AU596604B2 - Control of sox emission - Google Patents

Description

Syney 6056A:rk -j 7 4 596604 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 Form 1( COMPLETE SPECIFICATION FOR OFFICE USE Short Title: Int. Cl: Application Number: 4, Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: This djuctjncnt contalm rg amndments made u~mw th Section 49.

And to oomcw t nt.

99 9.

9 9 9 9 9. S.

9 S 9 9 *9 9 9 9.a t *t 99 9 Priority: Related Art: TO BE COMPLETED BY APPLICANT 4 .9 9 9 .9.9 .9 9 9 .9 99 9 9 99 69

I.

9 999999 4, Name of Applicant: Address of Applicant: ,Rctual inventor: Address for Service: TEXACO DEVELOPMENT CORPORATION 2000 Westchester Avenue, White Plains, NEW YORK 10650, U.S.A.

Paul Herbert Lewis 1igene Pei-Shing Dai and Edward Harland Holst GRIFFITH HASSEL FRAZER 71 YORK STREET SYDNEY NSW 2000'

AUSTRALIA

Complete Specification for the invention. entitled: CONTROL OF SOX EMISSION The following statement is a full d escription of this invention, i~hcluding the best method oF performing it known to >me/us:- 56A :r k

;I

:.I

0.77,872-C1-FB CONTROL OF SOx EMISSION x .9 91l 9 Il *I.9 I 9 p4 9.l I This invention relates to a process for remov.,.g a gaseous sulfur compound from a mixture of gases containing sulfur oxides. More.particularly, it relates to fluid catalytic cracking under conditions whereby the sulfur oxide content of the r generator off-gas is lowered.

As is well known to those skilled in the art, when sulfur-containing charge hydrocarbons are admitted to a fluid catalytic cracking (FCC) reactor, the S charge is converted to -lower boiling products including those falling within the motor fuel boiling range.

A portion of the sulfur in the charge hydrocarbon is liberated in the reactor as hydrogen sulfide and mercaptans which may be separated from the FCCU cracked products. A portion of the sulfur is fixed on the coke-containing spent catalyst which is passed from the reaction zone to the regeneration zone wherein an oxygen-containing gas is provided to regenerate the S spent catalyst. The gas formed during regeneration includes oxides of carbon as the coke is burned from the surface of the catalyst. The gas so formed also includes oxides of sulfur (principally sulfur dioxide plus some sulfur trioxide); and these oxides of the sul fur- may be the predomi narnt undesirable species S in the regenerator off-gas.

Economic considerations prevent the effective removal of sulfur oxides from the regenerator offgas; and environmental considerations dictate that they be decreased. Prior art attempts include operation under conditions such that the sulfur in the regeneration zone is fixed on the catalyst (thereby lowering the

SO

x content of the regenerator off-gas); and the sulfur 69 0 we 0 0v 9 99 99-V

I

i2 r 1 r f S2 is released as additional mercaptan and hydrogen sulfide in the reaction zone. Here these sulfur compositions may be readily passed to effluent separation operations which would not be the case for sulfurcontaining gases recovered as regenerator waste-gas.

Illustrative of prior art endeavors in this area include those disclosed in U.S.P. 4,344,926 which issued August 17, 1982 to Texaco Inc. as assignee of Randall H. Petty and Burton H. Bartley (the text of which is incorporated herein by reference) and the prior art cited therein.

It is an object of this invention to provide a process for removing a gaseous sulfur compound from a mixture of gases containing sulfur oxides.

Other objects will be pparent to those skilled in S the art.

In accordance with certain of its aspects, this i,"t invention is directed to a process for removing a t C gaseous sulfur compound from.a mixture of gases containing sulfur oxides which comprises c ntacting said mixture of gases containing sulfur oxides at 800 0 F 1500°F (427 0 C 816 0 C) with a composite containing a porous refractory support bearing as a first component (i) at least one of bismuth, -hri- amn-u, or a rare earth StC C C e 25 metal, such as cerium and as a second component (ii) at least one alkali metal.

The mixture of gases which may be treated by S the process of this invention include gases which contain sulfur oxides; and commonly such gases are found -to contain, as the principal oxide of sulfur, sulfur d .xide with lesser quantities of sulfur trioxide.

In the preferred embodiment, this invention finds use in connection with fluid catalytic cracking (FCC) wherein a charge hydrocarbon is subjected to cracking conditions include temperature of 800°F S- 1200°F (427 0 C 649 0 typically 960 0 F (516°C) to yield cracked product contai ning hydrocarbons 1_1 I 1 I 3boiling in the motor fuel boiling range. When the charge to cracking (typically a gas oil) contains sulfur, a portion of this sulfur is reduced in the reaction zone to hydrogen sulfide and mercaptans which are recovered with the cracked product from which they may readily be separated.

During reaction, the fluid catalyst particles become deactivated as they are covered with coke; and they also pick up a substantial portion of sulfur.

This spent catalyst is passed to a regeneration zone wherein spent catalyst is contacted with oxygen-containing gas, typically air, at 1100F 1500°F (595 0 C 815°C), typically 1350°F (732 0 and under these conditions, the spent catalyst is regenerated and may thereafter :'15 by returned to the readtion zone. During regeneration, the coke content of th'e spent catalyst is oxidized to form regenerator off-gas including carbon dioxide and carbon monoxide. Sulfur in the spent catalyst S is oxidized to form sulfur dioxide and sulfur trioxide.

The content of SO (oxides of sulfur) in the regenerator off-gas, when the initial sulfur-containing charge contains 0.5 w% 2.5 say 2 w% sulfur, may be as high as 4 w% 5 say 5 w% of the sulfur content of the charge hydrocarbon to the reaction zone.

The SOx content of regenerator off-gas under these x conditions may be 2000 3000 ppm(v), say 2500 ppm(v).

It is a feature of the process of this invention tthat the SO content of these sulfur-containing gases 0 may be reduced by contacting these gases at 800°F 1500F (427 0 C 815 0 preferably 1000°F 1500°F (595°C 815°C) say 1350°F (732 C) with a composite containing a porous refractory support bearing as a first component at least one of bismuth, eaha, or a rare earth metal such as cerium and as a second component (ii) at least one alkali metal, preferably potassium or sodium or cesium.

L.

4 The porous refractory support which may be employed in practice of the process of this invention may be active or inactive or inert. Typical of such supports may be alumina gamma alumina), silica, magnesia, silica-alumina, silica-magnesia, mordenite, zeolites, etc. When the SO x -containing gases are passed from the regeneration zone to a separate conversion zone, the support may be any convenient support whether active or inactive or inert and may be of a particle size comparable to that utilized in fluid bed operations 20-200 microns) or that utilized in fixed bed operations 0.1-1 inch).

It is, however, preferred in the case of FCC operations, that the support be of particle size 15 suitable for use in FCC operations (20-200 microns).

Although it is possible to utilize, as the support for removing gaseous sulfur compounds, the fluidized S catalyst which is used in FCC operations, it is preferred S, that this support be a different phase; i.e. even 20 in those instances when it is the same composition as the support for the FCC catalyst (or as the FCC :catalyst), it is preferred that it be formulated separately and thereafter mixed with the FCC catalyst.

Typical equilibrium FCC catalysts 'may include.

25 that marketed by Davison Chemical Division of W.

R. Grace and Company under the trademark CBZ-l containing a synthetic crystalline Y-type zeolite in an amorphous S 'e silica-alumina matrix having the following character- |O istics: I j II I; TABLE 1 Cracking Catalyst Property Value Surface Area, m2/gm 105 Pore Volume cc/gm 0.37 Density, Ib/ft 3 Aerated 47.6 Settled 51.8 Particle Size Distribution, wt. 0 20 microns 0 20 40 microns 0 0 40 80 microns 22 80+ microns 78 Average Particle Size, (microns) 86 37.7 Alumina Content, wt. a 0.41 T Sodium Content, wt. %41 X-Ray Metals, wpprl* Cu Ni 220 3330 Fe Cr 310 SV 370 Zeolite Content, wt. 7.9 parts per million by weight

S/

I6 1

I

Illustrative porous refractory supports which may be employed in the SO x removing compositions of this invention may include a gamma alumina prepared by calcining for 3 hours at 900°F (482°C): the Catapal SB brand of high purity alpha alumina monohydrate marketed by Conoco Chemicals Divisioan of Continental Oil Company. The gamma alumina produet is characterized as follows: TABLE I I Alumina content*, wt.

Loss on Ignition, wt.

Carbon*, wt. Si0 wt. Fe2 0 wt. Na 20*, wt. Sulfur*, wt. Ti0 wt. Crystal Structure* 0.3% 0.068% 0.005% 0.004% 0.01% 0.12% alpha-alumina monohydrate gamma- al umi na 250m2/g 49 1 b,/ft 3 48%< 45 microns 9% >90 microns Crystal Structure** Surface Area (BET)** Pore Volume** 0-100A O-lO,O00A Loose Bulk Density* Particle Size Distribution* *As received **After calcination fo0r 3 hrs. at 900°F (482°C.

~i -1 i, I -7 In the preferred embodiment, the additive composition of the instant invention is prepared (as on alumina support) separately from the FCC cracking catalyst; and it is then mixed with the FCC catalyst to yield a mixture wherein the additive composition of the instant invention is 1 10 say 6 w% of the total mixture.

It is a feature of this invention that the composition contains (in addition to the porous refractory support) as a first component at least one. of bismuth, h~Bmi, or a rare earth metal such as cerium and as a second component (ii) at least one alkali metal, preferably potassium sodium, cesium, or rubidium. Preferred compositions contain potassium 0 15 and cerium or sodium and'cerium.

These compositions" may commonly be prepared by immersing the support, typically gamma alumina of 20-200 micron particle size, in aqueous solutions tt«t t of water-soluble compounds of the component metals.

20 Typical water-soluble .compounds may -1include:; acetates, oxalates, or nitrates of cerium and of the alkali metals e.g. sodium, potassium, or cesium. Bismuth may be added to the alumina as a 7 w% solution of Bi (NO 3 5H 2 0 in water which has been acidified 25 with sufficient nitric acid to form a clear solution.

It is possible to add all the metals of the two ,omponents separately or in one operation.

The rare earth metals include elements of atomic number 57 to 71. This group which is sometimes referred to as a lanthanide series -includes lanthanum, cerium, praeseodymium, samarium, dysprosium, and other elements which are present in small quantities. These metals are difficultly separable from -n e another and may be available commercially in a mixture containing about 50 w% cerium, 20-30 w% lanthanum, 15% neodymium, 5-6% praeseodymium, and less thai about of the remaining rare earth elements. For purposes of the instant inventnfon it is found that mixtures A l 1y

A

-8 of rare earths may be employed including those commonly avaiable which are naturally occurring mixtures which have not been separated into fractions. Although less desirable because of increased cost, available salts of increased purity of cerium or lanthanum may be employed such as cerium nitrate Ce (NO 3 )3 6H20.

In one preferred embodiment, it may be desirable to add the alumina support to a solution of alkali metal hydroxide and thereafter to add a solution of the nitrate of bismuth or cerium. The latter metals are precipitated as their hydroxides or oxides.

The mix may then -e dried, e.g. at 212 0 F-300°F (100 0 C 140°C) for 1 24 hours, say 15 hours and then crushed to desired size of 50-200 microns.

S, It may then be calcined at 1300 0 F 1500 0 F (704°C 816 0 say 1400 0 F (760 0 C) for 3 36 hours, say 24 hours.

More than one metal from each group may be added Na and K plus Bi and Ce, or K plus Bi and Ce); t it is found, however, that satisfactory improved) results may be achieved by use of one metal from each group e.g. K-Ce; Na-Ce; K-Bi; Na-Bi; etc.

The preferred composition contains potassium and 25 cerium: K-Ce.

o* is preferred that the first component (preferably bismuth or cerium) be present in the total amount of 0.5 10w%, preferably 0.5w% 5w%, more preferably lw% 3w% of the support, say 3w%. The second alkali 30 metal component (potassium, sodiun, or cesium) is preferably present in amount of 0.4 10w%, preferably Sw% 5w%, more preferably lw% 3w%, say 3w% of the support. A preferred composition may contain 3w% potassium (expressed as K) plus 3w% cerium (expressed as Ce) on gamma alumina prepared from the Catapal SB c u ,aina.

SThe composition so prepared may in the preferred embodiment be mixed with FtC cracking catalyst 'and 1 i i 9- *t ft.

ft ft I tE t eT tc C C used in an FCCU wherein a sulfur-containing charge hydrocarbon is cracked. Illustrative of the charge hydrocarbons may be a straight run gas oil having API gravity of 22.0 26.4 and containing 0.5 w% sulfur.

It is unexpectedly found that substantially improved results (measured in terms of the w% of feed sulfur found in the off-gas e.g. from the FCCU regenerator) may be obtained if the composition contains the first component in the form of crystals of oxide of crystal size of les(s than about 90 Angstrom Units.

It is also unexpectedly found that composites containing crystals of size 20 85 Angstrom Units, more preferably 70 Angstrom Units, typically about 60 70 Angstrom 15 Units;. possess superior stability towards the steaming that occurs in the FCCU re'generator.

The crystal size of the crystals of the oxide S of the first component typically cerium oxide, principally Ce0 2 is the weight average crystal size as determined ,20 by X-ray diffraction line broadening, using molybdenum X-rays. The line width of the CeO 2 line at a d-spacing of 3.12A is measured at half peak intensity. The line widths are corrected for camera geometrical factors by using the Warren method described in H.P.

Klug and L.E. Alexander, "X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials", John Wiley, New York (1954), pages 502 503. Large crystal size LiF is incorporated in each sample in weighed amounts to serve as a calibration material. The 030 LiF diffraction line at d-spacing 2.325A is measured.

Crystal sizes are calculated from diffraction line widths using the well known Scherrer equation.

Crystalline CeO 2 contents are calculated from the ratio of the intensity of the CeO 2 diffraction line at d-spacing 3.12A to that of the LiF at d-spacing 2.325A.Q The ratio is related to crystalline CeO2 content by a proportionality constant. The proportionality constant' is (determined using mixtures of CeO with alumi ia 2 of known composition.

c cc c Ic V Co oC

A

if 10 As the average crystal size so measured decreases, the line broadens; and eventually (in the 10 Angstrom Unit crystal size range), the line becomes more and more difficult to distinguish from the background.

It will be apparent that the measured size is a weight average. There is a crystal size distribution; and a given sample will contain crystals of crystal size above and below the stated weight average value.

The desired crystal size of the first component, e.g. CeO 2 can be obtained by controlling the amount of cerium deposited on a given surface area. The larger the cerium amount, the larger the CeO2 crystals.

For example, Catapal SB alumina has a surface area of 250 m 2 If this alumina is impregnated so as to contain 2.4 w% cerium, CeO 2 crystals form that are 10 Angstrom Units in size. It is further found that if the Catapal SB ,alumina is impregnated with 4.5 5.0 w% cerium, CeO 2 crystals form that are 60 70 Angstrom Units in size. It is further found that if the Catapal SB alumina is impregnated with w% Cerium, CeO2 crystals form that are 123 Angstrom Units in size.

In order to prepare an agent that contains w% cerium and yet has a larger CeO2 crystal size S0 than 10 Angstrom Units it is necessary that the alumina have a surface area materially smaller than 250 m 2 /g, A say 150 m 2 It is apparent to those skilled in the art that if an agent is improperly made so that 1 30 local high concentrations of cerium salts form on Sthe alumina, larger than expected CeO2 crystals wi'll form. It is necessary that the mixing of alumin'a and cerium and potassium additives be thorough.

The drying of the agent after impregnation should be sufficiently slow that solution droplets do not form.

In another embodiment, it is found that posttreating a formed catalyst by steaming may ,Jodify \v 11 CeO2 crystal size. The effect of steaming is the more pronounced the higher the cerium content of the agent. Thus, steaming at 1400°F 1500°F, preferably 1470°F for 12 to 48 hours, preferably 24 hours, of an agent that contains 2.4 w% cerium causes no increase in CeO2 crystal size. In contrast, similar steaming causes an increase in CeO 2 crystal size from 63 66 A.U. to 85 A.U. when the agent cerium content is 4.6 4.8 w%.

The compositioN;s of this invention may commonly be prepared by immersing the support, typically gamma alumina of 20 200 micron particle size and having a surface area of 150 400, preferably 200 300, say about 250 square meters per gram (m 2 in aqueous 15 solutions of water-soluble compounds of the component metals. Typical water-soluble compounds may include: Sacetates, oxalates, or nitrates of cerium and of S the alkali metals e.g. sodium potassium, or cesium.

E Chromium may be added as chromous nitrate Cr(N0 3 )3 9H 2 0. Bismuth may be added to the alumina as a 7 w% solution of Bi (NO 3 )3 .5H 2 0 in water which has been acidified with sufficient nitric acid to for- clear solution. It is possible to add all the metals of the two components separately or fn one operation.

The rare earth metals include elements of atomic number 57 to 71. This group which is sometimes referred to as the lanthanide series includes lanthanutm, neodymium, cerium, praeseodymiuir, samarium, dyspr(sium, and other. elements which are present in small quantities.

These metals are difficultly separable from ine another and may be available commercially in a mixture containing about 50 w% cerium, 20 30 w% lanthanum, 15 W% neodymium, 5 6 praeseodymium, a 4sess Usn.

about 5 w% of the remaining rare earth elements.

For purposes of the inrstant t is found that mixtures of rare earth K employed including those commonly avail naturally 1/1/ "1 iC- i i ;_V 12 St C t t ~C O C

CCC

,et I C c Iccr occurring mixtures which have not been separated into fractions. Pure cerium nitrate Ce(N0 3 3 .6H 2 0 is readily available at reasonable cost. It is the preferred source.

There may be 7 100 w% of the first component oxide that is crystalline. It is unexpectedly found that the agents with 40 100 preferably 60 say 67 w% crystalline oxide have better stability towards steaming that occurs in an FCCU regenerator as far as SO xmission control is concerned.

In operation of the FCCU, the charge hydrocarbon is heated to 800°F-1200°F (454°C-538 0 say 960°F (516°C) at atmospheric pressure, and amitted in vapor phise to the reaction zone (a reducing zone) wherein it contacts the fluidized powdered cracking catalyst composition which includ'es the FCC catalyst and the admixed porous refractory support bearing as a first component at least one of bismuth, chromium, or a rare earth metal such as cerium and as a second 20 component (ii) at least one alkali metal, preferably potassium, sodium, or cesium. The charge sulfurcontaining hydrocarbon is cracked to yield vapor containing lighter hydrocarbons including those boiling in the motor fuel range and (ii) hydrogen 25 sulfide and mercaptans. This stream is removed from the reaction zone and subjected to separation operations wherein the hydrocarbons are separated from the sulfurcontaining components.

In the reaction zone, there is laid down on the catalyst a deposit of coke-carbon in typical amount of 3.5 w% 5.0 say 4.2 w% of the total weigh, of the catalyst. The catalyst also accumulates solid, sulfur-containing material derived from the charge sulfur-containing hydrocarbon. Typical sulfur content of the spent catalyst may be 0.03 w% 0.04 say 0.03 w%.

The spent catalyst composition bearing the sulfurcontaining coke is passed to a regeneration zone I "I.

*r 4 *i

IS

4 s.\ 1 o;

II

ii i .g P. 61 C) C :Ir C 13 (oxidation zone) wherein it is contacted with oxygencottaining gas (oxygen-enriched air or more preferably, air). As regeneration proceeds at 1100F 1500°F (590 0 C 815°C), say 1350°F (732°C) and atmospheric pressure, carbon is burned off the catalyst to form carbon dioxide and carbon monoxide. When regeneration is carried out in the "excess oxygen mode", the amount of air used (typically 180 220, say 220 thousand Ibs per hour) is sufficient to produce a regenerator off gas containing 77 83 parts, say 79 parts of inert nitrogen) gas, 1 7 parts, say 5 parts of oxygen, less' than 1 part, of carbon monoxide, and 14 18 parts, say 16 parts of carbon dioxide.

The sulfur content of the catalyst particles 15 is also oxidized to form sulfur oxides SOx principally sulfur dioxide and sulfur trioxide.

SIn prior art operation wherein the catalyst composition contains only the FCC catalyst (and not the additive composition of this invention), the c' 20 regenerator off-,gas.. may contain.. 375-'5620, 'say '4680 w ppm sulfur dioxide and 520-780, say 650w ppm-sulfur trioxide, e.g. 1800-2400 ppm(v), say 2500 ppm(v) of sulfur dioxide and 200-300 ppm(v), say 250 ppm(v) of sulfur trioxide. This corresponds to 4 6 v%, say 5 w% of the sulfur which is present in the sulfurcontaining hydrocarbon charge.

In practice of the process of this invention wherein the catalyst composition includes the FCC S catalyst plus the additive composition of this invention, 30 the regenerator off-gas may contain 281-468 w ppm, say 375 w ppm sulfur dioxide and 39-65 w ppm, say 52 w ppm sulfur trioxide i.e. 135-225 ppm(v), say 180 ppm(v) of sulfur dioxide and 15-25 ppm(v) of sulfur trioxide, say 20 ppm(v). This corresponds to 0.3-0.'5 say 0.4 w% of the sulfur that is present in the ,ulfur-containing hydrodarbon charge.

In practice of a less preferred embodiment of .a i cI^ ,irin _ilTu ii 'i 1 r A7

S

i 1 14 this invention, the sulfur-removing composition containing porous refractory support bearing as a first component at least one of bismuth, chromium, or a rare earth metal such as cerium and as a second component (ii) at least one alkali metal, preferably potassium, sodium, or cesium may be absent from the FCC catalyst composition; and it may be maintained in a separate bed to which the standard FCC regenerator off-gases are passed and wherein the sulfur is fixed in solid form on the sulfur-removing composition. When this less preferred embodiment is employed, the fluidized particles which have adsorbed the sulfur at 1100F- 1500°F (595 0 C-815 0 say 1350°F (732°C) are regenerated as by passing an oxygen-containing gas over the catalyst at 850 0 F-1000F (454°C-538 0 C) say 920 F (493 0

C)

at atmospheric pressure.

St, In practice of the p,(uess of this invention, C much of the sulfur in the regenerator becomes fixed in solid form (as sulfate, etc.) on the porous refractory S 20 support'" bearing as a first component in eas.t one of bismuth, chromium, or a rare earth metal such as cerium and as a second component (ii) at least one alkali metal, preferably potassium, sodium, or cesium. The total sulfur content of the fluidized cracking catalyst composition in clud'ng the additive may be 0.03-0.04 say 0.034 w% (as S) based on total composition.

Sc, This sulfur-bearing regenerated catalyst compos-ition is preferably passed to the reaction zone, wherein, under the conditions of reaction, much of the sulfur thereon is released as hydrogen sulfide and mercaptans.

The overall result of this sequence of operations in the typical FCCU is that: 20-35 of the 2 w% of the sulfur in the charge hydrocarbon s desirably released as hydrogen sulfide and mercaptars 'n the reaction zone overhead; (ii) 0.3-0.5 of the 2 w% of the sulfur in the charge hydrocarbon< is found in the regenerator

A-

4 6

I

j~ 15 off-gas; and i ii the SOX content of the regenerator o ff gas i s reduced to 150-250 prim( vi, say 200 ppm(v) of prior operations undesirably yielding 2000-3000 ppm(v), say 2500 ppm(v).

Practice of the process of t h is invention will1 be apparent to those skilled in the art from inspection of the following examples wherein, as elsewhere in thi s specification, all1 parts are part by weight unless otherwise stated.

*I t a4 4 6 64 C 4 6 44 's 0 Is- I I YR I 1_ .11 1; Il- -"r 16 EXAMPLE I In this example, which represents the best mode 3 presently known of carrying out the process of this invention, the charge alpha aluminum oxide monohydrate (100 parts) is Catapal SB alumina marketed by Conoco.

This product is pure alumina (of 50 200 micron particle size) except for the following impurities:

TABLE

Component W TiO 2 0.12 S 15 SiO 2 0.008 2 Fe 2 0 3 0.005 SCarbbn 0.36 SSulfur 0.01 Na20 (plus Ill ,alkali metals'), i iLOi 004 22 c.

Water is added to this charge gamma alumina S" (100 parts) to form a paste. There is added thereto with mixing a solution of 4.30 parts of potassium hydroxide in 50 parts of water. A solution containing 25 50 parts of water and 9.28 parts of cerium nitrate (Ce(N0 3 )3 6112 0) is added to the potassium-containing alumina, mixing well, The mix is dried at 185 0

F

S 230 0 F (85 0 C 110 0 C) for 15 24 hours and then calcined at 1400 0 F (760°C) for 24 hours. Analysis showed that the composition contained alumina, 3 potassium, and 3 w% cerium, the latter two percentages based on the alumina. It was then pulverized to 200 micron size and mixed with nine times its weight of commercial equilibrium cracking catalyst Davison CBZ-1 brand 1 catalyst containing originally w% rare earth exchanged Y zeolite plus 85 w% sil ica-alumina.

-'C

r I ~-LP I

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17 This catalyst composition is evaluated for its

SO

x emission reduction capacity in a micro activity tester which simulates FCC conditions including the following:

TABLE

Condition Value Re.ction Zone Average Temperature Reaction Time Catalyst Inventory Pressure 0

C)

(min) (g) 960 516 atmospheric 4r 4r 4 *r *a .44 4~ 4* Nitrogen Flow rate ml/min Catalyst: oil (wt ratio) Regeneration Zone (Complete coke combustion mode) ou Air Flow ml/min Average Ca! Regeneration Time (min) 175 175 1300 705 Il.' I I 4 4 *144 A 14 4* 4 8t .4 *e 4 44 The charge to the reaction zone, in vapor phase at 920'F (473°C), is a synthetic gas oil containing 2 w% sulfur having the fsllowing composition: a t 44130 4r A

TABLE

Property n-dodecane Hexene-1 Benzothiophene W 90.6 8.4 o0 During evaluation, measurements were made of the SO x emitted in the regenerator off-gas, these being reported as w% of the sulfur contained in the sulfur-c'ontaining hydrocarbon charge and (ii) the sulfide It4 2 -1 -T 11 18

(H

2 S and mercaptans) contained in the cracked product leaving the reactor overhead as weight of the sulfur contained in the sulfur-containing hydrocarbon charge.

The results are tabulated in the Table following Example IX.

EXAMPLES I.I-IX In Examples II-III and V, other additives falling within the scope of this invention were prepared to give compositions as follows: Ue 41 *D i 'L Lt i Ie I U- V I I.

*1 r* -a 1 Example

II

III

V

Composition 3%Na/3%Ce/A1203 3%K/3%Bi/A1203 3%Na/3%Bi/Al203 2 3 In control Examples IV* and VI* VII* various formulations falling outside ,the scope of the .instant invention are made up in manner generally similar to the procedure of Example I. The material tested in control Example VIII* is Catapal SB alumina alone; and in control Example IX*, the material tested is the equilibrium Davison CBZ-1 Brand catalyst.

The results are as follows:

II

*a* aB

C

d ,.i -19

TAB!LE

Example Agent So x HgS 3%K/3%Ce/A1 2 0 3 0.43 2 II3%Na/3%Ce/A1 2 0 3 0).48 26 II3%K/3%Bi/A1 2 0 3 0.57 26 IV* 3%NaIAl 2 O0 3 ME8 25 V 3%Na/3%Bi /Al 0~ .52 VI* 4%Bi/Al 2 o 1.1 27 VII* 3%K/A1 2 0 3 0.85 27 VIII* AL 2 0 3 .4 29 IX* Eq. Davison CBZ-l 4.5 28 *Control Examples sox includies sulfiir dioxide and s ul1f ur trioxide in the regenerator o f f- g as reported as w% of the elsL s ul1f ur content of the sulfur-contai ni ng hydrocarbon charge.

20 H S includes hydriogen sulfide plus.. .merciptans i n the reactor off-gas, reported as w% of the s ulf u r content of the charge sul fur-cortai ni ng hydrocarbcon charge.

so SO concentrations are general ly measurable t o within a n experimental errop of an~d the a a concentrations noted in Examples I V, V and VII differ by non-significant differences.

From the above Table, it will be apparent that a It the following, conclusions may be drawn: thei compositions of t h is invention (Ex I I I and V) permit attainment of regenerator offgas containing less than lw% SO x which is substantially st better than that obtained by use of pure alumina (Ex VIII*) .or catalyst alone (Ex (ii) the most satisfactory resuIts achieved (Ex I) by use of the preferred composition of this invention are two 0.86/0.43), times b_-ette0,' than the best control examiple (Ex- IV);

O

I

20 (iii) the results achieved by use of this invention (Ex I) may be more than ten times (4.5/0.43) better than are attained by use of equilibrium Davison CBZ- 1 catalyst; etc.

EXAMPLES X*-XI 4* *O r 4

S

St 4F 4 St S 4C 4444O 5r 4 S4 4., *r The catalyst composition 'of Example I and one similar to Example IV* but containing 2w%Na/A1 2 0 3 both in combination with CBZ-1 were subjected to stability tests, by. exposing the .mixture to .water-saturated laboratory air for-prolonged times at 1350 0

F.

In the case of-: control. Exampilen, ,o.the. 2w%Na/.

Al 2 03 composition, the SO x content of regenerator 15 off-gas was about 0.74% at day 1 and increased up to about 2.08% at day 6.

In contrast, for experimental Example XI (using the catalyst of Example I, the 3%K/3%Ce/A1 2 0 3 composition), the SO x content was about 0.18% at day 1 and increased only to about 0.4% at day 8.

Results comparable to those attained by Example I may be attained if the catalyst composition contains the following in addition to the 3 w% potassium as the first component:

TABLE

4 *s 4 4 Example

XII

Composition 3 w% Bi 3 w% Ce on alumina 3 w% Ce on alumina

XIII

;r ~~tIULuu i I 21 EXAMPLE XIV*-XV In this pair of comparative Examples, FCC operations were carried out using an Isthmus vacuum gas oil containing 1.44 w% sulfur utilizing a reactor temperature of 960°F and a regenerator temperature of 1350 0

F.

In control Example XIV, the catalyst contained the Davison CBZ-1 brand of commercial catalyst.

In experimental Example XV, the catalyst contained 3 w% of additive containing 3 w% potassium and 3 w% cerium on gamma-alumina.

Using the control system, the SO x content of the regenerator off-gs averaged 854 wppm. Using the experimental system, the SO content of the S 15 regenerator off-gas averaged 566 wppm an improvement of 34%.

t c Ct EXAMPLE XVI In this Example, the charge alpha aluminum oxide monohydrate (100 parts) is Catapal SB alumina marketed by Conoco. The surface area is 250 m 2 This product is pure alumina (of 50-200 micron particle size) except for the following impurities:

TABLE

Component W 7 TiO 2 0.12 SiO 2 0.008 Fe 2 0 3 0.005 Carbon 0.3 Sulfur 0.01 (plus all alkali metals) 0.004 This catalyst composition is evaluated for its

SO

x emission reduction capacity in a micro activity xa 22 tester which simulates FCC conditions including the following:

TABLE

Reaction Zone Condition Average Temperature 6r 6: 6* t t r( 6 Reaction Time (min) Catalyst Inventory (g) Pressure Nitrogen Flow rate ml/min Catalyst: oil (wt ratio) Regeneration zone (Complete coke combustion Air Flow ml/min Average Temperature (OF) Regeneration Time (min) The charge to the reaction zone, in at 920°F (473°C), is a synthetic gas oil 2 w% sulfur having the following composition: Value 960 516 atmospheric 175 mode) 175 ca 1300 705 vapor phase containing ii *r *166 46 4 46 66 66 4 6*

TABLE

o t t 4 6 Component n-dodecane Hexane-l Benzothiophene 90.6 8.4 During evaluation, measurements are made of the SO x emitted in the regenerator off-gas, these being reported as w% of the sulfur contained in the sulfur-containing hydrocarbon charge and (ii) the sulfide (H 2 S and mercaptans) coitained in the cracked product leaving the reactor overhead- as weight of the sulfur contained in the. sulfur-containing hydrocarbon charge.

0

I

23 0

S

S

*5

S

S*

0S *0 0 S eO.

Si S ,c A solution is prepared so that 100 ml of it contains 17.5g of cerium nitrate Ce(NO 3 )3 .6H 2 0.

ml of this solution is added to 93.4 g of dry alumina with mixing so as to form a moist mull.

This is dried at temperatures ranging from ambient up to 212 0 F. To this product is added 85 ml of a KOH solution that contains 1.Og of KOH per 100 ml of solution. The mix is dried at 185-230°F (85-110 0

C)

for 15-24 hours and then calcined at 1400°F (760 0

C)

for 24 hours. Analysis shows that the composition agent contains alumina, 0.6 w% potassium, and 4..8 w% cerium (corresponding to 5.9 w% cerium oxide, CeO2 The crystal size of the Ce02 is 66 Angstrom Units. The crystalline CeO 2 content is 3.9 w%.

15 The product is then pulverized to 50-200 micron size.

For laboratory microact'ivity testing, one part of this agent is mixed with nineteen parts by weight of Davison CBZ-1 Commercial equilibrium cracking catalyst.

EXAMPLE XVII The agent of Example XVI is steamed for 24 hr:*rs at 1470°F prior to mixing with cracking catalyst.

The agent contains CeO 2 crystals that are 85 A. U.

in size and the agent contains 2.6 w% of crystalline CeO 2 For laboratory testing for activity, one part of this agent is mixed with nineteen parts by weight of Davison CBZ-1 equilibrium cracking catalyst.

EXAMPLE XVIII The product of Example XVIII is prepa ed by making a solution such that 100 ml of it contains 16.8 g of cerium nitrate Ce(N0 3 )3 .6H 2 0. 85 ml of this solution is added to 93.1 g of dry alumina with mii 1 to form a moist mull. This is dried at temperatures ranging from ambient up to 212°F. To i i likii ~l*rJ- 24 this product is added 85 ml of a KOH solution that contains 1.7 g of KOH per 100 ml of solution. The mix is dried at 185-230°F (85-110°C) for 15-24 hours and ther: calcined at 1100F for 2 hours. Analysis shows that the composition contains alumina, w% potassium, and 4.6 w% cerium (corresponding to' 5.6 w% CeO 2 The crystal size of the Ce02 is 63 A. U. The crystalline CeO 2 content is 4.1 The product is then pulverized to 50-200 micron size.

For laboratory microactivity testing one part of this agent is mixed with nineteen parts by- weight of Davison CBZ-1 commercial equilibrium cracking catalyst.

EXAMPLE XIX *o 9 The agent of Example XVIII is steamed for 24 hours at 1470°F prior to mixing one part with nineteen parts Davison CBZ-1 equilibrium cracking catalyst.

The crystal size of the CeO 2 formed was 85 A. U.

The crystalline CeO 2 content of the agent is 3.7 w%.

EXAMPLE XX The agent of Example XX is prepared by using Catapal SB alumina. A solution is prepared so that 100 ml of it contains 11.3 g of cerium nitrate Ce(N0 3 .6H 2 0. 85 ml of this solution is added to 0 92.6 g of dry alumina with mixing s-o as to form a 0 moist mull. This is dried at temperatures ranging from ambient up to 212 0 F. To this product is added ml of a KOH solution that contains 5.0 g of KOH per 100 ml. of solution. This mix is dried at 185- 3 5 230F (85-,110C) for 15-24 hours and then calcined at 1400 0 F for 24 hours. Analysis shows that the composition contains alumina, 3.0 potassium and L I kMTrC trno 25 3.1 w% cerium (corresponding to 3,8 w% cerium oxide, CeO 2 The crystal size of the Ce02 is 94 A. U.

The crystalline CeO2 content is 3.9 This material is evaluated in a microactivity evaluation unit by adding one part of the agent to 9 parts of equilibrium Davison Cracking catalyst CBZ-1. The catalyst is also evaluated in a pilot-unit size unit by mixing one part of the agent with 32 'parts of the equilibrium cracking catalyst inventory.

EXAMPLE XXI The agent of Example XXI is prepared by making a solution such that 100 ml of it contains 21.9 g S 15 of cerium nitrate (Ce('N )3 .6H 2 85 ml of this solution is added to 91.4 g of dry alumina with mixing so as to form a moist mull. This is dried to temperatures ranging from ambient up to 212°F. To this is added ml of a KOH solution that contains 1.7 g KOH per 100 ml of solution. The mix is dried at 185-230°F ;(85-110°C) for 15-24 hours and then calcined at 1400°F (760 0 C) for 24 hours. Analysis shows that the coiiposition contains alumina, 1.0 w% potassium, and 6,0 w% cerium (corresponding to 7.4 w% cerium oxide, CeO 2 The crystal size of the CeO 2 is 123 A. U. The crystalline CeO 2 content is 6.5 The product was then pulverized to 50-200 micron size. Ten parts of the agent were then mixed with 90 parts of equilibrium cracking catalyst CBZ-1.

EXAMPLE XXIi The age t of Example XXII I's prepared by making a solution, such that 100 ml fit contains 8.75 g of cerium nitrate Ce(N0 3 3 .6H 2 0. 85 ml of this solution is added to 9,3 5 of ,dry alumina .wi.th imixing.. so n as to form a moist mull. This is dried at temperature ranging from ambient up to 212 0 F. To this product

\\N

A

i7 I3

I.-

r- i I liai i- 4 4 0 1 26 is added 85 ml of a KOH solution that contains of KOH per 100 ml of solution. The mix is then dried at 185-230°F (85-1100C) for 15-24 hours and then calcined at 1400°F for 24 hours, analysis shows that the composition contains alumina, 2.4 w% cerium (corresponding to 3.0 w% cerium oxide, CeO 2 and w% potassium. The crystal size of the CeO 2 could not be accurately determined because of the great breadth of the CeO 2 diffraction line. The agent contains about 0.2 w% .crystalline CeO 2 The .overall crystal size is about 10 A. U. This material is evaluated by mixing one part agent with nineteen S parts by weight of commercial Davison CBZ-l equilibrium S cracking catalyst.

Vt C, C7 t EXAMPLE XXiI 6 ft ter It I 4 i 4 r Ia 1 1* The agent of Example XXIII is steamed at 1470 0

F

for 24 or 48 hours. The agent is found to contain 20 CeO2 crystals that are about 10 A. U. in size. This material is evaluated by mixing one part agent with nineteen parts by weight of commercial Davison CBZ- 1 equilibrium cracking catalyst.

The 'ata'yst so prepared are all tested in a manner comparable to that of Example XVI. The results are as follows: k ii.

27

TABLE

Example Total Content, Crystalline CeO 2 Feed ii Ce CeO 2 K Size Content, w% as SO x XVI 4.8 5.9 0.6 66 3.9 0.1 (b XVII 4.8 5.9 0.6 85 2.6 0.3 (b XVIII 4.6 5.6 1.0 63 4.1 0.2 (b XIX 4.6 5.6 1.0 85 3.7 0.3 (b XX 3.1 3.8 3.0 94 3.9 0.4 (a t C r SXXI 6.0 7.4 1.0 123 6.5 0.6 (a XXII 2.4 3.0 3.0 "10" 0.2 0.2 (b XXIII 2.4 3.0 3.0 "10" 0.2 0.5 (b Evaluated with 10 parts agent plus 90 parts equilibrium C3Z-1 Evaluated with 5 parts agent plus 95 parts equilibrium CBZ-1 Control sample From the above Table, the following conclusions may be drawn: Examples XVI and XVIII, which show the best mode presently known, show a Ce-K agent containing crystals of cerium oxide of crystal size of about Angstrom Units permits operation to yield regenerator off-gas which desirably contain only 0.1 0.2 w% of the feed-tu'lfurc(as SO';- (ii) Examples XVII and XIX show that the agents of Examples XVI and, XVIII withstand best the steaming

S

-e I -28 that an agent would encounter in an FCCU regenerator.

Regenerator off-gas contains 0,3 w% of the feed sulfur.

(iii) Example XXII and XXIII show a Ce-K agent cctaining crystals of cerium oxide of about 10 Angstrom Units permits operation to yield regenerator offgas which desirable contain only 0.2 w% of the feed sulfur (as SO However, the steam stability of this agent is poorer in that stelaming causes the agent to permit 0.5 w% of the feed sulfur to escape in the regenerator off-gas.

(iv) Example XXI, which is outside the scope of this inventio.n (the crystal size is 123 AU) may give some improvement (0.6 w% of the feed sulfur C is emitted as SO but it gives less improvement than may be attaind by the instant invention.

c Example XXI is'tested in 10 w% concentration I (to yield whereas in Example XVI, the concentration t is 5 w% (to yield Thus the degree of improvement may be equal to a factor of 12.

EXAMPLE XXIV The agent of Example XXIV is prepared by using Catapal SB alumina. A solution is prepared so that 100 ml of it contains 27.2 g of chr as nitrate Cr(N0 3 )3 .9H 2 0. 85 ml of this solution is added to 92.0 g of dry -alumina with mixing so as to form a moist mull. This is dried at temperatures ranging from ambient up to 212 0 F. To this product is added 85 ml of a KOH solution that contains 5.0 g of KOH per 100 ml of solution. The mix is dried at 185- 230°F (85-110 0 C) for 15 24 hours and then calcined at 1400*F for 24 hours. analysis showed that the composition contained alumina, 3.0 w% potassium and 3.0 w% chromium (co'responding to 4.4 w% chromic oxide, Cr 2 0 3 i .f

Claims (9)

1. A process for removing a sulfur oxides component from a mixture of gases containing sulfur oxides which comprises contacting said mixture of gases containing ,ulfur oxides at 800°F-1500°F with a catalyst composite containing a porous refractory support bearing as a first component (i) to 10 wt.% of at least one of bismuth, or a rare earth metal, and as a second component (ii) 0.4 to 10 wt.% of at least one compound containing alkali metal.

2. A process as claimed in Claim 1 wherein said first component is in the form of crystals of oxide of crystal size less than 90 Angstrom Units.

3. A process as claimed in Claim 1 or 2, wherein said porous refractory support is alumina. 15

4. A process as claimed in any one of the preceding Claims, wherein said first component is bismuth or cerium.

5. A process as claimed in any one of the preceding Claims, wherein said second component is potassium or sodium.

6. A process which comprises contacting a 20 sulfur-containing hydrocarbon charge stock in a reaction zone at 800°F-1200 0 F with a fluidized particulate cracking catalyst composition including a cracking catalyst and a catalyst composite containing a porous refractory support bearing as a first component 0.5 to 10 wt.% of at least one of bismuth, or a rare earth metal, and as a second component (ii) 0.4 to 10 wt.% of at least one compound containing alkali metal, thereby forming reaction product containing normally liquid cracked hydrocarbon products including, as hydrogen sulfide and mercaptans, a 30 portion of the sulfur from said sulfur-containing hydrocarbon charge stock and (ii) spent catalyst composition bearing sulfur-containing coke; removing from said reaction zone cracked hydrocarbon products in admixture with hydrogen sulfide and mercaptans; separating said cracksec hydrocarbon products from the hydrogen sulfide and mercaptans in 8aid admixture; 4L *0 0 S. 0 *5 S o476s/as yC OFF% I-:i jr! a 4 3 -30- contacting said spent catalyst compostions bearing sulfur-containing coke in a regeneration zone with oxygen-containing gas at 1100 0 F-1500 0 F thereby forming regenerator off-gas of decreased content of oxides of sulfur and regenerated cracking catalyst containing a solid composition of sulfur, and passing said regenerated catalyst to said reaction zone wherein sulfur on said regenerated catalyst composition is converted to hydrogen sulfide.

7. A composition of matter comprising a cracking catalyst and from 1 to 10 based on total weight of a porous refractory support bearing as a first component (i) to 10 wt.% of at least one of bismuth, or a rare earth metal and as second component (ii) from 0.4 to 10 wt.% of at least one alkali metal compound.

8. A composition of matter as claimed in Claim 7 wherein said first component is in the form of crystals of oxide of crystal size less than 91 Angstrom Units.

9. A process as claimed in claim 1 substantially as 20 herein described with reference to any one of Examples I, Ii, III, V and XV. A composition of matter as claimed in claim 7 substantially as herein described with reference to any one of Examples I, II, III, V, XV, XVI, XVII, XVIII, XIX, XX, 25 XXII and XXIII. DATED this 12th day of February, 1990 TEXACO DEVELOPMENT CORPORATION By their Patent Attorneys 30 GRIFFITH HACK CO. 4 *c I tt 4 6 *I 4 .444 44 44 4 It I t* 4 I It 41 I I I I I 4e 4 4e* t I 4 0476s/as r i