| Biomass is an extensive,lower-priced, renewable energy with enormous reserves.It attracted a wide spread attention among researchers for its great potential as an alternative to fossil fuels.Pyrolysis liquefaction is one of the most promising methods for biomass utilization and its product bio-oil is a kind of compound with high oxygen content, low calorific value, strong corrosive which limit its application and needing for futher upgrading. Catalytic cracking is regarded as a promising upgrading method for its mild reactive conditions, low cost, easy and quick operation.However, the catalyst was prone to be coking and deactivated during upgradingprocess and leading to lower quality of the refined bio-oil.With the aim to explore possible solution to problems inbio-oil catalytic cracking upgrading, an on-line catalytic cracking upgrading scheme of combing NTP with HZSM-5 was proposed. A NTP assisted catalytic cracking reactor was designed and the effects of operating parameters on reactor’s working performance were studied. Rape straw pyrolysis steam was upgraded by NTP assistied with HZSM-5 in the reactor and the effects of the catalyst temperature, catalyst bed height, reactor discharge power on physicochemical properties and oil phase yield of upgraded bio-oil were studied. Meanwhile, the synergistic mechanism of NTP and HZSM-5 on bio-oil upgrading and catalyst coking were studied. The main work are as follows:(1) Design and performance research of NTP assisted catalytic cracking reactor. A NTP assisted catalytic cracking reactor was designed basing on DBD and coaxial cylindrical electrode structure. The effect of operating parameters on reactor’s performance were studied. The test results showed that lower system pressure, higher height of catalyst bed and temperature were helpful for the improvement of discharge power, and discharge power were increased and then decreased with the increase of catalyst particle size. Basing on performance test, the preferablysystem pressure and the catalyst particle size of NTP assisted HZSM-5 bio-oil upgrading systemareselected as 5k Pa and 4mm.(2) Biomass screening and bio-oil upgrading research. According to elements and proximate analysis, choose rape strawas the raw material of experiment for its moderate contents of moisture, ash, and high content of volatile component. The effects of the operating parameterson physicochemical properties and oil phase yield of upgraded bio-oil were studied. The results showed that the calorific value andoil phase yieldwere increased and then decreasedwhile the oxygen content was firstly decreased and then increased, with the increase of reactor discharge power, catalyst temperature, catalyst bed height. Compared with HZSM-5 catalytic cracking, NTP assited HZSM-5 catalytic cracking obtained a higer quality of upgrading bio-oil and less coke amount of catalyst which confirmed that NTP assisted HZSM-5 for bio-oil upgrading is feasible.(3) Optimization of upgrading process parameters of catalytic cracking. Taking catalyst temperature, catalyst bed height, reactor discharge power as variants and oil phase yield as index,an optimizing model of bio-oil upgrading process parameters was built based on response surface methodology. In terms of the optimizing model, optimal process parameters of bio-oil upgrading arecatalyst temperature of 391.56℃, catalyst bed height of 33.53 mm, reactor discharge power of 23.76 W.(4)Mechanism research of NTP assisted HZSM-5 catalytic cracking. Test component contents of upgraded bio-oil and measure catalyst’s coking content by GC-MS and TG-DTG. The activation energy of catalytic reaction was decreased for the reactants activation and catalyst modification by NTP. The results of GC-MS showed that the contentsof aldehydes, ketones, phenols and acids ofbio-oil were decreased by 1.98%, 2.02%, 14.78%, 1.14% with NTP assited HZSM-5 upgrading. The catalyst coking rate was decreased effectively due to the energetic electrons impact on catalyst and inactivation of Lewis acid sites.Results of TG-DTG show that the synergism of NTPeliminates fibrous carbon deposition and reduced the adhesion of graphite coke whichleding tothe reduction the total amount of coke. |
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