| Nicotinic acid, also called vitamin 83, or 3-pyridinecarboxylic acid, is asort of necessary nutritive matter in human and animal bodies. It is usedwidely in many industries of fine chemistry, such as pesticide, medicine andfood etc., and is an important medium of medical synthesis and additives offood, drink and feed. Presently, nicotinic acid is synthesized mainly by chemical oxidation,ammonia oxidation, air oxidation, electrolysis oxidation, and quinoliniumoxidation methods. Among them, electrolysis oxidation method is the mostprospective one because of its simple operation, short processing, mildreaction conditions, fine and pure products, and low pollution. 3—picoline, which is cheap and frequent, is a kind of petroleum products,and is considered to be the best feedstock of synthesizing nicotinic acid byelectrolysis oxidation. However, there are few successful industry reportsabout using 3-picoline to produce nicotinic acid by electrolysis oxidation withhigh yield. The main reason is that it is a high-tech system, and there are stillmany problems concerning the electrolytic system and the separation method.Based on literatures and former researchers' work, PbOi electrode is the mostproper anode, and tbSC^ aqueous solution is the best anodolyte. Diaphragm isvery important for an electrolysis device, and in the electrolytic oxidationsystem of 3-picoline to nicotinic acid, Ion Exchanging Membrane (IBM),which always serves as a Diaphragm, can affect the electrolytic conditions andeffectiveness greatly, and the results are poor for the electrolysis of nodiaphragm. But few researchers have systematically investigated the effect of 78various IEM in this system before. Four kinds of IEM electrolysis systemswere studied in this dissertation.1. CM-001 (Sulfonated Polythene) H+ IEM was used as the diaphragm ofthis electrolytic system. Experiments were arranged through orthogonallayout, two levels of three factors, H2SO4 (15%, 20%),3-picoline (0.5mol/L, 0.7mol/L) and anode potential (1.8V, 1.85V vs SCE),were studied. The better conditions were H2SO4 20%, 3-picoline 0.7mol/L, andanode potential 1.85V. Furthermore, the exhaustive electrolysisexperiment of larger scale was applied to study the change trends of theconcentration of H2SO4 (10%, 15%, 18%, 27%) and 3-picoline (0.5mol/L,0.6mol/L, 0.8mol/L) in anodolyte. As a result, it was found that theoptimal anodolyte, with HiSC^ 18% and 3-picoline 0.6mol/L, hadthe highest current efficiency (68.16%) and selectivity (80.65%).Under the above conditions, 3-picoline was added to the anodolyte during theelectrolysis to keep its concentration stable at the optimal value. In thisexperiment, current efficiency could be kept higher than 65%, and thehighest was 73.03%; selectivity could maintain at 80%, and the highestwas 98.76%. In all above experiments, the aqueous solution of 10% NaOHwas served as the catholyte. Compared with the system of the catholyte with10% H2SO4, whose highest current efficiency was 63.63% and selectivity was97.40%. Sulphuric acid catholyte could bring much lower cell voltage, andcould save electrical energy. For the electrolytic system with the catholyte ofNaOH, the electric energy cost 7.34J to synthesize per gram nicotinic acid,while it cost only 6.47J with the catholyte of HaSC^. It was found by analyzingthe catholyte that in this IEM system 3-picoline could penetrate from theanodic cell to the cathodic cell, but this phenomenon was not expected. The 79penetration efficiency was around 7.5%.2. Nafion902 Na+ IBM was applied as the diaphragm, the current efficiencycould reach as high as 80.52%, and the selectivity could be 95.02%. The cellvoltage was a little high at 6.0V, while the current density was low at only7.5mA/cm2. It cost 13.64J electric energy to produce per gram nicotinic acid inth...
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