mSA-CS双极膜在电还原制备巯基乙酸中的应用

用Ca^2＋改性海藻酸钠(SA), 用戊二醛(GA)改性壳聚糖(CS), 制备mSA-CS聚合物双极膜. 测定膜的红外光谱及机械性能, 并作膜的热重分析. 以扫描电镜观察膜表面和界面层形态. 测定了mCS膜制备溶液的粘度以及mSA, mCS膜的含水率、离子交换容量及酸碱浓度对膜溶胀度的影响. 将mSA-CS双极膜应用于电解还原制备巯基乙酸(TGA). 实验结果表明, 以硫代硫酸钠法合成的TGA和二硫代二乙酸(DTDGA)的混合液作阴极液, TGA初始合成质量分数为4.61%, 电流密度为10 mA•cm^－2下常温电解, 产物巯基乙酸的电流效率达66.7%. 与传统的金属还原法还原DTDGA成TGA相比, 不仅省去了昂贵的金属还原剂的消耗, 而且消除了对环境的污染.     

Ni-mSA-mCS双极膜的制备及其在电合成TGA中的应用

通过用Ca2+改性海藻酸钠(SA)和用戊二醛改性壳聚糖(CS)制备Ni-mSA-mCS(m: modified)双极膜. 镍网预先埋在mSA膜表面作为阴极, 不仅增强了膜的机械性能, 而且降低阴极电解液的IR降, 实现零极距. 测定了膜的红外光谱、电镜扫描、机械性能. 将Ni-mSA-mCS双极膜应用于电还原制备巯基乙酸(TGA). 实验结果表明, 电流密度为10 mA·cm-2, 常温电解, 电流效率可达66.7%. 与传统的Zn还原法相比, 不仅省去了昂贵的金属还原剂的消耗, 而且消除了锌泥对环境的污染.     

锌汞齐还原法测定二硫代二乙酸

将锌汞齐能还原二硫代二乙酸(DTDGA)成巯基乙酸(TGA)的原理和碘量法滴定相结合,对电还原DTDGA合成TGA反应液中的DTDGA进行定量分析,测定结果的相对标准偏差为0.37%,加标平均回收率100.6%。     

m(SA-CS)BM串联电解槽双成对电解制备乙醛酸

分别用戊二醛和二价锡离子改性壳聚糖(CS)和海藻酸钠(SA),制备改性海藻酸钠/亮聚糖双极膜[m(SA-CS)BM].将其作为双阴阳极电解槽的隔膜,应用于双成对电合成乙醛酸体系.在电场的作用下,双极膜中水电离后生成的H+透过Msa阳离子膜进入阴极室,以补充草酸电还原生成乙醛酸过程中H+的消耗;OH-透过Mcs阴离子膜进入阳极室,与乙二醛电氧化生成乙醛酸过程中产生的H+结合生成H2O,以增大正向反应的速度.在电流密度为30mA/cm2,20℃下电解,双阴极室的电流效率分别可达86.94%和82.81%,双阳极室的电流效率可达81.99%和78.62%,电解电压稳定在3.0V左右.     

Ni-P-mCMC/mCS双极膜技术在成对电解制备糠醇、糠酸中的应用

以磷酸化试剂改性羧甲基纤维素钠(mCMC)制备了阳膜层,以戊二醛改性壳聚糖(mCS)制备了阴膜层溶胶,将阴膜层溶胶流延于阳膜层上,制备了P-mCMC/mCS双极膜,而后以化学镀方法在阳膜层表面镀镍,制备了Ni-P-mCMC/mCS双极膜,并应用于成对电合成糠醇(阴极室中)、糠酸(阳极室中)。在电场的作用下,双极膜中水电离后生成的H+透过mCMC阳离子膜进入阴极室,促进糠醛电还原生成糠醇过程的进行;OH-透过mCS阴离子膜进入阳极室,与糠醛电氧化生成糠酸过程中产生的H+结合生成H2O,以增大正向反应的速度。在电流密度为2.5×10-2A/cm2,30℃下电解,阴阳两极室的电解效率分别为83.0%和77.4%,电解槽电压稳定在3.0V左右。     

发泡镍电极电化学还原嘌呤中间体

由三维发泡镍电极H2SO4电解质和阳离子交换膜,组成隔膜式三维发泡镍电解循环装置.利用该装置将3-甲基-4-亚氨基-5-异亚硝基脲嗪(NAU)电还原为3-甲基-4,5-二氨基脲嗪(DAU).比较发泡镍阴极的电流密度,测定不同pH条件下的反应电位.结果表明,发泡镍电极的电流密度比平板镍高77.3%～86.7%,电流效率平均90.3%,NAU还原转化率平均98.4%,电还原能耗平均2.92kWh/kg.恒电流电还原过程出现峰电位,继续延长电还原时间则有副反应产生.分别以传统铁粉还原和电还原的DAU完成下游嘌呤产品的合成,证明电还原产品收率不低于铁粉还原.     

钨酸盐/过钨酸盐体系阴极间接电氧化合成红曲黄色素

以自制SBS-g-(AA/StSO3Na)/SBS-g-DMAEMA双极膜作电解槽阴阳两极室的隔膜,借助正交试验确定阴极电还原氧气产生过氧化氢的最优条件,进而利用钨酸钠/过钨酸钠体系由阴极间接电氧化红曲红制备红曲黄色素.实验表明:以石墨作电极,阳极液为10%硫酸溶液,阴极液为0.5g·L-1红曲红丙酮水溶液,添加钨酸钠(浓度15mmol/L),调节pH至3,在通氧速率65cm3/min,电流密度5.78mA.cm-2下电解2h,阴极平均电流效率可达72.39%.电解产物经红外表征和紫外跟踪分析,证实了红曲红烯键环氧化反应的发生.     

mCMC-PEG/mCS-PEG双极膜的制备与表征

以Fe3+改性羧甲基纤维素(mCMC)和聚乙二醇(PEG)共混为阳膜;以戊二醛改性壳聚糖(mCS)和聚乙二醇共混为阴膜,制备了mCMC-PEG/mCS-PEG双极膜.以FTIR测定了膜红外光谱,以扫描电镜观察了膜表面和界面层的形态,以TG进行膜的热重分析.测定了mCMC-PEG和mCS-PEG不同比例共混膜的含水率、离子交换容量、溶胀度,及mCMC-PEG/mCS-PEG双极膜的电性能.研究结果表明,在双极膜材料中引入亲水性的聚乙二醇后,因分子间的相容性增大,故而提高了双极膜的离子交换容量,并减小了膜的溶胀性.当CMC∶PEG质量比等于10∶1和CS∶PEG质量比等于2∶1时所制得的双极膜具有良好的电化学性能,在酸碱溶液中机械强度高、溶胀小.     

离子交换膜法合成2,2′-二氯氢化偶氮苯

应用离子交换膜法电解邻氯硝基苯合成2,2′-二氯氢化偶氮苯.讨论了电极活化条件、电流密度、电解液温度等因素对电解还原反应的影响.结果表明:在反应温度t=80℃,阴极、阳极电解液分别为10%和30%(by m ass)的NaOH溶液,电流密度4.2A/dm2条件下电解,电流效率最高,可达73%,收率为83%.     

电解四甲基碳酸氢铵制备四甲基氢氧化铵

以四甲基碳酸氢铵为原料,钛基二氧化钌为阳极,不锈钢为阴极,在H型电解槽中恒电流密度电解合成四甲基氢氧化铵,主要考察了合成工艺中离子交换膜种类、原料浓度、电解温度和电流密度对电流效率的影响。研究结果表明,当采用旭化成F4403D为阳离子交换膜,在四甲基碳酸氢铵浓度为1.41mol·L-1,电解液温度40℃～60℃,电流密度792A.m-2的条件下,电流效率可达83.5%。     

Electro-generation of TGA by Ni-mSA-mCS bipolar membrane

Ni-mSA-mCS bipolar membrane (BM) was prepared by sodium alginate (SA) and chitosan (CS),which were modified by Ca~(2 ) and glutaraldehyde as linking reagents,respectively,mSA-mCS membrane was characterized by FTIR,SEM,TG and used as a separator in the electrolysis cell to produce thioglycolic acid (TGA).The experiment results show that TGA was prepared effectively by electro-reduction of dithiodiglycolic acid (DTDGA) with the mixture of TGA and DTDGA in the cathodic chamber.The current efficiency was up to 66.7% at the room temperature (25℃) during the current density of 10 mA/cm~2.Compared with the traditional metal reduction method,the electro-reduction technology saves the zinc powder and eliminates the pollution to environment. (?)2007 Zhen Chen.Published by Elsevier B.V.on behalf of Chinese Chemical Society.All rights reserved.     

交联聚苯乙烯-丁二烯-苯乙烯双极膜的制备及其在电合成环氧丁二酸中的应用

以聚苯乙烯-丁二烯-苯乙烯（SBS）嵌段共聚物作为基膜材料,采用自由基接枝聚合反应,在SBS主链上引入丙烯酸（AA）、苯乙烯磺酸和γ-甲基丙烯酰氧基丙基三甲氧基硅烷（KH570）链段作为阳离子交换膜;引入丙烯酸二甲基胺基乙酯和KH570链段作阴离子交换膜,阴、阳离子交换膜经KH570结构中三甲氧基硅烷基团的水解缩合,得到含硅氧交联网的SBS接枝离子交换膜,用流延法制备了SBS双极膜。 测得SBS阴膜和阳膜的吸水率分别为63.9%和72.8%,SBS阴膜和阳膜的离子交换容量分别为1.51和2.71 mmol/g。 将SBS双极膜作为阴阳两室隔膜,采用钨酸钠/过钨酸钠体系由阴极间接电氧化合成了环氧丁二酸。 结果表明,以石墨为阴、阳电极,电流密度为2.0×10-2 A/cm²、50 ℃反应4 h,环氧丁二酸的产率为53.0%,电流效率为40.8%。     

Preparation of PVA-GA-CS/PVA-Fe-SA bipolar membrane and its application in electro-generation of 2,2-dimethyl-3-hydroxypropionic acid

PVA-GA-CS/PVA-Fe-SA bipolar membrane was prepared by a paste method. PVA-sodium alginate (SA) and PVA-chitosan (CS) were cross-linked by FeCl₃ and glutaraldehyde (GA), respectively. The charge densities of PVA-CS and PVA-SA solutions were determined by the colloid titration. The swelling level of bipolar membrane was in the range of 25–85%, meanwhile the permeability and the ion-exchange capacity as well as co-ion transport properties was investigated. FTIR was applied to analyze the functional groups of the bipolar membrane. Furthermore, SEM photographs of the BPM cross-section illustrated a structure that consists of an anion layer (PVA-GA-CS) and a cation layer (PVA-Fe-SA). TG analysis of PVA-GA-CS/PVA-Fe-SA bipolar membranes exhibited a good thermal stability. PVA-GA-CS/PVA-Fe-SA bipolar membranes were used as the separator in the electrolysis cell for electro-generation of 2,2-dimethyl-3-hydroxypropionic acid. The average current efficiency was 52.2%, and the highest current efficiency reached 68.9%.     

Production of a water disinfectant by membrane electrolysis of brine solution and evaluation of its quality change during the storage time

Anolyte solution produced by membrane electrolysis of NaCl solution contains a high level of available chlorine content (ACC) and other oxidizing compounds, rendering this solution a strong disinfectant property. In this paper, some process parameters affecting the anolyte production efficiency, such as total inlet flow (240–320 L/h), saline solution concentration (1.65–3.50 g/L), and the type of membrane (cation exchange, anion exchange, and bipolar membranes) were investigated in an electrolysis cell. Changes in the quality of anolytes produced at three initial concentrations of very high (ACC₁ = 816.5 mg/L), relatively high (ACC₂ = 461.5 mg/L), and medium (ACC₃ = 355.0 mg/L) during storage (from the production up to 20 weeks) were examined by adjusting the total inlet flow, saline concentrations, and membrane types. Changes in the ACC of the produced anolyte solution were generally affected by the type of membrane used in the electrolysis cell. The use of anion exchange membrane resulted in the lowest durability of anolyte quality (60–80% ACC reduction after 4 weeks of storage) and the cation exchange membrane had the highest durability (less than 40% decrease after 4 weeks of storage). In addition, changes in the pH and the oxidation–reduction potential of the anolyte were investigated during the storage period, which had a different trend depending on the type of applied membrane.     

Electrolysis of sodium chloride using composite poly(styrene-co-divinylbenzene) cation exchange membranes

Composite cation exchange membranes are prepared from cross-linked styrene-divinylbenzene copolymers for the electrolysis of sodium chloride to produce sodium hydroxide and chlorine by selective removal of sodium ions. It is prepared from a syrup of the polymer using dual initiating system and is modified with chloroacetic acid to introduce acid functional groups (COO⁻) on its surface. The effect of the modification is confirmed by FTIR, SEM, contact angle, water content, and ion exchange capacity measurements. The performance of the membrane has been evaluated in terms of current efficiency and power consumption and the effect of current density, salt concentration and flow rate on efficiency has been studied. Our membrane has an ion exchange capacity of 0.833 meq./g which is close to that of the commercially available Nafion-117 membrane having an ion exchange capacity 0.9 meq./g. The Nafion-117 used for electrodialysis of sodium sulfate has a current efficiency of around 90% and specific energy consumption of 0.1 kW/mol at 2N concentration of the salt at 1000 A/m². Our membrane used for electrodialysis of sodium chloride has a current efficiency of 93% and a power consumption of around 0.3122 kW/mol at the same concentration of salt and at a current density of 254 A/m². The two-dimensional space-charge model in cylindrical coordinates has been solved semi-analytically to obtain the effective wall potential and pore size of the membrane which are difficult to measure directly. The experimentally obtained solute flux and current density have been fitted to the model and optimum values of effective wall potential and pore diameter have been determined to be 98.5 mV and 0.8 nm, respectively.