Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-V-11reactor we can see that its concentration increases after 4 hours of reaction at WHSV > 4 h –1which means that the catalysts loses selectivity in its oligomerization reaction leading toC 4 -hydrocarbons and liquid products.Water addition to ethanol flow decreases the amount of liquid hydrocarbons formedduring ethanol conversion on ZnO/FeO x /HZSM-5. The conversion of ethanol also decreasesto 90% at 1:5 ethanol-water (e/w) conversion with the increase of diethyl ether concentration.At ratios lover than 1:4 e/w diethyl ether formation was also observed consuming up to 10%of ethanol. The rise of ethylene concentration within 4 hours of reaction has been found withwater concentrations higher than 25%. High concentration of C 4 products means thatoligomerization of ethylene either stops at this stage or leads to C 6 -species which aretransformed to the mixture of C 2 , C 3 and C 4 via cracking routes.In our opinion the main deactivation role of water in this zeolite catalyst is blocking ofactivation site for oligomerization and aromatics production. The high concentration of watermolecules inside the pores of zeolite lowers the acidity of the catalyst and moves adsorbedethylene species from active centers back to gaseous phase before their oligomerization. Inproving this conception it is necessary to mention that after short activation of the catalyst(1hr) in air stream, its properties regenerate almost completely.But if we are concerned with optimizing yields of C 3 -C 4 or ethylene instead of liquidproducts we can conclude that water addition to ethanol plays an important role in changingcatalyst selectivity without altering the catalyst and technological equipement.Table 2. The influence of water on product composition of ethanol conversion onZnO/FeO x /HZSM-5 catalyst (T = 350 °C, P = 1 atm)WHSVethanol,h –1WHSVwater,h –1LiquidHC, %C 2 (1) ,% massC 2 (2) ,% massC 3 (1) ,% massC 3 (2) ,% massC 4 (1) ,% massC 4 (2) ,% mass2 2 2 27 44 21 16 50 352 4 0 44 47 15 15 35 332 6 0 45 60 10 8 18 122 10 0 50 70 22 10 22 104 2 10 25 27 19 17 51 496 2 5 20 50 20 11 55 331) after 1 hour of reaction2) after 4 hours of reaction478