Laboratory deactivated catalysts

Advance Catalyst Evaluation unit (ACE) [5] was used to study catalyst-feed interactions on two commercially available, laboratory deactivated catalyst materials. 

Matrix and Zeolite Deactivation for Laboratory Deactivated Catalysts... 

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). 

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. 

The ACE rnns [5] nsed the same laboratory deactivated MIDAS catalyst as in the DCR rnns above. All ACE testing were conducted at a reactor temperature of 930°F... 

On the other hand, in the presence of the contaminant metals the acidities deltas are positive. The enhanced reductive part of the ADV-CPS protocol is probably responsible for this alteration. This observation can be attributed to the limitation of the vanadium deleterious effect on the catalyst s structure, as it is less drastic in its reduced oxidation state. Consequently, all the observations are convergent to the fact that keeping the metals reduced for a certain period of time during the laboratory deactivation procedure seems to be beneficial as far as acidity retention is concerned. 

FCC catalyst, supplied by Grace Davison, at three different cat-to-oil ratios, 4,6, and 8. The feed was injected at a constant rate of 3 g/min for 30 seconds. The catalyst to oil ratio was adjusted by varying the amonnt of catalyst in the reactor. Two catalysts used for this evaluation were laboratory deactivated using the cyclic propylene steaming (CPS) method [6]. Properties of these catalysts after deactivation are listed in Table 12.3. 

The Pt/Rh/Ce02 sample also generated methane, but to a minor extent (2% in the off-gas at 300 °C). Both Pt/Ce02 and Pt/Pd/Ce02 catalysts were less active but no methane was detected in the off-gas and deactivation within 1 h test duration was moderate compared with the other samples. A proprietary laboratory-made catalyst achieved equilibrium conversion of 60% under the same conditions. The catalyst showed no selectivity towards methanation. 

Comparison with Lab Steam Deactivations. Catalyst fractions which exhibit 50% or greater loss in micropore volume/crystallinity comprise less than 15% of equilibrium catalyst. The major portion of this particular equilibrium catalyst is remarkably similar to the material which results from increasingly severe laboratory steam deactivations at 815°C or less (Tables VI and VII). Dealumination is rapid, the associated crystallinity loss is small, and the matrix surface area shows little change. Crystallinity retention falls below 70% only after dealumination is complete. 

The comparison of physical properties of laboratory-steamed catalyst with those of equilibrium catalyst fractions given in Table VII indicates that a wide range of steaming temperatures is necessary to reproduce the equilibrium catalyst deactivation profile for lab steaming times of one day or less. These results indicate that an improved catalyst aging procedure for simulating... 

The test requires the use of a standard batch of gas oil as a feedstock and a set of equilibrium fluid cracking catalysts with consensus mean conversion values assigned in a reactor of specified design. The gas oil and the set of equilibrium cracking catalysts are useful reference materials. Conversion for any equilibrium or laboratory-deactivated fluid cracking catalyst can be measured and compared to a conversion calibration curve. Conversion is measured by the difference between the amount of feed used and the amount of unconverted material. The unconverted material is defined as all liquid product with a boiling point above 216°C. 

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. 

Recent work on laboratory catalyst deactivation in the presence of Ni and V by cyclic propylene steaming (CPS) has shown that a number of conditions affect the dehydrogenation activity and zeolite destruction activity of the individual metals. These conditions include find metal oxidation state, overall exposure of the metal to oxidation, the catalyst composition, the total metal concentration and the NiA ratio. Microactivity data, which show dramatic changes in coke and hydrogen production, and surface area results, which show changes in zeolite stability, are presented that illustrate the effect each of these conditions has on the laboratory deactivation of metals. The CPS conditions which are adjustable, namely final metal oxidation state and overall exposure of the metal to oxidation are used as variables which can control the metal deactivation procedure and improve the simulation of commercial catalyst deactivation. In particular, the CPS procedure can be modified to simulate both full combustion and partial combustion regeneration. 

Low Oxygen CPS Deactivation As noted earlier, commercial results (7) indicate that there is a large difference in both activity and selectivity of catalysts from full combustion and partial combustion FCC units. The variation in yields is due to the oxidation states of both Ni and V, as described in the previous section however, the variation in activity is primarily due to the oxidation state of the V, which is very destructive to the zeolite in its oxidized form. Therefore, modifications to laboratory deactivation procedures are required to simulate the deactivation of catalysts from full and partial combustion FCC units. All of the standard deactivation procedures discussed so far have been aimed at simulating full combustion. The modified CPS procedure described in the previous section does change the final metal oxidation state to a reduced state similar to what one would expect from a partial combustion unit however, throughout most of the deactivation, the metals on the catalyst are exposed to full combustion conditions. As such, the zeolite destruction is higher than that expected from a partial combustion unit. 

The gum phenomenon was studied in detail 10-25 years ago. The composition of "gum deposits" was studied by extracts of deactivated catalysts. Jackson et al, 10) found that the chemical structure of gum deposits on catalysts deactivated in laboratory tests was independent of the reacting hydrocarbons and consisted of -CH2-polymers, whereas Bhatta and Dixon (77) found aromatics in extracts from... 

Laboratory cracking catalyst deactivation protocols are used in order to simulate long term commercial catalyst deactivation in an accelerated way. Different methods reported to date have been reviewed [5]. 

The deactivated catalyst recovered from the reactor after each run was analysed for its coke content using a LECO CS244 carbon/sulphur analyzer. The total surface area of the fresh and spent catalysts were measured using a Quantasorb Sortometer in the Catalyst Characterization Laboratories at Kuwait Institute for Scientific Research. The catalyst pore structures were also examined through a scanning electron microscope and images of the fresh and spent catalyst. 

Nam et al.l studied the deactivation of a commercial catalyst, 10% V2O5 on alumina, by SO2 in the reduction of NO by NH3. The feed gas was the flue gas from the combustion of No.2 fuel oil in a laboratory furnace, doped with NO and NH3. The physico-chemical properties of the deactivating catalysts were correlated with its activity and accumulating sulfur content, and the deactivation was modeled. The activation energies of fresh and deactivated catalysts were similar. The sulfur content of the catalyst, as well as the surface area, appeared to be a dominant deactivation parameter, analogous to coke-induced deactivation. Pore size distribution changes indicated that... 

An earlier study using this same compound, DMMP, led to a mathematical model of the deactivation process. Graven et a/. studied the oxidation of DMMP vapor in a stream of air, or nitrogen, over platinum-alumina catalysts. A commercial catalyst and a number of laboratory-prepared catalysts were investigated over a range of temperatures from 573-773 K, residence times from 0.15 to 2.7 seconds. The average catalyst particle sizes varied from 0.31 to 2.4 mm. They found that the fresh catalyst showed a very high activity, but after a few hours on stream it deactivated to the point that measurable quantities of DMMP vapor appeared in the effluent.. The reaction products over the deactivated catalyst were methanol and phosphorus acid. 

Inspection at entry point Regular laboratory analysis of raw materials should be carried out to ensure smooth operations and minimum waste generation since they can more easily get converted to finished products, cause less choking in the plant units, and will not cause process problems (deactivate catalysts). 

The composition of the giun layer was examined by extracting the deactivated catalyst with trichlorine methane. After brief laboratory experiments [254] [453], a paraffinic structure of -CH2- chains was identified, whereas extracts from industrially used catalysts showed a high content of poly-aromatics [31] [54]. This indicates that the gum deposits are slowly aged to less reactive deposits (Figure 5.28). 

Tests 2 and 3 were run in the same reactor as Test 1. In order to confirm the initial activity, the catalyst was started up without added sulfur. The catalyst picked up sulfur in both these tests and was deactivated even though no sulfur was added to the feed this indicates that sulfur remained in the reactor after Test 1. This is a common problem encountered when working with sulfur in laboratory test reactors. The sulfur reacts with the steel walls of the reactor. Then, even though sulfur is removed from the feed, sulfur evolves from the walls of the reactor and it is either picked up by the catalyst or it appears in the effluent from the reactor. With continuous addition of sulfur, the CO leakage continues to increase. 

Two types of laboratory tests were conducted to evaluate contaminant tests, a catalyst stability test and a high-conversion bromine product test. For catalyst stability testing, only a small amount of catalyst was used (1.5 g) to ensure incomplete conversion of the HBr. If a feed contaminant causes catalyst deactivation, it is apparent as an immediate decrease in conversion. If an excess of catalyst was used instead, even if deactivation occurred at the inlet of the bed, it may not be detected until the region of deactivation moves considerably downstream. This could take many hours or days. 

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