| Biomass resources are abundant,renewable and environmentally friendly raw materials which are regarded as one of the most attractive resources for producing renewable chemicals.TG-FTIR,Fixed bed reactor and GC/MS techniques were used to analyzed the the effect of temperature,flow rate of N2,acid pretreatment and catalyst on the pyrolysis properties,product distribution and composition of walnut shell pyrolysis process.(1)TG-DTG results showed that the walnut shell undergoes three consecutive stages,corresponding to moisture evaporation,thermal decomposition,and further carbonization.The second stage(200～450℃)was the main stage with the 60%weight loss.The fixed bed experiment results showed that the higher N2 flow rate and temperature,the higher gas yield and lower coke yield obtained,while the maximum liquid yield was obtained at 550℃ with of 50 mL/min N2 flow rate.GC/MS was used to investigate the components of liquid products which obtained at 340℃ and the 100 mL/min of N2 flow rate.It was found that the main compounds were nitrogen-containing chemicals,light aromatic hydrocarbons,ketones and phenols.(2)The channels appeared in the surface structure of walnut shell after HCl+HF pretreatment which leads to the increasing of the specific surface area.The acid washing removed the ash,alkali metal and alkaline earth metal(K,Ca,Na,Mg)in walnut shell,while C,H,O content increased and N element almost disappeared after acid washed.In TG experiment,the weight loss of acid washed sample were 75 wt%,which was 5%higher than untreated sample,while the amount of main gas pruoducts(CO,CO2,CH4 and moisture)were decreased.After acid washing,the liquid products increased 31%and gasous and char products reduced.Acid washing significantly inhibited the formation of nitrogenous compounds,but greatly promoted the formation of carbohydrate components in liquid products.Nitrogenous compounds decreased from 22.6%to 7.29%,and sugars increased from 1.02%to 18.68%.(3)H-Beta and H-ZSM-5 improved the yield of liquid and gasous products while reduced the yield of char on fixed bed catalytic pyrolysis experiment of acid washed walnut shell.The results of the liquid products GC/MS analysis showed that the component of ketones,acids and oxygen-containings were inhibited and the inhibitory effect of H-Beta was more obvious than H-ZSM-5.H-Beta and H-ZSM-5 promoted the production of aromatics content from 11.1%to 14.4%and 12.87%,respectively.The gasous products of CO2,CO,CH4 and moisture from acid washed sample in TG-FTIR pyrolysis process were promoted by all two catalysts. |
