Molecular sieve abstract
The present invention relates to a process for the preparation
of a large-pore molecular sieve, comprising crystallizing the molecular
sieve from a starting mixture at a pH in the range of from 3 to
8 and recovering a large-pore molecular sieve, the said starting
mixture having a molar composition satisfying the following molar
ratio's: wherein n and m are the weighted average valences of R
and M respectively, M is an alkali- or alkaline earth metal, X is
a trivalent metal and Y is a tetravalent element, wherein R comprises
at least one main organic template R.sub.m having the formula R.sub.1
R.sub.2 R.sub.3 R.sub.4 Q.sup.+ wherein Q is nitrogen or phosphorus
and wherein at least one and at most three of R.sub.1 R.sub.2
R.sub.3 and R.sub.4 is an aryl or alkyl group having 6 to 36 carbon
atoms and each of the remainder of R.sub.1 R.sub.2 R.sub.3 and
R.sub.4 is selected from hydrogen and an alkyl group having 1 to
5 carbon atoms.
Molecular sieve claims
What is claimed is:
1. A process for the preparation of a large-pore molecular sieve
having in its calcined state an X-ray diffraction pattern with at
least one peak at a d-spacing of at least 1.8 nanometers, comprising
crystallizing the molecular sieve from a starting mixture at a pH
in the range of from 3 to 8 and recovering a large-pore molecular
sieve, the said starting mixture having a molar composition satisfying
the following molar ratios:
wherein n and m are the weighted average valences of R and M respectively,
M is an alkali- or alkaline earth metal, X is a trivalent metal
and Y is a tetravalent element, wherein R comprises at least one
main organic template R.sub.m having the formula R.sub.1 R.sub.2
R.sub.3 R.sub.4 Q.sup.+ wherein Q is nitrogen or phosphorus, wherein
at least one and at most three of R.sub.1 R.sub.2 R.sub.3 and
R.sub.4 is an aryl or alkyl group having 6 to 36 carbon atoms and
each of the remainder of R.sub.1 R.sub.2 R.sub.3 and R.sub.4 is
selected from hydrogen and an alkyl group having 1 to 5 carbon atoms,
and wherein the fluorine source is selected from the group consisting
of HF, NH.sub.4 F and mixtures thereof.
2. The process as claimed in claim 1 characterized in that the
starting mixture has a molar composition satisfying the following
molar ratios:
3. The process as claimed in claim 2 characterized in that the
starting mixture has a molar composition satisfying the following
molar ratio's:
4. The process as claimed in claim 1 wherein R further comprises
R.sub.a having the formula R.sub.5 R.sub.6 R.sub.7 R.sub.8 Q.sup.+
wherein Q is nitrogen or phosphorus and each of R.sub.5 R.sub.6
R.sub.7 and R.sub.8 is selected from hydrogen and an alkyl group
having 1 to 5 carbon atoms, wherein 2 alkyl groups can be interconnected
to form a cyclic compound.
5. The process as claimed in claim 1 wherein the starting mixture
further comprises an auxiliary organic compound R.sub.c selected
from the group of aromatic hydrocarbons and amines having 5 to 20
carbon atoms and halogen- and C.sub.1 -C.sub.14 alkyl-substituted
derivatives thereof, cyclic and polycyclic aliphatic hydrocarbons
and amines of 5 to 20 carbon atoms and halogen- and C.sub.1 -C.sub.14
alkyl-substituted derivatives thereof, straight and branched chain
aliphatic hydrocarbons and amines having 3 to 16 carbon atoms and
hydroxyl- or halogen-substituted derivatives thereof.
6. The process as claimed in claim 5 characterized in that the
molar ratio R.sub.c /YO.sub.2 ranges from about 0.05 to about 20.
7. The process as claimed in claim 1 characterized in that the
reaction temperature is in the range of from about 60.degree. C.
to 250.degree. C.
8. The process as claimed in claim 1 characterized in that the
crystallization time is in the range of from about 2 to about 336
hours.
9. The process as claimed in claim 1 characterized in that the
pH is in the range of from about 3 to about 7.5.
10. The process as claimed in claim 1 characterized in that X
is selected from the group consisting of Ga, Fe, B, Al and mixtures
thereof.
11. The process as claimed in claim 1 characterized in that Y
is selected from the group consisting of Ti, Zr, Si and mixtures
thereof.
Molecular sieve description
FIELD OF THE INVENTION
The present invention relates to a process for preparing a large
pore molecular sieve. In particular, the present invention relates
to a process for preparing a molecular sieve containing pores having
diameters of at least 1.3 nm.
BACKGROUND OF THE INVENTION
Such molecular sieves are known in the art. International Application
Publication No. WO 93/01884 (WO 93/01884) discloses a hydroprocessing
catalyst containing a support material comprising an ultra-large
pore crystalline material (molecular sieve) of high surface area
and porosity. The crystalline material exhibits after calcination
an X-ray diffraction pattern with at least one peak having a relative
intensity of 100 at a d-spacing greater than 1.8 nm and having a
benzene sorption capacity greater than 15 grams benzene per 100
grams of the material at 6.7 kPa and 25.degree. C.
The crystalline material is typically prepared by crystallization
from a starting mixture at strong basic conditions, that is a pH
in the range of from 9 to 14. In particular, if the starting mixture
does not contain bivalent or pentavalent species it is stated that
it is essential to maintain the pH within this range in three out
of four synthesis procedures disclosed in WO 93/01884.
The fourth synthesis procedure disclosed in WO 93/01884 should
be carried out at a pH of less than 12. In this fourth procedure
the same synthesis mixture is to be employed as disclosed with respect
to the third synthesis procedure. The lower limit of the pH range
which can be used in the fourth procedure is therefore about 9.
Beck et al. (J. Am. Chem Soc. 1992 Vol. 114 pages 10834-10843)
discuss the influence of organic templates on the structure and
properties of the crystalline material and propose two theoretical
models for formation of the crystalline material.
Monnier et al. (Science 1993 Vol. 261 pages 1299-1303) synthesized
the crystalline materials at a range of experimental conditions
and on the basis of the known experimental results developed a refined
model of the formation process which could explain the then known
experimental data and which could predict conditions needed for
the synthesis of desired structures. According to this publication
a pH of at least 9.5 seems essential in order to be able to directly
synthesize the crystalline materials. According to Monnier et al.
the crystal structure of a monoclinic, layered crystalline material
produced in the initial stages of the synthesis process at a pH
of at least 9.5 can be altered to a hexagonal crystalline material
by a hydrothermal treatment at 373 K at a pH of 7 over 10 days.
It has now been found possible to directly synthesize crystalline
material, hereinafter called molecular sieves, as described in WO
93/01884 under acidic, neutral or weak basic conditions, by using
starting mixtures containing a fluorine source.
SUMMARY OF THE INVENTION
The present invention therefore relates to a process for the preparation
of a large-pore molecular sieve, comprising crystallizing the molecular
sieve from a starting mixture at a pH in the range of from 3 to
8 and recovering a large-pore molecular sieve, the said starting
mixture having a molar composition satisfying the following molar
ratios:
wherein n and m are the weighted average valences of R and M respectively,
M is an alkali- or alkaline earth metal, X is a trivalent metal
and Y is a tetravalent element, wherein R comprises at least one
main organic template R.sub.m having the formula R.sub.1 R.sub.2
R.sub.3 R.sub.4 Q.sup.+ wherein Q is nitrogen or phosphorus and
wherein at least one and at most three of R.sub.1 R.sub.2 R.sub.3
and R.sub.4 is an aryl or alkyl group having 6 to 36 carbon atoms
and each of the remainder of R.sub.1 R.sub.2 R.sub.3 and R.sub.4
is selected from hydrogen and an alkyl group having 1 to 5 carbon
atoms. The compound from which the above ammonium or phosphonium
ion is derived may be, for example, the hydroxide, halide, silicate
or mixtures thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
It will be appreciated that in the starting mixture electroneutrality
is preserved. Accordingly, both R.sub.2/n O and M.sub.2/n O as well
as any other ingredient of the starting mixture may be present in
the starting mixture in an ionic form.
A disadvantage of the preparation methods under strong basic conditions
is that the starting mixture does not contain sufficient H.sup.+
to act as counter-ion for AlO.sub.2 - in the molecular sieve crystal
lattice. Thus, the starting mixture normally contains alkali- or
alkaline earth metal compounds to act as counter-ion.
Alkali- or alkaline earth metal compounds-containing molecular
sieves are usually not desired as such molecular sieves are hardly
acidic, if at all. Thus, normally the alkali- or alkaline earth
metal compounds-containing molecular sieves are first calcined or
extracted to remove organic template(s), then ion-exchanged with
an aqueous ammonium solution to remove alkali- or alkaline earth
metal compounds from ion-exchange sites of the molecular sieve,
and finally calcined to convert NH.sub.4.sup.+ in ion-exchange sites
to H+, while producing NH.sub.3 containing gas.
It is known in zeolite synthesis to synthesize zeolitic materials
in the presence of NH.sub.4.sup.+ rather than alkali- or alkaline
earth metals. However, at the high pH employed in the experiments
described in WO 93/01884 NH4+ is unstable and converts to NH3.
Accordingly, at such high pH NH.sub.4.sup.+ cannot normally be used
instead of alkali- and/or alkaline earth metal compounds.
In theory it is feasible to synthesize crystalline materials at
high pH in the absence of any added counter-ion apart from ionic
forms of the organic template(s). However, at strong basic conditions
this requires excessive amounts of expensive organic template(s).
It would be particularly desirable if large-pore molecular sieves
could be produced from a starting mixture containing substantially
no, preferably no, alkali- or alkaline earth metal compound(s).
It has now been found possible to synthesize the crystalline material
of the present invention in the absence of alkali- or alkaline-earth
metal compounds, and in the presence of fluorine, in accordance
with the process of the present invention.
Accordingly, in a preferred embodiment the present invention relates
to a process for preparing a large-pore molecular sieve comprising
crystallizing the molecular sieve from a starting mixture having
a molar composition satisfying the following molar ratio's:
More preferably the starting mixture has a molar composition satisfying
the following molar ratio's:
Preferably, R comprises an additional organic template R.sub.a
in the form of an ammonium or phosphonium ion of the above formula
(R.sub.1 R.sub.2 R.sub.3 R.sub.4 Q.sup.+) but wherein each R.sub.1
R.sub.2 R.sub.3 and R.sub.4 is selected from hydrogen and an alkyl
group having 1 to 5 carbon atoms, and wherein 2 alkyl groups can
be interconnected to form a cyclic compound. The compound from which
the additional organic template ion is derived may be, for example,
the hydroxide, halide, silicate or mixtures thereof.
The molar ratio additional organic template R.sub.a /main organic
template R.sub.m may typically range from 0.01 to 100. The total
of organic template R being used in the starting mixture should
however remain within the ranges described herein. Preferably, the
R.sub.2/n O/(YO.sub.2 +X.sub.2 O.sub.3) molar ratio in the starting
mixture is at least 0.1 if R comprises both R.sub.m and R.sub.a.
In order to vary the pore size of the molecular sieve, the starting
mixture may comprise an auxiliary organic compound R.sub.c in addition
to the organic templates R, that is R.sub.m +R.sub.a, described
hereinabove. Typically, this organic compound is selected from the
group of aromatic hydrocarbons and amines having 5 to 20 carbon
atoms and halogen- and C.sub.1 -C.sub.14 alkyl-substituted derivatives
thereof; or cyclic and polycyclic aliphatic hydrocarbons and amines
of 5 to 20 carbon atoms and halogen- and C.sub.1 -C.sub.14 alkyl-substituted
derivatives thereof; or straight and branched chain aliphatic hydrocarbons
and amines having 3 to 16 carbon atoms and hydroxyl or halogen-substituted
derivatives thereof.
In the auxiliary organic compounds the halogen derivative is preferably
a bromine, fluorine or chlorine derivative.
The molar ratio auxiliary organic compound R.sub.c /(R.sub.m +R.sub.a)
may range from 0.02 to 100 preferably from 0.05 to 35. It is to
be understood that for the purposes of this specification the auxiliary
organic compound R.sub.c is not comprised within the term "organic
template(s)", "R" or "R.sub.2/n O" as used
herein. If present in a starting mixture, the molar ratio R.sub.c
/YO.sub.2 typically ranges from 0.05 to 20 preferably from 0.1
to 10.
Typically, the synthesis is carried out at a crystallization time
in the range of from 2 to 336 hours, preferably at a crystallization
time in the range of from 12 to 240 hours, more preferably in the
range of from 24 to 120 hours.
Typically a reaction temperature is employed in the range of from
60.degree. to 250.degree. C., preferably in the range of from 90.degree.
to 200.degree. C.
Preferably, the synthesis is carried out at a pH in the range of
from 3 to 7.5 more preferably in the range of from 4 to 7.
X is preferably chosen from Ga, Fe, B and/or Al, more preferably
Al. Examples of suitable sources of X include any oxides, hydroxides,
sulfates, alkoxides and/or halides of X.
Y is preferably chosen from Ti, Zr and/or Si, more preferably Si.
Examples of suitable sources of Y include any oxides, alkoxides
and/or halides of Y as well as quaternary ammonium compounds such
as tetramethylammonium silicate, and tetraethylorthosilicate.
Typically, any source of fluorine ions in the starting mixture
can be used in the process of the present invention. Particularly
suitable sources include HF and NH.sub.4 F. For reasons of safety
NH.sub.4 F is preferably used.
It is to be understood that the amount of NH.sub.4.sup.+ in the
starting mixture is not critical and is in fact determined by the
amount of ammonium salts used in preparation of the starting mixture.
NH4+ may even be absent from the starting mixture as in the synthesis
according to the present invention ionic forms of the organic template(s)
used and any auxiliary organic compound may act as counter-ion in
the crystal lattice of the crystalline molecular sieve.
The organic template(s) and any auxiliary organic compound(s) may
be removed from the large-pore crystalline molecular sieve according
to the present invention by calcining the molecular sieve at a temperature
in the range of from 350.degree. to 600.degree. C. for 1 to 24 hours.
Alternatively, R, that is the organic template(s) Rm and optionally
R.sub.a, and any R.sub.c, that is the auxiliary organic compound(s),
may be removed from the large-pore crystalline molecular sieve according
to the present invention by contacting the molecular sieve with
a polar solvent capable of extracting R and any R.sub.c from the
molecular sieve. A suitable method has been disclosed in U.S. Pat.
No. 5143879.
In yet another aspect the present invention relates to a large-pore
crystalline molecular sieve having in its calcined state an X-ray
diffraction pattern with at least one peak at a d-spacing of at
least 1.8 nm, a benzene sorption capacity of more than 15 grams
benzene per 100 grams of the crystalline molecular sieve at 6.7
kPa and 25.degree. C., and a chemical composition which can be expressed
as follows:
Ways to determine the benzene sorption capacity are known to those
skilled in the art. Suitable techniques have been described in WO
93/01884.
Preferably, the crystalline molecular sieve has the following chemical
composition:
In a most preferred embodiment X is Al and Y is Si.
Typically, in the X-ray diffraction pattern of the crystalline
molecular sieve, the relative intensity of the strongest peak at
a d-spacing of at least 1.8 nm is 100. Preferably, the X-ray diffraction
pattern exhibits no peaks at d-spacings less than 1.0 nm having
a relative intensity of more than 20%, more preferably more than
10%, of the strongest peak.
Preferably, the calcined crystalline molecular sieve has an X-ray
diffraction pattern in which a d-spacing of at least 1.8 nm can
be indexed as d.sub.100. Ways to index d-spacings in X-ray diffraction
patterns are known to those skilled in the art. A suitable method
is described in WO 93/01884.
Preferably, the crystalline molecular sieve has a hexagonal arrangement
of uniformly-sized pores having diameters of at least 1.3 nm, as
defined in WO 93/01884 and WO 91/11390.
In another aspect, the present invention relates to the use of
a crystalline molecular sieve according to the present invention
as described hereinbefore, as a catalyst, catalyst carrier, adsorbent
or as component in a washing composition. Preferably the crystalline
molecular sieve is used in its R-free form. It is to be understood
that the crystalline molecular sieve may be composited with a matrix
material for example when used as catalyst or catalyst carrier for
certain applications. Examples of suitable matrix materials have
been described in WO 93/01884. Further, it will be appreciated that
when the crystalline molecular sieve is used as catalyst or catalyst
carrier, the finished catalyst may comprise (catalytically active)
metals, such as those from Group VIII or VIB from the Periodic Table
of the Elements. In a preferred embodiment, the crystalline molecular
sieve in combination with a metal having hydrogenation/- dehydrogenation
activity, is used as a hydroprocessing catalyst for hydroprocessing
of mineral or synthetic oil feedstocks.
The term hydroprocessing as used herein includes hydrocracking,
hydrotreating, hydrofinishing, hydroisomerization, hydrodesulfurization,
and hydrodenitrogenation.
In a particular preferred embodiment, the crystalline molecular
sieve is used in a hydrocracking and/or hydroisomerization process
to produce lubricating base oils from flashed distillates and/or
waxy feedstocks, such as slack wax.
The invention will now be illustrated further with reference to
the following Examples. The Examples are given for illustrative
purposes only and should not be construed as in any way limiting
the invention to a scope which is narrower than the present claims.
EXAMPLES
Example I
A synthesis mixture was prepared by admixing colloidal acid-stabilized
silica commercially available from Nalco, water, aqueous NH.sub.4
F solution, and as organic templates cetyltrimethylammoniumchloride
(CTMACl) and trimethylammoniumchloride (TMACl). The synthesis mixture
had the following molar composition:
The synthesis mixture had a pH of 7. The mixture was heated for
24 hours to 107.degree. C. in a teflon-lined autoclave under autogenous
pressure. After washing and filtering a crystalline material was
obtained having a X-ray diffraction pattern in which the largest
d-spacing amounted to 5.4 nm.
Example II
The as-synthesized crystalline molecular sieve obtained in the
experiment described in Example I was subjected to a calcination
treatment in air at 540.degree. C. for 10 hours The calcined crystalline
material had an X-ray diffraction pattern in which the largest d-spacing
amounted to 4.9 nm.
Example III
The experiment described in Example I was repeated, but dodecyltrimethylammoniumbromide
(DTMABr) was used instead of cetyltrimethylammoniumchloride, in
the same molar amount. After washing and filtering a crystalline
material was obtained having a X-ray diffraction pattern in which
the largest d-spacing amounted to 4.3 nm.
Example IV
A synthesis mixture was prepared by admixing colloidal acid-stabilized
silica commercially available from Nalco, water, aqueous NH.sub.4
F solution, and as organic templates cetyltrimethylammoniumbromide
(CTMABr) and trimethylammoniumchloride (TMACl). The synthesis mixture
had the following molar composition:
The mixture was heated for 100 hours at 108.degree. C. in a teflon-lined
autoclave under autogenous pressure. After washing and filtering
a crystalline material was obtained having a X-ray diffraction pattern
in which the largest d-spacing amounted to 5.7 nm.
Example V
A synthesis mixture was prepared by admixing colloidal acid-stabilized
silica commercially available from Nalco, water, aqueous NH.sub.4
F solution, cetyltrimethylammoniumbromide (CTMABr), trimethylammoniumchloride
(TMACl) and aluminumchloride (AlCl.sub.3.6H.sub.2 O). The synthesis
mixture had the following molar composition:
The mixture was heated for 24 hours at 106.degree. C. in a teflon-lined
autoclave under autogenous pressure. After washing and filtering
a crystalline material was obtained having a X-ray diffraction pattern
in which the largest d-spacing amounted to 6.5 nm.
Example VI
A synthesis mixture was prepared by admixing colloidal acid-stabilized
silica commercially available from Nalco, water, aqueous NH.sub.4
F solution, dodecyltrimethylammoniumbromide (DTMABr), triethylammoniumchloride
(TEACl) and aluminumchloride (AlCl.sub.3.6H.sub.2 O). The synthesis
mixture had the following molar composition:
The mixture was heated for 75 hours at 108.degree. C. in a teflon-lined
autoclave under autogenous pressure. After washing and filtering
a crystalline material was obtained having a X-ray diffraction pattern
in which the largest d-spacing amounted to 5.1 nm.
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