Catalytic Preparation And Properties Of Turpentine-based Biomass High Density Fuels

With the increasingly severe fossil energy shortage,it is urgent to develop biomass high-energy-density fuel(HEDF)with higher energy,higher stability and more greener production process to replace the petroleum-based products to satisfy the development of aerospace technology.Natural Biomass Turpentine is a potential resource to prepare biomass HEDF due to containing much rigid polycyclic hydrocarbon structure C10-C15 in the molecular constituent structure.In this paper,the dimerization / isomerization of α-pinene under acid catalysis was studied.The products were anlysed quantitatively and qualitatively by gas chromatography(GC)and gas-mass spectrometry(GC-MS).Besides,the production distributes and reaction mechanisms were also studied and discussed.The research provided theoretical basis for turpentine the prepare biomass HEDF directly.The common ionic liquids were synthesized and applied to catalyze the dimerization / isomerization of α-pinene.It was found that the catalytic acidity had great influence on the reaction.Both the Br?nsted acid,the Lewis acid and the Br?nsted-Leisic double acid catalyst had a direct effect on the reaction.The stronger the acid strength was,the higher selectivity of α-pinene dimerization.Simple Br?nsted acid or Lewis acid could initiate the reaction individually.The double acid catalyst could significantly increase the α-pinene reactivity.Though the traditional double acid ionic liquids,[MIMPS].2AlCl3,for example had high catalytic activity and dimerization selectivity,the catalysts existed problems such as easy hydrolysis,poor reproducibility of preparation,and formation of hydration by-products,which limited the wide application to produce biomass HEDF.The environment-friendly Keggin type phosphotungstic acid was used to catalyze the dimerization / isomerization of α-pinene and the effects of different activation temperature and activation time on the acidity and catalytic performance of phosphotungstic acid were investigated.The acidity and structure of phosphotungstic acid were characterized by potentiometric titration,thermogravimetry(TG),infrared spectroscopy(FT-IR)and X-ray powder diffraction(XRD).The results showed that the activated phosphotungstic acid had quite high conversion of α-pinene and selectivity of dimerization.The Keggin structure of the catalystic did not change before and after the reaction.Under the optimized conditions of activation temperature 200°C,activation time 10 h,catalyst dosage 9 wt%,toluene 10 mL,α-pinene 10 m L,reaction time 10 h and reaction temperature 90°C,the conversion of α-pinene was 99.9%,and the selectivity of dimerizations reached to 57.6%.The catalyst still had a good catalytic activity after reused for 5 times.Based on the composition of the ionic liquid structure,the heteropoly phosphotungstate was used as the anion while N-methylimidazole and triethylamine were used as the organic cation skeleton,with which sulfonic acid group with Br?nsted acidity was introduced.Besides transition metal cations were also introduced forming a series of Br?nsted-Lewis double acid organic-inorganic phosphotungstic acid salts.The melting point,acidity,structure and stability were determined and characterized by melting point determination,n-butylamine/acetonitrile titration,pyridine infrared adsorption(Py-IR),FT-IR,XRD,TG-DTG and elemental analysis(ICP-AES).It was found that the optimized catalyst Mn0.5[MIMPS]2PW12O40 showed good catalytic activity and selectivity,the conversion of α-pinene was 99.8% and selectivity of dimerization could reach to 60.7% under the optimized reaction conditions of 7 wt% of catalyst,10 mL of toluene,10 mL of α-pinene,reaction temperature 80 ° C and reaction time 16 h.The catalyst dispersibility is higher than that of pure phosphotungstic acid and sill contained good catalytic activity after recycled for 8 times without further treatment.In the study of reaction mechanism,it was found that the isomerization and dimerization of the reaction occured simultaneously.The dimerization products are α-pinene and its main isomer products through the polymerization.It was also found that 3-carne is a bridge linking isomerizations between the α-pinene ring-opening and ring-expanding reaction.The α-pinene dimerization products were got after distilled and purified by above α-pinene dimerization / isomerization reaction mixture,then hydrogenated and mixed with pinane in different proportions.The relationship between the density,freezing point,combustion calorific value,viscosity,flash point of complexes was investigated and compared with other existing HEDFs to obtain the best compound ratio of the composite fuel products.On this basis,the catalyst was controlled to catalyze the reaction of α-pinene,and the optimized proportion of dimer / isomer product mixture was obtained directly,then the composite fuel product was obtained directly by one pot hydrogenation.In addition,the above-mentioned reaction could be carried out directly using the turpentine instead of α-pinene as a raw material,and a composite fuel product with good low temperature and fuel performance could be obtained.This study provides a feasible new way for the preparation of HEDF for biomass resources turpentine and α-pinene.