Catalytic Hydrocracking Of Coals, Their Extraction Residues And Liquefaction Residues

Hydrocracking is one of the most important reactions for direct coal liquefaction.Preparation of catalysts with high activity is the core technology in the hydrocracking process.Three solid acid catalysts (NSA, PCA/AC and TMSTFMS/AC) were prepared by impregnatingthe same volume of pentachloroantimony (PCA), trimethylsiyl trifluoromethanesulfonate(TMSTFMS), or isometric PCA and TMSTFMA into an activated carbon (AC). Through FTIR,SEM, EDS, BET, NH₃-TPD and XRD analyses reveal the strong interactions among PCA,TMSTFMA and AC in the NSA, and NSA exhibits appreciably stronger acidity than the othertwo catalysts. Di (1-naphthyl) methane (DNM) was used as a coal-related model compound toevaluate their catalytic activity. The DNM hydrocracking reactions show that Car-Calkbond inDNM can be selectively cleaved over each catalyst to afford naphthalene and1-methylnaphthalene under preesurized hydrogen at temperatures up to300oC, but as a newsolid acid, NSA is significantly more active for DNM hydrocracking than the other twocatalysts. The yield of naphthalene is appreciably higher tnan that of1-methylnaphthalene overany catalysts and the difference in yield between the two products increased with raising thereaction temperature, indicating that the1-methylnaphthalene demethylation proceeded andbecame significant at higher temperatures. DNM conversion, the product yields basicallyincreased with the increases in the NSA feed, reaction time and initial hydrogen pressure.Shengli lignite (SL), Lingwu bituminous coal (LBC), Shenmu-Fugu bituminous coal(SFBC), Lingwu extraction residue (LER), Shengli extraction residue (SER), Shengliliquefaction residue (SLR) and Heishan liquefaction residue (HLR) were selected as theanalysis samples in the catalytic hydrocracking reactions with NSA at300oC. The productswere analyzed with GC/MS and were qualitative and quantitative analysis. The non-catalytichydroconversions (NCHC) were used as blanket experiments to compare with catalytichydroconversions (CHC) over NSA. Compared with the products from NCHC and CHC, itfound that NSA can highly promote the micromolecules to release from coals. The products ofhydrocracking reactions from the coal samples can be classified as alkanes, alkenes, arenes,phenols, esters, ethers, and other species organic compounds. The yields of arenes and phenolsof products from CHC were significant higher than that from NCHC. The number of aromaticring of arenes in products from raw coals and extraction coal residues is less than5, andphenols and naphthols are the main component of phenols in products from raw coals andextraction coal residues. The contents of arenes in products from coal liquefaction residueswere much higher that that from raw coals and extraction coal residues, and the number of the aromatic rings is mainly4and more than4. The content of aliphatic hydrocarbons in theproducts from coal liquefaction residues was less than that from raw coals and extraction coalresidues. Aromatic rings are the basic structure in coal liquefaction residues. Side chains ofaliphatic hydrocarbon were removed from liquefaction residues through the process ofliquefaction.The reactions of several coal relative model compounds show that NSA has highselectivity to cleavage of C_ar–C_alk bond, and the reaction reactivity depend on the superdelocalization energy (Sr) and resonance energy value (RE) of corresponding bond. Strongelectrophilic abilities and strong acidity of the NSA facilitates heterolytical splitting of H₂to animmobile H^-adhered to the NSA surface and a mobile H⁺. The mobile H⁺which added to theipso-position of arylalkanes to lead the cleavage of C_ar–C_alk bond. The generation of H⁺is thesignificant step of the hydrocracking reactions. The NSA also has the role to promote thecleavage of ether bridge bonds.There were55figures,69tables and174references in this paper.