Reaction Pathways in 1‐Butanol Dehydration on γ‐Alumina

Abstract

ducts are 1-butene, dibutylether and water, and an isomerization reaction leads to 2-butene. experimental parameters like reaction temperature, reactant partial pressure and contact time on the activity of our catalyst.tive phenomenon between direct and consecutive dehydration reactions. 1-Butanol dehydration has been studied on pure Y -A~~O J . Dehydration pro-The aim of this work was to obtain basic information on the influences of We propoae a reaction pathway where the most important fact is a competi- INTRODUCT IONAlcohol dehydration haa been studied since many years (1) and catalytically carried out on aluminas, sulfates and phosphates, aimple (Cr, Si, Ti, Be, Zn, ... ) or mixed metallic oxides (e.g. silica-alumina) and zeolite6 (1,2,3). Ion exchange resins have also been used ( 4 ) .fins and ethers (1). In the case of 1-butanol, dehydration laada to water, 1-butene and dibutylether. In addition, isomerization of 1-butene occurs in parallel along with 1-butanol dehydration and leads to 2-butanes (cis and trans) ( 5 ) . Alcohol dehydration on aluminas gives, as reaction products, water, ole- Olefin formationVarious reaction schemes for alcohol dehydration to olefins have been proposed by authors (2). They are always based on acid-base mechanisms, as shown below on the example of ethanol dehydration.

1-Butanol dehydration in microchannel reactor: Kinetics and reactor modeling

“…This can be explained by the fact that at low partial pressure the molecules occupy far away catalyst sites and due to low concentration of 1-butanol in the bulk, possibility to form dibutyl ether is low (Phung et al, 2014). Similarly if dual site mechanism is considered to form dibutyl ether, it can be postulated that since the molecules are occupied on scattered catalyst sites the possibility of interaction between two adsorbed species at adjacent sites is very low (Berteau et al, 1985). Increasing the partial pressure in turn increases the concentration of butoxy species formed by adsorption of 1-butanol on the active sites.…”

“…3). In the literature some studies for alcohol dehydration Berteau et al (1985) and Decanio et al (1992) have advocated this dual site mechanism. In general two neighboring alkoxy species formed through Lewis acid-base and basic sites on alumina undergo a nucleophilic attack of the Lewis acid-base alkoxide species on positively polarized carbon in basic alkoxide species.…”

“…In the solid phase, internal diffusion and reaction inside the catalyst layer were considered. Walter et al (2005) modeled the cylindrical channel in 2D considering axial convection, dispersion in axial and radial direction for gas-phase, where pseudohomogeneous reaction was considered instead of modeling internal Berteau et al (1985) and Decanio et al (1992). transport. Schmidt et al (2013) developed a steady state 2D model and regarded catalyst layer using a slab geometry.…”

Butanol production from lignocellulosics

“…The reaction conditions and the choice of the catalyst have an effect on the product distribution. The main product is 1-butene, but other butenes (2-butenes, isobutene) are also formed either through an intermediate common in 1-butene formation or via 1-butene isomerization (Macho et al 2001;Berteau et al 1985). There is a thermodynamical equilibrium between the different butene isomers and at these temperatures isobutene is the most favored isomer (Domokos 1973).…”

“…3 Comparison of the widespread prokaryotic fatty acid boxidation pathway and 1-butanol biosynthesis pathway in Clostridium acetobutylicum. Enzymes of E. coli and C. acetobutylicum are indicated by their gene names: atoB acetyl-CoA C-acetyltransferase; fadA (fadI) acetyl-CoA C-acyltransferase; fadB (fadJ) 3-hydroxyacyl-CoA dehydrogenase/ enoyl-CoA hydratase; fade (ydiO) acyl-CoA dehydrogenase; thlA, thlB thiolase (acetyl-CoA acetyltransferase); hbd 3-hydroxybutyryl-CoA dehydrogenase; crt crotonase (3-hydroxybutyryl-CoA dehydratase); bcd butyryl-CoA dehydrogenase (adapted from Gulevich et al 2011) modified aluminum oxides (Shen et al 1990;Macho et al 2001;Makarova et al 1990Makarova et al , 1994Berteau et al 1985;Berteau and Delmon 1989;Zhang et al 2010;Zotov et al 2010). The reaction conditions and the choice of the catalyst have an effect on the product distribution.…”