CZ2021398A3 - A method for producing hydrogen peroxide in plasma in situ and a device for this - Google Patents

Abstract

A method of producing hydrogen peroxide using a barrier discharge between the electrodes of a plasma reactor, into which a liquid containing water is fed into a closable container. The container is closed, a negative pressure is created in it allowing the formation of vapors, a high voltage is applied to the electrodes, which causes a plasma discharge, which causes the decomposition of the vapors to form hydrogen peroxide. Subsequently, the pressure will increase again and the hydrogen peroxide will pass back into the remaining liquid, for its further action. The device consists of a plasma reactor, where the material of the barrier, which forms at least part of the reactor body, is glass, porcelain, ceramics, etc. The reactor body is a hollow container (1) with a volume larger than the filling (6) of the working liquid and which can be closed on one side with a plug ( 5) and from the second by a movable felt (2) controlled by a sliding unit (7). Externally, on the wall of the container (1) outside the volume for the liquid filling (6) of the reactor, electrodes (31, 32) are arranged at a distance from each other and are stored in an insulator (4).

Description

A method for the production of hydrogen peroxide in plasma in situ and a device for carrying out this method

Field of technology

The present invention relates to a method and device for the production of hydrogen peroxide in situ with the help of a barrier discharge in water vapor under reduced pressure and also a plasma reactor.

Current state of the art

It is known that a large number of chemical reactions can occur in gases and liquids remaining in contact with the plasma, the final ratio of products being dependent on a number of factors. One of the most well-known reactions in the water environment is the formation of hydrogen peroxide, see e.g. Czech patent No. 308532, which occurs by the detachment of a hydrogen atom from a water molecule followed by the rapid recombination of two hydroxyl radicals. In general, it can be said that the simpler the composition of the reaction mixture, i.e. both the liquid and gas phases, the fewer end products are formed. This means that the discharge in water vapor leads primarily to the formation of hydrogen peroxide, oxygen, hydrogen and ozone.

A vacuum discharge has the advantage of being relatively easy to ignite and sustain. Analogous barrier discharge (dielectric barrier discharge, DBD) is advantageous in that the barrier material, e.g. glass, ceramics, etc., limits the current in the discharge and thus prevents heating, degradation of metal electrodes and contamination of liquid samples. The combination of these two properties enables the production of hydrogen peroxide, which can serve as a substrate in enzymatic reactions. There are at least four types of enzymes that use H2O2 as a substrate: peroxidases, haloperoxidases, hydrolases, and peroxygenases. In addition, there are organic and inorganic catalysts that also use H2O2. Since hydrogen peroxide is considered a "green" oxidant, it can be expected that interest in this substance and its application spectrum will expand.

Currently, hydrogen peroxide is produced using a cyclic process developed by BASF in 1939. This process consists in reducing an anthraquinone derivative with hydrogen in the presence of a catalyst, after which the resulting hydroquinone is oxidized by oxygen from the air. Hydrogen peroxide is subsequently obtained from the reaction mixture, while anthraquinone continues into further cycles of reduction and oxidation. In addition to this industrial method, there are a number of reactions whose product is hydrogen peroxide and which can be used to generate peroxide in situ. In this way, the technically complex dosing of hydrogen peroxide into the reaction mixture can be replaced and its dilution can be avoided. For example, the enzyme glucose oxidase catalyzes the formation of hydrogen peroxide from glucose and oxygen, and the rate of this reaction can be controlled. Another option is the electrochemical production of hydrogen peroxide or production using photochemical reactions.

The in situ production of hydrogen peroxide for enzymatic reactions using plasma has also been described, specifically using the commercially available PiasmaDerm device (barrier discharge, CINOGY, Duderstadt, Germany). This process takes place at atmospheric pressure and temperature, with the barrier electrode positioned just above the surface of the liquid. Part of the energy is thus consumed to create nitrogen oxides or ozone, which are undesirable here. In addition, relatively rapid degradation of the enzyme by plasma may occur.

Current biotechnology and diagnostics offer a wide range of kits and tests that are designed for single use and work with fluid volumes in the order of microliters. Often these protocols can be automated and used with pipetting robots, allowing thousands of analyzes to be performed per day. Microfluidic chip technology, where extremely small sample volumes are worked with, is also constantly being developed. The use of plasma is not new here, however, due to the small dimensions of the chips, it is not possible to use too high a voltage. For this reason, reducing the breakdown voltage by reducing the pressure appears to be an interesting possibility. However, according to current knowledge, there is no solution that would combine these advanced technologies with the production of hydrogen peroxide in situ using plasma under reduced pressure.

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The task of the invention is therefore to eliminate the above-mentioned lack of the current state of the art and to propose a method and a compact device for the production of hydrogen peroxide in situ, which would be compatible with the technologies available in the field of medicine, biotechnology or diagnostics.

The essence of the invention

The above-mentioned shortcomings of the state of the art are eliminated and the set task is solved by the method of producing hydrogen peroxide in plasma in situ using a barrier discharge between the electrodes of a plasma reactor under the pressure of saturated water vapor according to the invention, the essence of which is that a working liquid is introduced into the closable container of the plasma reactor containing water, the container is closed, then a negative pressure is created in the container, so that its vapors are formed above the working liquid, a high voltage is applied to the electrodes of the plasma reactor located on the outer surfaces of the walls of the reactor container defining the volume of the container containing the vapors, which is induced through the barrier wall of the container a plasma discharge, the action of which will cause the decomposition of vapors to form hydrogen peroxide, after which the pressure in the vessel will increase again and the resulting hydrogen peroxide will pass back into the remaining liquid for its desired effect.

For the implementation of the method described above, a device for the production of hydrogen peroxide in plasma in situ at the pressure of saturated water vapor is proposed, which consists of a plasma reactor for a barrier discharge, the electrodes of which can be connected to a high voltage source and where the barrier material, which forms at least part of the reactor body . on the wall of the vessel made of barrier material placed outside the volume for the working fluid in the insulator of the electrodes arranged at a distance from each other.

According to the invention, it is advantageous if the reactor vessel with a volume larger than the volume of the working liquid filling is arranged vertically and the electrodes are annular electrodes spaced apart in the direction of piston travel.

For practical reasons, it is advantageous if the reactor vessel consists of a glass hollow cylinder of circular cross-section. However, porcelain, ceramics and the like can also be used.

The piston advance unit can be operated manually and/or pneumatically, hydraulically, or electrically for precise adjustment of the negative pressure above the liquid filling of the vessel.

An embodiment in which one of the electrodes could be formed by a conductive part of the piston is also conceivable.

The above-described plasma reactor for the production of hydrogen peroxide under reduced pressure according to the invention allows the production of hydrogen peroxide in situ, so it is suitable for use especially in medicine for diagnosis, or for example for biotechnology. The plasma in this reactor can be distant from the surface of the sample, which will limit enzyme degradation. In addition, since the plasma burns in water vapor, energy will not be used to produce NO _X , as is the case with an atmospheric discharge.

Clarification of drawings

The invention will further be explained in more detail with the help of a description of an exemplary embodiment shown in the attached drawings, in which it represents:

Fig. 1 - arrangement of the device reactor in the working position immediately after filling with the working liquid;

-2 CZ 2021 - 398 A3 Fig. 2 - state of the reactor when the pressure above the working liquid filling was reduced by the stroke of the piston and Fig. 3 - graph of the increase of hydrogen peroxide over time in a possible example of the use of the invention described below.

An example of the implementation of the invention

Fig. 1 schematically shows the working position and state of the reactor immediately after filling a part of its container 1 with the determined size of the filling 6 of the working liquid and closing the working volume on one side with a piston 2 and on the other side with a stopper 5. The first annular electrode 31 and the second annular electrode arranged at a distance electrode 32 are located externally on the wall of container 1 outside, or above the filling 6 in the insulator 4. In this case, the piston 2 is connected by a piston rod to the manual displacement unit T

In Fig. 2, the reactor according to the invention is shown in a state where voltage can be applied to the electrodes 31, 32, the piston 2 is moved away from the liquid filling 6, so that in the space above the filling liquid 6 there is a reduced pressure and a saturated vapor of the working liquid. The discharge that occurs when a high voltage is applied to the steam results in the formation of H2O2 in the gas phase, H2 (hydrogen), O2 (oxygen) and possibly other reaction products.

As the pictures indicate, the basis of the advantageous possible implementation of the device for the production of hydrogen peroxide in situ using a barrier discharge in water vapor according to the invention could advantageously be a classic syringe, on the shell of which, or container 1 would have two ring electrodes 31, 32 fitted externally in the insulator 4 with leads for connection to a high voltage source. In the transparent hollow glass cylinder of the syringe, between its bottom and the sealing piston 2, there is both a space for the liquid filling 6 and an evacuated space for steam, which is created by the movement of the piston 2 from the filling 6 by the action of an axial force on the shaped extension of the piston rod. In this case, this would represent the displacement unit 7. After connecting the electrodes 31, 32 to the high voltage source, a plasma discharge would occur in the cylinder causing the formation of hydrogen peroxide. Even with such a possible simple prototype design, the space for the liquid filling 6 must be closed before the pressure above the surface is reduced by the plug 5.

By increasing the pressure again, hydrogen peroxide gas passes into the solution and the desired reaction can occur.

The described embodiments can be used, for example, for the oxidation of tetramethylbenzidine (TMB) using in situ generated hydrogen peroxide in the presence of horseradish peroxidase (HRP).

HRP

TMB

The above-mentioned glass syringe with piston 2, on which copper electrodes 31, 32 insulated with silicone would be placed, can serve as a prototype. The syringe must be tightly closed at the end with a stopper 5. During approximately one minute of treatment in the liquid solution, the blue color of oxidized TMB is formed.

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Another example of possible use is the determination of hydrogen peroxide using a titanium complex (Ti (IV)) in an acidic environment - increase over time. In this case, a high voltage was applied to the metal part of the glass syringe piston and to the bottom copper electrode. Approximately 100 μΐ 5 deionized water was treated. The operation of the reactor took place in cycles, with one cycle lasting about 8 seconds.

The graph in Fig. 3 shows the increase in hydrogen peroxide concentrations.

Claims (2)

1. A method of producing hydrogen peroxide in plasma in situ using a barrier discharge between the electrodes of a plasma reactor under the pressure of saturated water vapor, characterized by the fact that a working liquid containing water is brought into the closable container of the plasma reactor, the container is closed, and subsequently a negative pressure, so that its vapors form above the working liquid, a high voltage is applied to the electrodes of the plasma reactor located on the outer surfaces of the walls of the reactor vessel defining the volume of the vessel containing the vapors, which causes a plasma discharge through the barrier wall of the vessel, which causes the vapors to decompose to form peroxide of hydrogen, after which the pressure in the container will increase again and the hydrogen peroxide formed will pass back into the remaining liquid for its desired action. 2. The method of producing hydrogen peroxide according to claim 1, characterized in that the pressure above the working liquid is reduced, or will increase, by increasing, or by reducing the volume of the reactor vessel. 3. The device for the production of hydrogen peroxide in plasma in situ at the pressure of saturated water vapor according to claims 1 and 2, which consists of a plasma reactor for a barrier discharge, the electrodes of which can be connected to a high voltage source and where the material of the barrier, which forms at least part of the body of the reactor , is selected from the group including glass, porcelain and ceramics, characterized by the fact that the body of the reactor is a hollow container (1) that can be closed on one side by a stopper (5) and on the opposite side by a tightly fitted moving piston (2) connected to a sliding unit (7) ), while the electrodes (31, 32) stored in the insulator (4) are located externally on the wall of the container (1) made of barrier material outside the space for the filling (6) of the working liquid and are arranged at a distance from each other. 4. Device according to claim 3, characterized in that the vessel (1) of the reactor, the volume of which is greater than the volume of the filling (6) of the working liquid, is formed by a vertically arranged hollow cylinder of circular cross-section made of glass, porcelain or ceramics. 5. Device according to claims 3 or 4, characterized in that the electrodes (31, 32) are annular electrodes spaced apart in the direction of displacement of the piston (2). 6. Device according to claim 3 to 5, characterized in that the displacement unit (7) of the piston (2) is a manual and/or pneumatically, hydraulically or electrically controllable displacement unit (7). 2 drawings