Characterization and evaluation of catalytic performance of mechanically activated pyrite catalysts
Industrial catalysts for direct coal liquefaction are faced with high raw material cost,high water consump-tion and salt-bearing wastewater.It is necessary to use natural minerals after mechanical activation as catalysts for di-rect coal liquefaction,but the problems such as large particle size of mineral catalysts,easy hardening after filtration and drying,and affecting dispersion and catalytic performance should be solved.By controlling the mechanical acti-vation time,a series of natural mineral catalysts with average particle size less than 5 μm were obtained by using a pyrite as raw material and tetralin with good hydrogen supply performance as grinding medium.The catalysts can be directly added to the direct coal liquefaction reaction system without filtration and drying.The catalysts were charac-terized by means of scanning electron microscopy,particle size analysis,X-ray diffraction spectroscopy and X-ray photoelectricity spectroscopy.The average particle size of the catalysts decreased rapidly to 2.82 μm after activation for 2 hours,and the decreased rate of particle sizes slowed down with the increase of activation time.The mechanical activation process had no obvious effect on the crystalline form of the active phase FeS2,but the amount of Fe2+and S2 on the surface of the catalyst increased significantly after activation,which is conductive to the improvement of catalytic activity.The sedimentation rate of catalyst in tetralin was little affected by particle size,and the dispersion of catalysts with small particle size were basically the same.Under the same reaction conditions,the pyrite catalyst with an average particle size of 2.46 μm had the best performance of direct coal liquefaction,and the conversion and oil yield reached 83.30％and 43.53％,respectively.
direct coal liquefactionpyrite catalystcatalytic performancemechanical activationtetralindis-persionaverage particle sizeconversion
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