Catalytic Hydroconversion Of Naomaohu Soluble Portion And Its Model Compounds Over Co/C@N

In this paper,a Co/C@N catalyst with excellent activity for the catalytic hydroconversion of coal model compounds?MCs?and the soluble organic species of Naomaohu subbituminous?NMH?was prepared by the one-step pyrolysis of ZIF-67.The prepared Co/C@N catalyst was systematically characterized by Nitrogen adsorption-desorption,inductively coupled plasma mass spectrometry?ICP-MS?,X-ray diffraction?XRD?,transmission electron microscope-energy dispersion chromatography?TEM-EDS?,scanning electron microscope-energy dispersion X Fluorescence spectroscopy?SEM-EDX?,X-ray photoelectron spectroscopy?XPS?,and CO₂ temperature programmed desorption?CO₂-TPD?.The results show that the prepared Co/C@N-T catalysts exhibit an irregular spherical structure with the Co contents between 26.61-32.23 wt%.During the pyrolysis of ZIF-67,N species were successfully doped in Co/C@N-T catalysts and uniformly distributed on the carbon-based surface,and the pyrolysis of the organic ligand 2-methylimidazole can partially reduce the oxide Co.The catalytic hydroconversion of benzyl phenyl ether?BPE?was used as a probe reaction to select the catalyst with the highest catalytic activity.Subsequently,the catalyst with the highest catalytic activity?Co/C@N-700?was used to catalyze the hydroconversion of phenethyl phenyl ether?PPE?,dinaphthyl ether?DNE?and other MCs containing C-O ether bonds.The effects of reaction temperature,initial hydrogen pressure and time on the catalytic hydroconversion conversion and selectivity of MCs were systematically investigated,and the catalytic hydroconversion reaction pathway of MCs was proposed combined theoretical calculations.The results show that BPE can be completely converted into toluene and cyclohexanol under the conditions of 160 ^oC,2.0 MPa and 60 min.The Co/C@N-700 catalyst has superior catalytic activity for the catalytic hydroconversion of several coal-related MCs containing C-O bonds.The catalytic hydroconversion process of the dimer MCs is dominated by the selective hydrogenolysis of C-O bonds,while the catalytic hydroconversion of the monomer MCs is mainly based on benzene ring hydrogenation.NMH was firstly thermally dissolved in methanol/toluene mixed solvent affording soluble portions and thermal dissolution residues,and then the catalytic hydroconversion of the soluble portion obtained at 320 ^oC(SP₃₂₀)was performed over Co/C@N-700 under different temperature affording its catalytic hydroconversion products?CHCs?.The results show that the yield of soluble portions increases with increasing temperature,and the yield of SP₃₂₀ is 36.46 wt%.Thermogravimetry,solid¹³C nuclear magnetic resonance(¹³C NMR)and Fourier transform infrared spectroscopy?FT-IR?analyses results show that the aromatic carbon content of the thermal dissolution residue obtained at 320 ^oC(R_TD)increases,while its carbonyl carbon content decreases compared with that of raw coal.Thermal dissolution destroyed the weak covalent bonds,hydrogen bond,carbonyl-containing structures and fatty C-O bonds in NMH,while has little damage to the condensed aromatic structure.Gas chromatography/mass spectrometry?GC/MS?analyses show that the compounds in SP₃₂₀20 mainly include alkanes,phenols,aromatic hydrocarbons,ethers and ketones.The contents of alkanes and alcohols increase significantly after the catalytic hydroconversion of SP₃₂₀ over Co/C@N-700,while the contents of phenols and aromatics decrease.The total content of oxygen-containing compounds?phenols,esters,ethers,ketones and alcohols?decreases.It indicates that the Co/C@N-700 catalyst effectively promotes the hydroconversion of aromatics and phenols in SP₃₂₀ to alkane and alcohol,which improves the quality of the soluble portions and is beneficial to its subsequent use.These findings provide a theoretical basis for the development of new catalytic hydroconversion catalysts and the mild conversion and high value-added utilization of low rank coals.The paper has 43 figures,26 tables and 151 references.