WO1989000983A1 - Preparation of titanium ceramic membranes - Google Patents
Preparation of titanium ceramic membranes Download PDFInfo
- Publication number
- WO1989000983A1 WO1989000983A1 PCT/US1988/002537 US8802537W WO8900983A1 WO 1989000983 A1 WO1989000983 A1 WO 1989000983A1 US 8802537 W US8802537 W US 8802537W WO 8900983 A1 WO8900983 A1 WO 8900983A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- titanium
- water
- solution
- gel
- membranes
- Prior art date
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- 239000012528 membrane Substances 0.000 title claims abstract description 58
- 239000010936 titanium Substances 0.000 title claims abstract description 41
- 229910052719 titanium Inorganic materials 0.000 title claims abstract description 36
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 title claims abstract description 35
- 239000000919 ceramic Substances 0.000 title claims abstract description 26
- 238000002360 preparation method Methods 0.000 title description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims abstract description 26
- 125000005233 alkylalcohol group Chemical group 0.000 claims abstract description 7
- 238000005245 sintering Methods 0.000 claims abstract description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 13
- -1 titanium alkoxide Chemical class 0.000 claims description 8
- LLZRNZOLAXHGLL-UHFFFAOYSA-J titanic acid Chemical compound O[Ti](O)(O)O LLZRNZOLAXHGLL-UHFFFAOYSA-J 0.000 claims description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 5
- 229910017604 nitric acid Inorganic materials 0.000 claims description 5
- 150000004703 alkoxides Chemical class 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 239000001301 oxygen Substances 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- 239000002244 precipitate Substances 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 2
- 239000004408 titanium dioxide Substances 0.000 claims description 2
- 125000004429 atom Chemical group 0.000 claims 1
- 125000004432 carbon atom Chemical group C* 0.000 claims 1
- 239000000499 gel Substances 0.000 abstract description 37
- 230000007062 hydrolysis Effects 0.000 abstract description 13
- 238000006460 hydrolysis reaction Methods 0.000 abstract description 13
- 239000002904 solvent Substances 0.000 abstract description 6
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 235000019441 ethanol Nutrition 0.000 description 11
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 10
- 230000008569 process Effects 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 8
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000010304 firing Methods 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000011148 porous material Substances 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 230000001427 coherent effect Effects 0.000 description 3
- 239000000084 colloidal system Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000000151 deposition Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000000543 intermediate Substances 0.000 description 2
- 238000001935 peptisation Methods 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000006116 polymerization reaction Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 2
- 230000004580 weight loss Effects 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 239000012901 Milli-Q water Substances 0.000 description 1
- 229910011011 Ti(OH)4 Inorganic materials 0.000 description 1
- LCKIEQZJEYYRIY-UHFFFAOYSA-N Titanium ion Chemical compound [Ti+4] LCKIEQZJEYYRIY-UHFFFAOYSA-N 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 125000003158 alcohol group Chemical group 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 229920000592 inorganic polymer Polymers 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 230000000813 microbial effect Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 150000002902 organometallic compounds Chemical class 0.000 description 1
- 125000002524 organometallic group Chemical group 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical class [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910002076 stabilized zirconia Inorganic materials 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 238000004659 sterilization and disinfection Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 230000003313 weakening effect Effects 0.000 description 1
- 229910009112 xH2O Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0079—Manufacture of membranes comprising organic and inorganic components
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/02—Inorganic material
- B01D71/024—Oxides
- B01D71/0271—Perovskites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0039—Inorganic membrane manufacture
- B01D67/0048—Inorganic membrane manufacture by sol-gel transition
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0004—Organic membrane manufacture by agglomeration of particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0004—Organic membrane manufacture by agglomeration of particles
- B01D67/00041—Organic membrane manufacture by agglomeration of particles by sintering
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/02—Inorganic material
- B01D71/022—Metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/02—Inorganic material
- B01D71/024—Oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/04—Oxides; Hydroxides
- C01G23/047—Titanium dioxide
- C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/08—Specific temperatures applied
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/08—Specific temperatures applied
- B01D2323/081—Heating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/12—Specific ratios of components used
Definitions
- the present invention relates to the preparation of ceramic membranes, and, in particular, relates to the reliable and successful production of both particulate and polymeric titanium ceramic membranes and coatings.
- Ceramic membranes are used currently in industry and science for a variety of processes and purposes, the most common of which is separations. While organic membranes are most' often used for separation processes, ceramic membranes have had increasing popularity because of several advantages which they offer over organic membranes. Ceramic membranes have a greater chemical stability since they are resistant to organic solvents, chlorine, and extremes of pH. Ceramic membranes are also stable at very high temperatures which allows for efficient sterilization of process equipment and pharmaceutical equipment often not possible with organic membranes. Because ceramic membranes are inorganic they are generally quite stable to microbial or biological degradation which can occasionally be a problem with organic membranes. Ceramic membranes are also mechanically very stable even under high pressures. The temperature, chemical, and mechanical stability ot ceramic membranes allows them to be cleaned more effectively than other less durable membrane compositions.
- a process preparing either particulate or polymeric titania ceramic membranes includes the steps of preparing a colloidal solution containing a titanium organic salt with a specific ratio between water and titanium concentrations in the colloid so as to determine whether the resulting membrane is either particulate or polymeric, adding to the colloidal solution an alkyl alcohol, tightly controlling the pH of the colloid, and controlling the sintering temperature of the gel created from the colloid as it is sintered into a ceramic so as to prevent cracking of the resulting membrane.
- the present invention is also summarized in that the teaching of the construction of an inorganic titanium polymeric membrane.
- the present invention is directed to the preparation of membranes of titanium oxides.
- the first variation involves the gellation of a colloidal sol. This first variation utilizes a type of gel that is generally particulate but which can be formed in a coherent bulk if the processing variables are controlled carefully and can result in a consistent and uniform membrane after gellation.
- the second variation in this method involves the hydrolysis of an organometallic titanium compound to form a soluble intermediate compound which then condenses into the inorganic titanium polymer.
- the preparation of such titanium ceramic membranes proceeds through a sol-gel preparation procedure.
- a titanium alkoxide is dissolved in alcohol and hydrolysized, totally or partially with water.
- the hydrolysis and peptization results in a colloidal suspension, or sol.
- the sol is then evaporated to leave a semi-solid or gel.
- the gel may be formed on a substrated or formed in a self-supporting shape.
- the gel is sintered by firing at high temperature into a ceramic.
- the first is the ratio of water to titanium in the colloidal formation so that the gel is properly formed.
- the second criteria is the proper selection of an alcohol solvent for the hydrolysis step.
- the third consideration is the tight controlling of the pH of the colloidal mixture.
- the fourth consideration is an upper limit upon the sintering temperatures to which the resultant gels are exposed during firing.
- the chemical reaction can be characterized as commencing with the hydrolysis of titanium organometallic compounds at room temperature.
- a typical reaction is:
- the above reaction proceeds most favorably if the water is tightly constrained. Therefore, it is first appropriate to dissolve the titanium tetraisopropoxide in a non-aqueous solvent.
- the most desirable solvents are organic alkyl alcohols different from the alkyl radical in the organometallic compound.
- isopropanol may be utilized, but ethyl or methyl alcohol are preferred.
- Water may then be added in increments while the solution is stirred. The hydrolysis will therefor proceed under controlled conditions resulting in a titanium hydroxide precipitant.
- the titanium hydroxide precipitant may then be peptized with appropriate amounts of HNO 3 .
- This step converts the precipitant into a highly dispersed, stable, colloidal solution.
- This suspension is maintained by stirring and then may be slowly gelled over time by water evaporation under constant relative humidity at room temperature. If desired, the slurry may also be heated for a time period of up to twelve hours.
- the result is a gel which may be solidified in a number of ways.
- the gel may be solidified onto a support, such as glass, by dipping the support into the gel, in which it is coated, and then drying and firing the gel coating on the support.
- the gel may be poured into suitable containers without supports as well. In either event, the resulting sol needs to be fired at the temperature not to exceed 500° C to form the stable particulate membrane.
- the starting material which is convenient is titanium tetraisopropoxide or other similar alkoxide compounds of titanium.
- the polymeric network is to be formed by oxide bridges. Only some soluble species developed during partial hydrolysis of the metal alkoxide are useful for further polymerization. This creates a difficulty since these alkoxide intermediates tend to hydrolyze rapidly in excess water producing titanium hydroxide precipitant. Therefore the amount of water must be even more tightly controlled for polymeric membrane formation.
- the process thus begins by hydrolysis in a very small quantity of water in alcohol solution.
- the alcohol should be selected to be an alkyl alcohol which is different in its radical from the radical in the organometallic beginning material.
- titanium dioxide not be allowed to precipitate. Since TiO 2 particles are isoelectric at a pH of 5.8, lower pH values are appropriate. It has been found that holding the pH of the hydrolysis step to near 2 will prevent the TiO 2 from precipitating during hydrolysis formulation. This reaction may be characterized as follows:
- x will be less than 4.
- Such partially hydrolyzed products which are soluble in the alcohol medium will immediately condense to form polymeric chains through condensation of the oxygen bridges as follows:
- x 1 is less than x
- y 1 is less than y
- z equals (4-(x 1 + y 1 ))/2.
- the result of this polymeric process is a gel which forms as a distinct phase in the otherwise liquid medium, and which shrinks with time as it expels the excess liquid. If exposed to air, the alcohol solvent will evaporate rapidly causing the gel to crack as a result of rapid shrinkage. If the gelling time is allowed to proceed over several hours, a monolithic and crack-free gel will result.
- This gel can be fired at temperatures up to 500° C without a resulting unacceptable number of cracks being formed.
- This polymeric gel membrane can also be formed on a ceramic or glass support or alternatively can be formed into a self-supporting membrane by deposition upon a surface or drying from a colloidal mix and later firing.
- Titanium tetraisopropoxide was obtained from Aldridge Chemical Company. Water used in the reactions was de-ionized using a Milli-Q water purification system from Milliport Corporation.
- the stable titanium sols can be best achieved if the mole ratio of free hydrogen ions (from the acid) to titanium molecules is between 0.1 and 1.0. This range can be expanded only in relatively dilute sol solutions such as those of Group B on the table. The reason for this is not completely understood but may relate to the increased interparticle distance in the more dilute solutions making aggregation more difficult than in concentrated sols. Only stable sols could be properly transformed by peptization into coherent transparent gels and thereafter into coherent titanium oxide membranes by protolysis.
- the concentration of the acid was found to effect the gelling volume.
- the gelling volume goes through a minimum when the acid concentration is about 0.4 moles of free protons per mole of titanium.
- the sols loose at least 4.5% of their original weight, depending upon the electrolyte concentration, to arrive at the gelling point.
- the sols must loose some additional 97.6% of their original weight in order to form a final solid gel. Heating the final gels in the sintering process results in a further weight loss of about 13.5% without destroying the internal gel structure. Sintering temperatures in excess of 500° C resulted in cracks in the resultant ceramics, but lower firing temperatures resulted in membranes with reasonably consistent porosity.
- Example 2 Polymeric Membranes A series of experiments were performed testing the parameters of water to titanium ratio on the preparation and features of polymeric titanium membranes made in accordance with this procedure.
- One of the critical parameters was determined to be the relative concentrations of water in titanium in the colloidal solution.
- the slow addition of the water, dissolved in alcohol, into a solution of titanium tetraisopropoxide dissolved in alcohol aided the success of the reaction.
- the need for the care in the amount of water and its slow addition arises from the tendency of the titanium alkoxide precursors to hydrolyze rapidly upon the addition of water producing titanium hydroxide which precipitates rapidly thereby not continuing to react with other molecules.
- *Gelling volume is represented by the height of sample in vial at gelling point. The initial height was 2.05 cm for every sample.
- the polymeric gels thus produced may be fired at temperatures up to 500° C without cracking. Microscopic examination of the polymeric surface reveals a relatively uniform surface without cracks in these membranes.
- the membranes have been formed both on substrates and free standing. It has been found for sintering temperatures in excess of 500° C that cracks and other forms of porosity develop in the membrane thereby weakening their integrity and uniformity.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing & Machinery (AREA)
- Inorganic Chemistry (AREA)
- Organic Chemistry (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Dispersion Chemistry (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Structural Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
- Catalysts (AREA)
Abstract
A procedure is disclosed for the reliable production of either particulate or polymeric titanium ceramic membranes by a highly constrained sol-gel procedure. The critical constraints in the procedure include the choice of alkyl alcohol solvent, the amount of water and its rate of addition, the pH of the solution during hydrolysis, and the limit of sintering temperature applied to the resulting gels.
Description
PREPARATION OF TITANIUM CERAMIC MEMBRANES
Field of the Invention The present invention relates to the preparation of ceramic membranes, and, in particular, relates to the reliable and successful production of both particulate and polymeric titanium ceramic membranes and coatings.
Description of the Prior Art Ceramic membranes are used currently in industry and science for a variety of processes and purposes, the most common of which is separations. While organic membranes are most' often used for separation processes, ceramic membranes have had increasing popularity because of several advantages which they offer over organic membranes. Ceramic membranes have a greater chemical stability since they are resistant to organic solvents, chlorine, and extremes of pH. Ceramic membranes are also stable at very high temperatures which allows for efficient sterilization of process equipment and pharmaceutical equipment often not possible with organic membranes. Because ceramic membranes are inorganic they are generally quite stable to microbial or biological degradation which can occasionally be a problem with organic membranes. Ceramic membranes are also mechanically very stable even under high pressures. The
temperature, chemical, and mechanical stability ot ceramic membranes allows them to be cleaned more effectively than other less durable membrane compositions.
The mechanism of operation and types of separations which can be achieved by ceramic membranes are discussed in general by Asaeda et al., Jour. of Chem. Eng. of Japan, 19:1, 72-77 (1986). At least one line of ceramic filters is currently on the market marketed under the trade name "Ceraflo" by the Norton Company of Worcester, Massachusetts.
While many of these characteristics seem to favor inorganic membranes over organic membranes, the use of these membranes in widespread commercial applications has been slow because of the difficulty in producing crack-free membrane which have defined pore size and distributions in desirable ranges. Some types of prior art inorganic membranes, such as the ultra-stabilized zirconia membranes made by depositing particles on a silica support are stable but have relatively large pore sizes which make them suitable only for very high molecular weight separations.
Significant effort has been extended in creating metal oxide membranes using aluminium. For example, it has been demonstrated that the use of sol-gel techniques allows the reproducible preparation of alumina ceramic membranes which may be supported or unsupported. Lenaars et al., Jour, of Membrane Science, 24, 261-270 (1985). By controlling various parameters of the process, it was demonstrated that reliable procedures can be developed for creating alumina ceramic membranes having relatively fine pores and a reliable size distribution of the pores.
The teachings in the art to date about the preparation of titania ceramic membranes have been limited. Most of the sol-gel teachings utilizing titanium have been aimed at preparing very thin particulate films because of their optical and corrosion resistance properties. However, the various parameters necessary for the reproducible and
consistent preparation of these or similar films has not previously been rigorously described in such a fashion that they are readily replicable.
Summary of the Invention The present invention is summarized in that a process preparing either particulate or polymeric titania ceramic membranes includes the steps of preparing a colloidal solution containing a titanium organic salt with a specific ratio between water and titanium concentrations in the colloid so as to determine whether the resulting membrane is either particulate or polymeric, adding to the colloidal solution an alkyl alcohol, tightly controlling the pH of the colloid, and controlling the sintering temperature of the gel created from the colloid as it is sintered into a ceramic so as to prevent cracking of the resulting membrane.
The present invention is also summarized in that the teaching of the construction of an inorganic titanium polymeric membrane.
It is an object of the present invention to provide a method for liably and reproducibly making both particulate and polymeric titanium ceramic membranes useful in a variety of applications and processes.
It is a further object of the present invention to define the parameters necessary for successful reproduction of this process.
It is another feature of the present invention in that the production of polymeric titanium films are created thereby providing an inorganic polymeric substance having potential utility for catalysis filtering or other applications.
Other objects, advantages, and features of the present invention will become apparent from the following specification.
Detailed Description of the Invention
The present invention is directed to the preparation of membranes of titanium oxides. There are two variations in the method as disclosed here. The first variation involves the gellation of a colloidal sol. This first variation utilizes a type of gel that is generally particulate but which can be formed in a coherent bulk if the processing variables are controlled carefully and can result in a consistent and uniform membrane after gellation. The second variation in this method involves the hydrolysis of an organometallic titanium compound to form a soluble intermediate compound which then condenses into the inorganic titanium polymer.
In general, the preparation of such titanium ceramic membranes proceeds through a sol-gel preparation procedure. A titanium alkoxide is dissolved in alcohol and hydrolysized, totally or partially with water. The hydrolysis and peptization (typically with HNO3) results in a colloidal suspension, or sol. The sol is then evaporated to leave a semi-solid or gel. The gel may be formed on a substrated or formed in a self-supporting shape. The gel is sintered by firing at high temperature into a ceramic.
For both particulate and polymeric titanium membranes, both of which involve the preparation of sols and gels which are then fired to achieve ceramic materials, there are four distinct variables which must be carefully controlled. The first is the ratio of water to titanium in the colloidal formation so that the gel is properly formed. The second criteria is the proper selection of an alcohol solvent for the hydrolysis step. The third consideration is the tight controlling of the pH of the colloidal mixture. The fourth consideration is an upper limit upon the sintering temperatures to which the resultant gels are exposed during firing.
For the formation of particulate membranes, the chemical reaction can be characterized as commencing with
the hydrolysis of titanium organometallic compounds at room temperature. Thus a typical reaction is:
Ti(iso-OC3H7)4 + 4H2O - Ti(OH)4 + 4C3H7OH
The above reaction proceeds most favorably if the water is tightly constrained. Therefore, it is first appropriate to dissolve the titanium tetraisopropoxide in a non-aqueous solvent. It has been found that the most desirable solvents are organic alkyl alcohols different from the alkyl radical in the organometallic compound. Thus in the above example isopropanol may be utilized, but ethyl or methyl alcohol are preferred. Water may then be added in increments while the solution is stirred. The hydrolysis will therefor proceed under controlled conditions resulting in a titanium hydroxide precipitant.
The titanium hydroxide precipitant may then be peptized with appropriate amounts of HNO3. This step converts the precipitant into a highly dispersed, stable, colloidal solution. This suspension is maintained by stirring and then may be slowly gelled over time by water evaporation under constant relative humidity at room temperature. If desired, the slurry may also be heated for a time period of up to twelve hours. The result is a gel which may be solidified in a number of ways. The gel may be solidified onto a support, such as glass, by dipping the support into the gel, in which it is coated, and then drying and firing the gel coating on the support. The gel may be poured into suitable containers without supports as well. In either event, the resulting sol needs to be fired at the temperature not to exceed 500° C to form the stable particulate membrane.
For the preparation of polymeric membranes, again the starting material which is convenient is titanium tetraisopropoxide or other similar alkoxide compounds of titanium. The polymeric network is to be formed by oxide bridges. Only some soluble species developed during
partial hydrolysis of the metal alkoxide are useful for further polymerization. This creates a difficulty since these alkoxide intermediates tend to hydrolyze rapidly in excess water producing titanium hydroxide precipitant. Therefore the amount of water must be even more tightly controlled for polymeric membrane formation. The process thus begins by hydrolysis in a very small quantity of water in alcohol solution. Again, the alcohol should be selected to be an alkyl alcohol which is different in its radical from the radical in the organometallic beginning material. As stated, it is particularly important that titanium dioxide not be allowed to precipitate. Since TiO2 particles are isoelectric at a pH of 5.8, lower pH values are appropriate. It has been found that holding the pH of the hydrolysis step to near 2 will prevent the TiO2 from precipitating during hydrolysis formulation. This reaction may be characterized as follows:
Ti(OR)4 + xH2O - Ti(OH)x(OR)4-x + xHOR
For partially hydrolyzed products in the above reaction, x will be less than 4. Such partially hydrolyzed products which are soluble in the alcohol medium will immediately condense to form polymeric chains through condensation of the oxygen bridges as follows:
Ti(OR)y(OH)x - TiOz(OR)yl (OH)xl + (y-yl)ROH
In this reaction, x1 is less than x, y1 is less than y and z equals (4-(x1 + y1))/2. In this fashion, a continuous inorganic polymer is formed of titanium atoms linked by the oxygen atoms.
The result of this polymeric process is a gel which forms as a distinct phase in the otherwise liquid medium, and which shrinks with time as it expels the excess liquid. If exposed to air, the alcohol solvent will evaporate rapidly causing the gel to crack as a result of
rapid shrinkage. If the gelling time is allowed to proceed over several hours, a monolithic and crack-free gel will result. This gel can be fired at temperatures up to 500° C without a resulting unacceptable number of cracks being formed. This polymeric gel membrane can also be formed on a ceramic or glass support or alternatively can be formed into a self-supporting membrane by deposition upon a surface or drying from a colloidal mix and later firing.
Example 1 Preparation of Particulate Membranes
Titanium tetraisopropoxide was obtained from Aldridge Chemical Company. Water used in the reactions was de-ionized using a Milli-Q water purification system from Milliport Corporation.
A series of hydrolysis and particle gel formation experiments were performed using a variety of pH levels and variations in the ratio between water concentration and titanium ion concentration. The results are summarized in Table 1 below.
S = Stable
NS = not stable, floccus appearance NP = not peptized completely
*Weight loss from original sol to solid gel, given as a percentage of the original sol weight.
From the above data, it is evident that the stable titanium sols can be best achieved if the mole ratio of free hydrogen ions (from the acid) to titanium molecules is between 0.1 and 1.0. This range can be expanded only in relatively dilute sol solutions such as those of Group B on the table. The reason for this is not completely understood but may relate to the increased interparticle distance in the more dilute solutions making aggregation more difficult than in concentrated sols. Only stable sols could be properly transformed by peptization into
coherent transparent gels and thereafter into coherent titanium oxide membranes by protolysis.
The concentration of the acid was found to effect the gelling volume. The gelling volume goes through a minimum when the acid concentration is about 0.4 moles of free protons per mole of titanium. The sols loose at least 4.5% of their original weight, depending upon the electrolyte concentration, to arrive at the gelling point. The sols must loose some additional 97.6% of their original weight in order to form a final solid gel. Heating the final gels in the sintering process results in a further weight loss of about 13.5% without destroying the internal gel structure. Sintering temperatures in excess of 500° C resulted in cracks in the resultant ceramics, but lower firing temperatures resulted in membranes with reasonably consistent porosity.
Example 2 Polymeric Membranes A series of experiments were performed testing the parameters of water to titanium ratio on the preparation and features of polymeric titanium membranes made in accordance with this procedure. One of the critical parameters was determined to be the relative concentrations of water in titanium in the colloidal solution. In addition to having a fixed limit on the ratio of water to titanium, it was also determined that the slow addition of the water, dissolved in alcohol, into a solution of titanium tetraisopropoxide dissolved in alcohol aided the success of the reaction. The need for the care in the amount of water and its slow addition arises from the tendency of the titanium alkoxide precursors to hydrolyze rapidly upon the addition of water producing titanium hydroxide which precipitates rapidly thereby not continuing to react with other molecules. These experiments are summarized in Table A which indicates that successful polymeric membranes can be
formed using initial ratios of water to titanium concentrations of up to 16 mole per mole.
*ratio of iso-C3H7OH to Ti.
The analysis of the experimental data shown in Table 2 also indicates that water concentration in the initial solution controls the viscosity of the sol. The more water there is in proportion to titanium in the original solution the more viscous the solution becomes. The limits of polymeric sol formation appear to be approximately 16 mole of water per mole of titanium to 2 mole of water per mole of titanium, indicating a range, expressed in weight, of from 3 to 12%. Of the gels
produced by these titanium sols, there appeared to be a transition when the mole of ratio of water to titanium was about 4. Above that level the gels are opaque while below that level the gels are transparent. The ratio of water concentration also had an effect upon gelling volume and gelling time. The experiments determining this criteria are summarized in Table 3 below.
*Gelling volume is represented by the height of sample in vial at gelling point. The initial height was 2.05 cm for every sample.
The choice of alcohol solvent which dilutes the reacting species also appears to affect the rates of hydrolysis in polymerization. It was found that the preferred and most successful alcohols to be used were alkyl alcohols different from the radical used in the reacting species. Thus, using titanium tetraisopropoxide, an ethyl alcohol solvent was preferred. Again, maintenance of low pH, preferably about 2, was necessary to prevent precipitation during hydrolysis.
The resulting titanium gels are quite different than other gels such as those formed by silicons. If titanium polymeric sols are placed in a closed container and aged for a time period of weeks, a monolithic crack-free gel forms and shrinks with time in the presence of expelled liquid. The sol thus evolves into a two-phase system, a crack-free gel, and the clearly separated expelled liquid phase.
The polymeric gels thus produced may be fired at temperatures up to 500° C without cracking. Microscopic examination of the polymeric surface reveals a relatively uniform surface without cracks in these membranes. The membranes have been formed both on substrates and free standing. It has been found for sintering temperatures in excess of 500° C that cracks and other forms of porosity develop in the membrane thereby weakening their integrity and uniformity.
Claims
1. A method of preparing a titanium ceramic membrane comprising the steps of: dissolving a titanium alkoxide in an alkyl alcohol wherein the alkyl alcohol has a different number of carbon atoms than the alkoxide radicals; adding to the solution a very limited quantity of water while maintaining a pH of about two so that a colloidal solution is formed; drying the colloidal solution to obtain a gel; and sintering the gel by heating to a temperature no higher than about 500° C.
2. A method as claimed in Claim 1 wherein the amount of water atoms is limited to less than 16:1 on a mole to mole ratio to titanium atoms in the solution.
3. A method as claimed in Claim 1 further including adding to the solution HNO3 to peptize the colloidal solution.
4. A method as claimed in Claim 1 wherein water is added sufficiently fast to precipitate titanium hydroxide, and wherein the precipitate is subsequently peptized with HNO3 to create a colloidal solution, and wherein the result is a particulate ceramic membrane.
5. A method as claimed in Claim 1 wherein the initial alcohol solution also includes HNO3 and wherein the rate at which water is added is limited so that substantially no titanium hydroxide precipitate is formed so that oxygen bridges between titanium atoms are formed so that the resulting membrane is a polymeric ceramic membrane.
6. A method as claimed in Claim 5 wherein the titanium alkoxide is between 3% and 12% by weight of the starting solution.
7. A method as claimed in Claim 1 wherein the alkoxide is tetraisopropoxide and the alcohol is ethanol.
8. A ceramic membrane of titanium dioxide characterized by extensive continuous polymeric oxygen bridges between the titanium atoms.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019890700535A KR960007372B1 (en) | 1987-07-27 | 1988-07-26 | Preparation of titanium ceramic membranes |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US7779987A | 1987-07-27 | 1987-07-27 | |
| US077,799 | 1987-07-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1989000983A1 true WO1989000983A1 (en) | 1989-02-09 |
Family
ID=22140118
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US1988/002537 WO1989000983A1 (en) | 1987-07-27 | 1988-07-26 | Preparation of titanium ceramic membranes |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0325653A4 (en) |
| JP (1) | JP3020241B2 (en) |
| KR (1) | KR960007372B1 (en) |
| AU (1) | AU2425288A (en) |
| CA (1) | CA1313886C (en) |
| WO (1) | WO1989000983A1 (en) |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0407181A1 (en) * | 1989-07-05 | 1991-01-09 | Wisconsin Alumni Research Foundation | Niobium-doped titanium membranes |
| US5137607A (en) * | 1990-04-27 | 1992-08-11 | Wisconsin Alumni Research Foundation | Reactor vessel using metal oxide ceramic membranes |
| US5223318A (en) * | 1990-08-06 | 1993-06-29 | Corning Incorporated | Titania substrates and fabrication |
| US5342431A (en) * | 1989-10-23 | 1994-08-30 | Wisconsin Alumni Research Foundation | Metal oxide membranes for gas separation |
| US5439624A (en) * | 1994-02-14 | 1995-08-08 | Wisconsin Alumni Research Foundation | Method for forming porous ceramic materials |
| US5468699A (en) * | 1992-07-30 | 1995-11-21 | Inrad | Molecular sieve - photoactive semiconductor membranes and reactions employing the membranes |
| US5487774A (en) * | 1993-11-08 | 1996-01-30 | Wisconsin Alumni Research Foundation | Gas phase fractionation method using porous ceramic membrane |
| EP1283068A1 (en) * | 2001-07-30 | 2003-02-12 | Saehan Industries, Inc. | Reverse osmosis membrane having excellent anti-fouling property and method for manufacturing the same |
| US6683023B2 (en) * | 2000-04-21 | 2004-01-27 | Showa Denko K.K. | Photocatalytic powder and polymer composition |
| US7896949B2 (en) | 2005-09-28 | 2011-03-01 | General Electric Company | Membranes for separation of carbon dioxide |
| KR20190066212A (en) | 2017-12-05 | 2019-06-13 | 단국대학교 천안캠퍼스 산학협력단 | Method of producing ceramics in low temperature using titanium gel and ceramics produced by the same method |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2820555B2 (en) * | 1991-07-09 | 1998-11-05 | 三菱重工業株式会社 | Titanium oxide catalyst for promoting photoreaction |
| JP5757038B2 (en) * | 2006-06-12 | 2015-07-29 | キャプティゲル アクチエボラグ | Metal oxide hydrogels and hydrosols, their manufacture and use |
-
1988
- 1988-07-26 EP EP19880908464 patent/EP0325653A4/en not_active Ceased
- 1988-07-26 JP JP63507695A patent/JP3020241B2/en not_active Expired - Lifetime
- 1988-07-26 KR KR1019890700535A patent/KR960007372B1/en not_active IP Right Cessation
- 1988-07-26 AU AU24252/88A patent/AU2425288A/en not_active Abandoned
- 1988-07-26 WO PCT/US1988/002537 patent/WO1989000983A1/en not_active Application Discontinuation
- 1988-07-27 CA CA000573216A patent/CA1313886C/en not_active Expired - Lifetime
Non-Patent Citations (4)
| Title |
|---|
| Journal of Materials Science, 12, issued June 1977, B.E. YOLDAS, "Preparation of Glasses and Ceramics from Metal-Organic Compounds", see pages 1203-1208. * |
| Journal of Meterials Science Letters 5, issued April 1986, K. KAMIYA et al, "Preparation of Ti02 Fibers by Hydrolysis and Polycondensation of Ti (0-i-C3H7)4, see pages 402-404. * |
| Treatise on Materials Science and Technology Vol. 22, issued July 1982, S. SAKKA, "Gel Method for Making Glass" see pages 132, 133, 136, 137, 142, 148 and 154-156. * |
| Yogyo-Kyokai-Shi, 95, issued February 1987, T. YOKO et al, "Photoelectrochemical Properties of Ti02 Films Prepared by the Sol-Gel Method, see pages 12-17. * |
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0407181A1 (en) * | 1989-07-05 | 1991-01-09 | Wisconsin Alumni Research Foundation | Niobium-doped titanium membranes |
| US5342431A (en) * | 1989-10-23 | 1994-08-30 | Wisconsin Alumni Research Foundation | Metal oxide membranes for gas separation |
| US5137607A (en) * | 1990-04-27 | 1992-08-11 | Wisconsin Alumni Research Foundation | Reactor vessel using metal oxide ceramic membranes |
| US5308454A (en) * | 1990-04-27 | 1994-05-03 | Wisconsin Alumni Research Foundation | Reactor process using metal oxide ceramic membranes |
| US5223318A (en) * | 1990-08-06 | 1993-06-29 | Corning Incorporated | Titania substrates and fabrication |
| US5712461A (en) * | 1992-07-30 | 1998-01-27 | Inrad | Molecular sieve--photoactive semiconductor membranes and reactions employing the membranes |
| US5468699A (en) * | 1992-07-30 | 1995-11-21 | Inrad | Molecular sieve - photoactive semiconductor membranes and reactions employing the membranes |
| US5487774A (en) * | 1993-11-08 | 1996-01-30 | Wisconsin Alumni Research Foundation | Gas phase fractionation method using porous ceramic membrane |
| US5610109A (en) * | 1994-02-14 | 1997-03-11 | Wisconsin Alumni Research Foundation | Porous ceramic material |
| US5639412A (en) * | 1994-02-14 | 1997-06-17 | Wisconsin Alumni Research Foundation | Substituted silica sol |
| US5712037A (en) * | 1994-02-14 | 1998-01-27 | Wisconsin Alumni Research Foundation | Substituted silica gel |
| US5439624A (en) * | 1994-02-14 | 1995-08-08 | Wisconsin Alumni Research Foundation | Method for forming porous ceramic materials |
| US6683023B2 (en) * | 2000-04-21 | 2004-01-27 | Showa Denko K.K. | Photocatalytic powder and polymer composition |
| US7335620B2 (en) | 2000-04-21 | 2008-02-26 | Showa Denko K.K. | Photocatalytic powder, photocatalytic slurry, and polymer composition, coating agent, photocatalytic functional molded article and photocatalytic functional structure using the powder |
| EP1283068A1 (en) * | 2001-07-30 | 2003-02-12 | Saehan Industries, Inc. | Reverse osmosis membrane having excellent anti-fouling property and method for manufacturing the same |
| US7896949B2 (en) | 2005-09-28 | 2011-03-01 | General Electric Company | Membranes for separation of carbon dioxide |
| KR20190066212A (en) | 2017-12-05 | 2019-06-13 | 단국대학교 천안캠퍼스 산학협력단 | Method of producing ceramics in low temperature using titanium gel and ceramics produced by the same method |
Also Published As
| Publication number | Publication date |
|---|---|
| KR890701493A (en) | 1989-12-20 |
| JP3020241B2 (en) | 2000-03-15 |
| CA1313886C (en) | 1993-02-23 |
| EP0325653A4 (en) | 1989-10-25 |
| KR960007372B1 (en) | 1996-05-31 |
| EP0325653A1 (en) | 1989-08-02 |
| JPH02500268A (en) | 1990-02-01 |
| AU2425288A (en) | 1989-03-01 |
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