Design of the catalytic properties and structure of zeolite materials play a key role in efficient transformation of biomass to sustainable chemicals. In the present study, we have designed theoretical and experimental approach for the production of acrylic acid (AA) from lactic acid (LA) over zeolite catalysts. Various BEA zeolites modified with metals (Co, Cu and Fe) were prepared using ion exchange and sonication methods. In the theoretical studies the metal M-O-M dimers have been found to be stable above oxygen bound with aluminium centers of BEA zeolite. The mechanism of direct LA dehydration over the Co-, Cu-and Fe-BEA zeolites has been proposed. Experimentally, the investigated catalysts trend in following byproduct formation: AA, propionic acid (PA), 2,3-pentanedione (2,3-PD) or acetaldehyde (AC). The best selectivity towards acrylic acid was achieved in the presence of the Co-and Cu-BEA catalysts prepared by the sonication method.

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The authors present a short review of selected natural-origin zeolite materials. This article discusses the structure, classification and ability to modify natural zeolites, along with examples of their potential applications as adsorbents or catalysts.

This article presents the results of the conversion of dihydroxyacetone (DHA) to lactic acid (LA) with the use of zeolite catalysts. For this purpose, synthetic zeolite beta (BEA) and natural clinoptilolite (CLI) were used as a matrix. The zeolites were modified with various metals (Sn, Fe, Cu and Zn) during ion exchange under hydrothermal conditions. The DHA conversion process with the participation of metal-functionalized zeolites allowed us to obtain intermediates, i.e., pyruvic aldehyde (PAL), which during the further reaction was transformed into a mixture of products such as ethyl lactate (EL), pyruvic aldehyde (PA), lactic acid and ethyl acetate (EA). The best selectivity towards lactic acid was achieved using Sn-CLI (100%) > Na-BEA (98.7%) > Sn-BEA (95.9%) > Cu-BEA (92.9%), ethyl lactate using Cu-CLI, and pyruvic aldehyde using the Zn-BEA catalyst. In the case of a natural zeolite, modification with Sn is promising for obtaining a pure lactic acid with a relatively good carbon balance.

This article presents the results of the conversion of biomass-based glucose to levulinic acid (LA) with the use of Na-BEA commercial zeolite catalyst. For this purpose, synthetic zeolite BEA was used as a matrix. The glucose conversion process with the participation of Na-BEA zeolite allowed the following acids to be obtained: levulinic acid, lactic acid, pyruvic acid and formic acid. The highest yield of levulinic acid was achieved when processed for 1–5 h at 200–250 °C with 0.1 g and 0.6 g of Na-BEA catalyst. We also compare the one-pot heterogeneous process with similar homogeneous process using H2SO4 as catalyst.

This paper is interested in mechanism of lactic acid (LA) adsorption and dehydration into acrylic acid (AA) over tin and iron beta zeolite (Sn-and Fe-BEA) catalysts. The electronic structure of clusters was calculated by ab initio density functional theory (DFT) method. The M2Si12O39H22 (hierarchical zeolite) and M2Si22O64H32 (ideal zeolite) clusters (M=Al, Si, Sn) were used in the LA dehydration reaction. The stabilization of the dimeric complex MOb -M (where M= Sn or Fe) in the BEA, ideal and hierarchical structure, was investigated. Possible modes of interaction of lactic acid with different cations (Si, Al, Fe or Sn) in the BEA zeolite framework as well as with added iron and tin dimers were considered. The interaction of lactic acid was only observed above the MOb -M dimer. The direct mechanism of lactic acid dehydration into acrylic acid was found over metal MOb -M dimers deposited at the BEA zeolite.

The production of chemicals from biomass is a very challenging process due to its diverse chemical composition. Lignin, cellulose and hemicellulose are the three main biopolymers of wood biomass, with cell walls of plant origin. Lignin has been chosen for the present studies due to its range of different linkages and structures. The present work involved a computational study of the most dominant lignin dimers and their vibrational structures, based on the Density Functional Theory method. Full geometry optimization of the compartments used the StoBe code with cluster model and non-local functional (RPBE) approach. The calculations of the vibrational frequencies were performed with harmonic approximations as well as an anharmonicity fit in the Morse potential function, as implemented in the StoBe code. In the case of lignin, the calculations included three different precursors based on: coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. To represent the cellulose and hemicellulose derivatives, selected aldopentoses and aldohexoses (arabinose, xylose, glucose, galactose, and mannose) were considered. Presented here are the theoretical investigations for a variety of biomass derived compounds, to give the possibility of obtaining a theoretical VBD (Vibrations Basis Database) for experimental spectra interpretation. Such a database could be further used in the preliminary composition assessment of biomass derived substrates, which will be discussed here in more detail.

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