PROCESS AND APPARATUS FOR CONCENTRATING HYDROGEN PEROXIDE TO 98 WT.% OR MORE

Abstract

The present invention is in the field of a method for obtaining high purity hydrogen peroxide, as well as a production unit for obtaining high purity hydrogen peroxide. It concerns a method for obtaining high purity hydrogen peroxide comprising the steps of providing an open container with an aqueous fluid comprising hydrogen peroxide, putting the open container with the aqueous fluid in a closed space, at ambient conditions providing an inert gas flow over and in contact with the aqueous fluid, removing water from the aqueous fluid at said ambient conditions by said gas flow, and thereby concentrating the hydrogen peroxide. The invention also concern a production unit for use in said method.

Claims

1. A method for obtaining high purity hydrogen peroxide comprising: providing an open container with an aqueous fluid comprising hydrogen peroxide, putting the open container with the aqueous fluid in a closed space, at ambient conditions providing an inert gas flow over and in contact with the aqueous fluid, removing water from the aqueous fluid at said ambient conditions by said gas flow, and thereby concentrating the H.sub.2O.sub.2.

2. The method according to claim 1, wherein the inert gas is >95% pure, and is selected from nitrogen, a noble gas, carbon dioxide, and combinations thereof.

3. The method according to claim 1, wherein the aqueous fluid comprises 1-99 wt. % water, and wherein the aqueous fluid comprises 1-85 wt. % hydrogen peroxide.

4. The method according to claim 1, wherein the water is removed during a period of 1-1000 hours.

5. The method according to claim 1, wherein ambient conditions are at a temperature of below 45° C., and at a pressure of 15-700 kPa, and in the absence of a catalyst, and in the absence of a voltage, and in the absence of a membrane, and in the absence of a reagent, and in the absence of a driving force, and in the absence of addition of thermal energy, and wherein the method is in-situ, and combinations thereof.

6. The method according to claim 1, wherein for a volume of 1-10 litre aqueous fluid the flow of inert gas is 1-1000 ccm/min.

7. The method according to claim 1, wherein the flow of inert gas is controlled by at least one valve.

8. The method according to claim 1, wherein the flow of gas is provided over a surface of the aqueous fluid, wherein said surface has a surface area of >100 cm.sup.2, and wherein a surface/volume ratio of the fluid is >10.sup.−3/m.

9. The method according to claim 1, wherein hydrogen peroxide is concentrated to a purity of >90 wt. %.

10. A production unit for use in the method of claim 1, comprising a concentration chamber, in the concentration chamber an open container for receiving aqueous fluid, an aqueous fluid supply comprising hydrogen peroxide in fluid connection with a source of aqueous fluid and the open container in the reaction chamber, an aqueous fluid outlet in fluid connection with a fluid receiver and the open container in the reaction chamber, a gas supply in fluid connection with a source of inert gas and the reaction chamber, and a valve for regulating an inflow of inert gas at ambient conditions.

11. The production unit according to claim 10, wherein the production unit is stand-alone.

Description

SUMMARY OF THE FIGURES

[0042] FIGS. 1, 2a-b, and 3-6 show experimental details of the present invention. FIGS. 7-8 show examples of the present device.

DETAILED DESCRIPTION OF FIGURES

[0043] In the figures: [0044] 1 source of inert gas [0045] 2 valve [0046] 3 open container [0047] 4 concentration chamber [0048] an aqueous fluid supply [0049] 6 an aqueous fluid outlet [0050] 7 controller [0051] 8 valve [0052] 9 outlet [0053] 10 outlet

[0054] FIG. 1 shows an experimental layout of the present production unit. Therein a concentration chamber 4 (Alpha Nanotech type) is shown. In the concentration chamber an open container 3 for receiving aqueous fluid is provided. Further an aqueous fluid supply 5 in fluid connection (Goodfellow PP) with a source of aqueous fluid (Merck H.sub.2O.sub.2 30%) and the open container in the reaction chamber for addition of the aqueous fluid comprising hydrogen peroxide is shown. Also an aqueous fluid outlet 6 in fluid connection with a fluid receiver and the open container in the reaction chamber is provided for removing hydrogen peroxide. A gas supply in fluid connection with a source of inert gas 1 (Anest Iwata) and the reaction chamber is further shown. Various valves 2 (Honeywell 67-7258) for regulating an inflow of inert gas may be present. And also at least one valve 8 for regulating an outflow of inert gas, and a controller 7 are shown.

[0055] Below is a short list of components used:

Nitrogen Gas generator, producing 99.5% pure N.sub.2, operating pressure: 2.5 Bar, operating Temperature: 20 degrees Celsius; Feedstock aqueous Hydrogen Peroxide, Hydrogen Peroxide 30%, EMSURE, ISO Sigma-Aldrich, CAS Number: 7722-84-1; concentration Dish 3 of Borosilicate glass, tubes of polypropylene, External Dynamic Air Environment Chamber 9 made of Poly-acetic acid.

[0056] FIG. 2a. Concentration vs time, concentration as result from refractive index measurement with Abbe refractometer.

[0057] FIG. 2b. Yield calculation of output solution. Result from initial weight and concentration vs final weight and concentration. Values from refractive index.

[0058] Inventors have now obtained H.sub.2O.sub.2 concentrations of up to 99.5%+, and would now like to include this in the patent application. They have updated the concentration and time graphs as shown in FIG. 2a-b. The time required to reach the higher concentrations has significantly reduced.

[0059] FIG. 3. Minimum activation energy to initiate decomposition vs H.sub.2O.sub.2 concentration.

[0060] FIG. 4. Ignition of concentrated H.sub.2O.sub.2 aqueous solution with Ethanol fuel.

[0061] FIG. 5. Ignition temperature vs H.sub.2O.sub.2 concentration.

[0062] FIG. 6. Ignition delay time vs H.sub.2O.sub.2 concentration.

[0063] FIG. 7 shows a first commercial version of the present apparatus, and FIG. 8 shows the present small stand-alone version. The inlet is to provide inert gas into the chamber. Here the water is extracted with the gas, and is then pushed through the outlet. This is a continuous process where the inert gas enters the H.sub.2O.sub.2 chamber and water is extracted by the gas. This then flows through the outlet carrying the water and leaving behind the concentrated H.sub.2O.sub.2. The source of the inert gas can be a gas storage cylinder or can be a system that extracts the inert gas straight from the atmosphere, or a combination of both. Therein the inert gas is passed over the H.sub.2O.sub.2. In the exit through 8, 9 and 10 the water is extracted from the inert gas and the inert gas is expelled back into the atmosphere, without having undergone any reaction itself (that is, inert gas composition remains the same). The gas may also be recirculated and reused to concentrate the H.sub.2O.sub.2. FIG. 8 shows the design of the final product that is presently being built. The user thereof will be able to collect any concentration H.sub.2O.sub.2 from this product, and along with wheels can ensure a high level of portability.

[0064] Experiment

[0065] Description of Production Unit Operation (FIG. 1)

[0066] This production unit comprises at least two main inputs, one for aqueous hydrogen peroxide (5), and one for an inert gas supply (1). The production unit is for purifying (hence concentrating) H.sub.2O.sub.2. The input of the feedstock hydrogen peroxide was provided at an initial concentration, which might be as low as 5 to 10% H.sub.2O.sub.2 aqueous solution) and volume that is required to be concentrated. This aqueous H.sub.2O.sub.2 in an amount of e.g. 2 is introduced into the concentration chamber (shown by 4 in FIG. 1) through the feed line (shown by 5 in FIG. 1). This concentration chamber consists of an open container, such as a concentration dish (shown by 3 in FIG. 1), held in place by mountings, where the initial aqueous hydrogen peroxide is placed. After placing the initial aqueous H.sub.2O.sub.2 into the dish, the feed line (shown by 5 in FIG. 1) is withdrawn to ensure no obstructions for the inert gas flow. After being withdrawn, the inert gas flow was initiated at a rate of 140 ccm/sec for a period of 20 hours to remove water from aqueous H.sub.2O.sub.2. This is initiated by actuating a flow control valve (shown by 2 in FIG. 1), to ensure a steady flow rate of inert gas into the concentration chamber. Due to this continuous input flow, the inert gas along with removed water vapour from aqueous H.sub.2O.sub.2 solution passes onto the external dynamic air environment through the valves (shown by 8 in FIG. 1). The external dynamic air environment chamber (shown by 9 in FIG. 1) consists of free moving air. This free moving air enters the chamber through the inlet (shown by 7 in FIG. 1), ensuring the continuous removal of the inert gas and the water vapour from the system though a valve (shown by 10 in FIG. 1), thereby preventing the accumulation and build-up of inert gas along with water vapour around the invention unit. The flow of the inert gas into the concentration chamber can be controlled by the valve (shown by 2 in FIG. 1, e.g. Bronkhorst FC-002) and the flow of the inert gas out of the concentration chamber can be controlled by the valve (shown by 8 in FIG. 1). The flow rate of the inert gas into and out of the concentration chamber can be set arbitrarily, such as within the claimed ranges, having an effect on both speed of concentration and final yield. The final concentrations of H.sub.2O.sub.2 (up to 99.6%) can be selected by allowing the inert gas supply for different time durations, as claimed. From FIGS. 2a and 2b, the time required and yield percent for a particular final H.sub.2O.sub.2 concentration can be obtained based on user requirement. Once the desired final concentration is reached, the valves shown by 2 and 8 are closed. After the valves have been closed, the concentrated hydrogen peroxide can be sampled by the output line as shown by 6 in FIG. 1. When the satisfactory final concentration of H.sub.2O.sub.2 is obtained, the sample can be extracted and used.

[0067] From graphs 2a and 2b a total time required for a required concentration can be obtained. It is noted that these graphs pertain to a particular and given flow rate of inert gas (140 ml/sec). This flow rate is considered optimal for the present production unit. For a shorter duration of the concentration procedure, a fast flow rate of the inert gas could be used. But this faster flow rate could affect the percent yield of the final concentrated H.sub.2O.sub.2. In order to significantly improve the final yield, the flow rate may typically be optimised. This will lead to larger amounts of final concentrated H.sub.2O.sub.2, based on the optimised flow rate selected.

[0068] Testing

[0069] Two methods were used in different qualities to characterize the concentration of the solution. These are:

[0070] Quantitatively: refractive index with the use of Abbe refractometer in controlled conditions (20° C., 1 atm). This optical approach is used to monitor H.sub.2O.sub.2 concentration. In this method the following procedure was followed; the varied concentration range of H.sub.2O.sub.2 produced by the present invention was evaluated through refractive index of H.sub.2O.sub.2 droplets using an Abbe refractometer. Using this technique one can measure the concentrations of H.sub.2O.sub.2. First the Abbe refractometer device was calibrated with a distilled H.sub.2O droplet followed by H.sub.2O.sub.2 concentrations ranging from 10% to 99.6%. Water has a refractive index of 1.33, and 100% pure H.sub.2O.sub.2 has a refractive index of 1.41 (at visible wavelengths of light), with aqueous solutions of H.sub.2O.sub.2 and water lying in between these values. As the concentration of H.sub.2O.sub.2 in the solution increases, it follows that the refractive index will increase, and by measuring the refractive index, it is possible to determine a concentration of H.sub.2O.sub.2 in a H.sub.2O.sub.2 aqueous solution.

[0071] Qualitatively: recording of decomposition temperature of the solution through fast recording data acquisition system (55 Hz) with k-type thermocouples. The process was initiated trough thermal activation of the solution. Monitoring the concentration of H.sub.2O.sub.2 in H.sub.2O.sub.2 aqueous solution through electrochemical redox reaction, where in the heat energy of the exothermic reaction increases with increasing H.sub.2O.sub.2 concentration. For this qualitative method, small amount of external source of temperature was used to increase the rate of decomposition of H.sub.2O.sub.2 aqueous solution.

[0072] Decomposition of concentrated H.sub.2O.sub.2 solutions: This approach helps to predict qualitatively the varied H.sub.2O.sub.2 concentrated solution decomposition with minimum input activation energy in terms of temperature. For qualitative evaluation of concentration, a H.sub.2O.sub.2 concentration from 80% and above have been investigated.

[0073] Evaluation 1—Decomposition Input Temperature (T.sub.Min): The process was initiated with thermal activation of the H.sub.2O.sub.2 aqueous solution by providing a minimum input activation energy to initiate decomposition. In this evaluation experiment, single drops of varied concentrations of H.sub.2O.sub.2 (from 80% to 95%) were released over a thermal heating plate from a height of 17 cm. H.sub.2O.sub.2 droplets of 0.13 mL of volume were generated through an electronic syringe pump. As soon as the concentrated H.sub.2O.sub.2 droplet comes in contact with the heating plate, it undergoes rapid exothermic decomposition followed by release of energy in terms of temperature. With increase in H.sub.2O.sub.2 concentration (from 80% to 95% pure) the minimum input energy (T.sub.Min) needed for decomposition decreases as seen in FIG. 3.

[0074] Ignition of concentrated H.sub.2O.sub.2 aqueous solution with fuel (Ethanol): Recording of ignition of the H.sub.2O.sub.2 droplet (concentration from 80% to 95%) once it comes in contact with a fuel ethanol (C2H.sub.5OH) droplet done using a photron high speed camera at 6400 fps. The reaction starts with minimum activation thermal energy supply of 250° C. via a heating plate to the H.sub.2O.sub.2 droplet (0.13 mL volume) at different concentrations (80% to 95% pure) and subsequent addition of an ethanol (99.5% pure) droplet from a height of 17 cm to initiate ignition. A electronic syringe pump was used to generate H.sub.2O.sub.2 and Ethanol droplet. With an increase in H.sub.2O.sub.2 concentration, it is expected that the ignition temperature increases followed by a decrease in ignition delay time (time between first contact and the start of ignition). This is due to increased energetic content with increased H.sub.2O.sub.2 concentration. This trend can be seen in FIG. 4-6.