| As an important chemical intermediate,sebacic acid is widely used in the manufacture of high temperature lubricants,engineering plastics,artificial flavors,resins,fibers,cosmetics and etc.In current industrial production,sebacic acid is mainly produced by alkali fusion of castor oil using phenol or cresol as a thinning agent,which not only results in a low quality and high color number of the product,but also increases the workload for the treatment of phenol-containing wastewater.Furthermore,the by-product glycerol,produced by castor oil during the cracking process,can decompose into toxic acrolein at high temperatures,thereby causing environmental pollution.Therefore,in order to improve the yield and quality of the product,it is necessary to explore a brand-new and green approach for producing sebacic acid.Solid-phase cleavage can effectively avoid the introduction of thinning agent such as phenol or cresol into the reaction system.Sodium ricinoleate can be obtained by saponification of castor oil,and sufficiently mixed with alkali and catalyst,then cracking at high temperatures to afford sebacic acid.In solid-phase cleavage,tubular furnace was used as the reactor,and the optimal reaction parameters for obtaining high yield of sebacic acid were as follows:1%ferric oxide as catalyst,5:4 mass ratio of sodium ricinoleate/potassium hydroxide,1 h reaction time,270?reaction time,0.09 MPa vacuum degree.Under these reaction conditions,70.2%yield in sebacic acid with a purity of 98.1%can be obtained.As a green process without thinning agent for preparing sebacic acid,solid-phase cleavage can shorten the reaction time significantly.The improvement in traditional alkali fusion of castor oil can effectively enhance the yield and quality of sebacic acid.The glycerol in castor oil can be separated by transesterification or saponification and acidification of castor oil to obtain methyl ricinoleate or ricinoleic acid,respectively.Castor oil was replaced by its two derivatives to carry out alkali fusion,and the reaction parameters for obtaining high yield of sebacic acid were optimized.The experimental results illustrated that 1%lead?IV?oxide showed the best catalytic performance,and the optimal oil/sodium hydroxide mass ratio was 15:14.In addition,3 h and 280?were considered as the most suitable reaction time and reaction temperature,respectively.When using methyl ricinoleate as the raw material,a maximum yield in sebacic acid of 77.7%(purity 97.8%;Pb content 0.34 mg·kg-1)can be obtained.As for ricinoleic acid,the maximum yield in sebacic acid was 78.6%(purity 98.0%;Pb content 0.55 mg·kg-1).The side reactions can be avoided due to the pre-separation of glycerol.Compared with alkali fusion of castor oil,the reaction time was reduced by 2 h and the yield of sebacic acid was increased by approximately 10%when using its derivatives as the raw material.In addition,the quality of the product was also improved.In order to reduce the platinum-cobalt color of sebacic acid,monosodium sebacate obtained by the first acidification was refined by extraction and adsorption.Firstly,petroleum ether was used as extractant for extracting a small amount of fatty acid dissolving in water.When the usage amount of petroleum ether was 30 wt%of the feed liquid,the extraction temperature was 80?,and the extraction time was 20 min,the color number of sebacic acid can be reduced to lower than 15.The other impurities in feed liquid was further treated by adsorption using activated carbon.When its additive amount was 1 wt%of the feed liquid,the color number of the product was further reduced to lower than 10,and the purity reached99.7%.The combination of extraction and adsorption effectively improves the quality of the product,which provides a guiding significance for the production of sebacic acid with high purity. |
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