膨胀石墨/有机金属骨架复合吸附材料的制备及性能研究

doi:10.11949/j.issn.0438-1157.20181174

摘要/Abstract

摘要：

粉末状有机金属骨架材料（MOFs）普遍存在密度低热导率低的不足，是限制其在水蒸气吸附领域应用的关键因素之一。以典型的高吸水量MOFs材料对苯二甲酸铬（MIL-101（Cr））为研究对象，采用干混法将膨胀石墨（EG）与该MOFs材料复合并模压成型，制备了一系列不同密度不同石墨含量的复合吸附材料。利用光学显微镜表征了材料微观结构，分析了压制密度、EG含量对材料内部结构的影响；使用恒温恒湿箱测试了纯MOFs材料及复合吸附材料的饱和吸附量，发现纯MOFs粉末在压制压力超过3 MPa后吸附能力大幅下降。在此基础上制备了密度适宜的复合材料，测试发现复合材料的饱和吸附量随着EG含量的增加而显著降低，但EG对MOFs本身的吸附量未造成显著影响；采用体积法研究了材料的吸附动力学，其中片状纯MOFs相比粉末状MOFs吸附速率大幅下降，而复合材料由于内部产生了更多的传质通道使其表面传质系数相比于片状纯MOFs提高了2.7倍。热导率测试结果表明复合吸附材料的热导率随着石墨含量的增加而显著升高，而材料的密度对热导率的影响相对较小。采用干混法制备的石墨含量50%，密度408 kg·m⁻³的复合吸附材料，其热导率相比纯MOFs材料提高了22倍达到2.76 W·m⁻¹·K⁻¹。

Abstract:

Low density and low thermal conductivity are common drawbacks of powder metal organic frameworks (MOFs), which is one of key point limited the application of MOFs. MIL-101(Cr) as a typical water adsorption MOFs with high adsorption capacity is the major study object in this work. Two methods of directly dry-mixing and soaking are utilized to composite expanded graphite (EG) with MOFs, after compression by mold, a series of composite sorbents pellets with different EG content and packed density are developed. The optical microscope is utilized to observe the structure of materials, by which the influences of packed density and EG content on microscale structure are analyzed. The tests of saturated sorption capacity of pure MOFs and composites are carried out in a constant temperature and humidity chamber, whose results indicates the sorption capacity of pure MOFs will apparently reduce if the compression pressure is higher than 3 MPa. Accordingly, composite sorbents are prepared under relatively low compression pressure, whose sorption capacities are decrease with the increase of EG content, which is only caused by the decrease of MOFs content while there is no negative effects of EG on MOFs adsorption. Volume method is applied in adsorption kinetics study, which reveals the adsorption rates of pellets pure MOFs are much lower than powder pure MOFs. However, the composites shows 2.7 times higher surface diffusive coefficient than pellet pure MOFs ascribed of the appearance of more mass transfer channels caused by compression with EG. The results of thermal conductivity measurements of composite sorbent illustrate that thermal conductivities are obviously enhanced with the increase of EG content while a much smaller enhancement is observed by increasing packed density. Comparing with pure MOFs, the developed composites by dry-mixing method with EG mass content of 50%, with packed density of 408 kg·m^-3 shows extraordinary high thermal conductivity of 2.76 W·m^-1·K^-1, which is 22 times higher than pure MOFs.

中图分类号:

许嘉兴, 晁京伟, 李廷贤, 王如竹. 膨胀石墨/有机金属骨架复合吸附材料的制备及性能研究[J]. 化工学报, 2018, 69(S2): 492-499.

XU Jiaxing, CHAO Jingwei, LI Tingxian, WANG Ruzhu. Preparation and characterization of expanded graphite/metal organic frameworks composite sorbent[J]. CIESC Journal, 2018, 69(S2): 492-499.

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