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.
General Synthesis of Ordered Mesoporous Carbonaceous Hybrid Nanostructures with Molecularly Dispersed Polyoxometallates
Chen, Chunhong,Fan, Zhanxi,Ge, Yiyao,Ma, Qinglang,Mao, Shanjun,Qi, Guodong,Tan, Chaoliang,Wang, Yong,Wang, Zhe,Xu, Jun,Zhang, Xiao
, p. 15556 - 15562 (2021)
Hybrid nanomaterials with controlled dimensions, intriguing components and ordered structures have attracted significant attention in nanoscience and technology. Herein, we report a facile and green polyoxometallate (POM)-assisted hydrothermal carbonization strategy for synthesis of carbonaceous hybrid nanomaterials with molecularly dispersed POMs and ordered mesopores. By using various polyoxometallates such as ammonium phosphomolybdate, silicotungstic acid, and phosphotungstic acid, our approach can be generalized to synthesize ordered mesoporous hybrid nanostructures with diverse compositions and morphologies (nanosheet-assembled hierarchical architectures, nanospheres, and nanorods). Moreover, the ordered mesoporous nanosheet-assembled hierarchical hybrids with molecularly dispersed POMs exhibit remarkable catalytic activity toward the dehydration of tert-butanol with the high isobutene selectivity (100 %) and long-term catalytic durability (80 h).
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.
Designing ferrierite-based catalysts with improved properties for skeletal isomerization of n -butene to isobutene
Hu, Haiqiang,Ke, Ming,Zhang, Ka,Liu, Qiang,Yu, Pei,Liu, Yang,Li, Changchun,Liu, Wen
, p. 31535 - 31543 (2017)
The crystal morphology and size of ferrierite catalysts were controlled by a suite of crystallization methods and structure-directing agents. In particular, nano-sized ferrierite could be obtained by using tetramethylammonium hydroxide and pyrrolidine as double structure-directing agents under dynamic crystallization. The catalysts were analysed by XRD, SEM, N2 adsorption-desorption, NMR, XRF, NH3-TPD, Py-IR, and TGA, and the characteristics were correlated with their catalytic performance in the skeletal isomerization of n-butene. The results clearly indicated that all the catalysts have a similar crystallinity, Si/Al ratio, and total number of acid sites, while a decrease in their crystal size leads to more pore mouth acid sites. The nano-sized ferrierite showed better stability and higher activity, which were related to their crystal morphology, size, and pore mouth acid. In addition, we further confirmed that high isobutene selectivity can be produced by monomolecular 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.
Catalytic Behavior of Pt/SbOx for Selective Oxidation of i-C4H10 and i-C4H8 in Stationary and Nonstationary Conditions
Inoue, Tomoya,Asakura, Kiyotaka,Iwasawa, Yasuhiro
, p. 184 - 190 (1997)
It was found that Pt/SbOx catalysts were active for the selective oxidation of i-C4H10 and i-C4H8 to methacrolein (MAL) at 773 K. The SbOx itself was inactive for the selective oxidation of i-C4H10, while i-C4H8 was converted to MAL on the SbOx. Small amounts of Pt (0.2-0.72 wt%) supported on the SbOx promoted the i-C4H10 oxidation with good selectivity to MAL (typically 50-60%) and MAL+i-C4H8 (80-90%). The selective oxidation of i-C4H8 to MAL was also markedly enhanced by Pt. The performance of Pt/SbOx catalysts for the i-C4H10 selective oxidation may be attributed to combinative catalysis of Pt particles modified with SbOy (y 6O13 produced under the oxidation conditions.
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.
Isobutane Dehydrogenation Assisted by CO2 over Silicalite-1-Supported ZnO Catalysts: Influence of Support Crystallite Size
Luo, Yajun,Wei, Chunling,Miao, Changxi,Yue, Yinghong,Hua, Weiming,Gao, Zi
, p. 703 - 708 (2020)
The ZnO catalysts supported on Silicalite-1 zeolites with different crystallite sizes (0.08, 0.35, 1 and 1.7 μm, respectively) and 5% Zn were synthesized via an incipient wetness method. The catalysts were characterized by XRD, N2 adsorption, SEM, TEM-EDX, DRIFT spectra and NH3-TPD, and their catalytic performance in isobutane dehydrogenation assisted by CO2 was investigated. The catalytic activity is strongly dependent on the crystallite size of Silicalite-1 support. The ZnO/S-1-0.35 catalyst with ca. 0.35 μm crystallite size displays the highest activity, affording an initial isobutane conversion of 51.0% and 74.5% isobutene selectivity. This can be attributed to a higher amount of acid sites present on this catalyst as well as the largest amount of nest silanols possessed by the S-1-0.35 support.
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.
Kinetic scheme of homogeneous acid-catalyzed transformation of isopentenols
Ryabova, R. S.,Osipova, G. F.,Travin, S. O.
, p. 840 - 843 (1995)
The reactions occurring in an equilibrium mixture of 3-methyl-1-buten-3-ol and 3-methyl-2-buten-1-ol in 24-49 percent aqueous solutions of H2SO4 yield isoprene, 3-methyl-3-buten-1-ol, isobutylene, formaldehyde, 3-methylbutane-1,3-diol.Isobutylene is rapidly hydrated to give 2-methylpropan-2-ol.The presence of formaldehyde in the reaction mixture indicates that the transformations involve the reverse Prins reaction.On the basis of experimental and literature data, two most probable reactions were suggested.
