Regulation Synthesis Of Calcium Cobaltate Doped With Neodymium From MOF Precursor And Production Of Phenolic Compounds By Catalytic Pyrolysis Of Lignin

As the second largest renewable resource in the world,lignin is generally discharged as cheap fuel or in the form of waste,which not only causes resource waste,but also seriously pollutes the environment.Chemical conversion of lignin into phenolic compounds with high added value can effectively realize the resource utilization of lignin.In this paper,a series of Neodymium doped Cobalt-calcium MOF precursors were synthesized by solvothermal method.Ca1-xNdxCoO3(1≥x≥0)was prepared by controlled roasting process.The morphology,crystal phase,particle size and pore structure were characterized and analyzed.The mechanism of its regeneration and recycling was explored and the results are as follows:(1)The optimum process parameters for solvothermal synthesis of CaNdCo-MOF precursor were that reaction temperature was 150℃ and the reaction time was 12 h,and the crystal morphology of CaNdCo-MOF precursor was regular.Doping coefficient of Ca1-xNdxCoO3 doped by Nd was x=0.3.The roasting mechanism is as follows:the roasting atmosphere is air,the heating rate is 6℃·min-1,the roasting temperature is 800℃,and the roasting time is 6 h.The Ca0.7Nd0.3CoO3(CNC-0.3)obtained under this condition is loose and porous.The specific surface area is 19.98 m2·g-1.(2)Kinetics of Ca0.7Nd0.3CoO3 catalyzed pyrolysis of lignin showed that:Ca0.7Nd0.3CoO3 has a significant catalytic effect on lignin.During the pyrolysis process,the weight loss rate increases by 14.58%,which is conducive to the generation of gas and liquid products.The catalytic processes of Ca0.7Nd0.3CoO3are second-order reactions and the temperature range of the secondary reactionswere 0-130℃ and 200-600℃,respectively.The activation energy of the reaction at 0-130℃ is 13.36 kJ·mol-1 and the activation energy of the reaction at 200-600℃ is 26.46 kJ·mol-1,which was 52.26 and 1.29 kJ·mol-1 lower than that of the pyrolysis of pure lignin respectively.Kinetic model of lignin pyrolysis and catalyzed pyrolysis of lignin are dα/dt=0.0064 ×(1-α)2exp(-13356/RT)and dα/dt=0.0223 ×(1α)2exp(-26461/RT)respectively.The linear regression coefficients of the obtained regression equations are above 0.9.(3)The evaluation results of Ca0.7Nd0.3CoO3catalyzed pyrolysis of lignin in a fixed bed reaction were as follows:the optimum process parameters for catalytic pyrolysis were m(CNC-0.3)/m(BL)=1:3,and the optimum temperature was 650℃.According to GC/MS analysis of the liquid products after catalytic pyrolysis of bagasse lignin,the liquid products mainly include phenols,guaiac-based,syringol,phenylketones and phenyl ethers.The selectivity of each product was 22.52 wt.%,11.37 wt.%,20.59 wt.%,13.01 wt.%and 12.57 wt.%respectively and the total selectivity of phenolic compounds was 54.48 wt.%.(4)After catalytic pyrolysis of lignin by Ca0.7Nd0.3CoO3,it was inactivated due to coking.After oxidation and regeneration,it was recycled.After five cycles,the liquid phase products yield was remained at 20%,indicating that CNC-0.3 had good activity,and the metal occurrence and morphology of catalyst did not change significantly before and after the reaction.It shows that it has good structural stability.