Coal desulfurization in a fluidized bed reactor

Fluidized bed reactor technology was investigated as a means of developing a new simple and low cost process for coal desulfurization. Preliminary experimental results obtained in a 2.54 cm batch fluidized bed reactor have shown that over 80% total sulfur reductions can be achieved by sequential chlorination and dechlorination/ hydrodesulfurization of high sulfur pulverized coals. Proximate and ultimate analyses of desulfurized coals have revealed enhanced carbon and fixed carbon levels and substantially reduced volatile, oxygen and hydrogen contents. While there was a minor increase in the ash content and heating value, nitrogen and chlorine contents were essentially unchanged. Compared to an earlier slurry phase process, the fluidized bed reactors process has specific advantages such as shorter reaction times, fewer processing steps and reduced reactant requirements. A fluidized bed reactor process may thus have a potential of being developed into a simple and economic means of converting high sulfur coals to environmentally acceptable fuels.

A Facile Synthesis of 1,5-Disubstituted Tetrazole Peptidomimetics by Desulfurization/Electrocyclization of Thiopeptides

The cis-amide bond isostere, 1,5-disubstituted tetrazole,has been introduced in the peptide backbone by a simple route starting from the thiopeptide. The desired 1,5-disubstituted tetrazole peptidomimetics were synthesized by the desulfurization of thiopeptides by using HgCl2 in the presence of NaN3/TEA in DMF in good yields. Various other thiophilic reagents including hypervalent iodine reagents failed to deliver the tetrazole product with the exception of CBr4/PPh3, which resulted in moderate yields. The advantage of the present protocol over previous methods has been demonstrated by the selective insertion of tetrazole into peptide-thiopeptide hybrids. Also, the protocol is compatible with commonly employed urethane protecting groups (Fmoc, Boc, and Cbz) in peptide chemistry. Thiopeptide Boc-Pro-CSNH]-Val-OMe (2i) and two tetrazole peptidomimetics Cbz-Ala-CN4]-Phe-OMe (3d) and Boc-Pro-CN4]-Val-OMe (3i) were obtained as single crystals and their molecular structures have been confirmed by X-ray crystallography.