CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase application under 35 U.S.C. § 371 of PCT/SG2017/050385, filed Jul. 28, 2017, and claims the benefit of and priority to Singapore Provisional Patent Application No. 10201606249T filed Jul. 28, 2016, the disclosure of which are hereby incorporated herein by reference in their entirety.

FIELD OF INVENTION

This invention relates to the development of an organic and inorganic composite material that may be moulded into any desired shape, which composite material may be used for purifying gas containing acidic and/or basic impurities.

BACKGROUND

Fossil fuels are a non-renewable form of energy that are expected to be exhausted by the end of the 21st century. Gasoline and diesel, in particular, are obtained from crude oil after fractional distillation in the oil refinery process and are the main source of fuel that powers today's cars. However, the combustion of gasoline and diesel produces undesirable compounds such as NOx, SOx, H2S and particulate emissions that are harmful to the environment. The anticipated rapid decline in fossil fuels, coupled with environmental pollution, has driven the search for alternative and cleaner power systems to drive such vehicles.

One of the potential replacements for vehicles using internal combustion engines are vehicles powered by fuel cells. Fuel cell vehicles are expected to be more efficient, (potentially three times more efficient) petrol engine cars. This is because the efficiency of a fuel cell is much higher than that of a conventional combustion engine (Kojima, Y., et al.,International Journal of Hydrogen Energy,2002. 27(10): p. 25 1029-1034.).

One of the market barriers to adopting vehicles powered by fuel cells is the availability and cost of producing pure hydrogen gas. The majority of hydrogen produced today is provided by steam reforming of natural gas or other hydrocarbons (Chinnappan, A., et al.,International Journal of Hydrogen Energy,2012. 37(13): p. 10240-10248.). Electrolysis of water using renewable energies, such as solar and wind is another method that can be used to produce hydrogen, but these methods are less common due to their high cost and relatively low efficiency (Jana, P., et al.,International Journal of Hydrogen Energy,2012. 37(8): p. 7034-7041.).

A further alternative source of hydrogen gas can be industrial processes where hydrogen is produced as a by-product. A good example of such an industrial process is the chlor-alkaline process. Chlor-alkaline plants discharge large amounts of hydrogen gas as a by-product while producing chlorine gas for other applications. However, the discharged gas contains chloride anion impurities that are known to have adverse effects on the performance of a fuel cell (S. M. M. Ehteshami, et al.,Journal of Industrial and Engineering Chemistry,2016. (34): p. 1-8.). Therefore, the discharged hydrogen gas must be purified to an acceptable level before it can be used in a hydrogen fuel cell system.

TABLE 1Impurity concentration of 4 gas samples taken at 1 h intervalTestMethodUnitResultsCarbon MonoxideMethanizermol ppm<1Carbon DioxideMethanizermol ppm<1CO2/SO2ASTM D5504-08mol ppm<0.01/<0.01Hydrogen sulfideASTM D5504-08mol ppm<0.01MethaneGC-PDHIDmol ppm<1OxygenGC-PDHIDmol ppm21.5NitrogenGC-PDHIDmol ppm10.5HydrogenUOP 539-12mol %98.24ChlorideC.I.Cwt. ppm<5Water ContentSolvent Extract/Karlvol %1.77FisherChlorineDrager Tubemol ppm<0.3

Table 1 above shows the impurity concentration of discharged hydrogen gas from a chlor-alkaline plant in Singapore. Conventionally, these acidic gases are removed by gas-liquid absorption-stripping processes using aqueous solutions of alkanolamines. The most commonly used alkanolamines include monoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine (MDEA) (H. Y. Huang, et al.,Industrial&Engineering Chemistry Research,2003. 42: p. 2427-2433). Though a mature technology being applied extensively today, this gas absorption process is highly energy-intensive because it requires significant energy costs to regenerate the alkanolamine solutions and it is also plagued by corrosion problems.

Thus, there remains a need for improved methods of removing acidic (or basic) impurities from gases provided as by products from industrial processes, as removing such impurities in a cheaper and more energy efficient manner may help to kick-start the fuel cell industry, amongst others.

SUMMARY OF INVENTION

In this invention, we have developed an organic and inorganic moulded composite and its fabrication process with the intended application in gas purification.

Thus, in a first aspect of the invention there is provided a composite material comprising:a particulate adsorbing material; anda crosslinked polymer comprising acidic or basic residues, whereinthe particulate adsorbing material is dispersed within a polymer matrix formed by the crosslinked polymer, and the particulate adsorbing material is selected from one or more of the group consisting of mesoporous silica, mesoporous carbon, mesoporous zinc oxide, a bentonite clay, and a kaolinite clay.

In embodiments of the first aspect of the invention:(a) the weight:weight ratio of the particulate adsorbing material to crosslinked polymer may be from 0.5:1 to 5:1;(b) the particulate adsorbing material may be selected from one or more of the group consisting of mesoporous silica, a bentonite clay, and a kaolinite clay (i.e. the particulate adsorbing material may be a mesoporous silica, optionally wherein the particulate adsorbing material may be a mesoporous silica selected from one or more of the group consisting of SBA-15, SBA-16, MCM-41, MCM-48, HMS, MSU-F, MSU-H, and MSU-X (e.g. the particulate adsorbing material is a mesoporous silica selected from SBA-15 and/or MCM-41);(c) the particulate adsorbing material may further comprise functional groups selected from a C1-10alkylamine and a C1-10alkylcarboxylic acid (e.g. the C1-10alkylamine may be n-propylamine), said functional groups may be present in a weight ratio with respect to the particulate material that may be from 0.05:1 to 1:1, such as from 0.07:1 to 0.25:1, such as from 0.09:1 to 0.23:1;(d) when the crosslinked polymer has basic residues, it may be formed from a monomeric material that may be preferably water soluble and which has at least one ethylenic bond and an amide functional group, optionally wherein the monomeric materials may be selected from one or more of the group consisting of acrylamide, methacrylamide, an alkyl-acrylamide, an alkyl-methacrylamide, dimethyl aminopropyl methacrylamide, a hydroxy-alkyl acrylamide, and a hydroxy-alkyl methacrylamide;(e) when the crosslinked polymer has basic residues, the weight:weight ratio of the particulate adsorbing material to crosslinked polymer may be from 0.8:1 to 2:1;(f) when the crosslinked polymer has acidic residues, it may be formed from a monomeric material that may be preferably water soluble and which has at least one ethylenic bond and a carboxylic acid functional group, optionally wherein the monomeric material may be methacrylic acid and/or acrylic acid or, more particularly, acrylic acid;(g) when the crosslinked polymer has acidic residues, the weight:weight ratio of the particulate adsorbing material to crosslinked polymer may be from 2:1 to 4.2:1;(h) the crosslinked polymer may comprise a residue from a crosslinking agent and the crosslinking agent may be selected from one or more of the group consisting of N,N′-methylenebis(acrylamide) and N,N′-diallyl-L-tartardiamide (e.g. the crosslinking agent may be N,N′-methylenebis(acrylamide)) and, in(i) the crosslinked polymer may be formed using a weight:weight ratio of from 5:1 to 50:1 of a monomer to a crosslinking agent, optionally wherein the weight:weight ratio may be from 10:1 to 25:1, such as 15:1.

In specific embodiments of the first aspect of the invention, the composite material may be a composite comprising mesoporous silica (e.g. MCM-41) and crosslinked acrylamide in a weight:weight ratio of about 1.56:1 (e.g. 1.5625:1), where the crosslinking agent is N,N′-methylenebis(acrylamide), which is present in a weight:weight ratio of 1:15 with respect to the acrylamide monomer. In alternative embodiments that may be mentioned herein, the composite may be a composite comprising a n-propylamine-functionalised mesoporous silica (e.g. MCM-41) and crosslinked acrylamide in a weight:weight ratio of about 1.71:1, where the crosslinking agent is N,N′-methylenebis(acrylamide), which is present in a weight:weight ratio of 1:15 with respect to the acrylamide monomer and the functional group is present in about a 0.37:1 weight ratio with respect to the mesoporous silica.

In a second aspect of the invention, there is provided a method of forming a composite material according to the first aspect of the invention and any technically sensible combination of its embodiments, wherein the process comprises the steps of:(i) forming a mixture comprising a particulate adsorbing material, at least one monomer having an ethylenic bond and a carboxylic acid or basic functional group, a crosslinking agent, a polymerisation initiator and a catalyst in a solvent; and(ii) initiating a polymerisation reaction to form the composite material.

In embodiments of the second aspect of the invention:(a) the initiator may be ammonium or potassium persulfate, the catalyst may be N,N,N′,N′-tetramethylethylenediamine and the solvent may comprise water (e.g. the solvent is water);(b) the mixture in step (i) of the second aspect of the invention may further comprise a C1-10alkylaminetrialkyloxysilane or a C1-10alkylcarboxylic acid trialkyloxysilane (e.g. the C1-10alkylaminetrialkyloxysilane may be (3-aminopropyl)triethoxysilane), or the particulate adsorbing material may be provided pre-functionalized by C1-10alkylamine or C1-10alkylcarboxylic acid groups (e.g. the particulate adsorbing material may be provided pre-functionalized by n-propylamine);(c) the process may further comprise ball milling of the mixture formed in step (i) of the second aspect of the invention.

In a third aspect of the invention, there is provided a use of a composite material according to the first aspect of the invention and any technically sensible combination of its embodiments to remove acidic or basic impurities from a gas in need thereof, wherein a composite material comprising acidic residues is used to remove basic impurities and a composite material comprising basic residues is used to remove acidic impurities.

In a fourth aspect of the invention, there is provided a method of purifying a gas, comprising contacting a gas with a composite material according to the first aspect of the invention and any technically sensible combination of its embodiments, wherein a composite material comprising acidic residues is used to remove basic impurities from a gas in need thereof and a composite material comprising basic residues is used to remove acidic impurities from a gas in need thereof.

