Steam-deactivated catalysts, sodium

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. 

Different procedures can be used in practice to activate the zeolite, and the choice of a particular method will depend on the catalytic characteristics desired. If the main objective is to prepare a very active cracking catalyst, then a considerable percentage of the sodium is exchanged by rare earth cations. On the other hand, if the main purpose is to obtain gasoline with a high RON, ultrastable Y zeolites (USY) with very low Na content are prepared. Then a small amount of rare earth cations is exchanged, but a controlled steam deactivation step has to be introduced in the activation procedure to obtain a controlled dealumination of the zeolite. This procedure achieves a high thermal and hydrothermal stability of the zeolite, provided that silicon is inserted in the vacancies left by extraction of A1 from the framework (1). The commercial catalysts so obtained have framework Si/Al ratios in the... 

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. 

The process of removing water-soluble salts from an oil stream is called oil desalting. Nearly all crude oil is produced with some entrained water, which normally contains dissolved salts, principally chlorides of sodium, calcium, and magnesium. The majority of the produced salt water is removed in the separation and treating process. However, a small amount of entrained water remains in the crude oil. The crude oil is sent to the refinery where it is heated as part of the various refinery processes. The entrained water is driven off as steam. However, the salts in the water does not leave with the steam but crystallizes and remains suspended in the oil or may deposit as scale within heat exchange equipment. In addition, entrained salt crystals will usually deactivate catalyst beds and plug downstream processing equipment. 

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.

Vanadium and sodium neutralize catalyst acid sites and can cause collapse of the zeolite structure. Figure 10-5 shows the deactivation of the catalyst activity as a function of vanadium concentration. Destruction of the zeolite by vanadium takes place in the regenerator where the combination of oxygen, steam, and high temperature forms vanadic acid according to the following equations ... 

In a series of experimental runs on virgin commercial catalysts and sieves then available and some of our experimental catalysts, we quickly learned that a catalyst impregnated with vanadium, and subjected to high temperatures in steam and air deactivated rapidly. Vanadium, especially in the +5 valence state, rapidly deactivated a catalyst by destroying zeolite crystallinity (Figure 17). In the presence of sodium, the deactivation rate of vanadium was even more severe. (lA-17)... 

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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