, Kai,Liu, Xiaohui,Lu, Guanzhong,Miao, Yongxia,Guo, Yanglong,Wang, Yanqin,Guo, Yun
, p. 78 - 84 (2013)
High dispersed 10% MoO3/SiO2 catalysts were prepared by the sol-gel method using a precipitant (ammonium hydroxide) with different pH values, and investigated by XRD, FT-IR spectroscopy of pyridine adsorbed and Raman spectroscopy techniques, and so on. The results show that the catalytic performance of MoO3/SiO2 for the epoxidation of propylene with cumene hydroperoxide (CHP) is affected by pH value of precipitant, and MoO3/SiO2 prepared with precipitant of pH 9 exhibits the highest yield of propylene oxide (PO). It has been found that the weak Lewis acidic sites on MoO3/SiO2 are the active sites of the propylene epoxidation with CHP, total amount of Lewis acid sites on the catalyst surface is related with the CHP conversion, and the weaker Lewis acid sites is in favor of the propylene epoxidation. When the amount of Lewis acid sites on the catalyst surface is more and their acid strength is higher, the CHP degradation and PO acid-catalytic hydrolysis would be speeded up, resulting in a reduction of the PO selectivity. The concentration and strength of the Lewis acid sites on MoO3/SiO2 are affected by pH of precipitant, and the catalyst prepared with precipitant of pH 9.0 possesses the most weakly Lewis acidic sites and the highest selectivity to PO (91.5%). Besides, the addition of certain amount of Nd can increase the weakly acidic sites to enhance CHP conversion and reduce the Lewis acidity of the catalyst thus suppress PO hydrolysis.
Synergistic Enhancement over Au-Pd/TS-1 Bimetallic Catalysts for Propylene Epoxidation with H2 and O2
Li, Zhishan,Gao, Lin,Zhu, Xiangshuai,Ma, Weihua,Feng, Xiang,Zhong, Qin
, p. 5116 - 5123 (2019)
Au?Pd bimetallic catalyst has attracted significant research interests due to its fascinating properties. Herein, Au?Pd nanoparticles (NPs) supported on titanium silicalite-1 (denoted as Au?Pd/TS-1) were prepared by the alcohol reduction method. The Au?Pd alloy structure was proven via multiple characterization. This Au?Pd/TS-1 bimetallic catalyst showed improved activity compared with monometallic catalyst for propylene epoxidation with H2 and O2. The synergistic enhancement over Au?Pd/TS-1 could be elaborated by H-spillover process, which reduced the apparent activation energy significantly. The insights in this work are of referential importance to understanding the effect of interaction between bimetallic components on reaction system.
Catalytic epoxidation of propylene over a Schiff-base molybdenum complex supported on a silanized mesostructured cellular foam
Chen, Dawei,Jiang, Haoran,Yuan, Xia,Zhang, Xiaoyu
, (2020)
A Schiff-base molybdenum complex (MoO2–salen) supported on mesostructured cellular foam (MCF) was initially prepared by an in situ synthesis method under acidic conditions. Following silanization modification, a MoO2–salen?MCF-S sample with improved surface hydrophobicity was obtained. The ligand environment of molybdenum within the samples has been analyzed by Fourier-transform infrared spectroscopy, ultraviolet/visible spectroscopy, and X-ray photoelectron spectroscopy. Furthermore, the textural and structural properties of the corresponding materials have been characterized by nitrogen adsorption–desorption isotherms and transmission electron microscopy. Despite of the presence of fewer MoO2 species, the results showed that MoO2–salen?MCF-S has more active Mo centers than MoO2–salen and MoO2–salen?MCF on the basis of maintaining the mesoporous structure. The catalytic performances of the synthesized samples were assessed in the epoxidation of propylene with tert-butyl hydroperoxide (TBHP) as an oxidant, and the mechanism of propylene epoxidation under MoO2–salen?MCF was given. The prepared MoO2–salen?MCF-S material showed the best epoxidation performance with 1,2-dichloroethane as a solvent and a molar ratio of propylene to TBHP of 10:1 at 120 °C, giving a TBHP conversion of up to 100% after 1 h, with selectivities for propylene oxide and tert-butyl alcohol reaching 94.7% and 84.6%, respectively.
Epoxidation of olefins catalyzed by a molecular iron n-heterocyclic carbene complex: Influence of reaction parameters on the catalytic activity
Kueck, Jens W.,Raba, Andreas,Markovits, Iulius I.E.,Cokoja, Mirza,Kuehn, Fritz E.
, p. 1882 - 1886 (2014)
The catalytic epoxidation of olefins by an iron(II) complex bearing a tetradentate bis(pyridyl-N-heterocyclic carbene) ligand was investigated. This is the first example of the use of an organometallic iron compound (i.e., with a Fe-C bond) as an olefin epoxidation catalyst. The catalyst system, used without additives, showed good epoxide yields and selectivity for various olefins after a reaction time of 5 min. It was found that the epoxide yield strongly depended on the amount of the peroxide used and its nature and noticeably increased at lower temperatures.
Visible light-induced reaction of NO2 with propene in low-temperature argon and xenon matrices
Nakata, Munetaka,Somura, Yukie,Takayanagi, Masao,Tanaka, Nobuaki,Shibuya, Kazuhiko,Uchimaru, Tadafumi,Tanabe, Kazutoshi
, p. 15815 - 15820 (1996)
Visible light-induced oxygen atom transfer from NO2 to propene has been investigated in low-temperature argon and xenon matrices. The reaction intermediate was propyl nitrite radical, and the final products were methyloxirane and NO, which was confirmed by FT-IR spectroscopy. Conformational structure of propyl nitrite radical was determined by the vibrational analysis of N=O and N-O stretching modes for the normal and 18O-isotope-substituted species with the aid of ab initio calculations, where geometrical optimization was carried out by using the DFT method with the 6-31G* basis set. From the analysis of absorbance growth behavior of the infrared bands for propyl nitrite radical and methyloxirane, first-order rate constants were determined by least-squares fittings. The photoreaction of propene and NO2 in xenon matrices was found to occur more rapidly than in argon matrices. The wavelength dependence of the rate constants is also discussed.
