Transition metal-modified polyoxometalates supported on carbon as catalyst in 2-(methylthio)-benzothiazole sulfoxidation

Abstract

Polyoxometalates with lacunary Keggin structure modified with transition metal ions [PW 11 O 39 M(H 2 O)] 5− , where M= Ni 2+ , Co 2+ , Cu 2+ or Zn 2+ , were synthesized and supported on activated carbon to obtain the PW11MC catalysts. Using FT-IR and DTA-TGA it was concluded that the [PW 11 O 39 M(H 2 O)] 5− species are interacting with the functional groups of the support, and that thermal treatment leads to the loss of the coordinatively bonded water molecules without any noticeable anion degradation. The activity and selectivity of the catalysts in the sulfoxidation reaction of 2-(methylthio)-benzothiazole, an emerging environmental pollutant, were evaluated. The reaction was carried out in acetonitrile as solvent using H 2 O 2 35% p/v as a clean oxidant. The conversion values decreased in the following order: PW11NiC > PW11CuC > PW11CoC > PW11ZnC, with selectivity to sulfoxide higher than 69%. The catalyst could be reused without appreciable loss of the catalytic activity at least three times. The materials were found to be efficient and recyclable catalysts for 2-(methylthio)-benzothiazole sulfoxidation in order to obtain a more biodegradable product than the corresponding substrate.

Flexible oxidation of styrene using TBHP over zirconia supported mono-copper substituted phosphotungstate

“…41 The Raman spectra of PW 11 Cu shows peaks at 11 Cu with maxima at 666 C and 960 C which have been assigned to reduction of species aer anion decomposition. 42 In the present case, similar maxima are obtained at 592 C and 819 C, which is attributed to formation of WO 3 species. 43 The decrease in reduction temperature is attributed to increase in the consumption of H 2 gas due to Cs counter cation.…”

“…The H 2 -TPR spectra of PW 11 Cu/ZrO 2 has a peak with lesser intensity and shows maxima at 518 C, while the second peak gets overlapped with the reduction peaks of ZrO 2 , which fall in the temperature range of 700-900 C. 45 The decrease in intensity as well as reduction temperature may be due to chemical interaction of [PW 11 Cu] 5À anions with the support. 42 This is further conrmed by 31 P MAS NMR. 31 P NMR is an important tool to understand the environment around phosphorus in polyoxometalates as well as the interaction of the anion with support.…”

Keggin-type lacunary and transition metal substituted polyoxometalates as heterogeneous catalysts: A recent progress

“…For the SiW 11 Co anion coordination of the Co metal to the amino group predominates when the reaction of POM with functionalized silica was performed at pH 5.5, while electrostatic interaction between the negatively charged POM and the protonated propylamine group was suggested to be predominant at pH 3.5. The 31 (126,127). The synthesis of supported TMSPOMs leads to compounds with a slightly lower thermal stability than that of the parent lacunary PW 11 .…”

“…In turn, the reduction temperature of these supported catalysts is shifted to lower temperatures compared to that of the corresponding bulk compounds. The application of the synthesized compound was tested for dehydration of isopropanol to give propene (128) as well as sulfoxidation reaction of 2-(methylthio)-benzothiazole (2-MTBT) (127). The activity of the synthesized catalysts in 2-MTBT sulfoxidation reaction decreased in the following order: PW 11 (128).…”

Heterogenized peroxopolyoxotungstate catalyst on the surface of clicked magnetite‐graphene oxide nanocomposite: Magnetically recoverable epoxidation catalyst

“…Frenzel et al . investigated the activity and selectivity of the lacunary Keggin POMs supported on activated carbon in the sulfoxidation reaction . Shanmugam et al .…”