Application Of Precious Metal In The Hydrogenation/Dehydrogenation Of Nitrogen Containing Heterocyclic Compounds

Heterocyclic compounds account for about one-third of all the organic compounds, of which heterocyclic nitrogen compounds is an important branch. Heterocyclic nitrogen compounds were often used as a structural unit within medicine and pesticide because of their unique biological activity and low toxicity. The structural modification could be easily performed for heterocyclic nitrogen compounds with the introducing of various functional groups, as well as the application in the field of organic metal catalyst and dye-sensitized solar cell. Moreover, the application of heterocyclic nitrogen compounds and their derivative are increased since used as the intermediates of medicine, agrochemical, dyestuff and other fine chemicals.The development of new energy is imminent for today’s world, as present source of energy used by people such as petroleum, natural gas and coal are non-renewable resources with limited stock on earth. As a secondary energy source, hydrogen would be a expected choice for people when they come face to face with the conventional energy crisis. Thus, the hydrogen storage system formed as the hydrogenation and dehydrogenation of heterocyclic nitrogen compounds would be an important source of hydrogen energy that can be circularly and safely used as well as easily transported.In this paper, experiment section consisted of two parts:Part â…  "catalytic hydrogenation of Indole" and Part â…¡ "catalytic dehydrogenation of Indoline". The mutual conversion of indole and indoline were studied as they belonged to the heterocyclic nitrogen compound on the one hand, but the hydrogen source generated from such conversion could be also used as hydrogen storage system that had advantages of reusable, transportation safety and convenient to use.Based on the research status in the field of catalytic selective reduction for Au catalyst, the influences of different carrier-supported Au catalysts on reaction were first studied in Part â…  "catalytic hydrogenation of Indole", and results showed that Al2O3 was the optimal carrier with highest activity. Then based on this result, other reaction conditions such as solvent, temperature, H2 pressure etc, were investigated, but a satisfactory conversion rate could not be obtained under any chose condition. Though a number of trials, it was shown that equilibrium conversion between indole and indoline with the final conversion rate of 60% was reached as the reaction time increased.In Part â…¡ "catalytic dehydrogenation of Indoline", the influences of various catalysts on this reaction were researched detailed at first, and results showed that the optimal Sel. and Conversion rate could be obtained by using Pd/C as catalyst. Then the effects of different kinds of carbon as carrier were further investigated, and Pd/XC-72 was shown to be the best choice from experimental data, the highest Sel. and conversion rate could be reached by using Pd/XC-72 as catalyst. Thus, the selective oxidation of indoline was performed by using catalyst of Pd/XC-72, and the reaction solvent, catalyst loading amount, reaction temperature and S/C value were changed to investigate the influences of different conditions on conversion rate and Sel. of oxidation reaction. The results indicated that the conversion rate was improved with the increase of reaction temperature and S/C ratio, and the optimal conversion rate up to 97% was achieved under Pd/XC-72 loading amount of 1%. Lastly, the concentration of nitric acid and mole ratio of Pd to NaBH₄ during the preparation of catalyst were studied, and the final conversion rate was found to increase with the decrease of nitric acid concentration, the highest conversion rate was obtained when the mole ratio of Pd to NaBH₄ was 1:15.On the basis of above research, the substrates were further expanded to 6-nitroindoline and tetrahydroquinoline, so as to investigate the selective dehydrogenation behavior of catalyst on them. It was found that the catalytic activity of Pd/XC-72 on dehydrogenation of 6-nitroindoline and tetrahydroquinoline was very weak.Finally, the preliminary study and discuss on recovery and reuse of catalyst were presented in this paper from the viewpoint of practical application, so as to provide basic data and theoretical guidance for application and promotion of the chemical process described in this paper.