Abstract
The synthesis of dimeric products from monoterpene hydrocarbons has been studied for the development of renewable high-density fuel. In this regard, the conversion of α-pinene in turpentine over stannic chloride molten salt hydrates (SnCl4·5H2O) as a catalyst was investigated, and the reaction products were analyzed with gas chromatography/flame ionization detector/mass spectrometer (GC/FID/MS). Overall, the content of α-pinene in a reaction mixture decreased precipitously with an increasing reaction temperature. Almost 100% of the conversion was shown after 1 h of reaction above 90 °C. From α-pinene, dimeric products (hydrocarbons and alcohols/ethers) were mostly formed and their yield showed a steady increase of up to 61 wt% based on the reaction mixture along with the reaction temperature. This conversion was thought to be promoted by Brønsted acid activity of the catalyst, which resulted from a Lewis acid-base interaction between the stannic (Sn(IV)) center and the coordinated water ligands. As for the unexpected heteroatom-containing products, oxygen and chlorine atoms were originated from the coordinated water and chloride ligands of the catalyst. Based on the results, we constructed not only a plausible catalytic cycle of SnCl4·5H2O but also the mechanism of catalyst decomposition.
Highlights
Aspirations for alternative biofuel have emerged vigorously worldwide, amid increasing concern about fossil fuel sustainability and environmental pollution
As previously mentioned in the introduction, what we have expected was that the Lewis acid-assisted Brønsted acidic nature of stannic chloride molten salt hydrates (SnCl4 ·5H2 O) would work as a catalyst
We focused on a plausible mechanism involving interaction between α-pinene and in Scheme between α-pinene andthe thecatalyst, catalyst,which which is is shown shown in Scheme plausiblecatalytic catalyticcycle cycleof of SnCl synthesis of of limonene
Summary
Aspirations for alternative biofuel have emerged vigorously worldwide, amid increasing concern about fossil fuel sustainability and environmental pollution In this respect, cellulosic biomass-derived chemicals such as furfural, 5-hydroxymethylfurfural, 2-methylfuran, levulinic esters, and angelica lactone have attracted considerable attention as renewable resources for the sustainable production of biofuels [1,2,3]. Cellulosic biomass-derived chemicals such as furfural, 5-hydroxymethylfurfural, 2-methylfuran, levulinic esters, and angelica lactone have attracted considerable attention as renewable resources for the sustainable production of biofuels [1,2,3] Another promising renewable chemical in order to produce synthetic fuel is turpentine. The decomposition of the catalyst results in oxygen-containing or chloride-containing products To overcome this limitation and ponder the improvement of the reaction system, we have discussed the mechanism of the catalytic conversion of α-pinene over SnCl4 ·5H2 O
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