Kinetics of aldehyde hydrogenation: Vapor‐phase flow system and supported nickel catalyst

Abstract

A kinetic study of the catalytic vapor-phase hydrogenation of three aldehydes (acetaldehyde, propionaldehyde, and n-butyraldehyde) was made at low conversions with a commercial supported nickel catalyst. A simple initial rate equation was determined and found to agree with a mechanism suggested by the ideal kinetics of Hougen and known experimental evidence. By means of this equation the relative reactivities of the aldehydes were compared and found to agree with the predictions of organic theory. An improved reactor designed to ensure isothermal operation is described.It would seem that experimentation in applied kinetics should have objectives in addition to the determination of a rate equation or apparent mechanism for a particular reaction. It is well known that an experimentally determined rate equation for a reaction over a. given catalyst often has limited usefulness. The kinetic constants are applicable with certainty only for the one catalyst and the range of experimental conditions. It is possible, however, to develop data and concepts of general usefulness from a study of any specific reaction, particularly if certain general objectives are selected during the early stages of a project.The objectives of the work described in this paper are listed below. The criterion for selection was the extent of their contribution to improved methods for the application of kinetics to process design and development. OBJECTIVES1. To determine a rate equation and rate constants for the catalytic vaporphase hydrogenation of aldehydes to the corresponding alcohols by use of a supported nickel catalyst. 2.To determine the relative reactivities of the three aldehydes and the feasibility of correlating kinetic data for members of a family of compounds for engineering purposes.3. To demonstrate an improved experimental reactor, designed to ensure nearly isothermal operation.4. To reemphasize the value of theoretical organic chemistry in establishing rate equations useful for design and in comparing reaction rates of members of a family of compounds. PREVIOUS WORK WITH ALDEHYDESalcohols on an industrial scale, the kinetics of the reaction has received little attention. The fundamental work done thus far, however, has established that the hydrogenation of aldehydes over nickel at temperatures near 150°C.involves addition across the olefinic bond of the enol form (%',S, 7 , l O ) . Palmer (7a), studying the reverse reaction on copper (dehydrogenation of ethyl, n-propyl, and n-butyl alcohols), found the rates and temperature coefficients to be equal.

Reaction Kinetics and Mechanism for the Catalytic Reduction of Propionic Acid over Supported ReOx Promoted by Pd

“…The observed low barrier to hydrogenation of the aldehyde intermediate is not surprising, as hydrogenation reactions of unsaturated CO bonds often have low barriers (see, for example, reduction of aldehydes over Ni catalysts supported on kieselguhr). 40 When the reduction of 1-propanol was studied over PdRe/SiO 2 at a lower temperature, the majority product (>80% selectivity) was propane in all cases, and the apparent barrier to propane formation was 70 kJ mol −1 .…”

Sustainability Assessment of Thermocatalytic Conversion of CO2 to Transportation Fuels, Methanol, and 1-Propanol

“…Due to the lack of process kinetics in the literature, the HFM reactor was modeled using a conversion reactor with 90% conversion of ethylene and 90% selectivity towards the aldehyde. Other reactors were modeled with published kinetic parameters. ,, Energy integration was achieved using pinch analysis…”

“…Other reactors were modeled with published kinetic parameters. 26,28,33 Energy integration was achieved using pinch analysis. 34 Economic Evaluation.…”

Smart Equipment – A Perspective Paper

“…Knowledge consolidation became visible in concise textbooks, such as of Brötz or, with higher emphasis on transport phenomena, of Bird, Stewart, and Lightfood in 1960 . Miniaturization of equipment is visible since 1950 for analytics and catalytic gas phase reactions and got new momentum in the 1990s with monolithic reactors and novel fabrication techniques . More complex equipment arrangement with integrated process steps and functions was possible with improved control strategies from concepts in process systems engineering starting in the 1970s with increasing computational power.…”