Catalyst comprising a NU-88 zeolite, a group VB element and its use for hydroconverting hydrocarbon-containing petroleum feeds

The invention provides a hydrocracking catalyst comprising at least one NU-88 zeolite, at least one group VB metal, preferably niobium, at least one amorphous or low crystallinity matrix, optionally at least one metal selected from the group formed by group VIB and VIII metals, optionally at least one element selected from the group formed by phosphorous, boron and silicon, and optionally at least one group VIIA element. The invention also relates to the use of the catalyst for hydrocracking hydrocarbon-containing feeds.

SUMMARY OF THE INVENTION 
The present invention relates to a catalyst for hydrocracking 
hydrocarbon-containing feeds, said catalyst comprising at least one NU-88 
zeolite, a group VB metal, preferably niobium, at least one amorphous or 
low crystallinity oxide type matrix, optionally at least one metal 
selected from group VIB and VIII of the periodic table, preferably 
molybdenum or tungsten, cobalt, nickel or iron. The catalyst matrix 
optionally contains an element selected from the group formed by 
phosphorous, boron and silicon, and optionally at least one group VIIA 
element (group 17, the halogens), such as fluorine. 
The present invention also relates to processes for preparing said 
catalyst, and to its use for hydrocracking hydrocarbon-containing feeds 
such as petroleum cuts, or cuts from coal containing aromatic and/or 
olefinic and/or naphthenic and/or paraffinic compounds, said feeds 
possibly containing metals and/or nitrogen and/or oxygen and/or sulphur. 
Hydrocracking heavy petroleum feeds is a very important refining process 
which produces lighter fractions such as gasoline, jet fuel and light gas 
oil from surplus heavy feeds which are of low intrinsic value, which 
lighter fractions are needed by the refiner so that he can match 
production to demand. Certain hydrocracking processes can also produce a 
highly purified residue which can constitute excellent bases for oils. The 
importance of catalytic hydrocracking over catalytic cracking is that it 
can provide very good quality middle distillates, jet fuels and gas oils. 
The gasoline produced has a much lower octane number than that from 
catalytic cracking. 
All catalysts used for hydrocracking are bifunctional, combining an acid 
function and a hydrogenating function. The acid function is supplied by 
large surface area supports (150 to 800 m.sup.2 /g in general) with a 
superficial acidity, such as halogenated aluminas (in particular 
fluorinated or chlorinated), combinations of boron and aluminium oxides, 
amorphous silica-aluminas and zeolites. The hydrogenating function is 
supplied either by one or more metals from group VIII of the periodic 
table, such as iron, cobalt, nickel, ruthenium, rhodium, palladium, 
osmium, iridium or platinum, or by a combination of at least one metal 
from group VI of the periodic table and at least one group VIII metal. 
The equilibrium between the two, acid and hydrogenating, functions is the 
fundamental parameter which governs the activity and selectivity of the 
catalyst. A weak acid function and a strong hydrogenating function 
produces low activity catalysts which generally operate at a high 
temperature (390.degree. C. or above), and at a low supply space velocity 
(HSV, expressed as the volume of feed to be treated per unit volume of 
catalyst per hour, and is generally 2 h.sup.-1 or less), but have very 
good selectivity for middle distillates. In contrast, a strong acid 
function and a weak hydrogenating function produces active catalysts but 
selectivities for middle distillates are poorer. The search for a suitable 
catalyst is thus centred on the proper choice of each of the functions to 
adjust the activity/selectivity balance of the catalyst. 
One of the main points of hydrocracking is to exhibit high flexibility at 
various levels: flexibility in the catalysts used, which results in 
flexibility in the feeds to be treated and in the products obtained. One 
parameter which is easy to control is the acidity of the catalyst support. 
The vast majority of conventional catalytic hydrocracking catalysts are 
constituted by weakly acidic supports such as amorphous silica-aluminas. 
More particularly, such systems are used to produce very good quality 
middle distillates and, when their acidity is very low, oil bases. 
Weakly acid supports include amorphous silica-aluminas. Many catalysts on 
the hydrocracking market are based on silica-alumina combined either with 
a group VIII metal or, as is preferable when the amount of heteroatomic 
poisons in the feed to be treated exceeds 0.5% by weight, a combination of 
sulphides of groups VIB and VIII metals. The selectivity of such systems 
for middle distillates is very good, and the products formed are of high 
quality. The least acidic of such catalysts can also produce lubricating 
bases. The disadvantage of all such amorphous support-based catalytic 
systems is, as already stated, their low activity. 
The catalytic activity of catalysts comprising for example Y zeolite with 
structure type FAU or catalysts comprising for example a beta type zeolite 
is higher than that of amorphous silica-aluminas, but selectivities for 
light products are higher. 
Further, simple sulphides of group VB elements have been described as 
constituents of catalysts for hydrorefining hydrocarbon-containing feeds, 
for example niobium trisulphide described in United States patent U.S. 
Pat. No. 5,294,333. Mixtures of simple sulphides comprising at least one 
group VB element and a group VIB element have also been tested as 
constituents for catalysts for hydrorefining hydrocarbon-containing feeds, 
as for example in U.S. Pat. No. 4,910,181 and U.S. Pat. No. 5,275,994. 
Research carried out by the Applicant on a number of zeolites and 
crystalline microporous solids have led to the discovery that, 
surprisingly, a catalyst for hydrocracking hydrocarbon-containing feeds 
characterized in that it comprises at least one NU-88 zeolite, at least 
one amorphous or low crystallinity mineral matrix, which is generally 
porous, such as alumina, at least one element from group VB of the 
periodic table, such as tantalum, niobium or vanadium, preferably niobium, 
optionally at least one element from group VIB of that periodic table, 
such as chromium, molybdenum or tungsten, preferably molybdenum or 
tungsten, more preferably molybdenum, optionally a group VIII element, 
i.e., an element selected from the group formed by: Fe, Ru, Os, Co, Rh, 
Ir, Ni, Pd, Pt, preferably iron, cobalt or nickel, optionally an element 
selected from the group formed by P, B and Si, and optionally a group VIIA 
element, preferably fluorine, can produce activities, i.e., a degree of 
conversion, which are higher than those of known prior art catalysts. 
The catalyst has a higher hydrocracking activity than those of prior art 
catalytic formulae based on group VIB elements. Without wishing to be 
bound to a particular theory, it appears that this particularly high 
activity of the catalysts of the present invention is due to the 
particular properties of the sulphide of the group VB element. The 
presence of such a sulphide with acidic properties not only improves the 
cracking properties but also improves the hydrogenating, 
hydrodesulphuration, and hydrodenitrogenation properties over those of a 
group VIB element sulphide and in particular a molybdenum or tungsten 
sulphide normally used for the hydrogenating function. 
The catalyst of the present invention generally comprises, in weight % with 
respect to the total catalyst weight: 
0.1% to 99.8%, preferably 0.1% to 90%, more preferably 0.1% to 80%, and 
particularly preferably 0.1% to 70%, of a NU-88 zeolite; 
0.1% to 60%, preferably 0.1% to 50%, more preferably 0.1% to 40%, of at 
least one metal selected from group VB; 
0.1% to 99%, preferably 1% to 99%, of an amorphous or low crystallinity 
oxide type porous mineral matrix; 
said catalyst being characterized in that it optionally comprises: 
0 to 60%, preferably 0.1% to 50%, more preferably 0.1% to 40%, of at least 
one metal selected from group VIII and group VIB elements; 
0 to 20%, preferably 0.1% to 15%, more preferably 0.1% to 10%, of at least 
one promoter element selected from the group formed by silicon, boron and 
phosphorous, not including the silicon possibly contained in the zeolite 
framework; 
and optionally again: 
0 to 20%, preferably 0.1% to 15%, more preferably 0.1% to 10%, of at least 
one element selected from group VIIA, preferably fluorine. 
When it is present, the promoter element silicon is in its amorphous form 
and mainly located on the matrix. 
The group VB, group VIB and group VIII metals in the catalyst of the 
present invention can be completely or partially present in the form of 
the metal and/or oxide and/or sulphide. 
The catalysts of the invention can be prepared using any of the methods 
known to the skilled person. 
A preferred method for preparing the catalyst of the present invention 
comprises the following steps: 
a) drying and weighing a solid termed the precursor, comprising at least 
the following compounds: at least one matrix, at least one NJ-88 zeolite, 
optionally at least one element selected from the group formed by group 
VIB and group VIII elements, optionally at least one element selected from 
the group phosphorous, boron and silicon, and optionally at least one 
group VIIA element, the whole preferably having been formed; 
b) calcining the dry solid obtained in step a) at a temperature of at least 
150.degree. C.; 
c) impregnating the solid precursor defined in step b) with a solution 
containing a group VB element, preferably niobium; 
d) leaving the moist solid in a moist atmosphere at a temperature in the 
range 10.degree. C. to 120.degree. C.; 
e) drying the moist solid obtained in step d) at a temperature in the range 
60.degree. C. to 150.degree. C. 
The precursor of step a) above can be produced using any of the 
conventional methods available to the skilled person. In a further 
preferred preparation method, the precursor is obtained by mixing at least 
one matrix and at least one NU-88 zeolite then forming, drying and 
calcining. The group VIB, VIII elements and those selected from 
phosphorous, boron, silicon and group VIIA elements are then optionally 
introduced using any method which is available to the skilled person, in 
any one of steps a) to e), before or after forming and before or after 
calcining the precursor or the catalyst. 
Forming can be carried out by extrusion, pelletization, by the oil drop 
method, by rotating plate granulation or using any other method which is 
well known to the skilled person. At least one calcining step can be 
carried out after any one of the preparation steps; it is normally carried 
out in air at a temperature of at least 150.degree. C., preferably at 
least 300.degree. C. Thus the product obtained after step a) and/or step 
e) and/or optionally after introducing the element or elements from groups 
VIB, VIII, those selected from phosphorous, boron, silicon, and the group 
VIIA elements, are optionally calcined in air, usually at a temperature of 
at least 150.degree. C., preferably at least 250.degree. C., routinely 
about 350.degree. C. to 1000.degree. C. 
The hydrogenating element can be introduced at any step in the preparation, 
preferably during mixing, or more preferably after forming. Forming is 
followed by calcining; the hydrogenating element can also be introduced 
before or after calcining. Preparation is generally completed by calcining 
at a temperature of 250.degree. C. to 600.degree. C. A further preferred 
method consists of mixing at least one NU-88 zeolite powder in a moist 
alumina gel for a few tens of minutes, then passing the paste obtained 
through a die to form extrudates with a diameter in the range 0.4 to 4 mm. 
The hydrogenating function can then be introduced only partially (in the 
case, for example of combinations of oxides of groups VIB and VIII metals) 
or completely on mixing the zeolite, i.e., at least one NU-88 zeolite, 
with at least one gel of the oxide selected as the matrix. It can also be 
introduced by one or more ion exchange operations carried out on the 
calcined support constituted by at least one NU-88 zeolite dispersed in at 
least one matrix, using solutions containing precursor salts of the 
selected metals when these are from group VIII. It can also be introduced 
by one or more steps for impregnating the formed and calcined support 
using a solution of precursors of group VIII metal oxides (in particular 
cobalt or nickel) when the precursors of the group VIB metal oxides (in 
particular molybdenum or tungsten) have already been introduced on mixing 
the support. Finally, it can also be introduced by one or more steps for 
impregnating the calcined support constituted by at least one NU-88 
zeolite and at least one matrix, using solutions containing precursors of 
oxides of group VI and/or group VIII metals, the precursors of the oxides 
of at least one group VIII metal preferably being introduced after those 
of group VIB or at the same time as the latter. 
The support is preferably impregnated using an aqueous solution. The 
support is preferably impregnated using the "dry" impregnation method 
which is well known to the skilled person. Impregnation can be carried out 
in a single step using a solution containing all of the constituent 
elements of the final catalyst. 
The boron and/or silicon and/or phosphorous and optionally the element 
selected from group VIIA, preferably fluorine, can be introduced onto the 
catalyst at any stage in the preparation and using any technique known to 
the skilled person. 
One preferred method of the invention consists of depositing the selected 
promoter elements, for example a boron-silicon combination, onto the 
calcined or non calcined precursor (preferably calcined). To this end, an 
aqueous solution of at least one boron salt such as ammonium biborate or 
ammonium pentaborate is prepared in an alkaline medium and in the presence 
of hydrogen peroxide and dry impregnation is carried out, in which the 
pore volume of the precursor is filled with the solution containing boron, 
for example. When silicon is also deposited, for example, a silicone type 
silicon compound can be used. 
Boron and silicon can also be deposited simultaneously using a solution 
containing a boron salt and a silicone type silicon compound, for example. 
Thus, in the case where the precursor is a nickel-molybdenum type catalyst 
supported on alumina and NU-88, for example, it is possible to impregnate 
this precursor with an aqueous solution of ammonium biborate or Rhodorsil 
E1P silicone from Rhone Poulenc, dry at 80.degree. C., for example, 
impregnate with an ammonium fluoride solution, then dry at 80.degree. C., 
for example, followed by calcining, preferably in air in a traversed bed, 
for example at 500.degree. C. for 4 hours. The group VB element is then 
deposited using any method which is known to the skilled person. 
The promoter element selected from the group formed by silicon, boron and 
phosphorous and the element selected from group VIIA halide ions can be 
introduced onto the calcined precursor using one or more impregnation 
operations using an excess of solution. 
Thus, for example, it is possible to impregnate this precursor with an 
aqueous solution of ammonium biborate or Rhodorsil E1P silicone from Rhone 
Poulenc, dry at 80.degree. C., for example, impregnate with an ammonium 
fluoride solution, then dry at 80.degree. C., for example, followed by 
calcining, preferably in air in a traversed bed, for example at 
500.degree. C. for 4 hours. The group VB element is then deposited using 
any method which is known to the skilled person. 
Other impregnation sequences can be used to obtain the catalyst of the 
invention. 
As an example, the precursor can be impregnated with a solution containing 
the promoter elements (P, B, Si), dried, calcined then the solid obtained 
can be impregnated with a solution containing a further promoter element, 
dried, then calcined. The precursor can also be impregnated with a 
solution containing two promoter elements, dried, calcined then the solid 
obtained can be impregnated with a solution containing a further promoter 
element, dried, then a final calcining step can be carried out. The group 
VB element is then deposited using any method which is known to the 
skilled person. 
The catalyst of the present invention can optionally comprise a group VIII 
element such as iron, cobalt, nickel, ruthenium, rhodium, palladium, 
osmium, iridium or platinum. Preferred group VIII metals are those 
selected from the group formed by iron, cobalt, nickel and ruthenium. 
Advantageously, the following combinations of metals are used: 
nickel-niobium-molybdenum, cobalt-niobium-molybdenum, 
iron-niobium-molybdenum, nickel-niobium-tungsten, cobalt-niobium-tungsten, 
iron-niobium-tungsten. Preferred combinations are: 
nickel-niobium-molybdenum, cobalt-niobium-molybdenum. It is also possible 
to use combinations of four metals, for example 
nickel-cobalt-niobium-molybdenum. Combinations containing a noble metal, 
such as ruthenium-niobium-molybdenum, or 
ruthenium-nickel-niobium-molybdenum, can also be used. 
When the elements are introduced in a plurality of impregnation steps using 
the corresponding precursor salts, an intermediate catalyst calcining step 
must be carried out at a temperature which is preferably in the range 
250.degree. C. to 600.degree. C., for example. 
Molybdenum impregnation can be facilitated by adding phosphoric acid to 
ammonium paramolybdate solutions, which enables phosphorous to be 
introduced as well to promote the catalytic activity. Other phosphorous 
compounds can be used, as is well known to the skilled person. 
Niobium impregnation can be facilitated by adding oxalic acid and 
optionally ammonium oxalate to niobium oxalate solutions. Other compounds 
can be used to improve solubility and facilitate niobium impregnation, as 
is well known to the skilled person. 
Sulphurisation of solids (catalysts) containing at least one group VB 
element in its oxide form has proved to be very difficult in the majority 
of conventional sulphurisation methods known to the skilled person. 
Catalysts containing at least one group VB element supported on an alumina 
type matrix are known to be very difficult to sulphurise once the 
combination of the group VB element and alumina has been calined at a 
temperature of over 200.degree. C. 
Sulphurisation can take place using any method known to the skilled person 
and at any stage of the preparation. The preferred method of the invention 
consists of heating the non calcined catalyst in a stream of a 
hydrogen-hydrogen sulphide mixture or in a stream of a nitrogen-hydrogen 
sulphide mixture or in a stream of pure hydrogen sulphide at a temperature 
in the range 150.degree. C. to 800.degree. C., preferably 250.degree. C. 
to 600.degree. C., generally in a traversed bed reaction zone. Thus, in 
the preferred case when the group VB metal is niobium and the group VIB 
metal is molybdenum, it is possible to impregnate the support, for example 
the alumina-NU-88 mixture, using ammonium heptamolybdate, dry at 
80.degree. C., then impregnate using niobium oxalate, dry at 80.degree. 
C., then sulphurise, for example and as is preferred, using H.sub.2 S in a 
traversed bed, for example at 500.degree. C. for 10 hours. 
The NU-88 zeolite used in the present invention is characterized by: 
i) a chemical composition with the following formula, expressed in terms of 
the mole ratios of the oxides for the anhydrous state: 
EQU 100.times.O.sub.2, mY.sub.2 O.sub.3, pR.sub.2/n O 
where m is 10 or less; p is 20 or less; R represents one or more cations 
with valency n; X represents silicon and/or germanium, preferably silicon; 
Y is selected from the group formed by the following elements: aluminium, 
iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, 
antimony, chromium and manganese, Y preferably being aluminium; and 
ii) an X ray diffraction diagram, in its as synthesised state, which 
comprises the results shown in Table 1. 
TABLE 1 
______________________________________ 
X ray diffraction diagram for NU-88 zeolite (as synthesised state) 
d.sub.hkl (10.sup.-10 m) 
I/I.sub.max 
______________________________________ 
12.1 .+-. 0.35 s or vs (1) 
11.0 .+-. 0.30 s (1) 
9.88 .+-. 0.25 m (1) 
6.17 .+-. 0.15 w 
3.97 .+-. 0.09 vs (2) 
3.90 .+-. 0.08 vs (2) 
3.80 .+-. 0.08 w (2) 
3.66 .+-. 0.07 vw 
3.52 .+-. 0.07 vw 
3.27 .+-. 0.07 vw 
3.09 .+-. 0.06 w 
2.91 .+-. 0.06 w 
2.68 .+-. 0.06 vw 
2.49 .+-. 0.05 vw 
2.20 .+-. 0.05 vw 
2.059 .+-. 0.05 w 
1.729 .+-. 0.04 vw 
______________________________________ 
(1) These peaks were not resolved and formed part of a feature. 
(2) these peaks were not resolved and formed part of the same feature. 
The invention also concerns NU-88 in its hydrogen form, termed H-NU-88, 
produced by calcining and/or ion exchange as will be described below. 
H-NU-88 zeolite has an X ray diffraction diagram which comprises the 
results shown in Table 2. 
TABLE 2 
______________________________________ 
X ray diffraction diagram for NU-88 zeolite (hydrogen form) 
d.sub.hkl (10.sup.-10 m) 
I/I.sub.max 
______________________________________ 
12.1 .+-. 0.35 vs (1) 
11.0 .+-. 0.30 s or vs (1) 
9.92 .+-. 0.25 w or m (1) 
8.83 .+-. 0.20 vw 
6.17 .+-. 0.15 w 
3.99 .+-. 0.10 s or vs (2) 
3.91 .+-. 0.08 vs (2) 
3.79 .+-. 0.08 w or m (2) 
3.67 .+-. 0.07 vw 
3.52 .+-. 0.07 vw 
3.09 .+-. 0.06 w 
2.90 .+-. 0.06 w 
2.48 .+-. 0.05 w 
2.065 .+-. 0.05 w 
1.885 .+-. 0.04 vw 
1.733 .+-. 0.04 vw 
______________________________________ 
(1) These peaks were not resolved and formed part of a feature. 
(2) these peaks were not resolved and formed part of the same feature. 
These diagrams were obtained using a diffractometer and a conventional 
powder method utilising the K.sub..alpha. line of copper, Cu K alpha. From 
the position of the diffraction peaks represented by the angle 2.theta., 
the characteristic interplanar distances d.sub.hkl of the sample can be 
calculated using the Bragg equation. The intensity is calculated on the 
basis of a relative intensity scale attributing a value of 100 to the line 
representing the strongest peak on the X ray diffraction diagram, and 
then: 
very weak (vw) means less than 10; 
weak (w) means less than 20; 
medium (m) means in the range 20 to 40; 
strong (s) means in the range 40 to 60; 
very strong (vs) means more than 60. 
The X ray diffractograms from which the data are obtained (spacing d and 
relative intensities) are characterized by large reflections with a large 
number of peaks forming shoulders on other peaks of higher intensity. Some 
or all of the shoulders may not be resolved. This may be the case for 
samples with low crystallinity or for samples with crystals which are 
small enough to produce significant broadening of the X rays. This can 
also be the case when the equipment or operating conditions used to 
produce the diagram differ from those used in the present case. 
NU-88 zeolite is considered to have a novel basic structure or topology 
which is characterized by its X ray diffraction diagram. NU-88 zeolite in 
its "as synthesised state" has substantially the X ray diffraction 
characteristics shown in Table 1, and is thus distinguished from prior art 
zeolites. The invention also concerns any zeolite with the same structural 
type as that of NU-88 zeolite. 
Tables 1 and 2 and the diffractograms of FIGS. 1 and 2 are relatively 
unusual for zeolitic structures. Thus these data appear to indicate that 
NU-88 zeolite has a defective structure. 
In the chemical composition defined above, m is generally in the range 0.1 
to 10, preferably 0.2 to 9, and more preferably 0.6 to 8; it appears that 
NU-88 zeolite is generally and most readily obtained in a very pure form 
when m is in the range 0.6 to 8. 
This definition also includes NU-88 zeolite in its "as synthesised state", 
as well as the forms obtained on dehydration and/or calcining and/or ion 
exchange. The term "in its as synthesised state" designates the product 
obtained by synthesis and washing, with or without drying or dehydration. 
In its "as synthesised state", NU-88 zeolite may contain a cation of metal 
M, which is an alkali, in particular sodium, and/or ammonium, and it may 
contain organic nitrogen-containing cations such as those described below 
or their decomposition products, or precursors thereof. These organic 
nitrogen-containing cations are designated here by the letter Q, which 
also includes decomposition products and precursors of the organic 
nitrogen-containing cations. 
Thus NU-88 zeolite in its "as synthesised state" (not calcined) is 
characterized by: 
i) a chemical composition with the following formula, expressed in terms of 
the mole ratios of the oxides for the anhydrous state: 
EQU 100.times.O.sub.2 : 10 or less Y.sub.2 O.sub.3 : 10 or less Q: 10 or less 
M.sub.2 O, 
where 
X represents silicon and/or germanium; 
Y is selected from the group formed by the following elements: aluminium, 
iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, 
antimony, chromium and manganese; 
M is at least one alkali metal cation (group IA of the periodic table) 
and/or ammonium; and 
Q is at least one organic nitrogen-containing cation or a precursor of an 
organic nitrogen-containing cation or a decomposition product of an 
organic nitrogen-containing cation; 
ii) an X ray diffraction diagram, in its as synthesised state, which 
comprises the results shown in Table 1. 
The compositions indicated above for NU-88 zeolite are given for the 
anhydrous state, since the NU-88 zeolite in its "as synthesised state" and 
activated forms of the NU-88 zeolite, i.e., resulting from calcining 
and/or ion exchange, may contain water. The mole ratio of H.sub.2 O of 
such forms, including NU-88 zeolite in its "as synthesised state", depends 
on the conditions under which it is prepared and stored after synthesis or 
activation. The molar quantities of water contained in these forms are 
typically in the range 0 to 100% .times.O.sub.2. 
The calcined forms of NU-88 zeolite do not contain any organic 
nitrogen-containing compound, or contain a lesser quantity than the "as 
synthesised state", since the major portion of the organic substance has 
been eliminated, generally by heat treatment consisting of burning off the 
organic substance in the presence of air, the hydrogen ion (H.sup.+) thus 
forming the other cation. 
Thus the NU-88 zeolite in its hydrogen form is characterized by: 
i) a chemical composition with the following formula, expressed in terms of 
the mole ratios of the oxides for the anhydrous state: 
EQU 100.times.O.sub.2 : 10 or less Y.sub.2 O.sub.3 : 10 or less M.sub.2 O, 
where 
X represents silicon and/or germanium; 
Y is selected from the group formed by the following elements: aluminium, 
iron, gallium, boron, titanium, vanadium, zirconium, molybdenum, arsenic, 
antimony, chromium and manganese; and 
M is at least one alkali metal cation (group IA of the periodic table) 
and/or ammonium and/or hydrogen; 
ii) an X ray diffraction diagram, in its as synthesised state, which 
comprises the results shown in Table 2. 
Of the NU-88 zeolite forms which can be obtained by ion exchange, the 
ammonium form (NH.sub.4.sup.+) is important as it can readily be converted 
into the hydrogen form by calcining. The hydrogen form and forms 
containing metals introduced by ion exchange will be described below. In 
some cases, the fact that the zeolite of the invention is subjected to the 
action of an acid can give rise to partial or complete elimination of a 
base element such as aluminium, as well as generation of the hydrogen 
form. This may constitute a means of modifying the composition of the 
substance after it has been synthesised. 
NU-88 zeolite in its hydrogen form (acid form), termed H-NU-88, produced by 
calcining and ion exchange as will be described below. 
NU-88 zeolite which is at least partially in its H.sup.+ form (as defined 
above) or in its NH.sub.4.sup.+ form or in its metal form, said metal 
being selected from the group formed by groups IA, IB, IIA, IIB, IIIA, 
IIIB (including the rare earths), VIII, Sn, Pb and Si, preferably at least 
partially in its H.sup.+ form or at least partially in its metal form, can 
also be used. This type of zeolite generally has an X ray diffraction 
diagram which includes the results shown in Table 1. 
Preferably, the NU-88 zeolite is at least partially in its acid form (and 
preferably completely in its H form) or partially exchanged with metal 
cations, for example alkaline-earth metal cations. 
The NU-88 zeolites which form part of the composition of the invention are 
used with the silicon and aluminium contents obtained on synthesis. 
When the support comprises at least one matrix, the porous mineral matrix, 
which is normally amorphous or of low crystallinity, is generally 
constituted by at least one refractory oxide in its amorphous or low 
crystallinity form. Said matrix is preferably selected from the group 
formed by alumina, silica, silica-alumina or a mixture of at least two of 
the oxides cited above. Aluminates can also be used. Preferably, matrices 
containing alumina in any of its forms which are known to the skilled 
person are used, preferably gamma alumina. 
Sources of the group VB element which can be used are well known to the 
skilled person. Examples of niobium sources are oxides such as diniobium 
pentoxide Nb.sub.2 O.sub.5, niobic acid Nb.sub.2 O.sub.5.H.sub.2 O, 
niobium hydroxides and polyoxoniobates, niobium alkoxides with formula 
Nb(OR.sub.1).sub.3 where R.sub.1 is an alkyl radical, niobium oxalate 
NbO(HC.sub.2 O.sub.4).sub.5, and ammonium niobate. Preferably, niobium 
oxalate or ammonium niobate are used. 
The sulphur source can be elemental sulphur, carbon disulphide, hydrogen 
sulphide, sulphur-containing hydrocarbons such as dimethyl sulphide, 
dimethyl disulphide, mercaptans, thiophene compounds, thiols, 
polysulphides such as ditertiononylpolysulphide or TPS-37 from ATOCHEM, 
sulphur-rich petroleum cuts such as gasoline, kerosine, gas oil, used 
alone or mixed with the sulphur-containing compounds cited above. The 
preferred sulphur source is carbon disulphide or hydrogen sulphide. 
The preferred phosphorous source is orthophosphoric acid H.sub.3 PO.sub.4, 
but its salts and esters such as ammonium phosphates are also suitable. 
Phosphorous can, for example, be introduced in the form of a mixture of 
phosphoric acid and a basic organic compound containing nitrogen, such as 
ammonia, primary and secondary amines, cyclic amines, pyridine group 
compounds, quinolines, and pyrrole group compounds. 
A variety of silicon sources can be used. Examples are ethyl orthosilicate 
Si(OEt).sub.4, siloxanes, polysiloxanes, silicones, silicone emulsions and 
halogenated silicates such as ammonium fluorosilicate (NH.sub.4).sub.2 
SiF.sub.6 or sodium fluorosilicate Na.sub.2 SiF.sub.6. Silicomolybdic acid 
and its salts, and silicotungstic acid and its salts can also 
advantageously be used. Silicon can be added, for example, by impregnating 
ethyl silicate in solution in a water/alcohol mixture. Silicon can also be 
added, for example, by impregnation using a silicone type silicon compound 
suspended in water. 
The boron source can be boric acid, preferably orthoboric acid H.sub.3 
BO.sub.3, ammonium biborate or pentaborate, boron oxide, or boric esters. 
Boron can, for example, be introduced in the form of a mixture of boric 
acid, hydrogen peroxide and a basic organic compound containing nitrogen, 
such as ammonia, primary and secondary amines, cyclic amines, pyridine 
group compounds, quinolines, and pyrrole group compounds. Boron can, for 
example, be introduced using a solution of boric acid in a water/alcohol 
mixture. 
Sources of group VIIA elements which can be used are well known to the 
skilled person. As an example, fluoride anions can be introduced in the 
form of hydrofluoric acid or its salts. Such salts are formed with alkali 
metals, ammonium or an organic compound. In the latter case, the salt is 
advantageously formed in the reaction mixture by reacting the organic 
compound with hydrofluoric acid. It is also possible to use hydrolysable 
compounds which can liberate fluoride anions in water, such as ammonium 
fluorosilicate (NH.sub.4).sub.2 SiF.sub.6, silicon tetrafluoride SiF.sub.4 
or sodium fluorosilicate Na.sub.2 SiF.sub.6. Fluorine can be introduced, 
for example, by impregnating an aqueous hydrofluoride solution or ammonium 
fluoride. 
Sources of group VIB elements which can be used are well known to the 
skilled person. Examples of molybdenum and tungsten sources are oxides and 
hydroxides, molybdic acids and tungstic acids and their salts, in 
particular ammonium salts such as ammonium molybdate, ammonium 
heptamolybdate, ammonium tungstate, phosphomolybdic acid, phosphotungstic 
acid and their salts, silicomolybdic acid, silicotungstic acid and their 
salts. Preferably, oxides and ammonium salts are used, such as ammonium 
molybdate, ammonium heptamolybdate and ammonium tungstate. 
The sources of the group VIII elements which can be used are well known to 
the skilled person. Examples of sources of non noble metals are nitrates, 
sulphates, phosphates, halides, for example chlorides, bromides and 
fluorides, and carboxylates, for example acetates and carbonates. Examples 
of sources of noble metals are halides, for example chlorides, nitrates, 
acids such as chloroplatinic acid, and oxychlorides such as ammoniacal 
ruthenium oxychloride. 
The catalysts obtained in the present invention are formed into grains of 
different shapes and dimensions. They are generally used in the form of 
cylindrical or polylobed extrudates such as bilobes, trilobes, or 
polylobes with a straight or twisted shape, but they can also be produced 
and used in the form of compressed powder, tablets, rings, beads or 
wheels. The specific surface area is measured by nitrogen adsorption using 
the BET method (Brunauer, Emmett, Teller, J. Am. Chem. Soc., vol. 60, 
309-316 (1938)) and is in the range 50 to 600 m.sup.2 /g, the pore volume 
measured using a mercury porisimeter is in the range 0.2 to 1.5 cm.sup.3 
/g and the pore size distribution may be unimodal, bimodal or polymodal. 
The catalysts obtained in the present invention are used for hydrocracking 
hydrocarbon feeds such as petroleum cuts. The feeds used in the process 
are gasolines, kerosines, gas oils, vacuum gas oils, atmospheric residues, 
vacuum residues, atmospheric distillates, vacuum distillates, heavy fuels, 
oils, waxes and paraffins, spent oil, deasphalted residues or crudes, 
feeds from thermal or catalytic conversion processes, and their mixtures. 
They contain heteroatoms such as sulphur, oxygen and nitrogen and possibly 
metals. 
The catalysts obtained are advantageously used for hydrocracking, in 
particular of vacuum distillate type heavy hydrocarbons, deasphalted 
residues or hydrotreated residues or the like. The heavy cuts are 
preferably constituted by at least 80% by volume of compounds with a 
boiling point of at least 350.degree. C., preferably in the range 
350.degree. C. to 580.degree. C. (i.e., corresponding to compounds 
containing at least 15 to 20 carbon atoms). They generally contain 
heteroatoms such as sulphur and nitrogen. The nitrogen content is usually 
in the range 1 to 5000 ppm by weight and the sulphur content is in the 
range 0.01% to 5% by weight. 
The hydrocracking conditions such as temperature, pressure, hydrogen 
recycle ratio, and hourly space velocity, can vary widely depending on the 
nature of the feed, the quality of the desired products and the facilities 
available to the refiner. The temperature is generally over 200.degree. C. 
and usually in the range 250.degree. C. to 480.degree. C. The pressure is 
over 0.1 MPa and usually over 1 MPa. The quantity of hydrogen is a minimum 
of 50 liters of hydrogen per liter of feed and usually in the range 80 to 
5000 liters of hydrogen per liter of feed. The hourly space velocity is 
generally in the range 0.1 to 20 volumes of feed per volume of catalyst 
per hour. 
The catalysts of the present invention preferably undergo sulphurisation to 
transform at least part of the metallic species to the sulphide before 
bringing them into contact with the feed to be treated. This activation 
treatment by sulphurisation is well known to the skilled person and can be 
carried out using any method already described in the literature. 
One conventional sulphurisation method which is well known to the skilled 
person consists of heating in the presence of hydrogen sulphide to a 
temperature in the range 150.degree. C. to 800.degree. C., preferably in 
the range 250.degree. C. to 600.degree. C., generally in a traversed bed 
reaction zone. 
The catalyst of the present invention can advantageously be used for 
hydrocracking hydrocarbon-containing feeds, in particular vacuum 
distillate type cuts, more particularly cuts with a sulphur content of 
over 0.1% by weight and a nitrogen content of over 10 ppm. 
In a first implementation, or partial hydrocracking, also known as mild 
hydrocracking, the degree of conversion is below 55%. The catalyst of the 
invention is thus used at a temperature which is generally 230.degree. C. 
or more, preferably in the range 300.degree. C. to 480.degree. C., and 
usually in the range 350.degree. C. to 450.degree. C. The pressure is 
generally over 2 MPa and preferably 3 MPa, less than 12 MPa and preferably 
less than 10 MPa. The quantity of hydrogen is a minimum of 100 liters of 
hydrogen per liter of feed and usually in the range 200 to 3000 liters of 
hydrogen per liter of feed. The hourly space velocity is generally in the 
range 0.1 to 10 h.sup.-1. Under these conditions, the catalysts of the 
present invention have better activities for conversion, 
hydrodesulphuration and hydrodenitrogenation than commercially available 
catalysts. 
In a second implementation, the catalyst of the present invention can be 
used for partial hydrocracking, advantageously under moderate hydrogen 
pressure conditions, of cuts such as vacuum distillates containing high 
sulphur and nitrogen contents which have already been hydrotreated. In 
this hydrocracking mode, the degree of conversion is below 55%. In this 
case, the petroleum cut is converted in two steps, the catalysts of the 
invention being used in the second step. The catalyst of the first step 
has a hydrotreatment function and comprises a matrix, preferably 
alumina-based, preferably containing no zeolite, and at least one metal 
with a hydrogenating function. Said matrix is an amorphous or low 
crystallinity oxide type porous mineral matrix. Non limiting examples are 
aluminas, silicas, and silica-aluminas. Aluminates can also be used. 
Preferably, matrices containing alumina are used, in any of the forms 
known to the skilled person, and more preferably aluminas, for example 
gamma aluminas, are used. The hydrotreatment function is ensured by at 
least one metal or metal compound from group VIII, such as nickel or 
cobalt. A combination of at least one metal or metal compound from group 
VIB (for example molybdenum or tungsten) and at least one metal or metal 
compound from group VIII (for example cobalt or nickel) can be used. The 
total concentration of groups VIB and VIII metal oxides is preferably in 
the range 5% to 40% by weight, most preferably in the range 7% to 30% by 
weight, and the weight ratio, expressed as the metal oxide of the group 
VIB metal (or metals) to that of the group VIII metal (or metals) is 
preferably in the range 1.25 to 20, more preferably in the range 2 to 10. 
Further, this catalyst can contain phosphorous. The phosphorous content, 
expressed as the concentration of phosphorous pentoxide P.sub.2 O.sub.5 is 
preferably at most 15%, more preferably in the range 0.1% to 15% by 
weight, and very preferably in the range 0.15% to 10% by weight. It can 
also contain boron in a ratio B/P=1.05-2 (atomic), the sum of the B and P 
contents, expressed as the oxides, preferably being in the range 5% to 15% 
by weight. 
The first step is generally carried out at a temperature of 350-460.degree. 
C., preferably 360-450.degree. C.; the pressure is at least 2 MPa, 
preferably at least 3 MPa; and the hourly space velocity is 0.1-5 
h.sup.-1, preferably 0.2-2 h.sup.-1, with a quantity of hydrogen at least 
100 liters of hydrogen per liter of feed, preferably 260-3000 liters of 
hydrogen per liter of feed. 
In the conversion step using the catalyst of the invention (or second 
hydrocracking step), the temperatures are generally 230.degree. C. or more 
and usually in the range 300.degree. C. to 480.degree. C., preferably in 
the range 330.degree. C. to 450.degree. C. The pressure is generally at 
least 2 MPa, preferably at least 3 MPa; it is less than 12 MPa and 
preferably less than 10 MPa. The quantity of hydrogen is a minimum of 100 
liters of hydrogen per liter of feed and usually in the range 200 to 3000 
liters of hydrogen per liter of feed. The hourly space velocity is 
generally in the range 0.15 to 10 h.sup.-1. Under these conditions, the 
catalysts of the present invention have better activities for conversion, 
hydrodesulphuration, and hydrodenitrogenation and a better selectivity for 
middle distillates than commercially available catalysts. The service life 
of the catalysts is also improved in the moderate pressure range. 
In a further implementation, the catalyst of the present invention can be 
used for hydrocracking under high hydrogen pressure conditions of at least 
5 MPa. The treated cuts are, for example, vacuum distillates containing 
high sulphur and nitrogen contents which have already been hydrotreated. 
In this hydrocracking mode, the degree of conversion is over 55%. In this 
case, the petroleum cut conversion process is carried out in two steps, 
the catalyst of the invention being used in the second step. 
The catalyst of the first step has a hydrotreatment function and comprises 
a matrix, preferably alumina-based, preferably containing no zeolite, and 
at least one metal with a hydrogenating function. Said matrix can also be 
constituted by, or comprise, a silica, silica-alumina, boron oxide, 
magnesia, zirconia, titanium oxide or a combination of these oxides. The 
hydro-dehydrogenating function is ensured by at least one group VIII metal 
or metal compound such as nickel or cobalt. A combination of at least one 
metal or metal compound from group VI (for example molybdenum or tungsten) 
and at least one metal or metal compound from group VIII (for example 
cobalt or nickel) can be used. The total concentration of groups VI and 
VIII metal oxides is in the range 5% to 40% by weight, preferably in the 
range 7% to 30% by weight, and the weight ratio, expressed as the metal 
oxide of the group VI metal (or metals) to that of the group VIII metal 
(or metals) is preferably in the range 1.25 to 20, more preferably in the 
range 2 to 10. Further, this catalyst can contain phosphorous. The 
phosphorous content, expressed as the concentration of phosphorous 
pentoxide P.sub.2 O.sub.5, is at most 15%, preferably in the range 0.1% to 
15% by weight, and more preferably in the range 0.15% to 10% by weight. It 
can also contain boron in a ratio B/P=1.02-2 (atomic), the sum of the B 
and P contents, expressed as the oxides, preferably being in the range 5% 
to 15% by weight. 
The first step is generally carried out at a temperature of 350-460.degree. 
C., preferably 360-450.degree. C.; the pressure is over 2 MPa, preferably 
at least 3 MPa; the hourly space velocity is 0.1-5 h.sup.-1, preferably 
0.2-2 h.sup.-1 ; and the quantity of hydrogen is at least 100 liters of 
hydrogen per liter of feed, preferably 260-3000 liters of hydrogen per 
liter of feed. 
For the conversion step using the catalyst of the invention (or second 
step), the temperatures are generally 230.degree. C. or more, usually in 
the range 300.degree. C. to 480.degree. C., preferably in the range 
300.degree. C. to 440.degree. C. The pressure is generally over 5 MPa, 
preferably over 7 MPa. The quantity of hydrogen is a minimum of 100 liters 
of hydrogen per liter of feed, usually in the range 200 to 3000 liters of 
hydrogen per liter of hydrogen per liter of feed. The hourly space 
velocity is generally in the range 0.15 to 10 h.sup.-1 
Under these conditions, the catalysts of the present invention have better 
activities for conversion than commercially available catalysts, even with 
considerably lower zeolite contents than those of commercially available 
catalysts. 
The following examples illustrate the present invention without in any way 
limiting its scope.

EXAMPLE 1: PREATION OF A HYDROCRACKING CATALYST SUPPORT CONTAINING A 
NU-88 ZEOLITE 
NU-88 zeolite was synthesized from hexane-1,6-bis(methylpyrrolidinium) 
bromide (HexPyrr). The structure of hexane-1,6-bis (methylpyrrolidinium) 
bromide (HexPyrr) is as follows: 
##STR1## 
A reaction mixture with molar composition: 
EQU 60 SiO.sub.2 : 2 Al.sub.2 O.sub.3 : 10 Na.sub.2 O; 10 HexPyrr: 3000 H.sub.2 
O 
was prepared from: 
48.07 g of "CAB-O-SEL" (BDH Ltd); 
12.303 g of SoAl 235 solution (Laroche) (composition in weight %: 22.10% 
Al.sub.2 O.sub.3 ; 20.40% Na.sub.2 O; 57.50% H.sub.2 O); 
7.4 g of sodium hydroxide pellets; 
57.2 g of HexPyrr (composition in weight %: 96.50% HexPyrr; 3.50% H.sub.2 
O) 
709 g of water. 
The mixture was prepared using the following method: 
A--solution of the sodium hydroxide and the sodium aluminate in water 
(approximately 200 g); 
B--solution of the HexPyrr in water (approximately 150 g); 
C--dispersion of the CAB-O-SIL in the remaining water. 
Solution A was added to dispersion C with stirring; solution B was then 
added. Stirring was continued until a homogeneous gel was obtained. The 
mixture obtained was then transferred to a stainless steel autoclave with 
a 1 liter capacity. The mixture was heated to a temperature of 160.degree. 
C. This temperature was maintained during the entire reaction period. The 
mixture was stirred using an inclined paddle stirrer. 
Samples of the reaction mixture were regularly removed and the progress of 
the reaction was followed by monitoring the pH. After 13 days at 
160.degree. C., the temperature of the reaction mixture was rapidly 
reduced to room temperature and the product was evacuated. The substance 
was then filtered; the solid product obtained was washed with 
demineralized water and dried for several hours at Analysis of the Si, Al 
and Na in the product was carried out using atomic emission spectroscopy. 
The following molar composition was determined: 
EQU 100 SiO.sub.2 ; 4.82 Al.sub.2 O.sub.3 ; 0.337 Na.sub.2 O. 
The dried solid product was analysed by powder X ray diffraction and 
identified as NU-88 zeolite. The diagram obtained agreed with the results 
shown in Table 1. The diffractogram is shown in FIG. 1 [with the intensity 
I (arbitrary units) up the ordinate and 2.theta. (Cu K alpha) along the 
abscissa]. 
The product obtained above was calcined in nitrogen for 24 hours at 
550.degree. C.; this step was immediately followed by a second calcining 
step in air at 450.degree. C., for 24 hours. 
The substance obtained was then left in contact with an aqueous 1 mole 
solution of ammonium chloride for 2 hours at room temperature using 50 ml 
of solution per gram of calcined solid product. The substance was then 
filtered, washed with deionized water and dried at 110.degree. C. This 
treatment was repeated three times. The substance was calcined in air for 
24 hours at 550.degree. C. The calcined product was analysed by X ray 
diffraction. The diffractogram obtained is shown in FIG. 2 [2.theta. (CuK 
alpha) along the abscissa and intensity I up the ordinate (arbitrary 
units)]. The X ray diffraction diagram was in agreement with Table 2. 
Atomic emission spectroscopic analysis of the Si, Al and Na in the product 
gave the following molar composition: 
EQU 100 SiO.sub.2 : 4.55 Al.sub.2 O.sub.3 : 0.009 Na.sub.2 O 
A hydrocracking catalyst support containing NU-88 zeolite produced as above 
was obtained as follows. 19.4 g of NU-88 zeolite was mixed with 80.6 g of 
a matrix composed of ultrafine tabular boehmite or alumina gel sold by 
Condea Chemie GmbH under the trade name SB3. This powder mixture was then 
mixed with an aqueous solution containing 66% nitric acid (7% by weight of 
acid per gram of dry gel) then mixed for 15 minutes. After mixing, the 
paste obtained was passed through a die with cylindrical orifices with a 
diameter of 1.4 mm. The extrudates were then dried overnight at 
120.degree. C. in air and calcined at 550.degree. C. in air. 
EXAMPLE 2: Preparation of Hydrocracking Catalysts Containing a NU-88 
Zeolite (in Accordance with the Invention) 
Extrudates of the support containing a NU-88 zeolite prepared in Example 1 
were dry impregnated with an aqueous solution of ammonium heptamolybdate 
and nickel nitrate, dried overnight at 120.degree. C. and finally calcined 
at 550.degree. C. in air. The oxide weight contents of catalyst CZ10 
obtained are shown in Table 2. 
The extrudates were dry impregnated with an aqueous solution of ammonium 
heptamolybdate, nickel nitrate and orthophosphoric acid, dried overnight 
at 120.degree. C. and finally calcined at 550.degree. C. in air. The oxide 
weight contents of catalyst CZ10P obtained are shown in Table 2. 
We then impregnated the CZ10P catalyst sample with an aqueous solution 
containing ammonium biborate and Rhodorsil EP1 silicone emulsion and 
obtained catalyst CZ10PBSi. The final oxide weight contents of the CZ10 
catalysts are shown in Table 2. 
TABLE 2 
__________________________________________________________________________ 
Characteristics of CZ10 catalysts 
Catalyst 
CZ10 
CZ10Nb 
CZ10P 
CZ10NbP 
CZ10PBSi 
CZ10NbPBSi 
__________________________________________________________________________ 
MoO.sub.3 
13.8 
12.9 13.3 12.3 12.8 11.9 
(wt %) 
Nb.sub.2 O.sub.5 0 6.4 0 6.6 0 6.6 
(wt %) 
NiO 3.1 2.9 3.0 2.8 2.9 2.7 
(wt %) 
P.sub.2 O.sub.5 0 0 4.65 4.3 4.5 4.2 
(wt %) 
B.sub.2 O.sub.3 0 0 0 0 1.5 1.4 
(wt %) 
SiO.sub.2 14.8 13.8 14.1 13.1 15.3 14.3 
(wt %) 
Complement 68.3 63.8 64.95 60.7 63.0 58.8 
to 100% 
mainly 
composed of 
Al.sub.2 O.sub.3 (wt 
%) 
__________________________________________________________________________ 
Electronic microprobe analysis of catalysts CZ10PBSi and CZ10NbPBSi (Table 
2) showed that the silicon added to the catalyst of the invention was 
mainly located on the matrix and was in the form of amorphous silica. 
EXAMPLE 3: Preparation of Hydrocracking Catalysts Containing a NU-88 
Zeolite and Niobium (in Accordance with the Invention) 
The catalysts of Example 3 above were impregnated using an aqueous solution 
of niobium oxalate Nb(HC.sub.2 O.sub.4).sub.5, oxalic acid and ammonium 
oxalate. The aqueous solution containing the niobium was prepared from 
1330 ml of water in which 33 g of oxalic acid, 37.2 g of ammonium oxalate 
and 92.3 g of niobium oxalate had been dissolved. This deposited about 5% 
by weight of Nb on the catalyst. The solution was prepared by first 
dissolving the mixture of oxalic acid and ammonium oxalate and when the 
solution was clear, heating the solution to 55.degree. C. and adding the 
niobium oxalate. Water was then added to obtain 1330 ml of solution. 
The catalysts of Example 3 were impregnated using the excess solution 
method. The 1330 ml of solution was brought into contact with 380 g of 
catalyst. After two hours, the extrudates were recovered. These were dried 
overnight at 120.degree. C. in a stream of dry air. The final oxide 
contents of catalysts CZ10Nb, CZ10NbP and CZ10NbPBSi obtained are shown in 
Table 2. 
EXAMPLE 4: Comparison of Catalysts for Partial Conversion Hydrocracking of 
a Vacuum Gas Oil 
The catalysts prepared in Examples 1 to 3 above were employed under 
moderate pressure hydrocracking conditions using a petroleum feed with the 
following principal characteristics: 
______________________________________ 
Density (20/4) 0.921 
Sulphur (weight %) 2.46 
Nitrogen (ppm by weight) 1130 
Simulated distillation 
Initial point 365.degree. C. 
10% point 430.degree. C. 
50% point 472.degree. C. 
90% point 504.degree. C. 
End point 539.degree. C. 
Pour point +39.degree. C. 
______________________________________ 
The catalytic test unit comprised two fixed bed reactors in upflow mode. 
The catalyst for the first hydrotreatment step of the process, HTH548 from 
Procatalyse, comprising a group VI element and a group VIII element 
deposited on alumina, was introduced into the first reactor, through which 
the feed passed first. A hydrocracking catalyst as described above was 
introduced into the second reactor, through which the feed passed last. 40 
ml of catalyst was introduced into each of the reactors. The two reactors 
operated at the same temperature and the same pressure. The operating 
conditions of the test unit were as follows: 
______________________________________ 
Total pressure 5 MPa 
Hydrotreatment catalyst 40 cm.sup.3 
Hydrocracking catalyst 40 cm.sup.3 
Temperature 400.degree. C. 
Hydrogen flow rate 20 l/h 
Feed flow rate 40 cm.sup.3 /h 
______________________________________ 
The two catalysts underwent in-situ sulphurisation before the reaction. It 
should be noted that any in-situ or ex-situ sulphurisation method is 
suitable. Once sulphurisation had been carried out, the feed described 
above could be transformed. 
The catalytic performances are expressed as the gross conversion at 
400.degree. C. (GC), the gross selectivity for middle distillates (GS) and 
the hydrodesulphuration (HDS) and hydrodenitrogenation (HDN) conversions. 
These catalytic performances were measured for the catalyst after a 
stabilisation period, generally of at least 48 hours, had passed. 
The gross conversion GC is taken to be: 
EQU GC=weight % of 380.degree. C..sup.minus of effluent. 
380.degree. C..sup.minus represents the fraction distilled at a temperature 
of 380.degree. C. or less. 
The gross selectivity GS for middle distillates is taken to be: 
EQU GS=100* weight of (150.degree. C.-380.degree. C.) fraction/weight of 
380.degree. C..sup.minus fraction of effluent. 
The hydrodesulphuration conversion HDS is taken to be: 
EQU HDS=(S.sub.initial -S.sub.effluent)/S.sub.initial 
*100=(24600-S.sub.effluent)/24600 * 100 
The hydrodenitrogenation conversion HDN is taken to be: 
EQU HDN=(N.sub.initial -N.sub.Effluent)/N.sub.initial * 
100=(1130-N.sub.effluent)/1130 * 100 
The following table shows the gross conversion GC at 400.degree. C., the 
gross selectivity GS, the hydrodesulphuration conversion HDS and the 
hydrodenitrogenation conversion HDN for the catalysts. 
TABLE 3 
______________________________________ 
Catalytic activities of catalysts for partial hydrocracking at 400.degree. 
C. 
GC GS HDS HDN 
(wt %) (%) (%) (%) 
______________________________________ 
CZ10 NiMo/NU-88 49.7 59.2 98.7 95.1 
CZ10Nb NiMoNb/NU-88 50.2 59.8 98.8 96.7 
CZ10P NiMoP/NU-88 49.7 60.3 99.3 96.2 
CZ10NbP NiMoNbP/NU-88 50.6 60.1 99.45 97.1 
CZ10PBSi NiMoPBSi/NU-88 50.9 59.4 99.5 98.4 
CZ10NbPBSi NiMoNbPBSi/NU-88 51.6 60.2 99.7 98.8 
______________________________________ 
The results of Table 3 show that adding niobium to NiMo, NiMoP, NiMoPBSi 
catalysts supported on supports containing alumina and a NU-88 zeolite 
improved the performances of the catalyst whatever the zeolite. The 
activities of catalysts containing NU-88 zeolite of the invention were 
higher, i.e., the conversions were higher for the same reaction 
temperature of 400.degree. C., than catalysts which were not in accordance 
with the invention (CZ10, CZ10P and CZ10PBSi). Catalysts of the invention 
containing niobium are thus of particular importance for partial 
hydrocracking of a vacuum distillate type feed containing nitrogen at 
medium hydrogen pressure. 
EXAMPLE 5: Comparison of NU-88 Based Catalysts for High Conversion 
Hydrocracking of a Vacuum Gas Oil 
The catalysts containing NU-88 zeolite and niobium prepared as described in 
Examples 1 to 3 were used under high conversion (60-100%) hydrocracking 
conditions. The petroleum feed was a hydrotreated vacuum distillate with 
the following principal characteristics: 
______________________________________ 
Density (20/4) 0.869 
Sulphur (ppm by weight) 502 
Nitrogen (ppm by weight) 10 
Simulated distillation 
Initial point 298.degree. C. 
10% point 369.degree. C. 
50% point 427.degree. C. 
90% point 481.degree. C. 
End point 538.degree. C. 
______________________________________ 
This feed had been obtained by hydrotreatment of a vacuum distillate using 
a HR360 catalyst from Procatalyse comprising a group VIB element and a 
group VIII element deposited on alumina. 
0.6% by weight of aniline and 2% by weight of dimethyldisulphide were added 
to the feed to simulate the partial pressures of H.sub.2 S and NH.sub.3 
present in the second hydrocracking step. The prepared feed was injected 
into the hydrocracking test unit which comprised one fixed bed reactor in 
upflow mode, into which 80 ml of catalyst had been introduced. The 
catalyst was sulphurised using a n-hexane/DMDS+ aniline mixture at 
320.degree. C. It should be noted that any in-situ or ex-situ 
sulphurisation method is suitable. Once sulphurisation had been carried 
out, the feed described above could be transformed. The operating 
conditions of the test unit were as follows: 
______________________________________ 
Total pressure 9 MPa 
Catalyst 80 cm.sup.3 
Temperature 360-420.degree. C. 
Hydrogen flow rate 80 l/h 
Feed flow rate 80 cm.sup.3 h 
______________________________________ 
The catalytic performances are expressed as the temperature at which a 
gross conversion of 70% is produced and by the gross selectivity for 
150-380.degree. C. middle distillates. These catalytic performances were 
measured for the catalyst after a stabilisation period, generally of at 
least 48 hours, had passed. 
The gross conversion GC is taken to be: 
EQU GC=weight % of 380.degree. C..sup.minus of effluent. 
The gross selectivity GS for middle distillates is taken to be: 
EQU GS=100* weight of (150.degree. C.-380.degree. C.) fraction/weight of 
380.degree. C..sup.minus fraction of effluent. 
The (27-150) gasoline yield (hereinafter Gyld) was equal to the weight % of 
compounds with a boiling point in the range 27.degree. C. to 150.degree. 
C. in the effluents. The jet fuel yield (kerosine, 150-250) (hereinafter 
Kyld) was equal to the weight % of compounds with a boiling point in the 
range 150.degree. C. to 250.degree. C. in the effluents. The (250-380) gas 
oil yield was equal to the weight % of compounds with a boiling point in 
the range 250.degree. C. to 380.degree. C. in the effluents. 
The reaction temperature was fixed so as to obtain a gross conversion GC of 
70% by weight. Table 5 below shows the reaction temperature and gross 
selectivity for the catalysts described in Table 2. 
Table 5 shows that using a catalyst of the invention containing NU-88 
zeolite and niobium leads to higher conversions (i.e., lower conversion 
temperatures for a given conversion of 70% by weight) than catalysts which 
are not in accordance with the invention containing no niobium. Further, 
the gasoline and kerosine yields of all of the catalysts containing a 
NU-88 zeolite and niobium of the invention were improved over those 
recorded for prior art catalysts containing no niobium. 
TABLE 5 
______________________________________ 
Catalytic activities of catalysts for high conversion (70%) hydrocracking 
Gasoline Kerosine 
yield yield 
T (.degree. C.) (wt %) (wt %) 
______________________________________ 
CZ10 NiMo/NU-88 373 37.4 12.0 
CZ10Nb NiMoNb/NU-88 371 38.2 11.4 
CZ10P NiMoP/NU-88 373 37.4 12.9 
CZ10NbP NiMoNbP/NU-88 371 38.4 12.2 
CZ10PBSi NiMoPBSi/NU-88 370 36.6 12.9 
CZ10NbPBSi NiMoNbPBSi/NU-88 368 37.9 12.4 
______________________________________