ABSTRACT
The waste tire pyrolysis oil (WTPO) has been widely concerned because it's a promising recycling method of waste tires. However, the high content of nitrogen in WTPO is unfavorable to its application. In this work, nitrogen compounds in the full distillation range of a waste tire pyrolysis oil were characterized by gas chromatograph-nitrogen chemiluminescence detector (GC-NCD), gas chromatograph-mass spectrometry (GC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In the gasoline fraction of WTPO, the most abundant nitrogen compounds were benzonitrile, aniline and small molecule nitriles. In the diesel fraction of WTPO, the most abundant nitrogen compounds were benzothiazole, quinoline derivatives, p-phthalodinitrile, benzonitrile derivatives, hexadecanenitrile and octadecanenitrile. In the heavy fraction of WTPO, significant amounts of NxOy (x = 2-3 and y = 1-2) species were discovered after the separation of solvent dissolution and solid phase extraction. The molecular structures of these NxOy species were determined as amide derivatives of diphenylamine by tandem mass spectra of FT-ICR MS. Therefore, the origin of nitriles in the light fractions of WTPO was suspected as the pyrolysis of these amides in the heavy fractions. Finally, the nitrogen transformation during the pyrolysis of waste tires was suggested based on the results of quantum chemistry simulations. These results would be helpful for the treatment and removal of these undesirable nitrogen compounds in WTPO.
Subject(s)
Nitrogen Compounds , Pyrolysis , Oils , Nitriles , NitrogenABSTRACT
A two-dimensional liquid chromatographic (2D LC) system was developed for the analysis of polycyclic aromatic sulfur heterocycles (PASHs) in heavy oil. The first dimension is a ligand-exchange chromatographic column packed with a palladium chloride/silica (PdCl2-SiO2) stationary phase, while the second dimension is a Spherisorb-NH2 column. The PASHs in vacuum gas oil were enriched online, and polycyclic aromatics hydrocarbons (PAHs) were separated according to their aromatic ring numbers. These separated fractions were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and detailed molecular characterization of PASHs and PAHs was achieved. Typical molecular structures of PASHs and PAHs in these fractions could be provided, and the side chain as well as the core structures were predicted. It is significant for the feedstocks selection and optimization of the hydrodesulfurization process by using these molecular characterization information.
ABSTRACT
An analytical method for separation and identification of the saturated hydrocarbons in diesels at molecular level by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC x GC-TOF MS)was established. The saturated hydrocarbons were pre-separated from diesel samples by solid phase extraction before GC x GC-TOF MS analysis. More than 1,000 individual compounds (including paraffins, naphthenes and ole- fins) in coker diesel were tentatively identified based on NIST library search, mass spectrum resolution, boiling point distribution law and separation characteristics. Normal paraffins showed great regularity and could be identified easily through the relative position with pristane and phytane. The cyclic alkanes arranged above paraffins with the increasing number of rings. The normal alkyl cyclohexanes and cyclopentanes were well distinguished due to the difference of their polarity. Normal α-olefins which were often neglected in the past were also identified. With the support of the above-introduced identification, the distribution by structural type and carbon number were presented using peak area normalization. This analytical method was suc- cessfully used to investigate the molecular composition of saturated fractions in different diesel samples. All the results indicated that the molecular compositions of saturates in catalytic cracking diesel and coker diesel were significantly different because of the processing mechanism. This method provided technical support for the characterization of saturated hydrocar- bons in diesels and the investigation of processing mechanism.