Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Reexamination Certificate
2000-11-17
2003-05-20
Dunn, Tom (Department: 1725)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
C502S064000, C502S068000, C502S071000, C502S077000, C502S079000, C502S214000
Reexamination Certificate
active
06566293
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a catalyst composition for FCC which has high efficiency in the production of C
3
and C
5
olefins, i.e. light olefins.
2. Prior Art
In FCC practice, there are two ways to increase light olefin selectivity. The first of these is to increase the reaction temperature. This will increase the contribution of thermal cracking, which leads to increased formation of lighter products. For instance, in the so-called DCC (Deep Catalytic Cracking) process, a specific type of FCC process, higher temperatures and increased amounts of steam are used. However, thermal cracking is not very selective and produces large amounts of products of relatively little value, such as hydrogen, methane, ethane, and ethylene, in the “wet gas” (which contains H
2
and C
1
-C
4
products). Wet gas compression often limits refinery operation.
The second method is to add an olefin-selective, zeolite-containing additive such as a ZSM-5-containing additive. Conventional additives usually contain phosphorus-activated ZSM-5, which selectively converts primary cracking products (e.g., gasoline olefins) to C
3
and C
4
olefins. Improvement of the activity or the selectivity with phosphorus is known to increase the effectiveness of ZSM-5. For instance, EP-A- 511 013 describes the treatment of ZSM-5 with phosphorus to increase the propylene selectivity. Further, U.S. Pat. No. 5,472,594 describes a process for converting a hydrocarbon feed to a product containing improved yields of C
4
/C
5
olefins with a catalyst composition containing zeolite Y and an additive comprising a phosphorus-containing medium pore zeolite such as ZSM-5. Also Mobil's WO 98/41595 describes a process for the catalytic cracking of a hydrocarbon feedstock to produce an enhanced yield of C
3
to C
5
olefins using a catalyst composition comprising a large pore molecular sieve such as zeolite Y and an additive comprising a phosphorus-containing ZSM-5 blended in with the base catalyst containing zeolite Y. The same is described in U.S. Pat. No. 5,456,821. WO 94/13754 describes the same process using a catalyst composition containing a large pore molecular sieve and an additive containing a specific ZSM-5 which optionally contains 1.5 to 5.5 wt % elemental phosphorus. Also U.S. Pat. No. 5,521,133 describes the preparation of a ZSM-5 additive by injecting a ZSM-5 and kaolin slurry with phosphoric acid prior to spray-drying.
Additives, however, dilute the catalyst inventory and will decrease bottoms conversion. In the past, it was tried to incorporate phosphorus-activated ZSM-5 as a component into FCC catalyst compositions. In U.S. Pat. No. 5,110,776 a phosphorus treatment was used to improve the attrition resistance of catalyst compositions. Here a Y zeolite is treated with a phosphorus-containing aqueous solution, and said treated zeolite is directly combined with a matrix precursor to form a slurry. Said slurry is spray-dried. The matrix precursor used comprises up to 3.4 wt % alumina, about 25 wt % clay, and about 45 wt % silica. Although. it is mentioned that ZSM-5 may be used, all of the examples are directed to the use of zeolite Y. The above-described U.S. Pat. No. 5,472,594 mentions mixing of the phosphorus-activated ZSM-5 with a matrix and Y zeolite and spray-drying to form an FCC catalyst, but gives no indication of how this can be done, nor of the type of matrix to be used. The examples only describe ZSM-5 additives which are mechanically mixed with base catalysts. Mobil's U.S. Pat. Nos. 5,126,298 and 5,231,064 describe the preparation of a catalyst composition by providing a zeolite slurry and two types of clay slurries, treating at least one of these slurries with a source of phosphorus, combining the slurries, and spray-drying at a pH of below 3. The catalyst matrix described here does not contain any added silica and/or alumina. As will be explained below, phosphorus-activated olefin-selective zeolites such as ZSM-5 can only be incorporated into a catalyst composition as a component when specific measures are taken.
Conventional FCC catalyst compositions which are also suitable for bottoms cracking contain a catalytic cracking component and amorphous alumina. Catalytic cracking components are either crystalline, such as zeolite Y and zeolite X, or amorphous, such as silica-alumina. Amorphous alumina is necessary to provide the bottoms conversion. Amorphous alumina may also be used as a binder to provide the matrix with enough binding function to properly bind the crystalline cracking component when present. Thus, said amorphous alumina is either present in the matrix, i.e. an active matrix is used, or in the amorphous cracking component in the form of silica-alumina. In other words, a catalyst composition with good bottoms conversion contains at least 10 wt % amorphous alumina. By the term amorphous alumina is meant an alumina which comprises bottoms cracking activity. This means that some crystallinity may be present. It was found that when the phosphorus compound used for activation of the olefin-selective zeolite is added to the catalyst, strike, i.e. the spray-drying slurry containing the matrix components and the catalytic cracking component, it interferes with the amorphous alumina present in the strike. As a result, at present no catalyst compositions are on the market which effectively combine olefin-selective zeolites with high amounts of alumina either in the matrix or in the amorphous cracking component. The object of the present invention is to provide a catalyst composition, with a high light olefin selectivity while maintaining the bottoms conversion.
SUMMARY OF THE INVENTION
In one embodiment, the present invention is directed to a process for the preparation of a catalyst composition comprising the following steps:
a) ex situ activating an olefin-selective zeolite with at least 10 wt % of a phosphorus-containing compound, calculated as P
2
O
5
based on the total amount of olefin-selective zeolite,
b) combining the activated olefin-selective zeolite with 10-40 wt % catalytic cracking component, binder, and 0-25 wt % silica in a slurry so that the total amount of amorphous alumina in the final catalyst composition is at least 10 wt %, and
spray-drying the slurry to form catalyst particles.
In a second embodiment, the present invention comprises a catalyst composition comprising:
a) 10 to 40 wt % catalytic cracking component,
b) 0.1 to 85 wt % ex situ phosphorus-treated olefin-selective zeolite, wherein the olefin-selective zeolite is treated with at least 10 wt % phosphorus-containing compound, calculated as P
2
O
5
based on the total amount of olefin-selective zeolite,
c) binder,
d) 0-25 wt % silica,
wherein the total amount of amorphous alumina in the final catalyst composition is at least 10 wt %.
Other embodiments of the invention encompass details about process steps and conditions and catalyst compositions, all of which are hereinafter disclosed in the following discussion of each of the facets of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the process of the present invention, the olefin-selective zeolite is activated ex situ, before it is added to a conventional FCC catalyst formulation. Ex situ activation of olefin-selective zeolite is achieved by treating the zeolite with a phosphate source, followed by drying and calcination. Subsequently, the activated olefin-selective zeolite is added to the catalyst matrix. It was found that the ex situ activation of olefin-selective zeolite immobilizes the phosphate enough to avoid its interference with the catalyst matrix or catalytic cracking component after addition thereto. This allows the olefin-selective zeolite to exert its selective cracking on the primary products, while not diluting the inventory. Thus, the refiner can actually lower the riser top temperature, which will allow a lower “wet gas” make, while also the contribution of the Y-zeolite to the C
3
- and C
4
-selectivity will be lowered. At the same time, the bottoms conversation wi
O'Connor Paul
Quinones Augusto R.
Vogt Eelco Titus Carel
Akzo Nobel N.V.
Dunn Tom
Ildebrando Christina
Morris Louis A.
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