China
Africa
Explore chapters and articles related to this topic
Feedstock Preparation
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
The Sulfinol process uses a solvent that is a composite solvent, consisting of a mixture of diisopropanolamine (30–45% v/v) or MDEA, sulfolane (tetrahydrothiophene dioxide) (40–60% v/v), and water (5–15% v/v). The acid gas loading of the Sulfinol solvent is higher and the energy required for its regeneration is lower than those of purely chemical solvents. At the same time, it has the advantage over purely physical solvents that severe product specifications can be met more easily and co-absorption of hydrocarbon derivatives is relatively low. Aromatic compounds, higher molecular weight hydrocarbon derivatives, and carbon dioxide are soluble to a lesser extent. The process is typically used when the hydrogen sulfide–carbon dioxide ratio is greater than 1:1 or where carbon dioxide removal is not required to the same extent as hydrogen sulfide removal. The process uses a conventional solvent absorption and regeneration cycle in which the sour gas components are removed from the feed gas by countercurrent contact with a lean solvent stream under pressure. The absorbed impurities are then removed from the rich solvent by stripping with steam in a heated regenerator column. The hot lean solvent is then cooled for reuse in the absorber. Part of the cooling may be by heat exchange with the rich solvent for partial recovery of heat energy. The solvent reclaimer is used in a small ancillary facility for recovering solvent components from higher-boiling products of alkanolamine degradation or from other high-boiling or solid impurities.
Synthesis and Applications of LDH-Based Nanocomposites
Published in Mahmood Aliofkhazraei, Advances in Nanostructured Composites, 2019
Alireza Khataee, Samira Arefi-Oskoui
POM/LDH nanocomposites have been widely used as catalyst in different catalytic reactions. Carriazo et al. (Carriazo et al. 2007) intercalated H2W12O46– and W4Nb2O194– between the layers of Mg-Al LDH and Zn-Al LDH through ion exchange. The resulted POM/LDH nanocomposites were used as catalyst for epoxidation of cyclooctene in the presence of oxidants (H2O2 or t-BuOOH). The H2W12O46–/Zn-Al LDH nanocomposite showed the best results for epoxide yield (17% at 24 h). Maciuca et al. (Maciuca et al. 2008a) investigated the catalytic oxidation of thioethers and thiophene derivatives using H2O2 as oxidant and V-, Mo- and W-containing layered double hydroxides as catalyst. For preparing catalysts, metal-oxoanions, including WO42–, W7O246–, V2O74–, V10O286–, MnO42–, Mo7O246–, intercalated in the interlayer gallery of Mg-Al LDH using direct ion exchange. The results demonstrated that LDHs containing W-based POMs are more active and stable compared with LDHs containing V-based and Mo-based POMs. In addition, Maciuca et al. (Maciuca et al. 2008b) in another research investigated the catalytic activities of mentioned V-, Mo- and W-containing layered double hydroxides as catalyst for mild oxidation of tetrahydrothiophene to sulfolane. WO42–/LDH nanocomposite showed the best catalytic activity and stability for this oxidation process.
Hydrogen Production by Catalytic Hydrocarbon Steam Reforming
Published in Deniz Uner, Advances in Refining Catalysis, 2017
Peter Broadhurst, Jumal Shah, Raimon Perea Marin
In natural gas feeds, S is the prevalent poison; it is generally found at levels between 1 and 30 ppmv depending on the gas source and pretreatment. Gases that are shipped as liquefied natural gas (LNG) or pipelined long distances are low in sulfur due to deliberate desulfurization. In some locations, the gas has a stenching agent added near the point of use to aid in leak detection. This stenching agent is typically 2–3 ppmv of a sulfur compound such as tetrahydrothiophene (THT) or tBuSH (TBM). Other than this, the sulfur compounds will be a combination of hydrogen sulfide, mercaptans, organic sulfides, and disulfides. Thiophenes are rarely observed.
Aryl sulfonyl chlorides and sodium aryl sulfinates: non-volatile, non-stench, and non-toxic aryl thiol surrogates for direct aryl-sulfenylation of C–H bonds
Published in Journal of Sulfur Chemistry, 2020
Xiaohui Lu, Qicheng Yi, Xicai Pan, Peifang Wang, Esmail Vessally
In a related investigation, Zhao and co-workers disclosed a metal-free procedure for the synthesis of aryl thioethers upon reaction of ethers with sodium sulfinates [49]. They carefully studied the reaction variables such as catalyst, oxidant, and additive and found that performing the reaction in the presence of I2/TBP/(EtO)2P(O)H combination as a catalytic system at 130°C under air was the optimum reaction condition. The synthetic broad scope of this process was established by using a variety of functionalized sodium aryl sulfinates and ethers (cyclic and liner). Interestingly, this approach could also be applied to the direct sulfenylation of C(sp3)-H bond adjacent to a sulfur atom, such as tetrahydrothiophene.
3-Functional substituted 4-trifluoromethyl tetrahydrothiophenes via [3 + 2]-cycloaddition reactions
Published in Journal of Sulfur Chemistry, 2019
Yuriy M. Markitanov, Vadim M. Timoshenko, Tymofii V. Rudenko, Eduard B. Rusanov, Yuriy G. Shermolovich
Sulfur containing heterocyclic scaffolds and sulfur-derived functional groups can be found in a broad range of pharmaceuticals and organic substances of natural origin [1,2]. Among the numerous heterocyclic moieties featuring sulfur, those containing a tetrahydrothiophene ring system as a core structure are endowed with various types of biological activities and have therapeutic applications [3–7]. As a consequence, the demand for new tetrahydrothiophene derivatives in biology, pharmacology and medicinal chemistry has prospects for growth [8]. Trifluoromethyl group introduced into a heterocycle can alter the observed biological activities or cause changes in physico-chemical properties of a molecule [9–12]. At the same time, introduction of sulfur or phosphorus functionality, as well as their combination with the existing endocyclic sulfur moiety, can lead to a substantial change in the properties of a heterocyclic molecule, which can be useful in drug discovery processes. However, to the best of our knowledge, tetrahydrothiophene species containing an exocyclic sulfur functional group are barely represented in literature [13,14]. Reports on trifluoromethyl containing thiolanes are rare as well [15–20] and the described procedures for their preparation usually suffer from the low availability of precursors or complexity of synthetic routes. Tetrahydrothiophenes containing both a polyfluoroalkyl group and a sulfur or phosphorus moiety have not yet been described. In view of the scenarios mentioned above, we became interested in the synthesis of trifluoromethyl tetrahydrothiophene derivatives substituted with heteroatomic functional group, such as sulfone, sulfoximine, sulfonamide and phosphonate.