Higher alcohols (C 4 +) can be formed from ethanol via condensation pathways collectively known as Guerbet reactions. Most prior Guerbet reaction studies involve vapor phase reactions, with n-butanol yields typically no higher than 30% of theoretical. We report here condensed-phase Guerbet reactions of ethanol over Ni/γ-Al 2 O 3 catalysts modified by La 2 O 3 .Higher alcohol selectivities in excess of 80% at 230 o C and autogeneous pressures are obtained in batch autoclave reactions. At these conditions, which are near the critical temperature of ethanol, the liquid phase is significantly expanded, byproduct gases (CH 4 and CO 2 ) are significantly dissolved in the liquid phase, and the vapor phase contains significant quantities of alcohols. To accurately compute ethanol conversion and product yields, both composition and quantity of each phase present at reaction conditions must be determined. To do this, the S-R Polar equation of state is combined with chromatographic analysis of liquid phase samples taken during reaction to model the phase equilibrium in the reactor at reaction conditions. Composition, density, and total number of moles of the vapor and liquid phases in the reactor are determined from the model and analysis, and are used to calculate more accurate values of conversion and product yield than those calculated by liquid phase samples alone.

The effect of water on higher alcohol and noncondensable gas formation in condensed-phase ethanol Guerbet chemistry over Ni/La 2 O 3 /γ-Al 2 O 3 catalysts is investigated. Addition of 10 wt % water to anhydrous ethanol has a modest effect on conversion rate but significantly reduces both n-butanol and C 6+ alcohol yields and increases noncondensable gas yields. Removal of water formed during Guerbet condensation reactions was accomplished by installing a recirculating loop that passed the reacting solution through a bed of 3 Å molecular sieves at low temperature. Removal of reaction water further reduces gas selectivity to less than 10% and increases alcohol selectivity to greater than 75% at 50% ethanol conversion. Water present in reaction is postulated to adsorb on the nickel surface as −OH, increasing C−C bond breakage of the adsorbed acetaldehyde intermediate, and also interact with basic sites responsible for the condensation reaction, weakening their activity.