This work describes research on the isomerization of R(+)-limonene over the Ti-MCM-41 catalyst. The studies showed that the Ti-MCM-41 catalyst is an active catalyst in the isomerization of R(+)-limonene. As a result of the isomerization of this compound, it is possible to obtain α-terpinene, γ-terpinene, terpinolene and p-cymene. Terpinolene is the main product of this process, and p-cymene is formed by the alpha-terpinene, gamma-terpinene and terpinolene dehydrogenation. The aforementioned products are of great practical importance. The most favorable reaction conditions leading to the obtaining of limonene isomerization products is the use of the catalyst in an amount of 15 wt% and the temperature of 160 • C. Depending on whether the desired products are the isomers of limonene (γ-terpinene, α-terpinene and terpinolene) or the product of their dehydroaromatization (β-cymene), it is possible to shorten or extend the reaction time. The method for the isomerization of limonene on the Ti-MCM-41 catalyst makes it possible to obtain a significant yield of both the limonene and p-cymene isomers. Longer reaction time is conducive to obtain larger quantities of other reaction products and less desirable products that constitute impurities (oxidized products and polymeric compounds).Currently, among the mesoporous titanium-silicate catalysts, great attention is paid to the Ti-MCM-41 catalyst. This catalyst can be obtained in a simple way. 1) By the hydrothermal method, crystallization of Ti-MCM-41 in the autoclave from the crystallization gel, 2) by the direct precipitation of Ti-MCM-41 from the crystallization gel at ambient temperature without the crystallization in the autoclave, or 3) by the impregnation of the previously obtained MCM-41 structure with an appropriate titanium source [3]. The first two methods allow the introduction of titanium to the entire catalyst structure (including the pores), while the third method allows the introduction of titanium, only on the surface of this material [4].Materials with MCM-41 structure (including Ti-MCM-41) are mesoporous materials having an ordered, two-dimensional structure with hexagonal pores. The MCM-41 structure resembles a honeycomb. These materials have a narrow pore size distribution (1.8 to 10 nm) that have p6mm symmetry. The size of the pores depends on the synthesis conditions, the composition of the crystallization gel, as well as on the length of alkyl chains of the surfactant used in the synthesis. The specific surface area of these materials is well developed and exceeds 1000 m 2 /g. These types of materials have walls with a thickness of 1 nm, which are made of amorphous silica, and their structure is characterized by a close-range order [5][6][7][8][9]. Thanks to this structure, Ti-MCM-41 materials are used as effective catalysts in the processes of epoxidation, oxidation and isomerization of olefins, e.g., allylic compounds (allyl alcohol [10], diallyl ether [11], allyl-glycidyl ether [12], and allyl chloride [13]) or olefins of natural origin (limonene [...
Abstract:The isomerization of limonene over the Ti-SBA-15 catalyst, which was prepared by the hydrothermal method, was studied. The main products of limonene isomerization were terpinolene, α-terpinene, γ-terpinene, and p-cymene-products with numerous applications. The amount of these products depended on reaction time, temperature, and catalyst content. These parameters changed in the following range: reaction time 30-1380 min, temperature 140-160 • C, and catalyst content 5-15 wt %. Finally, the most favorable conditions for the limonene isomerization process were established: a reaction time of 180 min, temperature of 160 • C, and amount of the catalyst 15 wt %. In order to obtain p-cymene (dehydroaromatization product), the most favorable conditions are similar but the reaction time should be 1380 min. The application of such conditions allowed us to obtain the highest amounts of the desired products in the shortest time.
: The interest in biologically active compounds of natural origin has increased significantly recently. Studies of scientists focuses on the activity of these compounds, as well as their modifications, which allow wide range of use in pharmacology. With the present knowledge and technologies, it is possible to obtain compounds with increased biological activity and targeted acting. Curcuminoids are the main components of turmeric (Curcuma longa L.), a plant from India and South-East Asia. Due to its intense yellow-orange color and pleasant aroma, the powdered rootstalk is widely used in food industry, as natural dye and spice. The chemical compound responsible for the characteristic color of rhizomes of curcuma is 1,6-heptadien-3,5-dione-1,7-bis(4-hydroxy-3-methoxyphenyl) - (1E, 6E) called curcumin. This work aims to characterize curcumin in terms of its structure, therapeutic properties and also as a substrate for the synthesis of valuable derivatives. Knowledge about this relationship based on literature analysis will enable a better understanding of the factors responsible for its biological activity.
The isomerization of limonene over natural the zeolite, clinoptilolite, was studied. The main products of limonene isomerization were terpinolene, α-terpinene, γ-terpinene and p-cymene. These products have numerous applications in the cosmetic, food and pharmaceutical industries. The main parameters affecting limonene isomerization were reaction time, temperature and catalyst content. These parameters varied within the following ranges: reaction time 15–1440 min; temperature 155–175°C; and catalyst content 5–15 wt.%. Terpinolene was obtained after reaction for 60 min at 175°C using 10 wt.% catalyst. p-Cymene was produced using similar conditions as for terpinolene except for a longer reaction time of 1440 min. The use of optimum experimental conditions allowed the greatest amounts of the desired products to be obtained in the shortest time.
This work presents studies on the activity of the Ti-SBA-16 (SBA—Santa Barbara Amorphous) catalyst in the isomerization of limonene and S-carvone. The Ti-SBA-16 catalyst was synthesized by a two-step method: first, the SBA-16 material was produced, and then it was impregnated with the titanium source. The Ti-SBA-16 catalyst was subjected to detailed characterizations by means of instrumental methods: XRD (X-ray Diffraction), UV-Vis (Ultraviolet–Visible) spectroscopy, FTIR (Fourier-Transform Infrared) spectroscopy, SEM (Scanning Electron Microscopy) with EDX (Energy Dispersive X-ray) spectroscopy, and EDXRF (Energy Dispersive X-ray Fluorescence). Both limonene and S-carvone underwent isomerization over the Ti-SBA-16 catalyst. In the isomerization of limonene, the main product was terpinolene, and its highest yield amounted to 39 mol% after 300 min at 170 °C with a catalyst content of 15 wt%. Under these conditions, the conversion of limonene reached 78 mol%. In contrast, the highest yield of carvacrol (65 mol%) was obtained with the catalyst content of 15 wt%, at 200 °C, and with the conversion of S-carvone reaching 79 mol%.
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