Process for the industrial production of high purity hydrogen peroxide

Process for the industrial production of hyperpure hydrogen peroxide also having high titre up to 60-70% by weight characterized in that the hydrogen peroxide produced in an industrial plant is directly fed to a purification unit, being part of the same production plant, in which the inverted osmosis, separation of the the high purity permeate flow and direct recycle of the concentrated flow to the production plant, are carried out.

The present invention relates to an industrial process for producing
 hyperpure hydrogen peroxide also having titre up to about 60-70% by
 weight, to be used in electronic, pharmaceutical and food industries.
 Specifically it is used in the electronic field in the semiconductor
 industry wherein H.sub.2 O.sub.2 electronic grade is required. The
 presence of impurities, such as ions, in the commercial hydrogen peroxide
 requires purification processes so that this product can be used in said
 industry.
 It is well known that hydrogen peroxide as all peroxides requires a
 precaution series with regard to its industrial production, storage and
 transport. The safety of these operations is a must on an industrial and
 commercial scale. An essential characteristic of the commercial hydrogen
 peroxide is the persistence in the long term of the peroxidic oxygen
 (active oxygen) content. This quality issue is conventionally
 characterized as thermal stability, for example by the ISO 7161 test
 (titre loss after 16 hours at 96.degree. C.).
 However the correlation of hydrogen peroxide thermal stability with its
 purity is not univocal, as the influence of the various impurities, in
 terms of stability decay, is different and said influence changes also in
 connection with the distribution of the impurities in their complex.
 The thermal stability of the industrial scale hydrogen peroxide is by
 itself an issue, both for the big volumes of product involved and the
 importance of the invested capitals, and for the safety warranties
 required for logistic and transport purposes. This issue becomes much more
 critical when H.sub.2 O.sub.2 titre reaches values up to about 60-70% by
 weight.
 The chemical industry solves this problem as follows: on one side, by the
 careful selection of the technical materials in contact with hydrogen
 peroxide--the production plants are made with aluminum or stainless steel;
 the storage tanks with stainless steel or with special plastic
 materials--; on the other side, by adding to hydrogen peroxide specific
 chemical products which are able to improve the thermal stability thereof
 also by the inhibition of chemical agents able to catalyze any product
 decomposition reactions.
 Practically to obtain hyperpure hydrogen peroxide it is necessary to start
 from commercial stabilized hydrogen peroxide and to process it by means of
 extreme purification processes to remove the impurities which are not
 acceptable in the indicated applications, for example in the electronic
 industry.
 The purification processes of the hydrogen peroxide for the removal of
 various polluting agents are known in the art. However all the known prior
 art purification processes are carried out in a small scale and the output
 in purified product is very limited. The ratio of the output product with
 respect to the input is very low, well below 20%, in the process of
 reverse osmosis of the prior art.
 All these processes use as starting material commercial grade stabilized
 H.sub.2 O.sub.2 (see U.S. Pat. No. 4,879,043).
 To reach a higher purity level, that is necessary for high purity
 applications, it is necessary to retreat the purified product. The
 disadvantage is that the yield in purified product is even lower. From the
 industrial point of view this is a great disadvantage.
 In particular see the patents having as an object the treatment of hydrogen
 peroxide by reverse osmosis, U.S. Pat. No. 4,525,265; U.S. Pat. No.
 4,879,043; the patents relating to the purification of hydrogen peroxide
 by treatment with ions exchange resins, WO 92/06918; DE 4,214,075; the
 patents describing the purification processes of hydrogen peroxide which
 are carried out by mixed techniques JP 7,109,109; U.S. Pat. No. 4,985,228;
 EP 626,342; DE 4,222,109.
 The combination of different indicated techniques, necessary in order to
 obtain high purity hydrogen peroxide which is therefore free from all the
 polluting agents, until the analytical detectability, must fully comply
 with operating safety criteria. This safety is however compromised by the
 lack of the chemical stabilizers of the product. Obviously the relevance
 of this problem increases with the production scale. Moreover, this
 problem becomes more critical as the concentration of the produced
 hydrogen peroxide reaches about 60-70% titre.
 Therefore the obtainment of hydrogen peroxide at increasing purity levels
 in industrial amounts is an open technological problem. The more, when its
 concentration is as high as about 60 to 70% titre.
 Moreover another drawback of the processes of the art is that the purified
 product yields are not high and the processing duration of the ions
 exchange resins is very short. Besides, the risk due to a prolonged use of
 said resins is very high. Moreover the amount of hydrogen peroxide
 containing impurities which requires specific treatments for its disposal
 is considerable; this requires treatment plants of remarkable sizes with
 consequent increase of the purification costs.
 It was felt the need to have available an industrial process to produce
 hyperpure hydrogen peroxide also having high concentration, up to about
 60-70% by weight (titre), which neither implies risks from the safety
 point of view nor implies the above mentioned disadvantages.
 The Applicant has surprisingly and unexpectedly found that it is possible
 to obtain on industrial scale hydrogen peroxide also at high concentration
 up to about 60-70% by weight with the purity levels required by the most
 sophisticated applications with the process described hereinafter.
 An object of the present invention is an industrial process for the
 production of hyperpure hydrogen peroxide also at high concentration, up
 to about 60-70% by weight, characterized in that the hydrogen peroxide
 produced in an industrial plant, and used as such without addition of any
 stabilizing agent, also at high concentration up to about 60-70% by weight
 is directly fed to a purification unit, being part of the same production
 plant, in which the reverse osmosis, separation of the high purity
 permeate flow and direct recycle of the concentrated flow to the
 production plant, are carried out.
 The osmosis is carried out in one or more steps in series or in parallel,
 with direct recycle of the concentrated flow to the production plant of
 the hydrogen peroxide, preferably to the final distillation unit. The
 membranes used to carry out the reverse osmosis are based on polyamides,
 polypiperazinamides, polyacrylonitrile and polysulphones.
 Preferably the purification process of the invention comprises also a
 treatment unit based on ions exchange resins for the above mentioned
 permeate, in order to obtain hydrogen peroxide with even higher purity
 levels. It has been indeed surprisingly found that the product coming out
 from the osmosis units has very high stability characteristics and can be
 further treated as hereabove indicated with the utmost safety.
 If desired, one or more units charged with ions exchange resins in series
 or in parallel can be used.
 The ions exchange resins are preferably of strong cationic type. Amberlite
 200C and Amberjet 1500H by Rohm & Haas can for example be mentioned.
 If desired, the process of the invention can comprise
 ultrafiltering/nanofiltering units to remove the particles that may be
 possibly present in the hydrogen peroxide. This step is generally inserted
 before the reverse osmosis unit and optionally also after the osmosis unit
 or the treatment with resin.
 Also for the ultrafiltering one or more units in series or in parallel can
 be used.
 By the process of the invention it has been achieved the possibility to
 integrate the purification unit with the hydrogen proxide industrial
 producing units, in the full compliance with the industrial fixed criteria
 of the risk control.
 Thus there are no scale limitations in the production of hyperpure hydrogen
 peroxide with respect to the current production of technical grade
 hydrogen peroxide. This is a remarkable advantage of the process of the
 invention in comparison with the processes of the art since it allows to
 solve the economic conflicts in their whole.
 It has been found that by the invention process the absence of chemical
 additives acting as stabilizers not only does not compromise the operating
 safety or the stability of the obtained product (TEST ISO 7161), but it
 also allows to obtain the desired purity levels with very good economic
 efficiency, since product purgings are not necessary, the concentrated
 flow coming from the osmosis unit being directly reintegrated in the
 production cycle.
 In the invention process the absence of massive polluting agents
 (stabilizers) in the crude product fed to the purification line comprising
 the reverse osmosis units, and optionally the units of the treatment with
 resins, optionally interposing an ultrafiltering/nanofiltering unit,
 allows to obtain the best desired purity levels in an economic and safe
 way. It has indeed been found that neither the reverse osmosis units are
 deactivated, nor depositions of impurities able to destabilize the
 hydrogen peroxide occur on the ionic eschange resins, nor agents external
 to the industrial production process of hydrogen peroxide are introduced
 in the production cycle, nor external polluting agents come into contact
 with the product which can be treated in line, in closed circuits. This
 represents a further advantage in comparison with the processes of the art
 and allows to obtain higher permeate yields compared with the prior art
 processes.
 The intrinsic safety of the purification process of the invention allows
 the integration thereof in the hydrogen peroxide industrial production
 plants, without increasing their total operating risk. The Applicant has
 surprisingly found that this safety is maintained also when H.sub.2
 O.sub.2 having high titre, for example up to about 60-70% by weight, is
 processed.
 This fact, together with the high yields resulting from the absence of
 purgings in the integrated cycle, makes the invention process particularly
 advantageous from the economic point of view.

The examples reported hereinafter have the only purpose to illustrate,
 without anyway limiting it, the process object of the present invention.
 EXAMPLE 1
 A 650 l/h flow of technical grade Hydrogen Peroxide, (not containing
 stabilizing agent) of industrial quality as shown in the analysis in Table
 1, column 1, extracted from a continuous distillation column, was
 uninterruptedly fed for 5 days to a purification unit formed by a
 filtering cartridge (ultrafiltering unit) and by a reverse osmosis
 modulus, operated at a pressure of 20 bar and at the temperature of
 20.degree. C.
 A 350 l/h flow of purified Hydrogen Peroxide was obtained, of average
 quality as shown by the analysis in Table 1, column 2, and a complementary
 flow of 300 l/h of crude Hydrogen Peroxide was recycled as such, directly
 to the continuous distillation unit.
 EXAMPLE 2
 A 650 l/h flow of crude Hydrogen Peroxide of Example 1 was uninterruptedly
 fed for 10 days to a purification unit formed by a couple of reverse
 osmosis moduli, placed in series, by operating at a pressure of 20 bar and
 at the temperature of 25.degree. C.
 A 200 l/h flow of purified Hydrogen Peroxide was obtained, of average
 quality as shown by the analysis in Table 1, column 3, and a complementary
 flow of 450 l/h of crude Hydrogen Peroxide was recycled as such, directly
 to the continuous distillation unit.
 EXAMPLE 3
 A 60 l/h flow of purified Hydrogen Peroxide of Example 2 was
 uninterruptedly fed for 24 hours to a purification unit constituted by a
 strong cationic resin Amberjet 1.500H dispersed bed, in acidic form, with
 a 300 h.sup.-1 space speed, and operated at atmospheric pressure and at
 the temperature of 5.degree. C., followed by a nanofiltering unit.
 A 35 l/h flow of purified Hydrogen Peroxide was obtained, of average
 quality as shown by the analysis in Table 1, column 4.
 TABLE 1
 column 1 column 2 column 3 column 4
 titre, % w/w 35.1 35.1 35.1 35.1
 stability
 ISO 7161 4 0.3 0.05 0.05
 pH 3.5 3.5 3.5 3.5
 TOC (ppm) 170 16 8
 Al (ppb) 450 11 1.2 0.50
 Cr (ppb) 6 &lt;0.5 0.14 0.08
 Mn (ppb) 0.02 0.01
 Co (ppb) 0.01 0.01
 Ni (ppb) 0.17 0.04
 Cu (ppb) 0.43 0.04
 Zn (ppb) 0.57 0.08
 As (ppb) 0.01 0.01
 Sn (ppb) 0.01 0.01
 Mo (ppb) 0.01 0.01
 W (ppb) 0.23 0.02
 Cd (ppb) 0.01 0.01
 Bi (ppb) 0.01 0.01
 Pb (ppb) 0.69 0.01
 Ti (ppb) 0.56 0.03
 Fe (ppb) 10 &lt;0.5 0.75 0.09
 Mg (ppb) 0.88 0.08
 Ca (ppb) &lt;50 3.0 0.09
 Sr (ppb) 0.57 0.01
 Ba (ppb) 0.2 0.02
 Na (ppb) 48 &lt;10 4.1 0.07
 K (ppb) 2.1 0.08
 PO.sub.4 (ppm) 7 &lt;0.1 &lt;0.05 &lt;0.05
 P.sub.2 O.sub.7 (ppm) &lt;0.05 &lt;0.05
 SO.sub.4 (ppm) &lt;0.1 &lt;0.05 &lt;0.05
 Cl (ppm) 0.5 &lt;0.1 &lt;0.05 &lt;0.05
 NO.sub.3 (ppm) 3 &lt;0.1 &lt;0.05 &lt;0.05
 EXAMPLE 4
 A 1900 l/h flow of hydrogen peroxide (not containing stabilizing agent)
 having a 59.8% w/w titre, of industrial quality (sodium ion content of
 2150 ppb) extracted from a continuous distillation column, was
 uninterruptedly fed for 6 days to a purification unit consisting of a
 reverse osmosis unit, constituted by a spiral wound membrane of composite
 polyamide (8040-HSY-SWC1 model by Hydranautics), operated at 40 bar
 pressure and at the temperature of 20.degree. C.
 A 900 Kg/h flow of purified hydrogen peroxide, having a 59.8% titre, of
 average quality as shown by the analysis in Table 2, column 1, was
 obtained and a complementary 1000 l/h flow of crude hydrogen peroxide was
 recycled as such, directly to the distillation unit.
 EXAMPLE 5
 A 2300 l/h flow of purified hydrogen peroxide of Example 4 having a 59.8%
 w/w titre, of average quality as shown by the analysis in Table 2, column
 1, was uninterruptedly fed for 3 days to a purification unit formed by a
 filtering cartridge (ultrafiltering unit) and by a reverse osmosis unit of
 Example 4, working at 40 bar pressure and at the temperature of 20.degree.
 C.
 A 1300 l/h flow of purified hydrogen peroxide, having a 59.8% titre of
 average quality as shown by the analysis in Table 2, column 2, was
 obtained and a complementary 1000 l/h flow of crude hydrogen peroxide was
 recycled as such, directly to the distillation unit.
 EXAMPLE 6
 A 2000 kg/h flow of hydrogen peroxide having a 69.9% titre, (not containing
 stabilizing agent) of industrial quality (sodium ion content of 2150 ppb)
 was uninterruptedly fed for 3 days to the purification unit of Example 5,
 by operating at a 20 bar pressure and at the temperature of 20.degree. C.
 A 950 l/h flow of purified hydrogen peroxide, having a 69.9% titre of
 average quality as shown by the analysis in Table 2, column 3, was
 obtained and a complementary 1050 l/h flow of crude hydrogen peroxide was
 recycled as such, directly to the industrial distillation unit.
 TABLE 2
 column 1 column 2 column 3
 Titre (% w/w) 59.8 59.8 69.9
 Total carbon (ppm) 14 6 16
 Chlorides (ppb) 55 &lt;10 62
 Nitrates (ppb) 200 85 225
 Phosphates (ppb) &lt;50 &lt;10 &lt;50
 Sulphates (ppb) &lt;50 &lt;10 &lt;50
 Arsenic (ppb) &lt;5 &lt;1 &lt;5
 Aluminum (ppb) &lt;5 &lt;1 &lt;5
 Barium (ppb) &lt;5 &lt;1 &lt;5
 Berillium (ppb) &lt;5 &lt;1 &lt;5
 Bismuth (ppb) &lt;5 &lt;1 &lt;5
 Cadmium (ppb) &lt;5 &lt;1 &lt;5
 Calcium (ppb) &lt;10 &lt;1 &lt;10
 Chromium (ppb) &lt;5 &lt;1 &lt;5
 Cobalt (ppb) &lt;5 &lt;1 &lt;5
 Copper (ppb) &lt;5 &lt;1 &lt;5
 Gallium (ppb) &lt;5 &lt;1 &lt;5
 Iron (ppb) &lt;5 &lt;1 &lt;5
 Magnesium (ppb) &lt;5 &lt;1 &lt;5
 Manganese (ppb) &lt;5 &lt;1 &lt;5
 Molibdenum (ppb) &lt;5 &lt;1 &lt;5
 Nickel (ppb) &lt;5 &lt;1 &lt;5
 Lead (ppb) &lt;5 &lt;1 &lt;5
 Silver (ppb) &lt;5 &lt;1 &lt;5
 Sodium (ppb) 53 &lt;5 66
 Strontium (ppb) &lt;5 &lt;1 &lt;5
 Tallium (ppb) &lt;5 &lt;1 &lt;5
 Tin (ppb) &lt;5 &lt;1 &lt;5
 Vanadium (ppb) &lt;5 &lt;1 &lt;5
 Zinc (ppb) &lt;5 &lt;1 &lt;5