EP4594250A1 - A new hydrogen peroxide purification process - Google Patents

Abstract

The present invention describes a novel process for the purification of hydrogen peroxide (H2O2) using a reagent which is a combination of supercritical CO2 (scCO2) and tetra butyl urea (TBU). It is a high-pressure process in a reactor, preferably a counter-current column, where scCO2 in combination with tetra butyl urea (TBU) is used as the medium, i.e. the reagent. TBU is added to the stream together with scCO2 in an appropriate ratio to H2O2. The product obtained is purified hydrogen peroxide. The resulting product is monitored at the effluent for total organic carbon - TOC, which is determined in ppm and is below 50 ppm.

Description

A NEW HYDROGEN PEROXIDE PURIFICATION PROCESS

DESCRIPTION OF THE INVENTON

The invention is based on a novel process for the purification of hydrogen peroxide (H2O2) using supercritical fluid SCCO2 in combination with tetra butyl urea (TBU) as the purification reagent.

The classical purification techniques used for hydrogen peroxide purification are distillation, adsorption, ion exchange, crystallisation, membrane separation. These processes are energy intensive. The proposed hydrogen peroxide purification process offers significant technical advantages, a process with fewer operations, consuming less energy and fewer raw materials. It is a high-pressure process, operating at pressures of 50 to 500 bar and temperatures in the range of 10 to 100 °C. The medium used is scCCh in combination with TBU. In the combination of the two reagents in the stream, TBU is added together with SCCO2 in the appropriate ratio to H2O2. The product obtained is purified hydrogen peroxide. The resulting product is monitored at the effluent for total organic carbon - TOC, which is determined in ppm.

STATE OF THE ART

Various techniques are known for the purification of hydrogen peroxide: distillation [1], adsorption of ionic exchange resins [2-4], recrystallisation, membrane separation [5], As an alternative, SCCO2 can be used to purify H2O2 [6],

Hydrogen peroxide (H2O2) is a slightly acidic, clear and colourless liquid which is completely miscible with water in all proportions. It plays an important role in protecting the human organism against microbes and viruses. It is known worldwide as a powerful environmentally friendly oxidant, which in its purified form is non-toxic and readily decomposes into byproducts [7], Worldwide, hydrogen peroxide is almost exclusively produced by the anthraquinone (AO) process, which is a very energy-intensive process [8], In this process, hydrogen peroxide is formed by the sequential hydrogenation and oxidation of alkyl anthraquinone dissolved in a mixture of organic solvents, followed by the recovery of the product in a liquid-liquid counter-current extraction with water [9], The sub-optimal partition coefficient and organic solvent contamination during the processing of the liquid-liquid extraction requires the further energy-consuming use of purification methods: distillation, adsorption and ion exchange resins, crystallisation, membrane separation. The concentrated, high-purity hydrogen peroxide is then stabilized against unwanted and uncontrolled decomposition by the addition of proprietary stabilizers.

In sustainable development, high-pressure is increasingly used as a process tool. Supercritical fluids can help address the shortcomings of many conventional processing and product manufacturing processes [10], Supercritical fluid extraction (SFE) is an essential method for the large-scale purification of complex liquid or solid substances, such as process waste streams. The main advantage of supercritical fluid-liquid extraction is that the supercritical fluid can be easily removed by lowering the temperature and pressure. The supercritical fluid becomes a gas, and the extracted substance condenses into a liquid or solid.

The ultra-pure hydrogen peroxide solution is prepared by purifying an industrial hydrogen peroxide solution, which is generally produced using anthraquinone. The process consists of successive hydrogenation, filtration oxidation and liquid/liquid extraction steps. Several ancillary processes are also required. The industrial hydrogen peroxide solution contains specific amounts of organic, inorganic, and metallic compounds. Organic impurities in hydrogen peroxide solutions are introduced by working solvents and soluble degradation products, including tributyl phosphate aromatics (TOP), anthraquinone, and its derivatives [1],

Many treatment technologies have been developed to remove the above impurities in the hydrogen peroxide solution and to reduce the total organic carbon (TOC) content. Currently, distillation [1], adsorption and ion exchange technology [2-4], recrystallisation [11], supercritical extraction [6], flocculation technology, combination reagent technology and membrane separation [5], such as microfiltration, ultrafiltration and reverse osmosis, are in industrial practice. Crystallisation, flocculation and addition of staining agents are additional technologies.

Currently, the preparation of ultrapure hydrogen peroxide is carried out first by distillation, followed by a combination of different membrane separation techniques or ion exchange processes and adsorption [12], Distillation is a reliable and simple method on an industrial scale. However, it involves the use of an inert column made of fluoropolymers (poor thermal conductors), which increases energy consumption, while at the same time the purity of the distilled hydrogen peroxide is not high enough [13],

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

Membrane technologies (reverse osmosis) are emerging as the preferred option for ultraefficient purification according to environmental criteria. Secondary chemicals are not required and therefore there are no waste streams. Nevertheless, ultra-efficient hydrogen peroxide purification can be considered as a very challenging process, as the strong oxidation 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 industrial aqueous H2O2 solution, to produce ultrapure H2O2. The results showed that the capacity of activated carbon to remove organic impurities from aqueous hydrogen peroxide solutions is mainly related to the microspore structure.

Rueda et al. [16] achieved the direct synthesis of hydrogen peroxide from H2 and O2 with water as solvent in a semi-continuous stirred reactor system. This process represents a greener alternative to the traditional process using anthraquinone or direct synthesis using organic solvents.

As an alternative for the purification of hydrogen peroxide, scCCh can be used but there is very little research in this field. Blanco-Brieva et al. [17] report remarkable results when synthesis is carried out at a high-pressure of 9,5 MPa in metabolic medium. Hancu et al. [18] used compounds that functionalise a number of amino and hydroxyl-AOs to promote mixing with CO2 at lower pressures, thereby increasing the solubility of CO2. Since very little has been studied in the field of hydrogen peroxide purification with supercritical fluids or with tetra butyl urea, we have undertaken preliminary investigations of hydrogen peroxide purification with supercritical CO2 only and with tetra butyl urea only - implementation examples 1 to 7 - to corroborate our invention. In the case of scCCh cleansing, the TOC has been lowered up to 120 ppm, while TBU has lowered the TOC value up to 70 ppm. This demonstrates that the combination of both reagents, SCCO2 and TBU, is the most effective in hydrogen peroxide purification.

THE SHORTCOMINGS OF EXISTING SOLUTIONS

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

The purification of hydrogen peroxide, where the medium, i.e., the reagent, is scCCh, provides significant technical advantages, a process with fewer operations, consuming less energy and fewer raw materials. All these processes involving SCCO2 have been carried out on a laboratory scale. There is no information on large scale production or purification of hydrogen peroxide that is economical and environmentally friendly.

Research has shown that purification of hydrogen peroxide where the medium, i.e., the reactant, is TBU (TBU extraction) also significantly reduces TOC values relative to the input H2O2 solution (raw H2O2). Therefore, TBU emerges as an alternative for H2O2 purification.

Hydrogen peroxide purification, where the medium, i.e., the reagent, is a combination of SCCO2 and TBU, further reduces the TOC value of the peroxide.

DETAILED DESCRIPTION

The working solution used to prepare hydrogen peroxide contains anthraquinones and its derivatives. These by-products contain a very complex mixture of degradation products which cannot actively participate in the production of hydrogen peroxide as they cause the working solution to become more viscous and denser. The degradation products must be removed from the working solution to prevent an increase in the density and viscosity of the working solution [19], A wide variety of organic substances are present in the crude hydrogen peroxide, such as organic solvents, quinones dissolved in organic solvents, water-soluble degradation products of solvents, in particular the sextate, emulsified solvents. Due to this variety of composition, not all organic substances can be removed by extraction alone, and not the water-soluble substances. The efficiency of the extraction or purification itself is influenced by the partition coefficient, which depends on the nature of the solvent, the intensity of agitation, the solubility of the extraction solvent in the peroxide phases and the temperature.

The hydrogen peroxide should therefore be properly purified, i.e. the decomposition products (mainly organic solvents) should be removed, thereby lowering the total organic carbon - TOC - content, which is achieved by the process according to the invention.

The invention is described below and illustrated in the figure.

Figure 1 shows the hydrogen peroxide purification scheme in a counter-current column or reactor.

The invention consists essentially in a novel purification-extraction process for hydrogen peroxide (H2O2), wherein the process is a high-pressure process and is carried out in reactor R at a pressure in the range of 50-500 bar and a temperature in the range of 10-100 °C. Preferably, the pressure is in the range of 100-500 bar and the temperature is in the range of 30-60 °C. The medium or reactant used in the process is a supercritical fluid, preferably supercritical CO2 (scCCh), in combination with tetra butyl urea (TBU). TBU is added to the liquid together with scCCh in an appropriate ratio to H2O2, where the TBU content in scCCh is between 0,1 % and 80 % by weight and the TBU/scCCh to H2O2 ratio is between 0,1 and 10. The ratio of hydrogen peroxide to scCCh, i.e. the S/F ratio, ranges from 5 kg/kg to 30 kg/kg.

CO2 is fed from a tank T2 and tetra butyl urea from a tank T3. Both reagents are fed via a high- pressure pump HP2 to a preheater P. Unpurified hydrogen peroxide enters a reactor R from a tank Tl. Impurities from the purification are collected in a separator SI. The purified hydrogen peroxide is led to a centrifuge in a separator S2 where TBU (supernatant) and H2O2 (lower - phase of the purified peroxide) are separated from each other, the resulting product is purified hydrogen peroxide, which is collected in a separator S3. The gaseous CO2 leaving SI is recycled at the end of the process. First, the impurities are removed in a separator S4, then the CO2 is cooled by a cooling system - H and fed back to the high-pressure pump HP2 and then again to the reactor R.

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

The advantage of using a combination of SCCO2 and TBU is that TBU and H2O2 do not mix and can be easily separated by centrifugation. The TBU and SCCO2 used are recirculated.

The hydrogen peroxide purification process therefore involves the following steps: preheating of the reactor R to a temperature T between 10 and 100 degrees; simultaneous introduction of CO2 from the tank T2 and tetra butyl urea from the tank T3 at a pressure of between 50 and 500 bar into the reactor R, both reactants being fed via the high-pressure pump HP2 to the preheat P and then to the reactor R; introduction of peroxide from the tank T1 via the HPLC pump HP1 into the reactor R, where peroxide extraction with a combination of supercritical CO2 and tetra butyl urea is carried out; collection and transfer of the impurities from the extraction to the separator SI, and collection and transfer of the peroxide to the separator S2; centrifugation of TBU and peroxide on a centrifuge in a separator S2 and feeding of purified peroxide to the separator S3; recycling the CO2 in the separator SI, where impurities are removed in the separator S4 and cooling the CO2 with the cooling system H, and feeding the CO2 back to the high- pressure pump HP2.

Preferably, the reactor R, where the hydrogen peroxide (H2O2) purification process is carried out, is a counter-current stainless steel column of 1 m -10 m in length, filled with an inert filler of glass beads of 0,1-1 cm in diameter. The length of the fill is 1-5 m. The 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. CO2 is fed from the tank T2 and tetra butyl urea is fed from the tankT3. Both reactants are fed via a high-pressure pump HP2 to a preheater P. The preheated scCCh and TBU are fed to the bottom of the reactor R so that the TBU content in the scCCh is between 0,1 wt.% and 0,1 wt.%. The crude hydrogen peroxide enters the reactor R from the tank T1 at the top of the reactor R via a HPLC pump HP1. The appropriate flow rates of hydrogen peroxide in the system are determined according to the ratio of scCCh, where the ratio of hydrogen peroxide to scCCh is from 5 kg/kg to 30 kg/kg. The impurities resulting from the purification are collected at the top of the reactor R in the separator SI. The purified hydrogen peroxide is led from the bottom of the reactor R to a centrifuge in the separator S2, where TBU (supernatant) and H2O2 (lower - purified peroxide phase) are separated from each other, the resulting product being purified hydrogen peroxide, which is collected in the separator S3. The gaseous CO2 leaving SI is recycled at the end of the process. First, the impurities are removed in the separator S4, then the CO2 is cooled by the cooling system H and fed back to the high-pressure pump HP2 and then again to the reactor R.

A sample of unpurified and purified hydrogen peroxide is analyzed for total organic carbon using a TOC Carbon Analyser, 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 confluent column or in a batch reactor. In the case of a co-current column, all components (hydrogen peroxide, SCCO2 and TBU) enter the reactor simultaneously at the bottom and exit at the top, whereby the SCCO2 is recycled and the TBU and purified peroxide are separated in a separator. The ratios and flow rates remain the same as for the countercurrent system. In the case of a batch reactor, however, TBU and H2O2 and scCCh under operating P and T are introduced into the batch reactor (high pressure reactor) at the same ratios and pressures and, after the process is complete, the system is depressurized and the H2O2 and TBU phases are separated, the lower phase being the purified hydrogen peroxide phase.

IMPLEMENTATION EXAMPLES

Examples 1-7 are preliminary experiments confirming that the invention involving both reagents, i.e. TBU and SCCO2, in the purification process is the preferred one. 1. Implementation Example - Purification of H2O2 with scCCh

Extraction of H2O2 was caried out in a counter-current column with scCCh solvent. The column scheme is shown in Figure 1. The peroxide phase (TOC = 500 - 600 ppm) was introduced at the top of the column, while SCCO2 entered at the bottom. The column was heated to operating temperature and preheated SCCO2 was introduced into the system using a high-pressure pump. Then hydrogen peroxide was introduced into the system at the top of the column. The appropriate flow rate of hydrogen peroxide into the system was selected accordingly. Supercritical CO2 was continuously introduced in the counter current at the bottom of the column. The ratio of peroxide to SCCO2 (S/F) was 10 kg/kg. The extraction was carried out for 150 min. The impurities resulting from the purification were collected at the top of the column in separator SI, while the purified hydrogen peroxide was collected in the separator at the bottom of column S2 and S3. Finally, purified hydrogen peroxide was obtained, which was measured to have a total carbon content of TOC = 200 ppm.

2. Implementation Example - Purification of H2O2 with SCCO2

Extraction of H2O2 was performed in a counter-current column with SCCO2 solvent. The column scheme is shown in Figure 1. The peroxide phase (TOC = 600 ppm) was introduced at the top of the column, while SCCO2 entered at the bottom. The column was heated to operating temperature and preheated SCCO2 was introduced into the system using a high- pressure pump. Then hydrogen peroxide was introduced into the system at the top of the column. The appropriate flow rate of hydrogen peroxide into the system was selected accordingly. Supercritical CO2 was continuously introduced in the counter current at the bottom of the column. The ratio of peroxide to SCCO2 (S/F) was 6 kg/kg. The extraction was carried out for 100 min. The impurities resulting from the purification were collected at the top of the column in separator SI, while the purified hydrogen peroxide was collected in the separator at the bottom of column S2 and S3. Finally, purified hydrogen peroxide was obtained, which was measured to have a total carbon content of TOC = 160 ppm.

3. Implementation Example - Purification of H2O2 with SCCO2

The extraction of H2O2 was carried out in a counter-current solvent column with SCCO2. The column scheme is shown in Figure 1. The peroxide phase (TOC = 550 ppm) was introduced at the top of the column, while scCCh entered at the bottom. The column was heated to operating temperature and preheated scCCh was introduced into the system using a high- pressure pump. Then hydrogen peroxide was introduced into the system at the top of the column. The appropriate flow rate of hydrogen peroxide into the system was selected accordingly. Supercritical CO2 was continuously introduced in the counter current at the bottom of the column. The peroxide to scCCh (S/F) ratio was 20 kg/kg. The extraction time was 120 min. The impurities resulting from the extraction were collected at the top of the column in separator SI, while the purified hydrogen peroxide was collected in the separator at the bottom of column S2 and S3. Finally, purified hydrogen peroxide was obtained, which was measured to have a total carbon content of TOC = 130 ppm.

4. Implementation Example - Purification of H2O2 with SCCO2

Extraction of osmotically purified H2O2 with SCCO2 solvent was performed. The peroxide phase (TOC = 51 ppm) was introduced at the top of the column while SCCO2 entered at the bottom. The column was heated to operating temperature and preheated SCCO2 was introduced into the system using a high-pressure pump. Then hydrogen peroxide was introduced into the system at the top of the column. The appropriate flow rate of hydrogen peroxide into the system was selected accordingly. Supercritical CO2 was continuously introduced in the counter current at the bottom of the column. The peroxide to scCCh (S/F) ratio was 20 kg/kg. The purge was run for 120 min.

The impurities resulting from the extraction were collected at the top of the column in the SI HPS separator, while the purified hydrogen peroxide was collected in the separator at the bottom of the S2 and S3 columns. In the end, purified hydrogen peroxide was obtained and measured to have a total carbon content of TOC = 100 ppm.

5. Implementation Example - Purification of H2O2 with TBU

Extraction of H2O2 (TOC = 500 ppm) with TBU. Preliminary studies on the extraction of H2O2 with TBU in a TBU:H2O2 = 1:1 column were first carried out. The column schematic is shown in Figure 1. H2O2 (4>v = 3 g/min) enters the system via a high-pressure pump at the top of the column, while TBU (4>v = 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 the H2O2 and TBU are separated by centrifugation and the peroxide is collected in separator S3. The peroxide phase is measured for total organic carbon - TOC in ppm. The experiments were run for 180 min. A favourable effect of H2O2 extraction is achieved after 60 min. Increasing the purification time does not result in lower TOC values in the effluent. It was shown that pure TBU purified the hydrogen peroxide from a TOC of approx. 600 ppm to approx. 120 ppm.

6. Implementation Example - Purification of H2O2 with TBU

Extraction of H2O2 (TOC = 550 ppm) with TBU in a column at TBU:H2O2 = 1:10. The column scheme is shown in Figure 1. H2O2 (4>v = 3 g/min) enters the system via a high-pressure pump at the top of the column while TBU (4>v = 0,3 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 H2O2 and TBU are separated by centrifugation and the peroxide is collected in separator S3. The peroxide phase is measured for total organic carbon - TOC in ppm. The experiments were carried out for 180 min. A favourable effect of H2O2 extraction is achieved after 60 min. Increasing the purification time does not result in lower TOC values in the effluent. The purified TBU was shown to partially purify the hydrogen peroxide to a TOC of approx. 100 ppm.

7. Implementation Example - Purification of H2O2 with TBU

Extraction of H2O2 (TOC = 550 ppm) with TBU in a column at TBU:H2O2 = 1:100. The column scheme is shown in Figure 1. H2O2 (4>v = 3 g/min) enters the system via a high-pressure pump at the top of the column while TBU (4>v = 0,3 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 H2O2 and TBU are separated by centrifugation and the peroxide is collected in separator S3. The peroxide phase is measured for total organic carbon - TOC in ppm. The experiments were carried out for 180 min. A favourable effect of H2O2 extraction is achieved after 180 min. Increasing the purification time does not result in lower TOC values in the effluent. The purified TBU was shown to partially purify the hydrogen peroxide to a TOC of approx. 70 ppm.

8. Implementation Example - H2O2 purification with a combination of SCCO2 and TBU

The subject of the invention is the extraction of H2O2 in a combination of SCCO2 and TBU solvents. The experiment was carried out in a column (Fig. 1) at operating temperature (30 °C - 60 °C) and pressure (100 bar - 150 bar). First, the system was heated to operating temperature. Then the system was pressurised by introducing superheated scCCh into the system. Once constant operating conditions were achieved, we started pumping TBU and H₂O₂.

At the top of the column, a high-pressure pump was used to introduce H2O2 at a peroxide flow rate of 4>v = 3 g/min, while at the bottom of the column superheated SCCO2 and TBU (4>vl = 3 g/min) were introduced. The TBU:H2O2 ratio was 1:1. The experimental conditions were kept constant throughout. The S/F was 20 kg/kg. The experiment was carried out for 180 min. The impurities were fed to separator SI at the top of the column. While H2O2 was collected in separator S2 and led to the centrifuge where TBU (supernant) and H2O2 (lower - aqueous phase) are separated, peroxide is collected in separator S3. The product is purified hydrogen peroxide. The purified H2O2 was analysed on a TOC Carbon Analyser, Shimatzu. Total organic carbon was determined, and the results are given as TOC in ppm. Under the given conditions, TBU in combination with SCCO2 purifies hydrogen peroxide to a TOC of approx. 30 ppm.

9. Implementation Example - H2O2 purification with a combination of SCCO2 and TBU

The subject of the invention is the extraction of H2O2 in a combination of SCCO2 and TBU solvents. The experiment was carried out in a column (Fig. 1) at operating temperature (60 °C

- 100 °C) and pressure (100 bar - 150 bar). First, the system was heated to operating temperature. Then the system was pressurised by introducing superheated scCCh into the system. Once constant operating conditions were achieved, we started pumping TBU and H2O2.

At the top of the column, a high-pressure pump was used to introduce H2O2 at a peroxide flow rate of 4>v = 3 g/min, while at the bottom of the column superheated SCCO2 and TBU (4>vl = 0,3 g/min) were introduced. The TBU:H2O2 ratio was 1:10. The experimental conditions were kept constant throughout. The S/F was 20 kg/kg. The experiment was carried out for 180 min. The impurities were fed to separator SI at the top of the column. The H2O2 was collected in separator S2 and led to a centrifuge where the TBU (supernatant) and H2O2 (lower - aqueous phase) are separated from each other, the peroxide is collected in separator S3. The product is purified hydrogen peroxide. The purified H2O2 was analysed on a TOC Carbon Analyser, Shimatzu. Total organic carbon was determined, and the results are given as TOC in ppm. Under the given conditions, TBU in combination with SCCO2 purifies hydrogen peroxide to a TOC of approx. 25 ppm.

10. Implementation Example - H2O2 purification with a combination of SCCO2 and TBU

The subject of the invention is the extraction of H2O2 in combination with SCCO2 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). The system was first heated to operating temperature. Then the system was pressurised by introducing superheated scCCh into the system. Once constant operating conditions were achieved, we started pumping TBU and H2O2.

At the top of the column, a high-pressure pump was used to introduce H2O2 at a peroxide flow rate of 4>v = 3 g/min, while at the bottom of the column superheated SCCO2 and TBU (4>vl = 0,03 g/min) were introduced. The TBU:H2O2 ratio was 1:100. The experimental conditions were kept constant throughout. The S/F was 20 kg/kg. The experiment was carried out for 180 min. The impurities were fed to separator SI at the top of the column. While H2O2 was collected in separator S2 and led to the centrifuge where TBU (supernant) and H2O2 (lower - aqueous phase) are mutually separated, purified peroxide is collected in separator S3. The product is purified hydrogen peroxide. The purified H2O2 was analysed on a TOC Carbon Analyser, Shimatzu. Total organic carbon was determined, and the results are given as TOC in ppm. Under the given conditions, TBU in combination with SCCO2 purifies hydrogen peroxide to a TOC of approx. 20 ppm.

It has been shown that the TOC in the purified H2O2 is further reduced if a combination of both solvents SCCO2 and TBU is used for purification.

The high-pressure continuous H2O2 purification process with SCCO2 in combination with TBU is more efficient than using TBU alone.

The advantages of the invention are: a process with fewer operations, consuming less energy and fewer raw materials, the product is significantly cleaner than the input peroxide, a reduction of TOC by more than half in a relatively short time, low purification temperature, due to the complete separation, CO2 and TBU used for purification can be reused.

The process according to the invention represents an alternative to all conventional H2O2 purification processes.

REFERENCES

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Claims

PATENT CLAIMS

1. A hydrogen peroxide purification process, characterized in that the process is carried out at a temperature in the range of 10 °C to 100 °C and a pressure in the range of 50 bar to 500 bar, wherein a reactant is a combination of supercritical CO2 - scCOz and tetra butyl urea - TBU, resulting in hydrogen peroxide with an impurity content of less than 50 ppm.

2. The process according to claim 1, characterized in that the process is carried out at a temperature in the range of 30 °C to 60 °C and at a pressure in the range of 100 bar to 500 bar.

3. The process according to claim 1 and 2, characterized in that the TBU content in the SCCO2 is between 0,1 wt.% and 80 wt.% and a TBU/scCCh to H2O2 ratio is between 0,1 and 10.

4. The process according to claims 1 to 3, characterized in that a ratio of hydrogen peroxide to scCO2 - S/F, ranges from 5 kg/kg to 30 kg/kg.

5. The process according to claims 1 to 3, wherein the process including the following steps:

- preheating a reactor (R) to a temperature T between 10 and 100 degrees;

- simultaneous introduction of CO2 from a tank (T2) and tetra butyl urea from a tank (T3) at a pressure of between 50 and 500 bar into the reactor (R), both reactants being directed via a high-pressure pump (HP2) to a preheater (P) and then to the reactor (R);

- introduction of peroxide from a tank (Tl) via a HPLC pump (HP1) into the reactor (R), during which an extraction of the peroxide takes place by a combination of supercritical CO2 and tetra butyl urea;

- collecting and leading of the impurities produced during the extraction into a separator (SI), and collecting and leading of peroxide into a separator (S2);

- centrifugation of TBU and peroxide on a centrifuge in the separator (S2) and leading the purified peroxide to a separator (S3); - recycling the CO2 in the separator (SI), removing impurities in a separator (S4) and cooling the CO2 with a cooling system (H), and feeding the CO2 back to the high-pressure pump (HP2). The process according to claim 5, wherein the reactor (R) is a counter-current column, a confluent column, or a batch reactor.