WO2018203796A1 - A sorbent and a filter - Google Patents

A sorbent and a filter Download PDF

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Publication number
WO2018203796A1
WO2018203796A1 PCT/SE2018/050405 SE2018050405W WO2018203796A1 WO 2018203796 A1 WO2018203796 A1 WO 2018203796A1 SE 2018050405 W SE2018050405 W SE 2018050405W WO 2018203796 A1 WO2018203796 A1 WO 2018203796A1
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Prior art keywords
sorbent
formaldehyde
precipitated silica
polyethylenimine
amorphous precipitated
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PCT/SE2018/050405
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French (fr)
Inventor
Zareh TOPALIAN
Peter Norberg
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Svenska Aerogel AB
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Svenska Aerogel AB
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Filing date
Publication date
Application filed by Svenska Aerogel AB filed Critical Svenska Aerogel AB
Priority to KR1020197035447A priority Critical patent/KR20200003861A/en
Priority to US16/609,376 priority patent/US20200188874A1/en
Priority to CN201880040686.3A priority patent/CN110799265A/en
Priority to EP18794253.7A priority patent/EP3638413A4/en
Publication of WO2018203796A1 publication Critical patent/WO2018203796A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B01J20/262—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon to carbon unsaturated bonds, e.g. obtained by polycondensation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/0027—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with additional separating or treating functions
    • B01D46/0036—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with additional separating or treating functions by adsorption or absorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/72—Organic compounds not provided for in groups B01D53/48 - B01D53/70, e.g. hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/81—Solid phase processes
    • B01D53/82—Solid phase processes with stationary reactants
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
    • B01J20/103—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate comprising silica
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28014—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their form
    • B01J20/28016—Particle form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B01J20/28061—Surface area, e.g. B.E.T specific surface area being in the range 100-500 m2/g
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
    • C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C01B33/22—Magnesium silicates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C01B33/32—Alkali metal silicates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/40—Alkaline earth metal or magnesium compounds
    • B01D2251/402—Alkaline earth metal or magnesium compounds of magnesium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/40—Alkaline earth metal or magnesium compounds
    • B01D2251/404—Alkaline earth metal or magnesium compounds of calcium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/106—Silica or silicates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/20—Organic adsorbents
    • B01D2253/202—Polymeric adsorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/25—Coated, impregnated or composite adsorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/30—Physical properties of adsorbents
    • B01D2253/302—Dimensions
    • B01D2253/306—Surface area, e.g. BET-specific surface
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
    • B01D2257/702—Hydrocarbons
    • B01D2257/7022—Aliphatic hydrocarbons
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
    • B01D2257/708—Volatile organic compounds V.O.C.'s
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/06—Polluted air

Definitions

  • the present invention relates to a sorbent for capture of formaldehyde. It further relates to a formaldehyde filter comprising such a sorbent, and to use of the proposed sorbent for capture of formaldehyde.
  • Formaldehyde is a volatile organic compound (VOC) present in e.g . resins used in the manufacture of composite wood products, bu ilding materials, household products such as glue, paint, coatings, carpets, etc.
  • VOC volatile organic compound
  • Formaldehyde is considered to be a human carcinogen and exposure to increased levels of formaldehyde may be associated with long-term health risks.
  • Formaldehyde is also associated with short term health effects, such as burning sensations in the eyes, nose, and throat, coughing , nausea, and skin irritation, which may arise also at modestly increased levels of exposure.
  • Another object is to provide a sorbent for capture of formaldehyde which can be cost efficiently produced .
  • At least the primary object is achieved by means of a sorbent for capture of formaldehyde according to claim 1 .
  • the sorbent comprises:
  • hydrophilic amorphous precipitated silica material having a BET surface area of at least 200 m 2 /g ;
  • PEI polyethylenimine
  • Sorbents accord ing to the invention may be used to remove formaldehyde from various environments in which formaldehyde is present, also at relatively low concentrations.
  • the sorbent may efficiently remove formaldehyde by means of chemisorption without the use of potentially hazardous chemicals. Thanks to the large BET surface area of the amorphous precipitated silica material , the PEI can be spread out over a large surface which thereby becomes active in the uptake of formaldehyde.
  • the sorbent can furthermore be cost efficiently produced by means of mixing alkali silicate with a salt solution followed by ambient pressure drying , such as previously described in WO2006/071 183, wherein the PEI may be added to and mixed with the precipitated silica after wash ing and dewatering , before final drying to obtain the sorbent in powder or granular form . Doping of the amorphous precipitated silica with PEI can thereby efficiently be included in the production process.
  • the polyethylenimine (PEI , (C2H5N) n ) is able to chemically react with formaldehyde and form a surface bound reaction product, thereby trapping it in the porous structure of the sorbent. Since the PEI acts so as to chemisorb formaldehyde, formaldehyde trapped within the sorbent is not released upon a change in e.g . temperature and/or formaldehyde concentration .
  • the sorbent comprises no other organic compound than PEI .
  • the amorphous precipitated silica material is therefore hydroph ilic.
  • the amorphous precipitated silica material has a BET surface area of at least 300 m 2 /g , preferably of at least 400 m 2 /g .
  • the relatively large BET surface area is beneficial for the adsorption efficiency of the sorbent and increases the formaldehyde uptake.
  • the amorphous precipitated silica material is a mesoporous material comprising agg lomerates of porous particles according to the formula Me y O x m S 1O2, wherein Me denotes any two or more metals selected among Ca, Mg , Cu , Zn , Mn , Cd , Pb, N i, Fe, Cr, Al, Ti, V, Co, Mo, Sn , Sb, Sr, Ba and W, y denotes the molar ratio of metallic constituents to oxygen, and m denotes the molar ratio of Si02/Me y O.
  • Me denotes any two or more metals selected among Ca, Mg , Cu , Zn , Mn , Cd , Pb, N i, Fe, Cr, Al, Ti, V, Co, Mo, Sn , Sb, Sr, Ba and W
  • y denotes the molar ratio of metallic constituents to oxygen
  • m denotes the m
  • the precipitated silica material accord ing to this formula is known to have a relatively large BET surface area and can be manufactured with suitable pore sizes within the mesoporous range, i.e. 2-50 nm.
  • the value of y may vary within the range 0.5-2 , depending on the valences of the metals.
  • Me denotes Ca and Mg .
  • a combination of Ca and Mg has proved to give good results in terms of BET surface area, pore size distribution and dopability of the silica material with the PE L
  • the molar ratio of Ca/Mg may e.g .
  • the molar ratio of Ca/Mg varies within the range 0.05 ⁇ Ca/Mg ⁇ 1 .0.
  • the polyethylenimine is present within the sorbent in an amount of 1 -40 wt.%.
  • the polyethylenimine is present within the sorbent in an amount of 1 -20 wt.%.
  • the polyethylenimine is present within the sorbent in an amount of 5-20 wt.%. According to one embodiment, the polyethylenimine is present within the sorbent in an amount of 5-12 wt.%.
  • the amount of PEI is given in percentage by weight (wt. %) of dry matter of the total sorbent weight.
  • wt. % percentage by weight
  • desirable levels of formaldehyde adsorption may be achieved .
  • amount By limiting the amount to 40 wt. %, preferably 20 wt. %, and more preferably 12 wt. %, negative effects on the BET surface area, the pore size and the mechanical strength of the sorbent can be avoided .
  • the invention also relates to a formaldehyde gas filter comprising the proposed sorbent in accordance with any of the above described embodiments.
  • the formaldehyde gas filter may comprise a gas permeable carrier for supporting the sorbent.
  • the present disclosure also relates to use of the proposed sorbent accord ing to any one of the above described embodiments for capture of formaldehyde gas.
  • Fig . 1 shows formaldehyde uptake of sorbents according to embodiments of the invention and reference sorbents.
  • a sorbent for capture of formaldehyde comprises an amorphous precipitated silica material having the general formula Me y O x m S 1O2, wherein Me denotes any two or more metals selected among Ca, Mg , Cu , Zn , Mn , Cd , Pb, Ni, Fe, Cr, Al, Ti, V, Co, Mo, Sn , Sb, Sr, Ba and W, y denotes the molar ratio of metallic constituents to oxygen , and m denotes the molar ratio of S iO2/Me y O.
  • a method of manufacturing this material by mixing alkali silicate with a salt solution is disclosed in WO 2006/071 183.
  • the material is formed as a precipitate by mixing alkali silicate with a salt solution .
  • the precipitate is thereafter processed in various ways to obtain an end product having desired properties in terms of pore size, particle size, surface area, density, etc.
  • the amorphous precipitated silica material used for the sorbent according to embodiments of the invention has a mesoporous structure with a BET surface area of at least 200 m 2 /g , preferably of at least 300 m 2 /g or more preferably of at least 400 m 2 /g .
  • the amorphous precipitated silica material is doped with an organ ic compound in the form of polyethylenimine (PE I) bound to a surface of the amorphous precipitated silica material.
  • PE I polyethylenimine
  • the combination of PEI and amorphous precipitated silica has according to the present invention been found to be beneficial for the capture of formaldehyde.
  • the PEI is preferably present within the sorbent in an amount of 1 -40 wt. %, more preferably in an amount of 1 -20 wt.% , and even more preferably in an amount of 5-20 wt.%, and most preferably in an amount of 5-12 wt.% .
  • the suitable amount of PEI depends on e.g .
  • the sorbent according to the invention may advantageously be included in a formaldehyde gas filter, intended to remove formaldehyde from various environments in which formaldehyde is present, also at relatively low concentrations such as less than 0.5 ppm or less than 1 ppm.
  • the sorbent may for th is purpose be supported on a gas permeable carrier, such as in a filter cassette.
  • a fan may be provided for forcing polluted air through the formaldehyde gas filter.
  • the amorphous precipitated silica material of S 1 -S3, T1 -T5 and T7 was a CMS type Quartzene® material .
  • the amorphous precipitated silica material of the sorbent samples S 1 , S2 and S3 and the test samples T1 -T5 and T7 was prepared in accordance with the method described in WO 2006/071 183, wherein calcium and magnesium sources were added to a dilute active aqueous sodium silicate solution.
  • a salt solution comprising MgC and CaC , was prepared at a ratio of 68 mol% Mg and 32 mol% Ca.
  • the salt solution was poured onto the 1 .5 M (with respect to S 1O2) sodium silicate solution, and the resulting mixture was agitated at room temperature. Su bsequent coagulation occurred and the slurry formed was thereafter washed and dewatered on a filter cloth by means of vacuum suction to become a cake or gel .
  • the amorphous precipitated silica material of samples T6 and T8 was prepared analogously but was functionalised using a functional group to obtain a hydrophobic surface.
  • a dilute solution comprising PEI was added to the obtained gel .
  • the PE I doped gel was dried to obtain the sorbent in powder or granu lar form.
  • solutions containing the other listed compounds were added to the obtained gel to obtain the samples T1 -T5.
  • the total formaldehyde uptake in mg formaldehyde per gram sorbent for the different tested samples is shown in fig . 1 . All tests were performed by passing air containing formaldehyde at a concentration of 260 ppm through the sorbent. Sample S2 containing 5 wt.% of PEI was also tested at a formaldehyde concentration of 130 ppm. The volume flow of air was 0.9 l/min . The reference sample Ref1 was tested twice with slightly different measurement procedures and the resu lts are shown as Ref1 -1 and Ref1 -2. As can be seen from fig .
  • the sample S 1 containing 40 wt.% PE I shows a somewhat lower uptake of around 40 mg per gram sorbent, which is however more than the uptake of the reference samples Ref1 and Ref2.
  • a comparison between the hydrophobic sample T6 and the samples S2 and S3 indicate that the hydrophilic nature of the amorphous precipitated silica material is important for achieving a high formaldehyde uptake.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Analytical Chemistry (AREA)
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  • Engineering & Computer Science (AREA)
  • Inorganic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Environmental & Geological Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)

Abstract

A sorbent for capture of formaldehyde, comprising a hydrophilic amorphous precipitated silica material having a BET surface area of at least 200 m2/g, and an organic compound in the form of polyethylenimine (PE I) bound to a surface of the amorphous precipitated silica material.

Description

A sorbent and a filter
TECH N ICAL FI ELD
The present invention relates to a sorbent for capture of formaldehyde. It further relates to a formaldehyde filter comprising such a sorbent, and to use of the proposed sorbent for capture of formaldehyde.
BACKGROUND AND PRIOR ART
Formaldehyde (CH2O) is a volatile organic compound (VOC) present in e.g . resins used in the manufacture of composite wood products, bu ilding materials, household products such as glue, paint, coatings, carpets, etc. Formaldehyde is considered to be a human carcinogen and exposure to increased levels of formaldehyde may be associated with long-term health risks. Formaldehyde is also associated with short term health effects, such as burning sensations in the eyes, nose, and throat, coughing , nausea, and skin irritation, which may arise also at modestly increased levels of exposure. It is therefore desirable to prevent off-gassing of formaldehyde from products containing the compound , or to otherwise reduce levels of formaldehyde in e.g . indoor environments. I n particular, it is desirable to reduce levels of formaldehyde in formaldehyde-based resins industry, in which the highest potential exposure occurs. Known methods for removing formaldehyde include the use of activated carbon filters and filters comprising potassium permanganate. However, it is desirable to provide an improved solution for removal of formaldehyde, which does not involve the use of potentially hazardous chemicals such as potassium permanganate. SUM MARY OF TH E I NVENTION It is a primary object of the present invention to provide an in at least some aspect improved technology by means of which formaldehyde can be removed from environments in which it is present, such as from indoor and industrial environments and packaging . I n particular, it is an object to provide such a technology which can remove formaldehyde relatively efficiently without the use of potentially hazardous chemicals such as potassium permanganate. Another object is to provide a sorbent for capture of formaldehyde which can be cost efficiently produced .
According to a first aspect of the invention , at least the primary object is achieved by means of a sorbent for capture of formaldehyde according to claim 1 . The sorbent comprises:
- a hydrophilic amorphous precipitated silica material having a BET surface area of at least 200 m2/g ; and
- polyethylenimine (PEI) bound to a surface of the amorphous precipitated silica material .
Sorbents accord ing to the invention may be used to remove formaldehyde from various environments in which formaldehyde is present, also at relatively low concentrations. The sorbent may efficiently remove formaldehyde by means of chemisorption without the use of potentially hazardous chemicals. Thanks to the large BET surface area of the amorphous precipitated silica material , the PEI can be spread out over a large surface which thereby becomes active in the uptake of formaldehyde. The sorbent can furthermore be cost efficiently produced by means of mixing alkali silicate with a salt solution followed by ambient pressure drying , such as previously described in WO2006/071 183, wherein the PEI may be added to and mixed with the precipitated silica after wash ing and dewatering , before final drying to obtain the sorbent in powder or granular form . Doping of the amorphous precipitated silica with PEI can thereby efficiently be included in the production process. The polyethylenimine (PEI , (C2H5N)n) is able to chemically react with formaldehyde and form a surface bound reaction product, thereby trapping it in the porous structure of the sorbent. Since the PEI acts so as to chemisorb formaldehyde, formaldehyde trapped within the sorbent is not released upon a change in e.g . temperature and/or formaldehyde concentration .
Preferably, the sorbent comprises no other organic compound than PEI . The amorphous precipitated silica material is therefore hydroph ilic.
According to one embodiment, the amorphous precipitated silica material has a BET surface area of at least 300 m2/g , preferably of at least 400 m2/g . The relatively large BET surface area is beneficial for the adsorption efficiency of the sorbent and increases the formaldehyde uptake.
According to one embodiment, the amorphous precipitated silica material is a mesoporous material comprising agg lomerates of porous particles according to the formula MeyO x m S 1O2, wherein Me denotes any two or more metals selected among Ca, Mg , Cu , Zn , Mn , Cd , Pb, N i, Fe, Cr, Al, Ti, V, Co, Mo, Sn , Sb, Sr, Ba and W, y denotes the molar ratio of metallic constituents to oxygen, and m denotes the molar ratio of Si02/MeyO. A method of manufacturing such an amorphous precipitated silica material has been previously described in WO2006/071 183. The precipitated silica material accord ing to this formula is known to have a relatively large BET surface area and can be manufactured with suitable pore sizes within the mesoporous range, i.e. 2-50 nm. The value of m may vary between 1 -4, or preferably 2-3.7, such as m=3.35. The value of y may vary within the range 0.5-2 , depending on the valences of the metals. According to one embodiment, Me denotes Ca and Mg . A combination of Ca and Mg has proved to give good results in terms of BET surface area, pore size distribution and dopability of the silica material with the PE L The molar ratio of Ca/Mg may e.g . be 35/65 or 32/68, but the molar ratio may of course be optimised to achieve a desired dopability with the PEL Preferably, the molar ratio of Ca/Mg varies within the range 0.05 < Ca/Mg < 1 .0.
According to one embodiment, the polyethylenimine is present within the sorbent in an amount of 1 -40 wt.%.
According to one embodiment, the polyethylenimine is present within the sorbent in an amount of 1 -20 wt.%.
According to one embodiment, the polyethylenimine is present within the sorbent in an amount of 5-20 wt.%. According to one embodiment, the polyethylenimine is present within the sorbent in an amount of 5-12 wt.%.
In the above embodiments, the amount of PEI is given in percentage by weight (wt. %) of dry matter of the total sorbent weight. By including at least 1 wt. %, preferably at least 5 wt.% , desirable levels of formaldehyde adsorption may be achieved . By limiting the amount to 40 wt. %, preferably 20 wt. %, and more preferably 12 wt. %, negative effects on the BET surface area, the pore size and the mechanical strength of the sorbent can be avoided . By limiting the PE I to maximum 20 wt.%, all PEI can be bound to the surface within the internal pore structure of the sorbent, and the adsorption of formaldehyde can be particu larly efficient. The invention also relates to a formaldehyde gas filter comprising the proposed sorbent in accordance with any of the above described embodiments. The formaldehyde gas filter may comprise a gas permeable carrier for supporting the sorbent.
The present disclosure also relates to use of the proposed sorbent accord ing to any one of the above described embodiments for capture of formaldehyde gas.
Further advantages as well as advantageous features of the present invention will appear from the following detailed description .
BRI EF DESCRI PTI ON OF TH E DRAWI NGS Embodiments of the invention will in the following be described with reference to the appended drawings, in which:
Fig . 1 shows formaldehyde uptake of sorbents according to embodiments of the invention and reference sorbents.
DETAI LED DESCRI PTI ON OF EMBODI MENTS OF THE I NVENTION
A sorbent for capture of formaldehyde according to an embodiment of the invention comprises an amorphous precipitated silica material having the general formula MeyO x m S 1O2, wherein Me denotes any two or more metals selected among Ca, Mg , Cu , Zn , Mn , Cd , Pb, Ni, Fe, Cr, Al, Ti, V, Co, Mo, Sn , Sb, Sr, Ba and W, y denotes the molar ratio of metallic constituents to oxygen , and m denotes the molar ratio of S iO2/MeyO. The amorphous precipitated silica material may be in the form of a Quartzene® material of CMS type, which can be written as (Cao.35, Mgo.65)O x 3.35 S 1O2, i.e. Me=(Cao.35, Mgo.65) , y= 1 and m=3.35. A method of manufacturing this material by mixing alkali silicate with a salt solution is disclosed in WO 2006/071 183. The material is formed as a precipitate by mixing alkali silicate with a salt solution . The precipitate is thereafter processed in various ways to obtain an end product having desired properties in terms of pore size, particle size, surface area, density, etc. The amorphous precipitated silica material used for the sorbent according to embodiments of the invention has a mesoporous structure with a BET surface area of at least 200 m2/g , preferably of at least 300 m2/g or more preferably of at least 400 m2/g .
The amorphous precipitated silica material is doped with an organ ic compound in the form of polyethylenimine (PE I) bound to a surface of the amorphous precipitated silica material. The combination of PEI and amorphous precipitated silica has according to the present invention been found to be beneficial for the capture of formaldehyde. The PEI is preferably present within the sorbent in an amount of 1 -40 wt. %, more preferably in an amount of 1 -20 wt.% , and even more preferably in an amount of 5-20 wt.%, and most preferably in an amount of 5-12 wt.% . However, the suitable amount of PEI depends on e.g . the available BET surface area of the amorphous precipitated silica material as well as the pore size of this material . The sorbent according to the invention may advantageously be included in a formaldehyde gas filter, intended to remove formaldehyde from various environments in which formaldehyde is present, also at relatively low concentrations such as less than 0.5 ppm or less than 1 ppm. The sorbent may for th is purpose be supported on a gas permeable carrier, such as in a filter cassette. A fan may be provided for forcing polluted air through the formaldehyde gas filter. EXAM PLES
A number of exemplary formaldehyde sorbents according to embodiments of the invention, S 1 -S3, were manufactured and tested together with test samples T1 -T7 and reference prior art sorbents, Ref1 -Ref2. The tested sorbents are listed in Table I .
Sam ple Description
S 1 40 wt. % PEI on precipitated silica
S2 5 wt. % PEI on precipitated silica
S3 20 wt.% PEI on precipitated silica
T1 10 wt. % triisopropanolamine on precipitated silica
T2 10 wt. % (3-Aminopropyl)triethoxysilane on
precipitated silica
T3 5 wt.% urea on precipitated silica
T4 10 wt.% urea on precipitated silica
T5 20 wt.% polyethylenoxide on precipitated silica
T6 8 wt.% PEI on hydrophobized precipitated silica
T7 Non-doped precipitated silica (hydrophilic)
T8 Hydrophobized precipitated silica
Ref1 Activated carbon (Jacobi)
Ref2 Commercial CamPure® adsorbent from Camfil The amorphous precipitated silica material of S 1 -S3, T1 -T5 and T7 was a CMS type Quartzene® material . The amorphous precipitated silica material of the sorbent samples S 1 , S2 and S3 and the test samples T1 -T5 and T7 was prepared in accordance with the method described in WO 2006/071 183, wherein calcium and magnesium sources were added to a dilute active aqueous sodium silicate solution. A salt solution , comprising MgC and CaC , was prepared at a ratio of 68 mol% Mg and 32 mol% Ca. The salt solution was poured onto the 1 .5 M (with respect to S 1O2) sodium silicate solution, and the resulting mixture was agitated at room temperature. Su bsequent coagulation occurred and the slurry formed was thereafter washed and dewatered on a filter cloth by means of vacuum suction to become a cake or gel .
The amorphous precipitated silica material of samples T6 and T8 was prepared analogously but was functionalised using a functional group to obtain a hydrophobic surface. For the samples S 1 -S3 and T6, a dilute solution comprising PEI was added to the obtained gel . After thorough mixing , the PE I doped gel was dried to obtain the sorbent in powder or granu lar form. In an analogous way, solutions containing the other listed compounds were added to the obtained gel to obtain the samples T1 -T5.
The total formaldehyde uptake in mg formaldehyde per gram sorbent for the different tested samples is shown in fig . 1 . All tests were performed by passing air containing formaldehyde at a concentration of 260 ppm through the sorbent. Sample S2 containing 5 wt.% of PEI was also tested at a formaldehyde concentration of 130 ppm. The volume flow of air was 0.9 l/min . The reference sample Ref1 was tested twice with slightly different measurement procedures and the resu lts are shown as Ref1 -1 and Ref1 -2. As can be seen from fig . 1 , all samples contain ing PEI loaded on hydroph ilic amorphous precipitated silica exhibit relatively high formaldehyde uptakes in comparison with the test samples T1 - T8 and the reference samples Ref1 and Ref2. The sample S3 containing 20 wt.% PEI on CMS type Quartzene® material shows the best results in terms of formaldehyde uptake of more than 90 mg adsorbed formaldehyde per gram sorbent. Also the sample S2, comprising 5 wt.% PEI , shows a high uptake of formaldehyde of around 60 mg per gram sorbent. The sample S 1 containing 40 wt.% PE I shows a somewhat lower uptake of around 40 mg per gram sorbent, which is however more than the uptake of the reference samples Ref1 and Ref2. A comparison between the hydrophobic sample T6 and the samples S2 and S3 indicate that the hydrophilic nature of the amorphous precipitated silica material is important for achieving a high formaldehyde uptake.
To summarize, the experimental resu lts show that all sorbents S 1 -S3 can function for capture of formaldehyde at ambient conditions for the tested concentrations. It is expected that they will likewise be efficient sorbents for formaldehyde at lower concentrations, such as at 1 ppm or less.
The invention is of course not in any way restricted to the embodiments described above. On the contrary, many possibilities to mod ifications thereof will be apparent to a person with ordinary skill in the art without departing from the basic idea of the invention such as defined in the appended claims.

Claims

CLAI MS
1 . A sorbent for capture of formaldehyde, comprising :
- a hydrophilic amorphous precipitated silica material having a BET surface area of at least 200 m2/g ; and
- an organic compound in the form of polyethylenimine (PEI) bound to a surface of the amorphous precipitated silica material .
2. The sorbent according to claim 1 , wherein the amorphous precipitated silica material has a BET surface area of at least 300 m2/g , preferably of at least 400 m2/g .
3. The sorbent accord ing to claim 1 or 2, wherein the amorphous precipitated silica material is a mesoporous material comprising agglomerates of porous particles according to the formula MeyO x m S 1 O2 , wherein Me denotes any two or more metals selected among Ca, Mg , Cu , Zn , Mn , Cd , Pb, Ni , Fe, Cr, Al , Ti , V, Co, Mo, Sn, Sb, Sr, Ba and W, y denotes the molar ratio of metallic constituents to oxygen, and m denotes the molar ratio of Si02/MeyO.
4. The sorbent according to claim 3, wherein Me denotes Ca and Mg .
5. The sorbent according to any one of the preceding claims, wherein the polyethylenimine is present with in the sorbent in an amount of 1 -40 wt.%.
6. The sorbent according to any one of the preceding claims, wherein the polyethylenimine is present with in the sorbent in an amount of 1 -20 wt.%.
7. The sorbent according to any one of the preceding claims, wherein the polyethylenimine is present with in the sorbent in an amount of 5-20 wt.%.
8. The sorbent according to any one of the preceding claims, wherein the polyethylenimine is present with in the sorbent in an amount of 5-12 wt.%.
9. A formaldehyde gas filter comprising the sorbent according to any one of the preceding claims.
10. Use of the sorbent according to any one of claims 1 -8 for capture of formaldehyde.
PCT/SE2018/050405 2017-05-03 2018-04-20 A sorbent and a filter Ceased WO2018203796A1 (en)

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