SI26410A - New hydrogen peroxide purification procedure - Google Patents

Abstract

The present invention describes a new process for purifying hydrogen peroxide (H2O2) with a reagent that is a combination of supercritical CO2 (scCO2) and tetrabutyl urea (TBU). It is a high-pressure process in a reactor, which is preferably a countercurrent column, where scCO2 in combination with tetrabutyl urea (TBU) is used as a medium, i.e. a reagent. TBU is added in the co-flow with scCO2 in the appropriate ratio to H2O2. The product obtained is purified hydrogen peroxide. The total organic carbon (TOC) value of the obtained product is monitored at the outlet, which is determined in ppm and is below 50 ppm.

Description

A NEW PROCEDURE FOR CLEANING HYDROGEN PEROSKID

DESCRIPTION OF THE INVENTION

The essence of the invention is a new hydrogen peroxide (H ₂ O ₂ ) purification process, where supercritical fluid scCO ₂ is used as a purification reagent in combination with tetrabutyl urea (TBU).

The classic purification techniques used to purify hydrogen peroxide are distillations, adsorption, ion exchange, crystallization, membrane separation. These processes are energy consuming. The proposed hydrogen peroxide purification process provides significant technical advantages, a process with fewer operations that consume less energy and less raw materials. It is a high-pressure process that takes place at a pressure of 50 to 500 bar and a temperature in the range of 10 to 100 °C. scCO ₂ in combination with TBU is used as a medium. TBU is added to the combination of both reagents in the co-flow together with scCO ₂ in the appropriate ratio to H ₂ O ₂ . The product we get is purified hydrogen peroxide. The total organic carbon (TOC) value of the obtained product at the outlet is monitored, which is determined in ppm.

STATE OF THE ART

Various techniques for the purification of hydrogen peroxide are known: distillation [1], adsorption of ion exchange resins [2-4], recrystallization, membrane separation [5], scCO ₂ [6] can be used as an alternative for H ₂ O ₂ purification,

Hydrogen peroxide (H ₂ O ₂ ) is a slightly acidic, clear and colorless liquid that is completely miscible with water in all proportions. It plays an important role in protecting the human body against microbes and viruses. It is known worldwide as a strong environmentally friendly oxidant, which in its purified form is non-toxic and easily decomposes into by-products [7], Worldwide, hydrogen peroxide is almost exclusively produced by the anthraquinone (AO) process, which is a very energy-consuming process [8], In this process, hydrogen peroxide is produced by sequential hydrogenation and oxidation of alkylanthraquinone dissolved in a mixture of organic solvents, followed by processing of the product in countercurrent liquid-liquid extraction with water [9], Suboptimal partition coefficient and organic solvent contamination during processing liquid-liquid extraction requires the further energy-consuming use of purification methods: distillation, adsorption and ion exchange resins, crystallization, membrane separation. The concentrated, high-purity hydrogen peroxide is then stabilized against unwanted and uncontrolled decomposition by adding proprietary stabilizers.

High pressure is increasingly used as a process tool in sustainable development. The use of supercritical fluids can help solve the shortcomings of many classical processes for the processing and production of products [10], Supercritical extraction (SFE) is an important method for large-scale purification of complex liquid or solid substances, such as waste process streams. The main advantage of supercritical liquid-liquid extraction is that, after extraction, the supercritical fluid can be easily removed by lowering the temperature and/or pressure. The supercritical fluid becomes a gas and the extracted material condenses into a liquid or solid.

Ultra pure hydrogen peroxide solution is prepared by purifying industrial hydrogen peroxide solution, which is generally produced using the anthraquinone method. The process consists of successive hydrogenation, filtration and oxidation and liquid/liquid extraction stages. A number of ancillary processes are also required. Industrial hydrogen peroxide solution contains certain amounts of organic, inorganic and metallic compounds. Organic impurities present in hydrogen peroxide solutions are introduced by working solvents and soluble decomposition products, including tributyl phosphate aromatics (TOP), anthraquinone and its derivatives [1],

In order to eliminate the above-mentioned impurities in the hydrogen peroxide solution and reduce the content of total organic carbon - TOG, many cleaning technologies have been developed. At present, distillation [1], adsorption and ion exchange technology [2-4], recrystallization [11], supercritical extraction [6], flocculation technology, reagent combination technology and membrane separation [5] such as microfiltration, ultrafiltration and reverse osmosis. Crystallization, flocculation and the addition of precipitation agents represent additional technologies.

Currently, for the preparation of ultrapure hydrogen peroxide, distillation is used first, followed by a combination of different membrane separation techniques or ion exchange processes and adsorption [12],

Distillation is a reliable and simple method for an industrial scale. However, it involves the use of an inert column made of fluoropolymers (poor thermal conductors), which increase energy consumption, and at the same time, the purity of the distilled hydrogen peroxide is not high enough [13].

Ion exchange is the most important ultra-efficient cleaning process. The regeneration of ion exchange resins means additional waste streams and the use of dangerous chemicals (strong acids and bases) and the thermal decomposition of the hydrogen peroxide solution [3]. The crystals are then collected, washed and melted to obtain a high concentration of hydrogen peroxide.

Membrane technologies (reverse osmosis) are emerging as the most appropriate option for ultra-efficient cleaning in accordance with environmental criteria. No secondary chemicals are required and therefore no waste streams. Nevertheless, the ultra-efficient purification of hydrogen peroxide can be considered a very demanding process, since a strong oxidizing medium can promote the degradation of polymer membranes [14]·

Lin et al. [15] investigated a suitable activated carbon (AC) for the selective removal of organic impurities from an industrial aqueous solution of H ₂ O ₂ , for the production of ultra-pure H ₂ O ₂ . The results showed that the capacity of activated carbon to remove organic impurities from aqueous solutions of hydrogen peroxide is mainly related to the microspore structure.

Rueda et al. [16] achieved the direct synthesis of hydrogen peroxide from H ₂ and 0 ₂ with water as a solvent in a semi-discontinuous mixed reactor system. This process represents a greener alternative to the traditional process using anthraquinone or direct synthesis using organic solvents.

As an alternative to hydrogen peroxide cleaning, scCO ₂ can be used, but there is very little research in this area. Blanco-Brieva et al. [17] reported notable results when performing the synthesis at a high pressure of 9.5 MPa in a metabolic medium. Hancu et al. [18] used compounds that functionalize a number of amino and hydroxyl-AOs to promote mixing with C0 ₂ at lower pressures and thereby increase the solubility of C0 ₂ .

Since there is very little research in the field of hydrogen peroxide purification with supercritical fluids or with tetrabutyl urea, in order to support our invention, we undertook preliminary research on the purification of hydrogen peroxide with only supercritical C0 ₂ and only with tetrabutyl urea - implementation examples from 1 to 7). In the case of cleaning with scCO _2, we managed to reduce the TOC to 120 ppm, while with TBU we reduced the TOC value to 70 ppm. With this, we proved that the combination of both scCO ₂ and TBU reagents is the most effective in cleaning hydrogen peroxide.

DISADVANTAGES OF EXISTING SOLUTIONS

Conventional purification processes such as: distillation, adsorption, ion exchange, crystallization, membrane separation are energy-consuming. Purification of hydrogen peroxide by the proposed process provides significant technical advantages, a process with fewer operations that consume less energy and less raw materials. The process according to the invention also achieves a high quality (purity) of the product compared to current processes.

Purification of hydrogen peroxide, where the medium, i.e. the reagent, scCO ₂ , provides significant technical advantages, a process with fewer operations that consume less energy and less raw materials. All these procedures involving scCO ₂ were performed on a laboratory scale. There is no information on the production or purification of hydrogen peroxide on a large scale that is economical and environmentally friendly.

Research has shown that the purification of hydrogen peroxide, where the medium, i.e. the reagent, is TBU (extraction with TBU), also significantly lowers the values of total organic carbon - TOC compared to the input solution H ₂ O ₂ (raw H ₂ O ₂ ). Therefore, TBU appears as an alternative for the purification of H ₂ O ₂ .

Purification of hydrogen peroxide where the medium, i.e. the reagent, is a combination of scCO ₂ and TBU further lowers the TOC value in the peroxide.

DETAILED DESCRIPTION

The working solution used for the preparation of hydrogen peroxide contains anthraquinones and their derivatives. These by-products contain a very complex mixture of decomposition products, in which they cannot actively participate in the production of hydrogen peroxide, as they cause a higher viscosity and density of the working solution. Decomposition products must be removed from the working solution and thereby prevent an increase in the density and viscosity of the working solution [19], There are many different organic substances present in unpurified hydrogen peroxide such as: organic solvents, quinones dissolved in organic solvents, water-soluble degradation products of solvents, especially sextate , emulsified solvents. Due to such a different composition, we cannot remove all organic substances by extraction alone, and above all we cannot remove water-soluble substances. On the extraction efficiency itself or purification is influenced by the distribution coefficient, which depends on the nature of the solvent, the intensity of mixing, the solubility of the extraction solvent in the peroxide phases, and the temperature.

It is therefore necessary to clean the hydrogen peroxide properly, i.e. remove the decomposition products (mainly organic solvents) and thereby reduce the content of total organic carbon - TOC, which is achieved by the process according to the invention.

The invention is described below and presented in the figure.

Figure 1 shows the scheme of purification of hydrogen peroxide in a countercurrent column or in the reactor.

The essence of the invention is a new purification process - extraction of hydrogen peroxide (H ₂ O ₂ ), whereby the process is a high-pressure process and takes place in the reactor R at a pressure in the range between 50 and 500 bar and a temperature in the range between 10-100 °C. Preferably, the pressure is in the range between 100 and 500 bar and the temperature is in the range between 30 - 60 °C. As a medium or as a reagent, the process uses a supercritical fluid, which is preferably supercritical CO ₂ (scCO ₂ ), in combination with tetrabutyl urea (TBU). TBU is added in the co-flow together with scCO ₂ in the appropriate ratio to H ₂ O ₂ , whereby the TBU content in scCO ₂ is between 0.1 wt. % to 80 wt. % and the ratio of TBU/ scCO ₂ to H ₂ O ₂ is between 0.1 and 10. The ratio of hydrogen peroxide to scCO ₂ , i.e. S/F, ranges from 5 kg/kg to 30 kg/kg.

CO ₂ is supplied from tank T2 and tetrabutyl urea from tank T3. Both reagents are led via the high-pressure pump - HP2 to the preheater - P. Unpurified hydrogen peroxide enters the reactor R from the tank Tl. The impurities created during cleaning are collected in the separator Fig. Purified hydrogen peroxide is sent to a centrifuge in separator S2, where TBU (supernantant) and H ₂ O ₂ (lower phase of purified peroxide) separate from each other, the resulting product is purified hydrogen peroxide, which is collected in separator S3. Gaseous CO ₂ , which emerges in Sl, is recycled after the process is finished. First, we remove the impurities in the separator S4, then the CO ₂ is cooled by the cooling system - H and led back to the high-pressure pump HP2 and then back to the reactor R.

The resulting product is monitored at the outlet for the value of total organic carbon - TOC, which is determined in ppm and represents the value of impurities. The resulting product is purified hydrogen peroxide with an impurity content below 50 ppm.

The advantage of using a combination of scCO ₂ and TBU is that TBU and H ₂ O ₂ do not mix with each other and are easily separated by centrifugation. The used TBU and scCO ₂ are recirculated.

The hydrogen peroxide purification process therefore includes the following steps:

- preheating of the reactor R to T between 10 and 100 degrees;

simultaneous introduction of CO ₂ from tank T2 and tetrabutyl urea from tank T3 at a pressure between 50 and 500 bar into reactor R, whereby both reagents are led via high-pressure pump HP2 to preheater P and then into reactor R,

- introduction of peroxide from tank Tl via HPLC pump HP1 into reactor R, during which extraction of peroxide takes place with a combination of supercritical CO ₂ and tetrabutyl urea;

- collection and management of impurities, which occurred during the extraction, in separator Sl, and collection and management of peroxide in separator S2;

centrifugation of TBU and peroxide on the centrifuge in the separator S2 and leading the purified peroxide to the separator S3;

recycling C0 ₂ in the separator S1, removing the impurities in the separator S4 and cooling the C0 ₂ with the cooling system H, and returning the C0 ₂ to the high-pressure pump HP2.

Preferably, the reactor R, where the hydrogen peroxide (H ₂ O ₂ ) purification process is carried out, is a stainless steel countercurrent column 1 m -10 m long, which is filled with an inert filler made of glass beads with a diameter of 0.1 -1 cm. The length of filling is 1 - 5 m. Reactor R is surrounded by an electric heating jacket - GP. At the top of the reactor R there is a discharge valve VI, at the bottom of the reactor R there is a discharge valve V2. CO ₂ is supplied from tank T2 and tetrabutyl urea from tank T3. Both reagents are led via a high-pressure pump - HP2 to preheating - P. Preheated scCO ₂ and TBU are introduced into the lower part of the reactor - R so that the TBU content in scCO ₂ is between 0.1 wt. % to 80 wt. %. Unpurified hydrogen peroxide enters the reactor R from the tank Tl at the top of the reactor - R via the HPLC pump - HP1. Suitable flows of hydrogen peroxide in the system are determined according to the scCO ₂ ratio, where the hydrogen peroxide to scCO ₂ ratio is from 5 kg/kg to 30 kg/kg. The impurities produced during the cleaning are collected on top of the reactor R in the separator Fig. The purified hydrogen peroxide is led from the lower part of the reactor R to the centrifuge in the separator S2, where TBU (supernatant) and H ₂ O ₂ (the lower phase of the purified peroxide) separate from each other, the resulting product is purified hydrogen peroxide, which is collected in the separator S3 . Gaseous CO ₂ , which emerges in Sl, is recycled after the process is finished. First, we remove the impurities in the separator S4, then the CO ₂ is cooled by the cooling system - H and led back to the high-pressure pump HP2 and then back to the reactor R.

A sample of crude and purified hydrogen peroxide is analyzed for total organic carbon with a TOC Carbon Analyzer, Shimatzu. The result is given as total organic carbon - TOC in ppm.

The process according to the invention is preferably carried out in a counter-current column, but the process can also be carried out in a co-current column or in a batch reactor. In the case of a co-flow column, all components (hydrogen peroxide, scCO ₂ and TBU) enter the reactor at the same time at the bottom and exit at the top, whereby the scCO ₂ is recycled, and the TBU and purified peroxide are separated in a separator. The ratios and flow rates remain the same as in the counter-current system. In the case of a batch reactor, TBU and H ₂ O ₂ and scCO ₂ under operating P and T are introduced into the batch reactor (high-pressure reactor) under the same conditions and pressures, and after the process is finished, the pressure, H ₂ O ₂ and TBU phases are released from the system and they separate, the lower phase being the purified phase of hydrogen peroxide.

IMPLEMENTATION EXAMPLES

Examples 1-7 are preliminary experiments that confirm that the invention, which includes both reagents in the purification, i.e. TBU and scCO ₂ , is the most suitable.

1. Implementation example - purification of H ₂ O ₂ with scCO ₂

Extraction of H ₂ O ₂ in a countercurrent column with scCO ₂ solvent. A schematic of the column is shown in Figure 1. The peroxide phase (TOC = 500 - 600 ppm) was introduced at the top of the column, while the scCO ₂ entered at the bottom. The column was heated to operating temperature and preheated scCO ₂ was introduced into the system with the help of a high-pressure pump. We then began pumping hydrogen peroxide into the system at the top of the column. Accordingly, we have chosen a suitable flow of hydrogen peroxide into the system. Supercritical CO ₂ was continuously introduced in countercurrent in the lower part of the column. The ratio of peroxide to scCO ₂ (S/F) was 10 kg/kg. The extraction took place for 150 min. The impurities produced during the cleaning were collected at the top of the column in the separator Sl, while the purified hydrogen peroxide was collected in the separator at the lower part of the column S2 and S3. In the end, we obtained purified hydrogen peroxide, which we measured for a total carbon content of TOC = 200 ppm.

2. Implementation example - purification of H ₂ O ₂ with scCO ₂

H ₂ O ₂ extraction takes place in a countercurrent column with scCO ₂ solvent. A schematic of the column is shown in Figure 1. The peroxide phase (TOC = 600 ppm) was introduced at the top of the column, while the scCO ₂ entered at the bottom. The column was heated to operating temperature and preheated scCO ₂ was introduced into the system with the help of a high-pressure pump. We then began pumping hydrogen peroxide into the system at the top of the column. Accordingly, we have chosen a suitable flow of hydrogen peroxide into the system. Supercritical CO ₂ was continuously introduced in countercurrent in the lower part of the column. The ratio of peroxide to scCO ₂ (S/F) was 6 kg/kg. The extraction took place for 100 min. Impurities formed during the extraction were collected at the top of the column in the separator Sl, while purified hydrogen peroxide was collected in the separator at the bottom of the column S2 and S3. In the end, we obtained purified hydrogen peroxide, which we measured for a total carbon content of TOC = 160 ppm.

3. Implementation example - purification of H ₂ O ₂ with scCO ₂

The extraction of H ₂ O ₂ was carried out in a countercurrent column with scCO ₂ solvent. A schematic of the column is shown in Figure 1. The peroxide phase (TOC = 550 ppm) was introduced at the top of the column, while scCO ₂ entered at the bottom. The column was heated to operating temperature and preheated scCO ₂ was introduced into the system with the help of a high-pressure pump. We then began pumping hydrogen peroxide into the system at the top of the column. Accordingly, we have chosen a suitable flow of hydrogen peroxide into the system. Supercritical CO ₂ was continuously introduced in countercurrent in the lower part of the column. The ratio of peroxide to scCO ₂ (S/F) was 20 kg/kg. The cleaning took 120 min. Impurities produced during the extraction are collected at the top of the column in the separator Sl, while purified hydrogen peroxide is collected in the separator at the bottom of the column S2 and S3. In the end, we obtained purified hydrogen peroxide, which we measured for a total carbon content of TOC = 130 ppm.

4. Implementation example - purification of H ₂ O ₂ with scCO ₂

We performed the extraction of osmosis-purified H ₂ O ₂ with scCO ₂ solvent. The peroxide phase (TOC = 51 ppm) was introduced at the top of the column while scCO ₂ entered at the bottom. The column was heated to operating temperature and preheated scCO ₂ was introduced into the system with the help of a high-pressure pump. We then began pumping hydrogen peroxide into the system at the top of the column. Accordingly, we have chosen a suitable flow rate of hydrogen peroxide into the system. Supercritical CO ₂ was continuously introduced in countercurrent in the lower part of the column. The ratio of peroxide to scCO ₂ (S/F) was 20 kg/kg. The cleaning took 120 min.

Impurities produced during the extraction were collected at the top of the column in the Sl HPS separator, while the purified hydrogen peroxide was collected in the separator at the bottom of the S2 and S3 columns. In the end, we obtained purified hydrogen peroxide, which we measured for a total carbon content of TOC = 100 ppm.

5. Implementation example - purification of H ₂ O ₂ with TBU

Extraction of H ₂ O ₂ (TOC= 500 ppm) with TBU. First, we performed preliminary studies of H ₂ O ₂ extraction with TBU in a column in the ratio TBU:H ₂ O ₂ = 1:1. The scheme of the column is shown in Figure 1. H ₂ O ₂ (φ _ν = 3 g/min) enters the system with the help of a high-pressure pump at the top of the column, while TBU (^ = 3 g/min) is introduced into the column at the bottom. The peroxide phase is led to separator S2 at the bottom of the column, where H ₂ O ₂ and TBU peroxide are separated by centrifugation and collected in separator S3. Total organic carbon - TOC in ppm is measured in the peroxide phase. The experiments lasted 180 min. The beneficial effect of H ₂ O ₂ extraction is achieved already after 60 min. By extending the cleaning time, we do not achieve lower TOC values at the outlet. Pure TBU was shown to scavenge hydrogen peroxide from TOC approx. 600 ppm at approx. 120 ppm.

6. Implementation example - purification of H ₂ O ₂ with TBU

Extraction of H ₂ O ₂ (TOC= 550 ppm) with TBU in a column in the ratio TBU:H ₂ O ₂ = 1:10. The scheme of the column is shown in Figure 1. H ₂ O ₂ (φ _ν = 3 g/min) enters the system with the help of a high-pressure pump at the top of the column, while TBU (^ = 0.3 g/min) is introduced into the column at the bottom. The peroxide phase is fed to separator S2 at the bottom of the column, where H ₂ O ₂ and TBU are separated by centrifugation, and the peroxide is collected in separator S3. Total organic carbon - TOC in ppm is measured in the peroxide phase. The experiments lasted 180 min. The beneficial effect of H ₂ O ₂ extraction is achieved after only 60 minutes. By extending the cleaning time, we do not achieve lower TOC values at the outlet. Pure TBU was shown to partially purify hydrogen peroxide to a TOC of approx. 100 ppm.

7. Implementation example - purification of H ₂ O ₂ with TBU

Extraction of H ₂ O ₂ (TOC= 550 ppm) with TBU. First, we carried out preliminary studies of H ₂ O ₂ extraction with TBU in a column in the _ratio TBU:H ₂ O ₂ = 1: ₁₀₀ . _ν = 3 g/min) while TBU = 0.03 g/min) is introduced into the column at the bottom. The peroxide phase is led to the separator S2 at the bottom of the column, where H ₂ O ₂ and TBU are separated by centrifugation, the peroxide is collected in the separator S3. Total organic carbon - TOC in ppm is measured in the peroxide phase. The experiments lasted 180 min. The beneficial effect of H ₂ O ₂ extraction is achieved after only 60 minutes. By extending the cleaning time, we do not achieve lower TOC values at the outlet. Pure TBU was shown to partially purify hydrogen peroxide to a TOC of approx. 70 ppm.

8. Implementation example - purification of H ₂ O ₂ with a combination of scCO ₂ and TBU

The subject of the invention is the extraction of H ₂ O ₂ in a combination of scCO ₂ and TBU solvents. The experiment was carried out in a column (Figure 1) at operating temperature (30 °C - 60 °C) and pressure (100 bar -150 bar). First, we warmed the system up to operating temperature. Then we established the pressure in the system by introducing superheated scCO ₂ into the system. When we reached constant operating conditions, we started pumping TBU and H ₂ O ₂ .

At the top, with the help of a high-pressure pump, H ₂ O ₂ peroxide flow φ _ν = 3 g/min was introduced into the column, while at the bottom of the column superheated scCO ₂ and TBU entered (φ _ν1 = 3 g/min). The TBU:H ₂ O ₂ ratio was 1:1. Experimental conditions were kept constant throughout. S/F was 20 kg/kg. The experiment was carried out for 180 min. The impurities were fed to the separator Sl at the top of the column. While H ₂ O ₂ was collected in separator S2, it was sent to a centrifuge, where TBU (supernatant) and H ₂ O ₂ (lower aqueous phase) separate from each other, peroxide is collected in separator S3. The product is purified hydrogen peroxide. Purified H ₂ O ₂ was analyzed on a TOC Carbon Analyzer, Shimatsu. Total organic carbon was determined and the results were given as TOC in ppm. Under the given conditions, hydrogen peroxide is purified with TBU in combination with scCO ₂ to a TOC of approx. 30 ppm.

9. Implementation example - purification of H ₂ O ₂ with a combination of scCO ₂ and TBU

The subject of the invention is the extraction of H ₂ O ₂ in a combination of scCO ₂ and TBU. The experiment was carried out in a column (Figure 1) at operating temperature (60 °C - 100 °C) and pressure (100 bar - 150 bar). First, we warmed the system up to operating temperature. Then we established the pressure in the system by introducing superheated scCO ₂ into the system. When we reached constant operating conditions, we started pumping TBU and H ₂ O ₂ .

At the top, with the help of a high-pressure pump, H ₂ O ₂ flow of peroxide φ _ν = 3 g/min was introduced into the column, while at the bottom of the column superheated scCO ₂ and TBU entered (φ _νί = 0.3 g/min). The TBU:H ₂ O ₂ ratio was 1:10. Experimental conditions were kept constant throughout. S/F was 20 kg/kg. The experiment was carried out for 180 min. The impurities were fed to the separator Sl at the top of the column. While H2O2 was collected in separator S2, it was sent to a centrifuge, where TBU (supernatant) and H ₂ O ₂ (lower - aqueous phase) separate from each other, purified peroxide is collected in separator S3. The product is purified hydrogen peroxide. Purified H ₂ O ₂ was analyzed on a TOC Carbon Analyzer, Shimatsu. Total organic carbon was determined and the results were given as TOC in ppm. Under the given conditions, hydrogen peroxide is purified with TBU in combination with scCO ₂ to a TOC of approx. 25 ppm.

10. Implementation example - purification of H ₂ O ₂ with a combination of scCO ₂ and TBU

The subject of the invention is the extraction of H ₂ O ₂ in a combination of scCO ₂ and TBU. The experiment was carried out in a column (Figure 1) at operating temperature (30 °C - 100 °C) and pressure (100 bar - 150 bar). First of all, we heat the system to operating temperature. Then we established the pressure in the system by introducing superheated scCO ₂ into the system. When we reached constant operating conditions, we started pumping TBU and H ₂ O ₂ .

At the top, with the help of a high-pressure pump, H ₂ O ₂ peroxide flow φ _ν =3 g/min was introduced into the column, while at the bottom of the column superheated scCO ₂ and TBU entered (φ _ν1 = 0.03 g/min). The TBU:H ₂ O ₂ ratio was 1:100. Experimental conditions were kept constant throughout. S/F was 20 kg/kg. The experiment was carried out for 180 min. The impurities were fed to the separator Sl at the top of the column. While H2O2 was collected in separator S2, it was sent to a centrifuge, where TBU (supernatant) and H ₂ O ₂ (lower - aqueous phase) separate from each other, purified peroxide is collected in separator S3. The product is purified hydrogen peroxide. Purified H ₂ O ₂ was analyzed on a TOC Carbon Analyzer, Shimatsu. Total organic carbon was determined and the results were given as TOC in ppm. Under the given conditions, hydrogen peroxide is purified with TBU in combination with scCO ₂ to a TOC of approx. 20 ppm.

We proved that TOC values in purified H ₂ O ₂ are further reduced if a combination of both scCO ₂ and TBU solvents is used for purification.

The high-pressure continuous cleaning process of H ₂ O ₂ with scCO ₂ in combination with TBU is more efficient than using only TBU for cleaning.

The advantages of the invention are:

a process with fewer operations that consume less energy and less raw materials,

- the product is significantly cleaner than the incoming peroxide,

- in a relatively short time we achieve a reduction of TOC by more than half, low cleaning temperature,

- due to complete separation, CO ₂ and TBU used for cleaning can be reused.

The process according to the invention represents an alternative to all conventional H ₂ O ₂ purification processes.

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Claims (6)

PATENT CLAIMS 1. Hydrogen peroxide purification process, characterized in that the process takes place at a temperature in the range between 10 °C and 100 °C and at a pressure in the range between 50 bar and 500 bar, wherein the reagent is a combination of supercritical CO ₂ - scCO ₂ and tetrabutyl urea - TBU, whereby hydrogen peroxide with an impurity content below 50 ppm is obtained. 2. The process according to claim 1, characterized in that the process takes place at a temperature in the range between 30 °C and 60 °C and at a pressure in the range between 100 bar and 500 bar. 3. The method according to claim 1 and 2, characterized in that the TBU content in scCO ₂ is between 0.lmas. % to 80 wt. %, and the ratio of TBU/scCO ₂ to H ₂ O ₂ is between 0.1 to 10. 4. The process according to claims 1 to 3, characterized by the fact that the ratio of hydrogen peroxide to scCO ₂ , i.e. S/F, is from 5 kg/kg to 30 kg/kg. 5. The method according to claims 1 to 3, characterized in that it includes the following steps: - preheating of the reactor (R) to T between 10 and 100 degrees; simultaneous introduction of CO ₂ from the tank (T2) and tetrabutyl urea from the tank (T3) at a pressure between 50 and 500 bar into the reactor (R), whereby both reagents are led via a high-pressure pump (HP2) to the preheater (P) and then to reactor (R), introduction of peroxide from the tank (Tl) via the HPLC pump (HP1) into the reactor (R), during which the extraction of the peroxide takes place with a combination of supercritical CO ₂ and tetrabutyl urea; - collection and management of impurities, which occurred during the extraction, in the separator (S1), and collection and management of peroxide in the separator (S2); centrifuging TBU and peroxide on a centrifuge in the separator (S2) and leading the purified peroxide to the separator (S3); recycling the CO ₂ in the separator (S1), where the impurities in the separator (S4) are removed and the CO ₂ is cooled by the cooling system (H), and the CO ₂ is fed back to the high pressure pump (HP2). 6. The method according to claim 5, characterized in that the reactor (R) is a counter-flow column, a co-flow column or a batch reactor.