Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And group viii containing
Reexamination Certificate
1998-12-30
2002-03-26
Langel, Wayne (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And group viii containing
C502S066000, C502S075000, C502S079000
Reexamination Certificate
active
06362123
ABSTRACT:
BACKGROUND
The present invention relates to novel hydrocracking catalysts. More particularly, the invention relates to noble metal containing low acidic hydrocracking catalysts.
Hydrocracking utilizing a zeolite catalyst is widely used in petroleum refining for converting various petroleum fractions to lighter and more valuable products, especially gasoline and distillates such as jet fuels, diesel fuels and heating oils.
Known hydrocracking catalysts comprise an acid cracking component and a hydrogenation component. The acid component can be an amorphous material such as an acidic clay or amorphous silica-alumina or, alternatively, a zeolite. Large pore zeolites such as zeolites X and Y possessing relatively low silica:alumina ratios, e.g., less than about 40:1, have been conventionally used for this purpose because the principal components of the feedstocks (gas oils, coker bottoms, reduced crudes, recycle oils, FCC bottoms) are higher molecular weight hydrocarbons which will not enter the internal pore structure of the smaller pore zeolites and therefore will not undergo conversion. The hydrogenation component may be a noble metal such as platinum or palladium or a non-noble metal such as nickel, molybdenum or tungsten or a combination of these metals.
A measurement of acidity provides an indication of the amount of framework aluminum in a zeolite. The reduction of acidity indicates that a portion of framework alumina is being lost. Thus, a higher silica to alumina ratio will correspond to a lower acidity. Although the silica to alumina ratio is most often used to refer to the cracking activity of a catalyst, alpha acidity is a more accurate measurement of such activity.
Distillate selective hydrocracking catalysts which rely upon the acidic components of the zeolite for hydrocracking activity cause a significant amount of unwanted secondary cracking of paraffins along with the desired cracking of aromatic and naphthenic components. This secondary cracking results in distillate yield loss.
There is, therefore, a need for a distillate selective hydrocracking catalyst with very low acidity, i.e. a hydrocracking catalyst which does not rely upon acidity of the zeolite for its hydrocracking activity. It has been found that such a catalyst is useful in various hydrocracking processes, such as a process for increasing diesel fuel cetane levels described in co-pending application 09/330,386, filed concurrently herewith.
SUMMARY OF INVENTION
The present invention is a hydrocracking catalyst composition that includes a large pore crystalline molecular sieve material component having a faujasite structure and an alpha acidity of less than 1, and a Group VIII noble metal component. Preferred crystalline sieve materials are zeolite Y and zeolite USY. In the preferred embodiment, the crystalline sieve material has an alpha acidity of about 0.3 or less. The Group VIII noble metal component can be platinum, palladium, iridium, rhodium, or a combination of one or more of these noble metals. Platinum is preferred. The content of the Group VIII noble metal component can vary between about 0.01 and about 5 wt % of the catalyst.
The Group VIII noble metal component is located within the catalyst in dispersed clusters. In the preferred embodiment, the particle size of the Group VIII metal on the catalyst is less than about 10 Å. Dispersion of the metal can also be measured by hydrogen chemisorption technique in terms of the H/metal ratio. In the preferred embodiment, when platinum is used as the noble metal component, the H/Pt ratio between about 1.1 and 1.5.
In a preferred embodiment, the catalyst is prepared by a method which includes: (a) replacing hydrogen on hydroxyl nest groups located within said crystalline molecular sieve material component with said Group VIII noble metal component by impregnation or cation exchange in a basic solution; (b) drying said catalyst to remove said basic solution; and (c) calcining said catalyst. Preferably, the basic solution has a pH of from about 7.5 to about 10.0.
The catalysts of the present invention have a low acidity that provides selective hydrocracking of the aromatics and naphthenes in a feedstock, while limiting the cracking of paraffins. The catalysts produce improved yields of distillate products, such as diesel fuel, at high conversion rates.
DETAILED DESCRIPTION OF INVENTION
The catalysts of the present invention include a large pore crystalline molecular sieve material component with a faujasite structure having an alpha acidity of less than 1 and, preferably, about 0.3 or less. The catalysts also contain a Group VIII noble metal component.
Unlike catalysts known in the art, the catalysts of the present invention do not rely on acidity to drive the hydrocracking reactions. Hydrocracking is driven by the Group VIII noble metal component, which acts as a hydrogenation and hydrocracking component. The crystalline molecular sieve material acts as a host for the Group VIII noble metal component. The low acidity permits the hydrocracking of the aromatics and naphthenic species, but minimizes secondary cracking of paraffins. Also, the faujasitic crystalline molecular sieve material provides reactant selectivity for adsorbing aromatic and naphthenic hydrocarbon structures, as opposed to paraffins. The preference of the catalyst for ringed structures allows the paraffins to pass through with minimal hydrocracking or hydroisomerization, thereby retaining a high distillate yield.
Constraint Index is a convenient measure of the extent to which a crystalline sieve material allows molecules of varying sizes access to its internal structure. Materials which provide highly restricted access to their internal structures have a high Constraint Index value and small pore size, e.g. less than 5 angstroms. On the other hand, materials which provide relatively free access to their internal porous crystalline sieve structure have a low Constraint Index value, and usually pores of large size, e.g. greater than 7 angstroms. The method by which Constraint Index is determined is described fully in U.S. Pat. No. 4,016,218, incorporated herein by reference.
Large pore crystalline sieve materials are typically defined as having a Constraint Index of 2 or less. Crystalline sieve materials having a Constraint Index of 2-12 are generally regarded to be medium pore materials.
The Constraint Index (CI) is calculated as follows:
Constraint
Index
=
log
10
(
fraction
of
n
-
hexane
remaining
)
log
10
(
fraction
of
3
-
methylpentane
remaining
)
(
1
)
The Constraint Index approximates the ratio of the cracking rate constants for the two hydrocarbons.
TABLE 1
Constraint Index (CI) values for some typical materials
CONSTRAINT
Material
INDEX (CI)
Test Temperature
ZSM-4
0.5
316° C.
ZSM-5
6-8.3
371° C.-316° C.
ZSM-11
5-8.7
371° C.-316° C.
ZSM-12
2.3
316° C.
ZSM-20
0.5
371° C.
ZSM-22
7.3
427° C.
ZSM-23
9.1
427° C.
ZSM-34
50
371° C.
ZSM-35
4.5
454° C.
ZSM-38
2
510° C.
ZSM-48
3.5
538° C.
ZSM-50
2.1
427° C.
TMA Offretite
3.7
316° C.
TEA Mordenite
0.4
316° C.
Clinoptilolite
3.4
510° C.
Mordenite
0.5
316° C.
REY
0.4
316° C.
Amorphous Silica-alumina
0.6
538° C.
Dealuminized Y (Deal Y)
0.5
510° C.
Erionite
38
316° C.
Zeolite Beta
0.6-2.0
316° C.-399° C.
The catalysts of the invention contain a large pore crystalline sieve material component with a Constraint Index of less than 2. The materials have a pore size sufficiently large to admit most of the components normally found in a feedstock and generally have a pore size greater than 7 Angstroms. These materials can include zeolites, such as Zeolite beta, Zeolite Y, Ultrastable Y (USY), Dealuminized Y (DEALY), Mordenite, ZSM-3, ZSM-4, ZSM-18 and ZSM-20.
The large pore crystalline sieve materials useful for the catalysts of the invention are of the faujasite family. Within the ranges specified above, preferred crystalline sieve materials useful for
Angevine Philip J.
Huang Tracy J.
Tsao Ying-Yen P.
Hantman Ronald D.
Langel Wayne
Mobil Oil Corporation
Nguyen Cam N.
LandOfFree
Noble metal containing low acidic hydrocracking catalysts does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Noble metal containing low acidic hydrocracking catalysts, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Noble metal containing low acidic hydrocracking catalysts will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2821250