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Oxidative cleavage of carbon–carbon double bonds (C═C) in alkenes and fatty acids produces aldehydes and acids valued as chemical intermediates. Solid tungsten oxide catalysts are low cost, nontoxi...

Ce-incorporated MoVTeNbO catalysts were developed to enhance ethylene productivity of oxidative dehydrogenation of ethane (ODHE) to ethylene. Structural characterizations (XRD, TEM, STEM, Raman, and UV–vis DRS) and DFT calculations revealed that Ce atoms were incorporated into MoVTeNbO framework with maintaining its unique structure (M1 phase), which is active phase for ODHE. The reducibility of the catalysts was enhanced and both V5+ and the lattice oxygen species available to ODHE reaction were enriched by incorporation of Ce, confirmed by TPR, XPS, and pulse injection method, respectively. These improved properties enhanced the conversion of ethane while maintaining their excellent selectivity to ethylene for MoVTeNbCeO catalysts. It is noteworthy that 56.2% of ethane conversion and 95.4% of ethylene selectivity were retained for 200 h over MoVTeNbCeO-0.1 catalyst. Ethylene productivity was calculated to be 1.11 kgC2H4/kgcat h. The developed catalyst exhibits substantial level of ethylene productivity and stability having the possibility with low production of COx to make a step forward for industrialization of oxidative dehydrogenation of ethane.

Si-(OH)-Al groups of amorphous aluminosilicate have been known to play important roles in acid-catalyzed reactions. However, there is a lack of theoretical understanding on the catalytic function of the acid sites and reaction mechanisms on the amorphous aluminosilicate surface. In this study, the preferred glycerol dehydration mechanism on Si-(OH)-Al sites was investigated via density functional theory calculation, and compared to experimental results. An amorphous aluminosilicate surface was constructed based on the β-cristobalite crystal structure, and adsorption and activation energies were calculated for each elementary step in the glycerol dehydration at Si-(OH)-Al sites. It was found that when the primary OH group of glycerol is adsorbed on Bronsted proton (Si-(OH)-Al sites), the adsorption strength is too strong to convert to acetol. On the other hand, the secondary OH group of glycerol is adsorbed with a relatively moderate strength at the acid site, which then leads to favorable production of 3-hydroxypropionaldehyde (3-HPA). Consequently, the 3-HPA is readily dehydrated into acrolein and water due to its reactive properties. Therefore, glycerol seemed to be preferentially converted into acrolein on amorphous aluminosilicate during dehydration. In order to verify the preferential formation of acrolein, catalytic activity test was experimentally conducted. The amorphous aluminosilicate catalyst exhibited remarkable selectivity for acrolein (46.5%), which supported our theoretical approach. In addition, the adsorbed and polymerized glycerol on the used catalyst surface was identified via 13C NMR. This suggests that when glycerol is too strongly adsorbed, it can be transformed into coke during dehydration. Combining our theoretical and experimental observations, it was concluded that strongly adsorbed glycerol gives rise to not only a lower level of conversion but also coke deposition on the amorphous aluminosilicate surface. Comparative investigation of aluminosilicate and H-ZSM-5 zeolite gave new light on that the adsorption structure, adsorption energy, and reaction mechanism are altered by silanol groups on the aluminosilicate surface, although the active site (Si-(OH)-Al) of aluminosilicate is similar to that of H-ZSM-5 zeolite.

The production of di-n-butyl-ether (DNBE), for use as a blending agent in diesel fuel, is very attractive because the reactant (n-butanol) can be readily produced by the fermentation of bio-derivatives. The dehydration of n-butanol is known to show diffusion-limited characteristics on porous catalysts, such as zeolites or mesoporous supported catalysts. In order to overcome this limitation, herein, we synthesized silica spheres (DSS) with three-dimensional (3D) open pores by a hydrothermal reaction for use as a catalyst for the dehydration of n-butanol. In addition, supported heteropolyacid (PW) catalysts were also prepared on various porous silicas, DSS, SBA-15 and microporous silica (mi-S), to investigate the effect of 3D pore structures on the conversion of n-butanol to DNBE against 2D mesoporous and microporous materials by quantitative calculation. PW/DSS showed the best performance among the catalysts at various temperatures (453, 473, and 493 K). The extent of catalytic performance enhancement was quantified by calculating the effectiveness factor ( η ) based on kinetics data. The η values for PW/DSS, PW/SBA, and PW/mi-S were determined to be 0.83, 0.63 and 0.52, respectively.