Catalytic Hydroconversion Of Jiangjunmiao Bituminous Coal Over Nickel-based Solid Superacid Catalyst

Direct coal liquefaction is one of the effective ways to realize the efficient utilization of coal resources.The preparation of highly active catalysts is the key technology in coal liquefaction.In this paper,solid acid catalyst(TFMSA/PAP)was prepared by impregnating trifluoromethanesulfonic acid(TFMSA)into purified attapulgite powder(PAP),and then the nickel-based solid superacid catalyst(Ni-TFMSA/PAP)was prepared by in-situ decomposing nickel tetracarbonyl(NTC)onto TFMSA/PAP.A series of characterizations for Ni-TFMSA/PAP was performed,and the characterization results show that Ni-TFMSA/PAP possesses large spcific surface and strong acidity;and there is an interaction between TFMSA and PAP.The Ni nanoparticles with good dispersity and low loading were successfully loaded onto the surface of TFMSA/PAP.Di(1-naphthyl)methane(DNM)and diphenylpropane(DPP)were selected as the coal-related model compounds(CRMCs)to explore the mechanism of catalytic hydroconversion over Ni-TFMSA/PAP.The results exhibit that Ni-TFMSA/PAP could selectively split the Car-Calk bonds in DNM and DPP and promote hydrogenation of aromatic rings.Extracts(ES),extraction residue(ER),ethanol-soluble portion(ESP)and thermal dissolution residue(TDR)were subjected to non-catalytic hydroconversion(NCHC)and catalytic hydroconversion(CHC)at 240 °C.The soluble portions(SPs)from CHC and NCHC were analyzed with a gas chromatograph/mass spectrometer(GC/MS)to investigate the catalysis of Ni-TFMSA/PAP on ES,ER,ESP,and TDR.The results showed that the the CHC yield of ER and TDR was higher than that of NCHC,and the yield of SPs from ER became maximum increase of 20% in yield before and after catalysis,suggesting that the catalytic effect of Ni-TFMSA/PAP on ER is more significant after separating small molecules from Jiangjunmiao bituminous coal through extraction with acetone/CS2.The SPs from CHC and NCHC of ES,ER,ESP and TDR mainly consist of aliphatic hydrocarbons,arenes,phenols,esters,ketones,and small amounts of nitrogen-/sulfur-containing compounds.The contents of aliphatic hydrocarbons in SPs from CHC of ES,ER,ESP and TDR are higher than those from NCHC,and most of the aliphatic hydrocarbons in SPs from CHC are cycloalkanes,suggesting that Ni-TFMSA/PAP can promote the formation of aliphatic hydrocarbons.The contents of arenes in SPs from CHC of ES,ESP,and TDR are lower than those from NCHC,while the content of arenes in SPs from CHC of ER is higher than that from NCHC,suggesting that Ni-TFMSA/PAP could catalytically cleave the Car-Calk in coals and hydrogenate aromatics into aliphatic hydrocarbons at the same time.Diarylalkanes were selected as CRMCs to investigate the CHC of mechanisms over Ni-TFMSA/PAP.The protons released from Ni-TFMSA/PAP selectively attack on the ipso-position of aromatic ring,leading to the cleavage of Car-Calk bond.Owing to the existence of Ni,Ni-TFMSA/PAP could catalyze biatomic hydrogen transfer,resulting in the hydrogenation of aromatic rings.Based on the hydrocracking mechanism of the CRMCs and the product distributions of SPs from CHC and NCHC of coal residues,the formation mechanisms of arenes and aliphatic hydrocarbons from CHC were proposed.