| With the advantages of huge production,suitability for storage and transportation,renewable,and convertible into gaseous fuels and liquid oils,biomass resources are considered as the most potential alternative to fossil fuels.Biomass pyrolysis technology is an efficient way to utilize biomass resources,through which the resources can be converted into bio-oil,syngas and bio-char.However,biomass tar would be inevitably produced during the process.The presence of tar in the gaseous product will block and corrode the pipeline,affect the normal operation of the equipment,and also cause the waste of resources and the environmental pollution.In this paper,the combination of catalytic cracking and partial oxidation significantly reduced the tar content in the syngas and improved the utilization efficiency of biomass energy resources by using the two-stage pyrolysis-catalytic reaction system.Meanwhile,it was also found that the nickel supported on activated carbon catalyst could greatly promote the growth of carbon nanotubes.Furthermore,the tire pyrolysis vapors were utilized as the carbon source for generation of carbon nanotubes.The detailed conclusions are drawn as follows:(1)The effects of the combination of heterogeneous catalysis using char as catalyst and partial oxidation on tar conversion,composition and lower heating value(LHV)of syngas were studied under different temperatures(600?900 ?)and air additions(5%,13%and 20%).The results indicated that both the char heterogeneous catalysis and the homogeneous partial oxidation have a great influence on tar the conversion rate;the combination of the two methods exhibited a higher tar conversion rate than either of the two methods alone.At the temperature of 900 ?,the tar conversion rate reached the highest value(95.95%)using the combination of the two methods(2)Five kinds of catalysts(Ce-char,Ni-char,Fe-char,K-char and Ca-char)were prepared by an impregnation method using biomass char as the catalyst support.The effects of partial oxidation and char-supported catalysts on tar conversion rate,syngas composition and tar composition were investigated under the condition of catalyst bed temperature of 800 ?and air addition of 13%.The results indicated that the catalytic performances of M-chars for tar conversion were:Ce-char>Ni-char>Fe-char>K-char>Ca-char;when Ce-char was used as catalyst,the conversion efficiency of tar was 99.28%and the LHV of the syngas reached 8.55 MJ/m3.(3)In order to solve the problem of carbon deposition on the catalyst,six catalysts(Fe/y-Al2O3,Co/?-Al2O3,Ni/?-Al2O3,Fe-/AC,Co/AC and Ni/AC)were prepared by the impregnation method.And the catalytic performance of these catalysts for the pyrolysis-catalytic conversion of waste tires to hydrogen and carbon nanotubes was screened and evaluated.The results showed that the catalytic performance of activated carbon supported catalysts were superior to those of y-Al2O3 supported catalysts.For the same catalyst support,the Ni-based catalysts exhibited better catalytic performance,followed by the Fe-and Co-based catalysts.Among these catalysts,Ni/AC showed the best catalytic performance,which produced the highest hydrogen production(59.55%)and carbon nanotubes. |
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