Construction Of Dicyclopentadiene Resin Hydrogenation Catalysts Based On Hydrotalcite-like Precursors

Dicyclopentadiene(DCPD)petroleum resin is a kind of thermoplastic polymer,which has excellent characteristics of reducing condensation and increasing viscosity,good water resistance,weather resistance,acid and alkali resistance,etc.In recent years,it has been widely used in the fields of rubber fillers,pressure sensitive adhesives,hot melt adhesives,and quick-drying printing inks.The DCPD resin obtained by the polymerization reaction contains a large number of unsaturated double bonds,which is easily substituted or oxidized with other substances,reducing its quality and grade.Catalytic hydrogenation is commonly used at home and abroad to hydrogenate unsaturated components in resins thereby improving its hue,acid value,odor and chemical stability,so as to increase their additional value.However,traditional resin hydrogenation catalysts suffer from the problems of easy loss of active components,poisoning and agglomerating of metal particles.Based on this,the hydrotalcite-like compounds are used as the precursors in this thesis to prepare monometallic Pd and bimetallic PdNi,CuNi catalysts,which are applied in the hydrogenation reaction of DCPD resin.The influence of metal-support interaction,synergistic effect and other factors on the hydrogenation reaction of resin are studied.The main research contents and results are as follows:(1)The Pd-Mg-Al ternary hydrotalcite-like precursor is successfully prepared by co-precipitation method,and Pd-MgAlO-HT catalyst with a Pd loading of 0.5 wt%is obtained by calcination and reduction.It is found that Pd-MgAlO-HT catalyst exhibits more uniform element distribution and small particle size due to the confinement effect of hydrotalcite-like precursors.The prepared catalyst is then used in the hydrogenation reaction of DCPD resin.The effects of reaction temperature,hydrogen pressure,reaction time on the hydrogenation reaction are investigated.The optimal conditions are reaction temperature of 210℃ and 5 MPa H2 pressure for 3 h.The degree of hydrogenation(DH)for DCPD resin is 96.5%.Compared with Pd/MgAlO-IM catalyst prepared by traditional impregnation method,Pd-MgAlO-HT catalyst has a strong metal-support interaction,which overcomes the problems such as metal particles easily agglomerate and active components easily lose in the reaction process.Therefore,it shows more excellent stability in the hydrogenation reaction of DCPD resin.After 5 cycles of experiments,the DH of Pd-MgAlO-HT catalyst maintains at 94.5%,while for Pd/MgAlO-IM catalyst,the DH is only 77.7%.(2)On the basis of monometallic Pd catalyst,bimetallic catalysts with different Pd/Ni mole ratios are developed by taking advantage of the controllability of metal elements in hydrotalc-like laminae.Thiophene is used as sulfur source to investigate the sulfur tolerance of the catalysts in the hydrogenation reaction of DCPD resin.The results show that Pd1Ni1-MgAlO-HT catalyst exhibits the highest hydrogenation activity under sulfur-containing conditions.The reaction conditions are further optimized to 255℃ and 10 MPa H2 pressure for 3 h.The catalyst could obtain hydrogenated DCPD resin with a DH up to 91.5%under sulfur content of 50 ppm.The electron transfer effect between Pd and Ni atoms in Pd1Ni1-MgAlO-HT catalyst is proved by XPS and other characterization methods,which weakens the adsorption capacity of the active site for sulfur element.Compared with Pd-MgAlO-HT catalyst with the same Pd content,Pd1Ni1-MgAlO-HT catalyst shows higher sulfur tolerance.(3)CuNi bimetallic catalysts with high loading are prepared by direct reduction of hydrotalcite-like precursors.The effect of the Cu/Ni mole ratio on the intrinsic catalytic activity of the catalyst is investigated using DCPD hydrogenation as a probe reaction.The results show that Cu1Ni3-Al2O3-HT catalyst has the best hydrogenation activity,and the complete conversion of DCPD can be achieved under the conditions of reaction temperature of 40℃ and 2 MPa H2 pressure within 6 h"1 LHSV.Compared with the catalysts prepared by impregnation method and mechanical mixing method with the same composition,it is found that the hydrogenation activity of Cu1Ni3-Al2O3-HT catalyst is significantly higher,which is due to its smaller particle size and stronger Cu-Ni synergistic effect.The Cu1Ni3-Al2O3-HT catalyst is then used in the hydrogenation reaction of DCPD resin under the conditions of reaction temperature of 250℃ and 8.0 MPa H2 pressure within 1.2 h-1 LHSV,a colorless resin product can be obtained,and the unsaturated bonds in the feedstock are completely hydrogenated.