Effect Of Nitrogen Compounds And Aromatics Of Feedstocks On FCC Reaction Performance

The nitrogen compounds and aromatics were separated from Coker gas oil(CGO)with a combination separation method of ion-exchange chromatography,coordination chromatography and adsorption chromatography,and then are characterized by FT-IR,Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry(ESI FT-ICT MS)and comprehensive two-dimensional gas chromatography with mass spectrometry(GC×GC-TOF MS)in this paper.In accordance with the characterization results,the model compounds were determined.Combined with molecular simulation,the adsorption and diffusion properties of these model compounds in the molecular sieve models were studied.What's more,through a heavy oil micro fixed-bed reactor,the FCC reaction performance of the feedstocks with these model compounds were investigated.The separation and characterization results of the nitrogen compunds and aromatics showed that the nitrogen compounds in CGO were mainly N1 class,and these basic nitrogen compounds were mainly derivatives of pyridine,quinoline and acridine or phenanthridine with alkyl and cycloalkyl chains.Non-basic nitrogen compounds were mainly derivatives of carbarzole,benzocarbarzole and dibenzo-carbazole.The content of tricyclic and aromatics with more than three rings in CGO was up to 68.53w%,including derivatives of perylene,benzo(k)fluoranthene,pyrene,benzoanthracene,chrysene,fluorine,anthracene,phenanthrene and phenylnaphthalene etc.Two rings aromatics were mainly naphthalene,biphenyl and indane etc,with the same content of 15-16w% as monocyclic aromatics.The molecular simulation results of adsorption and diffusion showed that the adsorption capacity of FAU zeolites to nitrogen compounds and aromatics was larger than the MFI zeolites.Increasing the temperature could restrain the adsorption of FAU zeolites to nitrogen compounds and aromatics,but the effect was poor in MFI zeolites.And the influence of Si/Al on the adsorption in MFI zeolites was obvious.In addition,both the side chains and the aromatic rings in the molecules made the diffusion coefficients decrease,and the aromatic rings affect more seriously.An increase in the temperature would cause the diffusion coefficients become larger,however the increasing extent of nitrogen compunds and aromatics was different.The results of FCC reaction performance of feedstocks with model compounds showed that the toxic effects of large basic nitrogen compounds on the USY zeolite based catalyst LVR-60 R was strong,which would lead to a decline in conversion and gasoline yield,and a significantly increase in coke yield.While small basic nitrogen compounds would have a serious impact on the ZSM-5 zeolite based catalyst LTB-2,which would result in the conversion and LPG yield dropping significantly,but the effect on the coke yield was not serious.The poison ability of non-basic nitrogen compounds was weaker,compared with molecules of similar molecular weight.The influence of aromatics on FCC reaction conversion and yield of dry gas,LPG and coke was similar to the basic nitrogen compounds,but the effect was weaker than basic nitrogen compounds.