Properties And Application Of Copper-based Catalysts Prepared By Complexation Of Biomass Derivatives

With the acceleration of industrialization and the shortage of fossil energy supply,people gradually focus on biomass resources.Biomass reserves are huge and widely distributed in China.In the long run,the development of biomass resources is not only beneficial to the environment,but also an important way to ensure sustainable development.Copper-based catalyst is the best choice because of its high selectivity,high activity,few by-products and low cost.Therefore,in this paper,a series of copper-based catalysts were prepared by complexation of biomass derivatives and used in the hydrogenation of oxalate（DMO）to ethylene glycol（EG）.Combined with N₂ isothermal adsorption and desorption,H₂ temperature programmed reduction,Raman spectroscopy,X-ray diffraction,NH₃/CO₂ probe molecular chemisorption,transmission electron microscope and scanning electron microscope,etc.,the catalytic activity of the catalyst was evaluated by fixed-bed reactor.The effects of Cu content,calcination temperature and type of complexing agent on the particle morphology,size and catalytic performance of the catalyst were discussed.（1）Cu O/Zr O₂ catalyst（w CZ）and Cu O-La₂O₃/Zr O₂ catalyst（w CLZ）,with different Cu content were prepared by acetic acid complexation method and applied to the hydrogenation of DMO to EG.It was found that the catalytic performance of w CZ increases at first and then decreases with the increase of copper content.When the Cu content was 50%（50CZ）,the catalyst shows a layered structure,showing excellent performance,such as the conversion frequency（TOF）can reach 134.1.When WLHSV=0.8 h^-1,the DMO conversion rate can reach 100%and the selectivity of EG is95.7%;when WLHSV=1.5 h^-1,the conversion rate of DMO decreases slightly to 98.4%,the selectivity of EG reaches the maximum value of 97.7%.Further experimental studies show that the introduction of La can inhibit the crystal transformation of the carrier caused by high temperature calcination,improve the dispersion of Cu and the activation of hydrogen,and increase the specific surface area and pore volume of the catalyst.（2）Cu O/Zr O₂ catalyst（32CZT）and Cu O-La₂O₃/Zr O₂ catalyst（32CLZT）were prepared by acetic acid complexation method and salicylic acid complexation method at different calcination temperatures,and applied to the hydrogenation of DMO to EG.It was found that the specific surface area of 32CZT prepared by acetic acid complexation method showed a volcanic curve with the increase of calcination temperature,and the specific surface area was the largest and the catalytic performance was the best when the calcination temperature was 550^oC（32CZ550）.At WLHSV=0.5h^-1,the DMO conversion rate is about 97.7%.The EG selectivity is as high as 95.3%;when the WLHSV is increased to 1.0 h^-1,the EG conversion rate is reduced to 86.3%,but the EG selectivity can still be maintained at a high value（92.6%）.Further experimental study found that the adsorption/activation ability of H₂ on the surface of Cu O-La₂O₃/Zr O₂ catalyst prepared by salicylic acid complexation increased obviously with the increase of calcination temperature.It had a linear relationship with the selectivity of ethylene glycol,which was due to the enhanced of the synergistic effect with Cu after the crystal phase of the carrier was transformed into monoclinic phase.In addition,the increase of calcination temperature significantly reduced the surface acidity/basicity and the occurrence of side reactions.The catalytic performance of 32CLZT catalyst showed a volcanic trend with the calcination temperature,and the catalytic performance is the best when the calcination temperature is 700^oC（32CLZ700）.Under the same reaction conditions,the conversion rate of DMO is about 97%,and the selectivity of EG can reach 98%,and the activity is stable in not less than 100 h.（3）Cu O-La₂O₃/Si O₂ catalyst was prepared by equal volume impregnation method and applied to the hydrogenation of DMO to EG.Using tetramethyl ammonium hydroxide,ammonia and glycine as ammonia（ammonium）sources,the effects of p H changes in solution caused by different ammonia（ammonium）sources on the structure and activity of the prepared catalysts were studied.It was found that the addition of ammonia source can not only complex metal ions,but also adjust the acidity and basicity of the solution,thus change the dispersion and sintering resistance of Cu active components in the catalyst,and affect the activity and stability of the catalyst.Among them,the hydrogenation performance of the catalyst prepared from ammonia water is the best,and its DMO conversion and EG selectivity can reach 98%and 97%respectively,and remain stable after 200 h of continuous reaction.（4）Cu O-La₂O₃/Zr O₂ catalyst was prepared by amino acid complexing method,and glycine,aspartic acid,L-glutamic acid and L-leucine were used as complexing agents.It was found that the Cu O-La₂O₃/Zr O₂ catalyst prepared with L-glutamic acid as complexing agent had the best performance.It has high Cu dispersion and exposed surface area,excellent texture properties,high surface H₂ adsorption and activation properties and abundant surface acid/basic sites,which give the catalyst good catalytic performance in related reactions.