Microwave-assisted Catalytic Fast Pyrolysis Of Bamboo For Bio-oil Production With Modified HZSM-5 Catalyst

With strong acidity and shape selectivity,HZSM-5 zeolites are widely used in catalytic fast pyrolysis of biomass.However,HZSM-5 zeolites are subjected to deactivation as the catalytic reaction proceeds,the underlying reason is that coke formation will inevitably occur and thus cause pore blockage.Thus HZSM-5 zeolites modified by phosphorus,zinc and nickel were prepared using wetness impregnation method firstly.Simultaneously,chemical liquid deposition with tetraethyl orthosilioate and tetrabutyl titanate as the modifiers was used to modify HZSM-5.X-ray diffraction?XRD?,nitrogen?N₂?-adsorption/desorption,ammonia-temperature programmed desorption?NH₃-TPD?and scanning electron micrograph?SEM?techniques are employed to investigate the porosity and acidity characteristics of original and modified HZSM-5 samples.Py-GC/MS and microwave-assisted catalytic fast pyrolysis?MACFP?of bamboo experiments are further conducted to explore the catalytic effect of modified HZSM-5 samples on biomass CFP and to verify the positive effect on coke reduction.Moreover,the influence of the parameters including midified catalysts ratio,the content supported on catalysts was investigated.Experimental results showed that strong acid sites amounts of phosphorus modified HZSM-5 zeolites decreased distinctly and acid sites strength slightly reduced.All of HZSM-5 zeolites midified by phosphorus,zinc and nickel remained original skeleton structure.With the loading amount increasing,the specific surface area and micropore volume decreased.The anti-coking performance of HZSM-5zeolites was enhanced by phosphorus and the selectivity of monoaromatics was strengthened by zinc and nickel.The optimal loading amount of phosphorus was 2.5%,Py-GC/MS experiments results showed that selectivity of monoaromatics increased.MACFP experiments results showed that the relative content and selectivity of monoaromatics in oil-phase products increased from 16.96%to 17.53%,40.12%to50.56%respectively,phenols with low oxygen content reach the maximum and the coke content decreased dramatically to 8.85%.Moreover,P/Zn-HZSM-5 with 3%zinc loading and P/Ni-HZSM-5 with 2%nickel loading exhibited good performance,and Py-GC/MS experiments results showed that the relative amount and selectivity of monoaromatics increased.MACFP experiments results showed the relative content and selectivity of monoaromatics in oil-phase products increased to 18.84%and 52.38%with 3%zinc.Simultaneously,MACFP experiments results also showed the relative content and selectivity of monoaromatics in oil-phase products increased to 20.80%and 55.46%with 2%nickel.The content of phenols with low oxygen content reached the maximum and the coke content decreased slightly.The optimal production distribution could be gotten with the catalysts ratio of 1:1.Furthermore,the results showed that the HZSM-5 zeolites modified by chemical liquid deposition maintained the original framework structure.The SiO₂ and TiO₂deposited on the surface of HZSM-5 zeolite were well-dispersed.The specific surface area and micropore volume decreased slightly.Both of the HZSM-5 zeolites modified by SiO₂ and TiO₂ had a beneficial effect on improving the production distribution and the anti-coking performance.The optimal depositing content of SiO₂ was 2%,and Py-GC/MS experiments results showed that the relative amount and selectivity of monoaromatics increased.Moreover,MACFP experiments results showed that the relative content and selectivity of monoaromatics in oil-phase products increased from16.96%to 20.97%,40.12 to 48.72%respectively,phenols with low oxygen content reach the maximum and the coke content decreased dramatically to 8.72%.Simultaneously,Py-GC/MS experiments results exhibited similar tendency with4%TiO₂ depositing content.And MACFP experiments results showed that the relative content and selectivity of monoaromatics in oil-phase products increased to 23.57%and 58.41%.The content of phenols with low oxygen content reach the maximum and the coke content decreased considerably.The optimal production distribution could be gotten with the catalysts ratio of 1:1 and the treatment time of 4 hours.Moreover,with the maximum relative content and selectivity of monoaromatics and the minimum coke amount of 7.58%,4%TiO₂-HZSM-5 exhibited better deoxidation and anti-coking performance than other modified zeolites.