74-93-1Relevant articles and documents
New method of dimethyl sulfi de synthesis
Mashkina
, p. 678 - 681 (2011)
The synthesis of dimethyl sulfide consists in the reaction of dimethyl disulfide with methanol in the presence of solid catalyst, aluminum γ-oxide. The yield of dimethyl sulfide grows with growing temperature, contact time, and content of methanol in the reaction mixture. At 350-400°C, molar ratio methanol-dimethyldisulfide 2.0-2.5, and total conversion of the reagents the yield of dimethyl sulfide reached 95 mol%. Pleiades Publishing, Ltd., 2011.
Catalytic synthesis of methanethiol from methanol and carbon disulfide over KW/Al2O3 catalysts
Wang, Weiming,Li, Yang,Zhang, Xiang,Fang, Weiping,Yang, Yiquan
, p. 104 - 108 (2015)
Abstract A series of KW/γ-Al2O3 catalysts with varying K/W mole ratio were prepared for the synthesis of methanethiol from carbon disulfide and methanol, and characterized by N2 adsorption-desorption, XRD and NH3/CO2-TPD techniques. Experimental results showed that the acidic and basic property of the catalyst plays a key role on the catalytic performance. It is shown that the conversion of CH3OH is chiefly related to the acid sites, while the base sites of catalysts are favorable for the selectivity toward CH3SH and hydrocarbons, but the strong base sites will restrain the selectivity toward CH3SH. When the K/W mole ratio is K/W = 2/1 and the reaction temperature is at 603 K, the conversion of CH3OH and the selectivity toward CH3SH are 98.3 and 56.2%, respectively.
Pre-steady-state kinetic and structural analysis of interaction of methionine γ-lyase from Citrobacter freundii with inhibitors
Kuznetsov, Nikita A.,Faleev, Nicolai G.,Kuznetsova, Alexandra A.,Morozova, Elena A.,Revtovich, Svetlana V.,Anufrieva, Natalya V.,Nikulin, Alexei D.,Fedorova, Olga S.,Demidkina, Tatyana V.
, p. 671 - 681 (2015)
Methionine γ-lyase (MGL) catalyzes the γ-elimination of L-methionine and its derivatives as well as the β-elimination of L-cysteine and its analogs. These reactions yield α-keto acids and thiols. The mechanism of chemical conversion of amino acids includes numerous reaction intermediates.The detailed analysis of MGL interaction with glycine, L-alanine, L-norvaline, and L-cycloserine was performed by pre-steady-state stopped-flow kinetics. The structure of side chains of the amino acids is important both for their binding with enzyme and for the stability of the external aldimine and ketimine intermediates. X-ray structure of the MGL·L-cycloserine complex has been solved at 1.6 A? resolution. The structure models the ketimine intermediate of physiological reaction. The results elucidate the mechanisms of the intermediate interconversion at the stages of external aldimine and ketimine formation.
Development of a Continuous Flow Sulfoxide Imidation Protocol Using Azide Sources under Superacidic Conditions
Gutmann, Bernhard,Elsner, Petteri,O'Kearney-Mcmullan, Anne,Goundry, William,Roberge, Dominique M.,Kappe, C. Oliver
, p. 1062 - 1067 (2015)
The development of a continuous flow sulfoxide imidation protocol for a pharmaceutically relevant target molecule is described. Sulfoxide imidation is a key step in the preparation of certain ATR kinase inhibitors. Reactions with NaN3 or TMSN3 and concentrated sulfuric acid under literature conditions provided low conversions and poor selectivities. In contrast, reactions employing fuming sulfuric acid afforded the target sulfoximine with a selectivity of ～90% after a reaction time of only 10-15 min at 50 °C. The imidation reaction using TMSN3 as reagent was successfully performed in a flow reactor utilizing CH2Cl2/H2SO4 biphasic conditions. The mixture was subsequently quenched in-line with H2O. Phase separation, neutralization, and re-extraction with an organic solvent furnished the product in excellent purity and good yields, albeit with loss of chirality.
Reactions of α-isobutyl-α-(methylthio)methylene Meldrum's acid with primary amines in aqueous DMSO
Biswas, Supriya,Ali, Mahammad,Rappoport, Zvi,Salim, Hatim
, p. 1678 - 1685 (2006)
The aminolysis of α-isobutyl-α-(methylthio)methylene Meldrum's acid 7 with primary amines, namely, n-butylamine, glycinamide, and methoxyethylamine in DMSO-H2O (50:50, v/v) at 20°C is overall second-order but first-order in both 7 and amines. The reaction with aminoacetonitrile (AA) is overall third-order, first-order in substrate, and second-order in amine at low amine concentration, while at high amine concentration and high pH the dependence on amine is first-order. A general three-step mechanism has been proposed for all these reactions. For the former group of amines, the first step is a rate-limiting attack of the amine to form the tetrahedral intermediate (TA±), followed by a fast acid-base equilibrium and a fast RNH3+- or H 2O-assisted leaving group expulsion. For AA, general base catalysis was confirmed from the dependence of kA on [AA]f and on [OH-]. For all four amines, a good Bronsted plot of log k 1 vs. pKaAH in DMSO-H2O (50:50, v/v) with βnuc = 0.34 ± 0.02 was observed. These observations are consistent with the suggested mechanism.
Catalytic synthesis of methanethiol from CO/H2/H2S mixtures using α-Al2O3
Zhang, Baojian,Taylor, Stuart H.,Hutchings, Graham J.
, p. 471 - 476 (2004)
Sustained synthesis of methanethiol from the reaction of CO/H 2/H2S mixtures is reported and discussed. Surprisingly, unmodified α-Al2O3 gives the best results for this reaction and methanethiol selectivities of > 98% at CO conversions of ca. 6% can be readily obtained (CO:H2:H2S = 4:5:1, 340°C, total pressure = 20 bar, 200 h-1). Reaction of CO+ H2 (CO:H2 = 1:1) in the absence of H2S using α-Al 2O3 under comparable conditions gives a lower CO conversion (ca. 1.3%) with significant selectivities to methane (20%), methanol (28.5%) and ethanol (21.1%). When H2S is added to the synthesis gas feedstock, the product selectivity switches to sulfur-containing products, almost exclusively methanethiol, but some by-product thiophene is also observed. A range of other catalysts were also investigated (e.g., γ-Al 2O3, Cr2O3, Cr2O 3/Al2O3, Cu/Cr2O3) but all give inferior catalytic performance when compared with α-Al 2O3. The mechanism of the synthesis of methanethiol is discussed, based on a modification of chain propagation in the Fischer-Tropsch synthesis reaction.
Activity of zeolites in dimethyl sulfide synthesis
Mashkina,Khairulina
, p. 579 - 583 (2010)
Dimethyl disulfide conversion into dimethyl sulfide over various zeolites in an inert medium at atmospheric pressure and T = 190-330°C is reported. A significant activity in dimethyl sulfide formation is shown by the decationized zeolites HNaY and HZSM-5, whose surface has strong protonic and nonprotonic acid sites. Cobalt-containing faujasite is more active than HNaY, and the activity of CoHZSM-5 is comparable with the activity of its decationized counterpart.
Metal Oxides as Catalysts for the Reaction between Methanol and Hydrogen Sulfide
Ziolek, M.,Kujawa, J.,Saur, O.,LaValley, J. C.
, p. 9761 - 9766 (1993)
The reaction between methanol and hydrogen sulfide leading to the formation of methanethiol and dimethyl sulfide has been studied using different H2S:CH3OH molar ratios (0.5:1, 1:1, 2:1) at 623 K on various metal oxides presenting different acidity and basicity.The correlations between activity and selectivity of catalysts and their average oxygen and cation charges as well as the strength of their acidic and basic sites, determined by adsorption of probe molecules followed by IR spectroscopy, are as follows: (i) the highest strenth of basic sites and the highest negative charge on oxygen (MgO) lead to the lowest activity and the highest selectivity toward CH3SH; (ii) the lowest strength of basic sites (medium oxygen charge) and the highest cation charge (γ-Al2O3) cause the highest activity and the highest selectivity toward (CH3)2S.The dimethyl sulfide selectivity is in the reverse order of the number of basic sites.IR measurements show that the reaction occurs between chemisorbed methanol (methoxy species) and SH(1-) species or/and H2S molecules.Too strongly held methoxy species as on MgO and PO4(3-)/SiO2 do not react with H2S.The difference in activity and selectivity of both titania samples (anatase and rutile) is discussed.
Thiolation behaviors of methanol catalyzed by bifunctional ZSM-5@t-ZrO2 catalyst
Cao, Jianxin,Kawi, Sibudjing,Liu, Fei,Pei, Lijie,Wang, Xiaodan,Yang, Anjie,Yao, Mengqin,Zhao, Tianxiang
, (2021/08/26)
The catalytic properties of bifunctional ZSM-5@t-ZrO2 catalyst for methanol thiolation were revealed by using methanol and H2S as probe molecules. Taking the ZSM-5/t-ZrO2 physically-blended catalyst, pure ZSM-5 and t-ZrO2 as control catalysts, we investigated the characteristics of adsorption and transformation of different reaction molecules on or over different catalysts by combination of in-situ diffuse reflectance Fourier transform infrared spectroscopy (Drifts) and a variety of techniques including XRD, XPS, XRF, FT-IR, N2 adsorption-desorption, CO2/NH3-TPD, and DSC. The results showed that the synergistic effect of acid sites between ZSM-5 phase and t-ZrO2 phase in the bifunctional catalyst enhanced the adsorption and dissociation of methanol molecules, while the base sites in t-ZrO2 phase were mainly responsible for the adsorption and dissociation of H2S molecules. Due to the small specific surface area of pure t-ZrO2 catalyst, precursor species for sulfur deposition and carbon deposition were easily formed. Presulfurization could improve the initial activity of methanol thiolation and shorten the induction period. The dissociation of H2S at the base sites was the rate-determining step of the bimolecular reaction, and the appropriate increase of base sites in the bifunctional components could construct the matching formation rate of sulfhydryl and methoxy groups. At the same time, the special composite structure and meso-microporous system of ZSM-5@t-ZrO2 could effectively reduce the formation rate of carbon and sulfur deposits.
PROCESS FOR THE PREPARATION OF METHYL MERCAPTAN
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Paragraph 0058-0060, (2020/11/30)
The invention relates to a process for preparing methyl mercaptan from a mixture of carbon oxide, hydrogen sulfide and hydrogen, in the presence of a catalyst based on molybdenum and potassium supported on zirconia, said catalyst not comprising any promoter.
