Highly active midbarrel hydrocracking catalyst and the...

Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component

Reexamination Certificate

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C502S060000, C502S064000, C502S067000, C502S074000, C502S079000

Reexamination Certificate

active

06670295

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a hydrocracking catalyst and its preparation process, especially a highly active midbarrel hydrocracking catalyst and its preparation process.
BACKGROUND
In recent years, the demand in both domestic and worldwide markets for high quality middle distillate products has been continuously increasing and the gap between supply and demand is getting greater and greater along with the development of the economy. The hydrocracking technology has become an optimum means for producing high quality clean middle distillates through deep processing of heavy oils due to its unique advantages.
At present, the activity of the midbarrel hydrocracking catalyst is not very high, and the solidifying point of the derived diesel with a wide distillation range is relatively high, so it is difficult to attain the objective of further increasing the output of the middle distillate oils by modifying the existing device or increasing the throughput.
The key to the increase in the output of the middle distillates in hydrocracking lies in the development and application of an adequate catalyst. The activity and selectivity to the middle distillates of a hydrocracking catalyst containing a single sort of zeolite can not be raised to a maximum extent due to the restriction of the sort of the zeolite, while the activity and selectivity to the middle distillates of a hydrocracking catalyst containing a composite of zeolites can be remarkably raised since the characteristics of various sorts of zeolites may be fully developed and synergetic catalysis may occur.
U.S. Pat. Nos. 5,536,687, 5,447,623 and 5,350,501 disclose a catalyst containing a zeolite-P and a zeolite-Y which is zeolite UHP-Y (LZ-10), which is prepared by (1) lowering the content of Na
2
O to 0.6-5.0 wt. % by partial NH
4
+
exchange of the zeolite-NaY, (2) lowering its unit cell size to 24.40-24.64 Å by steam calcination treatment, (3) lowering the content of Na
2
O to <0.5 wt. % by the second time NH
4
+
exchange, (4) lowering its unit cell size to 24.25-24.35 Å by steam calcination treatment again. The catalyst for producing middle distillates comprises zeolite-Y (1-15 wt. %), zeolite-&bgr; (1-15 wt. %), dispersed silica-alumina, alumina, metals W and Ni. Its activity and selectivity to middle distillates are not so high, so it is difficult to meet the need of producers for increasing the processing capacity of the device to further increase the output of middle distillates.
U.S. Pat. No. 5,279,726 discloses a hydrocracking catalyst containing a zeolite-&bgr; and the use thereof, which catalyst contains a zeolite-&bgr; and a zeolite-Y which is a ultra-stable zeolite-Y (LZY-82, LZY-84) with a unit cell size of 24.52-24.59 Å. The catalyst for producing middle distillates contains zeolite-Y and zeolite-&bgr; of 2.5-15 wt. % respectively. The zeolite-Y of the catalyst has a large unit cell size and strong acidity, which is unfavorable to the increase in the selectivity of the catalyst to middle distillates.
U.S. Pat. No. 5,160,033 discloses a hydrocracking catalyst for improving the octane number of gasoline and a process for the preparation thereof, which catalyst takes a zeolite-Y and a zeolite-&bgr; as the acidic components and is mainly used in the isomerization of alkanes. The zeolite-&bgr; is calcined to weaken its acidity, and the zeolite-Y is a ultra-stable zeolite Y-85 with a silica to alumina ratio of 6.5-20 and a unit cell size of 24.34-24.58 Å. The catalyst contains 10-30% of zeolite-&bgr; based on the total amount of the zeolites. This catalyst is mainly used in the isomerization of alkanes in gasoline.
U.S. Pat. No. 5,464,527 discloses a hydrocracking catalyst for raising the selectivity to middle distillates (turbine fuel+diesel), which catalyst uses a ultrahydrophobic zeolite-Y exchanged with rare earth (LZ-10) and dispersed silica-alumina as cracking components, and the metals W and Ni as hydrogenation metal components. This catalyst has a high selectivity to middle distillates, but its reaction temperature is still high.
THE DISCLOSURE OF THE INVENTION
The object of the present invention is to overcome the drawbacks of the prior catalysts and to develop a hydrocracking catalyst with a high activity and high yield to middle distillates.
The inventors have now surprisingly discovered a hydrocracking catalyst which has an activity higher than those of the prior midbarrel catalysts, and a remarkably increased selectivity to middle distillates. The solidifying point of the produced diesel distillate is lowered. This catalyst can meet the need of the refineries for increasing the throughput and further increasing the output of the middle distillates.
The hydrocracking catalyst of present invention comprises zeolites, amorphous silica-alumina and alumina as a support, Group VIII metal(s) and/or Group VIB metal(s) as active components; and comprises, on the basis of the catalyst weight, 4%-28%, preferably 4%-25% of a modified zeolite-Y and 4%-28%, preferably 4%-18% of a modified zeolite-&bgr;, wherein said zeolite-Y has a relative crystallinity of higher than 95%, preferably 100%-105%; a silica/alumina molar ratio of 9.0-30.6, preferably 10-20; an infrared acid of 0.30-0.90 mmol/g with more than 95% of Bronsted acid; an unit cell size of 24.25×10
−10
m-24.45×10
−10
m; a Na
2
O weight content of less than 0.16%, preferably less than 0.1%. Said modified zeolite-&bgr; has a silica/alumina molar ratio of 85-153, preferably 102-136; a Na
2
O weight content of less than 0.15%, preferably less than 0.1%; a relative crystallinity of 100-110% and an infrared acid of 0.1-0.4 mmol/g, preferably 0.2-0.3 mmol/g.
Said zeolite-Y preferably has a specific surface area of 680-850 m
2
/g, and a pore volume of 0.30-0.55 ml/g; said modified zeolite-p preferably has a specific surface area of 400-750 m
2
/g, more preferably 500-600 m
2
/g, and a pore volume of 0.25-0.50 ml/g, preferably 0.3-0.4 ml/g.
Said catalyst generally comprises amorphous silica-alumina of 0-32%, preferably 10%-28%; macroporous alumina of 0-32%, preferably 7%-28%; microporous alumina of 12-18%, preferably 13%-16%; Group VIB metal(s) of 15%-30%, preferably 18%-27%; Group VIII metal(s) of 3%-8%, preferably 4%-7%.
The aforesaid modified zeolite-Y may be derived by modification of zeolite-SSY. Particularly, said modified zeolite-Y may be prepared by calcining the zeolite-SSY in the presence of steam at a temperature of 500° C.-750° C., preferably 550° C.-650° C. under a vapor pressure of 0.01-0.30 MPa, preferably 0.05-0.20 MPa for 0.5-4 hours, preferably 1-2 hours.
Said zeolite-SSY may be prepared by
(1) mixing a starting material of zeolite-Y (i.e., zeolite NH
4
NaY or NaY) with water to form a slurry of the zeolite, the concentration of which is that per 100 ml slurry contains 5-30 g, preferably 10-25 g of the starting material of zeolite-Y;
(2) heating the mixture of step (1) to a temperature of 50-120° C., preferably 70-100° C.;
(3) adding thereto the crystal ammonium hexafluorosilicate or a solution thereof, and reacting with stirring the mixture for 0.1-24 hours, preferably 0.5-5 hours; and
(4) separating the product, which is then filtered, washed with water, and dried to obtain said zeolite-SSY; wherein
in step (1) the starting material of zeolite-Y is preferably zeolite NH
4
NaY with its Na
2
O content of less than 5.0% by weight, and its silica/alumina molar ratio of 3.5-7.0, preferably 4.5-7.0; and
in step (3) the amount of the added ammonium hexafluorosilicate is at least 10 g, preferably 20-50 g relative to per 100 g starting material of zeolite-Y; and the addition rate is up to 30 g, preferably 5-25 g per hour relative to 100 g of the starting material of zeolite-Y.
The zeolite-SSY with low Na
2
O content and high crystallinity is obtained directly by the above process.
The aforesaid modified zeolite-p may be a new one derived by the following highly efficient synthesis process, which comprises the steps that
(1) a slurry of a completely crystallized zeolite

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