Steam deactivation

Three series of LaCoi. CuxOs, LaMni.xCuxOs, LaFei x(Cu, Pd)x03 perovskites prepared by reactive grinding were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed desorption (TPD) of O2, NO + O2, and CsHg in the absence or presence of H2O, Fourier transform infrared (FTIR) spectroscopy as well as activity evaluations without or with 10% steam in the feed. This research was carried out with the objective to investigate the water vapor effect on the catalytic behavior of the tested perovskites. An attempt to propose a steam deactivation mechanism and to correlate the water resistance of perovskites with their properties has also been done. 

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... 

Light hydrocarbons (Ci to C4) and aromatics (mainly Ce to Ce) were produced by ZSM-5 due to the the conversion of olefins and paraffins. Thus,these results provide evidence for cracking of olefins, paraffins and cyclization of olefins by ZSM-5 at 500 C. The steam deactivated ZSM-5 catalyst exhibited reduced olefin conversion and negligible paraffin conversion activity. 

Isomerization of linear olefins to branched olefins by ZSM-5 has been observed under certain conditions (3). An analysis of the distribution of Cs and Ce olefin isomers in the feed gasoline as well as the product from steam deactivated ZSM-5 show no strong evidence for deactivated ZSM-5 to produce branched olefins from the a-olefins (Table VII). The distribution of isomers obtained with the catalyst containing 1% steam deactivated ZSM-5 in a matrix was equivalent to that obtained with the pure matrix catalyst. 

The results on olefin isomers (Table Vll) can also be explained by the observation that the constraint index of ZSM-5 is approximately unity under the conditions of this study. Shape selectivity or preferential conversion of straight chain olefins by ZSM-5 cannot be expected at 500 C. Thus, under the conditions of this study, olefin isomer distribution was not significantly affected by deactivated ZSM-5. At temperatures lower than that employed in the present study, it is conceivable that distribution of olefin isomers could be altered by steam deactivated ZSM-5. 

Table III compares the gasoline composition from three steam deactivated catalyst systems. The first contains 10% rare earth exchanged faujasite (RE FAU) in an inert silica/clay matrix at a cell size of 2.446 nm the second contains 20% of an ultra stable faujasite (Z-14 USY) at a unit cell size of 2.426 nm in inert matrix. The third contains 50% amorphous high surface area silica-alumina (70% AI2O3 30% Si02) and 50% clay the nitrogen BET surface area of this catalyst after steam deactivation is 140 m /g. All three catalysts were deactivated for 4 hrs. at 100% steam and at 816°C.

Na on zeolite Na added as Na2CO before steam deactivation. 

Figure 9. SEM-EDAX Analysis of Steam-Deactivated Samples Silicon.

Prior to testing, the catalysts and additives are steam deactivated at 1350 F, 100% steam, 15 pslg, for 8 hours. This Is Davison s S-13.5 steam deactivation. 

The Davison SOx Indices of S-13.5 steam-deactivated catalysts correlate fairly well with their performance in commercial units. This is seen in Figure 3. This correlation curve best applies to SOx emissions of about 800 ppm. 

Since the oxidation of SO to SO is a step in the operation of SOx catalysts, an increase in oxygen concentration should favor the reaction, and thereby increase the efficiency of SOx catalysts. The evidence indicates that this occurs. Baron, Wu and Krenzke (9) have shown that an increase in excess oxygen from 0.9% to 3.4% resulted in a 20% reduction in SOx emissions. This was for a steam-deactivated catalyst in a laboratory unit at 1345 F (no combustion promoter). 

We have found that Additive R has very good metals tolerance. Laboratory metals-impregnation studies show that 5,000 ppm Ni + V (33% Ni, 67% V) has no effect on the SOx reduction capability of Additive R. At a higher metals level of 10,000 ppm Ni + V (33% Ni, 67% V), Additive R loses only 9% of its SOx reduction capability. This is seen in Figure 5 for DA-250 + 10% Additive R + 0.37% CP-3. In this study, the DA-250 and Additive R were impregnated with metals then CP-3 was added and the 3-component blend steam deactivated at 1350 F, 100% steam, 15 psig, 8 hours. 

For the case in which the blend components were steamed together, the electron microprobe analyses showed the presence of silica on Additive R. This means that silica was transported from the cracking catalyst particles to the Additive R particles during the steam deactivation. The amount of silica transported and the distance the silica penetrated into the Additive R particles varied from particle to particle. The silica penetration ranged from about 10 microns to complete penetration of an entire particle. The amount of silica transported, expressed as the peak concentration observed in the outer section of the particle, varied from about 0.5% to about 8% SiO (estimates). 

These results on commercially-aged samples show that silica is transported from the cracking catalyst particles to the Additive R particles during commercial-unit aging, just as it is during a laboratory steam deactivation. More Importantly, the data show that silica deactivates Additive R in a commercial unit (loss of SOx capability) just as it does in a laboratory deactivation. 

Figure 6. Silica concentration and distribution in steam-deactivated Additive R (Blend components steamed together). Particle No. 1. Left, SEM photo and right. Si map.

High activity retentions were achieved in bench unit testing of y Og/steam deactivated catalysts blended with 15% MgO (Table III). 

Figure 12. Effect of MgO on V XANES spectrum of Catalyst A containing 5000 ppm V (from V 0 ) after steam deactivation at 1450 F 0% MgO (----), 15% MgO. ...

To promote the activity of steam deactivated PILC and to evaluate PILC as a matrix component in cracking catalysts, REY-PILC and REY-clay containing 10 wt % REY were deactivated by method D. The MAT conversions, using North Sea gas oil, and surface area after regeneration are compared with calcined PILC below. 

Finally, PILC, REY-PILC, and a commercial equilibrium catalyst were evaluated at near constant conversion using a heavier feed, hydrotreated resid. The product yields are shown in Table III. Steam deactivated (D), REY-PILC, produced the same gasoline selectivity, LCO/HCO ratio, and coke yield as calcined PILC. The equilibrium catalyst which represents a more severely deactivated (E) sample had higher gasoline selectivity, lower coke yield, and lower HCO/LCO ratio. The higher coke yield of REY-PILC could be due to occlusion of high molecular weight hydrocarbons in the microstructure of the pillared clay. 

In an exploratory experiment, 13 different powder materials were tested in a FFB ACE unit. Most of the results were unremarkable except for three catalysts a low Z/M commercial maximum distillate catalyst (the same LZM catalyst used in the pilot riser experiment), a spray dried low surface area silica (inert) and the minimum aromatics breakthrough (MAB) catalyst. The inert material was included in the study to represent thermal cracking. The catalysts were steam deactivated in the fixed bed steamer prior to testing. Catalysts and the VGO-B feed properties are displayed in Tables 2.3 and 2.1, respectively. LCO aromatics were measured with 2D GC. Figures 2.7 through 2.9 illustrate the main results. 

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