Process for manufacturing a purified aqueous hydrogen peroxide solution

Abstract

Process for manufacturing a purified aqueous hydrogen peroxide solution, in which a crude aqueous hydrogen peroxide solution is subjected to a washing operation with at least one organic solvent, and wherein an organophosphorus chelating agent is added to the organic solvent.

Claims

1. A process for manufacturing a purified aqueous hydrogen peroxide solution, comprising: washing a crude aqueous hydrogen peroxide solution with a mixture of at least one organic solvent and an organophosphorus chelating agent, wherein the crude aqueous hydrogen peroxide solution is made by auto-oxidation of at least one alkylanthraquinone in a working solution comprising at least one organic solvent and the at least one alkylanthraquinone; wherein the organic solvent used for the washing step is not part of the working solution and is not recycled into it.

2. The process according to claim 1, wherein the at least one organic solvent used in the washing is chosen so that it improves the metal extraction by the organophosphorus chelating agent.

3. The process according to claim 2, wherein the at least one organic solvent comprises an organophosphorus compound different from the organophosphorus chelating agent.

4. The process according to claim 3, wherein the organophosphorus chelating agent is di-(2-ethylhexyl) phosphoric acid and the at least one organic solvent comprises trioctylphosphate or triethylhexylphosphate.

5. A process for manufacturing propylene oxide (1,2-epoxypropane) by reaction of propylene with hydrogen peroxide that comprises hydrogen peroxide washed by a process according to claim 1.

6. The process for manufacturing propylene oxide (1,2-epoxypropane) according to claim 5, wherein the washed hydrogen peroxide is in the form of an aqueous hydrogen peroxide solution containing from 1 to 100 ppb of Al and/or Fe.

7. The process according to claim 6, wherein the aqueous hydrogen peroxide solution contains less than 100 ppb of Cr.

8. The process according to claim 3, wherein the organic solvent used for the washing step comprises an organophosphorus compound chosen from alkyl-phosphates and alkyl-phosphonates.

9. The process of claim 5, wherein the hydrogen peroxide is in the form of an aqueous hydrogen peroxide solution that comprises less than 100 ppb of Al and/or Fe.

10. The process according to claim 5, wherein the hydrogen peroxide is in the form of an aqueous hydrogen peroxide solution that comprises less than 100 ppb of Cr.

11. The process of claim 6, wherein the aqueous hydrogen peroxide solution comprises from 10 to 100 ppb of Al and/or Fe.

12. The process according to claim 6, wherein the aqueous hydrogen peroxide solution contains from 1 to 100 ppb of Cr.

13. The process according to claim 6, wherein the aqueous hydrogen peroxide solution contains from 10 to 100 ppb of Cr.

14. The process according to claim 3, wherein the organophosphorus chelating agent is di-(2-ethylhexyl) phosphoric acid and the at least one organic solvent comprises trialkylphosphine oxides.

Description

(1) The present invention is illustrated in a non limitative way by the Examples below and FIGS. 1 to 3 attached which relate to preferred embodiments thereof.

(2) FIG. 1 is schematic diagram of the apparatus (installation) used for the continuous trial of Example 7.

(3) FIG. 2 shows the evolution of aluminium and iron content in the aqueous phase at the outlet of this installation.

(4) FIG. 3 shows the buildup of aluminium and iron in the organic phase inside said installation.

EXAMPLES 1 TO 4

(5) DEHPA has been tested as a chelant to remove Al and Fe from a crude H2O2 solution having a peroxide concentration of 40% and the following metal content: Al=220 ppb Fe=110 ppb

Example 1: pH Optimization

(6) A sample of hydrogen peroxide at 40% concentration is treated either with a nitric acid solution or with sodium hydroxide solution to obtain the desired pH. Then the hydrogen peroxide is mixed with the organic solution containing the solvent and the chelating agent in a plastic decanting funnel. The funnel was then shaken during 30 min and let to decant until a good separation is obtained between the organic and the aqueous phases. The treated hydrogen peroxide was recovered and analyzed for metal concentration by ICP. The ratio peroxide on organic phase (TOP+DEHPA) was set equal to 5.0. The amount of DEHPA in TOP was set equal to 2% by weight.

(7) The results obtained are shown in table 1 below.

(8) TABLE-US-00001 TABLE 1 P in Al in Fe in H2O2 Al Fe H2O2 H2O2 crude removed removed pH crude ppb crude ppb ppm (%) (%) 180 24 8.3 5 76 2.0 170 17 12 26 85 2.5 150 14 20 35 87 3.0 140 26 36 36 76 1.5 150 54 77 35 55 4.0 180 74 81 22 33 4.5 180 80 83 22 27
These tests show that: the optimum pH range for Al and Fe removal is between 2.0 and 2.5 which is close to the natural pH of crude peroxide when the pH increases (especially above 3.5), the chelant (complexing agent) has a tendency to dissolve in the hydrogen peroxide as can be seen by the evolution of the P content.

Example 2: Optimization of the Ratio Peroxide/Organic and Amount of DEHPA

(9) The same conditions as in Example 1 were used except that the pH was not adjusted before the test.

(10) The results obtained are shown in table 2 below.

(11) TABLE-US-00002 TABLE 2 Al in Fe in P in Al Fe pH H2O2/ DEHPA H2O2 H2O2 H2O2 re- re- of TOP in TOP crude crude crude moved moved H2O2 ratio (%) ppb ppb ppm (%) (%) 2 1 0 220 46 11 4 58 2 1 2 120 5 15 48 95 2 1 5 41 <5 25 82 >95 2 5 0 200 43 10 13 61 2 5 2 170 17 12 26 85 2 5 5 66 <5 16 71 >95 2 10 0 200 42 10 13 62 2 10 2 180 18 12 22 84 2 10 5 120 <5 12 48 >95

(12) These tests show that the optimum metal removal is obtained with a low ratio peroxide to organic phase (1 to 1) and with a concentration of DEHPA of 5% by weight in TOP.

Example 3: Influence of Solvent: Solvesso?/DiBC Compared to TOP

(13) As the solvent combination Solvesso?150/DiBC is often used on crude H2O2 production sites, it was interesting to check the efficiency of DEHPA in this type of solvent.

(14) The tests performed at lab scale (again using the same procedure as in the previous examples) are shown in Table 3 below.

(15) TABLE-US-00003 TABLE 3 DEHPA in Al in Fe in P in Al Fe pH H2O2/ S150/ H2O2 H2O2 H2O2 re- re- of solvent DBC crude crude crude moved moved H2O2 ratio (%) ppb ppb ppm (%) (%) 2 1 1 180 47 11 22 57 3 1 1 190 50 14 17 55 4 1 1 190 33 15 17 70 5 1 1 220 13 27 4 88 6 1 1 12 12 80 95 89

(16) These results indicate two main different trends in comparison with TOP the optimum pH is much higher (close to 6.0) and might lead to a stability issue for hydrogen peroxide the amount of DEHPA required for an optimum removal is lower than the one required for TOP systems (1% instead of 5%).

Example 4: Influence of Complexing Agents: CYANEX? 272 Compared to DEHPA

(17) CYANEX? 272, a phosphonated component with a different structure than DEHPA and having the chemical formula is bis(2,4,4-trimethylpentyl)phosphinic acid (CAS: 83411-71-6) was used again in the same experimental conditions. The comparative tests performed at lab scale are shown in Table 4 below.

(18) TABLE-US-00004 TABLE 4 Al in Fe in P in H2O2/ CYANEX H2O2 H2O2 H2O2 Al Fe TOP in TOP CRUDE CRUDE crude removed removed ratio (%) ppb ppb ppm (%) (%) 1 0 220 46 11 4 58 1 2 160 6 15 30 95 1 5 160 6 18 30 >95 5 0 200 43 10 13 61 5 2 170 12 12 26 89 5 5 160 5 14 30 >95 10 0 200 42 10 13 62 10 2 170 19 11 26 83 10 5 160 9 13 30 >95

(19) These tests show that when using the best conditions optimized for DEHPA (pH=2, Ratio=1 and DEHPA=5%), the Al removal by CYANEX? is limited to 30% instead of 82% for DEHPA.

(20) CYANEX? 272 has however a high efficiency for Fe removal (>95%) and similar to the one obtained with DEHPA.

Examples 5, 6 and 7

(21) A multi-extraction process has been tested to remove Al, Fe and Cr from a crude H2O2 solution having a peroxide concentration of 40% and the following metal content: Al=76 ppb Fe=92 ppb Cr=23 ppb

Example 5: Test at Ambient Temperature

(22) A crude solution of hydrogen peroxide at 40% concentration was mixed with an organic solution containing a mixture of solvents and a chelating agent in a plastic decanting funnel. The organic solution consisted of: 80% w/w of Solvess?150 10% w/w of TOP 10% w/w of DEHPA

(23) The funnel was then shaken during 60 min at ambient temperature and let to decant for 24 hours. The treated hydrogen peroxide was separated from the organic phase, filtered on paper filters (597? followed by 595) and a sample was taken for analysis.

(24) The same sample of hydrogen peroxide was treated 5 times successively with a fresh aliquot of the organic chelating solution. At each step of the process, a sample was taken and analysed for metal concentration by ICP-MS.

(25) The ratio peroxide on organic phase (S150+TOP+DEHPA) was the same at each step and equal to 10.

(26) The results obtained are shown in Table 5 below:

(27) TABLE-US-00005 TABLE 5 ICP analysis Yield of removal Al ?g/kg Fe ?g/kg Cr ?g/kg Al % Fe % Cr % Initial H2O2 76 92 23 extraction 1 5 0.29 16 93.4 99.7 30.4 extraction 2 2 0.07 11 97.4 99.9 52.2 extraction 3 1.5 0.09 8 98.0 99.9 65.2 extraction 4 1.5 0.15 5 98.0 99.8 78.3 extraction 5 1.4 0.08 3.1 98.2 99.9 86.5
These results show that: The extracting process is efficient for Al, Fe and Cr at the natural pH of crude hydrogen peroxide The efficiency of the extracting process goes in the order: Fe>Al>Cr

Example 6: Test at 50? C.

(28) The same procedure as in Example 5 was repeated except that the temperature was set at 50? C. instead of ambient.

(29) The results obtained are shown in Table 6 below:

(30) TABLE-US-00006 TABLE 6 ICP analysis Yield of removal Al ?g/kg Fe ?g/kg Cr ?g/kg Al % Fe % Cr % Initial H2O2 76 92 23 extraction 1 3.8 0.9 6 95.0 99.0 73.9 extraction 2 1.3 0.16 1.3 98.3 99.8 94.3 extraction 3 0.7 0.05 0.5 99.1 99.9 97.8 extraction 4 1.2 0.08 0.22 98.4 99.9 99.0 extraction 5 0.7 <0.05 0.13 99.1 100 99.4
These results show that: The efficiency of the extracting process is higher at 50? C. than at ambient temperature Metal concentrations below 1 ppb in the crude can be achieved after 3 extractions for Al, Fe and Cr After 5 extractions, Fe can be removed completely from the hydrogen peroxide solution.

Example 7: Continuous Extraction Trial

(31) 2 continuous flows of a crude solution of hydrogen peroxide at 40% concentration identical to the one used in Examples 5 and 6 above and of an organic solution containing a mixture of solvents and a chelating agent were mixed together continuously in a heated glass reactor. The organic solution consisted of: 80% w/w of Solvess?150 10% w/w of TOP 10% w/w of DEHPA

(32) The mixture between aqueous and organic phases was then fed continuously in a separating glass column filled with a packing glass in order to separate both phases. That process was then repeated in a second set of identical material. A schematic diagram of the used apparatus (installation) is set out in FIG. 1 attached. The mixture of solvents was permanently recycled inside this installation following a closed circuit. The flows for each solutions were: 50 ml/h for the aqueous hydrogen peroxide solution 100 ml/h for the organic extraction solution

(33) The total amount of organic solution recycled in the system was 1250 ml and the installation was fully kept at 50? C.

(34) Periodically a sample of the aqueous solution was taken at the outlet of the installation and analysed by ICP. The evolution of aluminium and iron content in the aqueous phase at the outlet of the installation is shown in FIG. 2 attached.

(35) Periodically a sample of the organic solution was taken and analysed by ICP-MS. The buildup of aluminium and iron in the organic phase is shown in FIG. 3 attached.

(36) These results show that: An aluminium concentration in the outlet crude can be maintained below 20 ppb for almost 2500 hours of operation. A concentration below 5 ppb of iron in the outlet hydrogen peroxide can be maintained on a long run. 1250 ml of extraction solution allowed purifying 125 l of hydrogen peroxide while maintaining a concentration of aluminium lower than 20 ppb in the crude.

Example 8: Regeneration of Exhausted Chelating Solution

(37) The organic mixture of solvents and chelating agent used in the continuous extraction trial (example 7) has been used to test the regeneration procedure.

(38) During the continuous trial, the inlet and outlet hydrogen peroxide solutions have been analysed periodically by ICP. By integration of these analytical results, the amount of aluminium in the organic solution at the end of the continuous test can be estimated to 10.2 mg/kg.

(39) In a plastic fuel decanter, 100 ml of that organic extracting solution have been mixed for 30 minutes with 100 ml of HNO.sub.3 1 mol/l at ambient temperature and let to decant until a good separation is obtained between both phases.

(40) Then the nitric acid solution was recovered and its aluminium content analysed by ICP. The result obtained was 9.2 mg/kg of aluminium in the nitric phase.

(41) Taking into account the density of hydrogen peroxide, the yield of aluminium regeneration was about:
9.2*100/(10.2*1.15)=78%