Investigation of synthesis route of unsaturated alcohols in the selective dehydration of diols

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We have recently found that cerium oxide (CeO_2) catalyzed the selective dehydration of 1,3-butanediol into unsaturated alcohols. We purchased equipment of gas chromatography with mass analyzer (GC-MS), Fourier transform infrared spectroscopy (FT-IR), and a soft ware for the calculation of quantum analysis in order to clarify the reaction mechanism for the dehydration of diols into unsaturated alcohols over cerium oxide. The research work has been well developed with the equipment and software introduced in this work.We were able to identify various by-products formed with a small amount in the reaction of diols by using GC-MS. The by-products provide useful information to consider the reaction route. In the model adsorption of 1,3-butanediol on an oxygen-defect site of a Ce_2 surface was investigated with quantum calculations of Density Functional Theory (DFT) and Paired Interacting Orbital (PIO) theory. In the structures optimized with DFT calculation, the two oxygen atoms of the OH … More groups interact with exposed Ce cations at an oxygen-defect site. In the most stable adsorption structure, one hydrogen atom of the 2-position methylene group interacts with the third Ce cation at the oxygen-defect site of the CeO_2(111) surface. In the PIO calculations of 1,3-butanediol-CeO_2(111) systems, the interacting orbitals are clarified. We proposed a reaction mechanism for the dehydration of 1,3-butanediol over CeO_2.We investigated the dehydration of butanediol into unsaturated alcohols over CeO_2 with different particle sizes. The particle size was controlled by the calcination temperature of CeO_2. Catalytic performance in the dehydration of 1,3-butanediol was greatly affected by the particle size. The selectivity to unsaturated alcohols such as 3-buten-2-ol and trans-2buten-1-ol increased with increasing the particle size, while decomposition of 1,3-butanediol into 3-buten-2-one and butanone was catalyzed by CeO_2 with small particles. In the dehydration of 1,3-butanediol, CeO_2 has structure-sensitive catalysis : CeO_2 {111} afacets have active sites for the formation of unsaturated alcohols, and the other surfaces catalyze the side reactions.We have not yet established the observation of adsorption mode of 1,3-butanediol in the FT-IR measurement because of its low volatility. However, in the support of this grant, we have also found that CeO_2, ZrO_2 and several rare earth oxides are effective for the dehydration of 1,4-butanediol into 3-buten-1-ol. Less