Producing Monocyclic Aromatic Hydrocarbons By Catalytic Cracking Of Biomass Based On HZSM-5 Molecular Sieve Catalyst

The traditional chemical industry needs to accelerate the innovation of technology under the background of the shortage of fossil resources.Monocyclic aromatic hydrocarbons(MAHs)are important chemical raw materials,and their traditional preparation methods are overly dependent on non-renewable resources.The catalytic pyrolysis of biomass with HZSM-5 catalyst is one of the most promising technologies for producing MAHs.However,the bio-oil obtained contains a large number of harmful polycyclic aromatic hydrocarbons(PAHs),and the characteristic of coking devitrification of HZSM-5 catalyst,which hinder the commercial application of the technology.Therefore,the technology was optimized by modifying the catalyst and introducing additional hydrogen sources.1.Selective preparation of monocyclic aromatic hydrocarbons from catalytic cracking of pine over Ti(SO4)2-MO2N/HZSM-5 catalyst.To selectively produce monocyclic aromatic hydrocarbons(MAHs)with low amount of polycyclic aromatic hydrocarbons(PAHs),modified HZSM-5 catalysts(Mo2N/HZSM-5,Ti(S04)2/HZSM-5 and Ti(S04)2-Mo2N/HZSM-5)were prepared and employed for ex-situ catalytic fast pyrolysis(CFP)of pine wood Both analytical pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)and lab-scale pyrolysis experiments were conducted to investigate the effects of catalyst,pyrolysis temperature and catalyst-to-pine ratio on the distribution of aromatic hydrocarbon products.The result of Py-GC/MS showed that the maximal MAHs yields from Ti(SO4)2-Mo2N/HZSM-5 catalysts were 12.53 wt%at 650? and catalyst-to-pine ratio of 7.Corresponding PAHs yields from the catalyst were 1.10 wt%.The results clearly indicated that the Ti(SO4)2-Mo2N/HZSM-5 significantly increased MAHs formation and decreased PAHs formation as compared with HZSM-5.Furthermore,lab-scale experiments were conducted to quantitatively determine the pyrolytic product distribution.Results showed that Ti(SO4)2-Mo2N/HZSM-5 catalyst increased the yield of liquid and gas products,and decreased solid products as compared with HZSM-5.Under optimal conditions of 650? and catalyst-to-pine ratio of 4/3,the actual yields of MAHs and PAHs from Ti(SO4)2-Mo2N/HZSM-5 catalyst were 9.71 wt%and 1.45 wt%,respectively.In addition,stability tests confirmed that the Ti(SO4)2-Mo2N/HZSM-5 catalyst possessed better effects on MAHs production as well as anti-deactivation than the HZSM-5.2.Selective preparation of monocyclic aromatic hydrocarbons from calcium formate assisted catalytic cracking of pine over HZSM-5 catalystThe purpose of introducing hydrogen donors into the catalytic cracking system is to improve the hydrogen deficient environment of hydrocarbon pool of HZSM-5.Therefore,the experiment of catalytic cracking of pine over HZSM-5 with different hydrogen donors(methanol,calcium formate and polyethylene terephthalate)was carried out on Py-GC/MS.In addition,the effects of catalytic cracking temperature,hydrogen donor/biomass ratio,and modified catalyst on the yield of aromatic hydrocarbon products were also examined.The experimental results showed that after deducting the pyrolysis products of hydrogen donors themselves,methanol,calcium formate and polyethylene terephthalate promoted the yield of MAHs by-0.02%,-36.72%and 6.74%,respectively,which indicated that calcium formate had the best effect of hydrogen supply.In order to further increase MAHs yield,catalysts modified by zinc,iron and calcium were used for catalytic cracking experiments of pine under the action of calcium formate.The modified Ga/HZSM-5 significantly promoted the formation of MAHs,with the yield increased by 24.7%compared with that from unmodified catalyst.Besides,in order to eliminate the influence of pyrolysis products of calcium formate,control experiment over HZSM-5 and calcium formate was also conducted.