Siloxane treatment by adsorption into porous materials
Siloxane treatment by adsorption into porous materials
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DOI：
10.1080/09593330903057540
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发表时间：
2009-09
影响因子：
2.8
通讯作者：
D. Ortega;A. Subrenat
中科院分区：
文献类型：
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作者：
D. Ortega;A. Subrenat
硅氧烷广泛用于不同的应用中：例如，保健、干洗、家用产品、油漆和涂料、纸张、个人护理。这解释了它们在环境中的普遍性。由于它们的挥发性，大多数时候它们分散在大气中，但它们也可以存在于垃圾填埋场的泥浆中。在厌氧消化过程中，当温度上升到60 ° C时，硅氧烷挥发，形成沼气的一部分。利用沼气生产能源、热量和氢气的操作问题已经确定。在高温下，硅氧烷转化为二氧化硅（通常称为砂传输）。这些白色沉积物可能粘附在金属或催化基材表面上，严重降低设备效率，这可能是更改设备保修的原因。因此，消除硅氧烷变得非常重要。不幸的是，在这个问题上可以找到的信息相对较少。尽管如此，一些作者描述了不同的硅氧烷定量分析方法，最近的研究着眼于垃圾填埋场中硅氧烷的存在以及对使用所产生的沼气的能量回收设备的限制。硅氧烷和有机硅在工业生产过程中的消费量不断增长，从而增加了它们在环境中的普遍性，阻碍了沼气作为"绿色能源"的使用。因此，本研究的主要重点是硅氧烷的处理。它们的消除进行了使用四种不同的多孔材料的吸附过程：活性炭布（ACC），颗粒活性炭（GAC），沸石和硅胶。本研究中使用了两种代表性的硅氧烷化合物，六甲基二硅氧烷（L2）和八甲基环四硅氧烷（D4）。在间歇反应器中进行了吸附动力学和等温线。据观察，进入多孔材料的传质是更迅速的活性炭比沸石和硅胶，与材料的多孔结构一致。此外，发现D4比L2更易吸附，这是由于固体表面与环状化合物（D4）的物理结构之间可能的相互作用。研究了湿度和温度对微生物降解的影响。温度的升高降低了吸附容量。在干空气和70%湿空气条件下考察了湿度对吸附的影响。活性炭和沸石的吸附容量没有显着差异，但硅胶的传质显着下降。对于吸附等温线，最大的消除能力，得到与活性炭材料，并直接关系到的多孔结构。为此，选择活性炭布作为吸附-脱附的动力学设计对象.热加热用于实现再生过程。已完成初始循环，表明工艺稳定。
Siloxanes are widely used in different applications: health care, dry cleaning, household products, paints and coatings, paper, personal care, for example. This explains their prevalence in the environment. Because of their volatile nature, most of the time they are dispersed in the atmosphere, but they can also be present in the slurry from landfills. During anaerobic digestion, when the temperature goes up to 60 °C, siloxanes are volatilized, forming part of the biogas. Operational problems using biogas to produce energy, heat and hydrogen have been identified. At high temperatures the siloxanes are transformed into silicate dioxide (commonly called sand transmission). These white deposits may adhere to metal or catalytic substrate surfaces, seriously reducing equipment efficiency, and this can be a reason for changing equipment warranties. Consequently, elimination of siloxanes has become very important. Unfortunately, relatively little information can be found on this subject. Nevertheless some authors have described different analytical methods for siloxane quantification, and recent studies have looked at the presence of siloxanes in landfills and the restriction on the energy recovery equipment using the biogas produced. The growing consumption of siloxanes and silicones in industrial processes consequently increase their prevalence in the environment, hampering the use of biogas as a source of ‘green energy’. Therefore, the principal focus of this study is the treatment of siloxanes. Their elimination was carried out using an adsorption process with four different porous materials: activated carbon cloths (ACC), granular activated carbon (GAC), zeolite and silica gel. Two representative siloxane compounds were used in this study, hexamethyldisiloxane (L2) and octamethylcyclotetrasiloxane (D4). Adsorption kinetics and isotherms in batch reactors were performed. It was observed that the mass transfer into the porous material was more rapid for the activated carbon than for the zeolite and silica gel, congruent with the porous structure of the material. Moreover, it was found that D4 is more adsorbable than L2, due to possible interactions between the solid surface and the physical structure of the cyclic compound (D4). The influence of humidity and temperature were also studied. The increase in the temperature reduced the adsorption capacities. The influence of humidity on the adsorption was investigated under dry air and humid air at 70%. No significant difference in the adsorption capacities was found for the activated carbon and for the zeolite, but for the silica gel the mass transfer decreased considerably. For the adsorption isotherms, the maximal capacity of elimination was obtained with the activated carbon materials and was directly related to the porous structure. Thus activated carbon cloth was chosen to design the adsorption– desorption processes in a dynamic system. Thermal heating was used to achieve the regeneration process. Initial cycles have been accomplished and show the stability of the process.