Steam-deactivated catalysts, sodium effect

Effect of Na on Fresh and Steam Deactivated Catalysts Properties of the two USY silica sol catalyst samples, having different method of sodium incorporation, are shown in Table 3. Both samples had similar zeolite and matrix surface areas and zeolite unit cell size after 4 hours at 1088K steaming. 

To determine if we could simulate in the laboratory the effect of sodium on conunercially deactivated FCC catalysts, we prepared catalysts containing Na in the range of 0.22 to 0.41 wt% by modifying the catalyst washing procedure and deactivated the samples at 1088 K fa- 4 hours under 1 atm of steam This steaming procedure is commonly used to prepare deactivated catalysts with physical properties (zeolite and matrix surface areas and unit cell size) that match conunercial Beats. 

Fig. 1. The effect of vanadium and sodium on the physiccil and catalytic properties of steam deactivated e terimental catalysts, (a) mlcropcoe surface area, (b) mesopore surface area, (c) relative zeolite crysteaiinity, and (d) MAT ocnversicn.

Among the several routes to obtain styrene, ethylbenzene del drogenation in the presence of steam is by far the most important one. This reaction is responsible for the global production of more than 90% of this monomer, used as precursor of various resins and polymers [1]. In industrial processes, the reaction is carried out over hematite-based catalysts doped with chromium and potassium oxides which are active and selective but deactivates with time [2], besides being toxic and harmful to the environment. Therefore, a lot of woik has been devoted to find alternative dopants to replace chromium [2-7]. In a previous woik [7], we have found that aluminum is a convenient dopant to replace chromium in hematite-based catalyst for ethylbenzene dehydrogenation. In order to improve the preparation of this solid, a comparison of the effect of sodium caibonate and sodium hydroxide with ammonium Itydroxide on the properties of hematite-based catalysts is done in the present work. The study intends to avoid ammonium hydroxide which is normally used in laboratoiy preparations but is not allowed in commercial preparations due to its toxicity to human and to the environment. 

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