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The Performance Of Re-based Catalyst For Hydrogenation Of 1,6-adipic Acid

Posted on:2021-04-04Degree:MasterType:Thesis
Country:ChinaCandidate:X Y LiFull Text:PDF
GTID:2381330626460773Subject:Chemical engineering
Abstract/Summary:PDF Full Text Request
In recent years,researchers have found that adding 1,6-hexanediol to polyurethane products can improve the strength and hydrolysis resistance of the product.Therefore,the demand of 1,6-hexanediol is increasing internationally However,China's current production capacity is not enough to meet domestic demand,mainly relying on imports from Western developed countries.At the same time,As a new cornerstone of organic synthesis,the current production process of1,6-hexanediol is still relatively cumbersome.The common hydrogenation method of dimethyl adipate needs to esterify adipic acid,and then dimethyl diacid has to be hydrogenated.The method has obvious drawbacks such as complicated steps and waste of production resources.Therefore,in this paper,a new type of catalyst used in the one-step hydrogenation of adipic acid to produce 1,6-hexanediol was prepared.Firstly,using activated carbon pretreated with nitric acid oxidation as a carrier,a series of Irx-Rey/AC catalysts were prepared using the impregnation method,and applied to the hydrogenation of adipic acid.In order to explore the optimal conditions,we study the effects of different reaction factors such as temperature,time,pressure and other factors on the catalytic performance of the catalyst.It was found that at180oC,8 MPa H2,and 10 h,the conversion rate of adipic acid was 77%,and the selectivity of 1,6-hexanediol could reach 52%.At the same time,the catalysts were characterized by XRD,TEM,XPS,H2-TPR and H2-TPD to study the structure of the catalyst and explore its effect on the performance of catalytic hydrogenation.Through characterization analysis,it was found that the synergistic interaction between Re and Ir can not only adjust the morphology of the bimetallic particles,but also may form new metal sites.The presence of the bimetallic is beneficial to improve the dispersion of precious metal particles on the carrier.It is also conducive to reduce the size of metal particles,which is beneficial to the selective hydrogenation of adipic acid to1,6-hexanediol.In addition,in the bimetallic catalyst,the reduction of surface metal species of oxidized state can effectively suppress the significant hydrogen spillover effect in the bimetallic Ir-Re sample.With the increase of Ir species,under the same reaction conditions,the formed catalyst is more difficult to remove hydrogen molecules,indicating that the interaction between the metal on the surface and the hydrogen molecules is stronger.Secondly,in order to investigate the effect of Ir and Re bimetals supported by different supports on the performance of the catalyst,a series of Ir1Re1/M?M=SBA-15,CNT,Al2O3,AC?catalysts were prepared for the adipic acid aqueous hydrogenation reaction.After experiments,it was found that Ir1Re1/AC catalyst using activated carbon pretreated with nitric acid oxidation as a carrier for catalytic hydrogenation reaction had the highest conversion rate of adipic acid and1,6-hexanediol.Under the conditions of 8 MPa H2,16 h and 180oC,the conversion rate of adipic acid reached 99%,and the selectivity of 1,6-hexanediol was 59%.At the same time,XRD,TEM and NH3-TPD characterization tests were carried out on all catalysts.It was found that the carrier carbon nanotubes of Ir1Re1/CNT maintained the original morphology in morphology,which indicated that during the preparation process of the catalyst,it does not affect its morphology and characteristics,and no aggregation occurs on the surface metal.The small number of particles observed on the surface of Ir1Re1/SBA-15 catalyst is mainly due to the sintering of particles during heat treatment.In fact,the acidity of carbon materials is related to the oxygen groups on the surface,which may cause the carrier to interact with the metal precursor,and cause the metal substances to be finely dispersed on the surface of the carrier,thereby improving their catalytic ability.
Keywords/Search Tags:Adipic acid, 1,6-hexanediol, Activated carbon, Hydrogenation reaction, Ir-Re catalyst
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