Effect of woody perovskite-type catalysts on diesel engine exhaust purification performance
In order to achieve four-way purification of soot(ST),nitrogen oxides(NOx),hydrocarbons(HC)and carbon monoxide(CO)in diesel exhaust,four kinds of La0.8Ce0.2Fe0.3Co0.7O3 woody perovskite-type catalysts(LCFCO-600,LCFCO-700,LCFCO-800 and LCFCO-900,respectively)were prepared by using wood fiber as biomass templates and calcination at 600℃,700℃,800℃and 900℃,respectively.The micromorphologies of the catalysts were observed by scanning electron microscope(SEM),and the elemental composition and corresponding proportion of LCFCO-800 were analyzed by energy spectrum(EDX).The crystal structure and phase composition of the catalysts were characterized by X-ray diffraction(XRD).The typical chemical bonds of the catalysts were analyzed by Fourier transform infrared spectroscopy(FT-IR).The structure parameters of the catalysts were analyzed by N2 adsorption/desorption.The four-way purification performance of the catalysts were evaluated by simulation experiments.The results show that the prepared catalysts have obvious biomass structure and high perovskite phase purity,among which LCFCO-800 has the largest specific surface area,total pore volume and average pore size,which are 3.270 m2/g,0.017 cm3/g and 20.486 nm,respectively,and LCFCO-800 has good four-way purification performance.Under the conditions of simulated exhaust temperature of 400℃,flow rate of 1 L/min and purification time of more than 120 s,the maximum purification efficiency of LCFCO-800 for ST,NOx,HC and CO is 92%,92%,98%and 76%,respectively.In addition,according to the Mars-van Krevelen REDOX reaction mechanism and experimental results,the four-way purification mechanism of the catalyst was analyzed.It is concluded that the increase of ST mass concentration can inhibit the oxidation of HC and CO,and the oxidation process of ST,HC and CO can help to generate more oxygen vacancies on the surface of catalysts,thus promoting the reduction of NOx.
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