## 4 HPS-Based Catalysts for the Synthesis and Transformation of Platform Chemicals
### Hydrogenation of Furfural  
Technological advances in the field of biomass conversion make it possible to produce a wide range of products of different chemical natures, in particular, furfural (FF), which belongs to the furan group. These compounds are widely used in chemical synthesis \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **BET** & **Langmuir** & **t-Plot** \\ \cline{2-5}  & **S\({}_{\text{BET}}\), m\({}^{2}\)/g** & **S\({}_{\text{L}}\), m\({}^{2}\)/g** & **S\({}_{\text{tr}}\) m\({}^{2}\)/g** & **V, cm\({}^{3}\)/g** \\ \hline
3\% Pt/MN270 (initial) & 863 & 944 & 184 1, 678 2, 862 3 & 0.31 \\
3\% Pt/MN270 (used) & 324 & 345 & 99 1 2, 224 2, 323 & 0.10 \\ \hline \hline \end{tabular}  
* \({}^{1}\)—specific surface area surface of meso- and macropores; \({}^{2}\)—specific surface area of micropores; \({}^{3}\)—is the total specific surface area; \({}^{5}\)—specific surface area (Langmuir model); \({}^{5}\)—specific surface area (BET model); \({}^{5}\)—specific surface area (t-plot); \({}^{7}\) is the volume of micropores.  
\end{table} 
Table 10: The characterization of the initial catalyst and the catalyst after four reaction cycles. Figure 8: Proposed scheme for the conversion of cellobiose into gluconic and glucaric acids in the presence of the 3% Pt/MN270 catalyst [170]. because they are highly reactive [173; 174]. FF can be produced by sequential hydrolysis and dehydration reactions of xylans that are obtained from biomass. Selective hydrogenation of furfural is important reaction in the production of furfuryl alcohol (FA), methylfuran, tetrahydrorofurfuryl alcohol, and other compounds (Figure 9). Furfuryl alcohol is mainly used for the production of special resins, lubricants, plasticizers, polymers and the coatings based on them, etc. [176]. Considering that FF hydrogenation is a complex multi-stage process that occurs with the formation of a large number of products, the synthesis and selection of a suitable catalytic system is very important. The Pd-containing catalysts based on HPS type MN270 were proposed for the FF hydrogenation. The influence of the precursor nature on the structure, composition, and catalytic properties was studied [177]. Bis(acetonitrile) palladium chloride (PdCl\({}_{2}\)(CH\({}_{3}\)CN)\({}_{2}\)) and palladium acetate (Pd(CH\({}_{3}\)COO)\({}_{2}\)) were used as palladium precursors. All catalysts under study were synthesized via incipient wetness impregnation. The selected Pd (II) precursors have different polarities, which influence their compatibility with HPS and, accordingly, the formation of palladium nanoparticles. The dielectric constants of acetonitrile and acetate are 36.64 and 6.2, respectively [178]. Our previous work [89] showed that HPS is extremely hydrophobic, but due to its unusual porosity and high crosslink density, it can accommodate even completely polar compounds. We believe that the behavior of any compound introduced into a porous matrix depends on its ability to either propagate along the pore walls, when both the matrix and the metal compound have similar properties, or to be repelled from the pore walls (when both are particularly different). This results in particles of different sizes and arrangements depending on the properties of the metal precursor. Therefore, the result depends on the balance of hydrophobicity and hydrophilicity between the metal precursor and HPS [89]. The study using the low-temperature nitrogen physisorption of initial HPS samples and final catalysts showed that the specific surface area of HPS after impregnation with Pd precursors decreased, suggesting pore clogging. It should be noted that the volume of mesopores decreased, while the volume of micropores remained unchanged. These data indicate the formation of palladium nanoparticles in HPS mesopores. Figure 9: Schematic representation of the FF hydrogenation (the target reaction product is highlighted in red). Reprinted from ref. [175], Copyright 2020, with permission from John Wiley and Sons (Hoboken, New Jersey, USA).