CA2307818C - Method of chlorine dioxide production - Google Patents
Method of chlorine dioxide production Download PDFInfo
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- CA2307818C CA2307818C CA 2307818 CA2307818A CA2307818C CA 2307818 C CA2307818 C CA 2307818C CA 2307818 CA2307818 CA 2307818 CA 2307818 A CA2307818 A CA 2307818A CA 2307818 C CA2307818 C CA 2307818C
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- Prior art keywords
- hydrogen peroxide
- chlorate
- chlorine dioxide
- sodium chlorate
- solution
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 title claims abstract description 52
- 239000004155 Chlorine dioxide Substances 0.000 title claims abstract description 26
- 235000019398 chlorine dioxide Nutrition 0.000 title claims abstract description 26
- 238000000034 method Methods 0.000 title claims description 31
- 238000004519 manufacturing process Methods 0.000 title description 7
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 80
- XTEGARKTQYYJKE-UHFFFAOYSA-M Chlorate Chemical compound [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 claims abstract description 53
- BZSXEZOLBIJVQK-UHFFFAOYSA-N 2-methylsulfonylbenzoic acid Chemical compound CS(=O)(=O)C1=CC=CC=C1C(O)=O BZSXEZOLBIJVQK-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000007864 aqueous solution Substances 0.000 claims abstract description 8
- 239000012429 reaction media Substances 0.000 claims description 4
- 239000011260 aqueous acid Substances 0.000 claims description 2
- 229940005989 chlorate ion Drugs 0.000 claims description 2
- XLYOFNOQVPJJNP-ZSJDYOACSA-N heavy water Substances [2H]O[2H] XLYOFNOQVPJJNP-ZSJDYOACSA-N 0.000 claims description 2
- 239000000243 solution Substances 0.000 abstract description 25
- -1 sodium chlorate Chemical compound 0.000 abstract description 8
- 238000006243 chemical reaction Methods 0.000 description 14
- 239000000203 mixture Substances 0.000 description 9
- 239000000126 substance Substances 0.000 description 7
- 229910052783 alkali metal Inorganic materials 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 5
- 235000011149 sulphuric acid Nutrition 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- XTEGARKTQYYJKE-UHFFFAOYSA-N chloric acid Chemical class OCl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-N 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 150000002978 peroxides Chemical class 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- RPAJSBKBKSSMLJ-DFWYDOINSA-N (2s)-2-aminopentanedioic acid;hydrochloride Chemical class Cl.OC(=O)[C@@H](N)CCC(O)=O RPAJSBKBKSSMLJ-DFWYDOINSA-N 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 238000004076 pulp bleaching Methods 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000009738 saturating Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- YZHUMGUJCQRKBT-UHFFFAOYSA-M sodium chlorate Chemical class [Na+].[O-]Cl(=O)=O YZHUMGUJCQRKBT-UHFFFAOYSA-M 0.000 description 1
- DHCDFWKWKRSZHF-UHFFFAOYSA-L thiosulfate(2-) Chemical compound [O-]S([S-])(=O)=O DHCDFWKWKRSZHF-UHFFFAOYSA-L 0.000 description 1
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- Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
An aqueous solution of hydrogen peroxide and a chlorate, particularly sodium chlorate, useful in the generation of chlorine dioxide, is provided which is more concentrated in at least chlorate than is achievable by mixing together separate aqueous solutions of commercially-available hydrogen peroxide and chlorate at the same weight ratio of hydrogen peroxide to chlorate. Such solutions enable chlorine dioxide to be generated with greater efficiency.
Description
TITLE OF INVENTION
METHOD OF CHLORINE DIOXIDE PRODUCTION
FIELD OF THE INVENTION
The present invention relates to the production of chlorine dioxide, particularly by an improved method involving the reaction between chlorate ions and hydrogen peroxide, carried out in a strongly acidic reaction medium.
BACKGROUND TO THE INVENTION
The reaction for the production of chlorine dioxide by reaction of chlorate ion with hydrogen peroxide can be depicted by the following equation:
2003- + H2O2 + 2H+ --> 2002 + O2 + 2H2O (1) Atmospheric type processes based on the above mentioned reaction were described thoroughly in the prior art. For example, U.S. Patent 2,332,181 (Soule) describes a highly efficient chlorine dioxide generation process based on reaction (1), carried out either batchwise or continuously, both in the absence and in the presence of chloride ions.
U.S. Patent 2,833,624 (Sprauer) discloses a process similar to that described in USP 2,332,181 but performed at elevated temperatures of above 70 C. According to Sprauer, the presence of chloride ions in the reaction medium may have a beneficial catalytic effect on the kinetics of reaction (1).
Sprauer suggests the use of a tubular reactor and shows that, under optimum conditions, 90% or better conversion of chlorate to chlorine dioxide is possible.
Sprauer further suggests the possibility of premixing the feedstocks, particularly chlorate, chloride and hydrogen peroxide. Both the specification and examples of Sprauer indicate that the premixing involves the use of solutions of separate feedstocks.
METHOD OF CHLORINE DIOXIDE PRODUCTION
FIELD OF THE INVENTION
The present invention relates to the production of chlorine dioxide, particularly by an improved method involving the reaction between chlorate ions and hydrogen peroxide, carried out in a strongly acidic reaction medium.
BACKGROUND TO THE INVENTION
The reaction for the production of chlorine dioxide by reaction of chlorate ion with hydrogen peroxide can be depicted by the following equation:
2003- + H2O2 + 2H+ --> 2002 + O2 + 2H2O (1) Atmospheric type processes based on the above mentioned reaction were described thoroughly in the prior art. For example, U.S. Patent 2,332,181 (Soule) describes a highly efficient chlorine dioxide generation process based on reaction (1), carried out either batchwise or continuously, both in the absence and in the presence of chloride ions.
U.S. Patent 2,833,624 (Sprauer) discloses a process similar to that described in USP 2,332,181 but performed at elevated temperatures of above 70 C. According to Sprauer, the presence of chloride ions in the reaction medium may have a beneficial catalytic effect on the kinetics of reaction (1).
Sprauer suggests the use of a tubular reactor and shows that, under optimum conditions, 90% or better conversion of chlorate to chlorine dioxide is possible.
Sprauer further suggests the possibility of premixing the feedstocks, particularly chlorate, chloride and hydrogen peroxide. Both the specification and examples of Sprauer indicate that the premixing involves the use of solutions of separate feedstocks.
In recently published European Patent Application EP 866,031 (Tenney) it was shown that the tubular reactor of the type described in Sprauer can be used to achieve chlorate conversion to chlorine dioxide of above 75% which is below the at least 90% value disclosed in Sprauer.
One of the deficiencies of all the above described processes is related to the limited range of concentrations of chemicals (chlorate and hydrogen peroxide) achievable in the reaction mixture prepared by mixing of the corresponding feedstocks in a ratio matching the requirements of the chlorine dioxide generator.
Such a limitation on chemicals concentrations affects, in a negative way, both the kinetics of reaction (1) and the process yield resulting therefrom.
There is a need, therefore, to develop a highly efficient chlorine dioxide generation process based on reaction (1) which is not affected by the kinetic limitations characteristic for the prior art processes.
SUMMARY OF INVENTION
It was surprisingly found that by using a concentrated, mixed feed of chlorate and hydrogen peroxide, in a form more concentrated with respect to at least chlorate than is achievable by combining saturated chlorate solution with commercially-available hydrogen peroxide solution, the kinetic limitations characteristic of the prior art processes can be overcome, resulting in a chlorine dioxide generation process having a significantly improved performance.
Accordingly, in one aspect of the present invention, there is provided an aqueous solution of hydrogen peroxide and chlorate for use as a feed to a chlorine dioxide generating process which is more concentrated in at least chlorate than a solution prepared by mixing saturated chlorate solution and commercially-available hydrogen peroxide solutions.
Commercially-available hydrogen peroxide solutions contain typically up to 70 wt% H2O2. Routine manufacture of more concentrated hydrogen peroxide solutions, such as about 90 wt% solution, has been discontinued sometime ago.
Nevertheless, the present invention constitutes an improvement even with respect to the latter solution.
The aforementioned concentrated, mixed feed can be prepared, for example, by dissolving crystalline alkali metal chlorate, preferably sodium chlorate, in a hydrogen peroxide solution of any desired concentration, generally from about 5 wt% to about 70 wt%, preferably about 10 wt% to about 50 wt%, and most preferably from about 10 wt% to about 30 wt%. The chlorate is added preferably to substantially saturate the aqueous hydrogen peroxide solution.
The present invention extends to a method of forming chlorine dioxide by reacting chlorate with hydrogen peroxide in an aqueous acid reaction medium according to the equation:
2C1O3- + H202 + 2H+ -+ 2C1O2 + 02 + 2H20 wherein a feed to the reaction is the aqueous solution of hydrogen peroxide and chlorate provided herein.
BRIEF DESCRIPTION OF DRAWING
Figure 1 is a graphical representation of the relationship of maximum sodium chlorate concentration in chlorate/hydrogen peroxide mixtures prepared by mixing saturated sodium chlorate solution with commercially-available hydrogen peroxide solution (50 wt% chain line; 70 wt% solid line) at different weight ratios.
GENERAL DESCRIPTION OF THE INVENTION
It is usually desirable to prepare a concentrated, mixed feed in which the ratio of hydrogen peroxide to chlorate matches the requirements of the overall chlorine dioxide generating process. These requirements are usually determined by many factors, such as generator design, desired production rate, flow characteristics, residence time, reaction kinetics and efficiency.
Upon selecting a specific H202 concentration within the aforementioned most desirable range of about 10 wt% to about 30 wt%, such as for example an about 18 wt% solution of H202, it is preferred to nearly saturate the about 18 wt%
H2O2 solution with sodium chlorate, resulting in a concentrated, mixed feed containing approximately 620 g/L NaC1O3 and 155 g/L H2O2, corresponding to a weight ratio of H202 to NaC1O3 of 0.25 g H202/g NaC1O3. Such a high concentration of NaC1O3 in a NaC1O3/H2O2 mixture cannot be achieved by the prior art method of mixing of separate solutions, even if a 90 wt% of H2O2 is used (in the latter case, the NaC1O3 concentration in the resulting mixture would have been below 550 g/L).
One of the deficiencies of all the above described processes is related to the limited range of concentrations of chemicals (chlorate and hydrogen peroxide) achievable in the reaction mixture prepared by mixing of the corresponding feedstocks in a ratio matching the requirements of the chlorine dioxide generator.
Such a limitation on chemicals concentrations affects, in a negative way, both the kinetics of reaction (1) and the process yield resulting therefrom.
There is a need, therefore, to develop a highly efficient chlorine dioxide generation process based on reaction (1) which is not affected by the kinetic limitations characteristic for the prior art processes.
SUMMARY OF INVENTION
It was surprisingly found that by using a concentrated, mixed feed of chlorate and hydrogen peroxide, in a form more concentrated with respect to at least chlorate than is achievable by combining saturated chlorate solution with commercially-available hydrogen peroxide solution, the kinetic limitations characteristic of the prior art processes can be overcome, resulting in a chlorine dioxide generation process having a significantly improved performance.
Accordingly, in one aspect of the present invention, there is provided an aqueous solution of hydrogen peroxide and chlorate for use as a feed to a chlorine dioxide generating process which is more concentrated in at least chlorate than a solution prepared by mixing saturated chlorate solution and commercially-available hydrogen peroxide solutions.
Commercially-available hydrogen peroxide solutions contain typically up to 70 wt% H2O2. Routine manufacture of more concentrated hydrogen peroxide solutions, such as about 90 wt% solution, has been discontinued sometime ago.
Nevertheless, the present invention constitutes an improvement even with respect to the latter solution.
The aforementioned concentrated, mixed feed can be prepared, for example, by dissolving crystalline alkali metal chlorate, preferably sodium chlorate, in a hydrogen peroxide solution of any desired concentration, generally from about 5 wt% to about 70 wt%, preferably about 10 wt% to about 50 wt%, and most preferably from about 10 wt% to about 30 wt%. The chlorate is added preferably to substantially saturate the aqueous hydrogen peroxide solution.
The present invention extends to a method of forming chlorine dioxide by reacting chlorate with hydrogen peroxide in an aqueous acid reaction medium according to the equation:
2C1O3- + H202 + 2H+ -+ 2C1O2 + 02 + 2H20 wherein a feed to the reaction is the aqueous solution of hydrogen peroxide and chlorate provided herein.
BRIEF DESCRIPTION OF DRAWING
Figure 1 is a graphical representation of the relationship of maximum sodium chlorate concentration in chlorate/hydrogen peroxide mixtures prepared by mixing saturated sodium chlorate solution with commercially-available hydrogen peroxide solution (50 wt% chain line; 70 wt% solid line) at different weight ratios.
GENERAL DESCRIPTION OF THE INVENTION
It is usually desirable to prepare a concentrated, mixed feed in which the ratio of hydrogen peroxide to chlorate matches the requirements of the overall chlorine dioxide generating process. These requirements are usually determined by many factors, such as generator design, desired production rate, flow characteristics, residence time, reaction kinetics and efficiency.
Upon selecting a specific H202 concentration within the aforementioned most desirable range of about 10 wt% to about 30 wt%, such as for example an about 18 wt% solution of H202, it is preferred to nearly saturate the about 18 wt%
H2O2 solution with sodium chlorate, resulting in a concentrated, mixed feed containing approximately 620 g/L NaC1O3 and 155 g/L H2O2, corresponding to a weight ratio of H202 to NaC1O3 of 0.25 g H202/g NaC1O3. Such a high concentration of NaC1O3 in a NaC1O3/H2O2 mixture cannot be achieved by the prior art method of mixing of separate solutions, even if a 90 wt% of H2O2 is used (in the latter case, the NaC1O3 concentration in the resulting mixture would have been below 550 g/L).
The weight ratio of H202 to NaC1O3 in mixtures useful for chlorine dioxide generation can vary in a wide range of between about 0.16 to about 0.30 g H202/g NaC1O3. The concentrations of the starting solutions of hydrogen peroxide used for the preparation of a feed mixture with a given H2O2/NaC1O3 weight ratio vary accordingly. For example, in order to prepare a mixture having a weight ratio of H202 to NaC1O3 of about 0.17, the concentration of H202 in the starting solution should be about 15 wt%. Upon saturation of such solution with NaC1O3, a mixture containing approximately 11Og/L H202 and 635 g/L NaC1O3 is formed.
Alternatively to the use of crystalline alkali metal chlorate for the dissolution in the hydrogen peroxide solutions, it is possible to employ a slurry of alkali metal chlorate or even a concentrated alkali metal chlorate solution. A
resulting mixture is then concentrated, for example, by evaporation of water therefrom, preferably at a reduced pressure, in order to lower the temperature of the evaporation step.
Regardless of the mode of preparation of the concentrated, mixed feed, the concentration of at least chlorate contained therein exceed that achievable by the prior art methods, i.e. by mixing of the solutions of corresponding feedstocks, without the subsequent concentrating step. The maximum NaC1O3 concentration levels in the NaC1O3/H2O2 mixtures achievable according to the prior art processes are graphically depicted in Figure 1.
The concentrated, mixed feed of alkali metal chlorate and hydrogen peroxide can be used to generate chlorine dioxide in any type of a generator.
For example, a tubular generator of the type described in USP 2,833,624 (Sprauer) and substantially reproduced in EP 866,031 (Tenney) can be employed.
Generators of other shapes and forms, for example, a conical or dual-conical shape can be employed, if desired. A suitable generator can operate in a single pass mode or with the recirculation of chemicals. In the latter case, it is preferred to separate the desired product, chlorine dioxide, from the unreacted chemicals, i.e. chlorate, acid and hydrogen peroxide, before return to the reactor.
In addition to being used in the aforementioned type generators, typically employed in the smaller scale, water treatment applications, the concentrated, mixed feed can be utilized for the generation of chlorine dioxide in large scale applications, such as pulp bleaching. Conventional generators, both atmospheric and subatmospheric, operated in both crystallizing and non-crystallizing modes of operation can be utilized. A conventional atmospheric type generator utilizing the 5 chemistry of reaction (1) is described, for example, in US Patent 5,380,517 (Sokol). The latter generator utilizes a design identical to that known for the Solvay or Mathieson reactor.
A subatmospheric, single vessel process (SVP) utilizing the chemistry of reaction (1) is described, for example, in US Patents 5,091,166 and 5,091,167 (Engstrom et al).
It is noted that the use of a premixed feed of chlorate and hydrogen peroxide, whether concentrated or not, has some additional benefits related to the simplification of the equipment required (less pumps required) and the avoidance of problems related to the inadequate and potentially unsafe control of separate feeds.
EXAMPLE
In order to illustrate the beneficial effect related to the use of concentrated, mixed feed of chlorate and hydrogen peroxide, two experimental runs were conducted. An experimental run (run 2) carried out according to the preferred embodiment of the invention involved the use of a concentrated, mixed feed containing approximately 620 g/L NaC1O3 and 155 g/L H202 prepared by saturating an about 18 wt% H202 solution with sodium chlorate, by dissolving NaC1O3 crystals in the H202 solution.
A comparative example (run 1) involved the use of a mixed feed containing approximately 480 g/L sodium chlorate and 120 g/L hydrogen peroxide prepared conventionally by mixing the required amounts of a 50 wt%
H202 solution and a saturated NaC1O3 solution containing 610 g NaC1O3/L.
Both runs were conducted under similar conditions in terms of acid and peroxide weight feed ratios (H2SO4/NaC1O3 and H2O2/NaC1O3) and operating pressure. Both runs were conducted in the same, conical reactor of 0.81 L
capacity.
Alternatively to the use of crystalline alkali metal chlorate for the dissolution in the hydrogen peroxide solutions, it is possible to employ a slurry of alkali metal chlorate or even a concentrated alkali metal chlorate solution. A
resulting mixture is then concentrated, for example, by evaporation of water therefrom, preferably at a reduced pressure, in order to lower the temperature of the evaporation step.
Regardless of the mode of preparation of the concentrated, mixed feed, the concentration of at least chlorate contained therein exceed that achievable by the prior art methods, i.e. by mixing of the solutions of corresponding feedstocks, without the subsequent concentrating step. The maximum NaC1O3 concentration levels in the NaC1O3/H2O2 mixtures achievable according to the prior art processes are graphically depicted in Figure 1.
The concentrated, mixed feed of alkali metal chlorate and hydrogen peroxide can be used to generate chlorine dioxide in any type of a generator.
For example, a tubular generator of the type described in USP 2,833,624 (Sprauer) and substantially reproduced in EP 866,031 (Tenney) can be employed.
Generators of other shapes and forms, for example, a conical or dual-conical shape can be employed, if desired. A suitable generator can operate in a single pass mode or with the recirculation of chemicals. In the latter case, it is preferred to separate the desired product, chlorine dioxide, from the unreacted chemicals, i.e. chlorate, acid and hydrogen peroxide, before return to the reactor.
In addition to being used in the aforementioned type generators, typically employed in the smaller scale, water treatment applications, the concentrated, mixed feed can be utilized for the generation of chlorine dioxide in large scale applications, such as pulp bleaching. Conventional generators, both atmospheric and subatmospheric, operated in both crystallizing and non-crystallizing modes of operation can be utilized. A conventional atmospheric type generator utilizing the 5 chemistry of reaction (1) is described, for example, in US Patent 5,380,517 (Sokol). The latter generator utilizes a design identical to that known for the Solvay or Mathieson reactor.
A subatmospheric, single vessel process (SVP) utilizing the chemistry of reaction (1) is described, for example, in US Patents 5,091,166 and 5,091,167 (Engstrom et al).
It is noted that the use of a premixed feed of chlorate and hydrogen peroxide, whether concentrated or not, has some additional benefits related to the simplification of the equipment required (less pumps required) and the avoidance of problems related to the inadequate and potentially unsafe control of separate feeds.
EXAMPLE
In order to illustrate the beneficial effect related to the use of concentrated, mixed feed of chlorate and hydrogen peroxide, two experimental runs were conducted. An experimental run (run 2) carried out according to the preferred embodiment of the invention involved the use of a concentrated, mixed feed containing approximately 620 g/L NaC1O3 and 155 g/L H202 prepared by saturating an about 18 wt% H202 solution with sodium chlorate, by dissolving NaC1O3 crystals in the H202 solution.
A comparative example (run 1) involved the use of a mixed feed containing approximately 480 g/L sodium chlorate and 120 g/L hydrogen peroxide prepared conventionally by mixing the required amounts of a 50 wt%
H202 solution and a saturated NaC1O3 solution containing 610 g NaC1O3/L.
Both runs were conducted under similar conditions in terms of acid and peroxide weight feed ratios (H2SO4/NaC1O3 and H2O2/NaC1O3) and operating pressure. Both runs were conducted in the same, conical reactor of 0.81 L
capacity.
After the feed rates were set, the necessary time to reach steady temperature was allowed before samples were taken. Steady state samples were collected every 20 to 25 minutes for a total of 70 to 90 minutes before considering each run completed.
Chlorine and chlorine dioxide analysis were done by the Neutral/Acid (KI/Thiosulphate) test performed on KI solution used to trap C1O2/C12 stripped out immediately after taking the process discharge sample.
The process conditions maintained during the runs were:
Run 1 Run 2 a) Pressure (mmHg) 480 480 b) (H2O2/NaClO3)Feed(g/g) 0.247 0.248 c) (H2SO4/NaC1O3)Feed(g/g) 2.489 2.222 d) [H2SO4]Feed(N) 27.3 27.3 e) [NaClO3]Feed(g/L) 480.5 618.4 f) Discharge Flow Rate (L/min) 41.86 42.13 g) Chlorate/Peroxide Feed Rate (L/min) 0.149 0.108 h) Acid Feed Flow Rate (L/min) 0.134 0.111 Results Run 1 Run 2 C102 Yield from NaClO3(%) 92.4 98.5 Chemical Efficiency(%) 99.0 99.5 H202 Consumption(g/g C102) 0.421 0.398 H2SO4 Consumption(g/g Cl02) 4.25 3.560 NaC1O3 Consumption(g/g C102) 1.708 1.602 Discharges i) [C102](g/L) 1.004 0.987 J) [C12](mg/L) 5.6 3.3 k) [NaC103](mg/L) 28.4 6.8 1) [H2SO4](g/L) 4.27 3.62 m) [C104](mg/L) 1.1 0.1 The above comparison clearly shows the superior performance of the process of the invention (run 2) in terms of yield, efficiency, chemical consumption for all feedstocks, product purity and the reduced losses of chemicals in the discharges (effluents).
SUMMARY OF DISCLOSURE
In summary of this disclosure, an improved process for the production of chlorine dioxide uses a concentrated, mixed feed of alkali metal chlorate and hydrogen peroxide. Modifications are possible within the scope of this invention.
Chlorine and chlorine dioxide analysis were done by the Neutral/Acid (KI/Thiosulphate) test performed on KI solution used to trap C1O2/C12 stripped out immediately after taking the process discharge sample.
The process conditions maintained during the runs were:
Run 1 Run 2 a) Pressure (mmHg) 480 480 b) (H2O2/NaClO3)Feed(g/g) 0.247 0.248 c) (H2SO4/NaC1O3)Feed(g/g) 2.489 2.222 d) [H2SO4]Feed(N) 27.3 27.3 e) [NaClO3]Feed(g/L) 480.5 618.4 f) Discharge Flow Rate (L/min) 41.86 42.13 g) Chlorate/Peroxide Feed Rate (L/min) 0.149 0.108 h) Acid Feed Flow Rate (L/min) 0.134 0.111 Results Run 1 Run 2 C102 Yield from NaClO3(%) 92.4 98.5 Chemical Efficiency(%) 99.0 99.5 H202 Consumption(g/g C102) 0.421 0.398 H2SO4 Consumption(g/g Cl02) 4.25 3.560 NaC1O3 Consumption(g/g C102) 1.708 1.602 Discharges i) [C102](g/L) 1.004 0.987 J) [C12](mg/L) 5.6 3.3 k) [NaC103](mg/L) 28.4 6.8 1) [H2SO4](g/L) 4.27 3.62 m) [C104](mg/L) 1.1 0.1 The above comparison clearly shows the superior performance of the process of the invention (run 2) in terms of yield, efficiency, chemical consumption for all feedstocks, product purity and the reduced losses of chemicals in the discharges (effluents).
SUMMARY OF DISCLOSURE
In summary of this disclosure, an improved process for the production of chlorine dioxide uses a concentrated, mixed feed of alkali metal chlorate and hydrogen peroxide. Modifications are possible within the scope of this invention.
Claims (8)
1. A method of forming chlorine dioxide, which comprises:
dissolving crystalline sodium chlorate in aqueous hydrogen peroxide solution to form an aqueous solution of hydrogen peroxide and sodium chlorate in a weight ratio of 0.16 to 0.30g H2O2/g NaClO3 and which has a sodium chlorate concentration at a specific weight ratio of hydrogen peroxide to sodium chlorate which is greater than that shown in continuous outline in Figure 1, and reacting chlorate ion in said aqueous solution of hydrogen peroxide and sodium chlorate in an aqueous acid reaction medium to produce chlorine dioxide according to the equation:
2ClO3- +H2O2+2H+-4 2ClO2+O2+2H2O.
dissolving crystalline sodium chlorate in aqueous hydrogen peroxide solution to form an aqueous solution of hydrogen peroxide and sodium chlorate in a weight ratio of 0.16 to 0.30g H2O2/g NaClO3 and which has a sodium chlorate concentration at a specific weight ratio of hydrogen peroxide to sodium chlorate which is greater than that shown in continuous outline in Figure 1, and reacting chlorate ion in said aqueous solution of hydrogen peroxide and sodium chlorate in an aqueous acid reaction medium to produce chlorine dioxide according to the equation:
2ClO3- +H2O2+2H+-4 2ClO2+O2+2H2O.
2. The method of claim 1 which is carried out in a tubular chlorine dioxide generator.
3. The method of claim 1 which is carried out in conical or dual-conical chlorine dioxide generator.
4. The method of any one of claims 1 to 3 wherein the concentration of the hydrogen peroxide solution is 10 to 50 wt%.
5. The method of claim 4 wherein the concentration of the hydrogen peroxide solution is 10 to 30 wt%.
6. The method of any one of claims 1 to 5 wherein sufficient sodium chlorate is dissolved in the hydrogen peroxide solution to substantially saturate the same.
7. The method of any one of claims 1 to 6, wherein said aqueous solution of hydrogen peroxide and sodium chlorate contains approximately 620 g/L NaClO3 and 155 g/L H2O2.
8. The method of claim 7 wherein said aqueous solution of hydrogen peroxide and sodium chlorate contains approximately 635 g/L NaClO3 and 110 g/L H2O2.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13858099P | 1999-06-11 | 1999-06-11 | |
| US60/138,580 | 1999-06-11 | ||
| US13974199P | 1999-06-18 | 1999-06-18 | |
| US60/139,741 | 1999-06-18 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2307818A1 CA2307818A1 (en) | 2000-12-11 |
| CA2307818C true CA2307818C (en) | 2012-03-13 |
Family
ID=26836330
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2307818 Expired - Lifetime CA2307818C (en) | 1999-06-11 | 2000-05-08 | Method of chlorine dioxide production |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2307818C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7070710B1 (en) | 1999-06-11 | 2006-07-04 | Eka Chemicals Inc. | Chemical composition and method |
-
2000
- 2000-05-08 CA CA 2307818 patent/CA2307818C/en not_active Expired - Lifetime
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| Publication number | Publication date |
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| CA2307818A1 (en) | 2000-12-11 |
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