GB2216896A - Catalytic cracking process - Google Patents

Description

1 CATALYTIC CRACKING PROCESS The present invention falls within the scope

f luid catalytic cracking of hydrocarbon charges.

n.-).1 '1 (,j ' 0 Lz 1 L' of The process which is currently the most commonly used is the process known as fluid catalytic cracking (FCC). In this type of process, the hydrocarbon charge is vaporized and contacted with a cracking catalyst at a high temperature, the latter being kept in suspension in the charge vapors. After the required molecular range has been reached by cracking, with a corresponding decrease in boiling points, the catalyst is separated from the obtained products, stripped, regenerated by combustion of the formed coke and then recontacted with the charce to be cracked.

Among the example those charges that can be used, there are for with final boiling points of about 4000C, such as vacuum gas-oils, but also heavier hydrocarbon oils, such as crude and/or stripped petroleums, and atmospheric or vacuum distillation residues. If need be, these charges can have been subjected to a preliminary treatment such as, for example, a hydrotreatment in the presence of cobalt-molybdenum or nickel-molybdenum type catalysts, for instance. The preferred charges of the invention are those containing fractions usually boiling at 7000C and over, which can contain high percentages of 2 asphaltenic. products and which carbon content up to 10% and over.

can show a Conradson Among the catalysts which can be used as described above, the following can be cited: cracking catalysts of the crystalline aluminosilicate type, certain silicaalumina, silica-magnesia and silica-zirconium types.

Catalytic cracking reactions are more and more often applied nowadays to the treatment of charges that become always heavier. Such charges are therefore difficult to vaporize, which leads to substantial coke formings due to the non-vaporized part of the charge which has nevertheless beeb introduced into the reactor. The main drawbacks that can be cited are the yield decrease the valorizable products, an increased production of regeneration gas, an increased air consumption and catalyst circulation, which leads to an oversizing of the reaction-regeneration unit.

concerning it is essential that vaporization in the reaction additional coke forming leads production which must be eliminated.

charge vaporization depends on the mixture temperature of the catalyst-charge unit and on the hydrocarbon partial an excellent zone can be obtained. The to an inadequate calories charne A satisfactorv pressure which is used in the reaction zone, as well as on the surrounding technology. It is well-known that the nature and the development of the nozzles ha,.,e an effect at474 UT:las-4T sassa-jdxa.4T luol-43caj DTwJaw-4opua U12 ST 4T a:juls Ipue paz)npo.Ad snt4-4 s- uoT4jeaj 5uTIneiD aWl Z-Cl d4e- MOI e 14-41M JaSTJ aq-4 G la^al STq-4 -4e 5UT-4eIn:)jT3 aj n-4 x r w -4 5 A 1'e: L:)-a 5-A L2W D aq-4 & = I- ueq: -A a L4 E2T L4 Z-L a-in-4ejadwa:l e "3,le paL4:),2a-i snL4-4 sT wnTiqTITnba UV -abieqD 0;-ji2d -4scal c: a uoT4ezT-4ade^ at4: sesne::) L4:iTt4m lab-jeq:) aq-4 pue 4s/,1e,4L=:3 at44 uaam:aq s-in:):)o a5uet4:)xa 4eat4 k ú sadrd 4aluT a5-jeqD aq4 La la^al aq4 4?:no paTjjeD ST:sAle:ez) aLl: CJ Pue e5-4L2L4-J ak44 c Bulx-rw aLl-1 = CJ a-4e-i mc)l..k e pue =_L a-jn4e-4adwa:

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at4'4 sip sa^ojdwT ucT4ezTjode^ aq: a D UT 5 lia-4awejed at44 ST a.An-4c-iedwa: aL44 'uc3T-4ezTjc3de^ a E) J L'k4::) at4:ucdn -:)e Aew L4:)TWm 5-4a-4awe-4ed snc)-r-ii2^ aLl-4buc)wv -4 SA 1 L- -4 L=:D au0Z a t4 -4 ULL44 JaL45TL4 papua-4xa a t4:.4- 0 -rI àL: IZ: ad-,d l4q Tm SuoT-4eln:)lie:i:)TweuApc)wjaq: uc spuadap q3Tqm 1:TwTI ucT;ezT-4cde^ aq: U0 -4ou -4nq a4ej ucT4czTjode^ aq4uc 52 03 GL 1 j h 4 form of a heat absorption. In the upper part of riser 1, a T-shaped device 4 is for example used to separate on one hand the reaction gas effluents and, an the other hand, the catalyst particles.

The unit control parameter is temperature T.4 (lower than T..=) at the riser outlet. For a determined temperature Tw (for example 520OC) and for a determined heat reaction (for example A H), with a determined flow rate, a 8 T will correspond to the determined A 'H. That is to say that, when the operator has determined T4 and AH, a temperature Tz, which is higher than T., follows from the determined values. If, for any reason, T decreases, the regulated (generally by modifying the circulating,catalyst flow rate), in order to make temperature Tz rise again, which leads T.4 to rise up to the temperature that Z.

was initially chosen by the operator. In French Patent in order to make T-s rise, a higher amount of to the system, either, for catalyst circulation or by the charge. But, while temperature also rises, the operation since the aim is is determined by thermodynamic cracking reactions (determined 4 heat input in the reaction system must be 2,604,720 calories must be given example, by increasing the increasing the temperature of doing this, the riser outlet which is not the point of to set T, at a value that and kinetic factors of the conversion). The process of French Patent 2,604,720 consists in injecting a fluid through pipe (5), down stream, that is to say above the charge injection point -k (pipes 3), in order to supply system (0=) with calories and thus be able to maintain temperature T.4 at the initially determined value.

lo Injecting said fluid above the charge injection point allows to increase T=, contrarily to what would happen if the injection was carried out mixed with the charge, at the level of the charge injection.

This temperature T= control is thus performed by injecting into at least one pipe 5 any appropriate fluid, which allows to increase the catalyst circulation or the charge temperature without increasing temperature T^. This brings about a higher heat level near level A (obtaining a temperature T'-2; higher than T-z, thus higher than T,,) which improves the charge vaporization.

This temperature control method, mixing the charge and the catalyst with an appropriate fluid, is today conventionally called "mixed temperature control" (MTC). This method is different from the conventional methods called "without mixed temperature control" methodsq in which no said fluid is injected.

The fluid which allows to achieve this control is a gas or an appropriate liquid. It can be a gasoline from a neighboring reforming unit, an appropriate gas, for example propene, etc. It can also be a part of the reaction effluent from riser 1. Such an effluent is generally fractionated into various cuts as it has already been described in 1 the patent application; these 6 effluents particularly contain a gasoline, a light cycle oil (L.C.O.), a heavy cycle oil (H.C.O.) and a slurry.

In French Patent 2,604,720, at least part of of the L.C.O. or of it will a given or L.C.O.

the the gasoline or preferably parl H.C.O. is recycled. More particularly, preferred to recycle an H.C.O. because, for H.C.O. mass (compared to an identical gasoline mass), there are less molecules in the H.C.O. as in gasoline or in L.C.O.; thus, the riser dimensions will be smaller than in the case of a gasoline or a L.C.O.

Besides, a H.C.O. has the advantage of being a valorizable product, that is to say a product which, while favoring an improved charge vaporization, will be present again in the reaction zone and will then be subjected to another cracking process, thus improving the overall valorizable products yield of the total initially -;W introduced cut.

be The advantage of recycling an H.C.O. (optionally a L.C.O.) is that the recycled product, which comes from a fractioning zone, is clean. This would not be the case with the slurry from the bottom of the fractionator, even if this slurry was treated in order to be purified (which would give a "clarified oil", C.O.).

In a general way, it is important to choose a temperature difference ranging from 2 to 1500C, more specifically from 30 to 700C, between T- and T4. This h 7 difference in temperature essentially depends on the nature of the charge.

In a preferred way, T'_.-T-z ranges from 2 to 301C, more particularly from 1E3 to 250C, the difference between T:-- and T^ being preferably selected between 20 and 701C.

The recycle ratio of part of the reaction effluent represents 1 to 100% by volume of the charge. When part of the H.C.O. is recycled, the recycled part preferably represents from 10 to 50% of the charge.

extended zone least one zone, down stream Besides, French Patent Application 96/00763 of January 21 1999 describes 15g-e Fic.2 cf t-EDrese.nt patent application) a fluidized or a carried Ded catalytic cracking process of a hydrocarbon charge, performed in an extended, tubular and appreciably vertical zone (1), the catalyst particles being introduced through a pipe (2) at the lower end of the and the charge being introduced through at pipe (3) into the 9 that is to say at a level B which is located higher than the catalyst particles inlet point, said catalyst particles being separated from the reaction effluent at the upper end of the extended zone, the reaction effluent being then fractionated in order to obtain various fractions, particularly LPSs, a gasoline, a L.C.O. and an H.C.O., the process comprising, on one hand, injecting a gasoline through at least one pipe (3a) into the extended zone at a level C down stream, that lower part of the extended a is to say higher than the catalyst particles inlet point and lower than level B, which is the charge inlet level, said gasoline representing 5 to 50% by volume of the charge, and on the other hand using as a catalyst a product containing at least one zeclite of the erionite family.

The invention, illustrated by Figure 3, relates to a fluidized or a carried bed catalytic cracking process of a hydrocarbon charge, in an extended, tubular and appreciably vertical zone (1), i the catalyst particles circulate upwards (ig.3) or downwards; the catalyst particles are introduced at a temperature TI., generally exceeding 6000C, at an end of the extended zone, through at least one pipe (2), the liquid charge beinc L.introduced at a temperature T= into the extended zone, through at least one pipe (3) opening into said extended zone at a level 8 located lower than the inlet level of the catalyst particles, a partial vaporization of the charge taking place at a temperature Tz higher than T=, thanks to the heat exchange between the catalyst particles and the liquid charge; the catalyst particles are then separated from the reaction effluent at the other end of said extended zone where the temperature T^ is lower than Tz; the reaction effluent is then fractionated in order to obtain especially LPGs, a gasoline fraction, a L.C.O. fraction, an H.C.O. fraction and generally a slurry.

n which the charge and 1 9 The process comprises using a catalyst containinn a zeolite of the er. ionite family and it also ccmprises (a) on one hand, recycling a fluid containing at least a part of said H.C.O. fraction into the extended zone through at least one pipe (5), at a level A located lower than level B in order to obtain at level A a temperature T'z > T= allowing to vaporize, totally or for the most part, the charge which would otherwise not be vaporized at level B at temperature T-., and (b) an the other hand, injecting a gasoline, for example a recycling containing at least part of a fraction gasoline extended C located particles point is.

selected among the group formed by a and LPGs (paraffin with C7 and/or C4), into the zone through at least one pipe (3-a), at a level lower than the inlet point of the catalyst and lower than level B where the charge inlet T.z-T.4 generally ranges from 2 to 1500C, or from 2 to 1000C, T'z-T-z. ranging from 2 to 300C, preferably from 18 to 250C, especially when Tz-T4 ranges from 30 to 700C or from 20 to 700C, or, for some charges, from 10 to 450C or from 4 to 300C.

Said fluid (recycled at level A) generally represents 1 to 100% by volume (preferably 2 to 10%) of the charge, or 10 to 50% said fraction represents 5 10 to 30%.

according to the charge, and which has been recycled at level C,' to 50% by volume of the charge, preferably The following examples illustrate invention.

the present EXAMPLES

In these examples, the heavy charge to be treated shows the following characteristics:

Density (20OC) 0.968 Viscosity (60OC) solid Cst (BOOC) 119.9 (119.8 MM:--/s) (10011c) 52.2 (52.2 mm2/s) Conradson % 5.1 Na ppm 2 Ni ppm 11.6 V ppm 1.2 c % 86.9 H % 12.2 N % 0.35 S % 0.21 Basic N % 0.055 Aromatic C % 22.3 Aromatic H % 2.7 Simulated distillation (OC) % 367 % 399 % 436 40 % 495 % 575 FBP - In the first series of tests, the catalyst used is an ultrastable conventional USY zeolite diluted in matrix based on a mixture of a silica-alumina rich in silica and on kaolin (30% by weight of kaolin in relation to the catalyst mass).

Further catalyst characteristics:

Total alumina Surface in m.g-Rare earth oxides Na=O V Ni Fe 37 % by weight 110 1.6 % by weight 0.3 % by weight 4,800 ppm 2,900 ppm 10, 21-00 ppm 11 In the first test, a conventional FCC process is carried out in a riser, without H.C.O. recycling and without gasoline injection.

- catalyst injection temperature 7710C - charge injection temperature 2100C - riser temperature next to pipe 3 5370C - temperature at the top of the riser 51611C - C/0 = 6, in which C is the catalyst flow rate and 0 the heavy charge flow rate (catalyst/oil ratio).

A second test is carried out as in the first test, but a straight-run gasoline is injected upstream from the charge injection paint (Fig.2). This straight-run gasoline is a 50-1600C non-olefinic cut composed of:

paraffins % by weight clefins % by weight naphthenes % by weight aromatics % by weight 5E3 0 29.5 12.5 This gasoline contains less than 2 % by weight of compounds with 5 carbon atoms. The injected gasoline mass represents 20 % of the cracking charge mass. Temperature T= near the inlet point of pipe 3 is 537OC; temperature T.4 at the top of the riser is 5160C.

12 The third test is carried out as in the first test but according to Figure 1; thus, 40 % of the obtained heavy diluent is recycled through pipe (5). The catalyst grains are injected through pipe (2) at 7710C and the charge is injected through pipe (3) at 2100C. Temperature T= in the riser, near pipe (3) inlet point, is 5376C. Temperature T4 at the top of the riser is 5160C. Temperature T= is 5566C.

A fourth test is carried out according to the second and to the third tests at the same time, in compliance to the technique illustrated by Figure 3.

The operating 'conditions of the last three tests were the following:

catalyst injection temperature T2. (OC) charge injection temperature T= (C) temperature T:_ at level E (C) temperature T.4 (OC) 771 210 537 516 In the third and in the fourth tests, temperature T':3 at level A of pipe (5) is 5560C. The gasoline is injected during the fourth test at 2100C, in the same proportions as in the second test.

The results that have been obtained with the four tests are shown in the following table. Yields are expressed in % by weight in relation to the fresh charge in the first and the third tests and in relation to the 13 fresh charge + the the fourth tests.

injected gasoline in the second and In the second and in the fourth tests, the injected gasoline conversion is close to 56 / by weight.

lst TEST 2nd TEST 3rd TEST 4th TEST gasoline H.C.O. gasoline injection recycling injection and HCO recycling weight weight weight weight - H=S 0.10 0.10 0.10 0.10 H= + Ca. + C= 4.6 5.5 3.2 4.0 C= 1.4 2.0 1.4 2.0 C== 4.4 6.5 4.6 6.8 saturated Ch. 4.1 5.1 4.3 5.3 (of which iC.4) (3.3) (4.2) (3.5) (4.2) total C.4= 5.9 9.3 6.1 1. i', Total gases 20.50 28.50 19.7 27.7 Cc gasoline 44.9 60.0 45.4 60.70 (221OC) L.C.O. 15.1 15.8 15.4 16.0 -(221-350OC) H.C.O. and 11.4 12.2 11.6 12.3 slurry heavy diluent (3500 C-) Coke 8.1 E3. 5 7.9 9.3 Conversion 73 73 Total 100 125. 100 125 Gasoline research 92.2 90.9 octane number Gasoline motor octane number E30.1 79.5 Injecting a light straight-run gasoline at the bottom of the riser on a very hot CatalYst allows to obtain an improved propvlene yield as well as an improved yield in olefins with 4 carbon atoms.

14 Simultaneously injecting recycling (4th test) does substantially better results a gasoline and an H.C.O.

not allow to obtain but it leads to highly appreciable gains (especially in propylene, unsaturated hydrocarbons with 4 carbon atoms and gasoline) without raising the coke and slurry contents in high-capacity industrial units.

The 2nd and the 4th previous tests are carried out again in a second series of tests (tests 2a and 4a) in the same operating-conditions, but solid is added to the catalyst which offretite-based solid is prepared as an offretite-based was used above. This follows:

The results appear in the following table, test 4a complying with the present patent application.

g of a synthetic offretite the main dodecagonal channels opening of Zhich is 6.4 x 10-J-Izl m, (W. ME1ER and D.H. OLSON, Atlas of Zeclite Structure Types, 1978), with a Si0=1Al=0=_ molar ratio of 8, containing 9.9% by weight of potassium and 2.8% by weight of tetramethylammonium under dry air, at a flow rate of 3 at 5500C, in order to remove TMA- ions, were calcined 1/hIg, for 2 hours cations.

The obtained product (reference 1A) was then exchanged three times with a 2 M ammonium nitrate solution, at 1000C for 4 hours, under stirring, with a solution volume - dry solid weight ratio (VIW) of 5.

The obtained solid (reference 1B) contains 2.8% by weight of potassium and has a SiO=/A1=0.z molar ratio of 9. This solid 1S is called Product 1.

The main dodecagonal channels opening of the offretite has not been modified by the treatment.

The following processes are carried out on the previously obtained offretite (Product 1) containing 2.E3/. by weight of potassium:

First cycle:

- self-steaming obtained) at 5500C for 2 hours (Product 2A is - 2 successive cationic exchanges with 2 M NKaNOz under the conditions described in example 1 (Product 2E is obtained).

Second cvcle self-steaming obtained) at 6500C for 2 hours (Product 2C is cationic exchange with 2 M NH4NC)z under the conditions described in example 1 (Product 2D is obtained) - 2 successive acid etchings with 0.23 N HCI followed by 0.36 N HCl at IOOOC for 4 hours, with a V/W ratio of 10 (Product 2E is obtainea after the first acid 16 etching and Product 2F is obtained after the second acid etching).

At the end of these various treatments, the crystallinity of Product 2F remains excellent; its potassium content is 0.7% by weight, its SiO=/A1=0z is 25 and its water adsorption capacity is 15% (P/Po = 0.1). Solid 2F is called Product 2.

14 liters of water, 600 g of dry pseudoboehemite gel marketed by CONDEA and containing about 75% by weight of alumina, as well as 2.5 kg of a silica-alumina calcined and ground to an average particle size of 6 microns are introduced into a 20 liter vessel. 160 cm3 of pure concentrated nitrkc acid are added to the previous mixture which is constantly stirred and then heated at 500C for 45 mn, still under constant stirring. 740 g of the offretite whic12 was previously_ prepared are then added to the mixture and stirring is continued for 15 mn. The mixture is then atomized in a NIRO atomizer, with an inlet temperature of 3800C and an outlet temperature of 1400C.

The finished solid comes in the form of microspheres with a granulometry that can be compared to that of commercial fluidized bed cracking catalysts. It contains 20% by weight of offretite in relation to the dry product.

17 Such a solid is generally calcined for 16 hours at 7500C under an atmosphere consisting of 100% steam before being used for cracking.

This solid is then added to the catalyst which has been previously used and which will contain 20% by weight of this solid, that is to say 4% of the pure offretite that has been prepared above. The obtained catalyst complies with the invention.

ill 1 m In tests 2a and 4a, the injected gasoline conversion is also 56% by weight.

An offretite with a SiO=/A1=0__ molar ratio of 25 is prepared as follows H=S H= + Cl. + C= C:-_ CZ= Saturated C., (of which iC,.;.) Total C.Q.= Total gases Cc gasoline (221OC) L.C.O. (221-350OC) H.C.O. and slurry heavy diluent (350OC-) Cake Conversion TOTAL Gasoline research octane number Gasoline motor octane number TEST 2a Gasoline injection Weight 0.10 6.4 3.0 10.3 6.1 (4.9) 12.7 38.6 52.9 13.9 11.0 8.7 TEST 4a Gasoline injection and HCO recycling Weight 0.10 4.7 3.0 10.6 6.2 (5.0) 12.7_ 37.2 52 15.6 11.9 E3. 4 is Test 4a shows an improved C== yield with no increase in H=, Cl, and C= light gases.

1 ii, 19

Claims (7)

1. Fluidized or carried bed catalytic cracking process of a hydrocarbon charge in the presence of a catalyst containing at least one zeolite of the erionite family, in an extended, tubular and appreciably vertical zone, in which the charge and the catalyst particles.circulate upwards or downwards, the catalyst particles being introduced at a temperature Ts. at one end of the extended zone through at least one pipe, the liquid charge being introduced at a tamperature T= lower than Tj into the extended zone through at least one pipe opening into said extended zone at a level 8 downward from the catalyst particles inlet level, a partial vaporization of the charge occurring at a temperature T- hiqher than T2, thanks to the heat exchange between the catalyst particles and the liquid charge, the catalyst particles being ther7 separated from the reaction effluent at the other end of said extended zone where a temperature T4 lower than T-3 is to be found, the reaction effluent being then fractionated in order to obtain especially LPGs, a gasoline fraction, an L.C.C. fraction and an H.C.O. fraction, a process which also comprises (a) on one hand, recycling a fluid containing at least part of said H.C.O. fraction into the extended zone, through at least one pipe, at a level A downstream from level -B, in order to get at level A a temperature T'- z higher than T-3 allowing to vaporize the total or part of the charge which would not have been vaporized at level B at temperature T= and (b), on the other hand, injecting a gasoline into the extended zone through at least one pipe, at a level C downstream from the catalyst particles inlet level and upstream from charge inlet level B.

2. A process according to claim 1, wherein T?_,-Ta ranges from 2 to 1500C, T':n-T.z ranging from 2 to 300C.

3. A process according to claim 1, wherein T'-z-T= ranges from 1E3 to 250C.

4. A process according to claim 2, wherein said fluid (recycled at level A) represents 1 to 100% by volume of the charge and wherein said gasoline which is injected at level C represents 5 to 50% by volume of the charge.

5. A process according to claim 4, wherein said fluid represents 2 to.10% by volume and said gasoline represents 10 to 30% by volume of the charge.

6. A process according to claim 1, wherein the charge is injected into the reaction zone at a temperature generally ranging from 90 to 4000C, under a relative pressure from 0.7 to 3.5 bars, the temperature of the regenerated catalyst that arrives in this zone ranging f rom 600 to 9500 C.

7. A process according to claim 1 substantially as hereinbef ore described with reference to Figure 3 of the accompanying drawings.

Published 1989 at The Patent Office. State House, 6671 Mgh Holborn. London WC1R 4TP. Further copiesmaybe obtainedfrom The Patent Offtce. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87 1