酸洗处理对生物炭性质及其吸附生物油的影响

Effect of acid washing treatment on the properties of biocharand its adsorption performance on bio-oil

为了研究酸洗处理对生物炭性质的影响及其对生物油浆体系中生物炭吸附生物油的影响,笔者采用HCl酸洗处理,分别制备了对松木原料酸洗和对热解炭化料酸洗的生物炭,同时在相同的热解条件下制备了仅水洗处理的生物炭作为实验对照。采用傅里叶红外光谱、比表面积及孔径分析、X射线衍射、拉曼光谱等手段对上述3种生物炭进行表征,并利用3种生物炭吸附生物油,利用气相色谱-质谱联用分析被不同生物炭样品吸附的生物油的成分差别。实验结果表明,松木原料酸洗对热解炭的性质影响更大,炭表面的C O和C—O含量增加,比表面积也更大,而晶体结构和石墨化程度变化不大。3种生物炭均对生物油有较好的吸附性能,对糖类、酚类、酸类、酮类、醛类都有较强的吸附力。由于酸洗预处理松木原料的生物炭具有较高含量的C O和C—O、较大的比表面积,对生物油有更高的吸附能力,也对生物油中酸类、酮类的吸附选择性更好。生物炭能够通过氢键和静电作用吸附易促进结焦的酸类、酮类,通过π-π相互作用吸附易结焦的酚类,有利于抑制生物油浆的结焦,推动生物油浆的广泛应用。

Bio-slurry is a new type of fuel prepared by mixing bio-oil and biochar derived from biomass pyrolysis,which can be used for combustion,pyrolysis and gasification,and is a promising alternative to traditional fossil fuels.However,the presence of a large number of organic compounds in bio-oil,such as various phenolic compounds that tend to polymerize and coke when heated,and acids and ketones that tend to promote coking when heated,directly affecting the application of bio-slurry.Biochar is an adsorbent material with good economic and environmental values,so it can be used to prevent the polymerization and coking of bio-oil by blocking the coking-prone components of bio-oil in the pore channels through the adsorption.Acid washing treatment is a common modification method of biochar,which can promote the adsorption of organic matter on biochar.In order to investigate the effects of the acid washing treatment on the properties of biochar and bio-oil adsorption by the biochar in bio-slurry system,the biochar acid-washed on raw pine wood(HCl-BC)and acid-washed on pyrolysis carbonized materials(BC-HCl)were prepared in this study using the HCl acid washing treatment,while the biochar treated with water-washing only was prepared under the same pyrolysis conditions as the experimental control.The three types of biochar were characterized by the Fourier transform infrared spectroscopy(FT-IR),specific surface area and pore size,X-ray diffraction(XRD)and Raman analyses.Bio-oil was adsorbed using the three types of biochar,and the differences in the composition of bio-oil adsorbed by different biochar samples were analyzed by the gas chromatograph-mass spectrometer(GC-MS).The experimental results showed that the acid washing treatment of pine wood had a greater effect on the properties of the biochar,with an increase in the C O and C—O contents and a larger specific surface area,while the crystal structure and the degree of graphitization did not change much.All three types of biochar had good adsorption performance on bio-oil,with strong adsorption on sugars,phenols,acids,ketones,and aldehydes.HCl-BC was more efficient in adsorption of organic matter due to its higher content of C O and C—O and larger specific surface area,and also had better selectivity adsorption for acids and ketones in bio-oil.Biochar is able to adsorb acids and ketones that tend to promote coking through hydrogen bonding and electrostatic interaction,and adsorb phenols that tend to coke throughπ-πinteraction,which is beneficial to inhibit coking of bio-slurry and promote the wide application of bio-slurry.