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1.
Keisuke Kojiro Tsunehisa Miki Hiroyuki Sugimoto Masamitsu Nakajima Kozo Kanayama 《Journal of Wood Science》2010,56(2):107-111
To investigate micropores and mesopores in the cell walls of dry wood, CO2 gas and N2 gas adsorption onto dry wood were measured at ice-water temperature (273 K) and liquid nitrogen temperature (77 K). CO2 gas adsorption isotherms obtained were used for determining micropore volumes smaller than 0.6 nm by the HK method (Horvath-Kawazoe
method), and N2 gas adsorption isotherms obtained were used for determining the mesopore volume between 2 nm and 50 nm by the Barrett-Joyner-Halenda
(BJH) method. Micropores and mesopores existed in cell walls of dry wood, and the cumulative pore volume was much larger for
micropores than for mesopores. Micropores in the cell wall of dry wood decreased with elevating heat treatment temperature,
and the decreased micropore was reproducible by wetting and drying. Mesopores did not decrease so much with elevating heat
treatment temperature. Micropore volumes for the softwood Hinoki and the hardwood Buna were compared. A larger amount of micropores
existed in hardwood Buna than in softwood Hinoki, and this relationship was considered to correspond to the difference in
thermal softening properties for lignin in water-swollen Hinoki and Buna. This result probably indicates that micropores in
the cell walls of dry wood relate to the structure of lignin. 相似文献
2.
To investigate the influence of heating and drying history on the microstructure of dry wood, in addition to the dynamic viscoelastic
properties, CO2 adsorption onto dry wood at ice.water temperature (273 K) was measured, and the micropore size distribution was obtained
using the Horvath-Kawazoe (HK) method. Micropores smaller than 0.6 nm exist in the microstructures of dry wood, and they decreased
with elevating out-gassing temperature and increased again after rewetting and drying. Dry wood subjected to higher temperatures
showed larger dynamic elastic modulus (E′) and smaller loss modulus (E″). This is interpreted as the result of the modification at higher temperature of the instability caused by drying. Drying
history influenced the number of micropores smaller than 0.6 nm in dry wood not subjected to high temperature, although the
difference in the number of micropores resulting from the drying history decreased with increasing out-gassing temperature.
A larger number of micropores smaller than 0.6 nm exist in the microstructure of dry wood in more unstable states, corresponding
to smaller E′ and larger E″ than in the stable state. Consequently, unstable states are considered to result from the existence of temporary micropores
in the microstructures of dry wood, probably in lignin.
Part of this report was presented at the 55th Annual Meeting of the Japan Wood Research Society, Kyoto, March 2005, and at
the 56th Annual Meeting of the Japan Wood Research Society, Akita, August 2006 相似文献
3.
In our preceding study, we clarified that liquids having similar molecular sizes to ethanol were mainly adsorbed onto lignin
among the major constituents of wood. This suggests that most micropores or adsorption sites loosely hydrogen-bonded to each
other, which are accessible to these liquids, exist in lignin. In the present study, to examine micropores in wood and lignin,
micropore distribution was measured by CO2 gas adsorption at ice-water temperature (273 K). Dry samples prepared by gradual delignification from wood meal were used
as adsorbents. The pore-size distributions were determined by analyzing adsorption isotherms using the Horvath-Kawazoe method.
It was found that the number of micropores decreased with the decrease in residual lignin, and micropores were hardly found
in cellulose and hemicellulose. It is considered that most micropores smaller than 0.6 nm in wood exist in lignin. 相似文献
4.
为了研究高温重整方法对活性炭性能的影响,以商品磷酸法木质成型活性炭为原料,考察了不同升温/降温方式、重整温度和重整时间对活性炭强度、孔结构、着火点和官能团的影响。结果表明:快速升温至800℃重整活性炭30~75 min后快速降温的方式(快速升温/快速降温(FH/FC))可使活性炭强度提高5.75%~6.39%,得率保持在83.54%以上,比梯度升温/自然降温(GI/ND)更高效节能。对经800℃重整30和60 min后的活性炭的孔结构和吸附性进行研究,发现活性炭的比表面积和总孔容积分别下降约400 m2/g和0.3 m3/g,孔径分布在1.2 nm以下的微孔所占的比例增加,对亚甲基蓝的吸附性能略有下降,而对碘的吸附性能略有提高,丁烷工作容量下降15%以内。经高温重整后,活性炭的着火点显著提高,800℃重整60 min后,着火点提高100℃以上,这与高温重整后活性炭表面含氧官能团数量的减少有关。 相似文献
5.
Molecular sieving behavior of carbonized wood: selective adsorption of toluene from a gas mixture containing α-pinene 总被引：1，自引：0，他引：1
The adsorption properties of wood carbonized at various temperatures were investigated using a mixed gas containing toluene
and α-pinene. Hinoki (Chamaecyparis obtusa) samples carbonized at 500°–1100°C were exposed to gas mixtures of toluene and α-pinene at 20°C. The samples carbonized at 500°–700°C only adsorbed toluene, whereas those carbonized at 800°–1100°C adsorbed
both toluene and α-pinene. Analysis of the surface structure of the carbonized wood by nitrogen adsorption at liquid nitrogen temperature indicated
that the sample carbonized at 700°C had micropores mainly 0.6 nm in diameter and few mesopores, whereas the samples carbonized
at 900°C and 1100°C had mesopores and micropores larger than 0.8 nm in diameter. With the sample carbonized at 700°C, the
flat-shaped toluene molecules could probably penetrate into the narrower pores, 0.8 nm in diameter, whereas the bulky globular-shaped
α-pinene molecules could not. Carbonization at temperatures higher than 900°C probably enlarged the pore size and thereby reduced
the selectivity of adsorption. The results revealed that wood carbonized below activation temperature has a unique flat-pore
structure that seems to work as a kind of molecular sieving carbon, successfully removing only the harmful volatile organic
compound (VOC), toluene, and leaving behind a pleasant aroma of α-pinene in the atmosphere. 相似文献
6.
通过测定试样活性炭的充填密度、水容量、比表面积、孔径分布和吸附等温线，研究了活化时间不同的３种活性炭的孔隙性能得知：随着活化时间的增加，大孔、过渡孔、微孔的容积和总孔容积都增大；大孔容积在总孔容积中所占的比例逐渐增加，微孔容积所占的比例逐渐减少，过渡孔容积所占的比例增加到一定数值后又减少；微孔分布的极大值移向半径大的一侧，半径小于０．９ｎｍ的微孔量迅速减少。 相似文献
7.
研究利用机械力化学技术制备了性能良好的活性炭。采用Central Composite Design中心复合设计和响应面分析,对影响活性炭碘吸附值的主要影响因素进行多项回归模型建立和参数优化,并通过低温液氮(N2/77 K)吸附测定较优条件下制备的活性炭的比表面积、孔容及孔径分布。结果表明,利用氯化锌为活化剂的机械力化学技术制备活性炭的较优工艺条件为:氯化锌与绝干木屑的质量之比(锌屑比)值3.00,研磨时间10 min,活化温度584℃,活化时间2.5 h,此条件下制备的活性炭碘吸附值为1 262.47 mg/g。 相似文献
8.
Characterisation of pore size distributions in variously dried Pinus radiata: analysis by thermoporosimetry 总被引：1，自引：0，他引：1
Warren J. Grigsby Hank Kroese Elizabeth A. Dunningham 《Wood Science and Technology》2013,47(4):737-747
The pore size distribution and networks within the wood cell wall tend to decrease on drying wood from its green state having implications for water ingress and further processing such as in preservative treatment. Thermoporosity measurements using differential scanning calorimetry have been applied to determine the pore size distribution of green Pinus radiata wood and how well this pore network is retained on supercritical fluid (SCF) dewatering compared with kiln drying. Generally, in green sapwood, the majority of bound water was distributed in pore sizes less than 50 nm diameter with only a small proportion present in pore sizes between 50 and 200 nm. On SCF dewatering, most bound water was found to reside in pore sizes <20 nm, consistent with dewatered wood being at fibre saturation point (FSP). Generally, on rewetting dewatered, kiln- or oven-dried wood, proportionately less bound water was present compared with green wood, consistent with reduced pore sizes and network accessibility for water ingress. Furthermore, on rewetting, there were distinctions between earlywood and latewood (LW) sections with the LW sections having a statistically greater proportion of water occupying smaller-sized pores (<20 nm). There was also greater variability of pore size distributions on sample rewetting, inferring drying does not uniformly reduce pore size volumes. Analysis suggests the extent of variability was generally less in the rewetted dewatered wood sample compared to kiln- or oven-dried samples, which may be a consequence of SCF drying only to FSP. 相似文献
9.
《Wood material science & engineering》2013,8(1-2):62-70
Abstract Mercury intrusion porosimetry (MIP) was used to evaluate the impregnation mechanisms of wood by methyl methacrylate (MMA) through examining the changes in porosity, pore volume, pore size distribution and bulk density of solid wood before and after MMA impregnation. Porosities of MMA-impregnated (hardened) wood samples were lower than those of solid wood samples for six studied species, five hardwoods and one softwood. Densities of hardened wood were enhanced from 45 to 130% depending on the species. The pore volume available for mercury intrusion was shifted from pore d>0.1 µm for solid wood to pore d≤0.1 µm for hardened wood. A pore diameter of 0.1 µm was used as the transition point for MMA impregnation and the increased mercury penetration below this point was attributed to the MMA polymer pore structure. Porosity as an intrinsic property of wood appears to be the main determinant of impregnation rate and polymer retention, especially for porosity with pore diameter >0.1 µm. The results indicate that the MIP technique is an effective tool with which to study the impregnation process. 相似文献
10.
选用低温竹炭为原料、氢氧化钾为活化剂,制备不同炭碱比和不同活化时间的竹活性炭。运用傅立叶红外光谱议(FTIR)、比表面积测定仪(BET)等仪器对竹活性炭表面官能团、比表面积和孔径结构及比电容进行了测试和分析。结果表明,炭碱比1:4、活化温度700℃、活化时间3h条件下制备的竹活性炭,比表面积为2897.7m2/g,总孔容为1.340cm3/g,平均孔径为2.59nm,亚甲基蓝吸附值为27.7ml/0.1g,碘吸附值为1920mg/g,作为超级电容器(EDLC)的电极,其比电容为114.4F/g。 相似文献
11.
热解活化法制备微孔发达椰壳活性炭及其吸附性能研究 总被引：1，自引：0，他引：1
以椰壳为原料,采用热解活化法制备微孔发达活性炭。研究了活化温度、活化时间对活性炭孔结构和吸附性能的影响。实验结果表明:活化温度为900℃,活化时间为4 h,可制得比表面积为994.42 m2/g的微孔发达活性炭,其碘吸附值为1 295 mg/g,亚甲基蓝吸附值为135 mg/g。N2吸附结果表明活性炭的平均孔径在2 nm左右,总孔容积为0.503 9 cm3/g,其中微孔容积为0.430 3 cm3/g,微孔率达85.39%。对该活性炭进行CO2动态吸附实验,CO2饱和吸附容量为56.61 mg/g,在热解活化法制备椰壳过程中,随着活化温度的升高和活化时间的延长,活性炭的得率有不同程度的降低。 相似文献
12.
13.
磷酸法自成型木质颗粒活性炭孔隙结构分析及其甲烷吸附性能 总被引：1，自引：0，他引：1
以杉木屑为原料,在不额外添加粘结剂的工艺下,采用磷酸活化法制备自成型颗粒活性炭,并对其活化工艺、孔隙结构和甲烷吸附性能进行了分析。结果表明:随着活化温度的升高,颗粒活性炭的吸附性能先升后降,450℃时吸附性能最佳,强度不断升高;浸渍比的增加有利于颗粒活性炭吸附性能的提高,不利于其强度的增大。氮气吸附等温线和压汞法分析表明:颗粒活性炭具有发达的微孔、中孔和大孔结构,浸渍比的增加有利于颗粒活性炭比孔容积的增加,不利于堆积密度和表观密度的增加。在活化温度450℃,压力3.4 MPa时单位质量和单位体积的颗粒活性炭的甲烷吸附值在浸渍比1.25时达到最大,分别为125.6 m L/g和115.2 L/L。 相似文献
14.
Lilibeth Pulido-Novicio Yasuji Kurimoto Masakazu Aoyama Kazuto Seki Shuichi Doi Toshimitsu Hata Shigehisa Ishihara Yuji Imamura 《Journal of Wood Science》2001,47(2):159-162
The ability of sugi wood carbonized at 1000°C to adsorb mercury was examined using aqueous solutions of mercuric chloride. Parameters studied include contact time, pH, adsorption temperature, and initial concentration of mercury in solution. Results showed that sugi wood carbonized at 1000°C could effectively remove mercury from aqueous solutions. The carbonized wood showed high adsorption ability for mercury at a wide pH range (pH 3–9), but its ability drastically decreased at pH 11. Adsorption decreased with increases in adsorption temperatures, indicating that the processes were exothermic in nature. Adsorption was found to follow the Freundlich isotherm model. The adsorption capacity of carbonized sugi wood was comparable to that of commercial activated carbon. 相似文献
15.
薄皮核桃壳基活性炭的制备及表征 总被引：1，自引：0，他引：1
【目的】以农林废弃物薄皮核桃壳为原料,通过化学活化-高温炭化法制备多孔活性炭材料,优化制备工艺过程,表征吸附性能机理,为薄皮核桃壳的开发利用提供技术指导。【方法】以碘吸附值和亚基甲蓝吸附值为考察指标,进行活化剂的筛选,并进一步考察原料粒度、料液比、活化时间、炭化温度和炭化时间对制备出的活性炭的吸附性能的影响。采用N2吸附-脱附等温线、元素分析仪和FTIR测定了活性炭的孔隙结构、主要元素组成和表面官能团,扫描电镜分析形貌结构,XRD和TG分析活性炭的结晶度和热稳定性。【结果】选用磷酸为最佳活化剂,薄皮核桃壳活性炭的最佳制备工艺条件为:核桃壳粉100目、料液比1:4、活化时间120 min、炭化温度500℃、炭化时间60 min,此工艺条件下制备出的活性炭的碘吸附值为657.42±3.16 mg/g、亚甲基蓝吸附值为248.55±1.94 mg/g。制备出的活性炭的表面积为449.80 m2/g,具有丰富的孔隙结构,孔容积为1.11 m2/g,平均孔径为7.87 nm。碳元素含量为65.56%,结晶度不高,为无定型结构,活性炭在400℃左右发生热降解,主要含有羧基、酚基、醇羟基等活性官能团。【结论】采用磷酸活化法制备出的薄皮核桃壳活性炭的孔隙结构发达,具有良好的吸附性能,碘吸附值和亚甲基蓝吸附值均高于国家标准,具有将废弃物资源循环利用的价值和前景。 相似文献
16.
Minzhen Bao Xianai Huang Mingliang Jiang Wenji Yu Yanglun Yu 《Journal of Wood Science》2017,63(6):591-605
This study aimed at developing a thermo-hydro-mechanical (THM) processing to compress poplar wood and investigating the effects of high temperature, moisture, and pressure during the THM processing on the changes in microstructure, porosity, mechanical properties, and dimensional stability of compressed poplar wood. The variations in these properties were correlated and their mathematical relations were determined. Poplar woods with high moisture content were compressed using different pressures at a temperature of 160 °C for different periods. The compression level was characterized by the volume compression ratio (CR), which is defined as the ratio of the compression volume and the original volume of sample before and after THM processing. The obtained results indicated that the high pressure of THM process caused the collapsing of wood cell lumens and the developing of a certain amount of fractures in the cell wall. The damage level of wood cells increased with increasing pressure and time. Moreover, the pressure narrowed the cell lumens, which decreased significantly the pore volume in wood substrate. The pore size distribution shifted from the level of macropores to those of mesopores and micropores after THM process. The THM process created superior mechanical property, especially for those with higher CR. Besides, it was revealed that the process decreased dramatically the set recovery of treated woods and improved their dimensional stability. A significant improvement was achieved in terms of the mechanical and physical properties of compressed poplar wood via the structural reformation during the THM process. 相似文献
17.
氨水改性活性炭及其性能的研究 总被引：1，自引：0，他引：1
采用氨水对活性炭进行改性,探讨氨水浓度、改性温度和处理时间对活性炭的吸附值、比表面积和表面化学结构的影响.结果表明,氨水改性对活性炭的孔结构产生破坏,不利于孔隙结构的发达,但氨水改性在活性炭表面引入了碱性基团,有利于苯酚吸附值的提高.随着氨水浓度的提高,活性炭的碘吸附值、比表面积、总孔容积和微孔容积不断下降,亚甲基蓝吸附值呈先降后升的趋势,碱性基团的含量和苯酚吸附值不断提高. 相似文献
18.
木材干缩的分形分析 总被引：12，自引：2，他引：10
本文通过一个木材干缩实验 ,展示了木材多孔性的分形特征。用银杏 (GinkgobilobaL .)和板栗(Castaneamollissima)木材作试材 ,用逐渐升高温度的方式处理试样 ,同时称重和量取尺寸 ,可以获得不同温度之间的重量和体积变化值 ,由变化值和立方体边长的对数值得直线斜率。直线斜率反映了木材中空隙体积的分形维数。这种方法可以通过不同树种、不同温度状态下木材水分逸出过程空隙空间分形维数的变化 ,分析木材的干缩规律。建议分形理论可成为木材多孔性研究的有效途径 相似文献
19.
The size and location of silver particles in K-glycerate/AgNO3 impregnated Swedish pine, green wood as well as high temperature dried, have been studied using TEM micrographs.
The diameter of the silver particles was found to be 2–20 nm in the impregnated green wood and as large as 1000 nm (major
axis) for the ellipsoid-shaped silver clusters in the impregnated dried wood. Studying the projected area of the silver particles
in impregnated green wood indicated that there are a lot of particles (40%) in the compound middle lamella with fewer particles
in the S2 (6–8%), S1 (4%) and S3 (2%) layers. The average distance between the silver particles, 50 nm (S2-layer), in impregnated green wood shows that the impregnant is distributed in the cell wall at the microfibrilar level. Experimental
results show that the fastest diffusion path into the cell wall is from the lumen over the pit membrane through the compound
middle lamella and not from the lumen through the secondary wall layer S3.
Received 11 January 1998 相似文献
20.
基于开发和利用生物质竹炭材料,以竹炭粉、凹凸棒、硅藻土等为原料,制备竹炭陶瓷复合材料,从而避免传统炭吸附材料易碎和粉尘污染的缺点。首先,将原料通过陶瓷造粒工艺制备成直径为2~5 mm的小球;然后,在N 2气氛中1250℃下烧结为竹炭陶小球,并对其结构和吸附性能进行了研究。XRD测试结果表明,竹炭陶瓷复合材料在烧结前后并未改变竹炭陶晶体结构。原料的SEM测试结果表明,竹炭粉在微观结构上存在1μm左右的大孔,其中硅藻土的微观形貌为多孔圆盘状结构,圆盘的直径分布在20~50μm,孔道直径在0.1~1.2μm;竹炭陶的SEM测试结果表明,断面结构疏松多孔,经过复合和烧结后,仍然保持了原有的孔道结构,保障了竹炭陶的吸附性能。BET法测试结果表明,竹炭陶的比表面积达到118.54 m^2/g。吸附性能测试表明,竹炭陶对水分吸附率达到22.0%,对甲醛、氨气及硫化氢等有害气体的吸附率分别达到87.7%,94.6%和96.3%。实验结果表明,竹炭陶具有良好的吸湿和气体吸附性能,是一种良好的空气净化材料,在室内环境和水处理等方面具有广阔的应用前景。 相似文献