US3836436A - Process for the electrochemical manufacture of silver containing catalysts - Google Patents

Process for the electrochemical manufacture of silver containing catalysts Download PDF

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Publication number
US3836436A
US3836436A US00275937A US27593772A US3836436A US 3836436 A US3836436 A US 3836436A US 00275937 A US00275937 A US 00275937A US 27593772 A US27593772 A US 27593772A US 3836436 A US3836436 A US 3836436A
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silver
current
process according
solution
feeding
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US00275937A
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English (en)
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L Rivola
V Mormino
B Notari
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SnamProgetti SpA
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SnamProgetti SpA
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D301/00—Preparation of oxiranes
    • C07D301/02—Synthesis of the oxirane ring
    • C07D301/03—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds
    • C07D301/04—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen
    • C07D301/08—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase
    • C07D301/10—Synthesis of the oxirane ring by oxidation of unsaturated compounds, or of mixtures of unsaturated and saturated compounds with air or molecular oxygen in the gaseous phase with catalysts containing silver or gold
    • 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
    • B01J23/48—Silver or gold
    • B01J23/50—Silver
    • 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
    • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
    • B01J37/348—Electrochemical processes, e.g. electrochemical deposition or anodisation
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C5/00—Electrolytic production, recovery or refining of metal powders or porous metal masses
    • C25C5/02—Electrolytic production, recovery or refining of metal powders or porous metal masses from solutions
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Definitions

  • ABSTRACT A process whereby a silver containing catalyst is produced, in a particle size ranging from 300 to 1,500 A, through the pulsed electrolysis of a solution of a silver salt (e.g., silver nitrate) in the presence of a complexing agent (e.g., ammonia) wherein current is fed to the solution for spaced periods of a few seconds duration.
  • a silver salt e.g., silver nitrate
  • a complexing agent e.g., ammonia
  • a current inversion lasting from a few seconds is effected.
  • the silver is obtained in the form of a powder which, after washing, can be used directly or supported on a ceramic material as catalyst for the production of ethylene oxide.
  • More particularly the present invention is related to the manufacture of silver containing catalysts useful for the catalytic production of ethylene oxide.
  • the process according to present invention for producing silver catalysts comprises a pulsed electrolysis of silver salt solutions in presence of complexing agents.
  • pulsed electrolysis it is meant an electrolysis wherein the current supply at intervals is broken off.
  • This breaking off the current can be in some case followed by an inversion of the supplying of the current.
  • the periods of feeding the current through the solution can be comprised between 3 and seconds followed by breaking off periods comprised between 3 and 60 seconds; possible after 10-15 cycles of supplying and breaking off the current a current inversion can be effected for a period preferably comprised between I and 60 seconds.
  • the solutions of silver salts advantageously used according to the invention can consist of silver nitrate, silver chloride, silver sulphate, silver acetate and silver.
  • concentrations of said solutions of silver salts can be comprised between 0.1 g and 10 g of silver per liter of solution.
  • the amount of complexing agent is preferably comprised between 3 and 50 moles per atom gram of silver employed.
  • the buffer solutions which can be advantageously used are the ones which keep the value of pH between 9 and 12.5.
  • Example of said buffer solutions are: glycine sodium hydroxide, disodic phosphate sodium hydroxide and the like; very good results have been obtained with the mixture borax sodium hydroxide.
  • the electrolysis is advantageously carried out at a temperature comprised between 0 and C and preferably between 10 and 40C.
  • the potential can be kept between 500 and l ,500 mV measured with respect to the saturated calomel electrode.
  • the apparent current density can be com prised between 0.1 and 0.5 amp/cm and preferably between 0.2 and 0.3 amp/cm
  • the electrolytic cell anode can be constituted by graphite, platinum, platinumrhodium, titanium and in a general sense any good conductor which cannot be attacked by alkali material while the cathode can be constituted by silver, stainless steel, graphite and generally the same materials used as anode.
  • thesilver salt solution is kept under vigorous stirring.
  • the obtained silver, in form of a powder, after washing can be directly used, as it is or preferably supported on a ceramic material, as catalyst for the production of ethylene oxide.
  • FIG. 1 represents an electrolytic cell for the silver deposition according to the invention.
  • FIG. 2 shows the scheme of a unit for the production of silver on an industrial scale.
  • FIGS. 3 and 4 represent respectively a sectional view and a plan view of the industrial unit of FIG. 2.
  • FIG. 5 shows the current supply scheme of the cell according to FIGS. 3 and 4.
  • reference 1 indicates the circulating pump of the electrolyte
  • 2 is the anode, for instance of graphite
  • 3 is the cathode, for instance of silver net
  • 4 is the very cell, wherein the electrolysis takes place, whose bottom consists of the silver net
  • 5 is the electrolyte contained in the reservoir 11
  • 6 is a voltmeter to measure the direct tension supplied to the cell
  • 7 is a timer for the inversion of the cell
  • 8 is a direct current generator
  • 9 is an amperometer for measuring the direct current supplied to the cell
  • 10 is a timer for the pulsed electrodeposition.
  • the working of the cell is the following: the electrolyte, prepared aside, in a container not shown, kept into the reservoir 11 and drawn by pump 1, is introduced in the cell from the top thereof.
  • the electrolyte is periodically renewed when its silver content decreases under predeterminated values.
  • the cell is supplied with direct current by a generator 8 through a timer 10 which has the function of sending to the cell itself current impulses; periodically the sense of the current is inverted by the timer 7.
  • the electrodeposited silver detaching from electrode 3 falls directly in the reservoir 11 through the opening in the bottom of the cell.
  • the reference 101 represents a continuous centrifuge
  • 102 is the electrolytic cell provided with a stirrer 108 and a circulation pump 106
  • 103 and 104 are storing reservoirs of the silver salt solution which are equipped with a circulating pump 107 and from 105 the deposited silver is recovered.
  • electrolytic silver is deposited which, as a suspension, is fed by means of the pump 106 to the centrifuge 101 and discharged through the duct 105.
  • the pump 106 has also the function of recycling the electrolyte by a suitable series of valves, the electrolyte is fed to cell 102 from reservoirs 103 and 104 by means of the pump 107.
  • the reservoirs 103 and 104 work alternatively, i.e. one is used for preparing the electrolyte while the other, containing the electrolyte, feeds the cell.
  • stirring means are provided which have not been shown.
  • FIGS. 3 and 4 wherein 109 shows the anode, for instance perforated graphite, 110 is the cathode, for instance of silver net, 111 are through terminals for feeding the electrodes with direct current, 112 is the valve which allows the output toward the centrifuge 105, 113 is the recycling duct to the centrifuge, 114 is the recycling duct to the cell, 115 is the feeding duct of fresh solution.
  • the electric scheme for feeding the industrial cell is diagramatically represented in FIG. 5.
  • the 30 electrodes are fed in small independent groups of five pairs in series.
  • the feeding with direct current (which is supplied by impulses of 5 see.) is supplied by an amperostatic generator 123 which feeds, by means of the commutation units 121a to 121d, only one small groups, respectively 122a to 122f of five pairs of elements each and one after the other.
  • the feeding cycle starts again as programmed by the logical control unit 120, consisting of a square waves generator 116, a frequency divider 117, a counting unit in binary code 118 and a binary-decimal unit 119.
  • EXAMPLE 1 100 g of silver nitrate 750 g of borax (Na B O 10H O), 400 g of sodium hydroxide and 10 g of presolubilized carboxymethylcellulose, are dissolved in distilled water up a total volume of solution of 100 liters, 600 cc of Nl-I in a water solution are added to the above solution.
  • Said solution containing silver as an ammonia complex is utilized as an electrolyte in an electrolytic cell (shown in FIG. 1), using silver net as cathode (1 X 1 mm mesh) and tubular or perforated plate graphite as anode.
  • the electrical contacts are made with gold wire which in the operative conditions of the cell behaves as an inert metal.
  • the solution is circulated in the sense directed in FIG. 1 by means of an external circulating pump and the silver content is kept constant by subsequent additions of silver nitrate in an ammonia solution.
  • the continuous feeding current of the cell is delivered by impulses having a rectangular profile of a period of 10 sec.
  • the cell feeding circuit is arranged in such a way to give 10 sec. of delivering and 60 sec. of rest.
  • the cathodic deposition is carried out at constant current (amperostatic).
  • the main anodic process is the discharge of oxygen
  • the main cathodic process is the discharge of silver.
  • the operative conditions are the following:
  • the silver content is kept constant by adding every 2 hours 2.0 to 2.4g of ammonia complexed silver nitrate.
  • the total consumption of electric power is therefore comprised between 2.3 and 4.5 kwh per kg of produced silver.
  • the silver powder, obtained by the method according to the invention was partially recovered from the solution and partially from the surface of the electrode, filtered, washed with distilled water and then dried in an oven for 3 hours.
  • the productivity has been raised up to 20-24g of silver for 24 hours of continuous working, i.e., of about 2g each day for cm of apparent cathodic surface.
  • a test of catalytic activity has been carried out.
  • the silver has been deposited on a ceramic carrier and the so obtained catalyst containing 15 percent of Ag has been introduced in a tube of 2.4 cm of diameter equipped with an external jacket for the circulation of a thermostating liquid.
  • the height of the catalyst bed was about 1 meter.
  • the reactor has been fluxed at atmospheric pressure with a gaseous mixture having the following composition: ethylene 5%, CO 6.5%, 0 5%, N 83.5%.
  • the feeding flow was 2l0Nl/h and the contact time about 4.6 sec.
  • a good conversion of ethylene to ethylene oxide was obtained with a selectivity (an ethylene oxide moles per moles of reacted ethylene) of 80/, with a conversion of 25 percent.
  • EXAMPLE 2 In this example one of the possible industrial process is shown for the production of a silver based catalyst by pulsed electrochemical deposition, which uses silver nitrate as starting material and a particular electrolytic cell.
  • the total current for any single impulse was 700-900A.
  • the faradic efficiency of the discharge of Ag is 80 90 percent and the tension of the comprehensive feeding is comprised between 5 15 V.
  • the consumption of electric power is therefore comprised between 1.5 and 4.5 kwh per kg of produced silver.
  • the solution of example 2 Since the main anodic product is oxygen, the solution of example 2, shall more and more depleted of Ag and on the contrary shall concentrate of NH NO Therefore a feeding system is provided to introduce fresh solution continuously recycled and adjusted as to the Ag content with a highly concentrated silver nitrate ammonia solution (see diagram of FIG. 3). The solution is deemed no more useful when the ammonium nitrate concentration (in moles) became 100 times higher than the one of silver nitrate (in moles).
  • the amount of silver to be recovered is about 1 percent with respect to the amount of produced silver.
  • the higher productivity of this electrolytic cell, for the catalytically active silver is of 300kg/day for a continuous working of 24 hours (by using therefore an apparent electrodic solution of 10 mm' for a total yearly production of more than t/year of metallic silver.
  • Process according to claim 4 characterized in that the period of feeding the current in the reverse direction is between 1 and 60 seconds.
  • Process according to claim 7 characterized in that the amount of complexing agent is between 3 and 50 moles per gram atom of used silver.
  • Process according to claim 1 characterized in that the electrolysis is carried out at a temperature between 10 and 40C.
  • Process according to claim 1 characterized in that the potential of said current is between 500 and 1,500 mV with respect to the saturated calomel electrode.
  • amp/cm and preferably between 0.2 and 0.3 amp/cm?

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Electrochemistry (AREA)
  • Toxicology (AREA)
  • Plasma & Fusion (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Catalysts (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Electroplating Methods And Accessories (AREA)
US00275937A 1971-07-31 1972-07-28 Process for the electrochemical manufacture of silver containing catalysts Expired - Lifetime US3836436A (en)

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US (1) US3836436A (pt)
JP (1) JPS5639932B1 (pt)
AT (1) AT322514B (pt)
AU (1) AU470570B2 (pt)
BE (1) BE786623A (pt)
BR (1) BR7205136D0 (pt)
CA (1) CA1005388A (pt)
CH (1) CH545653A (pt)
CS (1) CS168601B2 (pt)
DD (1) DD98211A5 (pt)
DE (1) DE2237574C3 (pt)
DK (1) DK141277B (pt)
ES (1) ES405711A1 (pt)
FR (1) FR2148028B1 (pt)
GB (1) GB1393689A (pt)
LU (1) LU65795A1 (pt)
NL (1) NL161509C (pt)
NO (1) NO131776C (pt)
PL (1) PL82002B1 (pt)
RO (1) RO61157A (pt)
SE (1) SE371938B (pt)
SU (1) SU444351A3 (pt)
TR (1) TR18002A (pt)
YU (1) YU34574B (pt)
ZA (1) ZA725196B (pt)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5413987A (en) * 1994-01-24 1995-05-09 Midwest Research Institute Preparation of superconductor precursor powders
US5462647A (en) * 1994-09-09 1995-10-31 Midwest Research Institute Preparation of lead-zirconium-titanium film and powder by electrodeposition
US5785837A (en) * 1996-01-02 1998-07-28 Midwest Research Institute Preparation of transparent conductors ferroelectric memory materials and ferrites
US6603028B1 (en) 1998-08-07 2003-08-05 Bayer Aktiengesellschaft Method for oxidizing hydrocarbons
US20090134038A1 (en) * 2005-10-05 2009-05-28 Tadeusz Chudoba Method of Chemical Reactions Conduction and Chemical Reactor
DE102014204372A1 (de) 2014-03-11 2015-09-17 Bayer Materialscience Ag Verfahren zur Herstellung von katalytisch aktiven Pulvern aus metallischem Silber oder aus Mischungen aus von metallischem Silber mit Silberoxid zur Herstellung von Gasdiffusionselektroden

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2520219C3 (de) * 1975-05-07 1983-02-24 Basf Ag, 6700 Ludwigshafen Verfahren zur Herstellung von Formaldehyd
SE8504290L (sv) * 1985-09-16 1987-03-17 Boliden Ab Forfarande for selektiv utvinning av bly ur komplexa sulfidmalmer
EP0672765B1 (en) * 1994-03-14 1999-06-30 Studiengesellschaft Kohle mbH Electrochemical reduction of metal salts as a method of preparing highly dispersed metal colloids and substrate fixed metal clusters by electrochemical reduction of metal salts
WO1996028249A1 (de) * 1995-03-15 1996-09-19 Basf Aktiengesellschaft Verfahren zur herstellung von phosphordotierten silberkatalysatoren
DE19912896A1 (de) * 1999-03-23 2000-09-28 Daimler Chrysler Ag Verfahren zur Herstellung eines Katalysators

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU197980A1 (ru) * В. Аветис , В. П. Андронов Способ электролитического изготовления металлических порошков
US2216167A (en) * 1936-08-24 1940-10-01 Gen Metals Powder Company Method of producing metal powders
SU129447A1 (ru) * 1959-09-15 1959-11-30 В.И. Семерюк Способ электролитического получени порошка серебра из нерастворимых соединений
US3463711A (en) * 1964-04-24 1969-08-26 Agfa Ag Electrolytic method and apparatus for recovering silver from fixing baths

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU197980A1 (ru) * В. Аветис , В. П. Андронов Способ электролитического изготовления металлических порошков
US2216167A (en) * 1936-08-24 1940-10-01 Gen Metals Powder Company Method of producing metal powders
SU129447A1 (ru) * 1959-09-15 1959-11-30 В.И. Семерюк Способ электролитического получени порошка серебра из нерастворимых соединений
US3463711A (en) * 1964-04-24 1969-08-26 Agfa Ag Electrolytic method and apparatus for recovering silver from fixing baths

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5413987A (en) * 1994-01-24 1995-05-09 Midwest Research Institute Preparation of superconductor precursor powders
US5789348A (en) * 1994-01-24 1998-08-04 Midwest Research Institute Preparation of superconductor precursor powders
US5462647A (en) * 1994-09-09 1995-10-31 Midwest Research Institute Preparation of lead-zirconium-titanium film and powder by electrodeposition
US5785837A (en) * 1996-01-02 1998-07-28 Midwest Research Institute Preparation of transparent conductors ferroelectric memory materials and ferrites
US6603028B1 (en) 1998-08-07 2003-08-05 Bayer Aktiengesellschaft Method for oxidizing hydrocarbons
US20090134038A1 (en) * 2005-10-05 2009-05-28 Tadeusz Chudoba Method of Chemical Reactions Conduction and Chemical Reactor
DE102014204372A1 (de) 2014-03-11 2015-09-17 Bayer Materialscience Ag Verfahren zur Herstellung von katalytisch aktiven Pulvern aus metallischem Silber oder aus Mischungen aus von metallischem Silber mit Silberoxid zur Herstellung von Gasdiffusionselektroden

Also Published As

Publication number Publication date
FR2148028A1 (pt) 1973-03-11
NO131776C (pt) 1975-07-30
DD98211A5 (pt) 1973-06-12
DE2237574B2 (de) 1974-07-04
CH545653A (pt) 1974-02-15
DK141277B (da) 1980-02-18
DE2237574A1 (de) 1973-02-22
TR18002A (tr) 1976-08-20
ES405711A1 (es) 1975-09-01
NL161509C (nl) 1980-02-15
BE786623A (fr) 1973-01-24
LU65795A1 (pt) 1972-11-28
NO131776B (pt) 1975-04-21
PL82002B1 (pt) 1975-10-31
DK141277C (pt) 1980-08-11
CA1005388A (en) 1977-02-15
NL7210498A (pt) 1973-02-02
ZA725196B (en) 1973-04-25
AT322514B (de) 1975-05-26
DE2237574C3 (de) 1975-02-27
SE371938B (pt) 1974-12-09
YU191272A (en) 1979-04-30
FR2148028B1 (pt) 1976-01-16
CS168601B2 (pt) 1976-06-29
AU470570B2 (en) 1976-03-18
NL161509B (nl) 1979-09-17
SU444351A3 (ru) 1974-09-25
RO61157A (pt) 1977-01-15
GB1393689A (en) 1975-05-07
BR7205136D0 (pt) 1973-06-14
YU34574B (en) 1979-10-31
JPS5639932B1 (pt) 1981-09-17
AU4447272A (en) 1974-01-17

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