Karel Frolich

The present study investigates the catalytic upgrading of bioethanol to higher-value chemicals through heterogeneous catalysis, with a focus on the production of 1-butanol as a versatile compound widely used in many applications. Copper-impregnated Li-Al mixed metal oxides were synthesized and characterized as catalysts for ethanol transformation. Comprehensive characterization techniques were involved to correlate catalyst properties with their performance and describe catalyst stability. The catalysts showed promising activity in the formation of higher alcohols under a high weight hourly space velocity (WHSV) and pressure. Theoretical calculations were incorporated into the study to describe the feasibility of individual steps in the Guerbet reaction with main side reactions involved and to supplement information regarding the influence of the catalyst itself. The temperature effects on the reactions were illustrated. In this way, we attempted to explain the role of the catalyst in the reaction pathways, contributing to a more precise tuning of the catalytic system.

Hyaluronic acid is an excellent biocompatible material for in vivo applications. Its ability to bind CD44, a cell receptor involved in numerous biological processes, predetermines HA-based nanomaterials as unique carrier for therapeutic and theranostic applications. Although numerous methods for the synthesis of hyaluronic acid nanoparticles (HANPs) are available today, their low reproducibility and wide size distribution hinder the precise assessment of the effect on the organism. A robust and reproducible approach for producing HANPs that meet strict criteria for in vivo applications (e.g., to lung parenchyma) remains challenging. We designed and evaluated four protocols for the preparation of HANPs with those required parameters. The HA molecule was cross-linked by novel combinations of carbodiimide, and four different amine-containing compounds resulted in monodisperse HANPs with a low polydispersity index. By a complex postsynthetic characterization, we confirmed that the prepared HANPs meet the criteria for inhaled therapeutic delivery and other in vivo applications.

The conversion of ethanol into petrochemicals, such as ethyl and butyl acetate, butanol, hexanol, and so forth was studied. The conversion was catalyzed by Mg-Fe mixed oxide modified with a second transition metal (Ni, Cu, Co, Mn, or Cr). The main aim was to describe the influence of second transition metal on (i) the catalyst itself and (ii) reaction products such as ethyl acetate, butanol, hexanol, acetone, and ethanal. Moreover, the results were compared with the results of pure Mg-Fe. The reaction was carried out in the gas phase in a flow reactor with a weight hour space velocity of 4.5 h^-1 for 32 h at three reaction temperatures (280, 300, and 350 °C). The metals Ni and Cu in Mg-Fe oxide enhanced the ethanol conversion due to the population of active dehydrogenation sites. Despite the lower acido-basicity, Cu, Co, and Ni supported the yield of ethyl acetate, and Cu and Ni also promoted the yield of higher alcohols. Ni was related to the extent of the gasification reactions. Moreover, long-term stability (by leaching of metals) test was carried out for all catalysts (128 h).

The paper is focused on the epoxidation of methyl esters prepared from oil crops with various profiles of higher fatty acids, especially unsaturated, which are mainly contained in the non-edible linseed and Camelina sativa oil (second generation). The novelty consists in the separation and identification of all products with oxirane ring formed through a reaction and in the determination of time course. Through the epoxidation, many intermediates and final products were formed, i.e., epoxides with different number and/or different position of oxirane rings in carbon chain. For the determination, three main methods (infrared spectroscopy, high-pressure liquid chromatography and gas chromatography with mass spectrometry) were applied. Only gas chromatography enables the separation of individual epoxides, which were identified on the base of the mass spectra, molecule ion and time course of products. The determination of intermediates enables: (i) control of the epoxidation process, (ii) determination of the mixture of epoxides in detail and so the calculation of selectivity of each product. Therefore, the epoxidation will be more environmentally friendly especially for advanced applications of non-edible oil crops containing high amounts of unsaturated fatty acids.

This paper is focused on the heterogeneously catalyzed transesterification (in a batch reactor) of vegetable oil, including the determination of leached metals. The oil was obtained from the short-season crop Camelina sativa. The reaction was catalyzed by mixed oxides, which were synthesized from Mg/Al hydrotalcites with built-in different types of divalent cations such as Mn, Ca, Co, Ni, and Fe. The various physicochemical properties like the structure by X-ray diffraction, acidity, basicity, and textural properties were measured and the effect of the added cation type on catalyst properties and activity was compared. A noticeable relationship between the cation type and catalytic activity in the transesterification reaction was observed. The highest ester content of 96.6 wt % after 7 h of transesterification was observed for catalysts with nickel and iron. The statistical analysis of results showed that the catalyst activity was mainly influenced by middle-temperature basic sites. The novelty lies in transesterification over five different heterogeneous catalysts—mixed oxides with added divalent metals at the same reaction conditions of C. sativa oil.

Background: Pyroaurite‐based MgFe oxides with varying Mg:Fe ratio were studied. The structural and acido‐basic properties were examined by number of experimental techniques. The oxide properties were correlated with the catalytic activity in aldol condensation of furfural with acetone.Results: Well‐developed mesoporous structure was detected for all oxides. Peculiar continuous increase of concentration of basic sites and population of unsaturated strong basic O²⁻ sites was observed with the rising amount of magnesium in the MgFe oxide matrix. A relatively higher concentration of Lewis acid Meⁿ⁺ sites was shown for low Mg:Fe ratios. Unambiguous correlation between conversion of furfural and the density of strong basic sites was proved by combined catalytic and statistical analysis. The contribution of other basic sites was found significantly less important. The impact of both acid and basic sites on the composition of reaction products was discussed.Conclusions: MgFe oxides revealed good catalytic performance in the aldol condensation of furfural with acetone where samples with a high Mg:Fe ratio were significantly more basic and had relatively enhanced furfural conversion (nominal Mg:Fe ratio 10; furfural conversion 88% and selectivity to F₂Ac 34%; reaction conditions: batch reactor; 50 °C; acetone/furfural = 10 mol L^–1). © 2018 Society of Chemical Industry