115-11-7Relevant articles and documents
Alkylperoxy and Alkyl Radicals. 5. Infrared Spectra and Ultraviolet Photolysis of t-C4H9O2 Radicals in Argon plus Oxygen Matrices
Chettur, G.,Snelson, A.
, p. 5873 - 5875 (1987)
tert-Butyl radicals formed by the pyrolysis of azoisobutane were isolated in matrices of Ar + 10percent 16O2 and Ar + 5percent 16O2 + 5percent 18O2.IR spectra of the resulting trapped species were obtained before and after irradiation of the matrices with a medium-pressure Hg arc lamp.In the 1200-200-cm-1 spectral range, nine absorption bands were observed and assigned to the tert-butylperoxy radical.A summary of the known vibration frequencies assigned to primary, secondary, and tertiary alkylperoxy radical centers is presented.
Key Roles of Lewis Acid-Base Pairs on ZnxZryOz in Direct Ethanol/Acetone to Isobutene Conversion
Sun, Junming,Baylon, Rebecca A. L.,Liu, Changjun,Mei, Donghai,Martin, Kevin J.,Venkitasubramanian, Padmesh,Wang, Yong
, p. 507 - 517 (2016)
The effects of surface acidity on the cascade ethanol-to-isobutene conversion were studied using ZnxZryOz catalysts. The ethanol-to-isobutene reaction was found to be limited by the secondary reaction of the key intermediate, acetone, namely the acetone-to-isobutene reaction. Although the catalysts with coexisting Br?nsted acidity could catalyze the rate-limiting acetone-to-isobutene reaction, the presence of Br?nsted acidity is also detrimental. First, secondary isobutene isomerization is favored, producing a mixture of butene isomers. Second, undesired polymerization and coke formation prevail, leading to rapid catalyst deactivation. Most importantly, both steady-state and kinetic reaction studies as well as FTIR analysis of adsorbed acetone-d6 and D2O unambiguously showed that a highly active and selective nature of balanced Lewis acid-base pairs was masked by the coexisting Br?nsted acidity in the aldolization and self-deoxygenation of acetone to isobutene. As a result, ZnxZryOz catalysts with only Lewis acid-base pairs were discovered, on which nearly a theoretical selectivity to isobutene (～88.9%) was successfully achieved, which has never been reported before. Moreover, the absence of Br?nsted acidity in such ZnxZryOz catalysts also eliminates the side isobutene isomerization and undesired polymerization/coke reactions, resulting in the production of high purity isobutene with significantly improved catalyst stability (2% activity loss after 200 h time-on-stream). This work not only demonstrates a balanced Lewis acid-base pair for the highly active and selective cascade ethanol-to-isobutene reaction but also sheds light on the rational design of selective and robust acid-base catalyst for C-C coupling via aldolization reaction.
A combined experimental and theoretical study of the homogeneous, unimolecular decomposition kinetics of 3-chloropivalic acid in the gas phase
Chuchani,Rotinov,Andres,Domingo,Safont
, p. 1869 - 1875 (2001)
Decomposition kinetics of 3-chloropivalic acid in the gas phase were determined in a static system over the temperature and pressure ranges of 380.5-430.1 °C and 43-120 Torr, respectively. The reaction, in vessel seasoned with allyl bromide, and in the presence of free-radical suppresser toluene, is homogeneous, unimolecular, and follows a first-order rate law. The rate coefficients are given by the following equation: log k1 (s-1) = (12.42 ± 0.36) - (205.8 ± 4.7) kJ mol-1(2.303RT)-1. The reaction mechanism for the formation of isobutene, hydrogen chloride, and carbon dioxide has been theoretically characterized. The theoretical study, at MP2/6-31G** computational level, points out that the molecular mechanism corresponds to a concerted and highly synchronous process yielding the products. An analysis of bond orders and NBO charges shows that the polarization of the C-Cl breaking bond can be considered the driving force for this fragmentation process. The rate coefficients obtained from experimental data and theoretical calculations are in good agreement.
A Fourier-transform Infrared and Catalytic Study of the Evolution of the Surface Acidity of Zirconium Phosphate following Heat Treatment
Busca, Guido,Lorenzelli, Vincenzo,Galli, Paola,Ginestra, Aldo La,Patrono, Pasquale
, p. 853 - 864 (1987)
The surface acidity of zirconium phosphate at different stages of dehydration and heat treatments has been studied by Fourier-transform infrared spectroscopy of adsorbed pyridine, acetonitrile and acetone and by catalytic cativity in the isomerization of but-1-ene.Broensted-acidic surface POH and P(OH)2 groups are identified -1, respectively> whose strenght increases slightly on bulk dehydration.They are thought to be responsible for the activity in but-1-ene isomerization, which also increases during condensation to pyrophosphate.Lewis-acidic sites of medium-high strenght have also been found, and responsible for the formation of chemisorbed forms of pyridine (ν8a = 1610 cm-1), acetonitrile -1> and acetone -1>.Surface ZrOH groups are also detected on the layered ZrP2O7 surface.The results illustrate the role of exposed planes, both parallel and perpendicular to the layered structure.
Investigations into the origin of the remarkable catalytic performance of aged H-ferrierite for the skeletal isomerization of 1-butene to isobutene
Lee, Song-Ho,Shin, Chae-Ho,Hong, Suk Bong
, p. 200 - 211 (2004)
The catalytic properties of the proton form of six different 10-ring zeolites (clinoptilolite, ferrierite, ZSM-22, SUZ-4, ZSM-57, and ZSM-5), together with the dealuminated analogs of some of these materials prepared via oxalic acid treatment, are compared in the skeletal isomerization of 1-butene. While the pore shape of 10-ring channels in this series of medium-pore zeolites was found to be the key parameter substantially governing the isomerization activity, the catalytic data obtained from two H-ferrierites with similar Si/Al ratios but different crystal sizes reveal that the rate of coke formation on this particular zeolite structure, as well as its isobutene selectivity, can differ significantly according to the zeolite crystal size. The overall results of our study strongly suggest that the remarkable isobutene selectivity of aged H-ferrierite is a consequence of pore mouth shape catalysis over the Bronsted acid sites located near the 10-ring pore mouths with a suitable degree of ellipticity, which may come not only from the unique geometrical constraints imposed by the dual pore system of this particular zeolite, but also from its behavior of being normally synthesized with a submicrometer crystal size.
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Schultz,Kistiakowsky
, p. 395,396 (1934)
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A Kinetic Study of the Thermal Decarboxylation of α,α-Difluoro β-Lactones
Ocampo, Rogelio,Dolbier Jr., William R.,Bartberger, Michael D.,Paredes, Rodrigo
, p. 109 - 114 (1997)
The rates of thermolysis of α,α-difluoro β-lactones 1, leading to CO2 and 1,1-difluoro olefins, have been obtained in the gas phase and in solution, and the activation parameters are reported. Ab initio calculations on the fluoro and nonfluorinated βlactone systems are also reported. The gas-phase kinetic and theoretical results are discussed in terms of a probable concerted, asynchronous, nonpolar mechanism, whereas the solution kinetics, which include extensive solvent effect studies, are discussed in terms of a polar mechanism which probably involves formation of a zwitterionic intermediate.
Production of isobutylene from acetone over micro–mesoporous catalysts
Ponomareva,Mal’tseva,Maerle,Rodionova,Pavlov,Dobryakova,Belova,Ivanova
, p. 253 - 258 (2016)
The production of isobutylene from acetone over micro–mesoporous catalysts with different mesopore contents, which have been prepared using hydrothermal recrystallization of mordenite (MOR) zeolite modified with cesium acetate by incipient wetness impregnation, has been studied. It has been shown that cesium is inserted into the cation positions during the modification, at the same time the number of Br?nsted acid sites in the samples decreased. It has been found that an increase in the content of mesopores in the catalyst leads to an increase in the initial rates of acetone conversion and isobutylene formation as a result of removing diffusion limitations. Br?nsted acid sites have been shown to be preferable for the selective production of isobutylene from acetone. Micro–mesoporous materials operate more stably as compared to microporous materials.
The Elimination Kinetics of 2-Bromo-3-Methylbutyric Acid in the Gas Phase
Chuchani, Gabriel,Dominguez, Rosa M.
, p. 85 - 88 (1995)
The kinetics of 2-bromo-3-methylbutyric acid in the gas phase was studied over the temperature range of 309.3 - 357.0 deg C and pressure range of 15.5 - 100.0 torr.This process, in seasoned static reaction vessels and in the presence of the free radical i
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Margerum et al.
, p. 1549,1551 (1959)
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Enhancement of catalytic wet air oxidation of tert-amyl methyl ether by the addition of Sn and CeO2 to Rh/Al2O3 catalysts
Cuauhtémoc,Del Angel,Torres,Angeles-Chavez,Navarrete,Padilla
, p. 180 - 187 (2011)
The Rh and Rh-Sn supported catalyst on γ-Al2O3 and γ-Al2O3-CeO2 (loading 1, 5 and 20 Ce wt%) were characterized by means of electron microscopy (TEM), temperature programmed reduction (TPR), Fourier transformed infrared of CO adsorption (FTIR-CO) and X-ray photoelectron spectroscopy (XPS). The catalysts were tested in the catalytic wet air oxidation of an aqueous solution of 227 ppm of TAME and 1 g/L of catalyst (120 °C and 10 bar of oxygen partial pressure). The rhodium monometallic catalysts showed an increase in the activity with the load of cerium oxide in the catalyst. The coexistence of Rh°/Rh δ+ and Ce4+/Ce3+ redox couples facilitates the activation of TAME and hence the catalytic activity and selectivity to mineralization. The addition of Snδ+ enhances the activity and selectivity; this is explained by assuming that Sn δ+ acts as Lewis acid sites trapping the TAME molecules for further oxidation on rhodium metal particles.
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White,Field
, p. 2148,2151, 2152 (1975)
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Stepwise mechanism of formal 1,5-sigmatropic rearrangement of dimethyl 3,3-dialkyl-3H-pyrazole-4,5-dicarboxylates
Majchrzak, Michael W.,Jefferson, Elizabeth,Warkentin, John
, p. 2449 - 2451 (1990)
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Direct conversion of bio-ethanol to propylene in high yield over the composite of In2O3 and zeolite beta
Xue, Fangqi,Miao, Changxi,Yue, Yinghong,Hua, Weiming,Gao, Zi
, p. 5582 - 5590 (2017)
A series of In2O3-beta composites with different contents of zeolite beta were prepared by the deposition-precipitation method, followed by calcination at 700 °C, and their catalytic performance in the conversion of ethanol to propylene (ETP) was investigated. The physicochemical properties of the as-synthesized materials were characterized by XRD, N2 adsorption, SEM, NH3-TPD, CO2-TPD and a probe reaction. The combination of In2O3 and zeolite beta improves the propylene yield significantly. The optimal result was observed for the composite with a beta content of 20-50%, which gave ca. 50% yield of propylene. The role of beta in the In2O3-beta composite catalyst is to promote the conversion of the intermediate of acetone to propylene via an additional reaction pathway, which accounts for the superior propylene yield of the In2O3-beta composite in comparison with In2O3 (ca. 32%). The proximity of these two components (In2O3 and zeolite beta) plays a crucial role in achieving a high yield of propylene for the ETP reaction.
Factors affecting the selective isomerization of n-butene into isobutene over ferrierite catalysts
Meriaudeau,Tuan, Vu A.,Hung, Le N.,Naccache,Szabo
, p. 329 - 332 (1997)
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CHLOROTRIMETHYLSILANE-PHENOL AS A MILD DEPROTECTION REAGENT FOR THE TERT-BUTYL BASED PROTECTING GROUPS IN PEPTIDE SYNTHESIS
Kaiser, Emil,Tam, James P.,Kubiak, Teresa M.,Merrifield, R. B.
, p. 303 - 306 (1988)
Efficient deprotection of the tertbutyl urethane group by 1 M Me3SiCl- 1 M and 3 M-phenol reagents is described.
Catalytic dehydrogenation of isobutane over a Ga2O3/ZnO interface: Reaction routes and mechanism
Wang, Guowei,Li, Chunyi,Shan, Honghong
, p. 3128 - 3136 (2016)
In this work, physical mixtures of ZnO and Ga2O3, even with a small amount of Ga2O3, were found to exhibit greatly enhanced catalytic performance for isobutane dehydrogenation compared to their individual components, namely solely ZnO or Ga2O3. The activity test results under different packing patterns indicated that, the interface between the two component oxides played a crucial role in improving the dehydrogenation performance. Moreover, consistent with the highest dehydrogenation reactivity, the largest activation energy for isobutane desorption over ZnO-Ga2O3 was determined using an isobutane-TPD test. The observed synergistic effect of ZnO and Ga2O3 could be understood as being that, Lewis acid sites provided by Ga2O3 promoted the heterolytic cleavage of C-H bonds in isobutane over ZnO, thereby increasing the isobutane conversion. On the surface of ZnO-Ga2O3, a double-site adsorption of isobutane was further speculated through FT-IR spectra analysis, and one-step decomposition was probably the actual reaction pathway of isobutane. In addition, from understanding that catalyst deactivation was caused by highly graphitized coke deposition, the deactivated catalyst was regenerated through air combustion, and good catalyst stability was demonstrated through continuous reaction-regeneration cycles.
[(≡SiO)TaV (=CH2)Cl2], the first tantalum methylidene species prepared and identified on the silica surface
Chen, Yin,Callens, Emmanuel,Abou-Hamad, Edy,Basset, Jean-Marie
, p. 3 - 6 (2013)
A novel surface tantalum methylidene [(≡SiO)TaV (=CH 2)Cl2] was obtained via thermal decomposition of the well-defined surface species [(≡SiO)TaVCl2Me 2]. This first surface tantalum methylidene ever synthesized has been fully characterized and the kinetics of the a-hydrogen abstraction reaction has also been investigated in the heterogeneous system.
Selective Isomerization of Butene to Iso-Butene
Cheng, Zheng Xing,Ponec, Vladimir
, p. 607 - 616 (1994)
Selective isomerization of butene to iso-butene has been studied with pure and variously modified alumina as catalysts.Results can be self-consistently eplained by concluding that (i) the molecular mechanism operates and requires Lewis acid sites, the presence and quality of which can be modulated by heat treatment in hydrogen, by surface modification with halogens, and by application of certain catalytic poisons, and (ii) the bimolecular mechanism is related to the Broensted acid sites and is stimulated, as expected, by increased pressure of n-butene.
Selective Oxidative Dehydrogenation of Isobutane over a Y2O3-CeF3 Catalyst
Zhang, Wei-De,Tang, Ding-Liang,Zhou, Xiao-Ping,Wan, Hui-Lin,Tsai, K. R.
, p. 771 - 772 (1994)
The multi-valence anion modified complex catalyst Y2O3-CeF3 was found to be selective for the oxidative dehydrogenation of isobutane to isobutene at a relatively high conversion.
EXTRACTION OF STANDARD HELMHOLTZ FUNCTIONS FROM AFFINITY RATE DATA
Garfinkle, Marvin
, p. 717 - 726 (1985)
An extrapolation procedure to extract standard Helmholtz functions from empirical kinetic data without reference to reaction mechanisms has been developed using an analytical description of the affinity decay rate.
The Study of CrOx-Containing Catalysts Supported on ZrO2, CeO2, and CexZr(1–x)O2 in Isobutane Dehydrogenation
Bugrova,Mamontov
, p. 143 - 149 (2018)
Olefin hydrocarbons are valuable raw materials for petrochemical and polymer manufacturing. Highly effective, but toxic chromium-containing catalytic materials are the most widely used catalysts to obtain olefins in industry. In this regard, the urgent challenge to increase the efficiency of oil processing is to develop the catalysts with low content of harmful active component. In the present study, the catalysts with low chromium content (1 theoretical monolayer = 5 Cr atoms per nm2 of support) were synthesized by incipient wetness impregnation of the supports (Al2O3, ZrO2, CeO2, and CexZr(1–x)O2). The samples obtained were characterized by low-temperature nitrogen adsorption, X-ray diffraction and H2-temperature-programmed reduction methods. The catalytic properties of the catalysts were tested in isobutane dehydrogenation reaction. It was shown that the state of chromium on the surface is different over different supports. For the CrOx/CeO2 catalyst, the formation of Cr2O3 particles with low activity in the dehydrogenation reaction was observed. For other samples, a highly disperse X-ray amorphous state of chromium was characteristic. The catalyst based on CexZr(1–x)O2 was the most active in isobutane dehydrogenation reaction due to possible stabilization of chromium as Cr(V) state.
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Odioso et al.
, p. 209,211 (1961)
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Petrow
, (1954)
Jones
, p. 1877 (1938)
METHOD FOR DEHYDRATING ALCOHOLS TO OBTAIN OLEFINS, INVOLVING A STEP OF CATALYST SELECTIVATION
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Paragraph 0055-0077, (2021/03/19)
The invention relates to a process for dehydrating alcohols to olefins, comprising a reaction step and a catalyst selectivation step.
Insights into the doping effect of rare-earth metal on ZnAl2O4 supported PtSn catalyzed isobutane dehydrogenation
Liu, Jianfeng,Zhou, Wei,Jiang, Dongyu,Wang, Dong,Wu, Wenhai,Wang, Yue,Ma, Xinbin
, p. 58 - 65 (2020/04/27)
Isobutane dehydrogenation is a vital route for the production of isobutene, an important substance for methyl tert-butyl ether. However, the reaction is typically performed at relatively low pressure and high temperature, resulting in a facilitated coke formation. Here, we used rare-earth metals (Y, La, Ce) as dopants to modify the ZnAl2O4 support and studied their effects on Pt-Sn catalyzed dehydrogenation of isobutane. Combining the experimental and theoretical results, it is demonstrated that while Y and La tend to incorporate into the matrix of ZnAl2O4, separate CeO2 phase could be easily formed on ZnAl2O4 surface, leading to a decrease in both amount and strength of the Lewis acid sites. And for the La-ZnAl2O4, because of the large local deformation, oxygen vacancy can be readily formed, and results in a lot acid sites in the subsurface layer available for reactions. Deactivation rates of the catalysts in isobutane dehydrogenation is found to linearly correlate with the Lewis acid amounts over the modified supports. Compared with the catalysts of Pt-Sn/ZnAl2O4, Pt-Sn/La-ZnAl2O4 and Pt-Sn/Y-ZnAl2O4, Pt-Sn/Ce-ZnAl2O4 exhibits superior catalytic performance due to the low coke contents and high Pt dispersion. These results may provide additional insights on the design and optimization of isobutane dehydrogenation catalysts by tailoring the composition and structure of oxide supports.
Synthesis and catalytic application of nanorod-like FER-type zeolites
Dai, Weijiong,Deng, Xin,Guan, Naijia,Li, Landong,Ruaux, Valérie,Tai, Wenshu,Valtchev, Valentin,Wu, Guangjun
, p. 24922 - 24931 (2021/11/27)
Nanosize dimensions have an important impact on zeolite properties and catalytic performance in particular. Herein, we develop a direct synthesis route to obtain a nanosized nanorod-like ferrierite (FER) zeolite with the assistance of ammonium fluoride (NH4F) and employing a conventional structure-directing agent (pyrrolidine). The resultant nanorod-like FER zeolite crystals exhibit a greatly reduced diffusion path along the c-axis. The physicochemical properties of nanorod-like FER and its conventional micronsized plate-like counterpart were analyzed by N2 adsorption-desorption, 27Al, 1H, 29Si MAS NMR, NH3-TPD, and in situ D3-acetonitrile and pyridine adsorption followed by FTIR. The nanorod-like FER zeolite possesses superior characteristics in terms of a larger external area, better accessibility to the acid sites, and a larger number of pore mouths per unit crystal surface than the micron-sized counterpart synthesized without NH4F. The improved properties provide the nanorod-like FER zeolite with high selectivity and low deactivation rates in 1-butene skeletal isomerization. The thermogravimetry analysis (TGA) of the coke amounts revealed a better capability of coke tolerance of the nanorod-like FER zeolite. The in situ ultraviolet-visible (UV/Vis) and Fourier transform infrared spectroscopy (FTIR) spectroscopy investigations of the organic intermediates formed on FER zeolite catalysts during the catalytic reaction further verified the enhanced catalytic activity and stability of the nanorod-like FER zeolite.
