Jan Hájek

Ruthenium-modified MCM-41 mesoporous molecular sieve and Y zeolite catalysts for selective hydrogenation of cinnamaldehyde

Abstract Ru-modified MCM-41 mesoporous molecular sieve and Y zeolite catalysts were synthesised and characterised using XRD, electrochemical voltammetry, ESCA (XPS), nitrogen adsorption and H2-TPD. Selective liquid-phase hydrogenation of cinnamaldehyde to cinnamyl alcohol was investigated over these catalysts and compared to hydrogenation on a commercial Ru/C catalyst. The effect of support (MCM-41, Y and C), solvent (cyclohexane, hexane and 2-propanol) and catalyst pre-treatment (calcination) on the conversion of cinnamaldehyde and selectivity to cinnamyl alcohol was studied. The zeolite structure, pore size, acidity, catalyst pre-treatment as well as the solvent influenced the activity and selectivity. Non-calcined Ru/Y exhibited the highest selectivity to cinnamyl alcohol. The activity of Ru/Y was highest with 2-propanol as a solvent.

Interconversion of Lactose to Lactulose in Alkaline Environment: Comparison of Different Catalysis Concepts

Interconversion of lactulose to lactulose with the aim to determine and optimize the yield of ketose was carried out. Various homogenous and heterogeneous alkaline catalysts were applied (NaOH, MgO, hydrotalcite etc.). The selectivity and activity of the catalysts were compared. The results gave insight to the performance differences among the screened catalysts under the various reaction conditions. From the activity performance point of view, the conversion was limited by the formation of acidic end-products. In general, the selectivity decreased with conversion and the conversion-selectivity pattern was independent of the catalyst.

High-selectivity hydrogenation of cinnamaldehyde over platinum supported on aluminosilicates

This work studies liquid-phase hydrogenation of cinnamaldehyde to cinnamylalcohol over Pt/K-10 and ion-exchanged Pt/Na-Y. The experiments show the highest selectivity of 78% for Pt/K-10 and 92% for the Pt/Na-Y. By careful analysis, characterisation and changing reaction conditions it was attempted to cover key parameters possibly responsible for the high selectivity. The parameters are described and discussed in detail.

Ruthenium-tin sol-gel catalysts: effect of the preparation and tin precursor influence

The influence of the synthesis route and the chemical nature of tin precursors on the catalytic properties of supported sol-gel Ru-Sn/SiO2 catalysts were studied. It was demonstrated that introduction of tin afforded better selectivities than a monometallic sol-gel catalyst in the liquid-phase hydrogenation of cinnamaldehyde; however, the chemical nature of the tin precursor did not influence the catalyst performance. Sol-gel catalyst properties depended significantly upon the preparation method used and on the activation temperature. The selectivity to unsaturated alcohol increased with conversion, which is indicative of the in-situ creation of active sites selective in the carbonyl bond hydrogenation.

Three-step synthesis of 1,1-dimethoxy-2-phenylpropane

In this work is presented a three-step synthesis of 1,1-dimethoxy-2-phenylpropane. The performed procedure was based on epoxidation of 2-phenylpropene to 2-methyl-2-phenyloxirane, acid catalyzed rearrangement of oxirane to 2-phenylpropanal and acetalization of the aldehyde to 1,1- dimethoxy-2-phenylpropane. The 1,1-dimethoxy-2-phenylpropane prepared was of high analytical purity (99.8%) with corresponding sensory properties, which allow its usage in the food industry.