## 4 HPS-Based Catalysts for the Synthesis and Transformation of Platform Chemicals
### Magnetic Catalysts Based on HPS in the Conversion of Plant Polysaccharides
In this regard, development of highly selective catalytic system seems to be rather difficult [148]. The magnetic support (Fe\({}_{3}\)O\({}_{4}\)/MN270) for the Ru-based catalyst was synthesized using the following procedure. FeCl\({}_{3}\) was dissolved in 95% ethanol. HPS powder (diameter < 45 microns) was put into the solution in the ratio of 1 g HPS per 2 g FeCl\({}_{3}\), mixed thoroughly and left for 10-15 min. Then sodium acetate was added to this mixture in an amount corresponding to the FeCl\({}_{3}\)/CH\({}_{3}\)COONa ratio of 1/1.5. The mixture was dried until ethanol was completely removed. The resulting red-brown powder was moistened with ethylene glycol, placed in a quartz tube and purged by argon. Then, it was heated up to 300 \({}^{\circ}\)C and kept in an argon flow for 5 h. The synthesized Fe\({}_{3}\)O\({}_{4}\)/MN270 powder was washed several times with water, then with ethanol, separated from the solvent with a magnet, and dried to constant weight in an oven at 70 \({}^{\circ}\)C in ambient air. The synthesis of 3% Ru-Fe\({}_{3}\)O\({}_{4}\)/MN270 catalyst was carried out using a procedure described in paragraph 4.1 of this review. Special attention has been paid to the optimization of magnetite particle formation inside HPS pores. Thus, the use of iron (III) nitrate as a precursor [149], turned out to be harmful for the porous structure of HPS (see Table 4). We attributed this result to the formation of strong oxidants during the thermal destruction of nitrate (4 Fe(NO\({}_{3}\))\({}_{3}\)\(\rightarrow\) 2 Fe\({}_{2}\)O\({}_{3}\) + 12 NO\({}_{2}\) + 3O\({}_{2}\)). The table data show that the specific surface area  
Figure 3: Scheme of the cellulose hydrogenolysis to glycols [107]. of such a sample (Entry 3) is about 50-fold smaller as compared to the sample synthesized using FeCl\({}_{3}\) (Entry 2) as a precursor. It has been shown that the sequential introduction of iron and ruthenium oxides (Entry 4) into the HPS support, the SSA (BET) decreases from 1075 to 364 m\({}^{2}\)/g. Although the proportion of pores with a diameter <6 nm decreases slightly, the samples retain their micro/mesoporous character. Therefore, co-impregnation by iron (III) chloride and CH\({}_{3}\)COONa was used for the synthesis of Fe\({}_{3}\)O\({}_{4}\)/MN270 composites. The reactions occurring during the synthesis process can be represented as follows:  
\[\text{FeCl}_{3}+3\text{CH}_{3}\text{COONa}=\text{Fe}(\text{CH}_{3}\text{COO})_{ 3}+3\text{NaCl}.\]  
As a result of the exchange reaction, Fe(CH\({}_{3}\)COO)\({}_{3}\) is formed in the pores of HPS. It is important to use 95% ethanol as a solvent to prevent hydrolysis of the resulting iron acetate. In the case when hydrolysis does not occur, the subsequent reaction of thermal decomposition of acetate at 300 \({}^{\circ}\)C takes place [150]:  
\[6\text{Fe}(\text{CH}_{3}\text{COO})_{3}\to 2\text{Fe}_{3}\text{O}_{4}+9 \text{CH}_{3}\text{COCH}_{3}+9\text{CO}_{2}+\text{\text{\text{\text{\text{ \text{\text{\text{\text{\text{\text{\text{\text{  
Powder X-ray diffraction data confirmed the magnetite particles formation. The XRD pattern of Fe\({}_{3}\)O\({}_{4}\)/MN270 displays sharp Bragg reflections whose intensity and positions are typical for magnetite (Figure 5). X-ray fluorescence analysis of the 3% Ru-Fe\({}_{3}\)O\({}_{4}\)/MN270 catalyst gave an Fe content of 19.6 wt.%, and a Ru content of 2.7 wt.%. Based on TEM results, the mean diameter of Ru nanoparticles of 2.0 \(\pm\) 0.5 nm and magnetite particles of 40 \(\pm\) 5 nm was determined. The synthesized catalyst was used in the hydrogenolysis of microcrystalline cellulose under optimal reaction conditions [149]: 255 \({}^{\circ}\)C; 60 bar H\({}_{2}\); 55 min; 0.3 g of cellulose; 0.07 g of catalyst; 30 mL H\({}_{2}\)O; and 0.195 mol of Ca(OH)\({}_{2}\) per 1 mol of cellulose.