Investigations into the conversion of ethanol into 1,3-butadiene

Abstract

In this paper we report the utility of a variety of silica impregnated bi-and trimetallic catalysts for the conversion of ethanol into 1,3-butadiene. The highest selectivity observed was 67%. The catalysts have been characterised via 29 Si solid-state NMR spectroscopy, TEM, XPS, pXRD and nitrogen adsorption studies. Different silica materials have been investigated as supports and there appears to be a relationship between the pore diameter and the selectivity to 1,3-butadiene. When the same metals were impregnated on non-acidic supports the conversion dramatically reduced.

Ethanol to 1,3‐Butadiene Conversion by using ZrZn‐Containing MgO/SiO2 Systems Prepared by Co‐precipitation and Effect of Catalyst Acidity Modification

“…[13,[21][22][23]28] In particular, a synergic effect between ZrO2 and ZnO has been demonstrated. [12,23] ZnO may support ethanol dehydrogenation and ZrO2 is expected to assist aldol condensation and crotonaldehyde reduction. [12,14,23,[28][29][30] Conversely, besides catalyst composition, the catalyst preparation method is of paramount importance for 1,3-BD formation, since different acid-basic features may be obtained depending on synthesis conditions.…”

“…[12,23] ZnO may support ethanol dehydrogenation and ZrO2 is expected to assist aldol condensation and crotonaldehyde reduction. [12,14,23,[28][29][30] Conversely, besides catalyst composition, the catalyst preparation method is of paramount importance for 1,3-BD formation, since different acid-basic features may be obtained depending on synthesis conditions. [18,22,23,31] Due to this, it has been reported different optimum Mg-to-Si molar ratios for 1,3-BD formation, depending on the synthesis procedure employed.…”

“…[9] The route most widely accepted to account for 1,3-BD production from ethanol involves five consecutive reactions. [10][11][12][13][14][15][16] Initially, ethanol is dehydrogenated to acetaldehyde. Then, 3-hydroxybutanal is formed from acetaldehyde self-aldolisation.…”

“…[18,22,23,31] Due to this, it has been reported different optimum Mg-to-Si molar ratios for 1,3-BD formation, depending on the synthesis procedure employed. [13,18,23] Among the catalyst preparation procedures, different methods have been investigated such as physical mixtures of MgO and SiO2, [11,13] wet-kneading, [10][11][12][13]22,23] sol-gel, [18,24] impregnation [13] and co-precipitation. [22,25,26] Whereas it has been proven that a physical mixture between precursor oxides is not suitable for 1,3-BD formation, since resultant catalysts show similar features to single MgO and SiO2 phases, wet-kneading methods have been the most widely discussed in the literature with less attention being dedicated to sol-gel and co-precipitation methods.…”

How well can renewable resources mimic commodity monomers and polymers?

“…88 More recently, bimetallic (Zr:Zn) and trimetallic (Cu:Zr:Zn) catalysts supported on silica produced up to 67% 1,3-butadiene with the remainder being ethylene and acetone. 89 The multistep mechanism initially involves the oxidation of ethanol to acetaldehyde followed by an Aldol reaction that produces acetaldol. Then, this four-carbon molecule undergoes a couple possible dehydration mechanisms before resulting in 1,3-butadiene.…”