Molecular Characterization of C_(9+)Aromatics in Gasoline by Gas Chromatography-Mass Spectrometry

The comprehensive characterization of heavy aromatic hydrocarbons in gasoline is important to optimize the blending process and understand the correlation between aromatics content and engine particulate emissions.However,most current analysis methods can only provide the composition of C_(8)/C_(8-) aromatics.In this study,a simple and fast gas chromatography-mass spectrometry(GC-MS)method to identify and quantify C_(9+)aromatics in gasoline was developed.A selected ion monitoring model was employed to eliminate interference from non-aromatic compounds in the detection of target compounds,as well as that between target compounds with different molecular formulas.The identification of C_(9+)aromatics was based on the retention time of model compounds,combined with characteristic mass fragment ions,boiling points,and retention indexes.Seventy-nine C_(9)–C_(12)aromatic compounds were quantified based on the calibration of representative model compounds,and the method demonstrated good linearity,and high accuracy and precision.Furthermore,the developed methodology was successfully applied to the analysis of gasoline fractions from the reforming,pyrolysis,straight-run,delayed coking,and catalytic cracking processes,as well as commercial gasolines.The results showed that C_(9)aromatics were the predominant aromatics in all gasoline samples,followed by C10 aromatics.Alkylbenzenes such as C_(9)H_(12)and C_(10)H_(14)were the main components in the reforming,straight-run,delayed coking,and catalytic cracking gasoline fractions,as well as in the commercial gasolines,in which 1,2,4-trimethylbenzene and 3-ethyltoluene were dominant;in contrast,aromatics with higher degrees of unsaturation such as indene were the most abundant aromatics in the pyrolysis gasoline fraction.

Synthesis, characterization and catalytic properties of mesoporous MCM-48 containing zeolite secondary building units

Mesoporous aluminosilicate MCM-48 containing zeolite secondary building units in the pore wall has been synthesized in alkaline media with a two-step procedure.The aluminosilicate precursors comprising zeolite secondary building units were first synthesized by carefully controlling reaction conditions and then were assembled using co-templates of gemini surfactant[C18H37N(CH3)2(CH2)3-N(CH3)2C18H37]2+(18-3-18)and triethanolamine(TEA).X-ray Diffraction(XRD)patterns of the as-made samples indicated that highly ordered mesostructured MCM-48 was formed.Transmission Electron Microscopy(TEM)images further verified the formation of MCM-48 with uniform cubic pore channel system having the pore opening diameter of about 25Å.Compared with the conventionally synthesized MCM-48,the as-synthesized MCM-48 sample showed an adsorption band at 520–600 cm-1 in its FT-IR spectrum,which was assigned to five-membered ring vibration from zeolite structure.This suggested the presence of zeolite building units in the pore wall.N2 adsorption data showed that the material had a much higher specific surface area(1200 m2/g)than the conventional MCM-48(1100 m2/g).Finally,the cat-alytic performance of the as-made MCM-48 was evaluated by hydrogenation dealkylation reaction of heavy aromatic hydrocarbons.Catalytic results showed that the as-made MCM-48 catalyst exhibited higher conversion than the con-ventional MCM-48 catalyst.The as-made mesostructured MCM-48 may have a potential catalytic application in the conversion of bulky molecules.