Jenő Hancsók

Since 2011, the volume of passenger air transport grew nearly 7.5%/year, while freight air transport grew 3.6%/year regarding to the performed kilometers. The expansion of the aviation sector resulted increasing fuel consumption, too. The growing usage of fossil-based jet fuel results significant particle and carbon dioxide emissions, which causes remarkable environment pollution. This emission can only be reduced with using alternative jet fuels, especially those are originated from natural/waste fatty acid/-ester triglyceride sources. The aim of the experimental work was to compare industrially applied sulfide-state catalysts containing different transition metals from the aspect of catalytic conversion of mixtures of waste coconut oil and unrefined kerosene to produce jet fuel at various process parameters (temperature = 280–360 °C, liquid hourly space velocity = 1.0–3.0 h⁻¹, pressure = 30 bar, hydrogen/hydrocarbon volume ratio = 600 Nm³/m³) in a continuous down-flow tubular reactor system. The obtained products contributes to decrease in particle and carbon dioxide emission of aircrafts due to their lower aromatic content. The smoke point of the products obtained at favorable process parameters was higher than 30 mm, while the requirement in ASTM D 1655 standard is minimum 25 mm.

Biomass-based Fischer–Tropsch paraffin mixtures, having C₁₆–C₄₆ and C₁₁–C₄₅ carbon number range, were hydrocracked over platinum-supported beta, ZSM-5, and mordenite catalysts. The aim of the study was to investigate the effects of the feedstock composition, the process parameters, and the catalyst properties (acidity and zeolite structure) on the C_21⁺ conversions, the product yields, and the isoparaffin contents. It was stated that lower C_21⁺ conversions and higher JET and diesel fuel yields can be obtained for feedstock comprising C₁₁–C₄₅ hydrocarbons. Under identical reaction conditions, the activity order of the catalysts was Pt/H-beta > Pt/H-ZSM-5 > Pt/H-mordenite. This order corresponds to the relative number of accessible acid sites. Among the tested catalysts, platinum-supported beta zeolite showed the highest hydroisomerization activity; meanwhile, in the pores of Pt/ZSM-5 and Pt/H-mordenite, diffusion constraints were observed. As the product of hydrocracking valuable gasoline, JET and diesel fuels having high hydrogen content and excellent burning properties were produced.

MgO−SiO₂ samples, having the composition of natural talc (NT), were obtained by co‐precipitation (CP) and wet kneading (WK) methods. The materials were used as catalysts of the ethanol‐to‐1,3‐butadiene reaction. ZnO, Ga₂O₃ and In₂O₃ were tested as promoters. The catalyst WK gave the highest 1,3‐Butadiene (BD) yield among the non‐promoted catalysts because of the high specific surface area and strong basicity. Results suggested that over the neat WK catalyst the acetaldehyde coupling to crotonaldehyde was the rate‐determining process step. Formation of crotyl alcohol intermediate was substantiated to proceed by the hydrogen transfer reaction between crotonaldehyde and ethanol. The crotyl alcohol intermediate becomes dehydrated to BD or, in a disproportionation side reaction, it forms crotonaldehyde and butanol. The promoter was found to increase the surface concentration of the reactant and reaction intermediates, thereby increases the rates of conversion and BD formation. The order of promoting efficiency was Zn>In>Ga.

The thermal and catalytic conversion processes of alternative feedstocks (e.g., waste and biomass) to different engine fuels can result in the formation of a significant amount of light hydrocarbons as by-products in the boiling range of gasoline. The properties of these C₅/C₆ hydrocarbons need to be improved due to many reasons, e.g., their benzene content, and/or poor oxidation stability (high olefin content) and low octane number ( ca. 93 %) in the case of Pt/Al₂O₃/Cl. In addition, the octane number was also enhanced (ca. 32 > ca. 27 unit) in the products compared to the feedstock. This was because a higher isoparaffin content can be obtained at a lower operating temperature. Moreover, cracking side reactions take place to a lesser extent. The utilization of these isomerized bio-origin light fractions can contribute to the competitiveness of second-generation biofuels.