Midbarrel hydrocracking catalyst and preparation thereof

A midbarrel hydrocracking catalyst includes the following: PA1 a. 10-75% by weight of a Y-type molecular sieve; PA1 b. 10-25% by weight of a small pore alumina; PA1 c. 0-40% by weight of an amorphous aluminosilicate; PA1 d. 0-25 % by weight of a large pore alumina; PA1 e. 12-32% by weight of a Group VIB metal oxide, and PA1 f. 3-8% by weight of a Group VIII metal oxide. The Y-type molecular sieve is a high silica Y-type molecular sieve USSSY of a Na.sub.2 O content of no more than 0.2% by weight, a SiO.sub.2 to AJ.sub.2 O.sub.3 molar ratio of 6-40, a relative crystallinity of more than 80% and a unit cell size of 2.426-2.44 nm.

FIELD OF THE INVENTION 
The present invention relates to a midbarrel hydrocracking catalyst, more 
particularly, to a hydrocracking catalyst of improved activity, 
selectivity and stability for producing middle distillates from vacuum gas 
oil and the like, especially of improved resistance to nitrogenous matter 
present in the feed material. 
BACKGROUND OF THE INVENTION 
Petroleum refiners usually employ hydrocracking process to produce 
desirable products such as turbine fuel, diesel fuel and other middle 
distillate products in the presence of a suitable hydrocracking catalyst. 
In recent years, since the vacuum gas oil becomes heavier in density and 
worse in quality, the hydrocracking catalysts are required to possess high 
activity, selectivity and stability for producing middle distillates from 
vacuum gas oil and the like, and especially to possess high resistance to 
various catalytic poison, in particular nitrogenous matter present in the 
feed material. Unfortunately, the prior art hydrocracking catalysts are 
suitable for processing a feed material with a nitrogenous matter level of 
no more than 10.times.10.sup.-4 % by weight (calculated as nitrogen), and 
when the nitrogen level of the feed material increases, the hydrocracking 
catalyst deactivates rapidly, in order to keep the productivity of the 
hydrocracking process constant, the operation temperature should be 
increased, which incurs more operation expense. 
Each of U.S. Pat. Nos. 4,517,033, 4,517,074, 4,563,434, 4,576,711, 
4,664,776, 4,672,048 and 4,762,813 disclosed a midbarrel hydrocracking 
catalyst, which comprises a molecular sieve, an amorphous aluminosilicate, 
an alumina and hydrogenation metal components, wherein said molecular 
sieve is LZ-10,LZ-210, modified LZ-210 or USY. Of the molecular sieves, 
LZ-10 is obtained by further hydrothermally treating USY, and LZ-210 is 
prepared by treating NH.sub.4 NaY molecular sieve with ammonium 
fluorosilicate in the presence of a buffer solution. However, when LZ-10 
is used to prepare a midbarrel hydrocracking catalyst, the result catalyst 
achieves good selectivity to middle distillates but relatively low 
activity; while when LZ-210, modified LZ-210 or USY is used, the resulting 
catalyst possesses high activity but low selectivity to middle 
distillates. 
It is known that the resistance of the hydrocracking catalyst containing a 
molecular sieve to nitrogenous matter can be improved by strengthening the 
resistance of said molecular sieve to nitrogenous matter. A known 
effective technique to strengthen the resistance of a molecular sieve to 
nitrogenous matter is treating NH.sub.4 NaY molecular sieve with 
fluorosilicate salts or fluorosilic acid in the presence of a buffer 
solution, but such a treating process provides molecular sieve with 
relatively low activity and resistance to nitrogenous matter. 
SUMMARY OF THE INVENTION 
Accordingly, an object of the invention is to provide a hydrocracking 
catalyst of improved activity, selectivity and stability for producing 
middle distillates from vacuum gas oil and the like, especially of 
improved resistance to nitrogenous matter, the catalyst of the present 
invention comprises: 
10-75% by weight of a Y-type molecular sieve; 
10-25% by weight of a small pore alumina; 
0-40% by weight of an amorphous aluminosilicate; 
0-35% by weight of a large pore alumina; 
12-32% by weight of a Group VIB metal oxide; and 
3-8% by weight of a Group VIII metal oxide; 
wherein the Y-type molecular sieve is a high silica Y-type molecular sieve 
of a Na.sub.2 O content of no more than 0.2% by weight, a SiO.sub.2 to 
Al.sub.2 O.sub.3 molar ratio of 6-40, a relative crystallinity of more 
than 80% and a unit cell size of 2.426-2.444 nm, designated as USSSY. 
Another object of the present invention is to provide a process for 
preparing a high silica Y-type molecular sieve USSSY of a Na.sub.2 O 
content of no more than 0.2% by weight, a SiO.sub.2 to Al.sub.2 O.sub.3 
molar ratio of 6-40, a relative crystallinity of more than 80% and a unit 
cell size of 2.426-2.444 nm, said process comprises treating a low sodium 
and high silica Y molecular sieve of a Na.sub.2 O content of no more than 
0.2% by weight, a SiO.sub.2 to Al.sub.2 O.sub.3 molar ratio of 6-40, a 
relative crystallinity of more than 95% and a unit cell size of 
2.444-2.455 nm at 500-700.degree. C. under a steam pressure of 0.05-0.2 
MPa for 0.5-2 hours. 
A still another object of the present invention is to provide a preparation 
process for a hydrocracking catalyst of improved activity, selectivity and 
stability for producing middle distillates from vacuum gas oil and the 
like, the process of the present invention comprises: 
adding dilute nitric acid to a small pore alumina and comulling to form an 
adhesive; and 
mixing a USSSY, an adhesive, a Group VIB element salt or oxide and/or a 
Group VIII element salt or oxide, and optionally a large pore alumina and 
an amorphous aluminosilicate, and kneading, then drying at 100.degree. 
C.-150.degree. C. for 3-6 hours, finally calcining at 450-650.degree. C. 
for 3-6 hours to give a catalyst; or 
mixing a USSSY, an adhesive, and optionally a large pore alumina and an 
amorphous aluminosilicate, kneading, drying at 100-150.degree. C. for 3-5 
hours, calcining at 450-650.degree. C. for 3-5 hours to give a support, 
impregnating said support with an aqueous solution containing a Group VIB 
element and/or a Group VIII element, then drying at 100-150.degree. C. for 
3-6 hours and finally calcining at 450-650.degree. C. for 3-6 hours to 
give a catalyst. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The inventors carried out extensive investigation on catalyst systems 
applied in the hydrocracking process and found that a high silica Y-type 
molecular sieve of a Na.sub.2 O content of no more than 0.2% by weight, a 
SiO.sub.2 to Al.sub.2 O.sub.3 molar ratio of 6-40, a relative 
crystallinity of more than 80% and a unit cell size of 2.426-2.444 nm 
possesses improved activity, selectivity and superior resistance to 
nitrogenous matter under hydrocracking process conditions, and that when 
such a molecular sieve is used to prepare a hydrocracking catalyst, the 
resulting catalyst achieves unexpectedly improved activity and selectivity 
for producing middle distillates from vacuum gas oil and the like, in 
addition to improved resistance to nitrogenous matter present in the feed 
material. 
The hydrocracking catalyst of the present invention comprises a Y-type 
molecular sieve, a small pore alumina, a Group VIB element oxide and/or a 
Group VIII element oxide, and optionally an amorphous aluminosilicate and 
a large pore alumina. 
The Y-type molecular sieve used in the present invention is a high silica 
Y-type molecular sieve of a Na.sub.2 O content of no more than 0.2% by 
weight, a SiO.sub.2 to Al.sub.2 O.sub.3 molar ratio of 6-40, a relative 
crystallinity of more than 80% and a unit cell size of 2.426-2.444 nm, and 
is designated as a molecular sieve USSSY. Such a USSSY is included in the 
present catalyst at a level of 10-75% by weight. 
The USSSY can be preferably prepared from a Y molecular sieve of a Na.sub.2 
O content of no more than 0.2% by weight, a SiO.sub.2 to Al.sub.2 O.sub.3 
molar ratio of 6-40, a relative crystallinity of more than 95% and a unit 
cell size of 2.444-2.455 nm, by hydrothermally treating said Y molecular 
sieve at 500-700.degree. C. under a steam pressure of 0.05-0.2 MPa for 
0.5-2 hours. Said Y molecular sieve is one preferably prepared by treating 
a NaY and/or NH.sub.4 NaY in the absence of any pH regulating agent, 
detailed as in, for example, Chinese Patent Application No. CN90102645.X 
The process for preparing the low-sodium-high-silica Y-type molecular sieve 
is identical with that disclosed in CN90102645.X, and comprises the steps 
of: 
(1) mixing the raw material Y type molecular sieve (NH.sub.4 NaY or NaY) 
with water to give a slurry having a concentration of 5-30 g of the raw 
material Y type molecular sieve per 100 ml of the slurry and heating the 
slurry to a reaction temperature of 50-120.degree. C.; 
(2) allowing to react by adding generally at an adequately slow rate of 30 
g max., preferably 5-25 g, of crystalline ammonium hexafluorosilicate or 
equivalent aqueous solution thereof per 100 g Y type molecular sieve/hour. 
(3) continuously stirring the mixture within 0.1-24 hours after completion 
of the addition of ammonium hexafluorosilicate while maintaining the 
reaction temperature at 50-120.degree. C.; 
(4) separating the product from the reaction mixture; 
(5) washing with water, filtering and drying the isolated 
low-sodium-high-silica Y type molecular sieve and sodium ammonium 
fluoroaluminate crystal to give the end product. 
The small pore alumina used in the present invention, commercially 
available from, for example, No. 3 Refinery of Fushun, P.R. China, is of a 
pseudoboehmite phase. Its pore volume is 0.40-0.60ml/g, surface area 
180-340 m.sup.2 /g, alumina trihydrate content less than 3% by weight. 
Said small pore alumina is present in the present catalyst at a level of 
10-25% by weight. 
The amorphous aluminosilicate used herein is present in the catalyst at a 
level of 0-40% by weight. Its SiO.sub.2 content is 10-90% by weight, pore 
volume 0-56-1.08 ml/g, surface area 220-460 m.sup.2 /g. It can be prepared 
by conventional process, such as depositing SiO.sub.2 upon porous Al.sub.2 
O.sub.3 to give an amorphous aluminosilicate cogel or graft copolymer, or 
by depositing Al.sub.2 O.sub.3 upon porous SiO.sub.2 to give said cogel or 
graft copolymer according to U.S. Pat. No. 4,517,073. Such an amorphous 
aluminosilicate is also available from for example No. 3 refinery of 
Fushun, P.R. China. When there is no amorphous aluminosilicate present in 
the present catalyst, the catalyst will become more suitable for producing 
light oils, but still possess high resistance to nitrogenous matter. 
The large pore alumina used in the invention, commercially available from 
for example No. 3 Refmery of Fushun, P.R. China, possesses a pore volume 
of 0.8-1.1 ml/g, a surface area of 230-400m.sup.2 /g, an alumina 
trihydrate content of less than 2% by weight. Its content in the present 
catalyst is 0-35% by weight. 
The hydrogenation metals used in the present invention are a Group VIB 
element and/or a Group VIII element of the periodic table of elements, 
their contents in oxide form in the catalyst are 12-32% by weight and 3-8% 
by weight respectively. The Group VIB elements are preferably W and/or Mo, 
and the Group VIII elements are preferably Ni and/or Co, the metals can be 
used in combination or singly. 
To produce the present catalyst, one can first prepare an adhesive by 
comulling a mixture of a small pore alumina and a nitric acid solution, 
then mechanically mix the hydrogenation metal oxides and/or insoluble 
salts thereof, a molecular sieve, an adhesive, and optionally a large pore 
alumina and an amorphous aluminosilicate, or alternatively, impregnate a 
support prepared from a mixture of a molecular sieve, an adhesive, and 
optionally an amorphous aluminosilicate and a large pore alumina with a 
solution of soluble salts of said hydrogenation elements, and knead, then 
dry at 100-150.degree. C. for 3-6 hours and finally calcining at 
450-650.degree. C. for 3-6 hours to give the catalyst. Said support can be 
prepared by kneading said mixture, then drying at 100-150.degree. C. for 
3-5 hours, and finally calcining at 450-650.degree. C. for 3-5 hours. Said 
metal oxide can be, for example, MoO.sub.3, WO.sub.3, NiO, CoO and 
Co.sub.2 O.sub.3 etc., said insoluble salts can be, for example, 
NiCO.sub.3, CoCO.sub.3 etc. Said soluble salts can be, for example, 
Ni(NO.sub.3).sub.2, Co(NO.sub.3).sub.2, (NH.sub.4).sub.2 MoO.sub.4 and 
(NH.sub.4).sub.2 W.sub.4 O.sub.13. Soluble acid of th corresponding 
element can also be used. 
The present catalyst can be moulded into any form suitable for 
hydrocracking process before putting into use. The operation temperature 
for the catalyst is preferably 300-400.degree. C., the hydrogen partial 
pressure is preferably 5-20 MPa. 
By utilizing a USSSY, the molecular sieve of improved activity, selectivity 
and improved resistance to nitrogenous matter, the present catalyst can 
achieve improved activity, selectivity and stability for producing middle 
distillates from vacuum gas oil and the like, even at a nitrogenous matter 
level of up to 30.times.10.sup.-4 % by weight (calculated as nitrogen, and 
the same below) of a feed material.

The present invention will be described in more detail by way of the 
nonlimiting examples below. 
EXAMPLE 1 
A low sodium and high silica Y molecular sieve is prepared according to CN 
90102645.X. The said Y molecular sieve is treated at 600.degree. C. under 
a steam pressure of 0.1 MPa for 1 hour to give USSSY-1. 
EXAMPLE 2 
The Y molecular sieve prepared as in Example 1 is treated at 500.degree. C. 
under a steam pressure of 0.05 MPa for 1 hour to give USSSY-2. 
EXAMPLE 3 
The Y molecular sieve prepared as in Example 1 is treated at 550.degree. C. 
under a steam pressure of 0.2 MPa for 1 hour to give USSSY-3. 
The properties of USSSYs prepared in Example 1 to Example 3 are shown in 
Table 1. 
TABLE 1 
______________________________________ 
Properties of USSSYs 
USSSY-1 USSSY-2 USSSY-3 
______________________________________ 
molar ratio of SiO.sub.2 to Al.sub.2 O.sub.3 
10.01 10.05 9.99 
unit cell size, nm 2.440 2.438 2.439 
relative crystallinity, % 
99 110 103 
Na.sub.2 O content, % by weight 0.05 0.2 
______________________________________ 
0.05 
EXAMPLE 4 
440 ml of 0.2N HNO.sub.3 solution is added to 75.4 g of a small pore 
alumina Al.sub.2 O.sub.3 of a pore volume of 0.47 ml/g and a surface area 
of 280 m.sup.2 /g (available from No. 3 Refinery of Fushun, P.R. China). 
This mixture is mulled to give an is adhesive (the same in all examples.) 
180.5 g of USSSY-1, 100.8 g of H.sub.2 WO.sub.4, 82.8 g of 
Ni(NO.sub.3).sub.2.-6H.sub.2 O and the prepared adhesive are subjected to 
comulling in a grinder into a paste which is then extruded. The extrudate 
is allowed to dry, then further dried at 110.degree. C. for 3 hours, and 
finally calcined in the stream of air at 500.degree. C. for 5 hours to 
give Catalyst A. 
EXAMPLE 5 
80.8 g of USSSY-2, 40.7 g of an amorphous aluminasilicate of a pore volume 
of 0.64 m.sup.1 /g and a surface area of 310 m.sup.2 /g, 40.7 g of large 
pore Al.sub.2 O.sub.3 of a surface area of 350 m.sup.2 /g and a pore 
volume of 0.90 ml/g (available from No. 3 Refinery of Fushun) and 105.5 g 
of adhesive prepared as in Example 4 are subjected to comulling in a 
grinder into a paste which is then extruded. After being dried, the 
extrudate are calcined at 600.degree. C. for 5 hours to give a carrier. 
The carrier obtained is impregnated with a mixture of an aqueous solution 
of ammonium metatungstate and nickelous nitrate, dried at 110.degree. C. 
for 3 hours and finally calcined at 500.degree. C. for 4.5 hours to give 
Catalyst B. 
EXAMPLE 6 
A mixture of 40.9 g of USSSY-3, 88.2 g of large poreAl.sub.2 O.sub.3 of a 
pore volume of 0.90 ml/g and a surface area of 350 m.sup.2 /g, 105.0 g of 
H.sub.2 WO.sub.4, 88.2 g of Ni(NO.sub.3).sub.2 -6H.sub.2 O and 220.5 
adhesive prepared as in Example 4 is extruded, dried at 110.degree. C. for 
5 hours and finally calcined at 500.degree. C. for 6 hours to give 
Catalyst C. 
EXAMPLE 7 
A mixture of 80 g of USSSY-3, 19.2 g of a large pore Al.sub.2 O.sub.3, 48g 
of an amorphous aluminosilicate and 40g of adhesive prepared as in Example 
4 is extruded, dried at 110.degree. C. for 5 hours and calcined at 
650.degree. C. for 3 hours. The carrier thus obtained is impregnated with 
a mixture solution of ammonium metatungstate and nickelous nitrate which 
contains 54.07 g of WO.sub.3 /100 ml and 9.38 g of NiO/100 ml 
respectively, dried at 110.degree. C. for 6 hours and calcined at 
500.degree. C. for 6 hours to give Catalyst D. 
EXAMPLE 8 
Catalyst E is prepared in the same procedures as in Example 7 except that 
the large poreAl.sub.2 O.sub.3 is not used. 
Compositions of catalysts of Example 4 to Example 8 are as follows: 
TABLE 2 
______________________________________ 
Catalyst Compositions 
Catalyst A B C D E 
______________________________________ 
composition, % by weight 
48.8 28.6 13.0 40 40 
USSSY 
small pore Al.sub.2 O.sub.3 20.4 14.4 21.0 20 20 
large pore Al.sub.2 O.sub.3 -- 11.2 28.0 16 -- 
amorphous aluminosilicate -- 16.8 -- 24 40 
WO.sub.3 25.1 24.1 31.0 24.06 20.91 
NiO 5.6 4.9 7.0 3.62 7.23 
______________________________________ 
COMATIVE EXAMPLE 1 
A mixture of 15 g of MoO.sub.3, 20 g of Ni(NO.sub.3).sub.2 -6H.sub.2 O, 
59.9 g of a USY molecular sieve available from No. 3 Refinery of Fushun, 
P.R. China and 66.7 g of an adhesive prepared as in Example 4 is comulled 
in a grinder into a paste, which is then extruded, dried at 105.degree. C. 
for 3 hours and calcined at 500.degree. C. for 4 hours to give comparative 
Catalyst A'. 
COMATIVE EXAMPLE 2 
Comparative Catalyst B' is prepared according to the procedures as 
described in U.S. Pat. No. 3,897,327. 
COMATIVE EXAMPLE 3 
Comparative Catalyst C' is prepared according to the procedures as 
described in U.S. Pat. No. 4,664,776. 
Compositions of comparative catalysts are as follows: 
TABLE 3 
______________________________________ 
Compositions of Comparative Catalysts 
Catalyst A' B' C' 
______________________________________ 
composition, % by weight USSSY 
60 16 40 
small pore A1.sub.2 O.sub.3 20 20 20 
large pore A1.sub.2 O.sub.3 -- 36 16 
amorphous aluminosilicate -- 28 24 
WO.sub.3 15(Mo.sub.3) 20.87 23.0 
NiO 
5 6.0 3.5 
______________________________________ 
EXAMPLE 9 
Evaluation of Catalytic Activity 
Catalysts are evaluated by a single-stage once-through operation in a 200 
ml small scale reactor. Vacuum gas oil is pre-treated by hydrorefining to 
remove hetero-atoms, hydrogenate aromatics, and to keep nitrogen and 
sulphur at certain levels. The sulphur level is finally controlled at 
about 0.3% by weight (if necessary, CS.sub.2 can be injected) before 
contacting the catalyst. The properties of the pre-treated vacuum gas oil 
to be used as feed material are as follows: 
TABLE 4 
______________________________________ 
Properties of the Vacuum Gas Oil 
Pre-treated Vacuum Gas Oil NO. 
1 2 3 
______________________________________ 
density (D.sub.4.sup.20), g/cm.sup.3 
0.9176 0.8732 0.8792 
distillation range, .degree. C. 
initial point 262 272 280 
50% 427 425 391 
95% 512 502 457 
dry point 520 -- 470 
sulfur, 10.sup.-4 w % 34 41 34 
______________________________________ 
(1) Comparison between A and A' 
Activities of Catalyst A and A' are evaluated for comparison, using 
pre-treated vacuum gas oil 1 as feed material. Process conditions and 
results are as follows: 
TABLE 5 
______________________________________ 
Catalyst A A' 
______________________________________ 
reaction conditions 
H2 partial pressute, MPa 7.8 7.8 
hydrocracking temperature, .degree. C. 375 375 
volume space velocity, h.sup.-1 1.81 1.34 
H.sub.2 /oil ratio, v/v 1500:1 1500:1 
nitrogen level of feed material, 10.sup.-4 % by weight 25.8 3.8 
product distribution, % by weight 
C1-C4 -- 
5.9 
C5-65.degree. C. 3.2 4.5 
65-177.degree. C. 32.3 27.8 
177-340.degree. C. 35.8 33.4 
&gt;340.degree. C. 26.8 30.2 
&lt;340.degree. C. 71.3 65.7 
product properties 
65-177.degree. C. naphtha 
density(D.sub.4.sup.20), g/cm.sup.3 0.7570 0.7579 
aromatic potential content, % by weight 
65 52 
177-340.degree. C. diesel oil 
density(D.sub.4.sup.20), g/cm.sup.3 0.8249 0.8254 
hexadecane value 47.1 47.1 
solidification point, .degree. C. &lt;26 &lt;-30 
______________________________________ 
As shown in Table 5, Catalyst A of the invention possesses higher activity 
and resistance to nitrogen. Furthermore, less gas and a naphtha of higher 
aromatic potential are produced in the presence of Catalyst A of the 
invention. 
(2) Activity Evaluation for Catalyst A, B and C 
Catalysts A, B and C. are evaluated using pre-treated vacuum gas oil 2 as 
the feed material under the same operation conditions: hydrogen partial 
pressure, 14.7 MPa; H.sub.2 /oil ratio, 1500:1 (v/v); volume space 
velocity, 1.5h.sup.-1 ; nitrogen level, 18.times.10.sup.-4 % by weight. 
Results are as follows: 
TABLE 6 
______________________________________ 
Evaluation of Catalysts A, B and C 
Catalyst A B C 
______________________________________ 
reaction temp., .degree. C. 
374 370 355 
product distribution, % by weight 
&lt;65.degree. C. 3.7 5.6 1.8 
65-180.degree. C. 50.8 46.2 26.6 
180-320.degree. C. 29.78 32.7 31.4 
yield 93.6 94.7 99.8 
______________________________________ 
As shown in Table 6, under various operation temperature, the catalysts of 
the invention achieve high activities and produce acceptable products. 
(3) Test on Selectivities of Catalysts D, E, B' and C' to Middle 
Distillates. 
Operation conditions and results for this test are shown in Table 7 and 8, 
respectively. 
TABLE 7 
______________________________________ 
Operation Conditions 
Pre-treated Vacuum 
gas oil 3, 18 .times. 10.sup.-4 % 
Feed Material by weight of N 
______________________________________ 
conversion of fractions with b.P. less than 
60 
350.degree. C., % by weight 
H.sub.2 partial pressure, MPa 14.7 
volume space velocity, h.sup.-1 1.5 
H.sub.2 /oil ratio, v/v 1500:1 
______________________________________ 
TABLE 8 
______________________________________ 
Evaluation Results 
Selectivityto middle 
Catalyst Reaction Temp, .degree. C. distillates* 
______________________________________ 
D 358 76.2 
E 360 75.8 
B' 371 76.4 
C' 358 74.7 
______________________________________ 
*selectivity to middle distillates = (weight of 132-350.degree. C. 
fractions)/(weight of 60-350.degree. C. fractions) 
As shown in Table 8, when selectivity of the catalyst of the invention to 
middle distillates is equal to that of Catalyst B', the reaction 
temperature with the catalyst of the invention can be decreased by 
13-15.degree. C. At the same reaction temperature, selectivity of Catalyst 
E is increased by 1.1% by weight compared with Catalyst C'. 
EXAMPLE 10 
Catalyst A is evaluated under different pressures. Pre-treated vacuum gas 
oil 2 is used and the results are shown in Table 9. 
TABLE 9 
______________________________________ 
Evaluation of Catalyst A Under Various Pressures 
H.sub.2 partial pressure, MPa 
9.8 7.84 6.37 
reaction temp, .degree. C. 365 365 368 
N content in feed material 8.5 
13.5 17.1 
10-4% by weight 
density of the product oil 0.7655 0.7844 0.7909 
(D.sub.4.sup.20), g/cm.sup.3 
product distribution, % 
by weight 
&lt;65.degree. C. 4.6 3.5 3.1 
65-180.degree. C. 36.0 27.9 25.1 
180-350.degree. C. 32.4 32.8 33.8 
&gt;350.degree. C. 24.8 30.7 36.4 
properties of the product 
6514 180.degree. C. naphtha 
PNA 52.2/43.1/4.7 46.7/45.6/7.7 47.0/43.5/9.5 
aromatic potential content, 45.3 50.9 50.7 
% by weight 
180-350.degree. C. diesel oil 
Solidification point, .sub.-- .degree. C. -- -16 -12 
diesel index -- 70.8 64.7 
BMCI value of &gt;350.degree. C. 9.1 10.7 8.5 
tail oil 
______________________________________ 
As shown in Table 9, desirable products can be produced under middle 
pressure even when nitrogen content in feed material is relatively high. 
EXAMPLE 11 
Stability Tests of the Catalysts 
(1) Stability Test of Catalyst A 
Stability of Catalyst A is tested for 2100 hours under 7.8 MPa using 
pre-treated vacuum gas oil 1 with a nitrogen content in the range of 
20-30.times.10.sup.-4 % by weight. When 60% conversion of fractions with a 
b.P. less than 320.degree. C. is kept constant, the reaction temperature 
is only increased by 3.degree. C. and the increase rate of temperature is 
0.034.degree. C./day, which indicates that catalyst of the invention has 
relatively high activity and stability even when nitrogen content is high. 
(2) Stability Test of Catalyst D 
Stability of Catalyst D prepared in Example 8 is tested for 5212 hours 
under the same operation conditions as those in (3) of Example 9. The 
reaction temperature is only increased by 5.degree. C. during the whole 
operation, which means that the catalyst of the invention possesses good 
stability.