Preparation And Application Of Catalysts For The Oxidation Of Fatty Alcohol Polyoxyethylene Ether

Alcohol-ether carboxylates(AEC)are a new type of anionic surfactants,which have the characteristics of safety,low toxicity,easy biodegradation,low surface tension and good compatibility with other surfactants.The research on the synthesis of AEC has been carried out for more than 10 years in China.The main technique route to produce AEC is the reaction of sodium chloroacetate and fatty alcohol polyoxyethylene ether.However,due to the low quality,the application and promotion of the AEC products are limited.Compared with the traditional process,the catalytic oxidation using precious metals has attracted widespread attention due to the advantages of shorter process flow and lower equipment requirements,which can be proceeded in continuous production and obtain high-purity products..Based on the above background,in this thesis Pd/C catalysts were prepared by a developed impregnation-reduction method,which exhibit excellent catalytic performances for the direct oxidation of fatty alcohol polyoxyethylene ether to AEC.The aim of this work is to prepare AEC-9H by catalytic oxidation of AEO-9.The preliminary tests of various catalysts with different metals as active centers,including cobalt based catalysts derived from Cobalt-based MOFs and commercial Pd/C,indicate that metal palladium has higher catalytic activity for the oxidation of AEO-9.Then,the optimal reaction conditions were determined by orthogonal test.In order to address the stability issue of palladium catalysts,the preparation technics are investigated,including carrier pretreatment,auxiliary doping of active metal,and the reduction process.It was found that the dispersion process rather than the additives has significant effect on improving the recycling stability of the catalysts.The characterization results of TEM,XRD,and H2-TPR show that the sodium bicarbonate will be mixed in the precipitatione when sodium carbonate was used for dispersion,resulting in poor stability of the obtained catalyst.The optimal preparation process is determined as following:activated carbon pre-treated by 8%nitric acid is used as the carrier,which is dispersed in a chloropallanic acid solution at room temperature for 3 h,then the pH of the system is adjusted to 13-14 by sodium hydroxide solution.The palladium in the impregnation solution is pre-dispersed,and then reduced by sodium borohydride.TEM characterization confirmed that Pd nanoparticles with an average particle size of 3.3 nm were yielded.The assynthesized Pd/C materials showed excellent catalytic performance in the oxidation of AEO-9.The XRD,TEM,and BET characterization results of the catalyst before and after 10 cycles of reaction demonstrate the good recycling stability of the catalyst under the investigated conditions.