Europaisches Patentamt 287 730 J European Patent Office 2) Publication number: 0 A1 Office europeen des brevets

EUROPEAN PATENT APPLICATION

© Application number: 87303659.4 © mtci.*: G01N 27/56

© Date of filing: 24.04.87

@ Date of publication of application: © Applicant: UOP INC. 26.10.88 Bulletin 88/43 25 East Algonquin Road Oes Plaines Illinois 6001 7-501 7(US) © Designated Contracting States: BE DE ES FR GB IT NL SE © Inventor: Petty-Weeks, Sandra Louise 15271 White Oak Drive West Chicago Illinois, 60185(US)

© Representative: Brock, Peter William UOP Processes International Corporation 48 Leicester Square London WC2H 7LW(QB)

Method and apparatus for detecting hydrogen-containing hydrogen-positive gases.

© Apparatus and method for detecting and mea- Fig suring hydrogen and gaseous compounds capable of dissociating into or combining with hydrogen ions using a novel solid electrolyte membrane which comprises a three-component blend prepared by admixing an organic polymer or copolymer, such as poly(vinyl alcohol), with an inorganic compound, such as a phosphoric acid, and an organic com- pound selected from a group of polymers and copolymers having monomer units containing nitro- gen, oxygen, or sulfur atoms, such as poly(vinyl pyrrolidone).

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Xerox Copy Centre 0 287 730

GAS- "METHOD AND APPARATUS FOR DETECTING HYDROGEN-CONTAINING OR HYDROGEN-REACTIVE ES"

inven- This invention relates to electrochemical mea- membrane is used in and part of the present that surement and detection of hydrogen or substances - tion. This membrane embodies the discovery a thin film capable of reacting with hydrogen. More specifi- macroscopically homogeneous polymer- fabricated from admix- cally, it relates to the use of a novel solid proton- blend membrane may be an such sulfuric conducting electrolyte membrane and a catalyst in 5 ture of an inorganic compound, as or detecting the presence in a sample gas of hy- acid or phosphoric acid, with an organic polymer selected drogen or gases capable of dissociating to yield or copolymer and an organic compound to combine with hydrogen ions, including oxygen, from a group of polymers and copolymers having sul- and measuring the quantity present relative to a monomer units containing nitrogen, oxygen, or known reference substance. The solid electrolyte w fur atoms, where the three components are at least This membrane is capable of membrane may be formed by blending an in- partially compatible. in detec- organic compound, an organic polymer or acting as a proton conductor a hydrogen is converted into copolymer, and an organic compound selected tor where molecular hydrogen of the membrane, protons are from a group of polymers and copolymers having protons on one side and monomer units containing nitrogen, oxygen, or sul- 15 then transported through the membrane, pro- fur atoms, or by compositing a membrane compris- tons are recombined with electrons to form molec- The membrane is ing these components with a porous support. This ular hydrogen on the other side. invention also involves the use of a reference sub- also useful in detection of gases capable of dis- with ions. stance in gaseous or solid form. sociating into or combing hydrogen U.S. Patent 4,500,667 (Polak and Beuhler) de- 20 In addition, the three components utilized to scribes proton-conducting membranes. make the membrane may be composited with or U.S. Patent 4,024,036 (Namamura et al) de- on a porous support to form a supported mem- well scribes a proton permselective solid state member brane which possesses increased strength as of capable of exhibiting ionic conductivity. as being a protonic conductor. Examples ma- U.S. Patent 3,265,536 (Miller et al), 4,306,774 25 terial used for such porous support include glass (Nicholson), 3,276,910 (Grasselli et al), and cloths, polysulfone and ceramics. 4,179,491 (Howe et al) deal with substances ca- The invention utilizes a concentration cell pable of conducting hydrogen ions. whose electrolyte is said membrane or supported An article by Lundsgaard, J.S., et al, "A Novel membrane. A membrane is mounted in a sample Hydrogen Gas Sensor Based on Hydrogen 30 cell or membrane housing having a sample gas URANYL Phosphate," Solid State Ionics 7 (1982) chamber and a reference chamber, which cham- 53-56, North Holland Publishing Co., describes ex- bers are separated by a partition comprising the contains the periments done using a substance which conducts membrane. The sample gas chamber hydrogen ions. gas sample of interest, which must include a com- A hydrogen detector using more complex 35 ponent capable of dissociating to form hydrogen methods than that of the invention may be seen in ions or capable of combining with hydrogen ions. U.S. Patent 4,373,375 (Terhune et al) and on page In the other chamber is a reference gas whose 8 of Platinum Metals Review 27.1 (January 1983), composition is known or a solid reference sub- Johnson Matthey, London. Three references show- stance which exhibits a substantially constant of the ing hydrogen detectors which use an entirely dif- 40 known hydrogen partial pressure during use ferent principle than the present invention are U.S. invention. Molecular transport through the mem- Patents 4,324,760 and 4,324,761 (Harris) and an brane should be sufficiently slow so that gases will article on page 29 of the August 1972 Instrumenta- not mix by diffusing through it. tion Technology. A catalytic agent for promotion of dissociation U.S. Patent 4,040,929 (Bauer et al) shows the 45 to hydrogen ions or combination with hydrogen use of a solid reference in an oxygen sensor. ions is in intimate contact with the membrane on The present invention provides methods and the sample gas side. Another catalytic agent is also reference side. It apparatus for detecting gaseous hydrogen, hydro- provided in a like manner on the that the catalytic be gen ion, dissociable hydrogen compounds, and is not necessary same agent substances capable of combining with hydrogen so used on both sides. Means for forming electrical ion, in order to indicate the presence or absence of contact and transferring electrons to and from an these substances and, where desired, provide external circuit are provided on each side of the quantitative information on the amount present. electrolyte in intimate contact with the catalytic A novel three component solid electrolyte agents. The cell electromotive force (EMF) Is mea- 0 287 730

sured across said means for forming electrical con- a solid electrolyte (ionic conductor) and conducting tact and provides an indication of the presence of electrodes are attached to both sides of the ionic hydrogen or gases capable of combining with it in conductor, an EMF is generated which is related to the sample gas and/or a quantitative measure of the partial pressures as follows: the amount of such which is present. A preferred embodiment of the method of the ** - ^ invention may be summarized as a method for Eo+-sr detection, in a gas sample, of a gaseous compo- nent which is capable, in the of a cata- presence where R is the gas constant, T is absolute tem- of to ions 10 lytic agent, dissociating yield hydrogen perature, F is the Faraday constant, Eo is the such method or of combining with hydrogen ions, standard oxidation-reduction potential difference, first comprising contacting said gas sample with a EMF is electromotive force, and n is the number of surface of a thin film polymer-blend membrane and electrons per molecule of product from the overall detecting an EMF signal between means for for- cell reaction. electrical connection with two 75 ming separate por- If the system described by the above equation tions of effective to the a catalytic agent promote behaves nonideally, the partial pressures must be dissociation and combination of ions, hydrogen replaced by fugacites. Another factor which may of is in contact where a first portion catalytic agent need to be considered in regard to a particular with said first surface and second of a portion system is the rate of dissociation to form the ions is in contact with a second surface 20 catalytic agent which pass through the solid electrolyte. This may said membrane which membrane isolates said of be a limiting factor to the transfer of ions through from reference substance and has gas sample a the electrolyte. The rate of dissociation can be said second surface to the reference sub- exposed calculated by means of the equilibrium constant for stance, said membrane comprising a blend of three the dissociation reaction. which 25 components, components are an organic The magnitude of EMF produced is generally polymer or copolymer, an inorganic compound se- in accordance with the parameters discussed here- of acids, lected from a group consisting phosphoric in: the Nernst equation and, where applicable, the acids, and salts of sulfuric acid, heteropoly dissociation equilibrium constant. However, re- and heteropoly acids, an organic compound se- quired practice in measuring concentration is to from of and lected a group polymers copolymers 30 periodically calibrate the measuring apparatus by units having monomer containing nitrogen, oxygen, use of samples whose composition is known. Thus, is or sulfur atoms, which organic compound com- exact adherence to theoretical relationships is not with said and said or- patible inorganic compound required of commercially used methods and ap- and the EMF ganic polymer correlating resulting paratus. The primary commercial requirement is existence amount of said signal with the or gas- 35 repeatability. eous component. It has now been discovered that a macro- device be used to automati- A calculating may scopically homogeneous thin film polymer-blend calculate concentrations, or calculation cally may membrane may be fabricated by admixing the or- be This device accomplished manually. may re- ganic and inorganic components discussed herein. ceive from probe, or tempera- 40 input a temperature Substances which are permerable by gases in a be entered for in the cal- ture may manually use selective manner are known and utilized in a vari- culation. of the or and/or Temperature gas gases ety of applications. A membrane formed in accor- be controlled at the membrane housing may a pre- dance with the present disclosure is substantially established value. The catalytic be plati- agent may impermeable to ions and gases, including hydro- palladium, or alloys thereof. The catalytic 45 num, gen gas, but does allow hydrogen ions to pass be conductive. Where tem- agent may electrically through it. For background information relating to of the is too low for perature sample gas high or the principles of the present invention, reference effective detection, it be adjusted before the may may be made to the book Solid Electrolytes and with the element. It gas is contacted electrolyte Their Applications, edited by Subbarao, Plenum may be necessary to adjust the concentration, in a 50 Press, 1980. of the known manner, sample gas contacting mem- Low mechanical strength has been a common brane in order to achieve effective detection. problem when attempting to apply permselective The invention utilizes solid present a electolyte membranes. The present invention provides a certain The Nernst sensor for detection of gases. membrane whose mechanical strength is increased describes the behavior of devices 55 equation sensing by compositing it with other materials, but whose When two media with dif- using solid electrolytes. desirable properties are not lost as a result of ferent P1 and P2, of partial pressures, a particular doing so. in both media substance present are separated by Also used in a preferred embodiment of the 0 287 730

abrupt changes in present invention is a solid substance which is a mer from solid to liquid are coefficient of expansion substitute for a reference gas, which reference gas certain properties, such as composi- is one of the two media mentioned above in the and heat capacity. The polymer-blend discussion of the Nernst equation. It is highly desir- tions of the present invention exhibit high protonic below the ob- able to use a solid reference substance which 5 conductivity at temperatures well of the individ- requires only periodic replacement instead of main- served glass transition temperatures ion-con- taining a continuous reference gas flow, or in ap- ual homopolymers. A device utilizing an below the of the propriate situations maintaining a sealed chamber ducting polymer must operate Tg is not usable at higher tem- of reference gas. The reference substance is in polymer; the polymer A intimate contact with the catalytic agent on the io peratures due to loss of strength, tackiness, etc. exhibited reference side of the membrane. One substance polymer-blend of the present invention transition which are at- may service as both reference substance and cata- two glass temperatures, but at different lytic agent. tibutable to the polymers occur deter- Figure 1 is a schematic representation, in values than the glass transition temperatures mixed with cross-section, of a test sensor similar to that used 75 mined for each polymer when it is not low in initial proof of principle experimentation. The any other substance. In addition, at a relatively transition is observed; drawing is not to scale. temperature, a second order Figure 2 is a schematic representation, in This is attributable to the inorganic compound. cross-section, of a test sensor which may be used Thus, it may be appreciated that there is a degree that at in experimentation for the embodiment which uti- 20 of interaction between the components, is, between the lizes a solid reference substance. It is not to scale. least some chemical interaction exists Figure 3 is a portion of a phase diagram of a components. solid reference substance capable of use in an A distinct advantage which is possessed by the embodiment of the present invention, in which hy- polymer-blend membranes of the present invention blend membrane is drogen partial pressure of the substance is plotted 25 over other organic-inorganic low resistivities against the amount of hydrogen in the substance. If that these membranes possess which the plot were extended to larger amounts of hy- (resistance times area divided by thickness), less than drogen, several plateaus might appear. are four to five orders of magnitude In Figure 4 depicts, in a sectional view, a sen- certain other organic-inorganic polymer blends. the sor with a sealed reference chamber mounted on a 30 using a gas sensor of the type of present pipeline. It is not to scale and has non-essential invention it is necessary to measure the output elements omitted. voltage. When utilizing a membrane of the instant Figure 5 depicts an embodiment of the in- invention, it will be possible to use a voltage mea- vention, in a sectional view, in which a membrane suring device of lower impedance. Use of such a and lower cost is part of a partition separating a sample gas cham- 35 device will result in a simplified ber from a reference chamber. electronics package for a commercial hydrogen It has now been discovered that a useful blend sensor. A voltmeter should have an impedance (AC of components may be obtained by admixing cer- resistance) at least 3 orders of magnitutde greater tain organic polymeric compounds with particular than that of .the system in which it is used for inorganic compounds, such as certain inorganic 40 measurement; high impedance voltage measuring acids or salts thereof, and with certain organic devices are more costly than those of low imped- compounds selected from a group of polymers and ance. In addition, a device with reduced impedance copolymers having monomer units containing nitro- is less sensitive to electromagnetic interference device. This the gen, oxygen, or sulfur atoms. The resulting com- than a high impedance permits envi- position of matter is formed into a macroscopically 45 device to be located in an electrically noisy homogeneous thin film membrane which may be ronment without adversely affecting its perfor- utilized in gas detection systems. The utility of mance. these membranes in gas detection devices is due The membrane of the present invention com- in part to the fact that the membranes will possess prises a blend of an organic polymer or copolymer, a high protonic conductivity, especially at room or so one of certain inorganic compounds, and an or- ambient temperature. ganic compound selected from a group of poly- Usually, high ionic conductivity is observed in mers and copolymers having monomer units con- which polymer complexes only when the temperature is taining nitrogen, oxygen, or sulfur atoms, above their glass transition temperature (Tg), that organic compound is at least partially compatible is, above the temperature at which the substance 55 with the inorganic compound and organic polymer. be changes from its solid to a liquid (the melting point Examples of organic polymers which may the of a polymer is usually above its glass transition employed as one component of the blend of temperature). Indications of the change of a poly- present invention will include polymers and 0 287 730 copolymers of vinyl alcohol, vinyl fluoride, ethylene ammonium tungstosilicate, sodium tungstosilicate, oxide, ethylimine, ethylene glycol, cellulose ace- potassium tungstosilicate, lithium tungstosilicate, tate, vinylmethylethyl ether, phenol formaldehyde calcium tungstosilicate, magnesium tungstosilicate, resins, etc. etc. The inorganic compound is selected from a 5 The third component of the thin film polymer group consisting of a phosphoric acid, sulphuric blend membrane of the present invention is an acid, heteropoly acids, or salts of heteropoly acids. organic compound selected from the group of poly- Examples of phosphoric acids which may be em- mers and copolymers having monomer units con- ployed will include hypophosphoric acid, taining nitrogen, oxygen or sulfur atoms, which metaphosphoric acid, orthophosphoric acid, 70 organic compound is at least partially compatible pyrophosphoric acid, pholyphosphoric acid, etc. with the aforementioned inorganic compounds and The sulfuric acid which is employed will comprise organic polymers and will include poly- an aqueous sulfuric acid which may contain from (ethyloxaxoline), poly(vinyl sulfonic acid), poly(vinyl about 10% to about 40% sulfuric acid in the aque- pyridine), poly(vinyl pyrrolidene), poly(vinyl pyr- ous solution. Examples of heteropoly acids or salts 75 rolidone), polyimide, poly(acrylamide, etc. It is also thereof which may be employed as a component of contemplated within the scope of this invention that the organic-inorganic blend which may be used to polymers of other oganic compounds containing a form a membrane will possess the generic formula: mixture of nitrogen, oxygen and sulfur atoms such Am(XxYy02) .n H2O in which X is selected from the as poly(vinyl-substituted furans) etc. may also be group consisting of boron, aluminum, gallium, sili- 20 employed, although not necessarily with equivalent con, germanium, tin, phosphorus, arsenic, antimo- results. It is desirable to select a compound which ny, bismuth, selenium, tellurium, iodine, and the has a relatively high heat distortion temperature in first, second, third and fourth transitional metal se- comparison to the other components of the blend ries, said series including scandium, yttrium, lan- and is relatively hygroscopic. It is also desirable thanum, actinium, titanium, zirconium, hafnium, va- 25 that this third component be at least partially mis- nadium, niobium, tantalum, chromium, molybde- cible with the other components. num and tungsten, Y is different from X and is It is to be understood that the aforementioned selected from the first, second, third, or fourth listing of inorganic compounds, organic polymers, transitional metal series, A is selected from the and organic compounds are only representative of group consisting of hydrogen, ammonium, sodium, 30 the class of compounds which may be employed in potassium, lithium, rubidium, cesium, beryllium, formulating the inorganic-organic blends of the magnesium, calcium, strontium and barium, m is present invention, and that this invention is not an integer of from 1 to 10, y is an integer of from 6 necessarily limited thereto. to 12 based on x taken as 1, z is an integer of from The novel compositions of matter used in the 30 to 80 and n is an integer of from 3 to 100. 35 present invention are prepared by admixing the Specific examples of these compounds will in- three components of the blend in a mutually mis- clude dodecamolybdophosphoric acid (DMPA), am- cible solvent at solution conditions for a period of monium molybdophosphate, sodium molyb- time sufficient to form the desired blend. In the dophosphate, potassium molybdophosphate, lith- preferred membrane the mutually miscible solvent ium molybdophophate, calcium moiybdophosphate, 40 which is employed to dissolve the components magnesium molybdophosphate, dodecatung- comprises water, although it is contemplated within stophosphoric acid, ammonium tungstophosphate, the scope of this application that any other mutu- sodium tungstophosphate, potassium tung- ally miscible solvent, either inorganic or organic in stophosphate, lithium tungstophosphate, calcium nature may also be employed. The mixing of the tungstophosphate, magnesium tungstophosphate, 45 three components of the composition of matter dodecamolybdosilicic acid, ammonium moiyb- may be affected at solution conditions which will dosilicate, sodium molybdosilicate, potassium include a temperature in the range of from about molybdosilicate, lithium molybdosilicate, calcium ambient (20o-25oC) up to the boiling point of the molybdosilicate, magnesium molybdosilicate, mutually miscible solvent which, for example, in the dodecamolybdogermanic acid, ammonium molyb- so case of water is 100oC. As an example, poly(vinyl dogermanate, sodium molybdogermanate, potas- pyrrolidone), poly(vinyl alcohol), and ortho- sium molydogermanate, lithium molybdoger- phosphoric acid may be placed in a flask and manate, calcium molybodgermanate, magnesium dissolved in water which has been heated to molybdogermanate, hexamolydbotelluric acid, am- 100oC. The blend is cast upon a suitable casting monium molybdotellurate, sodium moiybdotel- 55 surface which may consist of any suitable material lurate, potassium moiybdotellurate, lithium sufficiently smooth in nature so as to provide a molybodellurate, calcium moybdotellurate, magne- surface free of any defects which may cause im- sium mobydotellurate, dodecatungstosilicic acid, perfections on the surface of the membrane. Exam- 0 287 730 10

sulfonic acid), and pies of suitable casting surfaces may include met- poly(vinyl alcohol)-poly(vinyl als such as stainless steel, aluminium, etc., glass, ammonium molybdosulfate-cellulose acetate-poly- polymer or ceramics. After casting the solution (vinyl sulfonic acid). also be contemplated within the scope upon the surface, the solvent is then removed by It is to that the thin film polymer blend any conventional means including natural evapora- 5 of this invention a tion or forced evaporation by the application of membranes may, if so desired be composited on structural elevated temperatures, whereby said solvent is solid porous support whereby increased the membrane. These evaporated and the desired membrane comprising strength will be imparted to desirable char- a thin film of the polymeric blend is formed. The membranes will possess the same thickness of the film can be controlled by the w acteristics as the unsupported membranes, such as electrical amounts of the various components of the blend tensile strength, mechanical properties, and in addition, will which are present in the reaction mixture or by the properties, yield strength, etc., thus depth of the casting vessel. The thin film organic- also possess added structural strength, per- utilized in such de- inorganic blend which is prepared according to the mitting the membrane to be the membrane be subjected to process of the present invention will possess a 75 vices where may thickness which may range from about 0.1 to over forces of increased strength. in 500 microns and preferably from about 20 to about The supported membrane may be prepared the 60 microns. a manner similar to that set forth with regard to The amounts of inorganic compound, organic unsupported membrane. For example, the thin film membrane polymer or copolymer, and organic compound 20 semipermeable portion of the compos- the three used in the blend may vary over a relatively wide ite may be prepared by admixing compo- in miscible solvent at range. For example, the inorganic compound which nents of the blend a mutually time sufficient to comprises a phosphoric acid, sulfuric acid, solution conditions for a period of of reaction heteropoly acid or salts thereof may be present in form the desired blend. Again, the time will the blend or membrane in a range of from about 1 25 which is necessary to form the desired blend to about 75 weight percent (preferaby 30 to 60), vary with the particular polymers containing a nitro- and the organic polymer may be present in the blend gen, sulfur or oxygen atom, organic poilymer been selected to or membrane in a range of from about 1 to about inorganic compound which have the 49 weight percent, and the organic compound con- form the desired membrane. After allowing sufficient to taining a nitrogen atom, etc., may be present in the 30 mixture to stand for a period of time is cast blend or membrane in a range of from about 1 to from the desired membrane, the solution which about 49 weight percent. Whenever a composition upon a porous support. The porous support of is expressed herein, it is to be understood that it is is employed to increase the structural strength based, in the case of polymers, on the monomer the membrane will comprise a compound which than the repeat unit. 35 possesses a porosity equal to or greater Some representative examples of a thin film porosity of the thin film inorganic-organic blend. It invention polymer blend membrane which may be prepared is contemplated within the scope of this will comprise orthophosphoric acid-poly(vinyl alco- that any relatively open-celled foam or porous sub- hol)-poly(vinyl pyrrodolidone), pyrophosphoric acid- strate which possesses a structural strength greater poly(vinyl alcohol)-poly(vinyl pyrrolidone), sulfuric 40 than the thin film membrane may be employed. will in- acid-poly(vinyl alcohol)-poly(ethyloxazoline), Some examples of these porous supports dodecamolybdophosphoric acid-poly(vinyl alcohol)- clude compounds such as glass cloth, polysulfone, poly(ethyloxazoline), dodecatungstophosphoric cellulose acetate, polyamides, ceramics such as acid-poly-(vinyl alcohol)poly(acrylamide), alumina, glass, porcelain, etc., which have been dodecamolybdosilicic acid-poly(vinyl alcohol)-poly- 45 fabricated to possess the necessary porosity, etc. (acrylamide), ammonium molybdophosphate-poly- The amount of blend which is cast upon the porous (vinyl fluoride)-poly(vinyl pyrrolidone), ortho- support will be that which is sufficient to form a thin phosphoric acid-poly(vinyl alcohol)-poly(vinyl pyr- film membrane having a thickness within the range rolidene), pyrophosphoric acid-poly(vinyl alcohol)- previously set forth. After casting, the mutually removed poly (ethyloxazoline), sulfuric acid-poly(vinyl alco- 50 miscible solvent such as water is by hol)-polyimide, dodecamolybdophosphoric acid- conventional means such as normal evaporation or external poly(vinyl alcohol)-poly(vinyl pyrrolidone), forced evaporation by the application of dodecatungstophosphoric acid-poly(vinyi alcohol)- heat, application of vacuum, etc., and the desired poly(ethyloxazolin), ammonium molybdophosphate- membrane comprising the thin film blend com- poly(vinyl alcohol)-poly(vinyl pyrroldione), ortho- 55 posited on the porous support may be recovered phosphoric acid-poly(vinyl alcohol)-poly- and utilized in an appropriate gas separation ap- (acrylamide), sulfuric acid-poly(ethylene oxide)- paratus or gas sensor apparatus. poly(acrylamide), dodecatungstophosphoric-acid- Examples of novel thin film inorganic-organic 11 0 287 730 12 polymer blends which are composited on a solid ink. The porous structure of sputter-deposited cata- support and whihc may be prepared according to lytic agent is helpful in facilitating spillover of hy- the process of the present invention will include drogen ions onto the membrane, but such structure orthophosphoric acid-poly(vinyl alcohol)-poly(vinyl is not required. pyrrolidone) composited on a glass cloth, ortho- 5 Referring to Figure 1 , membrane 1 , or disc 1 , phosphoric acid-poly(vinyl alcohol)-poly(vinyl pyr- was mounted in test fixture 2, which may also be idine) composited on polysulfone, orthophosphoric referred to as a sample cell, membrane housing, or acid-poly(vinyl alcohol)-poly(ethyloxazoline) com- test sensor. The above-mentioned platinum depos- posited on cellulose acetate, orthophosphoric acid- its 5 served as catalytic agent to promote dis- poly(vinyl alcohol)-poly(vinyl pyrrolidone) composit- io sociation and reassociation or combination of hy- ed on alumina, pyrophosphoric acid-poly(vinyl al- drogen. Electrical connection was made to the cohol)-poly(acrylamide) composited on a glass platinum through copper platens 6, which were cloth, etc. held in place by springs (not shown) extending It is to be understood that the aforementioned between the platens and interior surfaces of the list of polymer blends is only representative of the 75 sample cell. Platens 6 did not cover the entire class of polymer blended membranes which may surface of the catalytic agent, though Figure 1 be prepared and that the invention is not necessar- shows this to be the case. Note that when the ily limited thereto. catalytic agent is electrically conductive and not It will be helpful in gaining an understanding of discontinuous, electrical contact need be made the invention to examine initial proof of principle 20 only at one point. However, catalytic agent need experimentation. The information presented in re- not be electrically conductive. Wire leads 3 and 4 gard to this experimentation is not meant to limit extended from the platens out of the test fixture the scope of the invention in any way. through means for sealing against gas leakage (not Three stock solutions were prepared: 10 grams shown). Leads 3 and 4 connecting to EMF and of poly(vinyl alcohol) having a molecular weight of 25 current detection means (not shown). Membrane 1 133,000 was dissolved in 500 ml of deionized wa- was sealed into test fixture 2 by 0-rings 7 so that ter, 5 grams of poly(vinyl pyrrolidone) having a there were no gas leakage paths between test gas molecular weight of 40,000 was dissolved in 250 ml chamber 8 and reference gas chamber 9. Tubing of deionized water, and 14.7 grams (10 ml) of 85% (not shown) was connected at the gas inlets as (by wt.) orthophosphoric acid was dissolved in 100 30 denoted by arrows 10 and 11 to provide as flow ml of deionized water. To prepare a novel polymer into chambers 8 and 9 and was also connected to blend membrane of the present invention, 12.5 ml the gas outlets as denoted by arrows 12 and 13 to (0.25 gram) of stock poly(vinyl alcohol) solution, 6.4 conduct gas away from the chambers. Gas-contain- ml (0.129 gram) of stock solution of poly(vinyl ing cylinders and gas flow control apparatus (not pyrrolidone) and 1.5 ml (0.219 gram) of stock solu- 35 shown) were used to provide gas to test the sensor tion of orthophosphoric acid were thoroughly ad- of fixture 3 in accordance with the herein described mixed, the mole ratio of the resulting blending experiments. Several cylinders of being 5:1:2 moles of poly (vinyl alcohol) to poly- hydrogen/nitrogen gas. mixtures were purchased; (vinyl pyrrolidone) to orthophosphoric acid. The so- and analysis (which was not checked) of the con- lution was then poured into an evaporation dish and 40 tent was supplied with each cylinder. the water was allowed to evaporation at room tem- Gas flows were established through the cham- perature for a period of 16 hours. The resulting film bers of the sample cell with both chamber pres- was transparent and possessed a thickness of sures at about one atmosphere, since the cham- about 63 microns. bers were vented directly to atmosphere by means This thin film membrane was cut into a disc 45 of a short length of tubing. One flow was pure having a 1 " (25.4 mm) diameter to form membrane hydrogen (hydrogen partial pressure of 1.0 atm) 1 of Figure 1 and platinum was sputter-deposited and the other was alternated between pure hy- onto each side of the disc for a period of about 5 drogen and a 10% by volume mixture of hydrogen minutes per side. The platinum deposits each had in nitrogen (hydrogen partical) pressure of 0.1 a thickness of abourt 400 Angstroms and an area so atm). The voltage across wires 3 and 4 was re- of about 1.5 square cm. Deposition was accom- corded by means of a standard laboratory strip plished by means of a Hummer II sputter deposi- chart recorder. When the flow to one chamber was tion system supplied by Technics Co. A biased alternated every 20 minutes, the voltage versus screen between the target and film was used to time plot was substantially perfect square wave reduce the electron flux to the membrane. There 55 form. Voltage varied consistently between 0.0 mil- are may alternative methods which could have livolts and 29.1 mv. Response was Nernstian; the been used to form the platinum deposits, such :.s calculated voltage is also 29.1 mv (at a room thermal evaporation or deposition by means of an temperature of about 22oC). Note that this is open 13 0 287 730 14

avail- circuit voltage. Voltage deviation from theoretical palladium is used. Other catalytic agents are in the art. The was less than about 1%. able and known to those skilled conductive; When the gases (100% hydrogen and 10% catalytic agent need not be electrically electrical hydrogen) were continuously flushed through the however, then the means for forming con- cell with no alternations for a period of 24 hours, 5 nection must be in contact with the catalytic agent of elec- the delta voltage remained at 29.1 mv for the over a broad area to facilitate movement duration of the test period. Upon connection of an trons from sites of the catalytic agent to the elec- Alter- ammeter to wires 3 and 4, the measured current trically conductive substance or electrode. in conduc- was 0.0133 ma at the beginning of the test period natively, catalyst may be embedded a and 0.0019 ma after 24 hours. The decrease in w tive matrix. Areas of membrane which are not adja- current flow over the test period is due to removal cent to catalytic agent are not effective in the of water from the membrane, since the membrane invention. Hydrogen ions spill over from the cata- and then was not completely dry. Current flow stabilized at lytic agent to the membrane protons the latter value. The resistance of the membrane move through the membrane. noted. When was measured when 100% hydrogen was flowing rs Response time of a sensor was through both chambers of the cell. For a 63 micron the 100% hydrogen and 10% hydrogen gas thick membrane with 1 .5 cm2 of platinum on each streams were alternated as described above, the surface, the resistivity was calculated from EMF time required for the voltage to change between and current data to be 3.7 x 106 ohm-cm. This steady state values was approximately 6 seconds. used is not applies to a membrane exposed to dry gas for 24 20 It should be noted that the sample cell hours. When a membrane which was not com- necessarily designed for quick response. have pletely dry was placed under test, the initial resis- Sensors utilizing the present membrane tance was lower. not yet been tested with sample gases containing Other membranes prepared from the above- small amounts of potential poisons. However, it is mentioned stock solutions were tested after sputter 25 believed that the present membranes will exhibit deposition of platinum. Voltage response was al- the same behavior as certain other membranes addition of carbon ways Nernstian, but current flow varied. For exam- which are tested. In these tests, volume ple, a membrane was prepared by admixing 12.5 monoxide in an amount of about 0.1% by ml (0.25 gram) of the poly(vinyi alcohol) stock in a hydrogen sample gas stream with a 100% solution, 6.4 ml (0.13 gram) of the stock poly(vinyl 30 hydrogen reference gas stream caused a change in pyrrolidone) solution and 1.0 ml (0.14 gram) of the EMF indicative of a large reduction in hydrogen stock phosphoric acid solution. The membrane had partial pressure. This apparent drop in hydrogen a mole ratio of 5:1:1.3 poly(vinyl alcohol) to poly- concentration was much larger than the expected (vinyl pyrrolidone) to phosphoric acid. The mem- drop due to the effect of dilution of sample gas brane was tested in a manner similar to that set 35 with CO. This is likely due to the competition byh forth above. Initial closed circuit curent was 1.3 x CO with molecular hydrogen for adsorption sites on 10-4 ma; after 17 hours and 22 hours under test, it platinum. No interference with the hydrogen con- 100 was 2x10-5 ma, corresponding to a hydrogen flux centration measurements was detectable when of 1.9 x 10-7 ft3/ft2-hr (5.8 x 10-8 m3.m2 hr). PPM by volume of CO was added to a sample gas Thickness of the membrane was 58 microns and 40 stream. It is expected that the present invention resitivity was 3.8 x 108 ohm-cm. cannot be used to measure the amount of hy- Another membrane was prepared by admixing drogen, or other gas, present in a sample gas stock solutions of poly(vinyl alcohol), poly(vinyl pyr- which also contains significant amounts of CO, or rolidone) and orthophosphoric acid in an amount other substances which interfere in the same man- sufficient to provide a molar ratio of 5:1 :4 poly(vinyl 45 ner, unless the amount of Co, or other substance, alcohol) to poly(vinyl pyrrolidone) to ortho- is known by other means or constant. The following phosphoric acid. The weight ratio was 30:16:54. 'potential poisons did not interfere with hydrogen The membrane was tested in a manner similar to concentration measurements made using the other that above. Initial closed circuit current was 0.022 membranes: hydrogen chloride (10 PPM), hydro- meth- ma; after 24 hours under test it was 0.016 ma and 50 gen sulfide (3%), carbon dioxide (100 PPM), after 72 hours, it drifted to 0.015 ma. The latter ane (3%), and butane (3%). All of the concentra- value corresponds to a hydrogen flux of 1.4 x 10-4 tions in sample gas shown in parenthesis are by ft3/ft2-hr (4.25 x 10-5 m3.m2 hr). Thickness of the volume. membrane was 80 microns and resistivity was 3.5 Membranes of the present invention have been 30oC x 105 ohm-cm at 24 hours. 55 tested at temperatures ranging from minus to In addition to platinum, palladium may be de- plus 50C. Nernstian behavior was observed though, posited on membranes for use as catalytic agent. of course, voltage varies with temperature. It may Nernstian voltage response will be observed when be possible to use these membranes at higher 15 0 287 730 16 temperatures, but no tests have been conducted. time required to change the hydrogen concentra- The above description of the invention has tion beyond the limits represented by points 31 dealt with hydrogen detection. It is clear that any and 32 can easily be measured in months or years, substance capable of dissociating in the presence the use of a solid reference is practical. Since the of a catalyst to yield hydrogen ions may be de- 5 flow of protons through the membrane substance tected in the same manner. An example is hy- may increase or decrease. When it passes above drogen chloride (using palladium or nickel catalyst point 32 or below point 31 , the reference substance if HCI is at room temperatgure). The Nernst equa- must be replaced. tion applies in a manner similar to that described Metal hydrides are, in general suitable for use herein. The invention is also usefl in detecting any m as solid reference substances in this invention, gasous component of a gas sample which is ca- since their phase diagrams are usually similar to pable of combining with hydrogen ions. Oxygen that of Figure 3. There may be several plateaus on may be used to illustrate this embodiment. Protons one diagram, so that there is a choice of reference passing through the membrane from a reference partial pressures while using one particular sub- gas chamber containing pure hydrogen will com- rs stance. Examples of metal hydrides include sub- bine with oxygen in a sample gas and electrons stances consisting of hydrogen an oxygen with from the external circuit (for example, wires 3 and tungsten, molybdenum, vanadium, or iridium, 4 of Figure 1) to form water in contrast to a hydrogen-zirconium-nickel compounds, hydrogen- hydrogen detector, wherein hydrogen is formed. zirconium-platinum compounds, and compounds of The Nernst equation is applicable; the Eo term is 20 hydrogen with platinum, palladium, zirconium, haf- not O, as it is when the same substance is present nium, vanadium, and niobium. Further examples on both sides of the membrane, and the partial comprise compounds of hydrogen and elements of pressure of oxygen to the one-half power times the atomic numbers of 3, 11, 12, 19 through 28, 37 partial pressure hydrogen divided into the partial through 48, 55 through 60, 62, 64, 72 through 78, pressure of water replaces the analogous term of 25 90 and 92. the equation. Hydrocarbons capable of hydrogena- The present membranes can be used with a tion or dehydrogenation may be subject of detec- solid reference substance. In order to illustrate this tion. Examples are cyclopentadiene, benzene, iso- embodiment of the present invention, the apparatus prene, cyclohexane, and isoamylene. of Figure 2 is fabricated. Palladium layer 42 of In the sensor of the present invention the EMF 30 approximately 1000 Angstroms thickness is developed is an open circuit value. Thus, theoreti- sputter-deposited on substrate 41. The substrate cally there is no electrons flowing in the external used is alumina. Choices of substrate may be circuit to combine with protons passing through the made from a wide variety of materials and are not membrane and therefore no change in reference a part of the invention. The palladium layer is hydrogen concentration. Of course, in actuality 35 moistened with Dl water and a membrane of the there is a small current flowing and reference hy- present invention 43 is placed over it. The mem- drogen concentration is constantly changing. A ref- brane has a thickness of approximately 50 microns. erence substance most possess the characteristic Platinum layer 44 is sputter-deposited on mem- of constant hydrogen partial pressure while hy- branes 43 to a thickness of approxiamtely 400 drogen concentration changes. Figure 3 depicts a 40 Angstroms. Wires 45 and 46 are attached to plati- portion of a phase diagram of a solid substance num layer 44 and palladium layer 42. The wires are suitable for use as a reference substance in the connected to voltmeter 47. In addition, switch 48 is present invention. For a sensor having a solid refer- provided in parallel with the voltmeter to complete ence substance to function properly, the hydrogen an external circuit when desired. concentration must lie on the plateau, or horizontal 45 The apparatus of Figure 2 is exposed to hy- portion, of the curve of Figure 3, the plateau lying drogen gas for about two hours, with switch 48 between points 31 and 32. As the hydrogen con- closed, to add hydrogen to palladium layer 42 to tent of the reference substance increases or de- provide the reference substance. Hydrogen dissoci- creases due to operation of the sensor, that is, as ated at platinum layer 44 and the protons passed hydrogen, or other substance, forms from the pro- so through membrane 43 while the electrons from the tons which pass through the membrane and the dissociated molecules flowed through the external electrons which flow in the external circuit, the circuit consisting of wires 45 and 46 and switch 48. point representing the reference substance moves It is not necessary to form the reference substance along the plateau. However, as long as the point is in place in this manner; palladium hydride could on the plateau the hydrogen partial pressure re- 55 have been deposited on the substrate. The pal- mains constant and, therefore, the reference sub- ladium hydride seved at both catalytic agent and stance is useful. It can be seen that a particular reference substance. reference substance has a limited life. Since the The apparatus depicted in Figure 2 is an exam- 17 0 287 730 18

membrane thickness pie of a sample cell or membrane housing. The form a thin film having a the therein set forth. After casting, the space adjacent to catalytic agent 44 comprises the within range miscible solvent such as water is removed sample gas chamber. The space occupied by ref- mutually such normal erence substance 42 comprises the reference by conventinal means as evaporation external chamber. Membrane 43 comprises a substantially 5 or forced evaporation by the application of and the desired imporous partition separating the chambers. It it heat, application of vacuum, etc., the thin film blend com- were desired to use a catalytic agent separate from membrane comprising recovered the reference substance, catalytic agent would be posited on the porous support may be depicted as a layer between the layers 41 and 43. and utilized in an appropriate gas sensor appara- After completion of fabrication of the sensor, it w tus. of the in- is placed in a closed chamber and pure hydrogen A polymer-blend membrane present vention is After a period of time sufficient gas is passed over the sensor. Switch 48 is open, prepared. stirred since it is used only during fabrication of the sen- to form the blend has passed, the solution is of find cloth which sor, i.e., during hydrogenation of the palladium. A and poured onto the top a glass valve in the outlet tubing from the closed chamber 75 was positioned in a standard Petri dish. The water of 46 hours is partially closed to throttle hydrogen flow out of is allowed to evaporate for a period the chamber and increase chamber pressure. Vol- and the resulting membrane composite comprising or with, the tages at various pressures are recorded and found a thin film membrane composited on, microns is to match values calculated using the Nernst equa- glass gloth having a thickness of 95 tion. 20 recovered. The composite membrane is cut into a " The reference partial pressure of hydrogen circle having a 1 (25.4 mm) diameter and platinum which is used in the Nernst equation to determine electrodes 1 square cm in area are sputter-dis- EMF is easily calculated. For example, niobium persed on each side of the membrane. The mem- similar to hydride has a hydrogen partial pressure of approxi- brane is then placed in a sample housing is mately 10-6 atmosphere, as calculated by the rela- 25 that of Figure 1 for test. The sensor response tionship Nernstian. However, the resistivity is higher. As an illustration of the greater structural strengh of a polymer blend composited on a po- _B_ In P = rous support when compared to unsupported mem- 2 ~KT R 30 branes, reference may be made to previous work involving two component polymer blend mem- where A = enthalphy between the two hydride branes. Two polymer blend membranes were pre- expressed in kcal/gm-atom, B = entropy phases pared. The polymer blend was prepared by dis- between the two hydride phases expressed in solving 0.5 gram of poly(vinyl alcohol) having a cal/gm-atom-oK,P = P2 or P1 as defined above, 35 molecular weight of 16,000 and 0.2 ml of ortho- and R and T are as defined above. phosphoric acid in boiling deionized water. The It be seen that a membrane mounted in a can resulting blend was cast onto a glass cloth having a in 1 and 4 be cell such as depicted Figure may thickness of 30 microns. A second blend was pre- subjected to high differential pressures which may pared by admixing like proportions of poly(vinyl deform or burst the membrane. A composite mem- 40 alcohol) and orthophosphoric acid and casting the brane be fabricated by casting a solution may resulting blend onto a Petri dish without a support. described above on a flexible porous prepared as After removal of the solvent, the two membranes A supported membrane assembly may be support. were recovered. membrane which is cast fabricated by attaching a Each membrane was placed in a holder which and dried as above to a rigid porous support. 45 enabled air pressure to be exerted against one side be accomplished by moistening Attachement may of the membrane while the other side was at at- the surface of the membrane and support and mospheric pressure. When exposed to 5 psig (34 the moistened surfaces together. The pressing kPag), the unsupported membrane burst at its cen- moisture will evaporate. ter in less than 1 minutes. At 2 psig (14 kPag), It is contemplated that any porous substrate so another sample of unsupported membrane bulged which a structural strength greater than possesses and was permanently deformed. The composite the thin film membrane be employed. Some may membrane was subjected to various pressure lev- of these supports will include examples porous els in 5 psig (34 kPag) increments with one minute such glass cloth, polysulfone, cel- compounds as hold time between increases in pressure. It burst at lulose acetate, polyamides, ceramics such as alu- 55 35 psig (241 kPag), shearing at the edges of the etc., which have been fab- mina, glass, porcelain, test hole in the holder. The point of failure leads ricated to the necessary porosity. The possess one to believe that holder design caused the shear- amount of blend which is cast upon the flexible ing and that a higher burst pressure would be porous support will be that which is sufficient to

10 19 0 287 730 20 observed in a different holder. stance suitable for use as an electrolyte in the As is common in many analysis instruments, concentration cell of this invention which has been the sample gas provided to a sensor may require formed into a particular physical entity, either with conditioning in order to achieve effective detection. or without additional substances, for use in the Of course, any particulate matter and liquid 5 invention. Where an electrolyte element surface is droplets are removed. The extend of conditioning referred to as in common with a gas or gas cham- depends on the particular gas involved and its ber, the meaning is the same as exposed to a gas state. For example, an extremely hot gas must be or gas chamber and such reference does not pre- cooled to a sufficiently low temperature so as not clude the presence of catalytic agent and elec- to degrade the apparatus by melting sensor com- jo trades at or covering the surface. Gas may diffuse ponents, including the membrane. A relatively cold through covering material. Sample gas chamber as may need to be heated to a temperature which refers to any space in which gas which is the promotes a reasonable response time of the ap- subeject of detection exists. For example, a sample paratus. A related factor to be considered is the cell can form a part of a pipeline wall such that the necessity for knowing the temperature for use in 75 gas flowing in the pipeline is the sample gas and the Nernst equation. The temperature may be mea- the pipeline is the sample gas chamber. The term sured or the temperature may be maintained at a "gas" is used herein to include vaporized liquids pre-established constant value. If the calibration regardless of boiling point characteristics of the gas temperature is maintained at the same value, substance. As used herein, miscible means ca- the matter is simplified. Water vapor and/or other 20 pable of being mixed where there may only be a substances are often removed from or added to a very small degree of solubility. As is familiar to sample gas stream. Other sample-conditioning those skilled in the art, the terms concentration and techniques may be required. For example, or in a partial pressure are often used interchangeably; situation where the concentration of the unknown partial pressure expresses concentration. Compati- substance is extremely large and capable of satu- 25 ble may be taken to mean that compatible com- rating the apparatus, the sample may be diluted by pounds will form the polymer-blend composition of addition of a known amount of inert gas. The actual matter. concentration of undiluted sample can then easily The design of sample, or detectors, or mem- be calculated. brane housings, is well known. Many configurations A detector may take many forms. A portable 30 are possible; Figure 1 provides an example of one battery-operated unit may be used as a "sniffer" to type. Figure 4 depicts an embodiment of the inven- detect the presence in the atmosphere of a particu- tion where membrane housing 56 is mounted lar gas due to leakage from a closed system. A (attachment means not shown) in the wall of pipe- detector may be permanently mounted in a particu- line 57. Gas is present and may or may not be lar location to detect leaks. When conditioning is 35 flowing in the pipeline. The sample gas chamber is not required, a detector may be fabricated for the interior of the pipe adjacent to housing 56, insertion directly into a process pipeline. When a while the reference chamber is defined by housing gas sample must be conditioned, a small 56 and solid electrolyte membrane 60. Reference sidestream may be withdrawn from a process pipe- gas is sealed into the reference gas chamber; thus line on a continuous or intermittent basis and 40 it is necessary to replace the reference gas at passed through a sample gas chamber. A quantity intervals upon its changing in concentration as a of reference gas may be sealed into a reference result of the cell reaction sufficiently to affect sen- gas chamber instead of providing a continuous sor results. It should also bo noted that the mem- flow. brane is not expected to be totally impermeable As used herein, the term "detection" includes 45 and that substances in addition to hydrogen ion not only sensing presence or absence of the de- may pass through it. Permeability experimentation tected substance, but measurement of the amount has not been accomplished, except to the extent of substance present, either in order of magnitude indicated herein. Alternatively, the reference cham- or exact amounts. Gas sample refers to any portion ber may contain a solid reference substance. Elec- of a gas which is the subject of detection. A gas 50 trically conductive catalytic agent is present on sample may have only one component. Sample both sides of membrane 60, as shown by refernce cell or membrane housing or test fixture refers to a numbers 55 and 59. Wire leads 53 and 54 extend housing or fixture which holds an electrolyte ele- outside the apparatus for connection to voltage ment and other required components. Figure 5 detection means. Retaining rings 52 and 58 serve depicts a membrane housing. Sensor is a general 55 to hold membrane 60 in place at its perimeter term denoting sensing apparatus, such apparatus (exact detail now shown). Screen 51 is provided to comprising a membrane housing. Membrane or protect membrane 60 from the impact of large electrolyte element refers to an ion-conducting sub- particles or objects. If a greater membrane surface

11 21 0 287 730 22

of Claim 1 further character- area than that of Figure 4 is desired, a detector 2. The apparatus in that said catalytic comprise a susb- may be fabricated in the form of a cylindrical probe ized agents of for insertion into a pipeline. Membrane material tance selected from a group consisting platinum, and thereof. may be placed over a perforated pipe which is palladium alloys forth in Claim 1 in sealed at one end. The interior of the perforated 5 3. The apparatus as set is in said pipe is the reference gas chamber. It may be which said inorganic compound present of from about 1 desirable to protect the membrane and catalytic membrane in an amount in a range said polymer agent by covering it with a porous substance to about 75 weight percent, organic in said membrane in an through which sample gas can pass. or copolymer is present about 1 to about 49 Referring to Figure 5, an embodiment of the io amount in a range of from is invention in which a membrane 66 serves as a part weight percent, and said organic compound in amount in of partition 65 is shown. Partition 65 separates a present in said membrane an a range 1 about 49 percent. sample gas chamber from a reference gas cham- of from about to weight forth in Claim 1 in ber. Catalytic agent 67 and 68 wire leads 63 and 4. The apparatus as set thickness of 64 perform the functions discussed above. 75 which said membrane possesses a about 0.1 to about 500 microns. 5. The apparatus of Claim 1 in which said Claims membrane is composited with a flexible porous support. further character- 1. Apparatus for detection, in a gas sample, of 20 6. The apparatus of Claim 1 that said reference substance is a solid and a gaseous component which is capable, in the ized in with said second catalytic and presence of a catalytic agent, of dissociating to is in contact agent known yield hydrogen ions or of combining with hydrogen exhibits a substantially constant hydrogen detection ions comprising: partial pressure during use of said ap- (a) a thin film polymer-blend, proton-con- 25 paratus. 1 further character- ducting membrane which comprises a combination 7. The apparatus of Claim and second of an organic polymer or copolymer, an inorganic ized in that said reference substance compound selected from the group consisting of catalytic agent comprise palladium hydride. further character- phosphoric acids, sulfuric acid, heteropoly acids, 8. The apparatus of Claim 1 of and an organic compound selected from the group 30 ized in that said membrane is comprised poly- and ortho- of polymers and copolymers having monomer units (vinyl alcohol), poly(vinyl pyrrolidone) containing nitrogen, oxygen, or sulfur atoms, which phosphoric acid. in of organic compound is compatible with said inor- 9. A method for detection, a gas sample, is in the ganic compound and said organic polymer or a gaseous component which capable, to copolymer: 35 presence of a catalytic agent, of dissociating (b) a membrane housing comprising a sam- yield hydrogen ions or of combining with hydrogen said ple gas chamber and a chamber containing a refer- ions, such method comprising introducing gas of the ence substance separated by a partition compris- sample into the sample gas chamber ap- Claims 1 to 8, ing said membrane, said membrane having a first paratus characterized in any one of surface in common with the sample gas chamber 40 measuring the EMF signal generated therein and exis- and a second surface in common with the refer- correlating the resulting EMF signal with the ence substance chamber; tence or amount of said gaseous component. (c) a first catalytic agent effective to promote 10. The method of Claim 9 further character- dissociation and combination of hydrogen ions in ized in that said gaseous component is elemental contact with said first surface and a second cata- 45 hydrogen or elemental oxygen. lytic agent effective to promote dissociation and 11. A thin film polymer-blend, proton-conduct- combination of hydrogen ions in contact with said ing membrane which comprises a combination of second surface; an organic polymer or copolymer, or inorganic of (d) means for forming electrical connection compound selected from the group consisting acids in operative contact with said first catalytic agent at so phosphoric acids, sulfuric acid, heteropoly said first surface and with said second catalytic and salts of heteropoly acids, and an organic com- of and agent at said second surface and for measuring an pound selected from the group poymers nitro- EMF signal between said surfaces; and, copolymers having monomer units containing (e) means for introducing the gas sample gen, oxygen or sulfur atoms, which organic com- into said sample gas chamber and means for cor- 55 pound is compatible with said inorganic compound relating the resulting EMF signal with the existence and said organic polymer. or amount of said gaseous compound.

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DOCUMENTS CONSIDERED TO BE RELEVANT Category Citation of document with indication, where appropriate, Relevant CLASSIFICATION OF THE . of relevant passages to claim APPLICATION ant. C1.4) Y US-A-4 560 444 (A.J. POLAK) 1,2,4,6 G 01 N 27/56 * Abstract; claims; figures * -11

D,Y US-A-4 500 667 (A.J. POLAK) 1,2,4, * Columns 1,2; column 3, lines 1-33 * 11

Y SENSORS AND ACTUATORS, vol. 9, no. 1, 1,2,8, February 1986, pages 1-7, Elsevier 11 Sequoia, Lausanne, CH; A.J. POLAK et al . : "Applications of novel proton-conducting polymers to hydrogen sensing" * Pages 1,2; conclusion *

D,A US-A-4 179 491 (A.T. HOWE)

A US-A-4 594 297 (A.J. POLAK)

D,A SOLID STATE IONICS, vol. 7, 1982, pages 53-56, North-Holland Publishing Co., NL; J.S. LUNDSGAARD et al . : "A novel TECHNICAL FIELDS hydrogen gas sensor based on hydrogen SEARCHED ant. CI.4) uranyl phosphate" G 01 N 27/56 H 01 M 8/10

The present search report has been drawn up for all claims Place of search Dale of completion of the search Examiner THE HAGUE 17-12-1987 CALLEWAERT-HAEZEBROUCK

CATEGORY OF CITED DOCUMENTS T : theory or principle underlying the invention E : earlier patent document, but published on, or X : particularly relevant if taken alone after the filing date Y : particularly relevant if combined with another D : document cited in the application document of the same category L : document cited for other reasons A : technological background O : non-written disclosure & : member of the same patent family, corresponding P : intermediate document document