The studies of pyrolysis of caffeic acid (CA) and its surface complexes is important for the development of technologies of heterogeneous catalytic pyrolysis of plant- and wood- based renewable biomass components. In this work, the structure and thermal transformations of the surface complexes of CA on the surface of nanoceria were investigated using Fourier transform–infrared (FT–IR) spectroscopy, thermogravimetric analysis (TGA) and temperature-programmed desorption mass spectrometry (TPD MS). It was found that CA on the surface of cerium dioxide forms several types of complexes: bidentate carboxylates, monodentate carboxylates and complexes formed as a result of interaction with phenolic hydroxyl groups. This is due to the ability of nanosized cerium dioxide to generate basic hydroxyl groups that can deprotonate phenolic groups to form phenolates on the surface. The main pyrolysis products were identified. The possible ways of forming 3,4-dihydroxyphenylethylene, acetylene carboxylic acid, pyrocatechol and phenol from surface complexes of CA were suggested. It was established that on the nanoceria surface effectively occur the decarboxylation, decarbonylation, and dehydration reactions of the CA, which are the desirable processes in biomass conversion technologies.

Understanding the mechanisms of thermal transformations of model lignin compounds (MLC) over nanoscale catalysts is important for improving the technologic processes occurring in the pyrolytic conversion of lignocellulose biomass into biofuels and value-added chemicals. Herein, we investigate catalytic pyrolysis of MLC (pyrocatechol (P), guaiacol (G), ferulic (FA), and vanillic acids (VA)) over nanoceria using FT-IR spectroscopy, temperature-programmed desorption mass spectrometry (TPD MS), and thermogravimetric analysis (DTG/DTA/TG). FT-IR spectroscopic studies indicate that the active groups of aromatic rings of P, G, VA, and FA as well as carboxylate groups of VA and FA are involved in the interaction with nanoceria surface. We explore the general transformation mechanisms of different surface complexes and identify their decomposition products. We demonstrate that decomposition of carboxylate acid complexes occurs by decarboxylation. When FA is used as a precursor, this reaction generates 4-vinylguaiacol. Complexes of VA and FA formed through both active groups of the aromatic ring and decompose on the CeO₂ surface to generate hydroxybenzene. The formation of alkylated products accompanies catalytic pyrolysis of acids due to processes of transalkylation on the surface.

Studies of the thermochemical properties of the important model compound of lignin-ferulic acid (FA) and its surface complexes are substantial for developing technologies for catalytic pyrolysis of renewable biomass into biofuels and lignin-derived chemicals as well as for bio-oil upgrading. In this work, the catalytic pyrolysis of ferulic acid over alumina was studied by temperature-programmed desorption mass spectrometry (TPD MS), in situ FT-IR spectroscopy, thermogravimetric analysis, and DFT calculations. We established that both the carboxyl group and the active groups (HO and CH₃O) of the aromatic ring interact with the alumina surface. We calculated the kinetic parameters of formation of the main products of catalytic pyrolysis: 4-vinylguaiacol, guaiacol, hydroxybenzene, benzene, toluene, cresol, naphthalene, and PACs. Possible methods of their forming from the related surface complexes of FA are suggested.

Temperature-programmed desorption mass spectrometry (TPD MS) was used to study the pyrolysis of p-coumaric acid (pCmA) on the nanoceria surface. The interaction of pCmA with the CeO₂ surface was investigated by FT-IR spectroscopy. The obtained data indicated the formation on the nanoceria surface of bidentate carboxylate complexes with chelate (Δν = 62 cm⁻¹) and bridge structure (Δν = 146 cm⁻¹). The thermal decomposition of pCmA over nanoceria occurred in several stages, mainly by decarboxylation. The main decomposition product is 4-vinylphenol (m/z 120). The obtained data can be useful for studying the mechanisms of catalytic thermal transformations of lignin-containing raw materials using catalysts containing cerium oxide and the development of effective technologies for the isolation of pCmA from lignin.

In this work, we investigated the pyrolysis of sinapic acid (SA) as a lignin S‐units model compound on the nanoceria catalyst. We employed various techniques to unravel the pyrolysis mechanism, including temperature‐programmed desorption mass spectrometry, thermogravimetric, and IR spectroscopic techniques, complemented with atomistic simulations. From spectroscopic data and atomistic models, we report that SA interacts with the catalyst via its carboxyl group and aromatic functional groups; the amounts of various surface complexes depend on the acid concentration. Conformational analysis revealed that parallel adsorption on ceria was preferred over the perpendicular one (Δ E ₀ = −154 kJ mol ⁻¹ ). The main pyrolysis products are associated with transformations of phenolate complexes, with the predominant formation of syringol and with decarboxylation of carboxylates, forming 4‐vinyl syringol, well known as canolol, thanks to its exceptional antioxidant properties. Modeling the transition state between the SA and its vinyl analog, canolol, displayed an additional intramolecular decarboxylation pathway with an activation energy barrier of +189 kJ mol ⁻¹ . This is consistent with the activation energy E ^≠ = 194 kJ mol ⁻¹ calculated from experimental kinetic data, and complements other established decarboxylation pathways. Methyl‐syringol, cresol, phenol, toluene, benzene, and other aromatics were found among the catalytic pyrolysis products of SA.