Capture of sulfur dioxide from Claus tail gas using fiber-like alumina-based adsorbents

This paper describes the preparation of alumina fibers doped with CaO, MgO and La₂O₃ and reports their use as SO₂ adsorbents. These materials were characterized using electron microscopy, powder X-ray diffraction and infrared analysis and were examined for their ability to capture SO₂ selectively from gas mixtures containing large quantities of H₂O, CO₂ and some O₂ at temperatures in excess of 353 K. Overall, it was found that these adsorbents could remove SO₂ selectively and that they could be regenerated by treatment with an H₂S-containing gas at approximately 600 K. Adsorption capacity was retained over several cycles. Fourier transform infrared analysis showed that SO₂ was adsorbed as free SO₂ and also in a combined form as sulfite and sulfate species. In the regeneration step, the adsorbed sulfur species were reduced to elemental sulfur and H₂S or were desorbed as SO₂. It is proposed that the chemistry described here could be applied to design of a process for capture of all sulfur species typically found in a Claus-based sulfur recovery system.

     

Silica-supported phosphorus pentoxide: a reusable catalyst for S,S-acetalization of carbonyl groups under ambient conditions

Phosphorus pentoxide supported on silica gel (P₂O₅/SiO₂) efficiently acts as a highly active and reusable catalyst for cyclic and non-cyclic S,S-acetalization of a variety of carbonyl compounds under mild, solvent-free and ambient conditions. This method offers significant advantages such as high conversion, clean work-up, short reaction times and simplicity in operation.

     

Alumina-supported monoperphosphoric acid for selective oxidation of sulfides to sulfoxides

Selective oxidation of aromatic and aliphatic sulfides to the corresponding sulfoxide was achieved by using POCl₃/H₂O₂ and (alumina-supported phosphorus oxychloride)/H₂O₂. A versatile procedure for the oxidation of sulfides to sulfoxides without any over-oxidation to sulfones has been reported. It is noteworthy that the reaction is clean and tolerates oxidatively sensitive functional groups and the sulfur atom is selectively oxidized.

     

Regioselective ring-opening of aziridines with diselenides and disulfides using the Zn/AlCl3 system

An efficient Zn/AlCl₃-promoted highly regioselective one-pot procedure has been demonstrated for the synthesis of β -amino selenides and sulfides from a variety of diselenides/disulfides and aziridines by reductive cleavage of Se–Se and S–S bonds using the Zn/AlCl₃ system in acetonitrile under very mild conditions.

     

Synthesis and characterization of copper(I) complexes from triphenylphosphine and isatin Schiff bases of semi- and thiosemicarbazide

The reaction of isatin-3-thiosemicarbazone (ITC, 1) or isatin-3-semicarbazone (ISC, 2) with nitrato bis(triphenylphosphine)copper(I) gave the four coordinate copper(I) complexes [Cu(PPh₃)₂(ITC)]NO₃ (3) and [Cu(PPh₃)₂(ISC)]NO₃ (4). The synthesized complexes were characterized by FT-IR, UV–VIS, Raman and elemental analysis. The crystal structure of 3 was investigated by single crystal X-ray diffraction. The ITC coordinates to the copper(I) ion in a bidentate fashion via the N(imine) and S atoms which along with two triphenylphosphine ligands form a tetracoordinate complex. The complex has a distorted tetrahedral coordination environment. Crystal data at 150.0 K: space group P2₁/c with a=12.5777(4), b=15.2062(5), c=21.9057(7) Å, β=95.628(3)^o, Z=4, R ₁=0.049.

     

Novel atom-economic synthesis of thioselenophosphinates via three-component reaction between secondary phosphine sulfides,elemental selenium,and amines

An efficient, general, and atom-economic synthesis of organoammonium thioselenophosphinates has been developed by exploiting a three-component reaction between secondary phosphine sulfides, elemental selenium, and various amines. The reaction proceeds under mild conditions (70–75 °C, 1 h, EtOH) to afford thioselenophosphinates in 77–94% yields.

     

Reactions of Pd2+ and Pt2+ with pyrrolidinedithio carbamate and cystine ligands: synthesis and DFT calculations

Mono- and dinuclear complexes of the type M(cys), M(PTD)₂ and M₂(PTD)₄, where M=Pd (II) or Pt(II), cys=(SCH ₂CH (NH ₂)COOH)₂ and PTD=pyrrolidine thiocarbanoyl disulfide, have been prepared through oxidative addition reaction. They are characterized by microanalyses of metal content, molar conductance, magnetic measurements, infrared and UV–visible spectral studies. The experimental infrared data are supported by density functional theory (DFT) calculations using the B3LYP level of theory and LANL2DZ basis set. The vibrational frequencies of the molecules were computed using the optimized geometry obtained from the DFT calculations. The diamagnetic nature, the electronic spectral studies and calculated geometries suggest a distorted square planner environment around Pd(II) and Pt(II) complexes.