Study On The Catalytic Reforming Of Tar Model Compound For Hydrogen Production With Bifunction Calcium Based Catalyst

Tar has severely restricted the application and development of biomass gasification technology.The effective removal and conversion of tar has attracted a lot of attention from relevant researchers in recent years.The removal of biomass tar by catalytic conversion is a relatively efficient method,the key of which lies in the selection and preparation of the catalyst.In the previous research,NiO/CaO-Ca₁₂Al₁₄O₃₃bifunction catalyst tar model compound has good effects on catalytic reforming performance,CO₂adsorption performance and anti-coking performance,but it is not ideal for the actual tar catalytic reforming hydrogen production,and the lack of a clear understanding of the mechanism of action of the catalyst.In response to the above problems,the paper selected benzene,m-cresol,and 1-methylnaphthalene,which are large representatives of the tar component,to carry out catalytic reforming hydrogen production research,explore the reaction mechanism,and further modify the calcium-based catalyst with a view to a method for improving the hydrogen production efficiency of tar catalytic reforming was found,and on this basis,an experimental study on the service life and cycle regeneration performance of the bifunction calcium-based catalyst was carried out.The main research conclusions are as follows:（1）Experimental studies on catalytic reforming of benzene,m-cresol,and1-methylnaphthalene in different tar model compound,investigated the effects of different temperatures and water-carbon ratio（S/C）on the catalytic performance of NiO/CaO-Ca₁₂Al₁₄O₃₃catalyst and explore the optimal process conditions for catalytic reforming to produce hydrogen.The results show that the catalytic activity of the bifunctional calcium-based catalyst increases first and then decreases with increasing temperature and water-to-carbon ratio.When benzene is used as a tar model compound,the optimal temperature for steam reforming should be 850℃and the optimal S/C should be 3.When m-cresol is used as a tar model compound,the optimal temperature for steam reforming should be 950℃and the optimal S/C should be 6.When 1-methylnaphthalene is used as a tar model compound,the optimal temperature for steam reforming should be1000℃and the optimal S/C should be 6.（2）Under the action of NiO/CaO-Ca₁₂Al₁₄O₃₃catalyst,the conversion order of the three tar model compound for catalytic reforming reaction is benzene>m-cresol>1-methylnaphthalene,after steam reforming of different tar model compound carried out XRD,ESEM,etc.and the detection of reaction intermediate products,speculated that the catalytic reforming reaction mechanism of these three different tar model compound:benzene undergoes a dissociative adsorption reaction on Ni,and after the benzene ring loses one or more H ions,adsorption reaction with oxygen ion O^-in the oxygen carrier generates small molecule gas;m-cresol undergoes bond breaking and recombination to form intermediates such as toluene,phenol,ethanol,acetaldehyde,benzene,etc.,and finally becomes small molecule gas;1-Methylnaphthalene will generate a large amount of by-products such as naphthalene,dihydroacenaphthene under the action of calcium-based bifunctional catalyst,and a small amount of catalytic reforming will generate synthesis gas.（3）In order to explore the cause of catalyst deactivation,a service life exploration experiment of NiO/CaO-Ca₁₂Al₁₄O₃₃catalyst was carried out.The results showed that with the extension of the reaction time of benzene steam reforming,the long-term high-temperature environment caused catalyst sintering and catalyst surface carbon deposits have led to a decrease in the activity of calcium-based catalysts.In the NiO/CaO-Ca₁₂Al₁₄O₃₃catalyst cycle performance exploration experiment,the method of regeneration of deactivated catalyst was explored.The experiment showed that the catalyst after the steam reforming reaction was regenerated at 850℃and O₂atmosphere for 25 min.In the benzene catalytic reforming reaction,after five cycles of benzene steam reforming and catalyst regeneration,the catalytic activity of the calcium-based catalyst is slightly weakened,indicating that the catalyst regeneration method can effectively improve its cycle performance.（4）In order to explore the method to improve the recycling rate of NiO/CaO-Ca₁₂Al₁₄O₃₃catalyst,Mg,Cr and La were used as metal additives to dope the calcium-based catalyst,and the cycle performance test of the modified calcium-based catalyst was carried out research and comparison of ESEM images obtained from experimental studies indicate that the order of the amount of porosity and roughness is La-modified>unmodified>Cr-modified>Mg-modified;the comparison of EDS graphs shows:the order of loading effect of modified additives It is La modification>Mg modification>Cr modification;the hydrogen yield and carbon conversion index of the benzene catalytic reforming gas product shows that the order of catalytic activity of the catalyst after recycling is La modification>Mg modification>Cr modification>unmodified;TG characterization results of the catalyst after 5 cycles of experiments show that:the three modified calcium based bifunctional anti-carbon deposition performance size order is Mg modified>Cr modified>La modified>unmodified.in general,the three modified bifunction calcium based catalyst have the cycle performance order of La₂O₃-NiO/CaO-Ca₁₂Al₁₄O₃₃>Mg O-NiO/CaO-Ca₁₂Al₁₄O₃₃>Cr₂O₃-NiO/CaO-Ca₁₂Al₁₄O₃₃.Among the three metal additive modification methods,the doped metal additive La is the most effective method to improve the recycling rate of calcium-based catalyst NiO/CaO-Ca₁₂Al₁₄O₃₃.