107-01-7Relevant articles and documents
Supramolecular origins of product selectivity for methanol-to-olefin catalysis on HSAPO-34
Song,Fu,Haw
, p. 4749 - 4754 (2001)
Ethylene selectivity in methanol-to-olefin (MTO) catalysis is related to the number of methyl groups on benzene rings trapped in the nanocages of the preferred catalyst HSAPO-34. By correlating the time evolutions of the catalysts' 13C NMR spectra and the volatile product distribution following abrupt cessation of methanol flow, we discovered that (in the absence of other adsorbates) propene is favored by methylbenzenes with four to six methyl groups but ethylene is predominant from those with two or three methyl groups. We substantially increased ethylene selectivity by operating at lower methanol partial pressures or higher temperatures, either of which reduces the steady-state average methyl substitution. As a step toward a kinetic analysis of the MTO reaction on HSAPO-34, we treated each nanocage with a methylbenzene molecule as a supramolecule capable of unimolecular dissociation into ethylene or propene and a less highly substituted methylbenzene. Addition of a water molecule to a nanocage containing a methylbenzene produces a distinct supramolecule with unique properties. Indeed, co-feeding water with methanol significantly increased the average number of methyl groups per ring at steady state relative to identical conditions without additional water, and also increased ethylene selectivity, apparently through transition state shape selectivity.
Amination of butenes over protonic zeolites
Lequitte,Figueras,Moreau,Hub
, p. 255 - 261 (1996)
The reaction of 1-butene and isobutene with ammonia has been investigated, far from thermodynamic equilibrium, in the pressure range 1-6 MPa over a series of acidic zeolites. The kinetics are compatible with a Langmuir-Hinshelwood mechanism involving adsorbed species. The rates of amination increase with the Si/Al ratio of the solid. A small influence of the zeolite structure is noticed on the relative adsorption coefficients in the case of 1-butene but not in that of isobutene. The catalytic activity calculated per proton is higher on MFI than on BEA or HY zeolites, but this effect of the structure is less than an order of magnitude. Under the conditions of reaction used in this work large pore zeolites show a good resistance to deactivation. It is proposed that deactivation is mainly due to the formation of strongly basic polyalkylamines and not to coke.
The Gas-Phase Elimination Kinetics of 2-Hydroxy-2-Methylbutyric Acid and 2-Ethyl-2-Hydroxybutyric Acid
Chuchani, Gabriel,Martin, Ignacio,Rotinov, Alexandra
, p. 849 - 854 (1995)
The elimination kinetics of the title compounds have been examined over the temperature range of 270 - 320 deg C and pressure range of 19 - 117 torr.The reactions, carried out in seasoned vessels, with the free-radical suppressor toluene always present, are homogeneous, unimolecular, and follow a first-order rate law.The products of 2-hydroxy-2-methylbutyric acid are 2-butanone, CO, and H2O; while of 2-ethyl-2-hydroxybutyric acid are 3-pentanone, CO, and H2O.The rate coeffcient is expressed by the following Arrhenius equation: for 2-hydroxy-2-methylbutyric acid, log k1(s-1) = (12.87 +/- 0.19) - (171.2 +/- 2.1) kJ mol-1 (2.303 RT)-1; and for 2-ethyl-2-hydroxybutyric acid, log k1(s-1) = (12.13 +/- 0.34) - (159.4 +/- 3.7) kJ mol-1 (2.303 RT)-1.Augmentation of alkyl bulkiness at the 2-position of the 2-hydroxycarboxylic acids showed an increase in the rate of dehydration.The electron release of alkyl groups, rather than steric acceleration, appears to enhance the pyrolysis decomposition of these substrates.These reactions are believed to proceed through a semi-polar five-membered cyclic transition type of mechanism.
Highly Selective MTO Reaction over a Nanosized ZSM-5 Zeolite Modified by Fe via the Low-Temperature Dielectric Barrier Discharge Plasma Method
Bai, Xuefeng,Bukina, Z. M.,Kolesnichenko, N. V.,Li, Yuzong,Maximov, A. L.,Su, Xiaofang,Wang, Wei,Wang, Yongchao,Wu, Wei
, p. 137 - 148 (2020)
Nanosized ZSM-5 zeolites were synthesized via in situ seed-induced hydrothermal method, and samples modified with an Fe promoter were prepared by the traditional wet impregnation-thermal decomposition and dielectric barrier discharge plasma (DBD) methods, respectively. The catalytic performance was studied by the methanol-to-olefin (MTO) reaction. The results showed that the acidity of the catalysts, the dispersity of the Fe promoter, and the interaction degree with the ZSM-5 zeolite are closely related to product selectivity in the MTO reaction. Compared with the Fe-NZ5 sample prepared by the traditional impregnation-calcination method, the FeD-NZ5 samples prepared by the DBD method demonstrated the higher selectivity of C2—C4 light olefins and the lower coke deposition during long-term evaluation (100 hr), which can be attributed to the weaker acid strength, more uniform Fe promoter dispersion, and strong interaction with the ZSM-5 zeolite.
Oxygen scrambling and stereochemistry during the trifluoroethanolysis of optically active 2-butyl 4-bromobenzenesulfonate
Dietze, Paul E.,Wojciechowski, Marek
, p. 5240 - 5244 (1990)
It is shown that during the trifluoroethanolysis of 2-butyl 4-bromobenzenesulfonate, containing 18O in the nonbridging oxygens, scrambling of the oxygen label occurs. When enantiomerically enriched 2-butyl 4-bromobenzenesulfonate is subjected to the same solvolysis conditions, racemization of the starting ester is not observed. Therefore if an ion-pair intermediate is involved in the trifluoroethanolysis reaction, the ion pair has a sufficient lifetime to permit rotation of the anion leading to oxygen scrambling. However, rotation of the cation, which would lead to racemization, does not occur. The possibility that the oxygen scrambling may be a concerted reaction and not involve an ion-pair intermediate is discussed.
TRANSFORMATION OF 1-BUTENE OVER SYNTHETIC ZEOLITES
Ferino, Italo,Monaci, Roberto,Solinas, Vincenzo,Forni, Lucio,Rivoldini, Antonio,Sanseverino, Luigi
, p. 869 - 881 (1992)
The behaviour of several zeolites as catalysts for the title reaction has been investigated by means of a continuous flow microreactor.Runs performed at atmospheric pressure indicated that at 423 K the completely protonic forms of the zeolites catalyze just the isomerization reaction.In the case of Y zeolites, oligomerization occures only over the partially decationated samples, in the temperature range between 373 and 423 K and W/F between 0.2 and 22 gcath/g1-but, to an extent which depends on the reaction conditions.Most of the catalysts were tested also under pressure (4.05 MPa) at 423 K.The protonic forms of Y and ZSM-5 zeolites seem promising catalysts in terms of both conversion and selectivity to oligomers.The 1-olefins account for 30percent of the entire olefinic mixture.The octenes, which account for 70percent of the liquid mixture, are mostly formed of dimethylhexenes.Trimers are also formed during the reaction and, in the very particular case of HZSM-5, tetramers are produced.
Thermal Decomposition of Allylic Sulfinic Acids: Confirmation of a Retro-ene Mechanism
King, Malcolm D.,Sue, Rodney E.,White, Rodney H.,Young, David J.
, p. 1797 - 1798 (1993)
The acidolysis of trialkyltin allylic sulfinates yields the corresponding sulfinic acids which undergo a first-order thermal decomposition with γ-syn substitution as predicted for a retro-ene mechanism.
INFLUENCE OF ETHYLENE ON THE HYDROGENATION OF CO OVER RUTHENIUM
Jordan, Deborah S.,Bell, Alexis T.
, p. 4797 - 4805 (1986)
The interactions of C2H4 with H2 and CO were investigated over a SiO2-supported Ru catalyst.To differentiate carbon sources, 13C-labeled CO and unlabeled C2H4 were used.Product analysis was carried out by isotope-ratio gas chromatography/mass spectrometry.In the absence of CO, C2H4 undergoes extensive hydrogenation.Small amounts of CH4 and C3+ olefins and paraffins are also observed, indicative of C2H4 hydrogenolysis and homologation.The presence of CO strongly suppresses C2H4 hydrogenolysis, but enhances C2H4 homologation.The hydrogenation of CO hydrocarbons is strongly influenced by the presence of C2H4.With increasing C2H4 partial pressure, the hydrogenation of CO to hydrocarbons is progressively suppressed, but the hydroformylation of C2H4 to form propanal (and some 1-propanol) is enhanced.The product distributions observed for the reactions of C2H4 and H2, and C2H4, CO, and H2, can be described in terms of a chain growth mechanism involving C1 and C2 monomer units.
Olefin oligomerization via new and efficient Br?nsted acidic ionic liquid catalyst systems
Wang, Guoqin,Song, Heyuan,Li, Ruiyun,Li, Zhen,Chen, Jing
, p. 1110 - 1120 (2018)
Olefin oligomerization reaction catalyzed by new catalyst systems (a Br?nsted-acidic ionic liquid as the main catalyst and tricaprylylmethylammonium chloride as the co-catalyst) has been investigated. The synthesized Br?nsted acidic ionic liquids were characterized by Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV), 1H nuclear magnetic resonance (NMR), and 13C NMR to analyze their structures and acidities. The influence of different ionic liquids, ionic liquid loading, different co-catalysts, catalyst ratios (mole ratio of ionic liquid to co-catalyst), reaction time, pressure, temperature, solvent, source of reactants, and the recycling of catalyst systems was studied. Among the synthesized ionic liquids, 1-(4-sulfonic acid)butyl-3-hexylimidazolium hydrogen sulfate ([HIMBs]HSO4) exhibited the best catalytic activity under the tested reaction conditions. The conversion of isobutene and selectivity of trimers were 83.21% and 35.80%, respectively, at the optimum reaction conditions. Furthermore, the catalyst system can be easily separated and reused; a feasible reaction mechanism is proposed on the basis of the distribution of experimental products.
Kinetics and mechanism of the homogeneous oxidation of n-butenes to methyl ethyl ketone in a solution of mo-v-phosphoric heteropoly acid in the presence of palladium pyridine-2,6-dicarboxylate
Odyakov,Zhizhina
, p. 828 - 834 (2011)
In catalytic two-step n-butene oxidation with dioxygen to methyl ethyl ketone, the first step is the oxidation of n-C4H8 with an aqueous solution of Mo-V-P heteropoly acid in the presence of Pd(II) complexes. The kinetics of n-butene oxidation with solutions of H7PV 4Mo8O40 (HPA-4) in the presence of the Pd(II) dipicolinate complex (H2O)PdII(dipic) (I), where dipic2- is the tridentate ligand 2,6-NC5H3(COO-)2, is studied. Calculation shows that, at the ratio dipic2- : Pd(II) = 1 : 1, the ligand decreases the redox potential of the Pd(II)/Pdmet system from 0.92 to 0.73-0.77, due to which Pd(II) is stabilized in reduced solutions of HPA-4. The reaction is first-order with respect to n-C4H8. Its order with respect to Pd(II) is slightly below unity, and its order with respect to HPA-4 is relatively low (~0.63). The activation energy of but-1-ene oxidation in the temperature range from 40 to 80°C is 49.0 kJ/mol, and that of the oxidation of but-2-ene is 55.6 kJ/mol. The mechanism of the reaction involving the cis-diaqua complex [(H2O)2PdII(Hdipic)] +, which forms reversibly from complex I, is proposed. The reaction rate is shown to increase with an increase in the HPA-4 concentration due to an increase in the acidity of the solution. Pleiades Publishing, Ltd., 2011.
