Preparation of cis-pinane via α-pinene hydrogenation in water
Amphiphilic mesoporous silica modified with trimethoxy (3,3,3-trifluoropropyl) silane (TFPS) and (3-aminopropyl) trimethoxysilane (APTS) was prepared by one-step synthesis. The structure and morphology of the mesoporous silica were characterized and confirmed by solid-state nuclear magnetic resonance, X-ray diffraction (XRD), N2 adsorption–desorption, Fourier transfer infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Meanwhile, the thermostability of the amphiphilic mesoporous silica was detected by thermogravimetric (TG) technique. Get more news about cis pinane,you can vist our website!
Highly dispersed Ru nanoparticles supported on such amphiphilic mesoporous silica (marked as Ru/MF@MN) were synthesized by wet impregnation method with the assistance of ultrasonic. The catalyst was characterized by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). In water medium, Ru/MF@MN was used in α-pinene hydrogenation to prepare cis-pinane. Under the optimum reaction conditions (35 °C, 2 MPa H2, 1 h, m (H2O) : m (α-pinene) : m (Ru/MF@MN) = 200 : 60 : 1), 99.9% α-pinene conversion and 98.9% cis-pinane selectivity were obtained. When Ru/MF@MN was recycled six times, the conversion slightly decreased and the selectivity was nearly unchanged.
cis-Pinane is a kind of significant industrial intermediate that is usually applied in medicine, materials and perfume owing to the high activity of its C2–H bond.1–4cis-Pinane is prepared by selective hydrogenation of α-pinene. Traditionally, α-pinene hydrogenation is commonly catalyzed by Pd/C5 or Pt/C,6 but the content of cis-pinane in products is very low. Moreover, carbon deposition or coking tended to occur due to the poor stability of carbon materials when the catalyst was recycled.7 Raney-Ni was also commonly used in the hydrogenation of α-pinene, but the reaction conditions were too harsh.8 When the hydrogenation of α-pinene was catalyzed by RuCl3·3H2O in water (160 °C, 5 MPa, 5 h), the α-pinene conversion could reach 99.7% and the cis-pinane selectivity was 98.3%.9 However, the stability of the catalyst was very poor.
3. Results and discussion
3.1 Synthesis and characterization of mesoporous silica
The water contact angles of four kinds of mesoporous silica were shown in Fig. 1. Interestingly, water contact angles continually increased with an increase in loading of fluorine. The results indicated that the hydrophobicity of mesoporous silica was enhanced. When the content of fluorine increased to 12.5%, the biggest water contact angle was obtained, which meant 12.5%MF@MN had the strongest hydrophobicity. It resulted in poor dispersity of such mesoporous silica in water. While the content of fluorine was 7.5%, the mesoporous silica with better wettability could disperse well in organic-aqueous biphase system. When Ru nanoparticles were supported on 7.5%MF@MN, 98.9% α-pinene was converted to cis-pinane and 99.9% conversion was achieved in water. So 7.5%MF@MN was selected as the optimum amphiphilic mesoporous silica for the following experiments.