Magdaléna Štolcová

Novel Cu and Cu2In/aluminosilicate type catalysts for the reduction of biomass-derived volatile fatty acids to alcohols

AbstractThis work relates to the consecutive reduction of short chain carboxylic acids (volatile fatty acids, VFAs) to alcohols as main products. Acetic acid (AA) was used as a reactant to model the VFAs that can be produced by either thermochemical or biological biomass degradation. The amorphised zeolite supported copper catalysts (Cu/SiAl), especially the In-modified CuIn/SiAl catalysts, showed high hydroconversion activity and selectivity for alcohol, ester and aldehyde. Catalysts containing dispersed copper particles in amorphous aluminosilicate were obtained by dehydrating and H2-reducing Cu-forms of low-silica synthetic zeolites (A, X, P). The activity of the highly destructed Cu-aluminosilicates was found to depend on the structure of the zeolite precursor. The formation of ethyl acetate could be suppressed by adding water to the AA feed and by modifying the catalyst, e.g. by In2O3 additive. In the catalysts modified by In2O3 additive formation of copper-indium alloy phase (Cu2In intermetallic compound) was detected resulting in a different selectivity than the one recorded for the Cu/SiAl.

Reaction of N-phenylhydroxylamine in the presence of clay catalysts

The condensation reaction of N-phenylhydroxylamine in the presence of clay catalysts was studied. The main products of this reaction are azoxybenzene, aniline and nitrosobenzene. In contrast with the previously published results, p-nitrosodiphenylamine is not formed during the condensation reaction.

Reaction of N-tert-butyl-2-benzothiazolesulphenamide with acetic anhydride in the presence of acids: II. Spectral studies

Abstract The reaction of N-tert-butyl-2-benzothiazolesulphenamide with acetic anhydride catalyzed by acetic acid in a nonpolar solvent has been studied by NMR, GC–MS and EPR techniques. In the catalytic process homolytic decomposition of N-tert-butyl-2-benzothiazolesulphenamide prevails over the heterolytic pathway which is typical for uncatalyzed reaction. Besides the typical products formed during the uncatalyzed reaction, in the acid catalyzed process products formed by recombination of radicals were confirmed by 13 C NMR and mass spectroscopy. In the formation of TBbisBS by homolytic pathway N,N′-dialkylhydrazine radicals and RNH radicals, produced by decomposition of N,N′-dialkylhydrazine, play probably an important role.

Reversed-phase high-performance liquid chromatographic method for the quantitative determination of alkylbis(2-benzothiazolylsulfen)amides

Abstract An isocratic, reversed-phase HPLC procedure was developed for the simultaneous determination of isopropyl-, tert.-butyl-, tert.-amyl-, cyclohexylbis(2-benzothiazolylsulfen)amides. Quantitation is performed on a C18 bonded-phase column (Separon SGX C18 5 μm) using N-dicyclohexyl-2-benzothiazolesulfenamide as internal standard followed by UV photodiode-array detection. The precision (n = 7) for all derivatives of alkylbis(2-benzothiazolylsulfen)amides is within 1.5%. Identification of the compounds also in the mixtures was done by NMR spectroscopy.

Determination of the products of the reaction of N-alkyl-2-benzothiazolesulfenamide by high-performance liquid chromatography with acetone

Abstract A slow reaction was observed between N-alkyl-2-benzothiazolesulfenamide derivatives and acetone at ambient temperature. The formed products identified by NMR technique are 1,1-bis-(2′-benzothiazolethio)-2-alkylaminoprop-1-ene, 1-(2′-benzothiazolethio)-2-morpholinoprop-1-ene and 2′-(benzothiazolylthio)propan-2-one. A packed octadecyl-bonded silica column has been employed for the separation of the main reaction products by HPLC. The precision of the gradient method used was below 2.3%.

Direct sulfenylation of acetone with benzothiazolesulfenamides to benzothiazolylthio-substituted alkylaminopropene: synthesis and application

N-Substituted derivatives of 2-benzothiazolesulfenamides give high yields of 1-(2′-benzothiazolylthio)-2-alkylaminoprop-1-ene and 1,1-bis-(2′-benzothiazolylthio)-2-alkylaminoprop-1-ene in a reaction with acetone in the temperature range from 56°C to 70°C and in the presence of a small amount of water. The α-sulfenylated carbonyl product, 2′-benzothiazolylthiopropan-2-one, is supposed to be an intermediate of this one-pot synthesis. 1,1-Bis-(2′-benzothiazolylthio)-2-tert-butylaminoprop-1-ene has been proved an accelerator of sulfur curing of rubber composites with high processing safety.