Hydrolysis Of Nitriles In Near-critical Water

Near-Critical Water(NCW),which stands for the pressurized liquid water under the condition of 200～350℃.The outstanding properties of NCW comparing to that of water at ambient temperature and pressure are its high ionization constant and low dielectric constant,so it possesses self-acid/base catalysis function,special solubility of organics and inorganics and self-physical properties adjustability.These unique properties indicate that NCW can act as a catalyst for organic reactions,also as a solvent and reactant.Acid or base catalyzed reactions can occur without of acid or base catalysts because of the function of NCW.NCW can also instead of organic solvents utilized heavily and realize the reaction process environment friendly. Consequently,NCW plays an important role in several fields such as reaction, separation,resource of trash and so forth.Nitrile is a kind of organic compounds containing cyano group,as a starting material to synthesize a series of amine,acid and polymer,the hydrolysis reactions of nitriles have been widely applied in plentiful organic synthesis such as amino acid, amide,carboxylic acid and its derivatives,which occupy an extremely important position in organic synthesis.Up to now,the research of nitriles hydrolysis in near-critical water is relatively few and lack of systematical exploration and summary. In this dissertation,two typical nitriles compounds,phenylacetonitrile and 3-cyanopyridine,as research objects are selected,and self-developed high-temperature and high-pressure reactor is used to investigate the reaction kinetics of nitriles hydrolysis reactions in NCW,and then the rule of nitriles hydrolysis in NCW is explored.In the non-catalytic hydrolysis reaction of phenylacetonitrile in NCW,after investigating the repeatability of experiment data and the influence of initial concentration of phenylacetonitrile on reaction,the hydrolysis reaction kinetics of phenylacetonitrile and its intermediate phenylacetamide in NCW was systematically studied in the temperature range from 523.15K to 563.15K.The results showed that the hydrolysis of phenylacetonitrile is a typical consecutive reaction which involves the formation of phenylacetamide as an intermediate product,and gives phenylacetic acid as the final product with very high selectivity.Based on the assumption of first order kinetics equation,the activation energies evaluated were 64.4 kJ·mol^-1for phenylacetonitrile hydrolysis and 82.4 kJ·mol^-1for phenylacetamide hydrolysis.We took the similar methods to carry out the non-catalytic hydrolysis reaction of 3-cyanopyridine in NCW and measure kinetics data in the temperature range from 483.15K to 523.15K.The results showed that the influence of temperature on the hydrolysis of 3-cyanopyridine is important and selective production of nicotinamide or nicotinic acid is possible at different reaction conditions.Based on the assumption of first order kinetics equation,the activation energies evaluated were 65.2 kJ·mol^-1 for 3-cyanopyridine hydrolysis and 85.8 kJ·mol^-1for nicotinamide hydrolysis.Based on the research of phenylacetonitrile and 3-cyanopyridine hydrolysis,we combined with nitriles hydrolysis reported in literature to summarize the reaction regularity of nitriles in NCW.At present,it is far from comprehensive about the research of nitriles hydrolysis in NCW,so further exploration of reaction mechanism needs more deep investigation.NCW acts as solvent and catalyst and can replace the traditional acid/base catalyst effect for the rich concentration of H⁺ and OH^- self-ionized by water.NCW process could also eliminate production of salts that results from the neutralization of acids used in conventional separation,solving a significant environment problem.The pioneer investigation of these two kinds of reactions can not only provide important basic data for other kinds of hydrolysis reactions of nitriles as well as further study the rule of nitriles hydrolysis in near-critical water,but also offer valuable reference to the modification of polymer with cyano-groups in NCW.