WO2013164840A2

WO2013164840A2 - System and method for production of membrane

Info

Publication number: WO2013164840A2
Application number: PCT/IN2013/000145
Authority: WO
Inventors: Gajanan Bhimroaji Kunde; C.Anand Babu
Original assignee: Yadav Ganapati Dadasaheb Chemical Engineering Department, Institute Of Chemical Technology
Priority date: 2012-03-09
Filing date: 2013-03-12
Publication date: 2013-11-07
Also published as: WO2013164840A3

Abstract

System and method for production of membrane having high strength, enhanced thermal stability and chemical resistance comprising of at least two furnace plates, at least one heating coils encased in ceramic disc housing, metal sheet and base. Perforated ceramic discs of the invention are mounted on a movable stand and equipped with heating mantle, insulation and is encased in a metallic cover. The pores present on ceramic disc not only helps in dissipation of gases emanating from heating of wet metal oxide gel diaphragms but also conducts the heat from heating coil to it. The pores in the ceramic disc plays dual role i.e. exit of trapped water and other organic matter as well as entry of heat towards the wet gel films for faster drying. On the other hand the perforated ceramic disc has a major role to play in preventing the deformation likely to occur during sintering of semidried metal oxide gel diaphragms by putting a vertical pressure and controlling its morphology as the heating progresses towards high temperature in controlled manner. By means of this setup the semidried gel diaphragms are calcined at high temperatures to get the desired flawless plain porous ceramic membranes and all operations are done smoothly.

Description

TITLE: SYSTEM AND METHOD FOR PRODUCTION OF MEMBRANE

FIELD OF INVENTION

The present invention is related to system for production of membrane having high strength, enhanced thermal stability and chemical resistance. Further invention is related to method for production of membrane having high strength, enhanced thermal stability and chemical resistance. Present system and method lower the cost of manufacturing and provides wide range of pore sizes for membrane. Apparatus along with method offer the better option and an advanced technology in the field of membrane production as membrane produced is with uniformity without any deformation and cracking.

BACKGROUND OF THE INVENTION

Porous inorganic solid material is studied widely after seventies. The important aspects of this class of material are their large surface area and wide range of pore structures. This quality of inorganic materials can be effectively used in catalysis and separation processes. Inorganic membranes can be most commonly used in separation processes. It is true that organic membranes are in wide application in separation processes but inorganic membranes offer special properties such as chemical inertness to most of organic solvents, high temperature application, and resistance to extreme pH and biological degradation. This makes them suitable candidate for industrial applications.

The quality of the product in majority of the cases depends upon the sintering process adopted. The sintering step consumes major part of the energy used in the industries. Besides this the technology required for sintering ceramic is intricate and costly.

Further it is known that alumina based inorganic membranes are having high strength, enhanced thermal stability and chemical resistance. But to lower the cost of manufacturing and to get wide range of pore sizes of membranes, sol-gel route can offer better option and technology.

The present invention shows production of ceramic membrane by sol-gel method which is most economical than conventional method. Conventional furnaces are not really useful for ceramic material made by sol-gel route. We need to innovate a new set of equipments and protocols to handle the material that coming out of sol-gel synthesis. The present effort is in this direction of overcoming the shortfalls of conventional furnaces during sintering of semidried diaphragms prepared by sol-gel method.

Porous inorganic solid material is studied widely after seventies. The important aspect of this class of material is their large surface area and wide range of pore sizes. This quality of inorganic materials can be effectively used in catalysis and separation processes. Inorganic membranes can be most commonly used in separation processes. It is true that organic membranes are in wide application in separation processes but inorganic membranes offer special properties such as chemical inertness to most of organic solvents, high temperature application, and resistance to extreme pH and biological degradation. This makes them suitable candidate for industrial applications.

It is known that alumina based inorganic membranes are having high strength, enhanced thermal stability and chemical resistance. To lower the cost of manufacturing and get wide range of pore sizes of alumina membranes, sol-gel route offers the best option and an advanced technology. Sol-gel technology has emerged as a source of wide range of pore sizes with great uniformity. It makes possible the synthesis of inorganic membranes at low temperature by hydrolysis and peptization of metal oxide^' precursor in a solvent. It is totally different from the process of sintering and compressing powders at high temperature to manufacture ceramic membranes.

U.S. Pat. No. 4,416,623 by Takahashi discloses muffle furnace with elongated muffle with different heating zones. The furnace is useful in heating of material in specific temperature zones and maintains the inner atmosphere at high purity.

U.S. Pat. No. 4,568,279 by Logue et al. discloses the invention relating to flame heated muffle furnace. The furnace treats ceramic articles on continuous basis as it passes through the furnace muffle. The flame do not come in contact with product under treatment; it helps in maintaining the purity of the product.

U.S. Pat. No. 4,919,867 by onings et al. discloses furnace for sintering ceramic articles on continuous basis. The furnace comprises of rotatable tube, through which the ceramic articles are guided through furnace. U.S. Pat. No. 5,762,862, by Okinaka et al. discloses a method of sintering ceramics using furnace for ceramic manufacture. The invention is useful in minimizing the defects such as sticking, deformation, breakages and surface abrasions in ceramic articles during sintering processes.

For the method, most of the work in this area is done on hydrolysis and peptization of metal alkoxides in a solvent by using peptizing agents such as HCl, HN0₃, acetic acid or salts of acidic or basic electrolytes etc. S.S.Kistler in 1940, describes the synthesis of dry aerogel from colloidal solution of various compounds of inorganic and organic substances in U.S. patent No 2, 188,007.

An article "Alumina Sol Preparation from Alkoxides", by Yoldas in American Ceramic society bulletin Vol.54, No.3 (1975) pages 289-290, depicts detailed process of hydrolysis of aluminiumalkoxide precursor followed by acid peptization of sol and further digestion of it at 80°C. The sol is further gelled by evaporating the solvent and can be dried to obtain an aerogel. Aerogel can be further calcined to obtain alumina porous monoliths.

The US Pat.No. 3,944,658 of Yoldas discloses a process of preparation of transparent activated non-particulate alumina and methods of preparing clear colloidal sol.

The U.S. Pat.No. 4,532,072 of Segal discloses preparation of alumina sol by hydrolysis of alumina alkoxide in stoichiometric proportion. Its peptization is done by using peptizing agent in an aqueous medium to produce alumina sol.

The US Pat.No. 4,465,739 by Yoldas, introduces the preparation of clear aluminum alkoxide solution by hydrolysis with water in presence of alcohol. On further heating the mixture at 60°C, a clear sol is formed. The sol is further converted to alumina glass by heating up to 500°C.

The US Pat.No. 4,801,399 by Clark et al. disclose the use of inorganic salts as catalyst in preparation of metal oxide sol by sol-gel method. The metal alkoxides are hydrolyzed by using excess amount of water. The peptization of the sol is done by metal salts as peptizing agents. The pore size obtained is in the range of 0.0001 to 10 microns in diameter. The US Pat.No.5, 104,539 by Anderson discloses effective use of sol-gel process for production of metal oxide porous ceramic membranes with small pore size in the range of 5 to 40 Angstroms. The U.S. Pat.No. 5,208, 190 by Anderson et al disclose the method of preparing alumina microporous ceramic membranes by sol gel method. The mean pore size is less than 100 Angstroms. Y. Mizushima et al discusses the formation of truly monolithic aerogels of alumina with highest porosities of 95 percent (Journal of Non-crystalline Solids 167(1994) 1. The US Pat.No. 5,591,380 by Wright disclose the preparation of alumina-silica sol-gel composites. The US Pat.No.6, 620,458 B2 by Poco et al, discloses a two step sol-gel process for synthesis of monolithic alumina aerogels.

The review published by Kobayashi et al in The Journal of Material Science 40 (2005) 263- 283 describes the developments in the area of alumina film by sol-gel method. Various applications of alumina films are also discussed. It states that alumina films are amorphous and are having separation ability and can act as effective substrate for various doping substances. Alumina matrix can enhance catalytic power of the dopants.

The warping phenomenon is observed during drying of the gel plate. The gel film tends to lift upwards in the direction of evaporation and then curve in opposite direction as the drying proceeds in the final stage (JNS 91, 1987, 83-100, drying gels— III Warping plate- George Scherer). U.S. Pat. No.6, 383,443 BI by Jeng et al describes a sol-gel process for synthesis of alpha alumina based materials. It describes that besides warping; monolithic alumina gels undergo cracking during drying. It can be prevented by maintaining proper temperature, humidity and drying methods. The polymeric drying molds are coated with silicon oil before pouring the gel. The resultant microstructure of alumina consists of average pore size distribution and can be used industrially.

The above prior arts disclose the furnaces used in heating or sintering the ceramic articles by conventional method, but none of these have acted in arresting the curvature of alumina thin films during drying and calcinations while producing the required dimensional structure of alumina. It does not satisfy the need of dimensional stability of ceramic articles produced by sol-gel processes. The synthesis of ceramic membrane by sol-gel method involves controlled heating, shaping and maintaining the compactness of structure during the preheating and sintering processes. The water and other organic matter evaporate from the ceramic semidried membrane diaphragms leaving behind the pores in the body of the membrane diaphragm. Thus there is a need to address this problem of curving of alumina films during drying and calcination so that the exact required size of porous monoliths of alumina films can be prepared. To meet the challenges of the sol-gel process we need to devise such a furnace which not only maintains the shape of the ceramic articles but also creates the porous structures, as and when required.

Further all the above literature illustrates the synthesis of alumina sol-gel and further drying of it by various methods, but none of these have acted in arresting the curvature of alumina thin films during drying and calcinations to producing the required dimensional structure of alumina. It is observed that though the cracking problem can be arrested up to some extent by employing the above mentioned procedures but none of the methods have given the practical examples of synthesizing unsupported alumina membrane /thin films of required sizes.

Objective of the invention

The objective of this invention is to make a furnace in which the ceramic membranes to be calcined should not only have dimensional stability but also not cause cracking. Moreover the removal of trapped volatile matter must take place in such a controlled manner which does not cause any deformation to the membrane structure. The formation of pores in membrane body is due to decomposition of water and volatile matter.

Another objective of the present invention is to provide method for production method for membrane having high strength, enhanced thermal stability and chemical resistance. Hence some of the objectives of the present invention can be given as follows

Yet another objective of present invention is to provide system compatible with a method wherein production of membrane results in membrane having high strength, enhanced thermal stability and chemical resistance.

Other objective of the present invention is to provide a method for production of membrane having high strength, enhanced thermal stability and chemical resistance.

Yet another objective is to provide production method that lowers the cost of manufacturing and provides wide range of pore sizes for membrane. One of the objectives of the present invention is to produce a membrane with uniformity and without any deformation and cracking so that it can be better option and an advanced technology in the field of membrane.

One of the objectives of the present invention that to obtain plain, curve free, crack free ceramic membrane by sol-gel method

One of the objectives of the present invention is that to provide simple, economical, improved casting and drying techniques for the manufacture of alumina membrane.

One of the objectives of the present invention is that to employ different metal oxides in production method for ceramic membranes and monoliths by sol-gel method

One of the objectives of the present invention that to optimize production method for ceramic membranes /films particularly by sol-gel method

Yet another objective of the present invention is that to provide ceramic membranes of different dimensions.

Another objective of present invention is to obtain a wide range of pore size distribution in alumina ceramic membranes and other metal oxide membranes.

SUMMARY OF THE INVENTION

In present invention is to make a furnace in which the ceramic membranes to be calcined should not only have dimensional stability but also not cause cracking. Moreover the removal of trapped volatile matter must take place in such a controlled manner which does not cause any deformation to the membrane structure. The formation of pores in membrane body is due to decomposition of water and volatile matter.

In system of invention wherein production of membrane having high strength, enhanced thermal stability and chemical resistance comprising of at least two furnace plates, at least one heating coils encased in ceramic disc housing , metal sheet and base wherein furnace plates are upper and lower plates fitted to the stand and can either be fixed or moved up and down on it by means of locks and slide arrangement.

Also in method for production of membrane having high strength, enhanced thermal stability and chemical resistance comprising steps of forming gel, casting of gel, heating of casted gel to form semidried film, sizing of semidried gel film, drying of semidried gel films between two porous transparent surfaces as sandwich under visible light source and further calcinations of dried film to obtained membrane; characterized that drying is carried out in between two porous transparent surfaces as sandwich under visible light source. In forming of gel can be carried out by veriaous proceses like hydrolysis and peptization or combination.

For specific method for production of ceramic membrane having high strength, enhanced thermal stability and chemical resistance can comprise steps like forming gel by hydrolysis of aluminium alkoxide is concentrated by evaporating the solvent to obtain a viscous, free flowing gel; drying viscous gel on the ceramic coated metallic surface/mold; sizing of semidried gel film, cutting it in required size and dimensions; drying by keeping semidried gel film between two porous transparent glass plates under the visible light; heating dried gel film between two porous ceramic surfaces as sandwiched assembly up to the temperature range of 200°C to 2000°C.

BRIEF DESCRIPTION OF THE DRAWING:

The preferred embodiments of the present invention such as objects, features and advantages, will be readily apparent from the following description in conjunction with complimentary drawings. The modification and variation can be brought out by without leaving mettle and extent of innovative idea of the disclosure and in it,

DRAWING 1 is a perspective view of the porous disc furnace embodying this invention.

DRAWING 2 is front elevation of the furnace.

DRAWING 3 is top elevation of the furnace.

DRAWING 4 is sectional view of furnace plate.

DRAWING 5 is a view of heating element of the furnace.

DRAWING 6 is a view of porous ceramic disc.

DRAWING 7 is a view of sintered alumina membrane diaphragm. DRAWING 8 is a view of Thermo Gravimetric Analysis (TGA) graph of alumina ceramic membrane.

DRAWING 9 is a view of BET adsorption graph of sintered alumina membrane.

DRAWING- 10 : Contact angle analysis of various concentration of aluminium alkoxide hydrogel on glass and Ceramic coated metal surface.

STATEMENT OF INVENTION:

The present invention relates to a System for production of membrane having high strength, enhanced thermal stability and chemical resistance comprising of at least two furnace plates, at least one heating coils encased in ceramic disc housing , metal sheet and base. The furnace plates are upper and lower plates fitted to the stand and can either be fixed or moved up and down on it by means of locks and slide arrangement and furnace plate has at least one disc of ceramic or metal oxide with ceramic disc holder, also disc of ceramic or metal oxide is porous and disc of ceramic has vents on all over the circumference, disc of ceramic or metal oxide has pores with different diameter. Each pore has different diameter at plane. The base consists of all electrical circuits and wiring and can be connected to power source with digital display unit for the temperature controller fitted on the rectangular base.

System for production of membrane having high strength, enhanced thermal stability and chemical resistance comprises of two upper and lower furnace plates which are covered on one side i.e. upper plate on upper side and lower plate on lower side by metal sheet, the stand (8) for mounting furnace plates (1, 4), the base (12) , socket holder for upper and lower ceramic disc(17), rectangular base (12) , assembly lock (1 1) for mounting and operating by slide and lock arrangement (5) to the assembly lock can be fixed on the upper plate, heating source with temperature controller for temperature programmed by PID controller with digital display (6) fixed on base (12) .The two upper and' lower furnace plates has heating coil is circulated all over the plate in a manner in which it provides uniform heating to the porous ceramic plate. Further two upper and lower furnace plates has heating metal coils (14) are connected to electrical terminals (15) and the coils are well fitted in the grooves (16) present on one side of the porous ceramic plate. The ceramic disc (17) holds the ceramic plate along with the assembly. Heating source with temperature controller for controlling temperature during heating and cooling of the device can be detected by thermocouple (18) and can be controlled by PID controller (6). Porous ceramic disc (2) has pores all over the area of the plate also it has pores (19) with diameter in the range 10 to 100 micron, Porous with average pore diameter 7.8 nm.

Method of operating system for production of membrane comprising steps of

inserting semidried ceramic membrane film as sandwich in between two furnace plates; lowering plates gently on each other without damaging ceramic film;

locking assembly by locking arrangement provided on stand;

mounting total compilation on the rectangular base;

calcinating of the semidried ceramic membrane circuits by switching on power source; controlling temperature of assembly by temperature control panel (6) on rectangular base to create a temperature profile of the furnace in such a manner that the circular alumina diaphragms gets heated up from room temperature to 2000°C to set with ramp rate of 1°C per minute. Cooling temperature of assembly at cooling rate 1°C per minute.

Method for production of membrane having high strength, enhanced thermal stability and chemical resistance comprising steps of forming gel, casting of gel, heating of casted gel to form semidried film, sizing of semidried gel film, drying of semidried gel films between two porous transparent surfaces as sandwich under visible light source and further calcinations of dried film to obtained membrane; characterized that drying is carried out in between two porous transparent surfaces as sandwich under visible light source

Forming of gel is carried out by various proceses like hydrolysis and peptization or combination thereof & casting of gel is carried out on metal pans or molds coated with hydrophobic material. Heating of casted gel under visible light in the range of 40 to 200 watt to form semidried film& heating of the viscous gel is carried out in non-stick coated metal surfaces/mold under visible light source in the range of 40 to 200 watt. Metal surface/mold is coated with non stick thin layer comprising of ceramic, metal oxide, paraffin waxes or esters of fatty acids. The metal surface/ mould comprises of material such as iron, steel, copper, brass, zinc, nickel or other transition metal and their alloys which can conduct and distribute heat effectively and evenly. The porous transparent surfaces comprises of glass plastic or any other polymeric material having the pore diameter in the range of 0.5 to 5 mm. Porous transparent ceramic surfaces further comprising of ceramic, metal, or metal alloys surfaces. Calcinations of dried film is carried out at temperature range of 300 to 1500°C for a time duration in the range of 2 to 20 hours. Forming gel comprises of sol-gel route and forming gel by sol-gel route is using metal oxides of alumina, titania, zirconia, ceria and or other metal oxides of transition metal elements. Drying of semidried gel films between two porous transparent surfaces as sandwich under visible light source is to makes a way for easy solvent evaporation when the total assembly is heated under visible light.Calcinations of dried film is carried out by heating membrane as sandwich in between two porous ceramic surfaces. Method for production of ceramic membrane having high strength, enhanced thermal stability and chemical resistance comprising steps

a) forming gel by hydrolysis of aluminium alkoxide is concentrated by evaporating the solvent to obtain a viscous, free flowing gel;

b) drying viscous gel on the ceramic coated metallic surface/mold;

c) sizing of semidried gel film, cutting it in required size and dimensions;

d) drying by keeping semidried gel film between two porous transparent glass plates under the visible light;

e) heating dried gel film between two porous ceramic surfaces as sandwiched

assembly up to the temperature range of 400°C to 1 150°C. -

Method for production of ceramic membrane as claimed in claim 33 wherein forming gel is carried out by hydrolyse of Aluminium alkoxide ( Aluminium sec Butoxide ) or Alumina metal salts (Aluminium Chloride, Aluminium Nitrate, Aluminium Acetate) by using peptizing agent. Peptizing agent is glyoxylic acid. Ceramic coated metallic surface/mold are replacable by glass surface. Viscous, free flowing gel has viscosity of 1 Pa.s to 5 Pa.s_* The ceramic coated metallic surface/mold containing viscous gel are then placed under visible light source for about three to ten hours for drying at room temperature.Porous ceramic surfaces has porosity in the range of 50% to 98%.

DESCRIPTION OF INVENTION

The invention also aims at a furnace meant for production of flawless ceramic porous diaphragms that can be used for separation and other applications.

Thus the aim of the present invention is to make available a furnace that can surmount aforementioned shortcomings coupled with the background of the invention.

According to the present invention a furnace comprises of two furnace plates which are mounted on right stand by means of lock and slider arrangement. These furnace plates are heated by metallic heating coils encased in ceramic housing. The inner insulation is provided by the glass wool. The whole assembly of the plate is encased in metal sheet cover keeping the perforated disc side open. The upper and lower plates are fitted to the stand and can either be fixed or moved up and down on it by means of locks and slide arrangement. The stand is fitted to rectangular base. During application the semidried ceramic membrane film is inserted as sandwich in between two furnace plates. The plates are lowered gently on each other without damaging ceramic film. The assembly is then locked by locking arrangement provided on left stand. The total compilation is then mounted on the rectangular base. The base consists of all electrical circuits and wiring and can be connected to power source. The digital display unit for the temperature controller is fitted on the rectangular base. The vents present on the side rim of the plates helps in easy escape of gases and volatile matter coming out of the calcination of the semidried ceramic membrane. Thus the furnace is designed to produce crack free and plain ceramic membrane.

Perforated ceramic discs of the invention are mounted on a movable stand and equipped with heating mantle, insulation and is encased in a metallic cover. The pores present on ceramic disc not only helps in dissipation of gases emanating from heating of wet metal oxide gel diaphragms but also conducts the heat from heating coil to it. The pores in the ceramic disc plays dual role i.e. exit of trapped water and other organic matter as well as entry of heat towards the wet gel films for faster drying. On the other hand the perforated ceramic disc has a major role to play in preventing the deformation likely to occur during sintering of semidried metal oxide gel diaphragms by putting a vertical pressure and controlling its morphology as the heating progresses towards high temperature in controlled manner. By means of this setup the semidried gel diaphragms are calcined at high temperatures to get the desired flawless plain porous ceramic membranes and all operations are done smoothly in a user friendly approach.

The important features and benefits of the invention will be cleared from the following description and related to an example of sintering disc furnace, which is mentioned without any implied limitation. It can be referred to the associated drawing which shows preferred embodiments of the present invention.

The special feature of the invention is use of perforated ceramic disc for the calcination of the semidried ceramic membrane which is prepared by sol-gel method. The perforation present in the disc helps in easy escape of the gases and volatile matter emanating from the calcination of the semidried ceramic films. On the other hand this disc helps in maintaining the plain morphology of the film by preventing it from plastic deformation during heating process. The disc provides solid support to the ceramic films.

The another aspect of the invention is lock provided on the top of the furnace plate which helps in maintaining the place at a fixed position during calcinations process.

Yet another feature of the present invention is the slider and locks provided on the right stand by means of which both the furnace plate can be moved up and down vertically. The most important feature of the invention is the temperature controller device (PID) which helps in programming the steps and ramps for heating in controlled manner. It also displays digitally the values of actual and programmed temperature in degree centigrade. in system of invention, production of membrane having high strength, enhanced thermal stability and chemical resistance is carried out with at least two furnace plates, at least one heating coils encased in ceramic disc housing , metal sheet and base. These furnace plates are upper and lower plates fitted to the stand and can either be fixed or moved up and down on it by means of locks and slide arrangement.

Base of system consists of all electrical circuits and wiring and can be connected to power source with digital display unit for the temperature controller fitted on the rectangular base and furnace plate has at least one disc of ceramic or metal oxide with ceramic disc holder. One of the embodiments of present invention is that disc of ceramic or metal oxide used in system is porous.

Yet another embodiment of the invention is that disc of ceramic has vents on all over the circumference having pores with different diameter whereas each pore has different diameter at plane.

In specific application of System for production of membrane having high strength, enhanced thermal stability and chemical resistance comprises of two upper and lower furnace plates which are covered on one side i.e. upper plate on upper side and lower plate on lower side by metal sheet, the stand (8) for mounting furnace plates (1, 4), the base (12) , socket holder for upper and lower ceramic disc(17), rectangular base (12) , assembly lock (1 1) for mounting and operating by slide and lock arrangement (5) to the assembly lock can be fixed on the upper plate, heating source with temperature controller for temperature programmed by PID controller with digital display (6) fixed on base (12)

Yet another embodiments of the invention two upper and lower furnace plates has heating coil is circulated all over the plate in a manner in which it provides uniform heating to the porous ceramic plate.

Two upper and lower furnace plates of system has heating metal coils (14) are connected to electrical terminals (15) and The coils are well fitted in the grooves (16) present on one side of the porous ceramic plate wherein ceramic disc (17) holds the ceramic plate along with the assembly.

Yet another embodiment of the invention is that system has heating source with temperature controller for controlling temperature during heating and cooling of the device can be detected by thermocouple (18) and can be controlled by PID controller (6).

Yet another embodiment of the invention is that porous ceramic disc (2) has pores all over the area of the plate wherein porous ceramic disc (2) has pores (19) with diameter in the range 10 to 100 micron. Yet another preferred embodiment is that porous ceramic disc (2) is porous with average pore diameter 7.8 nm.

Yet another embodiment of the invention is that operating system for production of membrane can comprise steps like inserting semidried ceramic membrane film as sandwich in between two furnace plates; lowering plates gently on each other without damaging ceramic film; locking assembly by locking arrangement provided on stand; mounting total compilation on the rectangular base; calcinating of the semidried ceramic membrane circuits by switching on power source; controlling temperature of assembly by temperature control panel (6) on rectangular base to create a temperature profile of the furnace in such a manner that the circular alumina diaphragms gets heated up from room temperature to 2000°C to set with ramp rate of 1°C per minute, along with cooling temperature of assembly at cooling rate 1°C per minute.

In present method of invention, membrane is produced preferabaly by sol-gel route. Thus in present method comprises steps of forming gel, casting of gel, heating of casted gel to form semidried film, sizing of semidried gel film, drying of semidried gel films between two porous transparent surfaces as sandwich under visible light source and further calcinations of dried film by placing it between two plain porous ceramic pieces to obtained membrane.

For further simplification these steps can be given as follows:

a) Formation of gel by veriaous proceses like hydrolysis and peptization etc.

b) casting of gel on metal pans or molds coated with hydrophobic material, c) heating of casted gel under visible light to form semidried film,

d) sizing of semidried gel film cutting it in required size and dimensions,

e) drying of semidried gel films by placing between two porous transparent surfaces as sandwich under visible light source and

f) Calcinations of dried film by placing it between two plain porous ceramic pieces to obtained membrane.

Some of the features of the present invention can be given wherein membrane produced is with uniformity without any deformation and cracking. In present invention is heating the viscous gel in non-stick coated metal surfaces under visible light source in the range of 40 to 200 watt. The metal surface may be coated with non stick thin layer comprising of ceramic, metal oxide, paraffin waxes or esters of faty acids. Whereas the metal mould comprises of material such as iron, steel, copper, brass, zinc, nickel or other transition metal and their alloys which can conduct and distribute heat effectively and evenly.

Yet another aspect of the invention is use of porous transparent surfaces comprising of glass plastic or any other polymeric material and the pore diameter is in the range of 0.5 to 5 mm.

Yet another attribute of invention is the use of porous ceramic surfaces comprising of ceramic, metal, or metal alloys for calcination of dried aerogel films, or membranes.

Calcination is done in the temperature range of 300 to 2000°C for a time duration in the range of 2 to 20 hours.

Method steps of invention can be applied to method for production of alumina membrane wherein the alumina membrane of different thickness consists of gamma, delta, theta or alpha phases, depending on the respective temeprature values can be prepared. The membranes obtained are having pores in the range of 0.3 nm to 200 nm. The membrane thus formed is crack free, uniform and curve free and can be used in industries for various seperation processes or as cataytic membrane reactor..

In method for production of ceramic membrane can comprises of logical and reproducible steps by means with nanoporous size of 0.3 nm to 200 nm. By employing setps of the present invention, ceramic membranes via sol-gel method can be prepared with thickness in range of 0.2 mm to 20 mm.

The drying step mentioned in the present invention is useful in production of ceramic membranes by sol-gel route, using metal oxides of alumina, titania, zirconia, ceria and or other metal oxides of transition metal elements. The placement of semidried aerogel film as sandwich in between two glass porous surfaces makes a way for easy solvent evaporation when the total assembly is heated under visible light. This arrangement also helps in keeping the monolith plain and crackfree. Further heating is continued in furnace by placing the dried film as sandwich in between two porous ceramic surfaces.

Ultimately when a temperature of 400°C is reached the solvent evaporates, leaving behind the porous structure.

By applying present steps of invention ceramic membrane can be produced. To suite a specific requirements for pellicular membrane, steps of present invention can be modified to the knowledge of person skilled in art.

These steps for ceramic membrane production can be given as below.

1) Forming gel by hydrolysis of aluminium alkoxide is concentrated by evaporating the solvent to obtain a viscous, free flowing gel.

2) Drying viscous gel on the ceramic coated metallic surface.

3) sizing of semidried gel film, cutting it in required size and dimensions and keeping it between two porous transparent glass plates under the visible light for further drying.

4) Keeping dried gel film between two porous ceramic surfaces as sandwiched assembly.

5) Heating sandwiched assembly up to the temperature range of 400°C to 2000°C,

6) The porous membrane are then removed from the sandwich assembly and collared peripherally with thin plastic material.

The collared porous alumina ceramic membrane thus obtained can be fitted airtight in the Alteration assembly without undergoing any crack to be further used in separation processes.

By applying steps of present invention method, alumina membranes having porosity in therange of 50% to 90% can be prepared sol-gel process technique.

In formation of solution, Aluminium alkoxide ( Aluminium sec Butoxide ) or Alumina metal salts (Aluminium Chloride, Aluminium Nitrate, Aluminium Acetate) " are hydrolysed by using glyoxylic acid as peptizing agent.

The sol is further concentrated by evaporating solvent till suitable viscosity is to form viscous gel. The viscous gel is then poured into ceramic coated metallic moulds at room temperature. The non-stick metallic moulds comprises of metals such as copper, steel iron, metal alloys. Considerable reduction in time duration was achieved while drying gel by using nonstick metal coated moulds. The metallic base of the mould helps in distribution and conduction of heat effectively. The non stick ceramic layer of metallic mould not only helps in easy removal of semidried (wet) film from the mould but prevents cracking too.

Peeling or removing of semidried (wet) film from the mould is evident from Drawing 10 which depicts the contact angel studies done on hydrogel. It shows that the ceramic or metal oxide coated metal surface offers best option in comparison to glass surface in order to obtain the semidried gel film in a short span of time under visible light at room temperature.

Drawing 1 to 6 illustrates various elevation and sectional views of furnace for membrane calcination; it should be understood that the examples are merely illustrative and the invention should not be understood to be limited to the illustrated embodiments.

Drawing T, referring fig. 1 can be seen that isometric elevation of the membrane calcination device according to this invention comprises of two upper and lower furnace plates which are covered on one side i.e. upper plate on upper side and lower plate on lower side by metal sheet. Both the furnace plates (1 , 4) are mounted on the stand (8). The stand (8) is fitted to the base (12) firmly. The vents (10) are present on the socket holder of upper and lower ceramic plates for easy escape of exhaust gases during calcination. Another stand (13) is mounted on the rectangular base (12) firmly. On the Left stand (13), assembly lock (1 1) is mounted and can be operated by slide and lock arrangement (5) the assembly lock can be fixed on the upper plate. The groove (3) on upper plate is made for fixing the lock (1 1). The assembly can be temperature programmed by PID controller with digital display (6) fixed on base (12). The semidried membrane film can be placed on top of lower porous ceramic plate (2) in a manner which covers the maximum area of the plate and in no way should exceed the peripheral limits of the plates. The upper plate is then lowered on the lower plate gently and locked by slider and lock arrangement in a manner taking care not to damage the semidried metal oxide membrane film. The temperature controller (PID) is then programmed for desired calcination temperature. When the system is cooled to room temperature, the upper plate is elevated and the calcined plain membrane film can be removed easily from the top of lower ceramic plate. Drawing 2, referring fig. 2 can be seen that the front view of the furnace for ceramic membranes.

Drawing 3, shows top view of the Furnace for ceramic membrane. Drawing 4, referring to fig. 4 can be seen that vertical section view of furnace plate consists of six parts. Part 9(a) is porous disc of ceramic or metal oxide. Part 9(b) is metallic heating coil encased in ceramic plate, whereas part 9(c) refers to cover of ceramic sheet over heating coils. The part 9(d) refers to thermal insulation wool, whereas part 9(e) shows asbestos sheet separating the metal and glass wool. The part 9(f) indicates a metallic cover which encases all the arrangements except exposed part of perforated ceramic disc for sintering.

Drawing 5, referring Drawing 5 can be seen that sectional view of heating arrangement of porous ceramic plate. The heating coil is circulated all over the plate in a manner in which it provides uniform heating to the porous ceramic plate. The heating arrangement is similar for lower and upper ceramic plates. The heating metal coils (14) are connected to electrical terminals (15). The coils are well fitted in the grooves (16) present on one side of the porous ceramic plate. The ceramic disc (17) holds the ceramic plate along with the assembly. The changes in the temperature during heating and cooling of the device can be detected by thermocouple (18) and can be controlled by PID controller (6).

Drawing 6, Referring Drawing 6 can be seen that porous ceramic disc (2) with pores all over the area of the plate. These pores (19) are in the range 10 to 100 micron in diameter. The pores help in escape of gases and volatile matter, emanating from thermal calcinations of semidried membrane film. The porous ceramic plate also acts as a good support in maintaining the plain morphology of ceramic membrane film during calcination which is the main feature of this technology.

Drawing 7, referring Drawing 7 can be seen that sintered alumina ceramic membrane diaphragm with a size of 65 mm diameter and 2 mm thickness. It is the example of utility of furnace (FIG. l) in making ceramic membranes.

Drawing 8, referring Drawing 8 can be seen that a Thermo gravimetric Profile (TGA) of the alumina membrane produced using the said furnace. It shows that loss of weight at various temperature values as sintering progresses in the furnace (FIG. l). Loss of weight is in the form of gases during sintering, which escapes through the vents present on the furnace plate.

Drawing 9, referring Drawing 9 can be seen that BET adsorption graph which indicate that the resultant alumina ceramic diaphragms which is formed after sintering in the furnace (FIG.l) is porous with average pore diameter 7.8 It shows that the furnace is capable of producing the porous structures.

The model of highly effective sintering furnace presented above demonstrates a development that will build up in the near future. The focus will be on development of object oriented highly efficient processes as per the need of application and customer requirement. The attention is paid to all the controlling factors from the start in an integral outlook of output and expenditure. This approach creates rationale for current and future innovative research assignments. The operating of the furnace is easy and space required for installation is small. The furnace can be made in the portable dimensions to carry out studies in any environment.

By applying steps of present invention to production of alumina membranes in system of invention some of the specific requirment can be optimized.

Thus sol which is formed by hydrolysis of aluminium alkoxide is further concentrated up to viscosity of 1 Pa.s to 5 Pa.s. The viscous mass is then poured into hydrophobic ceramic thin film coated metallic mould.The viscous gel is free flowing and can be spread evenly in ceramic coated metallic mould. The gel containing moulds are then placed under visible light source for about three to ten hours ( range 40 to 200 watt) for drying at room temperature. The semidried gel film starts peeling up and can be easily removed from the surface. This air dried film can be handled easily and can be easily cut by a scissor or a knife into desired shapes and sizes.

The cut pieces are then placed between two porous transparent glass or plastic plates as sandwich model in such a way that it covers entire gel film. The galss or plastic plate used was of 2 to 10 mm thickness and coinsisted of symmetrical array of holes (pore diameter in the range of 0.5 to 5 mm ) all over. Overnight is sufficient for drying the aerogel film under the visible light source. All the solvent content of the gel gets evaporated. The transparent porous plate helps in keeping the aerogel film plain and crackfree. The holes in glass or plastic plate allows an easy solvent evaporation . The heat generated by visible light source is mild and specific which helps in slow removal of trapped solvent in aerogel network. The dried pieces can be lifted easily from the porous transparent glass plates and can be given a desired cut by a scissor or a knife. The plain dried aerogel film obtained above is further subjected to sintering or calcination. It is placed between two highly porous (50% to 90%) plain ceramic or metal plates in a programmable furnace. The pores diameter may vary from 200 nm to 1000 nm. The furnace temperature is raised gradually. The slow heating rate is very important as it prevents the thermal shocks and cracking in membrane / film. The volatile matter and organic template present in aerogel film gets evaporated as temperature in furnace starts increasing. TGA graph in Drawing 8 shows that up to the temperature of 400°C about 40% of the mass gets evaporated during calcination. The TGA analysis indicates that during the first 20 minutes nearly 10% to 20% of the volatile component of the air dried aerogel is lost. The temperature in this range is 500°C. The next step of 10% to 30% loss occurs at 400°C to 650°C within one hour to four hours. The first 20% loss is due to non-bonded volatile component in the form of water or alcohol which is trapped inside the aerogel matrix and capillaries. The next step is very important and actually results in the formation of porous membrane structure. The alkoxide groups bonded to the aluminium atom gets evaporated. Thus TGA analysis gives us a clear picture of planning the temperature programme of furnace for calcination.

The evaporation of organic template creates pores in the aerogel film . The porous ceramic or metal plates not only helps in easy escape of organic matter through its pores but also prevents the deformation in the alumina film. Generally rapid changes of mass occurs in the temperature range of 150 °C to 400 °C. This is the turbulent period in the processing of alumina film by sol-gel method. BET analysis ( Drawing 9) of the final calcined material at 1000°C shows that the film is porous having pore diameter in the range of 7 to 8 nm.

Calcination helps in changing the different phases of alumina at various temperature ranges. The gamma form of alumina exists up to a temperature of 300°C to 700°C. If heating is stopped at this stage we can get active gamma alumina phase. It can be applied in seperation as well as catalytic applications. If the calcination of alumina film is continued in the temperature. range of 750°C -900°C we obtain theta delta form which finally changes to alpha form 900°C to 1200°C. The alpha form of porous alumina film is highly stable and can be used in high temperature applications.

The problem of curving or deformation of alumina films at all stages is reduced by applying proper drying techniques. The time duration for drying of alumina gel films is also minimised by employing visible light source to speed up the evaporation of solvent gradually. The process of invention discloses calcination techniques which reduces the deformation in membrane diaphragms during high temperature sintering. The porous membrane diaphragms thus formed can be used in seperation processes in industries.The detailed description of the present invention is the resolve and aim to set a process for those of ordinary skill in the art for practical implementation within the context of invention.

Labels of the Drawings

1 - Upper furnace plate.

2- Porous furnace disc

3- Socket for furnace lock

4- Lower furnace plate

5- Slider and lock arrangement

6- Control and display panel

7- Slider and locks arrangement

8- Right Vertical stand

9- Ceramic disc holder

10- Vents for gases

1 1 - Furnace Lock '

12- Rectangular base

13- Left vertical stand

14- Heating coil

15- Electrical terminals

16- Separating ridge

17- Ceramic disc

18- Thermocouple

19- Micro pores on the ceramic disc

The following example gives illustration and results of use of furnace in detail.

Example

Flat porous alumina circular diaphragms which had a diameter of 70 mm and thickness of 2mm are sintered in high temperature furnace (DRAWING. 1), that has furnace plates 120mm diameter and 50mm high each in accordance to Fig. l . The pre air dried alumina aero gel circular diaphragm is placed on lower furnace plate (4), the upper furnace plate (1) is then gently lowered on the lower furnace plate in such a way not to damage the alumina diaphragm. The upper plate should just touch the diaphragm placed on lower plate. The locks on stand (8) and (13) are applied to fix the furnace plate. The temperature control panel (6) on rectangular base is used to create a temperature profile of the furnace in such a manner that the circular alumina diaphragms gets heated up from room temperature to 1000°C. The temperature of 1000°C is set with ramp rate of 1°C per minute. The stay at 1000°C is given for 30 minutes. The cooling rate is also set at 1°C per minute. When the temperature reaches 400°C all the organic matter and water content evaporates from alumina aero gel diaphragm through pores on porous ceramic plate (2). The TGA profile (DRAWING.8) shows that after 400°C there is no effect of mass transfer as the temperature progresses towards 1000°C. The exhaust gases escapes from furnace plate through vents provided on all over the circumference of furnace plates. The furnace cooled slowly as per the temperature profile.

o '

When the temperature reaches 25 C the locks are released and with utmost care the upper plate is lifted up and fixed at a safe distance. The sintered alumina diaphragm (DRAWING.7) is then removed from the place and is ready to use as separation media. The BET adsorption average pore diameter is 7.8nm (DRAWING.9).

Example 2

For production of Alumina membrane Aluminium sec-butoxide is hydrolysed by water in stoichiometric ratio of 1.25: 125 at 90°C with vigorous stirring.The alkoxide solution is peptized by addition of peptizing agent glyoxylic acid under vigorous stirring in the molar ratio, glyoxylic adid : Al =0.15: 1.25. The solution so obtained is kept at 95°C for 10 to 48 hours. A clear transparent sol is thus obtained. The clear sol obtained in above process is further concentrated by evaporating the solvent in the range of 40% to 70%.The viscous free flowing gel obtained is casted in metallic mold containing a coating of ceramic or metal oxide thin film. The thickness of the gel casted is in the range of 1 mm to 20mm. The gel is then kept under visible light source of 75 watt. This step helps in reducing the drying time of gel. Within 5 to 12 hours the film of gel gets hardened and starts peeling off the drying surface. The Gel diameter gets reduced upto 30% of the original mould diameter and the thickness of the gel film gets reduced up to 60% of the initial cast volume after drying under visible light source. The film is then lifted, washed with acetone , cut into required size and shape and placed in between two porous transparent glass plates as sandwich.This complete assembly is then kept under visible light source of 150 watt for drying. With overnight drying the solvent content of the aerogel film evaporates and material gets hardened and flat uniformly.The flat hardened film is then placed between two porous plain ceramic plates and the assembly is kept in programmable muffle furnace for calcination at high temperature.The furnace is programmed at temperature rise of 1°C per minute and maintained at 1 100°C for three hours . The material is then cooled to room temperature before lifting the alumina films from porous ceramic plates. The calcined alumina film is then collared peripherially by thin plastic flexible film for fitting into filtration assembly. The average pore diameter thus obtained is in the range of 5 to 200 A⁰.

Claims

CLAIMS laim,

1. System for production of membrane having high strength, enhanced thermal stability and chemical resistance comprising of at least two furnace plates, at least one heating coils encased in ceramic disc housing , metal sheet and base.

2. System for production of membrane as claimed in claim 1 wherein furnace plates are upper and lower plates fitted to the stand and can either be fixed or moved up and down on it by means of locks and slide arrangement.

3. System for production of membrane as claimed in claim 1 wherein base consists of all electrical circuits and wiring and can be connected to power source with digital display unit for the temperature controller fitted on the rectangular base.

4. System for production of membrane as claimed in claim I wherein furnace plate has at least one disc of ceramic or metal oxide with ceramic disc holder.

5. System for production of membrane as claimed in claim 1 and 4 wherein disc of ceramic or metal oxide is porous.

6. System for production of membrane as claimed in claim 1 and 4 wherein disc of ceramic has vents on all over the circumference

7. System for production of membrane as claimed in claim 1 and 4 wherein disc of ceramic or metal oxide has pores with different diameter.

8. System for production of membrane as claimed in claim 1 and 4 wherein each pore has different diameter at plane.^"

9. System for production of membrane having high strength, enhanced thermal stability and chemical resistance comprises of two upper and lower furnace plates which are covered on one side i.e. upper plate on upper side and lower plate on lower side by metal sheet, the stand (8) for mounting furnace plates (1, 4), the base (12) , socket holder for upper and lower ceramic disc(17), rectangular base (12) , assembly lock (1 1) for mounting and operating by slide and lock arrangement (5) to the assembly lock can be fixed on the upper plate, heating source with temperature controller for temperature programmed by PID controller with digital display (6) fixed on base (12)

10. System for production of membrane as claimed in claim 1 and 9 wherein two upper and lower furnace plates has heating coil is circulated all over the plate in a manner in which it provides uniform heating to the porous ceramic plate.

1 1. System for production of membrane as claimed in claim 1 and 9 wherein two upper and lower furnace plates has heating metal coils (14) are connected to electrical terminals (15) and The coils are well fitted in the grooves (16) present on one side of the porous ceramic plate.

12. System for production of membrane as claimed in claim 1 and 9 wherein ceramic disc (17) holds the ceramic plate along with the assembly.

13. System for production of membrane as claimed in claim 1 and 9 heating source with temperature controller for controlling temperature during heating and cooling of the device can be detected by thermocouple (18) and can be controlled by PID controller (6).

14. System for production of membrane as claimed in claim 1 and 9 as wherein porous ceramic disc (2) has pores all over the. area of the plate.

15. System for production of membrane as claimed in claim 1 and 9 as wherein porous ceramic disc (2) has pores (19) with diameter in the range 10 to 100 micron.

16. System for production of membrane as claimed in claim 1 and 9 as wherein porous ceramic disc (2) is porous with average pore diameter 7.8 nm.

17. Method of operating system for production of membrane as claimed in claim 1 to 16 comprising steps of inserting semidried ceramic membrane film as sandwich in between two furnace plates; lowering plates gently on each other without damaging ceramic film; locking assembly by locking arrangement provided on stand; mounting total compilation on the rectangular base; calcinating of the semidried ceramic membrane circuits by switching on power source; controlling temperature of assembly by temperature control panel (6) on rectangular base to create a temperature profile of the furnace in such a manner that the circular alumina diaphragms gets heated up from room temperature to 2000°C to set with ramp rate of 1 °C per minute ; cooling temperature of assembly at cooling rate 1°C per minute.

18. Method for production of membrane having high strength, enhanced thermal stability and chemical resistance comprising steps of forming gel, casting of gel, heating of casted gel to form semidried film, sizing of semidried gel film, drying of semidried gel films between two porous transparent surfaces as sandwich under visible light source and further calcinations of dried film to obtained membrane;characterized that drying is carried out in between two porous transparent surfaces as sandwich under visible light source

19. Method for production of membrane as claimed in claim 18 wherein forming of gel is Carried out by veriaous proceses like hydrolysis and peptization or combination thereof. '

20. Method for production of membrane as claimed in claim 18 wherein casting of gel is carried out on metal pans or moulds coated with hydrophobic material.

21. Method for production of membrane as claimed in claim 18 wherein heating of casted gel under visible light In the range of 40 to 200 watt to form semidried film.

22. Method for production of membrane as claimed in claim 18 wherein sizing of semidried gel film cutting it in required size and dimensions.

23. Method for production of membrane as claimed in claim 1 wherein heating of the viscous gel is carried out in non-stick coated metal surfaces/mold under visible light source in the range of 40 to 200 watt.

24. Method for production of membrane as claimed in claim 23 wherein metal surface/mold is coated with non stick thin layer comprising of ceramic, metal oxide, paraffin waxes or esters of fatty acids.

25. Method for production of membrane as claimed in claim 23 wherein the metal surface/ mould comprises of material such as iron, steel, copper, brass, zinc, nickel or other transition metal and their alloys which can conduct and distribute heat effectively and evenly.

26. Method for production of membrane as claimed in claim 18 wherein porous transparent surfaces comprises of glass plastic or any other polymeric material having the pore diameter in the range of 0.5 to 5 mm. .

27. Method for production of membrane as claimed in claim 26 wherein porous transparent ceramic surfaces further comprising of ceramic, metal, or metal alloys surfaces.

28. Method for production of membrane as claimed in claim 18 wherein calcinations of dried film is carried out at temperature range of 300 to 1500°C for a time duration in the range of 2 to 20 hours.

29. Method for production of membrane as claimed in claim 18 wherein forming gel comprises of sol-gel route.

30. Method for production of membrane as claimed in claim 18 wherein forming gel by sol-gel route is using metal oxides of alumina, titania, zirconia, ceria and or other metal oxides of transition metal elements.

31. Method for production of membrane as claimed in claim 18 wherein drying of semidried gel films between two porous transparent surfaces as sandwich under visible light source is to makes a way for easy solvent evaporation when the total assembly is heated under visible light.

32. Method for production of membrane as claimed in claim 18 wherein calcinations of dried film is carried out by heating membrane as sandwich in between two porous ceramic surfaces.

33. Method for production of ceramic membrane having high strength, enhanced thermal stability and chemical resistance comprising steps

f) forming gel by hydrolysis of aluminium alkoxide is concentrated by evaporating the solvent to obtain a viscous, free flowing gel;

g) drying viscous gel on the ceramic coated metallic surface/mold;

h) sizing of semidried gel film, cutting it in required size and dimensions;

i) drying by keeping semidried gel film between two porous transparent glass plates under the visible light;

j) heating dried gel film between two porous ceramic surfaces as sandwiched

assembly up to the temperature range of 400°C to 2000°C.

34. Method for production of ceramic membrane as claimed in claim 33 wherein forming gel is carried out by hydrolyse of Aluminium alkoxide ( Aluminium sec Butoxide ) or Alumina metal salts (Aluminium Chloride, Aluminium Nitrate, Aluminium Acetate) by using peptizing agent.

35. Method for production of ceramic membrane as claimed in claim 33 wherein peptizing agent is glyoxylic acid.

36. Method for production of ceramic membrane as claimed in claim 33 wherein ceramic coated metallic surface/mold are replacable by glass surface.

37. Method for production of ceramic membrane as claimed in claim 33 wherein viscous, free flowing gel has viscosity of 1 Pa.s to 5 Pa.s.

38. Method for production of ceramic membrane as claimed in claim 33 wherein the ceramic coated metallic surface/mold containing viscous gel are then placed under visible light source for about three to ten hours for drying at room temperature.

39. Method for production of ceramic membrane as claimed in claim 33 wherein porous ceramic surfaces has porosity in the range of 50% to 98%.

40. System for production of membrane as described in drawings and in examples herein

41. Membrane produced by system as claimed in claims 1 to 17 and method as claimed in claims 18 to 39 herein.

Dated this 07 day of March 2013

Kolhe

Of InlOgible Innovations LLP Applicant's Agent