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Studies On Several Organic Synthesis Reactions In Near-critical Water

Posted on:2006-05-27Degree:MasterType:Thesis
Country:ChinaCandidate:F GaoFull Text:PDF
GTID:2121360152971785Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
Near-critical water can serve as a reactive medium for organic synthesis as a result of the changes that occur to its chemical and physical properties at elevated temperature. It has already shown its abilities to replace for many toxic organic solvents, and ability to catalyze reactions that traditionally require the addition of acid or base. The task of this work was to gain a better understanding of several organic synthesis reactions in near-critical water.An environmentally-benign process for synthesis of benzaldehyde in near-critical water without any catalyst was proposed. The kinetics of non-catalyzed hydrolysis of cinnamaldehyde in water at 15 MPa and temperatures from 240 ℃ to 320℃ was investigated. The activation energy evaluated was 59.8 kJ/mol. Not only was the process proposed environmentally friendly, but also the benzaldehyde remained its natural property as only water was needed in the process.Effects of temperature and residence time on benzaldehyde conversion wasinvestigated for temperatures from 260℃ to 310℃ and pressure at 15MPa. Theevaluated activation energy of benzaldehyde decomposition was 71.1 kJ/mol. The optimized reaction conditions was deduced from experimental data.The acceleration of base-catalyzed reactions in near-critical water by the addition of ammonia to the reaction medium was reported. The reaction examined was the hydrolysis of cinnamaldehyde to form benzaldehyde. The rate of hydrolysis was more quickly when ammonia was added to the aqueous medium. The kinetics of hydrolysis of cinnamaldehyde in ammonia at 15 MPa and temperatures from 220 ℃ to 300℃ was investigated. The activation energy evaluated was 58.6 kJ/mol.The kinetics of non-catalyzed pinacol rearrangement in near-critical water at 15MPa and temperatures from 180℃ to 220 ℃ was investigated. The activation energy evaluated was 176.4kJ/mol.
Keywords/Search Tags:near-critical water, cinnamaldehyde, benzaldehyde, ammonia, pinacol, pinacolone, hydrolysis, rearrangement, kinetics
PDF Full Text Request
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