Molecular sieve abstract
This invention relates to the use of pore mouth control of microporous
solids for developing novel molecular sieve adsorbents and their
potential in the drying of alcohols. More specifically, the invention
relates to the manufacture and use of a molecular sieve adsorbent,
which selectively adsorbs water from azeotropic alcohol-water mixtures
by pore mouth control of microporous solids with liquid phase metal
alkoxide deposition on the external surface at ambient conditions
of temperature and pressure. The prepared adsorbent is therefore
useful for the commercial drying of alcohols.
Molecular sieve claims
That which is claimed is:
1. A process for the preparation of a molecular sieve adsorbent
for adsorptive dehydration of alcohols, said process comprising
the steps of: a) obtaining a molecular sieve adsorbent represented
by the chemical formula: (Na.sub.2O).sub.6.(Al.sub.2O.sub.3).sub.6.(SiO.sub.2).sub.12.(M.-
sub.2/nO.sub.2).sub.x.wH.sub.2O, where M is the element selected
from Si, Al, Zr and Ti; n its valance, the values of x varies from
0.001 to 0.1 and w is the number of moles of water; b) activating
the molecular sieve adsorbent at a temperature in the range of 350
to 450.degree. C. to eliminate physically adsorbed water, for a
period ranging from 3 to 6 hours; c) cooling the activated the molecular
sieve adsorbent under vacuum in the range of 10.sup.-2 to 10.sup.-4
torr; d) treating the activated adsorbent with an alkoxide of element
M in a dry solvent; e) drying the treated activated adsorbent of
step (d) in air in static condition at a temperature in the range
of 15 to 40.degree. C.; f) converting the alkoxide deposited on
modified adsorbent into silica by calcining the same in a temperature
range of 450 to 600.degree. C. for a period ranging from 3 to 8
hrs, and g) obtaining the adsorbent by cooling the calcined product
of step (g) at ambient temperature in static condition.
2. The process of claim 1 wherein the preferred temperature of
activation of molecular sieve adsorbent is about 400.degree. C.
3. The process of claim 1 wherein the alkoxide of step (d) is
selected from the group consisting of: tetra methyl orthosilicate,
tetra ethyl orthosilicate, titanium iso-propoxide, zirconium iso-propoxide,
and aluminium iso-propoxide.
4. The process of claim 1 wherein the dry solvent of step (d)
is selected from the group consisting of: toluene, benzene, cyclohexane,
and xylene.
5. The process of claim 1 wherein in step (d) the treatment of
activated molecular sieve is performed by treating with alkoxide
solution of element M or with vapours of alkoxide.
6. The process of claim 4 wherein the activated adsorbent is treated
with the alkoxide of element M in a dry solvent in the in the concentration
range of 0.1 to 1.0 wt %/volume for a period in the range of 4 to
8 hours under continuous stirring.
7. The process of claim 4 wherein the activated adsorbent is treated
with the vapours of alkoxide in the temperature range of 80 to 150.degree.
C. for a period in the range of 2 to 6 hours.
8. The process of claim 1 wherein said metal alkoxide deposition
on the microporous solid surface is carried out in a simple liquid
phase reaction at ambient temperature and pressure conditions with
constant stirring.
9. The process of claim 5 wherein in step (d), 0.10 to 1.0 weight
percent of metal alkoxide is deposited uniformly on the surface
of activated adsorbent.
10. The process of claim 1 wherein in step (g), the temperature
of calcinations is about 550.degree. C.
11. The process of claim 1 wherein the calcinations time is about
4 hours.
12. The process of claim 1 wherein the adsorbent prepared is useful
for the dehydration of alcohols and the recovery of alcohol is 99.9%.
13. A process for the preparation of a molecular sieve adsorbent
for the adsorptive dehydration of alcohols using a molecular sieve
adsorbent represented by the chemical formula: (Na.sub.2O).sub.6.(Al.sub.2O.sub.3).-
sub.6.(SiO.sub.2).sub.12.(M.sub.2/nO.sub.2).wH.sub.2O, where M is
Si, Al, Zr, Ti; n its valancy, the values of x varies from 0.001
to 0.1 and w being the number of moles of water, which comprises
activating the molecular sieve at temperature in a range of 350
to 450.degree. C. to eliminate physically adsorbed water for a period
ranging from 3 to 6 hours; cooling the solid under vacuum in a range
of 10.sup.-2 to 10.sup.-4 torr; treating the activated solid with
a solution of alkoxide in a dry solvent for a period of 4 to 8 hours;
and heating the alkoxide deposited solid in the temperature range
of 450 to 600.degree. C. for a period ranging from 3 to 8 hours.
14. A process for the preparation of a molecular sieve adsorbent
for the adsorptive dehydration of alcohols using a molecular sieve
adsorbent represented by the chemical formula: (Na.sub.2O).sub.6.(Al.sub.2O.sub.3).-
sub.6.(SiO.sub.2).sub.12.(M.sub.2/nO.sub.2).sub.x.wH.sub.2O, where
M is Si, Al, Zr, Ti; n its valancy, the values of x varies from
0.001 to 0.1 and w being the number of moles of water, which comprises
activating the molecular sieve at temperature in the range of 350
to 450.degree. C. to eliminate physically adsorbed water for a period
ranging from 3 to 6 hours; cooling the solid under vacuum in the
range of 10.sup.-2 to 10.sup.-4 torr; treating the activated solid
with vapours of the alkoxide at a temperature range of 80 to 150.degree.
C. for a period of 2-to 6 hours; heating the alkoxide deposited
solid in the temperature range of 450 to 600.degree. C. for a period
ranging from 3 to 8 hours.
Molecular sieve description
FIELD OF THE INVENTION
[0001] The present invention relates to a process for the preparation
of a molecular sieve adsorbent for the adsorptive dehydration of
alcohols.
[0002] The invention relates to the preparation and use of surface
modified zeolites (activated molecular sieve) in the dehydration
of alcohols. More specifically, the invention relates to the preparation
and use of a molecular sieve adsorbent, which selectively removes
water from a water-ethanol azeotrope obtained from distillation
of the crude synthetic or fermentation feedstock.
BACKGROUND AND PRIOR ART
[0003] The use of anhydrous alcohol (99.5 vol. % ethanol) has become
an important consideration as a means of saving gasoline produced
from high-cost crude oil. It is a well-established fact that up
to 20 percent anhydrous ethanol can be blended with gasoline to
obtain a relatively high-octane antiknock fuel, which can be used
for internal combustion engines. With some engine modification,
anhydrous ethanol can be used as the fuel directly.
[0004] Alcohol/water mixtures, such as those produced by fermentation
of biomass material, form a single liquid phase that usually contains
more or less equal volumes of ethanol and water, at least after
initial distillation. Such mixtures are separated conventionally
by further distillation, sometimes with addition of benzene, cyclohexane,
etc. to yield an anhydrous alcohol fraction, which may contain minor
amounts of other alcohols, such as propyl or butyl. Adsorption and
solvent extraction are alternative or supplemental methods of separating
alcohol and water. An increasing use of alcohol is seen for fuel,
often in admixture with fossil fuels, such as gasoline or even diesel
oil, for example, in which anhydrous conditions are favoured.
[0005] Over the past 30 years a series of distillation systems
have been developed for the efficient recovery of ethanol from synthetic
and fermentation feedstock. These units produce high-grade industrial
alcohol, anhydrous alcohol, alcoholic spirits, and ethanol for motor
fuels. Ethanol quality and recovery have been improved while at
the same time, energy consumption has decreased.
[0006] Synthetic ethanol is purified in a simple three-column distillation
unit wherein the recovery is 98%, and the high-grade product contains
less than 20 mg/kg of total impurities and has a permanganate time
of over 60 min.
[0007] The following are key features for the efficient recovery
of high-grade ALCOHOL especially ethanol from fermentation feed
stocks:
[0008] 1) Extractive distillation results in a higher degree of
purity than is possible in conventional purification columns. Both
investment and operating costs are reduced.
[0009] 2) Pressure-cascading installations and heat pumps permit
substantial heat recovery and recycling, thus minimizing heat loss
and steam consumption. Virtually all (95-99%) the ethanol in the
crude feed is recovered as high-grade product.
[0010] 3) Advanced control systems ensure stable operating conditions.
Product quality can be maintained with a total impurity content
of less than 50 mg/kg and a permanganate time of over 45 min.
[0011] 4) Energy requirements are minimized. The flash heat recovered
from the grain-cooking system is used to heat the ethanol distillation
unit, thus reducing the energy consumption for ethanol production
by ca. 10%. Use of a vapour recompression technique can reduce the
energy required for the evaporation of stillage to as little as
one-tenth of that required in a triple- or quadruple-effect evaporator.
[0012] With the ready availability of 95% alcohol through distillation,
it might be expected that obtaining 100% (water free) alcohol would
provide little problem. However, this is not the case, for no matter
how efficient or long the distillation process, 95% alcohol or any
lower-strength solution cannot be further concentrated beyond about
a 96.4% alcohol solution by weight under standard conditions. At
approximately that point, equilibrium is reached in which the liquid
and vapour mixtures have the same composition. This is called an
azeotrope or a constant-boiling mixture. In the case of ethyl alcohol,
this is a binary azeotrope of the minimum-boiling variety. It has
been reported that pressure changes affect this azeotropic mixture.
[0013] To produce anhydrous ethanol, the water-ethanol azeotrope
obtained from distillation of the crude synthetic or fermentation
feedstock must be dehydrated. For economic reasons, large distilleries
rely mostly on azeotropic distillation for ethanol dehydration.
Benzene has been used as an azeotropic dehydrating (entraining)
agent in many plants, but some concern exists about its carcinogenicity
and toxicity. Cyclohexane and ethylene glycol are used in some distilleries
as effective dehydrating agents.
[0014] Some smaller ethanol plants use molecular sieve adsorption
techniques to dry the ethanol azeotrope. Pervaporation through semipermeable
membranes or use of a solid dehydrating agent may reduce energy
and equipment costs.
[0015] Growing requirements for anhydrous ethanol for use in motor
fuel gasoline blends require systems that operate with a minimum
of energy and that are also reliable in continuous operation. Although
production and blending of ethanol with gasoline have been practiced
in different countries during the past forty years, the use of ethanol
in such blends has been limited because of the relatively high costs
of production.
[0016] The conventional distillation system for recovering motor
fuel grade anhydrous ethanol from a dilute feedstock, such as fermented
beer or synthetic crude alcohol, utilizes the three essential steps:
(i) stripping and rectifying operation; (ii) dehydration; and (iii)
condensation and decantation in three different towers. In the first
tower the feedstock containing, 6 to 10 vol. % ethanol is subjected
to a preliminary stripping and rectifying operation in which the
concentration of water is materially reduced and concentrated ethanol
stream is removed which contains in the order of 95 vol. % ethanol,
thereby approaching the ethanol-water azeotrope composition of about
97 vol. % ethanol. The concentrated ethanol stream is next subjected
to azeotropic distillation in the second or dehydrating tower using
a suitable azeotropic or entraining agent, usually benzene or a
benzene-heptane mixture. This results in removal of most of the
remaining water, and the desired motor fuel grade anhydrous ethanol
product (99.5 vol. %) is recovered from the dehydrating tower. The
third tower of the system comprises a stripping tower in which the
benzene or other azeotropic agent is recovered from the water-rich
phase following condensation and decantation of the azeotropic overhead
stream from the dehydrating tower.
[0017] One of the key elements in the high operating cost of the
above described conventional distillation system is the high thermal
energy requirement of the system, particularly steam consumption.
The conventional system also has other serious short comings that
detract from the commercial feasibility of the use of anhydrous
ethanol as motor fuel. For example, the stripper-rectifier tower
is occasionally operated under super atmospheric pressure, which
results in higher temperatures, which in turn cause rapid fouling
and plugging of the trays. As a consequence, periodic interruption
of the operation is necessary to permit cleaning of the tower with
resultant high maintenance costs. Furthermore, the conventional
system does not include adequate provision to overcome the operating
difficulties and product quality problems caused by the presence
of higher boiling and lower boiling impurities in the feedstock.
[0018] In the prior art, to satisfy the ever-growing demand for
absolute alcohol on a commercial scale, several continuous methods
have been used. The first, based on a patent issued to Donald B.
Keyes (U.S. Pat. No. 1830469) relies upon the dehydration of ethyl
alcohol by the formation of a ternary azeotrope with benzene, ethyl
alcohol and the remaining water in a 95% alcohol solution. This
azeotropic mixture, having a low boiling point, is distilled off
and must be separated by further secondary operations, leaving anhydrous
ethyl alcohol at the bottom of the rectification column. Many other
compounds have been suggested for use in similar azeotropic distillations,
including ethyl ether, methylene chloride, isobutylene, isooctane,
gasoline, benzene and naphtha, isopropyl ether, methyl alcohol and
acetone. All of these distillations suffer from similar problems,
however, those being increased cost and increased danger from fire
or explosion during processing due to the added components.
[0019] A second process, based on the patent to Joseph Van Ruymbeke
(U.S. Pat. No. 1459699) relies upon a reflux of glycerine in the
column to act as a dehydrating agent. The glycerine and water pass
out at the bottom of the still with the distillate being anhydrous
ethyl alcohol. Considerable alcohol is caught up with the glycerine
and water, however, and must be recovered in a second rectifying
still. Yet another method, reported to be the earliest of its kind,
utilizes anhydrous potassium carbonate as the drying agent. Many
other inorganic compounds have been similarly studied, such as calcium
oxide, calcium carbide, calcium sulphate, calcium aluminium oxide,
aluminium and mercuric chloride, zinc chloride and sodium hydroxide,
some of which are suggested as additives in the glycerine refluxing
process mentioned above. The limitation of this processes are that
its required two-step rectifying column and in another additive
inorganic materials are not eco-friendly.
[0020] U.S. Pat. No. 4161429 (1979) to J. J. Baiel, et al. discloses
a high-pressure (100-200 Psi) azeotropic distillation process of
ethanol conducted in the absence of oxygen using pentanes and cyclohexane
as entrainers. The drawbacks associated with the process are: (i)
it requires high-pressure distillation; and (ii) continuously maintaining
the oxygen free atmosphere is difficult.
[0021] U.S. Pat. No. 4217178 (1980) to R. Katzen, et al. discloses
an improved distillation method for obtaining motor fuel grade anhydrous
ethanol from fermentation or synthetic feedstock. The three-tower
system used in the anhydrous ethanol production comprises a stripper-rectifier
tower in which the dilute feedstock is converted to a concentrated
ethanol stream, a dehydrating tower in which water is removed from
the concentrated ethanol stream by azeotropic distillation, and
a stripper tower for recovering the azeotropic agent. The limitations
of this process are the high operating pressure and the difficulty
in complete removal of the azeotropic agent from the anhydrous ethanol.
[0022] U.S. Pat. No. 4256541 (1981) to W. C. Muller, et al. discloses
a method for distillation of anhydrous (absolute) ethanol with high
thermal efficiency from any dilute feedstock using cyclohexane as
the azeotrope-forming agent. The limitation of the process is that
the process involves the use of cyclohexane as azeotropic forming
agent during the azeotropic distillation.
[0023] U.S. Pat. No. 4273621 (1981) to L. L. Fornoff discloses
a process for dehydrating aqueous ethanol utilizing a high-pressure
distillation with a single distillation column of an aqueous ethanol
admixture, to achieve a vapour phase ethanol-water admixture containing
about 90%, by weight, of ethanol, and then drying the vaporous admixture,
in the presence of CO.sub.2 with a crystalline zeolite type 3A.
The limitations of this process are the low water adsorption capacity
and low hydrothermal stability of the zeolite 3A type adsorbent.
[0024] U.S. Pat. No. 4277635 (1981) to C. S. Oulman, et al. discloses
a process for concentrating relatively dilute aqueous solutions
of ethanol by passing through a bed of a crystalline silica polymorph,
such as silicalite, to adsorb the ethanol with residual dilute feed
in contact with the bed, which is displaced by passing concentrated
aqueous ethanol through the bed without displacing the adsorbed
ethanol. A product concentrate is then obtained by removing the
adsorbed ethanol from the bed together with at least a portion of
the concentrated aqueous ethanol used as the displacer liquid. The
limitation of the process is the requirement of passing concentrated
ethanol for the recovery of the anhydrous ethanol.
[0025] U.S. Pat. No. 4301312 (1981) to H. M. Feder, et al. discloses
a process for the production of anhydrous ethanol by using a transition
metal carbonyl and a tertiary amine as a homogeneous catalytic system
in methanol or a less volatile solvent to react methanol with carbon
monoxide and hydrogen gas producing ethanol and carbon dioxide.
The gas contains a high carbon monoxide to hydrogen ratio as is
present in a typical gasifier product. The reaction has potential
for anhydrous ethanol production as carbon dioxide rather than water
is produced. The only other significant by product is methane. The
drawbacks of the process are that it involves the use of inflammable
hydrogen and carbon monoxide and the formation of methane by-product.
[0026] U.S. Pat. No. 4306884 (1981) to E. R. Roth discloses a
process for the separation of alcohol/water mixtures by extraction
of alcohol with a solvent especially suited to such extraction and
subsequent removal with addition of gasoline between the solvent
extraction and solvent recovery steps. The limitation of the process
is that it can produce only denatured ethanol, which contains the
solvents used for the extraction of ethanol.
[0027] U.S. Pat. No. 4306940 (1981) to S. Zenty discloses a process
and apparatus especially suited for distilling alcohol from aqueous
fermentation liquors wherein liquid vapours from a liquid mixture
is pre heated with the product. The limitation of the process is
that it can produce only a water-ethanol azeotropic mixture containing
about 95% of ethanol. The production of anhydrous ethanol requires
additional purification steps.
[0028] U.S. Pat. No. 4306942 (1981) to B. F. Brush, et al. discloses
an improved distillation method and apparatus for recovering hydrous
ethanol from fermentation or synthetic feedstock with a multiple
heat exchange steps. The limitation of the process is that it can
produce only a water-ethanol azeotropic mixture containing about
95% of ethanol. Anhydrous ethanol production requires additional
dehydration steps.
[0029] U.S. Pat. No. 4308106 (1981) to R. L. Mannfeld provides
a process and still for removing substantially all water from an
alcohol-containing solution using a rectification column under reduced
pressure of about 40 mmHg or less to get alcohol having a water
content of about 2% by volume or less. The limitation of the process
is that maintaining very low pressure for the distillation is difficult
and needs specially designed pumps.
[0030] U.S. Pat. No. 4346241 (1982) to J. Feldman provides a
process for obtaining substantially anhydrous ethanol from a dilute
aqueous ethanol solution in which the ethanol stream is subjected
to liquid-liquid extraction to provide an ethanol-poor raffinate
phase and an ethanol-rich extract phase. The ethanol present in
said latter phase is concentrated in a rectifying column to provide
an aqueous ethanol of high proof and the concentrated ethanol is
azeotropically distilled in an anhydrous column operated under substantially
super atmospheric pressure at high temperature. The drawbacks associated
with the process are the use of amines as the extactant for the
extraction of ethanol. Also, multiple steps are involved which increases
the unit operation as well as the time for dehydration.
[0031] U.S. Pat. No. 4349416 (1982) to H. S. Brandt, et al. discloses
a process and apparatus for the separation of components from a
mixture, which forms an azeotrope, by subjecting the mixture to
extractive distillation to remove one of the components and regeneration
to separate another component from the extracting agent added to
the extractive distillation column. The drawbacks associated with
the process are the use of azeotropic forming agents and the extractive
distillation process involved in the separation.
[0032] U.S. Pat. No. 4351732 (1982) to J. D. Psaras, et al. provides
a process and apparatus for dehydrating liquid phase ethanol in
an adsorber unit containing at least two towers that cycle between
adsorption and desorption cycles, characterized in the desorption
cycle by an indirect heating volatilisation of absorbed and adsorbed
liquid at ambient pressures, and by a final stages desorption under
sub-atmospheric pressures. The limitations of the process are the
low water adsorption selectivity and capacity of the adsorbent.
[0033] U.S. Pat. No. 4366032 (1982) to P. Mikitenko, et al. provides
a process for dehydrating an aliphatic alcohols-water mixture wherein
the alcohols-water mixture is subjected to a first fractionation
in the presence of a selective solvent, giving a vapour effluent
containing dehydrated light alcohols and a liquid phase containing
heavy alcohols, water and the selective solvent. Said liquid phase
is subjected to a second fractionation giving as vapour effluent
an hetero-azeotropic mixture of water and heavy alcohols and a liquid
effluent. The limitations of the process are the use of azeotropic
forming agents and the extractive distillation process involved
in distillation process.
[0034] U.S. Pat. No. 4372822 (1983) to W. C. Muller, et al. discloses
a process for the preparation of anhydrous ethanol by distillation
with thermal efficiency from a dilute feedstock. The columns are
operated at substantially super atmospheric pressure with thermal
values recovered from these columns being used in the operation
of the rectifying column. The limitation of the process is that
it requires high-pressure and elevated temperature for the anhydrous
ethanol production.
[0035] U.S. Pat. No. 4422903 (1983) to J. R. Messick, et al.
discloses an improved distillation method and apparatus for recovering
anhydrous ethanol from fermentation or synthetic feedstock. The
system includes at least one stripper-rectifier tower, a dehydrating
tower, and an azeotropic agent stripping tower at higher pressure
than the stripper-rectifier tower, and also condenses the overhead
vapours from the dehydrating tower. The drawback of the process
is that it is multi-stage at elevated temperature and pressure.
It also involves the use of azeotropic forming agents in the distillation
process.
[0036] U.S. Pat. No. 4428798 (1984) to D. Zudkevitch, et al.
discloses a process for separating low molecular weight alcohols,
especially ethanol, from aqueous mixtures. The process involves
subjecting alcohol-water mixtures to extraction and/or extractive
distillation procedures. Extractive solvents useful for the process
of this invention include phenyls having at least six carbon atoms
and a boiling point between 180.degree. C. and 350.degree. C. The
limitation of the process is the use of phenyls as extractive solvents
for the azeotropic distillation process at higher temperature and
pressure. Moreover, the removal of phenyl from dehydrated ethanol
is also essential.
[0037] U.S. Pat. No. 4455198 (1984) to D. Zudkevitch, et al.
discloses a process for ethanol concentration from ethanol-water
mixtures by extraction or extractive distillation with a solvent,
a cyclic ketone of at least seven carbons or cyclic alcohol of at
least eight carbons such a cyclohexylcyclohexanone or cyclohexylcyclohexanol.
The preferred solvents are also non-toxic, such that the alcohol
can be used for human consumption. The limitations of the process
are the use of azeotropic forming agents and the extractive distillation
process involved in distillation process.
[0038] U.S. Pat. No. 4559109 (1985) to F. M. Lee, et al. discloses
a process for producing anhydrous ethanol from an ethanol-water
mixture feedstock comprising subjecting the feedstock to distillation
in a first distillation zone to produce an overhead vapours of from
80 to 90 weight percent ethanol, subjecting the thus produced overhead
vapours to extractive distillation in an extractive distillation
zone to produce anhydrous ethanol vapour overhead of about 99.5
weight percent ethanol and a solvent-rich bottom stream. The drawback
of the process is the azeotropic distillation involves the use of
toxic solvents as the azeotrope-forming agent.
[0039] U.S. Pat. No. 4620857 (1986) to E. Vansant, et al. discloses
a process for the porous solid such as a zeolite or clay can be
degassed to make it suitable as an adsorbent, after which the entrances
of the pores are narrowed to a desired size by treating the porous
solid with chemisorbable materials such as diborane. The limitations
of the process are that the diborane used for the narrowing of the
pores is highly reactive and toxic and the narrowing of the pores
may not be uniform.
[0040] U.S. Pat. No. 4645569 (1987) to T. Akabane, et al. discloses
a process for producing anhydrous ethanol using an apparatus comprising
a combination of a concentration column, an azeotropic distillation
column, and a solvent recovery column, capable of effectively utilizing
the vapour at the top of the concentration column and the azeotropic
distillation column. The limitation of the process is that the extractive
distillation process consumes a very high amount of energy.
[0041] U.S. Pat. No. 4654123 (1987) to L. Berg, et al. discloses
a process for the separation of alcohol/water using extractive distillation
in which the water is removed as overhead product and the ethanol
and extractive agent as bottoms and subsequently separated by conventional
rectification. Typical examples of suitable extractive agents are
hexahydrophthalic anhydride; methyl tetrahydrophthalic anhydride
and pentanol-1; trimellitic anhydride, ethyl salicylate and resorcinol.
The limitations of the process are that the extractive distillation
process involves multiple steps and involves the use of toxic azeotropic
forming agents.
[0042] U.S. Pat. No. 4692218 (1987) to H. Houben, et al. discloses
a method and apparatus for simultaneously producing various forms
of alcohol, including ethanol, which can likewise be withdrawn from
the apparatus simultaneously. To this end, successive columns in
the individual processing stages, each of which includes distillation,
rectification, purification and dehydration, are connected in parallel
for product flow but in series for energy flow and conservation.
The limitations of the process are that it involves different process
stages and requires high amount of energy.
[0043] U.S. Pat. No. 5035776 (1991) to J. P. Knapp discloses
a thermally integrated extractive distillation process for recovering
anhydrous ethanol from fermentation or synthetic feed stocks with
four distillation columns. In the first step, the dilute ethanol
water mixture is concentrated by distillation. The concentrated
ethanol in the first distillation column is then distilled at higher
pressures in the second and third distillation column to get the
azeotropic mixture of ethanol and water. The azeotropic mixture
thus produced is then subjected to extractive distillation to get
anhydrous ethanol. The limitations of the process are that it involves
multi-stage distillation and extractive distillation for the production
of anhydrous ethanol.
[0044] In one approach, a chemical vapour deposition technique
was used for controlling the pore opening size of the zeolites by
the deposition of silicon alkoxide for the size/shape selective
separation of molecules [M. Niwa et al., J C S Faraday Trans. I,
1984 80 3135-3145; M. Niwa et al., J. Phys. Chem., 1986 90 6233-6237;
Chemistry Letters, 1989 441-442; M. Niwa et al., Ind. Eng. Chem.
Res., 1991 30 38-42; D. Ohayon et al., Applied Catalysis A-General,
2001 217 241-251]. Chemical vapour deposition is carried out by
taking a requisite quantity of zeolite in a glass reactor, which
is thermally activated at 450.degree. C. in situ under inert gas
like nitrogen flow. The vapours of silicon alkoxide are continuously
injected into inert gas stream, which carries the vapours to zeolite
surface where alkoxide chemically reacts with silanol groups of
the zeolite. Once the desired quantity of alkoxide is deposited
on the zeolite, sample is heated to 550.degree. C. in air for 4-6
hours after which it is brought down to ambient temperature and
used for adsorption. The major disadvantages of this technique are:
(i) Chemical vapour deposition, which leads to non-uniform coating
of alkoxide which in turn results in non-uniform pore mouth closure;
(ii) The process has to be carried out at elevated temperature where
the alkoxide gets vaporised; (iii) The deposition of the alkoxide
requires to be done at a slow rate for better diffusion; and (iv)
This method is expensive and lack of a commercial level at higher
scale will be difficult.
[0045] To summarize, the known processes are complex, require other
additives (such as benzene or ether), which significantly increase
cost and potential hazard during use, and fail to provide a safe,
efficient, simple method of operation. The applicant's invention
described and claimed herein below attempts to meet this need.
OBJECT OF THE INVENTION
[0046] The main object of the present invention is to provide a
process for the preparation of a molecular sieve adsorbent for the
adsorptive dehydration of alcohols, which obviates the drawbacks
as detailed above.
[0047] Still another object of the present invention is to prepare
a molecular sieve-type adsorbent for the dehydration of the alcohols.
[0048] Still another object of the present invention is to provide
an adsorbent, which can be prepared by the external surface modification
of the microporous solids like zeolites to have molecular sieving
effect.
[0049] Yet another object of the present invention is to have a
uniform deposition of alkoxide on the surface of the zeolites.
[0050] Yet another object of the present invention is to prepare
a molecular sieve adsorbent with high thermal and hydrothermal stability.
[0051] Yet another object of the present invention is to prepare
an adsorbent, which selectively adsorbs water from water-alcohol
mixtures and can be used commercially for the separation and dehydration
of alcohols.
SUMMARY OF THE INVENTION
[0052] This invention relates to the use of pore mouth control
of microporous solids for developing novel molecular sieve adsorbents
and their potential in the drying of alcohols. More specifically,
the invention relates to the manufacture and use of a molecular
sieve adsorbent, which selectively adsorbs water from azeotropic
alcohol-water mixtures, by pore mouth control of microporous solids
with liquid phase metal alkoxide deposition on the external surface
at ambient conditions of temperature and pressure. Thus, prepared
adsorbent is useful for the commercial drying of alcohols.
DETAILED DESCRIPTION OF THE INVENTION
[0053] Accordingly, the present invention provides a process for
the preparation of a molecular sieve adsorbent for the adsorptive
dehydration of alcohols; said process comprising the steps of:
[0054] a) obtaining a molecular sieve adsorbent represented by
the chemical formula, (Na.sub.2O).sub.6.(Al.sub.2O.sub.3).sub.6.(SiO.sub.2).s-
ub.12.(M.sub.2/nO.sub.2).sub.x.wH.sub.2O, where M is Si, Al, Zr,
Ti, n its valance, the values of x varies from 0.001 to 0.1 and
w being the number of moles of water;
[0055] b) activating the molecular sieve adsorbent in the temperature
range of 350 to 450.degree. C. to eliminate physically adsorbed
water, for a period ranging from 3 to 6 hours;
[0056] c) cooling the activating the molecular sieve adsorbent
in a desiccators under vacuum in the range of 10.sup.-2 to 10.sup.-4
torr;
[0057] d) treating the activated adsorbent with alkoxide solution
of metal M in a dry solvent in the concentration range of 0.1 to
1.0 wt %/volume for a period in the range of 4 to 8 hours under
continuous stirring;
[0058] e) recovering the solvent by conventional techniques for
re-use;
[0059] f) drying the treated activated adsorbent of step (d) in
air in static condition at ambient temperature in the range of 20
to 35.degree. C.;
[0060] g) converting the alkoxide deposited on modified adsorbent
into silica by calcining the same in the temperature range of 450
to 600.degree. C. for a period ranging from 3 to 8 hrs, and
[0061] h) obtaining the adsorbent by cooling the same at ambient
temperature in static condition or by treating the activated adsorbent
with the vapours of the alkoxide at a temperature range of 80-150.degree.
C. for a period of 2-6 hours.
[0062] In an embodiment of the present invention, commercially
available adsorbent may used for the preparation of the molecular
sieve adsorbent.
[0063] In another embodiment of the present invention, the adsorbent
was activated at 350 to 550.degree. C. for 3-6 hours followed by
cooling under inert or vacuum condition.
[0064] In another embodiment of the present invention, the alkoxide
was dissolved in dry solvent, which may be selected from like toluene,
benzene, xylene and cyclohexane.
[0065] In still another embodiment of the present invention, the
alkoxides used are tetra methyl orthosilicate, tetra ethyl orthosilicate,
titanium iso-propoxide, zirconium iso-propoxide and aluminium iso-propoxide.
[0066] In another embodiment of the present invention, 0.10 to
1.00 weight percentage of alkoxide may be deposited onto the zeolite
in a single step by treating the activated adsorbent with a solution
of alkoxide in dry solvent for 4 to 8 hours.
[0067] In still another embodiment of the present invention, said
alkoxide may be deposited in the range of was carried out at alkoxide
concentration of 0.10 to 1.00% by weight of the adsorbent.
[0068] In still another embodiment of the present invention, the
alkoxide deposition may be carried out in liquid phase for a period
ranging from 4 to 8 hours under continuous stirring at ambient temperature.
[0069] In another embodiment of the present invention, the alkoxide
may be deposited onto the zeolite in a single step vapour phase
process by treating the activated adsorbent with the vapours of
the alkoxide at a temperature range of 80-150.degree. C. for a period
of 2-6 hours.
[0070] In still another embodiment of the present invention, the
alkoxide deposition may be uniform on the surface of the adsorbent.
[0071] In still another embodiment of the present invention, the
solvent was recovered by distillation method preferably under vacuum
distillation and can be re-used.
[0072] In still another embodiment of the present invention, the
adsorbents are dried in air or under vacuum conditions.
[0073] In still another embodiment of the present invention, the
adsorbent is calcined in the temperature range 500 to 600.degree.
C., preferably at 550.degree. C.
[0074] In the present invention, we report a novel process to control
the pore size of microporous solids like zeolites, which selectively
adsorb water from alcohol-water azeotropic mixtures. Furthermore
this adsorbent displays high thermal and hydrothermal stability.
[0075] Microporous solids like zeolites are finding increased applications
as adsorbents for separating mixtures of closely related compounds.
These have a three dimensional network of basic structural units
consisting SiO.sub.4 and AlO.sub.4 tetrahedrons linked to each other
by sharing apical oxygen atoms. Silicon and aluminium atoms lie
in the centre of the tetrahedral. The resulting alumno-silicate
structure, which is generally highly porous, possesses three-dimensional
pores the access to which is through molecular sized windows. In
a hydrated form, the preferred zeolites are generally represented
by the following formula, M.sub.2/nO.Al.sub.2O.sub.3.xSiO.sub.2.wH.sub.2O,
where M is a cation, which balances the electrovalence of the tetrahedral
and is generally referred to as extra framework exchangeable cation,
n represents the valancy of the cation and x and w represents the
moles of SiO.sub.2 and water respectively.
[0076] The attributes which make the zeolites attractive for separation
include an unusually high thermal and hydrothermal stability, uniform
pore structure, easy pore aperture modification and substantial
adsorption capacity even at low adsorbate pressures. Furthermore,
zeolites can be produced synthetically under relatively moderate
hydrothermal conditions.
[0077] Structural analysis of the samples was done by X-ray diffraction
where in the crystallinity of the zeolites are measured from the
intensity of the well-defined peaks. The in situ X-ray powder diffraction
measurements at 30.degree. C., 100.degree. C., 200.degree. C., 300.degree.
C., 400.degree. C., 500.degree. C., 600.degree. C., 650.degree.
C., 700.degree. C., 750.degree. C., 800.degree. C. and 850.degree.
C. shows that the newly developed adsorbent have high thermal stability.
X-ray powder diffraction was measured using PHILIPS X'pert MPD system
equipped with XRK 900 reaction chamber.
[0078] Microporous solid powder with a chemical composition [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12.wH.sub.2O]
was used as the starting material. X-ray diffraction data showed
that the starting material was highly crystalline. A known amount
of the powder [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12.wH.sub.2O]
was activated at 400.degree. C. to remove the water adsorbed and
mixed thoroughly with a solution having known amount of alkoxide
in 100 ml dry solvent, the sample was dried by evaporating solvent
under reduced pressure and the alkoxide species deposited on the
solids surface was converted into silica by calcinations of the
zeolite at 550.degree. C.
[0079] Water, methanol and ethanol adsorption were studied gravimetrically
after activating the sample at 400.degree. C.
[0080] Advantages of the present invention include:
[0081] 1. The adsorbent, prepared by the modification of microporous
solid selectively adsorbs water over alcohols;
[0082] 2. The adsorbent is prepared by a simple liquid phase or
vapour phase alkoxide deposition;
[0083] 3. The alkoxide deposition is uniform on the external surface
of the microporous solid;
[0084] 4. The metal alkoxide deposition is carried out at ambient
temperature and pressure;
[0085] 5. The solvent used for the alkoxide deposition can be recovered
by distillation method;
[0086] 6. The adsorbent shows very high thermal and hydrothermal
stability; and
[0087] 7. The adsorbent is useful in the commercial drying of alcohols.
[0088] Furthermore, the molecular sieve adsorbent obtained by the
control of the pore mouth of the microporous solids with liquid
phase metal alkoxide deposition on the external surface at ambient
conditions of temperature and pressure involves:
[0089] (i) the deposition of alkoxide by chemically reacting alkoxide
with silanol groups present on the external surface of the activated
molecular sieve (zeolite) followed by calcination at 500-600.degree.
C.,
[0090] (ii) liquid phase or vapour phase chemical reaction of alkoxide
in moisture free solvent to ensure uniform deposition of silica
on the surface of the microporous solid at ambient conditions,
[0091] (iii) enhancement of thermal and hydrothermal stability
of the adsorbent by alkoxide deposition on the external surface
of the solids, and
[0092] (iv) preparation microporous solids based dehydrating adsorbent
based on shape/size selectivity by controlling the pore mouths of
the solids by depositing inorganic oxides on the external surface.
Brief Description of the Table
[0093] Table-1: The adsorption capacity and selectivity of all
18 adsorbent samples are enumerated in Table 1 and correspond to
the examples provided herein.
1 TABLE-1 Amount Adsorbed in wt % Sample Methanol Ethanol Water
Example-1 18.20 15.76 22.21 Example-2 6.17 5.40 21.26 Example-3
6.18 5.39 21.33 Example-4 6.00 5.19 21.38 Example-5 5.30 3.04 22.17
Example-6 2.40 2.08 21.15 Example-7 2.63 1.92 21.69 Example-8 2.23
1.97 20.06 Example-9 5.37 5.02 21.97 Example-10 2.71 2.18 21.82
Example-11 5.12 4.31 22.06 Example-12 2.51 1.84 21.87 Example-13
2.62 1.91 22.12 Example-14 2.42 1.73 21.58 Example-15 2.52 1.93
22.15 Example-16 2.65 1.99 21.91 Example-17 2.64 2.42 21.07 Example-18
2.57 1.82 21.43
EXAMPLES
[0094] The following examples are given by way of illustration
and therefore should not be constructed to limit the scope of the
present invention.
Example-1
[0095] A known amount of microporous solid with chemical composition,
[(Na.sub.2O).sub.6(Al.sub.2O.sub.3).sub.6.(SiO.sub.2).sub.12.wH.sub.2O],
was activated at 400.degree. C. and adsorption measurements were
carried out by measuring the adsorption isotherms. Methanol, ethanol
and water adsorption capacities are, 18.20%, 15.76% and 22.21% respectively
and are given in Table 1.
Example-2
[0096] 10.0 g of the solid powder [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2)-
.sub.12.wH.sub.2O] was activated at 400.degree. C. to remove the
adsorbed water in the zeolite and stirred with 0.10 g tetra methyl
orthosilicate in 100 ml dry toluene. The sample was dried after
5 hrs by evaporating solvent under reduced pressure. The tetra methyl
ortho silicate species deposited on the external solid surface was
converted into silica by calcinations of the solid at 550.degree.
C. A known amount of the sample was activated at 400.degree. C.
under vacuum and adsorption measurements were carried out as described
earlier. In situ X-ray powder diffraction measurements at various
temperatures up to 850.degree. C. shows that the adsorbent has high
thermal and hydrothermal stability. Methanol, ethanol and water
adsorption capacity values are 6.17%, 5.40% and 21.26% respectively
and are given in Table 1.
Example-3
[0097] 10.0 g of the solid powder with chemical composition, [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12.wH.sub.2O]
was activated at 400.degree. C. to remove the water adsorbed in
the solid and stirred with 0.10 g tetra ethyl orthosilicate in 100
ml dry solvent. The sample was dried after 5 hrs by evaporating
solvent under reduced pressure. The tetra ethyl ortho silicate species
deposited on the external surface of the solid was converted into
silica by calcinations of the zeolite at 550.degree. C. A known
amount of the sample was activated at 400.degree. C. under vacuum
and adsorption measurements were carried out as described earlier.
In situ X-ray powder diffraction measurements at various temperatures
up to 850.degree. C. shows that the adsorbent has high thermal and
hydrothermal stability. Methanol, ethanol and water adsorption capacity
values are 6.17%, 5.39% and 21.33% respectively and are given in
Table 1.
Example-4
[0098] 10.0 g of the solid powder with chemical composition, [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12.wH.sub.2O]
was activated at 400.degree. C. to remove the water adsorbed in
the solid and stirred with 0.15 g tetra ethyl orthosilicate in 100
ml dry toluene. The sample was dried after 5 hrs by evaporating
toluene under reduced pressure. The tetra ethyl ortho silicate species
deposited on the external surface of the solid was converted into
silica by calcinations of the zeolite at 550.degree. C. A known
amount of the sample was activated at 400.degree. C. under vacuum
and adsorption measurements were carried out as described earlier.
In situ X-ray powder diffraction measurements at various temperatures
up to 850.degree. C. shows that the adsorbent has high thermal and
hydrothermal stability. Methanol, ethanol and water adsorption capacity
values are 6.00%, 5.19% and 21.38% respectively and are given in
Table 1.
Example-5
[0099] 10.0 g of the solid powder with chemical composition, [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12.wH.sub.2O]
was activated at 400.degree. C. to remove the water adsorbed in
the zeolite and stirred with 0.20 g tetra ethyl orthosilicate in
100 ml dry toluene. The sample was dried after 5 hrs by evaporating
toluene under reduced pressure. The tetra ethyl ortho silicate species
deposited on the external surface solid was converted into silica
by calcinations of the solid at 550.degree. C. A known amount of
the sample was activated at 400.degree. C. under vacuum and adsorption
measurements were carried out as described earlier. In situ X-ray
powder diffraction measurements at various temperatures up to 850.degree.
C. shows that the adsorbent has high thermal and hydrothermal stability.
Methanol, ethanol and water adsorption capacity values are 5.30%,
5.04% and 22.17% respectively and are given in Table 1. 5.0 g of
the adsorbent in was filled in a column and activated at 400.degree.
C. by passing 99.5% pure nitrogen gas to remove the adsorbed molecules.
The activated adsorbent was cooled to room temperature under inert
atmosphere. 25 ml ethyl alcohol-water mixture containing 95% ethyl
alcohol was passed through the column and the product was analysed
by Gas Chromatography and was found that the purity of the product
ethanol was 99.9%.
Example-6
[0100] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 0.25 g tetra ethyl orthosilicate
in 100 ml dry toluene. The sample was dried after 5 hrs by evaporating
toluene under reduced pressure. The tetra ethyl ortho silicate species
deposited on the external solid surface was converted into silica
by calcinations of the solid at 500.degree. C. A known amount of
the sample was activated at 400.degree. C. under vacuum and adsorption
measurements were carried out as described earlier. In situ X-ray
powder diffraction measurements at various temperatures up to 850.degree.
C. shows that the adsorbent has high thermal and hydrothermal stability
Methanol, ethanol and water adsorption capacity values are 2.40%,
2.08% and 21.15% respectively and are given in Table 1.
Example-7
[0101] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 0.30 g tetra ethyl orthosilicate
in 100 ml dry toluene. The sample was dried after 5 hrs by evaporating
toluene under reduced pressure. The tetra ethyl ortho silicate species
deposited on the external solid surface was converted into silica
by calcinations of the zeolite at 550.degree. C. A known amount
of the sample was activated at 400.degree. C. under vacuum and adsorption
measurements were carried out as described earlier. In situ X-ray
powder diffraction measurements at various temperatures up to 850.degree.
C. shows that the adsorbent has high thermal and hydrothermal stability.
Methanol, ethanol and water adsorption capacity values are 2.63%,
1.92% and 21.69% respectively and are given in Table 1. 5.0 g of
the adsorbent was filled in a column and activated at 400.degree.
C. by passing 99.5% pure nitrogen gas to remove the adsorbed molecules.
The activated adsorbent was cooled to room temperature under inert
atmosphere. 25 ml ethyl alcohol-water mixture containing 95% ethyl
alcohol was passed through the column and the product was analysed
by Gas Chromatography and was found that the purity of the product
ethanol was 99.9%.
Example-8
[0102] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 1.00 g tetra ethyl orthosilicate
in 100 ml dry toluene. The sample was dried after 5 hrs by evaporating
toluene under reduced pressure. The tetra ethyl ortho silicate species
deposited on the external solid surface was converted into silica
by calcinations of the zeolite at 550.degree. C. A known amount
of the sample was activated at 400.degree. C. under vacuum and adsorption
measurements were carried out as described earlier. In situ X-ray
powder diffraction measurements at various temperatures up to 850.degree.
C. shows that the adsorbent has high thermal and hydrothermal stability.
Methanol, ethanol and water adsorption capacity values are 2.23%,
1.97% and 20.06% respectively and are given in Table 1. 5.0 g of
the adsorbent was filled in a column and activated at 450.degree.
C. by passing 99.5% pure nitrogen gas to remove the adsorbed molecules.
The activated adsorbent was cooled to room temperature under inert
atmosphere. 25 ml methanol-water mixture containing 94% methanol
was passed through the column and the product was analysed by Gas
Chromatography and was found that the purity of the product methanol
was 99.9%.
Example-9
[0103] 10.0 g of the zeolite powder [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.-
2).sub.12.wH.sub.2O] was activated at 400.degree. C. to remove the
water adsorbed in the zeolite and stirred with 0.20 g tetra methyl
orthosilicate in 100 ml dry toluene. The sample was dried after
5 hrs by evaporating toluene under reduced pressure. The tetra methyl
ortho silicate species deposited on the zeolite surface was converted
into silica by calcinations of the zeolite at 550.degree. C. A known
amount of the sample was activated at 400.degree. C. under vacuum
and adsorption measurements were carried out as described earlier.
In situ X-ray powder diffraction measurements at various temperatures
up to 850.degree. C. shows that the adsorbent has high thermal and
hydrothermal stability. Methanol, ethanol and water adsorption capacity
values are 5.37%, 5.02% and 21.97% respectively and are given in
Table 1. 5.0 g of the adsorbent in was filled in a column and activated
at 400.degree. C. by passing 99.5% pure nitrogen gas to remove the
adsorbed molecules. The activated adsorbent was cooled to room temperature
under inert atmosphere. 25 ml ethyl alcohol-water mixture containing
95% ethyl alcohol was passed through the column and the product
was analysed by Gas Chromatography and was found that the purity
of the product ethanol was 99.9%.
Example-10
[0104] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 0.25 g tetra methyl orthosilicate
in 100 ml dry benzene. The sample was dried after 5 hrs by evaporating
benzene under reduced pressure. The tetra methyl ortho silicate
species deposited on the solid surface was converted into silica
by calcinations of the zeolite at 500.degree. C. A known amount
of the sample was activated at 400.degree. C. under vacuum and adsorption
measurements were carried out as described earlier. In situ X-ray
powder diffraction measurements at various temperatures up to 850.degree.
C. shows that the adsorbent has high thermal and hydrothermal stability.
Methanol, ethanol and water adsorption capacity values are 2.71%,
2.18% and 21.82% respectively and are given in Table 1. 5.0 g of
the adsorbent was filled in a column and activated at 450.degree.
C. by passing 99.5% pure nitrogen gas to remove the adsorbed molecules.
The activated adsorbent was cooled to room temperature under inert
atmosphere. 25 ml methanol-water mixture containing 94% methanol
was passed through the column and the product was analysed by Gas
Chromatography and was found that the purity of the product methanol
was 99.9%.
Example-11
[0105] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 0.20 g tetra ethyl orthosilicate
in 100 ml dry benzene. The sample was dried after 5 hrs by evaporating
benzene under reduced pressure. The tetra ethyl ortho silicate species
deposited on the solid external surface was converted into silica
by calcinations of the zeolite at 550.degree. C. A known amount
of the sample was activated at 400.degree. C. under vacuum and adsorption
measurements were carried out as described earlier. In situ X-ray
powder diffraction measurements at various temperatures up to 850.degree.
C. shows that the adsorbent has high thermal and hydrothermal stability.
Methanol, ethanol and water adsorption capacity values are 5.12%,
4.31% and 22.06% respectively and are given in Table 1. 5.0 g of
the adsorbent in Example-7 was filled in a column and activated
at 400.degree. C. by passing 99.5% pure nitrogen gas to remove the
adsorbed molecules. The activated adsorbent was cooled to room temperature
under inert atmosphere. 25 ml ethyl alcohol-water mixture containing
95% ethyl alcohol was passed through the column and the product
was analysed by Gas Chromatography and was found that the purity
of the product ethanol was 99.9%.
Example-12
[0106] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 0.25 g tetra ethyl orthosilicate
in 100 ml dry cyclohexane. The sample was dried after 5 hrs by evaporating
cyclohexane under reduced pressure. The tetra ethyl ortho silicate
species deposited on the external solid surface was converted into
silica by calcinations of the zeolite at 600.degree. C. A known
amount of the sample was activated at 400.degree. C. under vacuum
and adsorption measurements were carried out as described earlier.
In situ X-ray powder diffraction measurements at various temperatures
up to 850.degree. C. shows that the adsorbent has high thermal and
hydrothermal stability. Methanol, ethanol and water adsorption capacity
values are 2.51%, 1.84% and 21.87% respectively and are given in
Table 1. 5.0 g of the adsorbent was filled in a column and activated
at 450.degree. C. by passing 99.5% pure nitrogen gas to remove the
adsorbed molecules. The activated adsorbent was cooled to room temperature
under inert atmosphere. 25 ml methanol-water mixture containing
94% methanol was passed through the column and the product was analysed
by Gas Chromatography and was found that the purity of the product
methanol was 99.9%.
Example-13
[0107] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 0.25 g tetra methyl orthosilicate
in 100 ml dry cyclohexane. The sample was dried after 5 hrs by evaporating
cyclohexane under reduced pressure. The tetra methyl ortho silicate
species deposited on the external solid surface was converted into
silica by calcinations of the zeolite at 550.degree. C. A known
amount of the sample was activated at 400.degree. C. under vacuum
and adsorption measurements were carried out as described earlier.
In situ X-ray powder diffraction measurements at various temperatures
up to 850.degree. C. shows that the adsorbent has high thermal and
hydrothermal stability. Methanol, ethanol and water adsorption capacity
values are 2.62%, 1.91% and 22.12% respectively and are given in
Table 1. 5.0 g of the adsorbent in was filled in a column and activated
at 400.degree. C. by passing 99.5% pure nitrogen gas to remove the
adsorbed molecules. The activated adsorbent was cooled to room temperature
under inert atmosphere. 20 ml n-propyl alcohol-water mixture containing
93% n-propyl alcohol was passed through the column and the product
was analysed by Gas Chromatography and was found that the purity
of the product n-propyl alcohol was 99.9%.
Example-14
[0108] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 0.25 g tetra ethyl orthosilicate
in 100 ml dry xylene. The sample was dried after 5 hrs by evaporating
xylene under reduced pressure. The tetra ethyl ortho silicate species
deposited on the external solid surface was converted into silica
by calcinations of the zeolite at 550.degree. C. A known amount
of the sample was activated at 400.degree. C. under vacuum and adsorption
measurements were carried out as described earlier. In situ X-ray
powder diffraction measurements at various temperatures up to 850.degree.
C. shows that the adsorbent has high thermal and hydrothermal stability.
Methanol, ethanol and water adsorption capacity values are 2.42%,
1.73% and 21.58% respectively and are given in Table 1. 5.0 g of
the adsorbent was filled in a column and activated at 400.degree.
C. by passing 99.5% pure nitrogen gas to remove the adsorbed molecules.
The activated adsorbent was cooled to room temperature under inert
atmosphere. 20 ml isopropyl alcohol-water mixture containing 92%
isopropyl alcohol was passed through the column and the product
was analysed by Gas Chromatography and was found that the purity
of the product isopropyl alcohol was 99.9%.
Example-15
[0109] 10.0 g of the solid [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2).sub.12-
.wH.sub.2O] was activated at 400.degree. C. to remove the water
adsorbed in the zeolite and stirred with 0.30 g titanium iso-propoxide
in 100 ml dry xylene. The sample was dried after 5 hrs by evaporating
xylene under reduced pressure. The titanium iso propoxide species
deposited on the external solid surface was converted into titania
by calcinations of the zeolite at 550.degree. C. A known amount
of the sample was activated at 400.degree. C. under vacuum and adsorption
measurements were carried out as described earlier. Methanol, ethanol
and water adsorption capacity values are 2.52%, 1.93% and 22.15%
respectively and are given in Table 1.
Example-16
[0110] 10.0 g of the solid powder [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2)-
.sub.12.wH.sub.2O] was activated at 400.degree. C. to remove the
water adsorbed in the zeolite and stirred with 0.35 g zirconium
iso propoxide in 100 ml dry xylene. The sample was dried after 5
hrs by evaporating xylene under reduced pressure. The zirconium
iso propoxide species deposited on the solid surface was converted
into zirconia by calcinations of the zeolite at 550.degree. C. A
known amount of the sample was activated at 400.degree. C. under
vacuum and adsorption measurements were carried out as described
earlier. Methanol, ethanol and water adsorption capacity values
are 2.65%, 1.99% and 21.91% respectively and are given in Table
1.
Example-17
[0111] 10.0 g of the solid powder [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2)-
.sub.12.wH.sub.2O] was activated at 400.degree. C. to remove the
water adsorbed in the solid and stirred with 0.20 g aluminium iso
propoxide in 100 ml dry xylene. The sample was dried after 5 hrs
by evaporating xylene under reduced pressure. The aluminium iso
propoxide species deposited on the zeolite surface was converted
into alumina by calcinations of the zeolite at 500.degree. C. A
known amount of the sample was activated at 400.degree. C. under
vacuum and adsorption measurements were carried out as described
earlier. Methanol, ethanol and water adsorption capacity values
are 2.69%, 2.42% and 21.07% respectively and are given in Table
1.
Example-18
[0112] 10.0 g of the solid powder [Na.sub.12(AlO.sub.2).sub.12.(SiO.sub.2)-
.sub.12.wH.sub.2O] was activated at 400.degree. C. to remove the
water adsorbed in the zeolite and stirred with 0.25 g tetra methyl
orthosilicate in 100 ml dry xylene. The sample was dried after 5
hrs by evaporating xylene under reduced pressure. The tetra methyl
ortho silicate species deposited on the zeolite surface was converted
into silica by calcinations of the zeolite at 650.degree. C. A known
amount of the sample was activated at 400.degree. C. under vacuum
and adsorption measurements were carried out as described earlier.
In situ X-ray powder diffraction measurements at various temperatures
up to 850.degree. C. shows that the adsorbent has high thermal and
hydrothermal stability. Methanol, ethanol and water adsorption capacity
values are 2.57%, 1.82% and 21.43% respectively and are given in
table 1. 5.0 g of the adsorbent in was filled in a column and activated
at 400.degree. C. by passing 99.5% pure nitrogen gas to remove the
adsorbed molecules. The activated adsorbent was cooled to room temperature
under inert atmosphere. 25 ml ethyl alcohol-water mixture containing
95% ethyl alcohol was passed through the column and the product
was analysed by Gas Chromatography and was found that the purity
of the product ethanol was 99.9%.
[0113] The adsorption capacity and selectivity of all the 18 adsorbent
samples are enumerated in Table-1. |