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Sn–Al-Beta zeolite was prepared through a hydrothermal method and further modified by alkali and alkaline earth (e.g. Sr and Ba) metals not practically altering the textural properties of the catalyst. The catalytic materials were tested in glucose transformation to methyl lactate in a batch reactor at 180 °C allowing to correlate catalytic activity and selectivity with the strength and type of acid sites. The results showed that by suppressing the Brønsted acidity of the modified catalyst with different promoters the yield of methyl lactate can be increased from ca. 20% to over 50%. Modification of Sn-Beta zeolite by alkali and alkaline earth (e.g. Sr and Ba) metals not practically altering the textural properties of the catalyst was essential for catalytic properties. The yield of methyl lactate can be increased from ca. 20% to over 50% by suppressing the Brønsted acidity of the modified catalyst with different promoters. [Display omitted] • Modification of Sn-Beta zeolite with alkali and alkaline earth (e.g. Sr and Ba) metals. • Glucose transformations to methyl lactate over these catalysts. • Catalytic activity and selectivity correlated with the strength and type of acid sites. • Suppressing Brønsted acidity increased methyl lactate yield from ca. 30% to over 50%. [ABSTRACT FROM AUTHOR]

The present work is focused on the improvement of an effective approach to tailor the acidity of silica alumina composite. SBA-15 was selected based on high surface area, uniform porosity and large mesopores. Modification of SBA-15 was performed to improve both Lewis and Brønsted acidities and hence catalyst activity. Therefore, introduction of alumina as a co-catalyst was carried out to enhance Lewis acid sites through its incorporation into the silica network. Evaporation impregnation method was evaluated for incorporation of aluminium to SBA-15 and materials with different SiO 2 /Al 2 O 3 ratios were prepared. Acidity and morphological features of the materials were assessed using XRD, EDX, SEM, TEM, N 2 -physisorption, 27Al MAS-NMR and FTIR with pyridine. Brønsted acidity was attained by the introduction of sulfonic acid groups in the final catalyst via the post-synthesis grafting method. Therefore, the balanced Lewis and Brønsted acidities and proper porosity of modified SBA-15 led to its efficient performance in the conversion of glucose as a biomass-based model component to levulinic acid. [Display omitted] • Acid sites modification of siliceous-based mesoporous material (SBA-15). • Alumina introduction as Lewis acid sites by evaporation impregnation technique. • Sulfonic acid groups incorporation as Brønsted acid sites by post-grafting method. • Obtaining the balanced acidity for biomass-based glucose transformation to levulinic acid. [ABSTRACT FROM AUTHOR]

Synthesis of Beta zeolite catalysts was carried out using two different methods. The influence of such parameters as synthesis time and temperature, gel composition and gel ripening on the physico-chemical and catalytic properties of Beta zeolite catalysts was studied. A range of analytical methods was applied in this work including scanning and transmission electron microscopies, energy dispersive X-ray spectroscopy, X-ray powder diffraction, nuclear magnetic resonance spectroscopy – 27A1-MAS-NMR and 29Si-MAS-NMR, nitrogen physisorption, Fourier transform infrared spectroscopy and inductively coupled plasma optical emission spectrometry. The sodium forms of Beta zeolites were transformed to the proton forms H-Beta by ion-exchange using aqueous solutions of NH 4 NO 3 and thereafter evaluated in Prins cyclization of (−)-isopulegol with benzaldehyde. The best catalyst synthesized at 150 °C in the rotation mode for 17 h possessing an optimal combination of morphological and structural properties as well as concentration of acid sites demonstrated high (−)-isopulegol conversion (93%) along with high selectivity to the desired product (79%). Image 1 • Influence of the synthesis parameters on properties of Beta zeolites. • Characterization of synthesized Beta zeolites by several methods. • Evaluation of activity in Prins cyclization of (−)-isopulegol with benzaldehyde. • Comparison of synthesized zeolites with a commercial beta zeolite. • High conversion and selectivity to the desired product. [ABSTRACT FROM AUTHOR]