| Plastic products are prone to aging due to sunlight.Therefore,it is often necessary to add UV absorbers to prevent plastic aging.Because of its low-toxicity and good stability,Benzotriazole compounds UV absorbent is commonly used as a plastic anti-aging agent.The traditional synthetic process of benzotriazole compounds UV absorbent is backward and more environmental pollution.In order to solve the problems such as the backwardness of synthetic process for UV absorbents and the large pollution of the environment,a new catalyst has been prepared in this thesis for catalytic reduction of azo compounds by hydrogen or hydrazine.The carbon supported nickel catalyst was successfully prepared in experiments and was applied to the catalytic hydrogenation reduction of azo dye.The effects of various process conditions on the reaction were explored.Under the condition:azo dye 0.01 mol,catalyst 200 mg,reaction temperature 353K,sodium hydroxide 2 g,water 30 ml,ethanol 30 ml,pressure 1.5 MPa,stirring speed 800 r.min-1,reaction time 30 min,the yield of UV-P is 92.3%,the purity of UV-P is 99.6%.The catalyst life test showed that it could be cycle used over 21 times with UV-P high yield and purity.Because of the inflammable and explosive nature of hydrogen,the experiment uses hydrated instead of hydrogen for the preparation of UV-P.The carbon supported nickel catalyst prepared in this experiment was used for reduction of azo dye by hydrazine.The experiments explored effects of process conditions on reactions.The results of experiments showed that the catalyst was the main factor affecting yield of UV-P.CoMPared to the traditional preparation processes for UV-P used at present,the reaction in this thesis reduces the emission of metal salt and sulphide,etc.,and has better environmental benefits.The mechanism of hydrazine reduction of azo dye for UV-P is explored.The results of study show that the preparation reaction of UV-P by azo dye is carried out in principle with step-by-step,whether by two-step or one-step method.The first step is that all the azo dye is reduced to nitrogen oxides,and then the nitrogen oxides can begin to reduce to generate UV-P. |
