裂解温度对海南不同材料生物炭理化特性的影响

Effect of Pyrolysis Temperature on the Physicochemical Properties of Biochar from Different Materials in Hainan

为探求热带地区生物质在制备生物炭时对温度的响应,以热带地区植物桉树、橡胶树和椰糠为原料,在300、500和700℃下制备成桉树炭(E)、橡胶树炭(RT)和椰糠炭(SC),利用元素分析仪、扫描电镜(SEM)、X射线能谱分析仪(EDS)和傅立叶红外光谱分析仪(FTIR)等研究不同裂解温度对生物炭的酸碱度、结构及元素组成和含量的影响。结果表明,随裂解温度升高,3种生物炭的灰分含量和pH均升高,其中300~500℃的增幅(17.60%~27.59%)要明显高于500~700℃(4.97%~10.47%);3种材料生物炭对比,裂解温度为300和500℃时,pH值E>SC>RT,温度为700℃时SC>E>RT。随温度升高,3种生物炭的产量降低,各温度下,SC的产率明显高于E和RT。C/N对比,各温度条件下均为RT>E>SC。SC含有更多的元素,而E和RT的C含量更高。裂解温度在300~500℃时,E和RT的-OH振动峰(3432 cm^(‒1))随温度升高而升高,温度升高至700℃,峰值出现降低;SC在300~700℃内,-OH振动峰随温度升高而升高。波数在1659~1744 cm^(‒1)时,E和RT的C=C振动峰在300~500℃时,随温度升高而升高,此时,温度再升高,峰值差异不大,SC在300~700℃内,峰值随温度升高而升高。2800~3000 cm^(‒1),脂肪族的CH_(3)和CH_(2)基团出现,裂解温度高于500℃时,E的振动峰与700℃基本持平,而RT的振动峰在700℃出现了降低。785~880 cm^(‒1)波段的吸收峰为芳环C-H弯曲振动,裂解温度高于500℃时,随温度升高,3种原料所形成的振动峰均降低。本研究结果显示,椰糠制备的生物炭其元素组成、表面特征以及官能团与桉树和橡胶树制备的生物炭存在较大差异性,且对裂解温度的响应更敏感。

In order to explore the temperature response of biomass in the preparation of biochar in tropical areas,euca-lyptus,rubber tree and coco bran were used as the raw materials to prepare eucalyptus charcoal(E)and rubber tree charcoal(RT)and coconut bran charcoal(SC)at 300,500 and 700℃.Elemental analyzer,scanning electron microscope(SEM),X-ray energy spectrum analyzer(EDS)and Fourier infrared spectroscopy(FTIR)were used to study the pH,structure and element composition of biochar at different pyrolysis temperatures.With the increase of pyrolysis tem-perature,the ash content and pH of the three biochar increased,and the increase of 300‒500℃(17.60%‒27.59%)was significantly higher than that of 500‒700℃(4.97%‒10.47%).When the pyrolysis temperature was 300 and 500℃,the pH value was E>SC>RT,and when the temperature was 700℃,and that was SC>E>RT.With the increase of tem-perature,the yield of the three biochars decreased.At each temperature,the yield of SC was significantly higher than that of E and RT.C/N comparison showed that RT>E>SC under all temperature conditions.SC contained more elements,while E and RT had higher C content.When the pyrolysis temperature was 300‒500℃,the-OH vibration peak(3432 cm^(‒1))of E and RT increased with the increase of temperature,and the peak value decreased when the temperature increased to 700℃.SC was within 300‒700℃,-OH vibration peak increased with increasing temperature.When the wavelength was 1659‒1744 cm^(‒1),when the C=C vibration peak of E and RT was 300‒500℃,it increased with the tem-perature rise.At this time,the temperature rose again,the peak difference was not big,SC was 300‒700℃,the peak value increased with increasing temperature.At 2800‒3000 cm^(‒1),aliphatic CH_(3) and CH_(2) groups appeared.When the cracking temperature was higher than 500℃,the vibration peak of E was basically the same as 700℃,while the vibra-tion peak of RT decreased at 700℃.The absorption peak in the 785‒880 cm^(‒1)band was the aromatic ring C-H bending vibration.When the cracking temperature was higher than 500℃,the vibration peaks formed by the three raw materials all decreased with the increase of temperature.The results of this study show that the elemental composition,surface characteristics and functional groups of biochar prepared from coconut bran are quite different from those of biochar prepared from eucalyptus and rubber trees,and it is more sensitive to the pyrolysis temperature.