Molecular sieve abstract
An improved catalyst composition for isomerizing xylene containing
a minor amount of ethylbenzene comprising a HAMS-1B crystalline
borosilicate molecular sieve incorporated into an inorganic matrix
impregnated with a small amount of a phosphorus compound. The catalyst
composition when contacted with an ethylbenzene containing xylene
under isomerization conditions results in a greater yield of paraxylene
and a conversion of ethylbenzene to more useful products.
Molecular sieve claims
What is claimed is:
1. A process for isomerizing a xylene feed containing a minor amount
of ethylbenzene comprising contacting said xylene with a catalyst
composition comprising a HAMS- 1B crystalline borosilicate molecular
sieve incorporated into an inorganic matrix, said composition impregnated
with a suitable phosphorus compound and subsequently heated to substantially
convert said compound to the oxide form.
2. The process of claim 1 wherein said phosphorus compound is ammonium
hydrogen phosphate, ammonium dihydrogen phosphate, triethylphosphite,
or phosphoric acid.
3. The process of claim 2 wherein said catalyst composition contains
between about 0.5 and about 25% phosphorus by weight.
4. The process of claim 2 wherein said catalyst composition contains
between about 1 and about 15% by weight phosphorus.
5. The process of claim 3 wherein said HAMS-1B molecular sieve
comprises from about 20 to about 80 wt. % incorporated into an alumina,
silica, or silica-alumina matrix.
6. The process of claim 4 wherein said HAMS-1B molecular sieve
comprises from about 20 to about 80 wt. % incorporated into an alumina,
silica, or silica-alumina matrix.
Molecular sieve description
BACKGROUND OF THE INVENTION
This invention relates to improved AMS-1B crystalline molecular
sieve-based catalyst compositions, and particularly, to the use
of such compositions having improved ability to selectively isomerize
xylene feeds.
In U.S. Pat. No. 4532226 a ZSM-5 aluminosilicate zeolite catalyst
modified by P and Cr, Mo, or W and used to selectively catalyze
formation of the 14-diakyl isomer during conversion of aromatic
compounds is described. U.S. Pat. No. 4518703 teaches a P modified
silica polymorph-based catalyst for the methylation of toluene.
In U.S. Pat. Nos. 4504690 4128592 and 4086287 is taught modifying
a ZSM-5 aluminosilicate zeolite catalyst with P, Mg or P/Mg oxides
to obtain high proportions of the 14-dialkyl isomer. Phosphorus
modification of a ZSM-5 zeolite catalyst for the alkylation of toluene
to form a higher proportion of p-xylene is shown in J. Appl. Polymer
Sci. 36 209 (1981) as are P or Mg modified ZSM-5 zeolite catalysts
for the disproportionation of toluene. Selective para-alkylation
using P modified ZSM-5 zeolite catalysts is again described in J.
Cat. 67 159 (1981). Conversion of olefins over the same type of
catalyst is shown in J. Cat. 61 155 (1980). Disproportionation
of toluene to produce benzene and xylenes over P/Mg modified crystalline
aluminosilicate zeolite catalysts is described in U.S. Pat. No.
4137195. Alkylation or disproportionation of certain monosubstituted
benzene compounds to achieve nearly 100% selectivity to para-disubstituted
derivatives over phosphorus compound-modified ZSM-5 aluminosilicate
zeolite catalysts is reported in J. Am. Chem. Soc. 101 6783 (1979).
Use of Mg compounds alone or in combination with P compounds to
modify a ZSM-5 aluminosilicate of zeolite catalyst is described
in U.S. Pat. No. 4049573 and the modified catalyst is used for
converting alcohols and ethers to hydrocarbons. Again, magnesium
is used to modify ZSM-5 zeolite catalysts in U.S. Pat. No. 4002698
which catalysts can be used for the selective production of p-xylene
from charge stocks of toluene and a C.sub.3 -C.sub.10 olefin; P
modified catalysts for the methylation of toluene are also described.
Phosphorus modified ZSM-5 aluminosilicate zeolite catalysts are
again described in U.S. Pat. No. 3972832 and described as useful
for the conversion of aliphatics to various products.
Catalyst compositions, generally useful for hydrocarbon conversion,
based upon AMS-1B crystalline borosilicate molecular sieve have
been described in U.S. Pat. Nos. 4268420 4269813 4285919
and Published European Application No. 68796.
As described in the references in the paragraph above, catalyst
compositions typically are formed by incorporating an AMS-1B crystalline
borosilicate molecular sieve material into a matrix such as alumina,
silica or silica-alumina to produce a catalyst formulation. In one
method of making AMS-1B crystalline borosilicate, sieve is formed
by crystallizing sources for silicon oxide and boron oxide with
sodium hydroxide and an organic compound. After crystallization,
the resulting sodium form is ion exchanged with an ammonium compound
and calcined to yield the hydrogen form of AMS-1B. In another more
preferred method, AMS-1B crystalline borosilicate is crystallized
in the hydrogen form from a mixture containing a diamine in place
of a metal hydroxide. AMS-1B borosilicates in hydrogen form are
designated HAMS-1B. Typically, the hydrogen form sieve is gelled
with an alumina sol, dried and calcined to yield a catalyst composition.
SUMMARY OF THE INVENTION
An improved catalyst composition having superior xylene isomerization
properties and a process for the use of such compositions which
improves conversion of the ethylbenzene in ethylbenzene-containing
xylene streams to more useful products and improves paraxylene production,
comprising a HAMS-1B crystalline borosilicate molecular sieve incorporated
into a matrix which has been impregnated with a small amount of
a phosphorus compound and its use for isomerizing an ethylbenzene-containing
xylene.
DETAILED DESCRIPTION OF THE INVENTION
The catalyst composition of this invention comprises an AMS-1B
crystalline borosilicate molecular sieve incorporated into a matrix
and impregnated with a solution containing a suitable phosphorus
salt, which impregnated catalyst composition is then dried and calcined.
Described also is a process for using these impregnated catalyst
compositions for the isomerization of a xylene which contains a
minor amount of ethylbenzene to produce larger yields of paraxylene
and more useful ethylbenzene reaction products.
The form of the AMS-1B crystalline borosilicate molecular sieve
which is incorporated with the inorganic matrix is the hydrogen
form, i.e., HAMS-1B. This catalyst composition is then impregnated
with a phosphorus compound as set forth below.
Phosphorus can be incorporated into such catalyst compositions
substantially in the form of phosphorus oxide in an amount from
about 0.5% to about 25% phosphorus by weight, preferably about 1%
to about 15% by weight phosphorus. Such incorporation can be readily
effected by contacting the catalyst composition with a solution
of a suitable phosphorus compound, followed by removal of the solvent
by drying and finally calcining the dried mass to convert the phosphorus
in the composition substantially to its oxide form.
Preferred phosphorus-containing compounds include diphenyl phosphine
chloride, trimethylphosphite, phosphorus trichloride, phosphoric
acid, phenyl phosphine oxychloride, trimethylphosphate, diphenyl
phosphinous acid, diphenyl phosphinic acid, diethylchlorothiophosphate,
methyl acid phosphate and other alcohol-P.sub.2 O.sub.5 reaction
products. Particularly preferred are phosphoric acid, triethylphosphite
and ammonium phosphates, including ammonium hydrogen phosphate,
(NH.sub.4).sub.2 HPO.sub.4 and ammonium dihydrogen phosphate, NH.sub.4
H.sub.2 PO.sub.4.
Solvents for use in the impregnation step which can be by means
of incipient impregnation or otherwise are polar or non-polar solvents
including water and organic solvents. More preferably, they include
water and organic solvents such as hydrocarbons and alcohols. Importantly,
the solvent should not react with the catalyst compositions in a
way destructive of their catalytic capability.
The temperature used in the impregnation step is generally that
required to air evaporate the solvent or less, i.e., up to about
150.degree. C. High temperatures during the solvent removal step,
i.e., drying, are generally to be avoided.
Calcination is generally conducted in the presence of air at a
temperature of between about 350.degree. C. and about 650.degree.
C. Temperatures from about 400.degree. C. up to about 600.degree.
C. are preferred. Such calcination is generally carried out for
3 to 10 hours but may be extended to 24 hours or longer. Care should
be taken to avoid catalyst composition degradation during calcination.
After calcination the phosphorus is substantially in the oxide form.
The catalyst compositions used in this invention are based on AMS-1B
crystalline borosilicate molecular sieve, which is described in
U.S. Pat. Nos. 4268420 4269813 and 4285919 and Published
European Patent Application No. 68796 all incorporated herein
by reference. AMS-1B crystalline borosilicate generally can be characterized
by the X-ray pattern listed in Table A and by the composition formula:
wherein M is at least one cation, n is the oxidation state of the
cation, y is between 4 and about 600 and z is between 0 and about
160.
TABLE A ______________________________________ d-Spacing .ANG.
(1) Assigned Strength (2) ______________________________________
11.2 .+-. 0.2 .sup. W-VS 10.0 .+-. 0.2 .sup. W-MS 5.97 .+-. 0.07
W-M 3.82 .+-. 0.05 VS 3.70 .+-. 0.05 MS 3.62 .+-. 0.05 M-MS 2.97
.+-. 0.02 W-M 1.99 .+-. 0.02 VW-M.sup. ______________________________________
(1) Copper K alpha radiation (2) VW = very weak; W = weak; M = medium;
MS = medium strong; VS = very strong
The AMS-1B borosilicate molecular sieve useful in this invention
can be prepared by crystallizing an aqueous mixture, at a controlled
pH, of sources for cations, an oxide of boron, an oxide of silicon,
and an organic template compound.
Typically, the mol ratios of the various reactants can be varied
to produce the crystalline borosilicates of this invention. Specifically,
the mol ratios of the initial reactant concentrations are indicated
below:
______________________________________ Most Broad Preferred Preferred
______________________________________ SiO.sub.2 /B.sub.2 O.sub.3
5-400 10-150 10-80 R.sub.2 O.sup.+ /[R.sub.2 O.sup.+ + M.sub.2/n
O] 0.1-1.0 0.2-0.97 0.3-0.97 OH.sup.- /SiO.sub.2 0.01-11 0.1-2 0.1-1
H.sub.2 O/OH.sup.-2 10-4000 10-500 10-500 ______________________________________
wherein R is an organic compound and M is at least one cation having
the oxidation state n, such as an alkali or an alkaline earth metal
cation or hydrogen. By regulation of the quantity of boron (represented
as B.sub.2 O.sub.3) in the reaction mixture, it is possible to vary
the SiO.sub.2 /B.sub.2 O.sub.3 molar ratio in the final product.
More specifically, the material useful in the present invention
is prepared by mixing a base, a boron oxide source, and an organic
template compound in water (preferably distilled or deionized).
The order of addition usually is not critical, although a typical
procedure is to dissolve base and boric acid in water and then add
the template compound. Generally, the silicon oxide compound is
added with intensive mixing such as that performed in a Waring Blendor
and the resulting slurry is transferred to a closed crystallization
vessel for a suitable time. After crystallization, the resulting
crystalline product can be filtered, washed with water, dried, and
calcined.
During preparation, acidic conditions should be avoided. When alkali
metal hydroxides are used, the values of the ratio of OH.sup.- /SiO.sub.2
shown above should furnish a pH of the system that broadly falls
within the range of about 9 to about 13.5. Advantageously, the pH
of the reaction system falls within the range of about 10.5 to about
11.5 and most preferably between about 10.8 and about 11.2.
Examples of materials affording silicon oxide useful in this invention
include silicic acid, sodium silicate, tetraalkyl silicates and
Ludox, a stabilized polymer of silicic acid manufactured by E. I.
DuPont de Nemours & Co. Typically, the oxide of boron source
is boric acid although equivalent species can be used such as sodium
borate and other boron-containing compounds.
Cations useful in formation of AMS-1B crystalline borosilicate
include alkali metal and alkaline earth metal cations such as sodium,
potassium, lithium, calcium and magnesium. Ammonium cations may
be used alone or in conjunction with such metal cations. Since basic
conditions are required for crystallization of the molecular sieve
of this invention, the source of such cation usually is a hydroxide
such as sodium hydroxide. Alternatively, AMS-1B can be prepared
directly in the hydrogen form by replacing such metal cation hydroxides
with an organic base such as ethylenediamine as described in Published
European Application No. 68796.
Organic templates useful in preparing AMS-1B crystalline borosilicate
include alkylammonium cations or precursors thereof such as tetraalkylammonium
compounds, especially tetra-n-propylammonium compounds. A useful
organic template is tetra-n-propylammonium bromide. Diamines, such
as hexamethylenediamine, can be used.
In a more detailed description of a typical preparation of this
invention, suitable quantities of sodium hydroxide and boric acid
(H.sub.3 BO.sub.3) are dissolved in distilled or deionized water
followed by addition of the organic template. The pH may be adjusted
between about 11.0.+-.0.2 using a compatible acid or base such as
sodium bisulfate or sodium hydroxide. After sufficient quantities
of a silica source such as a silicic acid polymer (Ludox) are added
with intensive mixing, preferably the pH is again checked and adjusted
to a range of about 11.0.+-.0.2.
Alternatively, AMS-1B crystalline borosilicate molecular sieve
can be prepared by crystallizing a mixture of sources for an oxide
of silicon, an oxide of boron, an alkyl ammonium compound and ethylenediamine
such that the initial reactant molar ratios of water to silica range
from about 5 to about 25 preferably about 5 to about 20 and most
preferably from about 10 to about 15. In addition, preferable molar
ratios for initial reactant silica to oxide of boron range from
about 4 to about 150 more preferably from about 5 to about 80 and
most preferably from about 5 to about 20. The molar ratio of ethylenediamine
to silicon oxide should be about above about 0.05 typically below
5 preferably between about 0.1 and about 1.0 and most preferably
between about 0.2 and 0.5. The molar ratio of alkylammonium compound,
such as tetra-n-propylammonium bromide, to silicon oxide can range
from 0 to about 1 or above, typically above about 0.005 preferably
about 0.01 to about 0.1 more preferably about 0.01 to about 0.08
and, most preferably, about 0.02 to about 0.05.
The resulting slurry is transferred to a closed crystallization
vessel and reacted usually at a pressure at least the vapor pressure
of water for a time sufficient to permit crystallization which usually
is about 0.25 to about 20 days, typically is about one to about
ten days and preferably is about one to about seven days, at a temperature
ranging from about 100.degree. C. to about 250.degree. C., preferably
about 125.degree. C. to about 200.degree. C. The crystallizing material
can be stirred or agitated as in a rocker bomb. Preferably, the
crystallization temperature is maintained below the decomposition
temperature of the organic template compound. Especially preferred
conditions are crystallizing at about 165.degree. C. for about five
to about seven days. Samples of material can be removed during crystallization
to check the degree of crystallization and determine the optimum
crystallization time.
The crystalline material formed can be separated and recovered
by well-known means such as filtration with aqueous washing. This
material can be mildly dried for anywhere from a few hours to a
few days at varying temperatures, typically about 50.degree.-225.degree.
C., to form a dry cake which can then be crushed to a powder or
to small particles and extruded, pelletized, or made into forms
suitable for its intended use. Typically, materials prepared after
mild drying contain the organic template compound and water of hydration
within the solid mass and a subsequent activation or calcination
procedure is necessary, if it is desired to remove this material
from the final product. Typically, mildly dried product is calcined
at temperatures ranging from about 260.degree. C. to about 850.degree.
C. and preferably about 425.degree. C. to about 600.degree. C. Extreme
calcination temperatures or prolonged crystallization times may
prove detrimental to the crystal structure or may totally destroy
it. Generally, there is no need to raise the calcination temperature
beyond about 600.degree. C. in order to remove organic material
from the originally formed crystalline material. Typically, the
molecular sieve material is dried in a forced draft oven at 165.degree.
C. for about 16 hours and is then calcined in air in a manner such
that the temperature rise does not exceed 125.degree. C. per hour
until a temperature of about 540.degree. C. is reached. Calcination
at this temperature usually is continued for about 4 to 16 hours.
A catalytically active material can be placed onto the borosilicate
structure, either before or after incorporation into a matrix, by
ion exchange, impregnation, a combination thereof, or other suitable
contact means. Before placing a catalytically active metal ion or
compound on the borosilicate structure, the borosilicate should
be in the hydrogen form. If the sieve was prepared using a metal
hydroxide, such as sodium hydroxide, the hydrogen form typically
is produced by exchange one or more times with ammonium ion, typically
using ammonium acetate, followed by drying and calcination as described
above.
The original cation in the AMS-1B crystalline borosilicate can
be replaced all or in part by ion exchange with other cations including
other metal ions and their amine complexes, alkylammonium ions,
ammonium ions, hydrogen ions, and mixtures thereof. Preferred replacing
cations are those which render the crystalline borosilicate catalytically
active, especially for hydrocarbon conversion. Typical catalytically
active ions include hydrogen, metal ions of Groups IB, IIA, IIB,
IIIA, VB, VIB and VIII, and of manganese, vanadium, chromium uranium,
and rare earth elements.
Also, water soluble salts of catalytically active materials can
be impregnated onto the crystalline borosilicate of this invention.
Such catalytically active materials include metals of Groups IB,
IIA, IIB, IIIA, IIIB, IVB, VB, VIB, VIIB, and VIII, and rare earth
elements.
Examples of catalytically active elements include ruthenium, rhodium,
iron, cobalt, and nickel. Mixtures of elements can be used. Other
catalytic materials include ions and compounds of aluminum, lanthanum,
molybdenum, tungsten, and noble metals such as ruthenium, osmium,
rhodium, iridium, palladium, and platinum. Other additional catalytic
materials can be ions and compounds of scandium, yttrium, titanium,
zirconium, hafnium, vanadium, niobium, tantalum, chromium, cerium,
manganese, cobalt, iron, zinc, and cadmium. Specific combinations
of non-noble metals of Group VIII and other catalytic materials
include ions or compounds of nickel and osmium, nickel and lanthanum,
nickel and palladium, nickel and iridium, nickel and molybdenum,
and nickel and tungsten.
Ion exchange and impregnation techniques are well-known in the
art. Typically, an aqueous solution of a cationic species is exchanged
one or more times at about 25.degree. C. to about 100.degree. C.
A hydrocarbon-soluble metal compound such as a metal carbonyl also
can be used to place a catalytically active material. Impregnation
of a catalytically active compound on the borosilicate or on a composition
comprising the crystalline borosilicate suspended in and distributed
throughout a matrix of a support material, such as porous refractory
inorganic oxide such as alumina, often results in a suitable catalytic
composition. A combination of ion exchange and impregnation can
be used. Presence of sodium ion in a composition usually is detrimental
to catalytic activity.
The amount of catalytically active material placed on the AMS-1B
borosilicate can vary from about 0.01 weight percent to about 30
weight percent, typically from about 0.05 to about 25 weight percent,
depending on the process use intended. The optimum amount can be
determined easily by routine experimentation.
The AMS-1B crystalline borosilicate useful in this invention is
admixed with or incorporated within various binders or matrix materials
depending upon the intended process use. The crystalline borosilicate
can be combined with active or inactive materials, synthetic or
naturally-occurring zeolites, as well as inorganic or organic materials
which would be useful for binding the borosilicate. Well-known materials
include silica, silica-alumina, alumina, magnesia, titania, zirconia,
alumina sols, hydrated aluminas, clays such as bentonite or kaolin,
or other binders well-known in the art. Typically, the borosilicate
is incorporated within a matrix material by blending with a sol
of the matrix material and gelling the resulting mixture. Also,
solid particles of the borosilicate and matrix material can be physically
admixed. Typically, such borosilicate compositions can be pelletized
or extruded into useful shapes. The crystalline borosilicate content
can vary anywhere from a few up to 100 wt. % of the total composition.
Catalytic compositions can contain about 0.1 wt. % to about 100
wt. % crystalline borosilicate material and preferably contain about
10 wt. % to about 95 wt. % of such material and most preferably
contain about 20 wt. % to about 80 wt. % of such material.
Catalyst compositions impregnated with a phosphorus compound according
to this invention can be in powder form or already in extrudate
form.
The xylene feed to the isomerization stage containing the catalyst
compositions of the instant invention may be a mixture of ortho,
para, and metaxylene, or any of the isomers individually. The feed
preferably contains between about 5% and about 25% by weight of
ethylbenzene, more preferably about 8% to about 20% ethylbenzene
and, most preferably, about 10% to about 15% ethylbenzene. Isomerization
conditions can vary considerably but preferably range between a
pressure of about 10 psig and about 500 psig and a temperature of
about 50.degree. C. to about 500.degree. C., more preferably, between
about 100.degree. C. to about 375.degree. C. at pressures from about
20 psig and about 300 psig.
The following Examples will serve to illustrate certain specific
embodiments of the hereindisclosed invention. These Examples should
not, however, be construed as limiting the scope of the novel invention
as there are many variations which may be made thereon without departing
from the spirit of the disclosed invention, as those of skill in
the art will recognize.
COMPARATIVE EXAMPLE 1
This catalyst composition was made from 40% HAMS-1B crystalline
borosilicate sieve and 60% alumina. A 118 g portion of HAMS-1B was
gelled with an 1810 g portion of PHF alumina sol that has a 9.47%
by weight content of alumina, using 171 ml of concentrated ammonium
hydroxide (29% NH.sub.3) and 236 g of water. The gel was dried at
165.degree. C. for 18 hours. The dried sample was ground to 18-40
mesh then calcined at 538.degree. C. for 12 hours.
Ten grams of the catalyst was tested for xylene isomerization/ethylbenzene
conversion. The catalyst was placed in a 1/2" i.d. reactor
and treated with helium at 250 psig for 2 hours at room temperature.
The reactor temperature was then increased to 360.degree. C. under
a hydrogen flow and the catalyst was treated with hydrogen at this
temperature and other reaction conditions listed in the Table for
two more hours. The hydrocarbon feed was then passed through the
reactor once-through. The results are also shown in the Table following
Example 15.
EXAMPLE 2
In a small beaker containing 38 g of water was dissolved 3.2 g
of (NH.sub.4).sub.2 HPO.sub.4. The solution was then added slowly
to 25 g of the catalyst of Example 1 while stirring with a glass
rod. The sample was then dried at 130.degree. C. for 16 hours and
calcined at 538.degree. C. for 12 hours. The resulting impregnated
catalyst composition contained approximately 2.7 weight percent
phosphorus.
EXAMPLE 3
The catalyst composition of Example 3 was tested for isomerization
as in Example 1. The reaction conditions and the results are shown
in the Table.
EXAMPLE 4
An impregnated catalyst composition was prepared as in Example
2 by using 25 g of the catalyst composition of Example I and 5.33
g of (NH.sub.4).sub.2 HPO.sub.4. The resulting catalyst composition
contained approximately 4.2% by weight phosphorus.
EXAMPLE 5
The catalyst composition of Example 4 was tested for isomerization
as in Example 1. The reaction conditions and results are shown in
the Table.
EXAMPLE 6
An impregnated catalyst composition was prepared as in Example
2 by using 25 g of the catalyst composition of Example 1 and 10.66
g of (NH.sub.4).sub.2 HOP.sub.4. The amount of phosphorus in this
catalyst composition was approximately 7.6% by weight.
EXAMPLE 7
The catalyst composition of Example 6 was tested as in Example
1. The reaction conditions and results are shown in the Table.
EXAMPLE 8
An impregnated catalyst composition was prepared as in Example
2 by using 25 g of the catalyst composition of Example 1 and 9.29
g of NH.sub.4 H.sub.2 PO.sub.4. The resulting catalyst composition
contained approximately 7.8% by weight phosphorus.
EXAMPLE 9
The catalyst composition of Example 8 was tested as in Example
1. The reaction conditions and results are shown in the Table.
EXAMPLE 10
An impregnated catalyst composition was prepared by adding a methanol
solution of triethylphosphite [4.02 g of (C.sub.2 H.sub.5 O).sub.3
P in 25 g of methanol] to 25 g of the catalyst composition of Example
1 and mixing with a glass rod for a few minutes. The methanol was
allowed to evaporate in the hood at room temperature. The sample
was then dried at 130.degree. C. for 16 hours then calcined at 538.degree.
C. for 12 hours. The resulting catalyst composition contained approximately
2.5% by weight phosphorus.
EXAMPLE 11
The catalyst composition of Example 10 was tested as in Example
1. The reaction conditions and results are shown in the Table.
EXAMPLE 12
An impregnated catalyst composition was prepared by adding 2.37
g of H.sub.3 PO.sub.4 (85%) in 38 g of water to 25 g of the catalyst
composition of Example 1 and stirring with a glass rod for a few
minutes. The sample was then dried at 130.degree. C. for 16 hours
and calcined at 538.degree. C. for 12 hours. The resulting catalyst
composition contained approximately 2.5% by weight phosphorus.
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