WO2011025808A1 - Production de dioxyde de chlore activée par uv en présence d'un courant électrique pour augmenter le rendement - Google Patents

Production de dioxyde de chlore activée par uv en présence d'un courant électrique pour augmenter le rendement Download PDF

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Publication number
WO2011025808A1
WO2011025808A1 PCT/US2010/046593 US2010046593W WO2011025808A1 WO 2011025808 A1 WO2011025808 A1 WO 2011025808A1 US 2010046593 W US2010046593 W US 2010046593W WO 2011025808 A1 WO2011025808 A1 WO 2011025808A1
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Prior art keywords
chlorine dioxide
chlorate
electric current
solution
chlorite
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PCT/US2010/046593
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English (en)
Inventor
Joseph Callerame
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Callerame, James
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Publication of WO2011025808A1 publication Critical patent/WO2011025808A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B11/00—Oxides or oxyacids of halogens; Salts thereof
    • C01B11/02—Oxides of chlorine
    • C01B11/022—Chlorine dioxide (ClO2)
    • C01B11/023—Preparation from chlorites or chlorates

Definitions

  • Chlorine dioxide (ClO 2 ) is of considerable industrial importance and has found use as a disinfectant and in the bleaching of wood pulp, fats, oils and flour. Generally, chlorine dioxide is used as a bleaching agent and for removing tastes and odors from water and other liquids. More recently, it has been used as an anti-pollutant.
  • chlorine dioxide For several of the established uses of chlorine dioxide, it is desirable to produce the gas in situ so that chlorine dioxide, upon formation, can be directly put to use either in gaseous form or, after absorption, in the form of an aqueous solution. In many instances, the use of a chlorine dioxide solution rather than in the gaseous form is preferred. Chlorine dioxide is absorbed in water and forms chlorous acid, from which the gas can be readily expelled by heating. The presence of chlorous acid in an aqueous solution indicates a reaction of chlorine dioxide with water.
  • Chlorous acid (HClO 2 ) is stable at low concentrations and is not generally stored long-term as a commercial product.
  • the corresponding sodium salt, sodium chlorite (NaClO 2 ) is stable and inexpensive enough to be commercially available.
  • the corresponding salts of heavy metals e.g., Ag + , Hg + , Pb 2+ , or Cu 2+
  • ammonium i.e., NH 4 +
  • Sodium chlorate (NaClO 3 ) is an oxidizing agent. When pure, it is a white crystalline powder that is hygroscopic and readily soluble in water. It decomposes above 250 °C to release oxygen and leave sodium chloride.
  • sodium chlorate is synthesized from the electrolysis of hot sodium chloride solution in a mixed electrode tank: NaCl + 3H 2 O ⁇ NaClO 3 + 3H 2 . It can also be synthesized by passing chlorine gas to a hot sodium hydroxide solution. It is then purified by crystallization.
  • Sodium chlorite is derived indirectly from sodium chlorate, NaClO 3 .
  • the explosively unstable gas chlorine dioxide (ClO 2 ) is produced by reducing sodium chlorate in a strong acid solution with a suitable reducing agent (e.g., sodium chloride, sulfur dioxide, or hydrochloric acid).
  • a suitable reducing agent e.g., sodium chloride, sulfur dioxide, or hydrochloric acid.
  • the chlorine dioxide gas is then absorbed into an alkaline solution and reduced with hydrogen peroxide (H 2 O 2 ), yielding sodium chlorite.
  • Chloric acid is a colorless substance that occurs only in solution. It is a strong acid and a strong oxidizing agent that decomposes if heated above 40 0 C. Under certain conditions it forms oxygen, water, and the explosive gas chlorine dioxide ClO 2 . Under other conditions, it forms perchloric acid and hydrochloric acid.
  • Perchloric acid HClO 4
  • HClO 4 is a volatile, unstable, colorless liquid.
  • HClO 4 is also a powerful oxidizing agent, especially when hot. It explodes when heated to about
  • HC1O 4 -2H 2 O is a stable liquid that boils at 200 0 C.
  • the present invention relates to methods of using chlorate or chlorite to produce chlorine dioxide gas by ultraviolet (UV) irradiation.
  • chlorine dioxide gas is produced by subjecting a chlorate solution or a chlorite solution to ultraviolet radiation in the presence of a catalyst and with an electric current.
  • Examples of a suitable chlorate include sodium chlorate, potassium chlorate, and calcium chlorate; and examples of a suitable chlorite include sodium chlorite, potassium chlorite, and calcium chlorite.
  • An example of the catalyst is carbon.
  • Other examples of a suitable catalyst include noble metals such as platinum, gold, silver, heavy metals, and others such as mercury and tungsten. Generally, any metal that facilitates or acts like an anode in the presence of UV (accepts the negativity of chlorate) and does not react with chlorine dioxide or the chlorite or chlorate is suitable.
  • the methods of this invention are carried out with an electric current, e.g., a direct current.
  • the electric current may be applied with two non-reacting electrodes, each of which, e.g., can be independently a carbon electrode or an iridium electrode, and can be, e.g., from each other by about 0.5 inch to about 5 inches (e.g., about 2 inches).
  • the electric current can range from about 0.1 to about 10 Amp, e.g., from about 0.1 to about 2.5 Amp, or at about 0.5 Amp.
  • the electric current can be applied with a voltage of from about 1 to about 24 Volts, e.g., from about 1 to about 12 Volts, or of about 6 Volts. Applying an electric current to the reaction for the production of ClO 2 gas was found to result in unexpectedly high yield of the ClO 2 gas, particularly with a chlorite or chlorate solution at a lower concentration.
  • Chloride ions can be introduced in many ways, e.g., by addition of a chloride salt (e.g., NaCl, NaCl 2 , KCl, or NH 4 Cl) or hydrochloride.
  • hydrogen ions can be introduced by addition of an acid such as HCl, CH 3 COOH, or H 2 CO 3 .
  • hydrogen ions can be introduced by bubbling with carbon dioxide (CO 2 ) into an aqueous solution to form carbonic acid which in turn ionizes to give rise to hydrogen ions.
  • CO 2 carbon dioxide
  • undesirable chlorine is not formed significantly by the reaction, which is a commercial and environmental advantage.
  • the yield of chlorine dioxide obtained by exposing the chlorate solution to ultraviolet radiation is a function of the exposure time, the intensity of the radiation and the concentration of chlorate and the presence of the catalyst in the solution. Since chlorine dioxide gas at higher concentrations has explosive properties, the above parameters are generally chosen such that the concentration of ClO 2 in the reaction mixture does not exceed about 10%. Alternatively, the generated chlorine dioxide gas can be continuously or periodically removed to maintain a desirable concentration in the reaction chamber.
  • Chlorine dioxide gas may be generated following general equations shown below as examples:
  • the chlorine dioxide generation process can be advantageously carried out in situ.
  • the chlorine dioxide formed need not be separated from the reaction mixture, but the entire reaction mixture, including the chlorine dioxide formed, may rather, in most instances, be used as a whole since the other components of the reaction may not exert any detrimental influence on the end uses.
  • a chlorine dioxide containing reaction mixture may be removed from the reaction space and transported to a place of use.
  • reaction parameters can be regulated with ease so that chlorine dioxide free of chlorine is formed.
  • the UV-lamp in the reaction chamber may be coated with Teflon ® or
  • PTFE polytetrafluoroethylene
  • any suitable non-corrosive layer to enhance the life and the efficiency of the lamp and to minimize undesirable salt deposits.
  • a method of producing chlorine dioxide includes the steps of introducing a solution of chlorate (e.g., NaClO 3 ) or chlorite (NaClO 2 ) into a reaction chamber and subjecting the chlorate to ultraviolet radiation in the presence of carbon catalyst.
  • the chlorate concentration is from about 0.1% w/v to about 50% w/v. Suitable chlorate concentrations also include about 0.1 to about 30% and 0.5% to about 20% w/v.
  • the chlorate solution or slurry is suitable for chlorine dioxide generation.
  • the chlorine dioxide generated may be less than about 10% w/v, or the generated gas can be continuously removed or stripped and the production of chlorine dioxide is performed in situ.
  • the ultraviolet radiation is provided by one or more ultraviolet generating lamps, optionally coated with an anticorrosive material.
  • the anticorrosive material is Teflon ® or any other suitable material.
  • the pH may be maintained in a range of about pH 3.5 to about pH 5.0.
  • the chlorine dioxide produced is removed from the reaction chamber and conveyed to a place of use or directly used along with a solution from the reaction chamber.
  • a cation ion-exchange resin may also be used as a reaction chamber for ClO 2 generation using chlorates.
  • One or more UV lamps can be positioned such that there exists a time interval between irradiations.
  • the one or more UV lamps can be turned off and on such that there exists a specific period during which there is no irradiation. This cycle of irradiation followed by a pause enhances the yield of chlorine dioxide.
  • This cyclical irradiation pattern is established by configuring one or more lamps serially or in parallel configuration, such that an incoming flow of precursor is exposed to the one or more lamps in a serial fashion with time intervals or by turning on and off the UV lamps in a periodic mode.
  • FIG. 1 is a diagrammatic rendering of apparatus for producing chlorine dioxide. DETAILED DESCRIPTION OF THE INVENTION
  • the reaction process may be carried out generally in an exemplary reactor shown in FIG. 1.
  • the reactor comprises a tubular vessel 1 having a valve-controlled bottom inlet 2 and a valve-controlled top exit 3.
  • the tubular vessel may be made of glass, titanium, a steel alloy, such as known under the name Hastalloy C or any suitable composite material.
  • An ultraviolet radiation source e.g., one or several quartz lamps 4, is arranged within the space 5 defined by the tubular vessel 1.
  • the quartz lamp is shown to have a distinct shape, it will be appreciated that other shapes, such as U-shaped quartz lamps, may also be used.
  • the electrical connections for the quartz lamp are diagrammatically indicated by reference numeral 6.
  • the UV source may be arranged outside the vessel.
  • the UV lamps may be coated with Teflon ® or generic PTFE or any suitable anti-corrosive layer to increase the life and efficiency of the lamp.
  • a shiny reflector such as of aluminum
  • the reflector may be arranged within the reaction space if it has a surface coating resistant to the reactants.
  • the reactor wall material may be of the UV transmitting kind if the UV source is arranged outside the reactor space, but may be nontransmitting if the light source is located within the reactor space.
  • the wall may thus be of glass, plastic, steel alloy or titanium, provided the material is resistant to the reactants.
  • a highly polished aluminum reflector should advantageously be used to contain the intensity of the radiation in the chamber space of the reactor if the material transmits UV radiation.
  • the reaction is improved for example 25% by adding a protonating catalyst for example, elemental carbon exposure to UV radiation at 200-280nm.
  • the kinetics of the reaction are also improved as the reaction rate increases with the amount of adsorptive surface of the elemental carbon that is included with the reactants as exposed surface (rod-granular). Carbon is not a reactant, but acts as a catalyst.
  • Suitable UV wavelength ranges include 180-300 nm, 220-260 nm, 240-250 nm, and of 254 nm. Protonation may not be required for the total duration of production process.
  • An initial protonating source may be useful in triggering the catalytic conversion of chlorate to chlorine dioxide.
  • organic acids and inorganic acids or any proton donor that ionize with the NaClO 3 are suitable.
  • extraction of ClO 2 from the reactants is accomplished with for example, air stream (positive pressure) or vacuum (negative pressure) or heat or extreme cooling of the reactants or any other standard procedure to remove gas from a reaction chamber.
  • the overall reaction of converting a precursor to ClO 2 is enhanced by irradiating the precursor (e.g., NaClO 3 or any suitable precursor to generate chlorine dioxide) serially, wherein a specific "pause" period is maintained during which no irradiation is performed.
  • a specific "pause" period is maintained during which no irradiation is performed.
  • This series of irradiation followed by a period of no irradiation e.g., 1/20 to 1/5 of the time for irradiation
  • the serial irradiation or pulsing is
  • the time interval between the irradiation may vary depending on the strength of UV lamps and the duration of the irradiation, the dimensions of the container and the percent yield desired. For example, the pause period may extend from a few seconds to a few minutes.
  • the pause period may be a fraction of the time required for the irradiation.
  • the pause period may vary from 1/30 or 1/20 to 1/5 of the time required for the irradiation phase.
  • the frequency of the pulses may also vary. The pulsing mode need not be carried out from beginning to end and may be performed towards the later stages of the production.
  • the inventive methods described herein involve the surprising effects achieved by exposing the reactants to a polarized radiation at wavelength from about 200 to about 400 nm, e.g., from about 240 to about 360 nm.
  • the wavelength can be varied about these parameters, however, without limiting the scope of the invention, in one embodiment, increased ClO 2 production is achieved when the polarized UV radiation is held constant at about 254 nm.
  • the polarized radiation such as, for example, polarized UV light may be about 75% polarized or about 80% polarized or about 95% polarized or about 100% polarized. Lower or higher percent polarized light can be used depending on the yield of chlorine dioxide produced.
  • the angle of polarized light may also vary relative to unpolarized light source.
  • the intensity of the radiation can vary from about 1,000 microwatts/cm 2 (or "mwatts/cm 2 ") to about 60,000 microwatts/cm 2 .
  • the methods of this invention can be carried out in situ or ex situ. Furthermore, the chlorine dioxide formed need not be separated from the reaction mixture; however, the entire reaction mixture, including the chlorine dioxide formed, may in most instances, be used as a whole since the other components of the reaction do not exert a detrimental influence on the application properties. Thus, the chlorine dioxide containing reaction product obtained as a result of the polarized radiation may be expelled from the reaction space and conveyed to a place of use, or, if desired, after completion of the reaction, the reaction mixture may be passed through water to form dissolved chlorine dioxide or chlorous acid.
  • One or more UV lamps can be positioned such that there exists a time interval between irradiations.
  • the one or more UV lamps can be turned off and on such that there exists a specific period during which there is no irradiation. This cycle of irradiation followed by a pause, enhances the yield of chlorine dioxide.
  • This cyclical irradiation pattern is established by configuring one or more lamps serially or in parallel configuration, such that an incoming flow of precursor is exposed to the one or more lamps in a serial fashion with time intervals or by turning on and off the UV lamps in a periodic mode.
  • Chlorine dioxide (ClO 2 ) production is enhanced by the use of an electromagnetic field (EMF) or electromotive force.
  • EMF electromagnetic field
  • the electromagnetic field is present during ultraviolet (UV) radiation-based production of chlorine dioxide.
  • UV ultraviolet
  • the EMF is believed to favor the reaction that results in the formation of chlorine dioxide from the starting materials, e.g. chlorine and oxygen.
  • a polarizing screen may be a linear reflecting polarizer screen, e.g., a 90° linear polarizer that functions like a conventional absorption polarizer, except that it reflects (instead of absorbs) substantially all light that does not pass though it.
  • the 90° reflecting polarizer screen transmits substantially all light waves polarized to 90° (i.e., "vertically” polarized light) and reflects substantially all light waves polarized to 0° (i.e., "horizontally” polarized light).
  • Polarizer may be made of any suitable reflecting polarizing material, such as double brightness
  • DBEF DBEF enhancement film
  • a suitable polarizer also includes a high transmittance-high efficiency linear polarizer that has about 38% transmittance for unpolarized light.
  • Commercial-quality film polarizers available in medium gray (25% transmission) and medium brown (22% transmission). Polarization efficiency is over 90%, preferably over 95%, and more preferably over 99%.
  • Extinction is described generally as a polarizing filter's ability to absorb polarized light that has an orientation 90° to the polarizer's axis of polarization.
  • reaction geometry of selected species can be controlled by using polarized light. It is possible that one of the reactants is generated in a photo-dissociation process. Another molecular reactant may be excited in a specific rovibrational state. For example, an attacking oxygen or a chlorine atom is generated in the
  • photo-dissociation/photolysis in the UV wavelength range e.g., about 100-400 nm, or about 200-300 nm, or about 250-280 nm; or about 280-355 nm.
  • chlorine atom is formed in the photolysis of Cl 2 at 355 nm.
  • Polarized UV excitation provides optimal reaction geometry for the formation of ClO 2 molecule from its reacting constituents.
  • Atomizing results in an increased production of chlorine dioxide.
  • Atomizing or spraying or vaporizing can be performed by any suitable equipment such as an atomizer, a container equipped with a spray head and the like.
  • NaClO 3 solutions are exposed to radiation from an ultraviolet light source of about 4000 mwatts/cm 2 at one inch and peak wavelength of 254 nm in the presence of carbon as a catalyst.
  • Chlorine dioxide is formed as determinable by spectrographic absorbance.
  • a 1% NaClO 3 solution was exposed to radiation from an ultraviolet light source of about 4000 mwatts/cm at 284 nm in the presence of carbon as a catalyst with an electric current of about 0.5 Amp at 6 Volts, for about 15 minutes.
  • the reaction solution was purged with a steam of air and the electric current was applied with two electrodes 2 carbon inches apart from each other.
  • the yield of chlorine dioxide was about 70% as determinable by spectrographic absorbance.
  • a control reaction in which no electric current was applied gave a yield of only 30%.
  • Example 2 Same experiments as Example 2 were conducted except that 0.25%, 0.5%, 2%, and 5% solutions were used. The results were similar - the 0.25% and 0.5% solutions had yields greater than 80%, while the 2% and 5% solutions gave rise to about 70%.
  • EXAMPLE 4 Production of chlorine dioxide in a reactor chamber.
  • This experiment can be carried out in the reactor or apparatus shown in FIG. 1.
  • Space 5 of the reactor vessel 1 is flushed with oxygen, introduced through inlet 2 to replace the air atmosphere in the reactor.
  • a 1% w/v solution of sodium chlorate in water is thereafter introduced into the chamber space through inlet 2 and the quartz lamp is switched on to expose the solution to ultraviolet radiation.
  • the radiation emitted by the lamp has a constant intensity of 4,000 mwatts/cm 2 at 254 nanometers at 1 inch.
  • the reference to "1 inch” indicates the distance from the center of illumination where the rated intensity is measured.
  • the solution is subjected to radiation in the presence of a carbon catalyst. Chlorine dioxide is detected in the solution after 10 seconds of exposure to the radiation by absorbance peak and titration.
  • Constant wavelength of 254 nanometers is maintained during the experiments without ozone producing interfering wavelengths.
  • several lamps may be used as a UV radiation source. In one series of experiments, two lamps were used, each being rated at 20,000 mwatts/cm 2 at 1 inch. However, it is possible to use lamps rated at 4,000 mwatts/cm 2 or less, in which event, up to 10 or even more lamps may be used.
  • the lamps may also be coated with Teflon ® or any suitable anti-corrosive layer.
  • Removal of ClO 2 gas from solution as a pure gas can be accomplished by a stream of air (positive or negative), and the removed chlorine dioxide gas can be readily used to or temporarily stored in cold water for later use. Removal of ClO 2 gas can also be performed by applying continuous or periodic vacuum in the reaction chamber.
  • Mercury vapor lamp (500Ov; 40 milliamp current) can also be used and maintained at 32 0 C or any suitable ambient temperature and pressure. All wetted parts are protected by inert materials to ClO 2 and UV radiation, and the reaction surface is reactive to volume of flow or contaminant.
  • Exposure to irradiation time is directly proportional to concentration of [ClO 2 ] + [H + ] or [ClO 3 ] + [H + ] and wattage of radiation.
  • potassium chlorate is suitable for chlorine dioxide generation.

Abstract

Un chlorate comprenant un chlorate de sodium est utilisé selon l'invention pour produire du gaz dioxyde de chlore après exposition à un rayonnement ultraviolet en présence d'un catalyseur convenable et d'un courant électrique. Le gaz dioxyde de chlore peut être utilisé pour désinfecter, blanchir et pour une grande variété de fins industrielles et commerciales. Une lampe à UV à revêtement Téflon® est éventuellement utilisée pour irradier une solution de chlorate.
PCT/US2010/046593 2009-08-25 2010-08-25 Production de dioxyde de chlore activée par uv en présence d'un courant électrique pour augmenter le rendement WO2011025808A1 (fr)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4874489A (en) * 1988-07-11 1989-10-17 Joseph Callerame Process for the production of chlorine dioxide
US6265343B1 (en) * 1994-03-07 2001-07-24 Degussa Corporation Catalyst and method for the synthesis of chlorine dioxide, and method of making catalyst for the synthesis of chlorine dioxide
US20050034997A1 (en) * 2003-08-12 2005-02-17 Halox Technologies, Inc. Electrolytic process for generating chlorine dioxide
US20050079124A1 (en) * 2003-08-06 2005-04-14 Sanderson William D. Apparatus and method for producing chlorine dioxide
US20050079122A1 (en) * 2003-10-10 2005-04-14 Dimascio Felice Systems and methods for generating chlorine dioxide
US20060171875A1 (en) * 2001-08-02 2006-08-03 Sampson Allison H Methods for making chlorine dioxide
US20060280673A1 (en) * 2005-06-10 2006-12-14 Dimascio Felice Processes for producing an aqueous solution containing chlorine dioxide

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4874489A (en) * 1988-07-11 1989-10-17 Joseph Callerame Process for the production of chlorine dioxide
US6265343B1 (en) * 1994-03-07 2001-07-24 Degussa Corporation Catalyst and method for the synthesis of chlorine dioxide, and method of making catalyst for the synthesis of chlorine dioxide
US20060171875A1 (en) * 2001-08-02 2006-08-03 Sampson Allison H Methods for making chlorine dioxide
US20050079124A1 (en) * 2003-08-06 2005-04-14 Sanderson William D. Apparatus and method for producing chlorine dioxide
US20050034997A1 (en) * 2003-08-12 2005-02-17 Halox Technologies, Inc. Electrolytic process for generating chlorine dioxide
US20050079122A1 (en) * 2003-10-10 2005-04-14 Dimascio Felice Systems and methods for generating chlorine dioxide
US20060280673A1 (en) * 2005-06-10 2006-12-14 Dimascio Felice Processes for producing an aqueous solution containing chlorine dioxide

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