## 4 HPS-Based Catalysts for the Synthesis and Transformation of Platform Chemicals
### Hydrolytic Oxidation of Cellobiose to Glucaric Acid  
Glucaric acid is an important platform compound used to produce detergents, polymers, and other valuable products [163; 164; 165]. The glucaric acid market is constantly growing and should reach USD 1.46 billion by 2027 [166]. Currently, glucaric acid is obtained by chemical oxidation of glucose with nitric acid, which is a non-selective, expensive, and environmentally hazardous process [167]. Another option for the synthesis of glucaric acid is oxidation using heterogeneous catalysts through the stage of formation of glucaric acid. The main disadvantage of the existing methods for producing glucaric acid is the use of mono- and disaccharides as raw materials, which have nutritional value (glucose and sucrose). In this regard, plant biomass, which has no nutritional value, is an ideal raw material for the synthesis of acids [168]. [PERSON] et al. [169] conducted a feasibility study for the production of pure glucaric acid from corn stover by two methods: homogeneous oxidation of glucose with nitric acid and oxidation of glucose with air in the presence of heterogeneous catalysts. The study showed that both options can be economically feasible for industrial use since the costs per 1 kg of product were 2.91 and 2.53 US dollars for homogeneous and heterogeneous oxidation. However, the process using heterogeneous catalysts has about 22% lower environmental impact. In this case, the main problem is the selection of a stable catalyst, which should present a high yield of glucaric acid. Previously reported results on the HPS-based catalysts for the oxidation of monosaccharides [87; 95] suggested that such catalytic systems can be successively applied for producing alolonic and alolaric acids directly from plant biomass. For this purpose, our group synthesized a series of catalysts based on hypercrosslinked polystyrene MN270 containing Pt, Pd, Au, and Ru. The synthesized catalysts were characterized and tested in the conversion of cellobiose to glucaric acid [170]. The synthesis of these catalysts was carried out according to the method given in paragraph 4.1 of this review. The precursors were ruthenium (IV) hydroxochloride, hydrogen hexachloroplatinate (IV) hydrate, sodium tetrachloropalladate (II), and gold (III) chloride hydrate (pure; OJSC Aurat, Moscow, Russia). Thus, using the appropriate precursors, 3% M/MN270 catalysts were synthesized (M = Pt, Pd, Au, Ru). Tables 7 and 8 present the results of X-ray fluorescence analysis and of low-temperature nitrogen adsorption used to characterize the synthesized catalysts. The elemental analysis data (Table 7) for metal content had values close to the calculated ones, which indicates the consistency of the method used for the synthesis of HPS-based catalysts. From the data in Table 8, it follows that the samples had predominant microporosity with a highly developed internal surface. After introducing metal nanoclusters into the polymer matrix, a change in its characteristics was observed. The specific \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Catalyst**} & \multirow{2}{*}{**S\({}_{\text{m}}\), \%**} & **Specific Catalytic Activity** & **Specific Catalytic Activity** \\  & & **Calculated as Mass of** & **Calculated as Mass of** \\  & & **Catalyst-h\({}^{-1}\)** & **Mannitol/Mass of Ru-h\({}^{-1}\)** \\ \hline
5\% Ru-Fe\({}_{3}\)O\({}_{4}\)/SiO\({}_{2}\) & 44.3 & 2.53 & 50.67 \\
3\% Ru-Fe\({}_{3}\)O\({}_{4}\)/MN270 & 48.7 & 2.78 & 92.76 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Selectivities (S\({}_{\text{m}}\)) and catalytic activities for mannitol production. surface area decreased due to blockage of micro-, meso- and macropores by nanoparticles of the active phase. At the same time, the microporous nature of all samples was preserved. The synthesized catalysts were characterized via transmission electron microscopy (TEM). The images and the average diameters of metal clusters were obtained (Figure 7).