106-99-0Relevant articles and documents
The e- + 1,3-Butadiene 1,3-Butadiene- Equilibrium in n-Hexane
Holroyd, Richard A.,Schwarz, Harold A.,Stradowska, Elizabeth,Ninomiya, Shiro,Itoh, Kengo,Nishikawa, Masaru
, p. 7142 - 7146 (1994)
The rate constants for attachment of excess electrons to 1,3-butadiene (ka) and detachment from the butadiene anoin (kd) in n-hexane are reported.The equilibrium constant, Keq = ka/kd, increases rapidly with pressure and decreases as the temperature increases.At -7 deg C attachment is observed at 1 bar.At high pressures the attachment rate is diffusion controlled.The activation energy for detachment is about 21 kcal/mol; detachment is facilitated by the large entropy of activation.The reaction volumes for attachment range from -181 cm3/mol at 400 bar to -122 cm3/mol at 1500 bar and are largely attributed to the electrostriction volume of the butadiene anion (Δel).Values of Δel) calculated by a model, which includes a glassy shell of solvent molecules around the ion, are in agreement with experimental reaction volumes.The analysis indicates the partial molar volume of the electron in hexane is small and probably negative.It is shown that the entropies of reaction are closely related to the partial molar volumes of reaction.
Preadsorbed oxygen atoms affect the product distribution and kinetics of acetylene cyclization to benzene on Pd(111): A laser-induced thermal desorption/fourier transform mass spectrometry study
Caldwell, Tracy E.,Abdelrehim, Ihab M.,Land, Donald P.
, p. 562 - 568 (1998)
The study presented here focuses on determining the role of oxygen as a modifier on Pd(111) and its effects on the cyclization of acetylene to benzene. Laser-induced thermal desorption/Fourier transform mass spectrometry (LITD/FTMS) is used as a sensitive tool for measuring the in situ kinetics of benzene formation from acetylene on O/Pd(111). Low exposure of acetylene on O/Pd(111) leads to the anticipated formation of benzene and 1,3-butadiene. Though there is no evidence of furan formation on the surface, oxidation products, such as CO and H2O, are observed. An enhancement in the yield of benzene has been observed with increasing oxygen preexposure. Our evidence suggests that this enhancement is caused by oxygen-island compression of acetylene molecules into bare patches of Pd, which effectively increases the local coverage of acetylene in those regions. Isothermal kinetic studies of 1.1 langmuirs of acetylene on a 50% saturated layer of O on Pd(111) (from a 0.25 langmuir exposure of O2 at 250 K) yield an Ea of 37.8 ± 3 kJ/mol using initial rates (and 36.2 ± 3 kJ/mol using a pseudo-first-order model). Both the activation energy and preexponential factor from a 50% saturation coverage of oxygen on Pd(111) correspond to the values expected for twice the acetylene exposure on a clean surface. The apparent contradiction between increased benzene yields and activation barrier for the O/Pd system can be rationalized by the compensation effect, where a more tightly bound reactant can lead to a greater entropy of activation.
Hydrocarbon Activation by Gas-Phase Lanthanide Cations: Interaction of Pr+, Eu+, and Gd+ with Small Alkanes, Cycloalkanes, and Alkenes
Schilling, J. Bruce,Beauchamp, J. L.
, p. 15 - 24 (1988)
We describe ion beam studies of the interaction of gas-phase lanthanide ions, praseodymium (Pr+), europium (Eu+), and gadolinium (Gd+), with small alkanes, cycloalkanes, alkenes, and several oxygen-containing compounds.Only Gd+ is seen to activate C-H and C-C bonds of alkanes.The ground-state electronic configuration of Gd+ (4f75d16s1) is different from those of Pr+ (4f36s1) and Eu+ (4f76s1), leading to the conclusion that the f electrons play little part in the metal ion reactivity.Gd+ can be thought of as having two valence electrons, and indeed it reacts similarly to Sc+ and the other group 3 metal ions Y+ and La+, yielding products corresponding to elimination of hydrogen, alkanes, and alkenes.The elimination of neutral alkenes in the reaction of Gd+ with alkanes results in the formation of metal dialkyl or hydrido-alkyl complexes.This finding leads to estimates for the sum of two Gd+ ? bond dissociation energies of between 110 and 130 kcal/mol.Gd+ and Pr+ react readily with alkenes, yielding mostly dehydrogenation products along with smaller amounts of C-C bond cleavage products.Reactions of Gd+ and Pr+ with oxyen-containing species such as nitric oxide, formaldehyde, acetaldehyde, and acetone yield primarily the metal oxide ions and provide a lower limit for D(M+-O) of 179 kcal/mol, in good agreement with literature values of D(Pr+-O) = 188.4 +/- 5.2 kcal/mol and D(Gd+-O) = 181.0 +/- 4.4 kcal/mol.In keeping with the strong metal ? bonds, Gd+ is also seen to readily react with formaldehyde to eliminate CO and form GdH2+.
Effect of CH2Br2-Addition upon Direct Oxidative Dehydrogenation of Butane into 1,3-Butadiene over Fe-Sb-O Composite Catalyst
Saitoh, Hitoshi,Satoh, Satoshi,Sodesawa, Toshiaki,Nozaki, Fumio
, p. 3649 - 3650 (1986)
Effect of CH2Br2-addition upon direct oxidative dehydrogenation of butane into 1,3-butadiene has been investigated in a conventional flow apparatus.The activity and selectivity of Fe-Sb-O catalyst were much improved by the addition of CH2Br2 to butane in the mole ratio, CH2Br2/n-C4H10, of 0.03 to 0.10 at temperatures near 450 deg C.
Tin-Assisted Fully Exposed Platinum Clusters Stabilized on Defect-Rich Graphene for Dehydrogenation Reaction
Zhang, Jiayun,Deng, Yuchen,Cai, Xiangbin,Chen, Yunlei,Peng, Mi,Jia, Zhimin,Jiang, Zheng,Ren, Pengju,Yao, Siyu,Xie, Jinglin,Xiao, Dequan,Wen, Xiaodong,Wang, Ning,Liu, Hongyang,Ma, Ding
, p. 5998 - 6005 (2019)
Tin-assisted fully exposed Pt clusters are fabricated on the core-shell nanodiamond@graphene (ND@G) hybrid support (a-PtSn/ND@G). The obtained atomically dispersed Pt clusters, with an average Pt atom number of 3, were anchored over the ND@G support by the assistance of Sn atoms as a partition agent and through the Pt-C bond between Pt clusters and defect-rich graphene nanoshell. The atomically dispersed Pt clusters guaranteed a full metal availability to the reactants, a high thermal stability, and an optimized adsorption/desorption behavior. It inhibits the side reactions and enhances catalytic performance in direct dehydrogenation of n-butane at a low temperature of 450 °C, leading to >98% selectivity toward olefin products, and the turnover frequency (TOF) of a-PtSn/ND@G is ～3.9 times higher than that of the traditional Pt3Sn alloy catalyst supported on Al2O3 (Pt3Sn/Al2O3).
Decomposition of 2-methylfuran. Experimental and modeling study
Lifshitz,Tamburu,Shashua
, p. 1018 - 1029 (1997)
The thermal reactions of 2-methylfuran were studied behind reflected shock waves in a pressurized driver single pulse shock tube over the temperature range 1100-1400 K and with overall densities of approx. 3 × 10-5 mol/cm3. A large number of products resulting from unimolecular cleavage of the ring and consecutive free radical reactions were obtained under shock heating. The unimolecular decomposition is initiated by two parallel channels: (1) 1,2-hydrogen atom migration from C(5) to C(4) and (2) a methyl group migration from C(2) to C(3) in the ring. Each channel is followed by two parallel modes of ring cleavage. In the first channel, breaking the O - C(2) and the C(4) - C(5) bonds in the ring yields CO and different isomers of C4H6, whereas breaking of the O - C(2) and the C(3) - C(4) bonds yields CH2CO and two isomers C3H4. In the second channel, breaking the O - C(5), and C(2) - C(3) bonds in the ring yields again CO and isomers of C4H6, whereas in the second mode O - C(5), C(2) - C(3), and C(3) - C(4) are broken to yield CO, C2H2, and C2H4. The four C4H6 isomers in decreasing order of abundance were 1,3-butadiene, 1-butyne, 1,2-butadiene, and 2-butyne. The major decomposition product is carbon monoxide. The rate constant for its overall formation is estimated to be kCO = 1015.88 exp(-78.3 × 103/RT) s-1, where R is expressed in units of cal/(K mol). Other products that were found in the postshock samples in decreasing order of abundance were C4H4, C2H2, CH4, p-C3H4, C2H6, C2H4, a-C3H4, C6H6, C4H4O, C3H6, and C4H2. The total decomposition of 2-methylfuran in terms of a first order rate constant is given by ktotal = 1014.78 exp(-71.8 × 103/RT) s-1. This rate and the production rate of carbon monoxide are slightly higher than the ones found in the decomposition of furan. An oxygen-carbon mass balance among the decomposition products was obtained. A reaction scheme composed of 36 species and some 100 elementary reactions accounts for the product distribution over the temperature range covered in this study. First order Arrhenius rate parameters for the formation of the various reaction products are given, a reaction scheme is suggested, and results of computer simulation and sensitivity analysis are shown. Differences and similarities in the reactions of furan and 2-methylfuran are discussed.
IR laser-induced thermolysis of silacyclopent-3-ene: Extrusion of silylene and chemical vapour deposition of polycarbosilane phases via reactions of silylene, buta-1,3-diene and methylene
Pola, Josef,Urbanová, Markéta,Díaz, Luis,Santos, Magna,Bastl, Zdenek,?ubrt, Jan
, p. 202 - 208 (2000)
Infrared laser-induced (SF6) photosensitized decomposition and infrared laser multiphoton decomposition of silacyclopent-3-ene occur as extrusion of silylene, yielding butadiene as a major gaseous product and affording chemical vapour deposition of solid saturated polycarbosilane films. The involvement of H2Si:, H2C: and buta-1,3-diene in the formation of the films is revealed through quantification of the gaseous products and identification of H2Si: and H2C: by laser induced fluorescence.
Ion and radical rearrangements as a probe of the mechanism of a surface reaction : The desulfurization of cyclopropylmethanethiol and 3-butene-1-thiol on Mo(110)
Wiegand,Napier,Friend,Uvdal
, p. 2962 - 2968 (1996)
Rearrangement reactions were used to probe the transient intermediates in thiol desulfurization induced by Mo(110) by studying cyclopropylmethanethiol and 3-butene-1-thiol. Thiolate intermediates were identified in both cases using vibrational spectroscopy, which indicates facile S-H bond scission on Mo(110). Heterolytic C-S bond scission, leading to a cationic intermediate, is excluded based on the lack of rearrangement products in the reactions of 3-butene-1-thiolate and the absence of cyclobutane or cyclobutene in the reaction of cyclopropylmethyl thiolate on Mo(110). Hydrogenolysis without rearrangement is the primary pathway for both thiols investigated. The lack of rearrangement in the 3-butene-1-thiolate indicates that C-S bond scission and C-H bond formation occur nearly simultaneously. Evidence for the radical pathway is obtained from the production of 1,3-butadiene formed via the rearrangement of cyclopropylmethyl group following C-S bond scission in the cyclopropylmethyl thiolate and by related studies of cyclopropylmethyl bromide. The investigation of the cyclopropylmethyl bromide also demonstrates that trapping of the cyclopropylmethyl radical is favored over selective β-dehydrogenation. This is the first study in which radical rearrangements have been used to obtain detailed information about the nature of extremely short-lived reactions in a surface process.
ZnTa-TUD-1 as an easily prepared, highly efficient catalyst for the selective conversion of ethanol to 1,3-butadiene
Pomalaza,Vofo,Capron,Dumeignil
, p. 3203 - 3209 (2018)
High performances in the conversion of ethanol to 1,3-butadiene were achieved with a Zn(ii) and Ta(v) catalyst supported on TUD-1, a mesoporous silica. The selectivity reached 73% after 3 h at 94% conversion. At an increased ethanol flow, the initial productivity increased to 2.45 g1,3-BD gcat-1 h-1, which remained stable for 60 h on stream, making it the most productive catalyst according to the literature. Preliminary characterization suggests that its morphological and acid properties contribute to these exceptional performances.
Vacuum-Ultraviolet (147.0 and 123.6 nm) Photolysis of trans- and cis-1,2-Dimethylcyclopropanes
Pendleton, Tanis S.,Kaplan, Michael,Doepker, Richard D.
, p. 472 - 476 (1980)
The photochemical decompositions of trans- and cis-1,2-dimethylcyclopropanes were investigated at 147.0 and 123.6 nm with standard rare gas resonance lamps.The observed products in the scavenged photolysis system were hydrogen, propylene, acetylene, ethylene, 1,3-butadiene, trans- or cis-2-butenes, pentadienes, allene, methylacetylene, and 1,2-butadiene, listed in decreasing importance.Quantum yields for each of the products were determined in experiments performed in both the presence and the absence of additives.Nitric oxide and oxygen were employed as radical scavengers, whereas hydrogen sulfide and hydrogen iodide were used as radical interceptors.Four radical species were identified and quantified, including methyl, vinyl, allyl, and a mixed C4H7 system.In both systems, ten primary processes have been proposed and the quantum efficiencies assigned for each primary reaction channel.The quantum efficiency for the methylene elimination channel ranged between 0.07 to 0.10 for both systems at both wavelengths. trans-1,2-Dimethylcyclopropane led exclusively to the trans-2-butene, whereas the cis- produced only the cis-2-butene.
