Font Size: a A A

Preparation And Properties Of Hydrophobic Palladium Nanoparticles And Hydrocarbon Fuel-based Nanofliuds

Posted on:2015-01-20Degree:MasterType:Thesis
Country:ChinaCandidate:H ChiFull Text:PDF
Abstract/Summary:PDF Full Text Request
For a special aviation engineering application, the endothermic hydrocarbon fuels (EHF) are designed as the pseudohomogeneous catalytic cracking systems, named nanofluids, to improve the heat sink which reflects the cooling performance of the hydrocarbon fuels. The prepared nanofluids in this work are composed of hydrophobic palladium nanoparticles as dispersants and several hydrocarbon fuels as base liquids. The corresponding investigations and results are introduced as follows.Three classes of hydrophobic palladium nanoparticles with C18H37SH, C18H37NH2and C18H37NH2&C18H37SH as ligands are prepared respectively from the reduction of K2PdCl4by NaBH4by using phase-transfer method. The effects of temperature, ligand and ratio of palladium to ligand on morphology, diameter, palladium content, and dispersion ability of the hydrophobic palladium nanoparticles in the base liquid are discussed. The prepared palladium nanoparticles are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), fourier transform infrared spectroscopy (FT-IR) and thermo-gravimetric analysis (TGA). Three kinds of hydrophobic palladium nanoparticles are prepared under the optimal conditions, which are marked as Pd@S, Pd@N and Pd@N&S, respectively. The Pd@S nanoparticles show the average diameter of1.76nm, and the palladium content is57.1wt%. The size distribution of Pd@N is at the range of1~4nm, and the palladium content is58.3wt%. The palladium content of Pd@N&S is83.5wt%.Different kinds of nanofluids composed of hydrocarbon fuels (EHF T-8, decalin) and palladium nanoparticles (the mass fraction is0.05wt%,0.1wt%or0.2wt%) are prepared. The viscosity, flow resistance, thermal conductivity and thermostability for these nanofluids are measured. It is observed that there are no obvious changes of viscosity and flow resistance in comparison with those of the base liquids. As an example, the viscosity is only increased by0.7%with the addition of0.2wt%Pd@S, while the thermal conductivity is increased by9%. For the nanofluids with addition of0.1wt%palladium nanoparticles, the order of the thermal stability is:Pd@N&S> Pd@S> Pd@N.The effects of the hydrophobic palladium nanoparticles (Pd@S, Pd@N and Pd@N&S) and ligands (C18H37SH and C18H37NH2) on the static (constant volume) and dynamic (constant pressure) cracking processes of decalin are studied at different conditions (static:440~470℃,1h; dynamic:560~640℃,3.5MPa,1mL/min). The addition of0.1wt%palladium nanoparticles can lead to the increase of the cracking conversion of decalin, and Pd@N performs best. The conversion from the static cracking of the decalin at470℃is27.5wt%. At640℃, the conversion from the dynamic cracking of decalin is increased by16.8wt%.The cracking of each nanofluid containing500ppm Pd is performed under supercritical conditions (3.5MPa,600~750℃) of decalin with a mass flow rate of1g/s in an electrically heated tube reactor, which simulates a single passage in a practical heat exchanger. The cracking results indicate that these nanoparticles exhibit catalytic activity to a certain extent, and the activity of Pd@N nanoparticles is better than that of Pd@S or Pd@N&S. The heat sink of nanofluids is effectively enhanced, and the nanofluid containing Pd@N shows the highest value, which reaches3.50MJ/kg and it is increased by0.29MJ/kg in comparison with the heat sink of thermal cracking at750℃. The cracking of aviation kerosene containing Pd nanoparticles is then performed. The heat sink is observed to be3.57MJ/kg, and it is increased by0.22MJ/kg compared with that of thermal cracking. The results confirm the feasibility of practical application of Pd nanoparticles to hydrocarbon fuels.As mentioned above, the hydrophobic palladium nanoparticles can be controlled with different contents of palladium and different kinds of ligands to meet different demands. The conversion and heat sink of the hydrocarbon fuels are increased with the addition of hydrophobic palladium nanoparticles. It is concluded that the nanofluids with hydrophobic palladium nanoparticles in hydrocarbon fuels should be possess promise application prospect.
Keywords/Search Tags:Hydrocarbon fuels, Hydrophobic palladium nanoparticles, Thermalstability, Static cracking, Dynamic cracking, Heat sink
PDF Full Text Request
Related items