Catalytic Hydroconversion Of Ningdong Lignite And Coal Model Compounds Over Cobalt-based Catalysts

In this work,Co-based catalysts,using melamine as nitrogen-doped carbon materials(NC)as a nonmetallic promoter and MCM-41 as a support,were prepared by co-impregnation method.According to the results characterized by N₂-adsorption-desorption,XRD,XPS,SEM,TEM,and NH₃-TPD,the content of nitrogen doped into the compound had a significant effect to the nature of catalyst.The Co/MCM-41-NC_1.0catalyst has the largest specific surface area,pore volume,the highest content of Co⁰,and the best dispersion of Co metal particles,when 1.0g melamine is added.The catalytic activities of catalysts were investigated for the hydrodeoxygenation(HDO)of diphenyl ether(DPE).To investigate the effect of nitrogen-doped carbon materials,the Co-/MCM-41-NC_1.0 shows high conversion of DPE and selectivity for cyclohexane,and Co-/MCM-41 catalyst was prepared and showed lower conversion(3.9%).Besides,the effects of temperature,holding time,and initial H₂ pressure on the catalytic performance of Co-/MCM-41-NC_1.0 catalyst were investigated.Co-/MCM-41-NC_1.0 catalyst showed high activity in hydrodeoxygenation(HDO)of diphenyl ether(DPE)under the optimized reaction condition(180 ^oC,1.0 MPa H₂ pressure,2 h),and the conversion of DPE and the selectivity of cyclohexane reached to 100%and 98.8%,respectively.Furthermore,the Co-/MCM-41-NC_1.0 also showed HDO activity to other lignin-related model compounds(LRMCs),such as benzyl phenyl ether,dibenzyl ether,dinaphthalene ether,anisole and 3-methoxyphenol,demonstrating its powerfully catalytic capability.NL was thermally dissolved in methanol producing soluble portions(SP)and thermal dissolution residues(TR),and then the catalytic hydroconversion of SP₃₂₀ was studied over Co/MCM-41-NC_1.0.XPS,FTIR and TG analyses results indicate that the content of aromatic carbon in TR was increased,and the stability of pyrolysis was enhanced.The result of GC/MS analyses show the relative content of oxygen-containing compounds in SP₃₂₀ including ester,phenols and ethers is higher.The ester and ethers were transformed completely and the relative content of alkanes and benzene compounds increase significantly after the catalytic hydroconversion of SP₃₂₀ over Co/MCM-41-NC_1.0,indicating the excellent catalytic activity of SP.NL was catalytic hydroconversion(CH)at different temperature over Co/MCM-41-NC_1.0catalyst.The FTIR analyses of catalytic residue(R_CH)and non-catalytic residue(R_NCH)show that the aromatic carbon content of R_CHis higher,suggesting that the Co/MCM-41-NC_1.0catalyst can break the covalent bonds and destroy the macromolecule skeleton.The FTIR analyses of SP_CH and the soluble portions non-catalytic hydroconversion(SP_NCH)indicate that the C-O bond in ethers was not detected.The results of GC/MS show the lower relative content of oxygen-containing compounds and the higher relative content of alkanes and benzene compounds in SP_NCHthan SP_CH.The results of Oribtrap MS show that the weighted average double bond equivalents(DBE)of SP_CH decreases,and O₄-O₆group compounds are transformed to O₁-O₃group compounds over Co/MCM-41-NC_1.0.In addition,the Co/MCM-41-NC_1.0catalyst has catalytic effects on desulfurization and denitrification.The paper has 29 figures,16 tables and 101 references.