Effect of the pretreatment of Fe-silicalite on its activity in the ammoxidation of propane

One-pot synthesis of iron doped mesoporous silica catalyst for propane ammoxidation

“…Very interesting is the comparison of mesoporous materials with microporous Fe-silicalite with concentration of iron 0.48 wt%. This material, as it has been shown previously, 19 showed quite interesting results in the direct ammoxidation of propane, good results were obtained over the sample which was activated in the diluted stream of propane and ammonia. As it is evident from the figure, at a similar conversion of propane, the calcined mesoporous material was more selective than the calcined Fe-silicalite.…”

“…Our previous studies conducted on Fe-silicalites clearly showed that extraction of Fe species from the framework is essential for reaching high catalytic activity in propane ammoxidation. 18,19 Therefore, we deduced that framework Fe atoms cannot act as an active site. We are aware that framework of amorphous mesoporous silica is more flexible than the zeolitic structure which can change the properties of tetrahedral atoms in the framework.…”

“…The acrylonitrile yield of 12% and productivity up to 9.3 mol ACN (kg cat h) −1 at 540 °C was obtained over our best catalyst. 19 This paper reports on the successful synthesis of mesoporous ferrosilicate (Fe-HMS) and its catalytic activity in direct ammoxidation of propane. Such material can benefit from two main advantages (i) as a mesoporous material it should overcome the problems connected with the diffusion, (ii) it contains low amount of strong acid sites even at high concentration of heteroatoms.…”

Structural changes in FeMFI during its activation for the direct ammoxidation of propane

“…Reactions catalyzed by these materials include (i) isomerization and oxidative dehydrogenation of alkanes, [1][2][3] (ii) selective oxidation of benzene to phenol using N 2 O as the oxidant, [4][5][6][7][8][9] (iii) reduction of NO x and N 2 O with hydrocarbons (HC-SCR) or ammonia (NH 3 -SCR), [10][11][12][13][14][15][16][17][18][19] direct N 2 O decomposition [19][20][21][22] and also (iv) direct ammoxidation of propane over differently activated Fe-silicalite in the presence of O 2 or O 2 /N 2 O as the oxidants. [23][24][25] For most of these reactions, the catalytic activity is thought to be related to extraframework iron species (iron oxides or oxohydroxide aggregates) formed by Fe extraction during the post-synthesis thermal treatments 1,2,7,8,[10][11][12]16,19,20,23 and acting either independently or in synergy with protonic RFe(OH)SiR (Brønsted acid) sites. 3,5,11,13,14,17,19,…”

“…[23][24][25] For most of these reactions, the catalytic activity is thought to be related to extraframework iron species (iron oxides or oxohydroxide aggregates) formed by Fe extraction during the post-synthesis thermal treatments 1,2,7,8,[10][11][12]16,19,20,23 and acting either independently or in synergy with protonic RFe(OH)SiR (Brønsted acid) sites. 3,5,11,13,14,17,19,24,25 Post-synthesis thermal treatments can be done either by calcination at high temperatures in air or by treatment in a flow of inert gas (or in a vacuum), but also in water vapor. 22 High temperature treatments of isomorphously substituted zeolites induce the removal of Fe 3+ from the framework to extraframework positions, with subsequent migration and grafting.…”