Abstract
Titanium-containing mesoporous silica catalysts with different Ti contents were prepared by the sol–gel method, whereby the molar ratios of silicon to titanium in the crystallization gel amounted to, respectively, 40:1, 30:1, 20:1 and 10:1. The produced Ti-MCM-41 materials were characterized by the following instrumental methods: XRD, UV-Vis, FT-IR, SEM, and XRF. Textural parameters were also determined for these materials by means of the N2 adsorption/desorption method. The activities of these catalysts were investigated in the α-pinene isomerization process. The most active catalyst was found to be the material with the molar ratio of Si:Ti equal to 10:1, which contained 12.09 wt% Ti. This catalyst was used in the extended studies on the α-pinene isomerization process, and the most favorable conditions for this reaction were found to be temperature of 160 °C, reaction time of 7 h, with the catalyst composition of 7.5 wt% relative to α-pinene. These studies showed that the most active catalyst, at the best reaction conditions, allowed for the attainment of 100% conversion of α-pinene over a period of 7 h. After this time the selectivities (in mol%) of the main products were as follows: camphene (35.45) and limonene (21.32). Moreover, other products with lower selectivities were formed: γ-terpinene (4.38), α-terpinene (8.12), terpinolene (11.16), p-cymene (6.61), and α-phellandrene (1.58).
Highlights
Porous materials [1] have found applications in many fields, e.g., in catalysis [2], nanotechnology [3], medicine [4], in processes of liquid and gaseous sewage treatment [5], and in separation of mixture components [6]
The studies show that Ti-MCM-41 catalysts are active in the α-pinene isomerization process, and that the increase in titanium content introduced into the silica structure significantly increases
On the basis of the tests carried out, it was shown that the most active catalyst was the one with a specific high content (Si):Ti molar ratio of of 10:1 in the crystallization gel, which contains 12.09 wt% Ti
Summary
Porous materials [1] have found applications in many fields, e.g., in catalysis [2], nanotechnology [3], medicine [4], in processes of liquid and gaseous sewage treatment [5], and in separation of mixture components [6]. Until the 1990s, the most commonly used materials in these fields were molecular sieves, especially zeolites. One of the few disadvantages of zeolites is their small pore diameter. The need to solve this problem prompted researchers to look for materials with a regular structure, such as zeolites, but with a larger pore diameter [7]. A breakthrough in this field occurred in 1990, when two independent research teams produced mesoporous silica with a strictly defined internal structure. Yanagisawa et al, using layered kanemite and surfactants, obtained mesoporous silica FSM-16 (folding sheet materials using C16 surfactant), which had excellent structural features [8]
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