Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/46—Removing components of defined structure
  • B01D53/62—Carbon oxides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/42—Platinum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/06—Washing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/12—Oxidising
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/889—Manganese, technetium or rhenium
  • B01J23/8892—Manganese

Definitions

• This alloy is contacted with an oxidizing acid for a time period and at a temperature and acid concentration sufiicient to dissolve a portion of the second metal.
• the alloy is subsequently contacted with an alkali metal hydroxide under conditions sufiicient to convert the aluminum at the surface of the alloy to aluminum hydroxide.
• the alloy thus treated is then heated in the presence of oxygen for a time period and at a temperature suflicient to convert the aluminum hydroxide to aluminum oxide.
• the present invention relates to a method for preparing improved metallic catalysts and catalyst supports having high surface area and to the catalysts and catalyst supports made thereby.
• the catalysts of the present invention are prepared from an alloy which comprises aluminum and a second metal, the second metal being soluble in oxidizing acids.
• the alloy is first contacted with an oxidizing acid for a time period and at a temperature and acid concentration suflicient to dissolve a portion of the second metal.
• the alloy is contacted with an alkali metal hydroxide under conditions sufl'icient to convert the aluminum at the surface of the alloy to aluminum hydroxide.
• the alloy is then heated in the presence of oxygen for a time period and at a temperature sufficient to convert the aluminum hydroxide to aluminum oxide (alumina).
• alumina particularly in the gamma form, not only has catalytic activity by itself, but also serves as an excellent catalyst support, particularly for noble metals.
• a portion of the metal making up the alloy employed is dissolved in the oxidizing acid, while the aluminum is not, thus creating tiny valleys where the dissolved metal is removed, while leaviing peaks where the aluminum remains. The presence of these peaks and valleys creates a high surface area.
• the acid employed for the acid treatment step be an oxidizing acid.
• the reason for this requirement is that the oxidizing nature of the acid produces an oxide film on the surface of the aluminum contained within the alloy. This oxide film has a very low solubility in the acid, and protects the aluminum from attack.
• the second metal which on the other hand, is soluble in the oxidizing acid, is attacked and dissolved by the acid. While it is possible that oxidation as well as dissolution of this second metal occurs, the presence of the two phenomena makes no difference, and for purposes of the present invention, metals which are soluble in oxidizing acid includes metals that are oxidized by the oxidizing acid, and that have oxides that are soluble in oxidizing acids.
• the preferred oxidizing acids for use in accordance ice with the present invention is nitric acid.
• other acids such as phosphoric acid and aqua regia, can also be employed.
• aluminum-containing alloys may be employed with the present invention.
• such alloys should contain from about 4.5 to about 25% aluminum by weight, and preferably such alloys comprise about 4.5 to 15% aluminum because of the superior mechanical properties of alloys with lower aluminum content.
• the identity of the second, oxidizing acid-soluble metal depends upon a number of factors, the most important of which are the physical and mechanical properties desired in the alloy.
• the most preferred second metal is iron, which may be present in amounts from about 6% to about by weight. Alloys containing only aluminum and iron are highly suitable. Other second metals that may be alloyed with the aluminum, and which are also soluble in the oxidizing acids, include nickel, molybdenum, titanium, vanadium and tungsten. Combinations of these metals, with or without iron, can also be employed. Still other metals may also be used provided that a suitable alloy may be prepared with aluminum, and also provided that these other metals are soluble in oxidizing acids. As with iron, the foregoing metals may be alloyed with the aluminum in total amounts ranging from about 6 to 85 by weight.
• Suitable additional oxidizing acid-soluble metals are chromium, cobalt, and manganese. Of the latter metals, chromium is particularly suitable, and chromium containing alloys have excellent characteristics in high-temperature applications. When chromium, cobalt, and manganeses are employed, they may be incorporated into the alloy in amounts up to about 32%. Above about 32%, the alloy sufiers a severe loss in mechanical strength. While there is: no required minimum, generally little effect on the alloy is seen when the chromium, cobalt, and/or manganese is below about 3% by weight.
• a particularly suitable alloy for use in accordance with the present invention is one containing about 4.5 to 15% by weight aluminum, about 6% to 85 by weight iron, and anywhere from 0 to 32% chromium.
• An especially preferred alloy contains about 70% iron, about 5% aluminum, and about 20% chromium, the remainder of the alloy being made up of additional metals and non-metals in minor proportions, such as cobalt, silicon, and manganese.
• metal ribbon or thin metal sheets are preferred, although the method of the present invention may be employed to prepare catalysts in the form of screens, granules, or any other desired form.
• the preparation of catalysts in accordance with the method of the present invention is commenced by contacting an alloy as described above with an oxidizing acid for a time period and at a temperature and acid concentration sufiicient to dissolve a portion of the oxidizing acid-soluble metal.
• the acid concentration may be varied over a wide range, generally any where from about 2.5% to by weight. Fuming acids may also be employed. It is preferable, however, to maintain the acid concentartion in the range of about 8% to about 25% by weight, as better control of the metal dissolution can be exerted.
• the temperature at which the acid is contacted with the metal may also vary over a wide range, and is not critical. Of course, with less concentrated acids, high temperatures ar often required in order to obtain acceptable dissolution speeds. As a general matter, the temperature of the acid may vary anywhere from a point just above the freezing point of the acid to very high temperatures, up to the decomposition temperature of the acid, provided that pressure is employed to prevent the acid from boiling away. As a practical matter, how ever, the treatment temperature should be at least about 20 C., preferably in the range of about 20 to 100 C., and more preferably in the range of about 20 to 75 C.
• the time of treatment will also vary over a wide range, and will be dependent upon both the temperature and the acid concentration.
• the time temperature, and concentration factors should always be regulated so that only a portion of the oxidizing acidsoluble metal is dissolved. That is, if the treatment is too severe, the alloy can 'be greatly weakened mechanically, or even caused to disintegrate. On the other hand, if the conditions are insufiiciently severe, the surface area may not be increased as much as desired.
• time of treatment as a practical matter, treatment times in the range of about one minute to 90 minutes may be employed, with times in the range of about 2 to 20 minutes being preferred.
• the composition of the alloy itself including the proportion of aluminum and the identity of acid-soluble metals, must be taken into consideration. That is, the lower the percentage of acid-soluble metals, and the less the acid solubility, the more severe are the conditions that must be employed.
• the alloy is preferably rinsed, and is then ready for the conversion of the aluminum to aluminum hydroxide.
• the aluminum at this point, at least at the surface, will be in the form of aluminum oxide as a result of the action of the oxidizing acid.
• this aluminum oxide is next converted to aluminum hydroxide, which forms a porous gel of high surface area.
• the hydroxide is then reconverted to the oxide, and preferably calcined to convert it to gramma alumina, a crystalline form of high catalytic activity.
• the alloy is treated with an alkali metal hydroxide.
• the conditions must be suflicient to convert the aluminum at the surface of the alloy (which is mainly in the form of aluminum oxide) to aluminum hydroxide.
• the hydroxide is preferably in the form of an aqueous solution ranging in concentration from about 5% by weight to a saturated solution. In the preferred embodiment, the concentration of the alkali metal hydroxide is about 50 to 87% by weight.
• the preferred alkali metal hydroxide is sodium hydroxide.
• the time and temperature of treatment may also be varied over a wide range. Neither of these factors is critical, and they are interrelated to each other as well as to the concentration of the solution. However, in most situations it is preferred to maintain the temperature in the range between the freezing point and the boiling point of the solution, as operation in a pressurized system is inconvenient and unnecessary. Preferably the temperature is maintained in the range of about 20 to 100 C.
• the time of treatment also is not critical, but as a practical matter should be maintained in the range of about 2 to 90 minutes, and preferably about 20 to 40 minutes.
• the alkali metal hydroxide treatment is most preferably performed two or more times, with the alloy being dried between the steps. When the hydroxide treat ment is performed more than once, the total treatment time for all of the steps should be the amounts indicated above.
• the alloy is subjected to a heating step.
• Such heating is accomplished in the presence of oxygen to convert the aluminum hydroxide to aluminum oxide.
• the temperature should also be suflicient for such conversion to take place.
• the catalyst is first dried at a temperature in the range of about 60 to 250 C. for a time period of at least about ten minutes.
• the alloy is heated to a temperature in the range of about to 450 0., preferably a temperature toward the upper end of this range, for a time period of not less than 20 minutes, and preferably for at least about 30 minutes.
• the amount of oxygen present in the gas passed over the catalyst during the oxidation step depends upon a number of factors, including the temperature. That is, the higher the temperature, the lower the concentration of oxygen required. Also, when it is desired to prepare a surface high in alumina, it is preferred that the stream passed over the alloy be relatively high in oxygen content. On the other hand, when a surface relatively low in alumina and high in the oxides of other metals contained in the catalyst is desired, such as cobalt, molybdenum, manganese, and/ or chromium oxides, the amount of oxygen in the stream should be relatively low. As a general matter, the oxygen may be varied anywhere from about 2 to 75% by volume. The remainder of the gas stream is preferably an inert gas, such as nitrogen, helium, or the like.
• calcining the alloy in order to convert the alumina to the gamma crystalline form.
• Such calcining is accomplished by heating the catalyst to a temperature of about 300 to 750 C. and preferably about 500 C. to 750 C. for a period of at least about 30 minutes.
• Such conversion of the alumina to the gamma form is particularly desirable where it is contemplated that the catalyst will be employed alone, or in combination with a noble metal, and where the alumina itself will have a significant catalytic effect.
• calcining of the catalyst is less important.
• the catalyst of the present invention may be used as a high surface-area support for virtually any of the well known catalytic metals. Included among such catalysts are the metals of Group VIII of the Periodic Table, the rare earths, and other metals including silver, titanium, manganese, copper, chromium, cadmium, molybdenum, vanadium, tungsten, rhenium, thorium, and actinium. Various combinations of these catalysts are also advantageously employed in a wide variety of catalyst applications. A particularly important application of catalysts of the present invention is in air pollution control applications, wherein it is desired to oxidize or reduce gases in order to destroy pollutants.
• the catalyst without any additional catalytic metal deposited performs as an excellent oxidation catalyst, as a result of the presence of gamma alumina. However, its performance is improved by the presence of a Group VIII noble metal.
• An oxidizing catalyst having a preference for certain hydrocarbons may be prepared, for example, by depositing manganese and cobalt on the surface.
• a cracking catalyst may be prepared by depositing, for example, a combination of manganese, cobalt, and copper..
• a catalyst having characteristics lying between those of a cracking catalyst and of an oxidation catalyst may be prepared, for exam ple, by depositing upon the surface a combination of molybdenum, titanium and chromium.
• An almost infinite variety of other catalysts may be prepared, as will be appreciated by those skilled in the art.
• the deposition of catalytically active metals upon the catalysts of the present invention may be accomplished either by electroplating or by chemical deposition, i.e., by chemical reduction of salt solutions. Both of these methods are well known in the art.
• the catalytically active metal When the catalytically active metal is deposited by electrodeposition, it will probably be deposited primarily in the crevices or valleys, since the alumina in the catalyst will have a relatively low conductivity. Thus, a catalyst which has exposed alumina may be prepared. On the other hand, when the metal is deposited by the reduction of salt solution, it is deposited evenly over the entire surface area. Depending upon the amount deposited, the alumina may or may not be exposed. Exposed alumina is particularly desirable in the case of oxidation catalysts, but is relatively unimportant in many other catalyst applications.
• catalytic metals must generally be activated by conversion to the oxide form, and by contacting them with a stream of hydrocarbons subsequent to deposition. Such activation may also be performed in accordance with the present invention by procedures which are well known in the art.
• an additional layer of alumina may also be applied.
• Such an additional layer of alumina is particularly desirable, for example, where an alumina catalyst is desired, or where a catalyst high in alumina content and containing an additional catalytic metal, such as a Group VIII noble metal, is desired.
• an additional layer of aluminum is first electroplated onto the catalyst by well known techniques. Such electroplating is conducted subsequent to the completion of the catalyst from the base alloy, which completion would ordinarily include the calcining step where active alumina is desired.
• the catalyst containing this additional layer of metallic aluminum is then contacted with an alkali metal hydroxide, reheated, reoxidized, and recalcined as was the original catalyst.
• the repeating of these steps converts the additional aluminum deposited to gamma alumina, thus producing a catalyst having a very high surface area, and having a surface which is almost entirely gamma alumina.
• the alloy employed in this example contained 70.85% of iron, 22.0% chromium, 4.5% aluminum, 1.0% manganese, 1.0% silicon, 0.5% cobalt, and 0.15% carbon, all of the foregoing percentages being by weight.
• the alloy was in the form of a ribbon having a width of about 4 millimeters, and a thickness of about 0.35 to about 0.45 millimeter. This ribbon was crimped, cut into pieces 5 centimeters in length, and placed between a 3-mesh and a l5-rnesh screen.
• the screen material had a low aluminum content, as a high mechanical strength was desired.
• the catalyst mat thus prepared was immersed in nitric acid having a concentration of about by weight.
• the temperature was maintained in the range of about 50 to 75 C.
• the acid was continuously agitated with a recycle pump, and was filtered as it was recycled.
• the alloy was maintained in contact with the acid for 12 minutes by being continuously dipped into the acid, removed, and reimmersed, in order to allow the dissolved metal, primarily iron, to run off.
• Fresh acid was introduced into the recycle stream in order to maintain the acid concentration in the range of 8 to 15% by weight. Spent acid was withdrawn to maintain a constant volume in the system.
• the alloy was rinsed, and was then immersed in an aqueous solution of sodium hydroxide having a concentration of 87% by weight.
• the temperature was maintained in the range of 45 to 65 C. and the treatment time was about 10 minutes. In order to avoid disturbing the delicate film of aluminum hydroxide, no agitation was employed during this alkali treatment.
• excess liquid was permitted to drip on the alloy, and the mat was then placed in a stream of hot air at a temperature of 150 C. This temperature was gradually raised to 300 C. over a time period of about 10 minutes. The 300 C. temperature was main tained for 30 minutes, in order to completely oxidize the aluminum hydroxide to aluminum oxide.
• the immersion in the sodium hydroxide solution was then repeated two more times, and after each repetition the aforementioned drying and oxidation steps were repeated.
• the oxygen in the air stream was enriched to a total oxygen content of 35-40% to insure complete oxidation.
• the temperature was raised to 500 C., and maintained at this level for 30 minutes, in order to convert the alumina to the gamma form.
• the catalyst prepared as above was employed as an oxidation catalyst to oxidize an air stream contaminated with carbon monoxide to carbon. dioxide, and showed excellent catalytic activity.
• EXAMPLE II A platinum catalyst was deposited upon the catalyst prepared in accordance with Example I according to the following procedure. First, 18.75 grams of chloroplatinic acid (H PtCl were dissolved in 300' grams of water and neutralized with sodium carbonate. This solution was then diluted to allow the application of 0.5 to 1.0 gram of PtCl equivalent to every square centimeter of surface area of the catalyst. A second solution was prepared by dissolving 15 grams of sodium carbonate and 10 grams of sodium formate in 300 ml. of water, and by diluting this solution to 2700 ml.
• H PtCl chloroplatinic acid
• the catalyst was removed from-the solution and heated in air at C. for 30 minutes, and then washed in cold water to remove residual sodium chloride. The catalyst was then heated in air at 350 C., the temperature being gradually increased to 500 C. over a time period of about 30 minutes.
• To activate the catalyst about l2-15 grams of toluol per cubic meter of air were periodically added to the air stream. This procedure activates the catalyst by changing its crystalline structure, as is well known in the art.
• a method for preparing a metallic catalyst having a high surface area from an alloy comprising up to about 25% aluminum and a second metal, said second metal being soluble in oxidizing acids comprising: contacting said alloy with an oxidizing acid for a time period and at a temperature and acid concentration sufiicient to dissolve a portion of said second metal; subsequently contacting said alloy with an alkali metal hydroxide under conditions sufiicient to convert aluminum at the surface of said alloy to aluminum hydroxide; and heating said alloy in the presence of oxygen for a time period and at a temperature sufiicient to convert said aluminum hydroxide to aluminum oxide.
• said second metal is selected from the group consisting of iron, nickel, molybdenum, titanium, vanadium, tungsten, and mixtures thereof.
• catalytically active metal is a noble metal from Group VIII of the Periodic Table.
• the method as defined in claim 3 further comprising steps of electroplating an additional layer of aluminum onto said alloy subsequent to said calcining; contacting said alloy and said additional layer of aluminum with an alkali metal hydroxide under conditions sufficient to convert said additional layer of aluminum to aluminum hydroxide; preheating said alloy and the presence of oxygen for a time period and at a temperature sufiicient to convert said aluminum hydroxide to aluminum oxide; and calcining said catalyst subsequent to said reheating at a temperature and for a time period sufficient to convert said aluminum oxide to the gamma form.
• said alloy further comprises a metal selected from the group consisting of chromium, cobalt, and manganese, and mixtures thereof.
• a method for preparing a metallic catalyst having a high surface area from an alloy comprising about 4.5% to about 25% aluminum, by weight, and a second metal, said second metal being soluble in oxidizing acids comprising: contacting said alloy with an oxidizing acid having a concentration of at least about 2.5% by weight for a time period of about 1 to 90 minutes and at a temperature of at least about 20 C., whereby to dissolve a portion of said second metal; subsequently contacting said alloy with an aqueous solution of an alkali metal hydroxide having a concentration of at least about 5% by weight for a time period of about 2 to minutes and at a temperature of about 20 to C., whereby to convert aluminum at the surface of said alloy to aluminum hydroxide; drying said catalyst at a temperature of about 60 to 250 C. for a time period of at least about 10 minutes; and heating said alloy in an atmosphere containing about 2% to 75% oxygen, by volume, for a time period of at least about 20 minutes and at a temperature of about 100 to 450 C
• the method as defined in claim 24 further comprising the steps of electroplating an additional layer of aluminum onto said alloy subsequent to said calcining; contacting said alloy and said additional layer of alumi num with an aqueous solution of alkali metal hydroxide having a concentration of at least 5% by weight for a time period of about 2 to 90 minutes and at a temperature of at least about 20 0., whereby to convert said additional layer of aluminum to aluminum hydroxide; redrying said catalyst at a temperature of about 60 to 250 C. for a time period of at least about 10 minutes; and reheating said alloy in an atmosphere containing about 2% to 75 oxygen, by volume, for a time period of at least about 20 minutes and a temperature of about 100 to 450 C.
• said alloy further comprises a metal selected from the group consisting of chromium, cobalt, manganese, and mixtures thereof.
• a method for preparing a catalyst having a high surface area from an alloy comprising about 4.5% to about 25% aluminum, by weight, and about 6% to about 85% iron by weight comprising: contacting said alloy with nitric acid having a concentration of at least about 2.5% by weight for a time period of about 1 to 90 minutes and at a temperature of about 20 to 100 C., whereby to dissolve a portion of said iron; subsequently contacting said alloy with an aqueous solution of sodium hydroxide having a concentration of at least about 5% by weight for a time period of about 2 to 90 minutes at a temperature of about 20 to 100 C., whereby to convert the aluminum at the surface of said alloy to aluminum hydroxide; drying said catalyst at a temperature of about 60 to 250 C.
• catalytically active metal selected from the group consisting of metal from Group VIII of the Periodic Table, rare earths, silver, titanium, manganese, copper, chromium, cadmium, molybdenum, vanadium, tungsten, rhenium, thorium, actinium, and mixtures thereof.
• catalytically active metal is a noble metal from Group VIII of the Periodic Table.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Biomedical Technology (AREA)
• Health & Medical Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Catalysts (AREA)
• Chemically Coating (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22246233

Family Applications (1)

Country Status (7)

Cited By (16)

Families Citing this family (3)

Family Cites Families (1)

• 1970
  • 1970-12-02 US US00094627A patent/US3712856A/en not_active Expired - Lifetime
• 1971
  • 1971-10-26 GB GB4971571A patent/GB1325392A/en not_active Expired
  • 1971-10-26 CA CA126,129A patent/CA983001A/en not_active Expired
  • 1971-10-28 AU AU35106/71A patent/AU451454B2/en not_active Expired
  • 1971-12-01 FR FR7143149A patent/FR2117250A5/fr not_active Expired
  • 1971-12-01 DE DE2159664A patent/DE2159664C2/de not_active Expired
  • 1971-12-02 JP JP46097521A patent/JPS5126913B1/ja active Pending

Also Published As

Similar Documents