Properties and activity of Zn–Ta-TUD-1 in the Lebedev process

Abstract

A zinc and tantalum-containing mesoporous silica catalyst highly active and selective in the Lebedev process has been prepared using the one-pot TUD-1 methodology. Characterization established a correlation between acidity and butadiene formation.

MgO−SiO2 Catalysts for the Ethanol to Butadiene Reaction: The Effect of Lewis Acid Promoters

“…If this activity change is not paralleled by increased aldol condensation activity acetaldehyde intermediate accumulate on the surface and appears in the product mixture in higher concentration. This phenomenon was demonstrated by the study of Pomalaza et al [30] . The metal oxide additives, used in present study, had the positive effect on the BD yields in the order Zn>In>Ga.…”

“…The Lebedev-process [3] where the ethanol is converted to BD over mixed oxide catalyst, like MgOÀ SiO 2 or ZnO-Al 2 O 3 , and the process of Ostromislensky [4] where a mixture of ethanol and acetaldehyde is reacted over alumina or clay catalysts. Recently, different oxides, mixed oxides, and zeolite supported catalysts, such as, SiO 2, [5][6][7][8] SiO 2 -ZrO 2, [9] zeolite Beta, [10] and MgOÀ SiO 2 [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] promoted with metals and/or metal oxides, such as oxides of Zn, [8,9,17,24,25,27] Ag, [10,27,28] Cu, [10,27] Au, [11] and Ga, [15,29] and metal combinations, like Zn-Hf, [5] Zn-Ta [7,30] and Zn-Zr [13,23,26] have been reported to be active in the ETB process.…”

Ethanol-to-butadiene: the reaction and its catalysts

“…An explanation for the trend observed when comparing the performances of silicasupported group 4 and 5 transition metals in the Ostromislensky process has yet to be found, as no correlation was found with intrinsic acid strength, one possibility being the difference in electronic properties of each metal. Direct correlations between the number of Lewis acid sites and the butadiene formation rate have been reported; 103,130,161,217,227 however excessive Lewis acid site concentration appears to be detrimental by favoring side reactions. 176 Furthermore, not all Lewis acid sites perform equally: Ivanova et al identified the ideal active sites as "open" isolated metal atoms in tetrahedral positions of the zeolite crystalline structure due to their enhanced steric accessibility and greater acid strength.…”

“…Foam-like mesoporous silica was also used by the present authors as a carrier for a highly active Zn-Ta catalyst for the Lebedev process. 103,227 Using the TUD-1 methodology with tetraethylene glycol as both the chelating and structuring agent, metal incorporation was included during the sol-gel step of the silica synthesis. The Zn-Ta-TUD-1 catalyst achieved a butadiene selectivity of 63% in spite of a high ethanol flow rate (8 h −1 ) resulting in the highest butadiene productivity reported for the Lebedev process (Table 4, entry 14), which was attributed to the morphological properties of the catalyst and the high dispersion of the active phase.…”

Recent Advances in Catalysts for the Conversion of Ethanol to Butadiene

“…A linear correlation was found for the initial butadiene yield and the number of Lewis acid sites as quantified by pyridine FTIR. [117] At higher metal loading, a homogeneous dispersion could not be achieved, resulting in a lower Lewis acid concentration and reduced BD productivity. Both KIT-6 and SBA-15 were explored as supports by Ahn et al for ZnÀ Zr mixed oxides.…”