## 3 Results and Discussion  
### Preparation of Magnetically Separable Quasi-Homogeneous Base Catalysts  
As shown in Scheme 1, two base catalysts functionalized with a trimethoxysilane group were anchored to the magnetite nanoparticles by a condensation reaction under basic conditions between the trimethoxysilane group and the hydroxyl groups existing on the surface of the magnetite nanoparticles. The first base catalyst, 1-(2-(dimethylamino)ethyl)-3-(3-(trimethoxysil)propyl)urea, contains tertiary amine groups and was prepared by the reaction of 3-isocyanatopropyl(trimethoxy)silane and \(N\),_N_-dimethylylethanolamine. The second base catalyst, _N_-[3-(trimethoxysil)propyl]ethylenediamine, contains primary and secondary amine groups. **Scheme 1**. Supporting different base catalysts on the surface of magnetite nanoparticles  
After supporting the base catalysts on the magnetite nanoparticles the resulting materials **MNP-NMe2** and **MNP-NH2** were characterized by Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), thermogravimetric analysis-differential thermal analysis (TGA-DTA) and infrared (IR) methods. The results of the TEM analysis (Figure 1) show that the average size of **MNP-NMe2** and **MNP-NH2** lies in the range of 10-15 nm. The shape of the magnetite nanoparticles modified with amine groups is spherical in both cases. In addition, TEM analysis confirms that a silica shell is not constructed on the surface of the magnetite nanoparticles even though the silane monomers were added in large excess. This result is also confirmed by XRD analysis (Figure 2) that shows just characteristic peaks of magnetite nanoparticles at 2\(\theta\) = 30.1\({}^{\circ}\), 35.5\({}^{\circ}\), 43.3\({}^{\circ}\), 53.6\({}^{\circ}\), 57\({}^{\circ}\) and 62.6\({}^{\circ}\). These peaks are attributed respectively to (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) phases of a cubic unit cell. The loading of the amine groups in the magnetically separable base catalysts was determined by TGA analysis that was performed under air atmosphere. This analysis shows that **MNP-NH\({}_{2}\)** contains about 0.46 mmol/g amine groups while **MNP-NMe\({}_{2}\)** contains about 0.63 mmol/g amine groups. Figure 3(a) shows TGA-DTA curves of the catalysts **MNP-NH\({}_{2}\)**. The DTA curve contains four distinct derivative peaks, which correspond to four mass losses in the TGA curve. Between 80  
Figure 1: Transmission Electron Microscopy (TEM) micrographs of base catalysts supported on magnetite nanoparticles: (**a**) **MNP-NH\({}_{2}\)**, scale bar 100 nm; (**b**) **MNP-NMe\({}_{2}\)**, scale bar 100 nm. Figure 2: Powder X-ray Diffraction (XRD) patterns of base catalysts supported on magnetite nanoparticles. there is an endothermic peak which belongs to desorption of volatile organic solvents and the percentage of the mass loss is 1.3%. At temperatures of 186 \({}^{\circ}\)C and 294 \({}^{\circ}\)C there are two exothermic peaks accompanied with mass loss of 4.5%, the first peak most likely corresponds to the decomposition of the amine groups and the second peak corresponds to the decomposition of the entire organic groups. The exothermic peak at 737 \({}^{\circ}\)C most probably corresponds to a phase transition in which magnetite is converted to FeO. This phase transition is accompanied by a mass loss of 1.1%. The TGA-DTA curves of **MNP-NMe2** (Figure 3(b)) show four steps of mass loss. The first mass loss of 2.7% at 80 \({}^{\circ}\)C takes place because of desorption of volatile organic solvents. The decomposition of the organic groups supported on the magnetite nanoparticles occurs at temperatures of 305 \({}^{\circ}\)C and 401 \({}^{\circ}\)C. In this case, the mass losses for the degradation of the organic groups are about 10.9%.