Study on the Design of Ionic Liquids and Its Extraction Experiment for the Nitrogen Heterocyclic Components of Coal Pyrolysis Oil
Author:Zhang Lian Zheng
Coal plays a very important position in china’s enery structure.As a clean technology for utilizing coal resources,coal pyrolysis can produce large amounts of pyrolysis oil which is the source of many important high value-added products.And indole,carbazole,pyridine,quinoline and thi-ophene etc.irreplaceable heteroatom compounds for the petrochemical products could be separated from the pyrolysis oil.But the separation technology of coal pyrolysis oil limits its depth development and utiliza-tion.In the view of the present situation of deep utilization of coal pyrol-ysis oil in china,this thesis aims at the efficient utilization of nitrogenous compounds(N-compounds)from coal pyrolysis oil.The design of the ionic liquid extractant and the application of extraction and separation of coal pyrolysis oil were carried out by using the green and novel ionic liq-uids(ILs).And a design method for the extractant of N-compounds in coal pyrolysis oil was established which solved the problem of extractant se-lection caused by many anions,cations type and its combination method.Then,based on the experiment,the separation mechanism was explored to provide the basis for the separation of N-compounds.The main research contents are lised as follows:(1)The research focused on the extraction of N-compounds by ILs in the micro molecular viewpoint.The micro interaction between the N-com-pounds and ILs were explored by quantum chemistry calculation and mo-lecular simulation.As results,the mechanism of N-compounds extracted by ILs could be determined.Then,the microstructures and the mechanism of the one-to-one model system were obtained.And the main factors of influencing the separation process by the ILs were determined,which could provide the the theoretical basis for the design of the ILs extractant.(2)Based on the COSMO-SAC model,the structure database of 39 kinds of cations and 29 kinds of anions were established.Then,the design method of ionic liquid extractants was proposed,which solved the con-ventional selection of the extractants are mainly depended on the experi-ences.Based on the analysis of the σ-profile,the effects of different types of N-compounds,the main structure of the cations,the carbon chain struc-ture of cationic alkyl substituent,the kinds and polarity of the substituent,and different types of anions to the influence of extraction mechanism were explored.Thus,the relations between different molerculars and ef-fects of shielding charge distribution could be systemically analyzed.For the difference between neutral and basic N-compounds,22 kinds of cati-ons and 19 anions were selected,which can be combined into 418 kinds of ILs,as the initial structures of neutral N-compounds extractants,and 15 kinds of cations and 8 anions were selected,which can be combined into 120 kinds of ILs,as the initial structures of basic N-compounds extractants.Then,the distribution coefficiency(D),selectivity(S),extractant loss(SL)and solvent solubility(SP)parameters of the above ILs at 298.15K were calculated according to the established method,and 10 kinds of ILs were selected to do the following extraction experiment.(3)The extraction and separation experiments of the N-compounds in the coal pyrolysis oil were carried out by using 10 designed ionic liquid extractants.The extraction temperature,extraction time,mass ratio of ILs to model oil and N-initial concentration were compared in the neutral and basic N-compounds’ separation process.The best extraction conditions of the ILs and the mechanism of extraction were obtained.And the extraction efficiency was both higher than the reported extractants for the neutral and basic N-compounds.Meanwhile,the recovery of the extractants and its recycling times were also investigated.After many times usage,the ionic liquid extractants were still maintained good extraction performance.Based on this,two separation processes were proposed,which provided reference for the green separation of N-compounds in coal pyrolysis oil.(4)The liquid-liquid phase equilibrium for 6 ILs and components of pyridine and indole,respectively,were studied experimentally.The van de Waals volume(r)and van de Waals surface area(q)parameters were cal-culated by the quantum calculation.The parameters of the models and the interaction parameters were obtained by using the activity coefficient models.The calculated binary interaction parameters can be used to guide the process design and optimization of the separation process.Meanwhile,the separation ability for the neutral and basic N-compounds were inves-tigated by calculating the distribution coefficient and selectivity of the cor-responding systems.