- CuCr2O4 derived by the sol-gel method as a highly active and selective catalyst for the conversion of glycerol to 2,6-dimethylpyrazine: A benign and eco-friendly process
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Vapour phase dehydrocyclization of crude glycerol in conjunction with 1,2-propanediamine (1,2-PDA) was examined over CuCr2O4 obtained by different preparation methods. A high proportion of copper species interacted with Cr2O3 in CuCr2O4 derived from the sol-gel route with a low ratio of Cu2+/Cu0 demonstrating higher dehydrocyclization activity and 2,6-dimethylpyrazine (2,6-DMP) selectivity. X-ray photoelectron spectroscopy analysis of the reduced CuCr2O4 revealed a lower fraction of ionic Cu and a high percentage of metallic Cu in the near surface region. The HCOOH and pyridine adsorbed DRIFT spectra of CuCr2O4 revealed that strong basic and moderate Lewis acid sites are responsible for the selective formation of 2,6-dimethylpyrazine which is consistent with the catalyst poisoning studies on CuCr2O4 co-feeding with pyridine as both Br?nsted and Lewis acid site blocker and 2,6-lutidine as a selective Br?nsted acid site blocker during the dehydrocyclization reaction. The presence of isolated CuO and Cr2O3 species led to a high selectivity for 2,6-dimethylpiperazine. The high intrinsic activity of CuCrsol-gel was also concomitant with the Cu metal surface areas of the catalysts. The fresh, reduced and some of the used catalysts are characterized by BET-surface area, powder XRD, FTIR, XPS, TEM, H2-TPR, TPD of NH3, pyridine, 2,6-dimethylpyridine and HCOOH adsorbed DRIFT spectroscopy.
- Vankudoth, Krishna,Gutta, Naresh,Velisoju, Vijay Kumar,Mutyala, Suresh,Aytam, Hari Padmasri,Akula, Venugopal
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p. 3399 - 3407
(2017/08/16)
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- The role of Lewis acid-base pair sites in ZnO-ZnCr2O4 catalysts for cyclization: Via dehydrogenative condensation of crude glycerol and 1,2-propanediamine for the synthesis of 2,6-dimethylpyrazine
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Nano-crystalline mixed oxides of ZnO-ZnCr2O4 (ZC) derived from Zn-Cr-HT precursors were examined for the vapor phase dehydrogenative condensation of crude glycerol and 1,2-propanediamine (1,2-PDA) to synthesize 2,6-dimethylpyrazine (1,2-DMP). The nature of the surface active sites is illustrated by BET-SA, XRD, ESR, H2-TPR, TPD of NH3, TEM, XPS, and pyridine and HCOOH adsorbed DRIFT spectroscopy. The role of acid-base sites in the product distribution is discussed using the catalytic activity data under a kinetic regime. The in situ IR studies revealed that the dehydration of glycerol occurs on weak Lewis acid sites and dehydrogenation takes place on strong basic sites on the catalyst surface. A relationship between surface acid-base strength and the 2,6-DMP rate is established.
- Vankudoth, Krishna,Padmasri, A. Hari,Sarkari, Reema,Velisoju, Vijay Kumar,Gutta, Naresh,Sathu, Naveen Kumar,Rohita,Akula, Venugopal
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supporting information
p. 9875 - 9883
(2017/09/18)
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- Synthesis of pyrazinyl compounds from glycerol and 1,2-propanediamine over Cu-TiO2 catalysts supported on γ-Al2O3
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Cu-TiO2 catalysts supported on γ-Al2O 3 are prepared and used in glycerol cyclization with 1,2-propanediamine to produce pyrazinyl compounds including 6-hydroxymethyl-2- methylpyrazine, 5-hydroxymethyl-2-methylpyrazine, 2,6-dimethylpyrazine and 2,5-dimethylpyrazine in a fixed-bed system. It is found that glycerol cylclization with 1,2-propanediamine gave a high total yield of pyrazinyl compounds (>80%) over Cu-TiO2/γ-Al2O3 catalyst, and cyclization was through the reactions between activated 1,2-propanediamine and the intermediates from glycerol dehydration and oxidation. In addition, the regioselectivity of the pyrazinyl compounds was mainly controlled by the steric hindrance of the substrates during the cyclization process.
- Li, Xue,Xu, Cheng-Hua,Liu, Chuan-Qi,Chen, Yu,Liu, Jian-Ying
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p. 751 - 754
(2013/07/26)
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