Process for preparation of bi-functional fluid catalytic...

Details Process for preparation of bi-functional fluid catalytic... Process for preparation of bi-functional fluid catalytic...

2001-09-25

2003-09-02

Elve, M. Alexandra (Department: 1725)

Catalyst, solid sorbent, or support therefor: product or process

Zeolite or clay, including gallium analogs

And additional al or si containing component

C502S060000, C502S064000, C502S077000, C502S078000, C502S081000

Reexamination Certificate

active

06613710

ABSTRACT:

FIELD OF INVENTION
A process for the preparation of bi-functional catalyst for Fluid Catalytic Cracking (FCC) process that comprises molecular sieves, modified clay and semi-basic alumina. The catalyst is highly effective in the cracking of high boiling petroleum feedstock to provide simultaneously, enhanced yields of Liquefied Petroleum Gas (LPG) and reduction of undesirable bottoms.
BACKGROUND AND PRIOR ART REFERENCES
FCC catalyst additives are commonly used since late eighties to improve the profitability of refiners. They are, additive for improving LPG and octane number, SO
x
additive for reduction of sulphur emission, CO-Promoter additive for containment of CO emission and Bottom cracking additives for reducing bottoms.
LPG enhancing additive plays an important role in boosting LPG and/or to improve the octane number of gasoline. It has been used commercially for almost a decade, and is now a well accepted way to increase C
3
and C
4
olefin yields and gasoline octane.
ZSM-5 zeolite forms the most active component of these additives. Quite a lot of work has been done on making zeolites, such as ZSM-5, with different materials, ranging from all silica to materials containing silica and some other tetravalent metal such as boron, iron, gallium, etc. In lieu of, or in addition to, being incorporated into the zeolite framework, these and other catalytically active elements can also be deposited upon the zeolite by any suitable procedure, e.g., impregnation.
In spite of the tremendous benefits arising out of using ZSM-5 based compositions for enhancing LPG certain gap areas still remain un-addressed. The main drawbacks of these compositions are that, higher LPG yield is attained at a cost. ZSM-5 additives generally dilute the host catalyst inventory and there by catalyst activity decreases necessitating higher catalyst charge. The bottom yield either remains same or increases. Presently there is no catalyst in the market, which at one go satisfies the two needs of refiners, i.e. enhancement of LPG and reduction of bottoms.
In order to formulate ZSM-5 based additives the catalyst researchers confront the task of making aqueous slurries using hydrophobic zeolite and other ingredients. The issue of producing attrition resistant low cost additives is bothering manufacturers worldwide. The other issue is the production of cost effective additives. ZSM-5 zeolite is an expensive chemical; its manufacturing process is very time consuming, capital intensive and complex. Hence there is always a demand to formulate ZSM-5 based additives using lower quantities of zeolite without compromising on LPG yield. The other additive which off late has been widely used by the refiners is bottom cracking additive. This additive is used to reduce the yield of undesirable bottom products of FCC cracker.
Number of refiners today face the challenge to produce more LPG and reduced bottom. Hence it is a long imperative to develop such a product, which will meet both these requirements without affecting the general yield pattern.
There is thus an urgent requirement of an catalyst formulation which when used as FCC additive will be bi-functional, i.e. besides meeting the first requirement of LPG enhancement it must reduce the undesirable CLO or slurry oil.
Considerable work has been done on formulating and optimizing catalyst compositions containing ZSM-5 zeolite as the main and active ingredient. It will be briefly reviewed.
U.S. Pat. No. 4,826,793, incorporated by reference, teaches ZSM-5 additives for FCC use with 20, 40 or 60 wt % ZSM-5 in an attrition resistant matrix. ZSM-5 may be stabilized with phosphorous or be in a phosphorous containing matrix. The technique employed was to prepare at lower pH, clay phosphate slurry, raise its pH by adding phosphorus-containing salts before addition of zeolites. This invention raised an issue that remains un-addressed in the patent domain, i.e. addition of zeolite to a low pH matrix without destruction of zeolite. On the other hand increasing pH by addition of phosphorus containing salts has some negative effects on binding strength of the final composite due to dilution effect. A gap in our understanding thus remains which the present invention is trying to bridge.
Phosphorous stabilization is well known in the art, and more details of the technique are given in the following patents. U.S. Pat. No. 3,911,041, which is incorporated by reference, teaches conversion of methanol and ethers over phosphorous stabilized zeolites. U.S. Pat. No. 3,972,832, which is incorporated by reference, teaches and claims a composition of matter of a phosphorus containing, shape selective zeolite having at least 0.78 wt % phosphorus incorporated with the crystal structure. U.S. Pat. No. 4,044,065, claims conversion of aliphatics over phosphorus containing shape selective zeolites. U.S. Pat. Nos. 4,356,338 and 4,423,266 teach decreasing catalyst coking, and extending catalyst life, by pretreatment of the catalyst with steam and/or a phosphorus-containing compound. P-ZSM-5/Al
2
O
3
has a much-reduced coking rate, as compared to H-ZSM-5/Al
2
O
3
. U.S. Pat. No. 4,590,321, which is incorporated by reference, claims conversion of feeds comprising C
2
to C
12
alkanes or alkenes at 200 to 700° C. over a phosphorus stabilized zeolite made by impregnating with phosphate ions, then calcining to convert phosphate ions to an oxide of phosphorus. U.S. Pat. No. 5,194,412 provides improved catalytic compositions that include a zeolite and aluminum phosphate. U.S. Pat. No. 3,354,096 describes zeolite containing adsorbent and catalyst compositions that contain a phosphate-binding agent to improve physical strength. U.S. Pat. No. 3,649,523 describes hydrocracking catalysts which comprise a zeolite and an aluminum phosphate gel matrix. U.S. Pat. Nos. 4,454,241, 4,465,780, 4,498,975 and 4,504,382 describe zeolite catalysts that are prepared from clay which are further modified by the addition of a phosphate compound to enhance catalytic activity. U.S. Pat. Nos. 4,567,152, 4,584,091, 4,629,717 and 4,692,236 describe zeolite containing catalytic cracking catalysts that include phosphorus-containing alumina. U.S. Pat. Nos. 4,605,637, 4,578,371, 4,724,066 and 4,839,319 describe phosphorus and aluminum phosphate modified zeolites such as ZSM-5, Beta and ultrastable Y that are used in the preparation of catalytic compositions, including catalytic cracking catalysts. U.S. Pat. No. 4,765,884 and U.S. Pat. No. 4,873,211 describe the preparation of cracking catalysts which consist of a zeolite and a precipitated aluminum phosphate gel matrix. U.S. Pat. No. 5,521,133 relates to microspheres produced by spray drying clay slurries and calcining the product to form attrition-resistant microspheres. More particularly, this invention relates to the addition of phosphoric acid to clay in a novel manner, i.e., injecting the acid into dispersed kaolin slurry immediately before spray drying to improve properties of the microspheres. U.S. Pat. No. 5,190,902 utilizes the addition of phosphoric acid (or other phosphate compounds) with kaolin clay in a spray drying process to produce spray-dried microspheres, which are then calcined. In some formulation zeolite particles are present in the spray dryer feed. The process is carried out in one of two basic ways. In one, the slurry of clay particles is brought to a low pH, e.g., 1.0 to 3.0 before being mixed with a source of phosphorus, followed by spray drying. In the other, the clay slurry is brought to a high pH level (e.g., 10 to 14) before mixing with phosphate-containing compound. According to the teachings of this patent, use of these pH ranges is necessary for the production of particles with superior attrition resistance. Similarly, U.S. Pat. No. 5,231,064, and U.S. Pat. No. 5,348,643, both describe formation of a cracking catalyst by spray drying a slurry of zeolite with a slurry of clay treated with a phosphorus source at a pH less than 3. Sufficient water is added to bring the combined slurries to a low solids content of 25%. The use of aluminum phosphates as a

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