Ethanol Conversion to 1,3-Butadiene on ZnO/MgO–SiO2 Catalysts: Effect of ZnO Content and MgO:SiO2 Ratio

Abstract

Effect of ZnO on ethanol conversion to 1,3-butadiene (BD) on ZnO/MgO-SiO 2 catalysts consists in the enhancement of selectivity and yield of BD due to higher rate of ethanol dehydrogenation to acetaldehyde. It has been shown that two types of Lewis acid sites formed in the contact zones of MgO-SiO 2 and ZnO-SiO 2 in the catalysts play an important role in BD synthesis from ethanol. The highest BD yield is achieved at ratio of MgO:SiO 2 = 1:1. Graphical Abstract

Ethanol/acetaldehyde conversion into butadiene over sol–gel ZrO2–SiO2catalysts doped with ZnO

“…Meanwhile, the selectivity to dehydration products remains high and the catalysts show a relatively poor durability on the long-time stability test. As reported, 5,10,[17][18][19] the addition of promoters into MgOSiO 2 system would be benecial for elevating BD selectivity as well as prolonging catalyst life.…”

“…However, as we can see, the temperature of NH 3 desorption peaks were shied to higher values, implying a relatively higher strength of acidity resulted from large amount of ZnO (bulk crystal) in the ZrO 2 -SiO 2 system, as revealed in XRD patterns and TEM images. In conclude, the importance of acid properties has been revealed in former literatures, 17,18 but few systematic study has been conducted as to the relevance and weight between the quantity and strength of acidity in ZrO 2 -SiO 2 catalytic system. Combining the results of the NH 3 -TPD with catalytic performances of catalysts in this work, we predicted boldly that the strength of acidity was more important than quantity of acidity as to improving catalytic performance.…”

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

“…For instance, the addition of metals and/or metal oxides based on Cu, Zr, Zn and Ag to the MgO-SiO2 system has been shown to be beneficial to 1,3-BD yield. [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.…”

“…[12,23] 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.…”

Recent Breakthroughs in the Conversion of Ethanol to Butadiene

“…Condensation of acetaldehyde with the carbanion leads to the synthesis of crotyl alcohol which dehydrates into butadiene over acid sites (Figure 3, steps 3 and 4). Over bare magnesium-silica, the rate-limiting reaction is thought to be the dehydrogenation of ethanol [24,31,52]. It explains the observed low productivity of butadiene over these catalysts (Table 1).…”