Preparation Of Modified BPM Using SBS As Starting Material And Its Application In Electro-synthesis Process

Using SBS(styrene-butadiene-styrene triblock copolymer) as a matrix,the SBS-g-AA /SBS-g-DMAEMA bipolar membrane(marked as SBS BPM ) was prepared by SBS doped acrylic acid(AA) through free radioal grafting reaction as the anode membrane, and SBS doped dimethyl amino ethyl methacrylate(DMAEMA) as the cathode membrane,respectively.The component and morphology of the SBS BPM were characterized by IR,TGA and SEM.IR results indicated that -COOH,-CH₂N(CH₃)₂ functional groups were graftinted in the SBS BPM.Two ways were adopted to graft -SO₃^- into SBS chain for enhancing the proton conductivity of the anode membrane.The first way:SBS was sulfonated using 98%H₂SO₄,then doped acrylic acid(AA) through free radical grafting polymerization. The measurements of IR,water uptake and degree of swelling indicated that the C=C double bonds in SBS was sulfonated,the crosslinked SBS membrane shows a good dimensional stability in water.The second method:SBS was reacted with AA and styrene sulfonate(StSO₃Na) by the grafting copolymerization,the swelling degree of the grafting copolymer SBS-g-(AA/StSO₃Na) is obvious.The AC impedances of BPM6 and BPM7 are similar.The SBS BPM was used as a separator between the cathode and anode chamber in the electrolysis cell to produce glyoxylic acid in pairs.The cathode electrolyte is the mixture of saturation oxalic acid and HCl,the anode electrolyte is the mixture of 12%glyoxal and 10%KBr,graphite was used as the cathode,Pb as the anode.The average current efficiencies were 79.2%and 64.7%in cathode and anode respectively at 16 mA/cm².The electrolysis volvage was as low as 3.2V.Using BPM7 as separator,the average current efficiency was 78.2%and 75.9%in cathode and anode respectively,the electrolysis volvage was as low as 3.4V.Then,SBS was modified by the trimethoxysilane.The cross-linked network of -Si-O- was obtained by sol-gel reaction of trimethoxysilane hydrolysis.The SBS-g-(AA/StSO₃Na-SiO₂)/SBS-g-DMAEMA-SiO₂ bipolar membrane was used in the electro-generation of organic compound to expand its application.The BPM10 was nsed as the separator in the electrolysis cell for electro-generation of 2,2-dimethyl-3-hydroxypropionic acid(HPAc) and succinic acid.Graphite was used as anode electrode. NaBr was added into the anode chamber as a media.When the electrolysis begins,Br is oxidized to Br₂,which serves as an oxidant to oxidize hydroxypivalaldehyde(HPA) to HPAc.The indirect electro-oxidation cyclic process carried out in the electrolysis cell. The hydroxyl ions from the interface of the bipolar membrane move into the anode chamber,and enhance the ion conductivity as well as the forward reaction.The highest current efficiency was up to 69.8%,the average current efficiency was up to 53.8%. Copper was used as a cathode electrode to electroreduce maleic acid for producing succinic acid in cathode room,the average current efficiency was up to 62.5%,and the yield of succinic acid was 64.1%.Based on the application of bipolar membrane in the electro-generation of inorganic compound.Using the SBS BPM10 as a separator,Graphite as the electrode,Ce³⁺/Ce⁴⁺ as medium to electrooxidate 2,3,4,5- tetramethoxyl toluene indirectly to produce coenzyme Q₀ in cathode.O₂ was electroreduced to H₂O₂,then react with acetic acid to produce Q₀. The current efficiency was up to 58.4%and 48.2%in cathode and anode respectively during the current density of 10 mA/cm² at room temperature,and the yield of cathode and anode was 40.2%and 48.0%,respectively.