Synthesis of dimethyl sulfide in the presence of zeolites

In the presence of zeolites, dimethyl sulfide is produced either through CH₃OH interaction with H₂S or via CH₃SH decomposition. In accordance with their activities, in both reactions, zeolites arrange in the same sequence: HZSMHNaY>NaXNaY. Realization of the reaction CH₃OH+H₂S is more difficult compared to methanethiol decomposition.

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CH₃OH H₂S CH₃SH. : HZSMHNaY>NaXNaY. CH₃OH+H₂S , .

     

Hydrogenolysis of dimethyl disulfide in the presence of bimetallic sulfide catalysts

The hydrogenolysis of dimethyl disulfide in the presence of Ni,Mo and Co,Mo bimetallic sulfide catalysts was studied at atmospheric pressure and T = 160–400°C. At T ≤ 200°C, dimethyl disulfide undergoes hydrogenolysis at the S-S bond, yielding methanethiol in 95–100% yield. The selectivity of the reaction decreases with increasing residence time and temperature due to methanethiol undergoing condensation to dimethyl disulfide and hydrogenolysis at the C-S bond to yield methane and hydrogen sulfide. The specific activity of the Co,Mo/Al₂O₃ catalyst in hydrogenolysis at the S-S and C-S bonds is equal to or lower than the total activity of the monometallic catalysts. The Ni,Mo/Al₂O₃ catalyst is twice as active as the Ni/Al₂O₃ + Mo/Al₂O₃ or the cobalt-molybdenum bimetallic catalyst.     

Dimethyl disulfide conversion into dimethyl sulfide in the presence of sulfidized catalysts

The conversion of dimethyl disulfide in the presence of various supported sulfidized metal-containing catalysts at atmospheric pressure and T = 150−350°C was studied. Sulfidized transition metals supported onto aluminum oxide were more active than catalysts based on a carbon support, silicon dioxide, amorphous aluminosilicate, and zeolite ZSM-5. The most active catalyst was 10% Co/Al₂O₃ prepared with the use of cobalt acetate as an active component precursor and treated with a mixture of hydrogen sulfide with hydrogen at T = 400°C. From kinetic data, it follows that all of the reaction products were formed simultaneously at a temperature of <200°C, whereas a consecutive reaction scheme took place at higher temperatures. In the presence of a sulfidized alumina-cobalt catalyst, the output of dimethyl sulfide was higher than that reached with the use of other well-known catalysts.     

Activity of catalysts in the synthesis of dimethyl sulfide from dimethyl disulfide

Dimethyl disulfide conversion at T = 190–350°C over catalysts containing acid and basic sites is reported. The products of this reaction are dimethyl sulfide, methanethiol, hydrogen sulfide, carbon disulfide, methane, and ethylene. At 190°C, these products form via parallel reactions. At higher temperature of up to 350°C, dimethyl sulfide can form by the condensation of the resulting methanethiol. The strong basic sites of the catalysts are uninvolved in dimethyl sulfide formation. Over catalysts whose surface has only strong protonic or strong Lewis acid sites, dimethyl sulfide formation does take place, but slowly and nonselectively. The highest dimethyl sulfide formation activity and selectivity are shown by catalysts having medium-strength basic sites along with strong protonic and strong Lewis acid sites.     

Activity of zeolites in dimethyl sulfide synthesis

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.     

Catalytic decomposition of dimethyl disulfide

We have studied dimethyl disulfide conversion on heterogeneous catalysts in a flow setup at T=250–350°C and atmospheric pressure. Methyl mercaptan appears to be the main reaction product. The rate of dimethyl disulfide decomposition and its selectivity towards methyl mercaptan in H₂S medium are higher than those in pure helium. Thus the process seems to involve the surface protons formed upon dissociative H₂S chemisorption.     

Methylation of benzene with dimethyl disulfide

Dimethyl disulfide reacts with benzene at 250–350°C over a period of 1–20 s in the presence of catalysts containing strong Brønsted and Lewis acid centers to give a mixture of methylbenzenes, viz. toluene, isomeric xylenes, mesitylene, and durene.     

Catalytic synthesis of dimethyl sulfide from dimethyl disulfide and methanol

The reaction of dimethyl disulfide with methanol was studied at atmospheric pressure and temperature of 350°C in the presence of catalysts containing acid and basic sites.     

Photochemistry of benzisothiazoles in the presence of dimethyl acetylenedicarboxylate

1,2-Benzisothiazole gave upon irradiation in the presence of dimethy acetylenedicarboxylate a mixture of $\text{cis}$- and $\text{trans}$- $\text{substituted}$ phenylthioalkenes (II) and 7-cyano-2,3-dicarboxybenzothiophene.     

Hydrogen yield from water radiolysis in the presence of zeolites

This paper reports a study of the decomposition of water by gamma radiolysis in the presence of zeolites ZSM-5, SAPO-5, and MOR. The irradiation is performed using ⁶⁰Co as a source with 1.12×10¹⁵ Bq activity at a 8.3 kGy/h dose rate. The stable products of radiolysis as well as the other chemical species are measured by mass spectrometry. The calculated radiation yield (G_{H 2}) generally decreases in the order: H-ZSM-5>Na-ZSM-5>H-SAPO-5>MOR under the given experimental conditions; the yield is higher in the presence of these catalysts than in their absence.     

Photoexcitation of dimethyl sulfide and dimethyl disulfide in the vacuum ultraviolet region: Rydberg states and photofragment emissions

Photoabsorption cross sections and fluorescence excitation spectra of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) vapors have been studied in the 110–220 nm region using synchrotron radiation. For DMS, a new Rydberg series originating from the n_s orbital is identified. A number of broad bands from DMDS are assigned as Rydberg transitions. Emissions from DMS and DMDS are assigned as the CH₃( - ) band. For DMDS, another emission which is attributable to the S₂(B-X) band appears in the excitation below 125 nm. Photodissociation processes forming the excited fragments are discussed.     

Catalytic reactions of dimethyl disulfide with thiophene and benzene

The gas-phase reaction of dimethyl disulfide with thiophene proceeds under the action of acid catalysts under atmospheric pressure at 160–350°C and a residence time of τ = 0.6–21 s to form thioalkylation and alkylation products. Dimethyl disulfide reacts with benzene to form only alkylation products. Catalysts containing both strong protic and Lewis acid sites, as well as basic sites of moderate strength, are the most active ones.     

Conversion of toluene on NiNaY and CeNaY zeolites

Ce–Y and Ni–Y zeolites were studied in the toluen conversion reaction before and after poisoning the acid centers by Na⁺ ions. It has been found that both Ce–Y and Ni–Y zeolites were active in the disproportionation of toluene at elevated pressures, which occur on strong Brönsted acid centers. The poisoning of the acid centers in Ni–Y zeolite led to the appearance of the activity of metallic Ni and complete change in the selectivity.

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Ce- Ni- Na⁺. , , . Ni- .

     

Transformations of isobutylene in the presence of various types of zeolites

Conclusions In contrast to zeolites with ultrahigh silica content, type A, X, Y, and M zeolites in the Na form and also those modified by decationization, cation exchange, and addition of-Al₂O₃, Al₂O₃-SiO₂, Pt, and Rh show a low activity in the aromatization reaction of C₃-C₄ olefins at 450–550°C at times of contact of 2–14.4 sec. The zeolites studied become rapidly deactivated as the result of intense coke formation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1300–1304, June, 1981.     

Radiation-induced polymerization of styrene in the presence of n-dibutyl disulfide

The γ-radiation-induced polymerization of pure styrene and styrene-n-dibutyl disulfide mixtures has been studied at a number of temperatures and dose rates. Up to 0.04 Mrad/hr the rates were proportional to the square root of the dose rate. By measuring the rates at a number of disulfide concentrations and at three different dose rates, the relative rates of radical formation were determined by kinetic analysis. Considerable energy transfer from the styrene to the disulfide was found. The relative contributions of energy transfer and radical formation were separated by using the kinetic scheme of Nikitina and Bagdasaryan. Values of 8.5 and 3.1 were found for the relative rates of radical production and energy transfer, respectively. This leads to a G (radical) value of 3.1 for n-dibutyl disulfide. With azobisisobutyronitrile as the initiator, the chain transfer constant to the disulfide was determined at 55°C. Finally, the sulfur content of a number of the polymers were determined, an average of two sulfur atoms per polymer chain was found. In general, the rate of polymerization was found to increase in the presence of dibutyl disulfide.