Rates of reaction in a recycling system—dehydration of ethanol and diethyl ether over alumina

Abstract

A new method for measuring isothermal rates of heterogeneously catalyzed gas reactions is described. The method involves a differential reactor incorporated in a recycling system and affords ease of control, occuracy, and many rate measurements in one run.The results for the reaction system investigated show that four reactions are important: the dehydration of ethanol to ethylene, the reaction of ethanol to form diethyl ether, the dehydration of diethyl ether to ethylene, and the reaction of diethyl ether to form ethanol.It is also shown that the rate controlling steps are the monomolecular surface reactions for the two dehydrations and for the formation of ethanol from diethyl ether, and the bimolecular surface reaction for the formation of diethyl ether from ethanol. The values and the temperature dependence of all pertinent rate and adsorption constants are determined and reported, and they are shown conversion.The measurement of the isothermal rates of heterogeneously catalyzed gas reactions is ordinarily accomplished directly in differential reactors or indirectly in integral ones. The former is a powerful method but difficulties are met in analyzing small differences in concentration across the short bed. The use of integral conversion data is limited by the necessity to hypothesize a rate equation before interpretation is possible and by the experimental problem of maintaining isothermal conditions in the reactor.A recycling differential reactor, first proposed by Dohse ( 5 ) , affords ease of temperature control, accuracy of analysis, and direct measurement of rates. A new reactor based on Dohse's original idea but extensively improved and modernized has been developed and used in this research. Reactants and products are continuously circulated through the catalyst, and samples of the reaction mixture are withdrawn frequently for analysis. The extent of reaction per pass through the catalyst bed is very small; consequently maintenance of isothermal conditions is not difficult. Conversion data, and thus rate data, are determined at many points in a run from the sample analyses, so increased accuracy of the rate data is assured. A run may be continued until very high conversions are attained; hence it is possible to meas- Page 42to correlate very well the'data up to 80% ure the rates over an unusually wide range of conversion in one run.A somewhat similar device was used by Smith, et al.( 1 3 ) , with considerable success for ion exchange systems. Perkins and Rase (10) and Polotniuk and Dobrovol 'skii (11 ) have reported the use of reactor systems involving recycling operations. These devices however involve recychg the reactants and products in a steady state measurement of rates at a given conversion and are not similar to the system described here.The dehydration of ethyl alcohoI over alumina catalyst was selected for study because such rates have not been well-defined and because a moderately complicated array of simultaneous and consecutive reactions is involved. Diethyl ether is an intermediate, and...

The effect of preparation method on the catalytic activity of amorphous aluminas in ethanol dehydration

“…The shape of our experimental curves in Fig 5, which were identical to those given by De Boer,16 could be explained by the combination of the above two mechanisms. Some explanations of this behaviour have been given by several researchers,17, 18 but it is rather clear that further investigation may be expected to be fruitful only if the range of experimental variables studied (and particularly, of temperature) are greatly expanded.…”

Diethyl Ether Production Process with Various Catalyst Type

“…In this process, ethanol conversion per pass and its yield is 60-80 and 90% respectively [1] . Butt, et al [2] and de Boer, et al [3] , studied kinetic reaction of this process.…”

Kinetics of individual steps in reaction network ethanol-diethyl ether-ethylene-water on alumina

“…Eq. (1) with n = 1 was applied, as well as Eqs (2) and (3) (3) Of the other steps in Scheme I, Butt, Bliss and Walker 3 described the decomposition of ether (steps 3 and 4) by Eq. (4) (j = 3 or 4) (4) Eqs (1) to (4) correspond to simple Langmuir-Hinshelwood models of surface reactions.…”