Pyrolysis Of Camellia Oleifera Shell And The Preparation And Characterization Of Mesoporous Activated Carbon

Using camellia oleifera shell from Guangxi Baise as raw material, the pyrolysis process was investigated under nitrogen atmosphere by a self-made tube-type pyrolysis furnace; and the mesoporous activated carbons (ACs) were prepared by one-step carbonization activation with H3PO4activation under traditional thermal and microwave. The ACs were characterized, and the pore structure of ACs was investigated. The main contents are as follows:The collection rate of char, bio-oil and uncondensable gas products were investigated at different temperature. With the temperature increasing from300℃to800℃, the collection rate of char decreased steadily, whereas, the collection rate of uncondensable gas increased. The collection rate of bio-oil increased at first and then decreased with the highest collection rate up to40.2%at500℃. The main components in the bio-oil were analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC). The results showed that the bio-oil was a complex mixture of oxy-organics.73peaks were separated and24compounds representing68.73%of the total peak area were identified to be acids, phenols, aldehydes, ketones, furans and esters. The main products were acetic acid (32.82%),1,2-Benzenediol (5.24%), Phenol,2,6-dimethoxy-(4.38%),1,2-Benzenediol,4-methyl-(3.27%), and phenol,2-methoxy-(3.19%). The process of forming bio-oil from pyrolysis of camellia oleifera shell was discussed, and the complex pyrolysis reaction networks were obtained.The influence factors on the preparation of ACs by traditional thermal and microwave were studied, and the suitable conditions were obtained. The optimal conditions for AC prepared by traditional thermal (hAC) were impregnation time20h, H3PO4solution concentration50(wt)%, particle size of raw material0.25～0.38mm, activation temperature500℃, activation time2.5h and impregnation ratio1:2.0; and the iodine and methylene blue (MB) value were969.87mg·g-1and279.55mg·g-1. The optimal conditions obtained for AC prepared by microwave (mwAC) were particle size of raw material0.25～0.38mm, impregnation ratio1:2.0, H3PO4solution concentration60(wt)%, microwave radiation time18min, microwave power700W and impregnation time20h; and the iodine and methylene blue (MB) value were1015.34mg·g-1and225.56mg·g-1.The characterization and pore structure of the self-made ACs from camellia oleifera shell was studied using nitrogen physisorption, SEM, XRD, FT-IR, Boehm titration and TG/DTA. The nitrogen adsorption isotherms of ACs were investigated on the bases of as-plot and Barrett-Joyner-Halenda (BJH) methods. The results showed that they had a narrow pore size distribution within1.4-5nm, and the SBET and mesoporous ratios of the hAC and mwAC were 1598.9m2·g-1and1767.5m2·g-1,75.3%and84.3%respectively. Adsorption capacity of ACs combined with the analysis of pore structure showed that the mwAC trended to form the pores with "small entrance-large body". XRD results showed that crystal structure of ACs was non-graphitized disorder structure. The FT-IR and Boehm titration indicated that the surface of ACs contained some oxygen-containing functional groups such as carboxyl, lactone and phenolic hydroxyl; the surface acidity of mwAC was stronger than hAC. TG/DTA analysis founded that hAC and mwAC had an excellent thermal stability below500℃.