Dehydration of methanol and tert-butyl alcohol on silica-alumina

Abstract

The catalytic dehydration of tert-butyl alcohol and of methanol has been studied over silicaalumina. Both reactions obey the rate law, v = kupi/(l +u&+bp,).Pyridine, Na+ and tetracyanoethylene poison the dehydration reactions. These results show that the reaction requires both acidic and basic sites. However, the dehydration of tert-butyl alcohol is much more sensitive to the presence of strongly acidic sites then the methanol dehydration. Alumina, which has a basic character, is more active than silica-alumina for methanol dehydration. These experimental results and those previously published in the literature accord with a conventional carbonium ion mechanism for the dehydration of tert-butyl alcohol. A new mechanism which involves a nucleophilic attack by the alcohol molecule is proposed for the dehydration of methanol.

Methanol dehydration to produce dimethyl ether over g-Al2O3

“…(II) was derived as shown in Table 1. The temperature dependence of the equilibrium constant was calculated from thermodynamic data [12] as follows: [2,3], [5,6] Equations (III) − (VI) assume the dissociative adsorption of methanol. Four sites are involved in eqs (III) and (IV) and two sites are involved in eqs (V) and (VI) was suggested by Figueras et al [3] who assumed a carbonium ion mechanism.…”

“…Surface reaction was shown to be the rate-determining step in methanol dehydration, but the methanol adsorption step remains controversial. Dissociative adsorption was proposed by Kalló and Knözinger [2], Figueras et al [3], Klusac and Schneider [4], Rubio et al [5], Schmitz [6], Than et al [7], and Bercic and Levec [8] while the molecular adsorption was assumed by Sinicyan et al [9] and Gates and Johanson [10]. Previous kinetic equations were derived in the temperatures above 300 o C for γ-Al 2 O 3 or below 200 o C for ion exchange resin for DME production by methanol dehydration.…”

Characterization by XRD, DRIFT, and MAS NMR Spectroscopies of a Mg2P2O7Catalyst

“…Some authors associate the dehydration with (Table 3). Conversion decreased with increasing calcination surface acid sites (38) and the dehydrogenation with surface temperature of the solid. These results show that the selectiv-basic sites (39,40).…”

Characterization of Acid–Base Paired Sites on Silica-Supported RuS2by Infrared Spectroscopy and Methyl Mercaptan Condensation Reaction

“…From either IR spectroscopy of kinetic measurements related to alcohol condensation catalyzed by oxides, it is well admitted that the first step of the reaction mechanism is the dissociative chemisorption of the reactant on an acid-base pair (47)(48)(49). This activation process leads to the formation of an alkoxide anion bonded to a surface acid site while the protonic species interacts with a basic oxygen atom of the solid leading to the formation of an OH group.…”