Hydrothermal Synthesis Of Ni Based Oxides And Their Catalytic Depolymerization Of Calcium Lignosulfonate

In this paper,a series of Ni O,Mg Al O_xand Ni Mg Al O_xwere prepared by hydrothermal synthesis.The crystal phase,morphology,functional group and specific surface area of Ni O,Mg Al O_xand Ni Mg Al O_xwere analyzed by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,infrared spectroscopy（FT-IR）and specific surface area analysis（BET）.The hydrothermal depolymerization performance of calcium lignosulfonate was evaluated in a high temperature and high pressure reactor.The results are as follows:（1）By optimizing the preparation process of Ni Mg Al-DHs,the optimal process parameters are:solution p H=12,crystallization time 24 h,crystallization temperature180°C,n(M²⁺)/n(M³⁺)=3,crystallinity of 85.12%,particle size of 100-300 nm.（2）The best calcination temperature of Ni Mg Al-DHs is 600°C,and the calcination time is 6 h.The composite metal oxide Ni Mg Al O_xwith catalytic effect is obtained.At this time,the metal oxide has good dispersivity and specific surface area of 104.52 m²/g,pore volume of 0.81 cm³/g,pore diameter of 31.12 nm.（3）A catalytic system for the depolymerization of calcium lignosulfonate was constructed with the active metal Ni O,solid alkali oxide Mg Al O_xand composite metal oxide Ni Mg Al O_xas catalysts.The depolymerization effect was examined under the conditions of 270°C,4 h,60 vol.%ethanol,m（Cat）/m（CLS）=0.5:1.The results showed that the yields of liquid phase products were 60.72%and 67.86%respectively,and the selectivity of phenols was 51.69%and 64.95%respectively,using Ni O and Mg Al O_xas catalysts.The selectivity of 2,6-dimethoxyphenol（S）in liquid phase products was 12.82%and 12.71%,respectively.When Ni Mg Al O_xwas used as catalyst,the yield of liquid-phase product was 72.45%,and the selectivity of phenols was 75.87%.Among them,the selectivity of 2-methoxyphenol（G）was as high as18.93%.（4）After four depolymerization regeneration cycles,the yield of composite metal oxide Ni Mg Al O_xin liquid phase is still 64.36%,and its selectivity is 52.87%.After regeneration,it still has good crystal phase and structure stability,which ensures good catalytic activity.