## 1 Introduction  
Lignocellulose feedstock is a major potential renewable source of bio-oils and a large number of valuable chemicals. A total of 10-25% of lignocellulosic raw material is lignin [1]. The exact structure of lignin is still unknown; however, it is believed that lignin is formed through biosynthesis of \(p\)-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol [2]. Lignin determines the strength of trunks and stems of plants [3]. Due to its rigid structure, this natural polymer is currently used mainly for heat and energy production [4; 5; 6; 7]. However, the growing amount of research on the production of bio-oil and various chemicals from lignocellulosic raw materials motivates the search for effective ways to process lignin [4; 5; 7]. Due to its unique structure, lignin can be a source of a large number of aromatic compounds, both monomers and polymers [1; 8; 9]. Since the structure of this natural polymer is extremely complex, model compounds are often used to study its conversion to high value-added chemicals [8; 10]. Ferulic and vanillic acids, as well as pyrocatechol and guaiacol are common products of lignin processing [1; 11; 12; 8; 13], and therefore are often used as model lignin compounds [4; 8; 11; 14; 15; 16; 17]. These compounds are lignin structural units of various sizes and contain almost the entire list of functional groups present in the lignin macromolecule. Among these products, guaiacol is an ideal model compound for assessing the performance of various catalysts, as it is a typical component of pyrolysis oil and one of the most complex methoxyphenols for deoxygenation [18; 19]. Pyrocatech is often an intermediate in converting other model lignin compounds, for example, guaiacol [8; 20]. Ferulic acid may be used for the production of valuable aromatic chemicals, in particular 4-vinylguaiacol [20; 21; 22; 23; 24], vanillin, and vanillin acid [25; 24; 26]. In addition to lignin, these compounds are found in large quantities in other polymers of vegetable raw materials and in the waste generated during their processing (wine-distileries, olive oil processing, table olive industries, pulp paper processing, etc.) [26; 27; 28; 29]. Due to the high toxicity of phenol-containing compounds to microorganisms [29; 30; 31], special attention is directed to their utilization [24; 32]. Pyrolysis is commonly used for lignin processing due to its ability to effectively separate this polymer's strong structure [8; 11; 33; 34]. However, high-temperature conversion of these raw materials generates a large number of final pyrolysis products. Various catalytic systems are used to overcome these imperfections [34]. CeO\({}_{2}\) is often used as a catalyst in the catalytic conversions of lignocellulosic raw materials [35; 36; 37; 38; 39; 40]. Its catalytic properties are attributed to the ease with which it alternates between the 3+ and 4+ oxidation states, depending on the environmental conditions. [35]. The corresponding number of oxygen vacancies compensates for the decrease in the positive charge of Ce\({}^{3+}\). The concentration of defects, both Ce\({}^{3+}\) ions and oxygen vacancies, on the oxide surface is higher than in the bulk [41]. Therefore, nanosized cerium oxide has higher concentrations of Ce\({}^{3+}\) ions and, accordingly, redox activity compared to large particles, since the surface-to-volume ratio increases [42]). In the conversion and valorization of lignocellulosic raw materials and model compounds of lignin, cerium oxide is combined with other catalysts, particularly metals [38; 39] and zirconium oxide [16; 35; 43]. In the work of [PERSON] and co-authors [32], CeO\({}_{2}\) oxide with platinum deposited on its surface was used for the oxidative conversion of lignin and 2-phenoxy-1-phenyl-ethanol, which contains \(\beta\)-O-4 bonds and C\(\alpha\)-hydroxyl groups, in monomeric aromatic compounds (4-methoxy-phenol, acetophenone, methyl benzoate (82%, 38%, and 40%). Pt/ CeO\({}_{2}\) catalysts have also been used to convert 4-propyl-phenol to propply-cyclohexane. [37].