Separation of fluid catalytic cracking equilibrium catalysts to improve value and reduce waste

Abstract

Useful portions of equilibrium catalyst from a Fluid Catalytic Cracking unit are obtained by fractionating to obtain a narrow size fraction, followed by separation of the narrow size fraction using density as a fractionating criterion. Size fractionating may be performed in vibrating sieves, and the density fractionating may be performed in an air cyclone. Both beneficial and detrimental fractions can be identified; in one embodiment, large particles are removed from ECAT to improve the coking factor.

Claims

1. Method of making a catalyst composition having at least one improved catalytic property from a particulate equilibrium catalyst comprising (a) fractionating said equilibrium catalyst by size, (b) recovering at least one particulate size fraction from step (a) comprising at least 80% particles within a size range having limits no greater than 30 microns apart, (c) further fractionating said at least one particulate size fraction in an air classifier, to obtain at least two subfractions, and (d) recovering at least one subfraction having at least one improved catalytic property.

2. Method of claim 1 including fractionating in step (a) in one or more sieves.

3. Method of claim 2 including vibrating said sieves.

4. Method of claim 1 including fractionating in step (a) in an air classifier.

5. Method of claim 1 including recovering, in step (b) at least one size fraction from step (a) comprising at least 80% particles within a size range having limits no greater than 20 microns apart.

6. Method of claim 1 including fractionating in step (a) or step (b) by more than one pass in an air classifier or a series of sieves, or a combination of both an air classifier and a series of sieves.

7. Method of claim 1 wherein said fraction recovered in step (d) contains at least 20% less of any of nickel, vanadium, iron, calcium, or sodium than is present in said equilibrium catalyst.

8. Method of claim 1 wherein said fraction recovered in step (d) has a coke factor at least 5% better than said equilibrium catalyst.

9. Method of claim 1 including identifying said subfraction recovered in step (d) as enriched in ZSM-5 additive having at least one catalytic property superior to said equilibrium catalyst by determining that either (i) its lanthanum content is lower than said equilibrium catalyst or (ii) its phosphorous content is higher than said equilibrium catalyst or (iii) its properties for making propylene or butylenes are superior to those of said equilibrium catalyst.

10. Method of claim 1 including identifying said subfraction recovered in step (d) as depleted in ZSM-5 additive having at least one catalytic property inferior to said equilibrium catalyst by determining that either (i) its lanthanum content is higher than said equilibrium catalyst or (ii) its phosphorous content is lower than said equilibrium catalyst or (iii) its properties for making propylene or butylenes are inferior to those of said equilibrium.

11. Method of claim 1 including identifying said subfraction recovered in step (d) as having at least one catalytic property superior to said equilibrium catalyst by determining that its content of at least one metal is lower than said equilibrium catalyst.

12. Method of claim 1 including identifying said subfraction recovered in step (d) as having at least one catalytic property superior to said equilibrium catalyst by determining that its coke factor is lower than said equilibrium catalyst.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a simplified process flowsheet to show apparatus to separate catalyst

(2) FIG. 2 is a plot graph demonstrating the PSD of fines recovered with kinetic screening

(3) FIG. 3 is a plot graph showing Ni Content

(4) FIG. 4 is a plot graph showing V Content

(5) FIG. 5 is a plot graph showing the BET surface area

(6) FIG. 6 is a plot graph showing P2O5 content

DETAILED DESCRIPTION OF THE INVENTION

(7) As indicated above, it is known in the art that high metal content in ECAT is generally correlated to high coke formation, leading to low conversion rates, and conversely particles containing low concentration of metals, particularly nickel and vanadium, can be expected to continue to perform at acceptable rates as they get older. Example 1 demonstrates, however, that particle size is also a factor. Indeed, Example 1 will demonstrate that when the low metal content resides in large particles, conversion can be low enough to suggest removal of the large particles.

Example 1Particle Size Effect

(8) An ECAT from a working FCC unit was obtained and had the following properties based on an average of 4 samples collected (to minimize variations due to measurements)

(9) TABLE-US-00002 TABLE 2 Conversion, wt % 73.7 Vanadium, wt % 71.2 CPF.sup.1 1.4 Al2O3, wt % 51.2 GPF.sup.2 2.0 C, wt % 0.03 SA, Mg.sup.2/g 142.4 0-20, wt % 0.0 MSA, Mg.sup.2/g 85 0-40, wt % 1.5 Na, Wt % 0.2 0-80, wt % 43.2 RE, wt % 1.64 APS, m 85.6 Nickel, ppm 226
1. Coke factor 2. Gas factor

(10) The definitions of conversion, CPF (Coke factor) and GPF (gas factor) are known to those experts in the Art.

(11) This sample was then subjected to a separation by particle size using a SWECO MX-48 Vibro-Energy Round Separator equipped with screens according to the desired particle size cut. This commercially available machine utilizes both vibration and tilting to assist in the sieving process. In a preferred embodiment, the screens may be equipped with special equipment to avoid plugging of the screens with fines. Sweco provides such equipment either as a removable screen with large holes in which balls are or inclusive to the screens. The vibrational frequencies (horizontal and vertical) of the equipment may be optimized by trial and error as each ECAT has unique properties.

(12) In this example, we used a single screen system that was changed once the whole product was passed through. We started with the largest fraction since this is the easiest to screen at a fast rate. The next smaller screen was then installed and the material that passed through the screen was fed. This was repeated with all the available screens. We have also carried out experiments with multiple screens at once and they also work and may be used in my invention. The kinetic energy applied to the sieves should be adjusted in order to minimize excessive jumping of the particles which tends to generate dust. A cover on the system is preferred. Some of the most important properties of the fractions are presented on the following Table 3.

(13) TABLE-US-00003 TABLE 3 Sample SA, Na, RE, Ni, V, Al2O3, APS, ID Mg.sup.2/g wt % wt % ppm ppm wt % m Fraction 1 144 0.23 1.70 519 786 50.3 49 Fraction 2 128 0.24 1.70 413 825 50.4 64 Fraction 3 137 0.23 1.80 360 853 50.2 89 Fraction 4 134 0.26 1.80 274 783 51.0 116 Fraction 5 137 0.25 1.80 274 799 51.4 152

(14) In order to demonstrate the usefulness of the invention, Fraction 5 was sent for testing and was compared with the original sample. Below, in Table 4, are the results of the catalytic testing.

(15) TABLE-US-00004 TABLE 4 Sample ID Conversion, wt % CPF GPF Fraction 5 71.8 1.75 1.69 2 week Average.sup.1 73.7 1.4 2.0 Change 1.9 0.4 0.31 .sup.1The 2 week average is the plant record for the ECAT sample as a whole.

(16) For those versed in the Art, it is clear that the yields of the Fraction 5 with a large particle size distribution are detrimental to the yields of the blend. In other words, removing Fraction 5, having the largest particle size distribution, from the original sample would yield a product with improved conversion and improved Coke Factor. This finding is completely contrary to the generally accepted principle that low nickel and vanadium contents will result in lower coke.

(17) My invention therefore includes a process of making an improved ECAT by removing particles larger than 90 microns. If desired, the cut-off could be at 100 microns, 110 microns, or 120 microns or any other cutoff above 90. My invention includes a composition comprising ECAT of particles less than 105 microns and no more than 5_% particles larger than 105 microns; also my invention includes ECAT consisting essentially of no more than 5% by weight particles more than 105 microns and the balance particles less than 105 microns.

Example 2Fines and Fractionation

(18) An ECAT from a working FCC unit was obtained and found to have the following particle size distribution (PSD), as shown in Table 5:

(19) TABLE-US-00005 TABLE 5 % Passing Size, m 10 23.38 20 35.82 30 46.38 40 55.00 50 62.52 60 69.57 70 76.94 80 85.47 90 97.59 95 107.8

(20) Fines content above 2 wt % in the less then 20 microns range and 15% in the range less than 40 microns are considered high for ECAT purposes. Clearly this ECAT contained excessive fines which are undesirable in the FCC unit but also interfere with the separation in the kinetic screening process. Accordingly, an original sample was then subjected to a separation using a SWECO MX-48 Vibro-Energy Round Separator identical to that used to obtain the PSD shown in Table 5. However, even after several adjustments on the kinetic energy input (vibrational energy on the horizontal and vertical axis) were tried, the rates of the separation were much slower than those of the procedure used to obtain the result shown in Table 3. We also noticed plugging of the screens.

(21) In order to achieve a better separation by particle size in the presence of a lot of fines, the sample was introduced to an ACS-005 air classifier made by RSG, Inc. of Sylacauga, Ala. The feed was injected via a screw feeder at a measured rate of about 700 lbs/hour. The motor was run at several conditions but we opted for 1100 rpm as a reasonable rate to separate the finest and lightest 35% of the sample. The particle size of the fractions is shown on Table 6. After removal of the fines, the coarser material was then passed to the kinetic separator (the SWECO MX-48 vibrating sieve system described above) with much improved rates. Rates of greater than 500 lbs/hr were achieved with good separation for the equipment used. These rates are not feasible with the fines present.

(22) TABLE-US-00006 TABLE 6 Starting ECAT with Fines Fines Material Removed Removed 100% 65% 35% % Passing Size, m Size, m Size, m 10 23.38 49.99 3.33 20 35.82 61.70 4.90 30 46.38 70.04 6.78 40 55.00 77.40 9.14 50 62.52 84.55 12.26 60 69.57 92.23 15.95 70 76.94 101.1 1.25 80 85.47 112.9 25.90 90 97.59 132.8 36.52 95 107.8 154.1 49.00

Example 3Density/Particle Size Separation

(23) The effectiveness of the air classifier to distinguished particles of different densities is improved by injecting particles with a narrow PSD. The ECAT in this example is known to contain at least three components: a high surface area FCC base catalyst (tracked by Rare Earth content), a ZSM-5 additive for propylene production tracked by Phosphorus content, and a low surface area component without rare earth and phosphorus. The amount of each of the components is not known exactly. Pure ZSM-5 additives usually have approximately 10 wt % P2O5. One must remember that it is likely that the three components differ in particle size distribution. Here, the coarser/heavier material from Example 2 was fractionated in the kinetic separator by using screens with cuts at approximately 120, 85, 60, 50 and 40 microns.

(24) The following Table 7 shows all the separations that were done on the air classifier in each of the different fractions collected from the kinetic separator:

(25) TABLE-US-00007 TABLE 7 Average Experimental Conditions Particle Size, Surface Area EXPER- Fraction feed microns m2/g IMENT Fed rpm rate Light Heavy Light Heavy 8 45 to 55.sup.1 1100 432 9 Heavy 8.sup.2 750 344 53 147 11 65 to 85.sup.3 750 769 12 Heavy 11 750 523 79 148 13 Light 11 750 434 78 154 14 85 to 750 472 120.sup.4 15 14 Heavy 750 327 102 157 16 14 Light 750 310 99 158 17 120 plus.sup.5 750 268 148 155 .sup.1,3,4,5the units are microns; the nominal screen limits are approximate - light scattering techniques were used to determine the fraction particle sizes.
2: The heavy fraction obtained in experiment 8 was fed.

(26) As a matter of example, Experiment 11 is the fraction collected by screening the sample used for Table 6 with the screens of nominally 85 and 65 microns. This was fed to the air classifier identified above with a feed rate of 769 lbs/hr at a rotor speed of 750 rpm and air blower frequency of 60 Hz. The product denominated Light 11 was 39% and the product denominated Heavy 11 was 61%. The Heavy/Coarse (Heavy 11, 61%) material was then fed with similar conditions with exception of a reduction in feed rate to 523 lbs/hr in Experiment 12. The fractions recovered were 45% Light 12 and 55% Heavy 12. Sample Heavy 12 represented the heaviest and or largest particles sieved with the screens between 85 and 60 microns.

(27) The Light 11 product was then also processed again in the air classifier with a feed rate of 434 lbs/hr in Experiment 13. In this case, the product recoveries were 47% for the Light 13 and 53% for the heavy/coarse material Heavy 13. The surface area analysis of the Light 13 and Heavy 12 samples, both from the same cut from the kinetic separator substantiate a lighter fraction given the higher surface area. Both the light and heavy fractions obtained may be further fractionated. Generally, they may first be fractionated by size with the kinetic sieve device and then further utilizing density differences in the air classifier. Further data has shown that a much higher rotor speed would lead into a better separation. This will be the subject of another example.

(28) Three of the samples above were also submitted for chemical analysis, with the results shown in Table 8.

(29) TABLE-US-00008 TABLE 8 SiO2, Al2O3, TiO2, Na2O, Fe2O3, La2O3, V, Ni, Zn, P2O5, Sample Wt % Wt % Wt % Wt % Wt % Wt % ppm Ppm Ppm Wt % Heavy 9 54.9 39.8 1.39 0.27 0.85 1.09 292 406 86 2.74 Heavy 55.1 39.8 1.28 0.29 0.75 0.53 210 183 51 4.37 17 Heavy 54.8 40.3 1.39 0.25 0.86 0.92 294 311 76 2.63 12

(30) Table 8 has some useful information sheds light into the components of each fraction.

(31) Fraction Heavy 17 clearly has a much higher ZSM-5 additive content than any of the other two fractions. This indicates a concentraton of ZSM-5 approaching 45%. This is also reflected on the much lower La2O3 content which is associated with the base catalyst. The TiO2 and Fe2O3 are lower thus suggesting also a lower content of such inactive component (clay that usually contains both of those contaminants). So even though the total base zeolite is lower, the clay is also lower. Taking into consideration that ZSM-5 is a very stable structure that suffers very little loss of crystalinity upon deactivation, we can explain the higher surface area of this Heavy fraction. Heavy 17 is a clear candidate for reuse in the FCC unit.

Example 4Recovery of Valuable Product from Air Classified Fines

(32) The use of Air Classification for removal of undesired particles, usually trying to control the 0-20 microns range is known to experts in the Art to correct for batches of catalysts that contain an excessive amount of fines. Recently, some refiners have started to set a specification on the 20-40 micron range as these particles tend to be lost preferentially from the FCC unit. Some unit designs are capable of running even with very few particles in that range (less than 3 to 5 wt % is considered low for many units) but some of these units can function normally at least from a physical point of view. Some catalyst manufactuers have then opted for Air Classification of their products in order to meet the new specifications. However, it is also known that, besides removing the undesired particles, air classification results in a substantial loss of desirable products. We have also indicated the sieving of fines from an ECAT (or fresh catalyst) can be achieved but usually at slow rate. Also we have mentioned that screens tend to plug thus making the process ineficcient unless a lot of machines are used in parallel. In this example, we show that by using a combination of Air Classification followed by screening of the fines under the right conditions, it is possible to dramatically reduce the amount of losses caused by the use of the Air Classifier alone. Because the ECAT product is of limited value relative to the costs to segregate effectively, the extra recovery of valuable samples is enough to convert this process from negative added value to positive added value.

(33) In this example, the air classifier was run at 1500 RPM with a feed rate of 512 lbs/hr yielding 26% yield of fines and 74% of coarser product. The product in this case was a spray dried particle with a homogeneous composition across the particle size. Table 9 shows the results obtained.

(34) TABLE-US-00009 TABLE 9 Original Coarse Fines SIZE, m 100% 74% 26% 0 to 20 2 0 5 0 to 40 22 6 64 0 to 80 66 54 93 0 to 105 81 78 96 0 to 125 89 89 97 0 to 150 95 0 98 APS 62 78 35

(35) As can be seen on Table 9, the fines contain 26% of material that is 0-40 microns with only 5% being 0-20%. This means that in order to reduce the 0-40 micron content by 16 wt %, we had to reject 26% of the initial sample. In order to improve the yield, this material was processed in the kinetic separator (sieves) with a 45 micron screen but adjusted with a feed rate of less than 200 lbs per hour and a higher degree of vibration (as per the manufacturer manual) optimized to minimize plugging of the screens even at the expense of a less than optimal separation. In other words, it is more or less unavoidable that some particles that have the potential to be screened are left in the final product in order to minimize the chance of plugging the screens. In this example, we were able to process the fine material and recover two fractions with the PSD shown on the figure below. Of the total 26% of the original sample, 14% of the sample was rejected and only 18% of the particles were measured to be below 40 microns (probably due to imperfections on the screens). Thus, with the combination of both techniques, in order to reduce the 0-40 micron by 14% (from 22% to 8%) we only lost a total 14% for an almost perfect separation.

(36) This type of separation was also done on ECAT's with very similar results. Thus a combination of both techniques is not only commercially feasble but it practically minimizes the waste of good product thus enhancing the feasibility of this application.

Example 5Multiple Passing Through a Classifier

(37) The same ECAT from example 2 is used as starting material. However, instead of pre-screening the fines at a very high rate, a sharper cut was attempted by running the air classifier at a higher speed (2000 RPM) while also reducing the feed rate.

(38) Table 10 shows all the separations that were done on the original sample (Experiment 13A) and on different fractions (13A Coarse/Heavy and 13A Fines/Light). For completeness, the labels on the results indicate that the separation includes not only the particle size separation but also density effects.

(39) TABLE-US-00010 Average Particle Size, Surface Experimental Conditions microns Area m2/g Feed Light/ Heavy/ Light/ Heavy/ Light/ Heavy/ EXPERIMENT Feed RPM rate Fines Coarse Fines Coarse Fines Coarse 13A ECAT 2000 356 35% 65% 40 84 149 159 14A 13A 1200 459 62% 38% 76 105 157 160 Coarse 15A 13A 2200 354 64% 35% 31 62 145 153 Fines
All the samples (with the exception of the fines from the first pass through the screener) were submitted for chemical analysis. The results are shown on Table 11.

(40) TABLE-US-00011 TABLE 11 APS, Ni V P2O5 m ppm ppm Wt % 70 334 251 3.0 84 261 238 3.1 106 211 211 3.2 76 286 239 2.8 62 341 255 3.0 31 433 265 2.7

(41) In order to see if further separation was still possible, the fractions from Experiment 14A were sieved. The fines/lighter fraction was sieved with a 75 micron sieve while the coarse/heavier sample was sieved with a 106 micron sieve. The following results were obtained:

(42) TABLE-US-00012 Cut Point, BET, Ni V P2O5 Estimated EXPERIMENT Feed m % SA ppm ppm Wt % APS, m 14A Fines/Light 75 62% 154 343 256 2.8 60 14A Fines/Light 75+ 38% 163 225 232 3.1 85 14A 106 63% 159 258 235 2.7 90 Coarse/Heavy 14A 106+ 37% 159 152 191 4.6 120 Coarse/Heavy

(43) The following plots summarize the results in a graphical way demonstrating the dependency of the metals Ni, V, known poisons, BET surface area, a measurement of crystallinity in these materials, and P2O5, a measurement of the amount of ZSM-5 in the sample.

(44) Referring now to FIG. 1, which is a simplified process flowsheet, a useful apparatus for practicing the invention is seen to comprise an air classifier 1, an air cyclone 2, a dust collector 3, and a blower not shown. These components are well known in the art. The blower draws air through the entire system, beginning at ECAT source 4 which is a duct through which the ECAT particles are drawn into air classifier 1. Both the air classifier 1 and the cyclone 2 are affected by rotation speed, which is adjustable. The air classifier 1 includes an interior rotor which affects the separation of particles. Generally, the larger, heavier particles fall to the bottom of air classifier 1 and the lighter ones proceed to the cyclone 2. The cyclone 2 operates only on kinetic forces, but also makes a two-part separation, the larger, heavier particles falling to the bottom and the lighter ones being drawn into the dust collector 3. Dust collector 3 is used primarily for environmental purposes; the particles it collects are generally quite small. The operator may collect the larger, heavier particles from the bottom of air classifier 1, while the particles in the bottom of cyclone 2 will generally be lighter and smaller. As indicated above, I refer to this entire assembly as an air classifier.

(45) In one useful practice, a selected fraction having a width range no greater than 30 microns is collected from a set of sieves not shown and fed to the air classifier 1 through source 4, where it is separated as indicated above, the lighter smaller particles being sent to the cyclone for further separation.

(46) Any sieving system effective to sort ECAT by size may be used in my invention. Vibrating and tilting techniques known in the art may be used to enhance the accuracy and speed of the process. Any air classifier or air classifier system effective to sort particulate ECAT may be used in my invention; as indicated above, the ability of the air classifier to recognize density as a criterion for sorting is enhanced by feeding narrow width fractions to it.

(47) The operator has considerable discretion in the choice and number of and type of sieves, and whether to employ enhancements such as vibrators, but for my invention it is necessary that at least one fraction be obtained having a size range no wider than 30 microns, more preferably 20 microns, and most preferably no more than 10 microns.

(48) Thus, it is seen that my invention includes a method of making a catalyst composition having at least one improved catalytic property from a particulate equilibrium catalyst comprising (a) fractionating said equilibrium catalyst by size, (b) recovering at least one particulate size fraction from step (a) comprising at least 80% particles within a size range having limits no greater than 30 microns apart, (c) further fractionating said at least one particulate size fraction in an air classifier, to obtain at least two subfractions, and (d) recovering at least one subfraction having at least one improved catalytic property.

(49) My invention also includes a method of separating from an equilibrium catalyst containing recycled fines a fraction of said equilibrium catalyst having at least one catalytic property superior to said equilibrium catalyst comprising (a) removing from said particulate equilibrium catalyst at least 90% by weight of all particulates less than 20 microns in dimension, thereby obtaining a portion of equilibrium catalyst depleted in fines, (b) fractionating said portion of equilibrium catalyst depleted in fines to obtain at least one fraction thereof within a size range having limits no greater than 30 microns apart, and (c) further fractionating said at least one fraction utilizing density as at least one criterion, to obtain at least two subfractions thereof, and (d) recovering at least one subfraction from step (c) having at least one catalytic property superior to said equilibrium catalyst.

(50) In addition, my invention includes a method of improving the catalytic properties of a particulate equilibrium catalyst comprising (a) optionally discarding at least 50% of particles therein of a size less than 20 microns (b) fractionating the remaining equilibrium catalyst by size, (c)_recovering at least one particulate size fraction from step (b) comprising at least 80% particles within a size range having limits no greater than 30 microns apart, (d) further fractionating said at least one particulate size fraction recovered in step_(c) utilizing density as at least one fractionation criterion, to obtain at least two subfractions, and (e) discarding at least one subfraction from step (c) having at least one catalytic property detrimental to said equilibrium catalyst.

(51) Also, my invention includes a method of making an equilibrium catalyst having at least one improved catalytic property comprising removing from said equilibrium catalyst an amount of particles larger than 90 microns effective to improve said at least one catalytic property.

(52) And, my invention includes a particulate equilibrium catalyst including no more than 5% by weight particles larger than 105 microns.

(53) It also includes a method of modifying a fresh catalytic cracking catalyst or an FCC additive therefor to improve at least one catalytic property thereof comprising removing from said fresh catalytic cracking catalyst or additive therefor at least some particles larger than 90 microns.

(54) The invention also includes a particulate fresh catalytic cracking catalyst including no more than 5% by weight particles larger than 105 microns.