The ACA selectivity practically does not change in the whole range of ethanol conversion and comes to 0.15–0.3% (Fig. 2c), while the butylenes selectivity increases profoundly at higher ethanol con- version (Fig. 2d). The temperature increase from 375 to 450 ◦ C leads to the growth of the ethylene selectivity because of the increase of the ethylene rate formation through DEE as an intermediate. How- ever, at high temperatures the amount of by-products, especially butylenes, is enhanced because of the ethylene dimerization (Fig. 2c and d).
Experiments have shown the inhibition effect of water con- centration in inlet mixture on the rate of ethanol dehydration and the ethylene yield. Water causes the increase in selectiv- ity to butylenes and the decrease in selectivity to ethylene. It is clear from Figs. 3 and 4 that the effect of water on the ethy- lene selectivity is more pronounced at temperatures higher than
375 ◦ C.
The following important observations have been made from the experimental results: the optimal operation conditions providing the maximal ethylene yield are: (1) the highest concentra- tion of ethanol in inlet reactant mixture, no less than 94 wt.%; (2) the temperature range of the process carrying out within
370–400 ◦ C.