Effect of Preparation Method and CuO Promotion in the Conversion of Ethanol into 1, 3‐Butadiene over SiO2–MgO Catalysts. Issue 9 (14th July 2014)

• Record Type: Journal Article
• Authors: Angelici, Carlo; Velthoen, Marjolein E. Z.; Weckhuysen, Bert M.; Bruijnincx, Pieter C. A.
• Is Part Of: ChemSusChem. Volume 7:Issue 9(2014:Sep.)
• Page Start: 2505
• Page End: 2515
• Publication Date: 2014-07-14
• Subjects: Green chemistry -- Periodicals; Sustainable engineering -- Periodicals; Chemistry -- Periodicals; Chemical engineering -- Periodicals; 660
• DOI: 10.1002/cssc.201402361
• Languages: English
• ISSNs: 1864-5631

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Silica–magnesia (Si/Mg=1:1) catalysts were studied in the one‐pot conversion of ethanol to butadiene. The catalyst synthesis method was found to greatly influence morphology and performance, with materials prepared through wet‐kneading performing best both in terms of ethanol conversion and butadiene yield. Detailed characterization of the catalysts synthesized through co‐precipitation or wet‐kneading allowed correlation of activity and selectivity with morphology, textural properties, crystallinity, and acidity/basicity. The higher yields achieved with the wet‐kneaded catalysts were attributed to a morphology consisting of SiO<sub>2</sub> spheres embedded in a thin layer of MgO. The particle size of the SiO<sub>2</sub> catalysts also influenced performance, with catalysts with smaller SiO<sub>2</sub> spheres showing higher activity. Temperature‐programmed desorption (TPD) measurements showed that best butadiene yields were obtained with SiO<sub>2</sub>–MgO catalysts characterized by an intermediate amount of acidic and basic sites. A Hammett indicator study showed the catalysts' p<italic>K</italic><sub>a</sub> value to be inversely correlated with the amount of dehydration by‐products formed. Butadiene yields could be further improved by the addition of 1 wt % of CuO as promoter to give butadiene yields and selectivities as high as 40 % and 53 %, respectively. The copper promoter boosts the production of the acetaldehyde intermediate changing the rate‐determining step of the process. TEM‐energy‐dispersive X‐ray (EDX) analyses showed CuO to be present on both the SiO<sub>2</sub> and MgO components. UV/Vis spectra of promoted catalysts in turn pointed at the presence of cluster‐like CuO species, which are proposed to be responsible for the increased butadiene production.</p> </abstract>