Research On Hydrolysis Of Single Nitrile In Near-Crititcal Water

Near-critical water(NCW),which stands for pressurized liquid water under the condition of 200℃-350℃,has outstanding properties compared with water at ambient temperature and pressure.NCW not only has high ionization constant and low dielectric constant,but also can be adjusted self-physical properties by changing operating conditions.So it possesses self-acid/base catalysis and function and special solubility of organic and inorganic compounds.These unique properties indicate that NCW can act as a catalyst for organic reaction,a solvent and reactant.NCW not only acts as an acid/base catalyst instead of traditional inorganic acid or base,but also as organic solvent instead of noxious organic compounds realizing the reaction process environment friendly.Consequently,NCW plays an important role in several fields such as reaction,separation,transformation of waste and so forth.Nitrile,containing a characteristic group-cyano group,is an important organic compound in industrial chemistry.Hydrolysis of nitrile is wildly 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 on hydrolysis of nitrile in NCW,which contains other functional groups or heteroatom comparing to that does not,is relatively few and luck of systematical exploration and summary.In this dissertation,nicotinonitrile and ethyl cyanoacetate were selected as research models,and self-develeloped high-temperature and high-pressure reactor was used to investigate regularity of products yields varying with different conditions,reaction kinetic and mechanisms.Nicotinonitrile which hydrolyzes to nicotinamide and nicotinic acid in near-critical water is a representative nitrile containing pyridyl group.In this dissertation,yield of hydrolysate dependence on temperature,reaction time,reactant/water ratio(R/W) and pressure was investigated,and the hydrolysis reaction kinetic of nicotinonitrile and its intermediate nicotinamide in NCW was systematically studied.The results showed that temperature affecting the hydrolysis of nicotinonitrile more than other factors, and higher selective between nicotinonitrile and nicotinamide can be realized by changing reaction condition.Based on the assumption of first order kinetic equation, the activation energies evaluated was 55.1±1.7kJ/mol for nicotinonitrile hydrolysis and 86.5±1.9 kJ/mol for nicotinamide hydrolysis.The results showed that yield of nicotinamide was higher at relative low temperature,and the yield of nicotinic acid was higher at relative high temperature.In the research of ethyl cyanoacetate(ECT) hydrolysis,the results showed that the rate of ester group hydrolysis is faster than that of cyano group,and the final products were ethanol,acetamide,acetic acid;the mechanism of ECT was also proposed.ECT hydrolyzed to cyanoacetic acid and ethanol in the experiment condition,and then cyanoacetic acid completely decarboxylate to acetonitrile and carbon dioxide quickly. The yields of ethyl cyanoacetate hydrolysis dependence on reaction temperature, reaction time,reactant/water ratio and pressure was studied,the results showed that yield of acetic acid reached maximum 85.5%and no acetonitrile could be detected at 320℃,60min,R/W(1:500) and 15MPa.Hydrolysis of nicotinonitrile and ECT was successfully carried out in NCW which acted as catalyst and solvent avoiding environment pollution by traditional acid/base as catalyst and complicated separation of products,and also providing basic data on the research of regularity hydrolysis of nitrile in NCW.The successful application of hydrolysis nitrile containing heteroatom in NCW can be expected to hydrolyze similar compounds,as well as other types of compounds,and ultimately to promote the research of hydrolysis in NCW.