高稳定性YSZ-LSCrF非对称平板氧分离膜和反应器性能研究

发布时间：2018-05-16 00:39

本文选题：相转化流延 + 非对称陶瓷透氧膜　；参考：《中国科学技术大学》2016年博士论文

【摘要】：陶瓷透氧膜材料由于能够同时传导氧离子和电子,在氧分压梯度下能够选择性地使氧气通过。将此种材料制备成透氧膜,可以用来从空气中分离氧气,从而改变传统的工业制氧工艺。将陶瓷透氧膜与甲烷部分氧化工艺耦合形成陶瓷膜反应器,能够显著降低合成气的生产成本,具有极大的经济与环境效益。透氧膜要实现商业化的应用,必须具有较高的氧渗透性能,同时在苛刻条件下具有足够的稳定性。实验室早期的研究中已经发现,将氧化钇稳定的氧化锆Zr0.84Y0.16O1.92(YSZ)与(LSCrF)复合形成的双相混合导体材料具有很好的稳定性。采用相转化法将其制备成具有较薄的功能层和厚的指状孔层构成的非对称结构的陶瓷膜,能够显著提高透氧膜的氧渗透性能。本论文致力于研究非对称平板陶瓷透氧膜的相转化法制备和其用于甲烷部分氧化膜反应器的研究。第一章主要介绍了陶瓷透氧膜的氧渗透原理和应用前景,以及相转化制备非对称结构膜的工艺,同时介绍了平板膜的研究现状。第二章研究了YSZ-LSCrF非对称陶瓷透氧膜的改进相转化法制备。由于相转化法制备的陶瓷透氧膜一般具有典型的非对称结构,包含致密功能层、指状孔层和覆盖在指状孔层表面的孔隙率较低的皮肤层。其中孔隙率较低的皮肤层对气体的输运阻力较大,因此去掉皮肤层是提高氧渗透性能(降低膜的浓差极化)的有效方法。因此,论文系统研究了采用石墨牺牲层的相转化流延法制备去皮肤层的YSZ-LSCrF非对称平板膜。制备过程中,上层采用石墨浆料,下层采用YSZ-LSCrF陶瓷浆料,采用双层流延技术,以水作为絮凝剂制备湿坯,并在空气中干燥。制备的生坯为三层结构：相对致密的皮肤层为石墨,指状孔层和海绵层为透氧膜材料陶瓷粉体。在后期的烧结制备过程中,石墨层燃烧除去,陶瓷粉体层保留下来,形成的非对称陶瓷透氧膜由厚度为850μm的指状孔层和150μm的致密功能层构成。由于制备过程中石墨牺牲的应用,皮肤层被完全除去,指状孔完全暴露出来,从而大大提高了多孔支撑体层的气体输运性能。为了进行比较,采用单层相转化流延方法制备了含皮肤层的非对称平板膜,并对两种结构的透氧膜进行了氧渗透性能测试和研究。测试过程中,透氧膜的致密侧暴露在空气中,多孔侧用30ml/min的He吹扫。实验结果显示,850℃,去皮肤层样品的氧渗透速率为1.08×10-8molcm-2s-1,而含皮肤层样品的为2.57×10-9molcm-2s-1。在air/CO梯度下对无皮肤层的样品进行氧渗透性能实验测试,其氧渗透速率在850℃高达2.26×10-7molcm-2s-1。本章工作的研究结果显示,采用改进的相转化流延技术和制备直孔结构多孔支撑体的非对称透氧膜,可显著降低透氧膜的浓差极化和提高透氧膜的氧渗透性能。透氧膜氧渗透速率的提高,对推动陶瓷透氧膜的工业化应用,具有重要意义。第三章研究了表面修饰对非对称平板膜的氧渗透行为的影响。采用改进的相转化流延法制备的非对称透氧膜,具有较薄的功能层和具有良好气体输运性能的多孔支撑体,这时透氧膜的氧渗透过程决速步骤将变为表面氧交换。因此,论文研究了膜的表面修饰,以提高表面氧交换速率和进一步提高直孔结构支撑体非对称膜的氧渗透性能。实验制备了三种样品,对于直孔结构多孔支撑体的YSZ-LSCrF非对称透氧膜,其致密侧采用丝网印刷方法制备一层同质的YSZ-LSCrF多孔层,指状孔内浸渍SDC纳米粒子。850℃时,在air/He梯度下,对于仅多孔侧修饰的样品,膜氧渗透速率为1.5×10-8molcm-2min-1;对于仅致密侧修饰的样品,氧渗透速率为2.81×10-8molcm-2min-1;对于致密膜的表面和多孔支撑体内孔均修饰的样品,氧渗透速率显著提高到3.83×10-8molcm-2min-1;与未进行表面修饰的样品相比较,氧渗透速率分别提高了～50%、～170%和～270%。当将吹扫气He切换成CO后,三种样品的氧渗透速率均提高了约一个数量级。对于两面修饰均修饰的样品,air/CO梯度下,850℃,氧渗透速率达到6.82×10-7mol cm-2 s-1,相当于1.00 ml (STP) cm-2 min-1。air/CO梯度下,氧渗透速率的提高,主要归因于膜两侧氧分压梯度的提高。实验结果还显示,测试后样品的相组成和微结构均没有变化。YSZ-LSCrF平板膜在空气/还原性气氛表现出了较高的稳定性和氧渗透速率,因此,YSZ-LSCrF透氧膜在膜反应器方面具有良好的应用前景。第四章研究了基于YSZ-LSCrF平板膜的甲烷部分氧化(partial oxidation of methane, POM)制合成气过程。将YSZ-LSCrF非对称平板膜用玻璃环封接剂固定在不锈钢底座上,膜的有效面积为13 cm2,在膜的下方填放Ni/Al2O3催化剂。甲烷是通过氧化-重整(oxidation/reforming)两个步骤转化为合成气的。氧化反应发生在膜的表面,CH4、H2、CO与从空气测渗透过来的氧发生反应,生成H2O、CO2；重整反应则在催化床上进行,CH4与氧化反应生成的H2O、CO2反应,转化为H2、CO。在800℃时CH4注入量为32ml/min时,CH4与渗透的O2比值接近2：1,CH4转化率高达90%,CO、H2的选择性也都超过95%,氧渗透速率为1.4 mlcm-2 min-1。透氧膜和催化剂在反应器条件下能保持良好的稳定,基于透氧膜的POM制合成气新工艺有望得到实际应用。第五章提出并实验研究了基于陶瓷透氧膜的合成气和氮气联产新工艺。实验中使用陶瓷透氧膜构建膜反应器,并将氧分离与甲烷部分氧化整合。将YSZ-LSCrF平板膜用玻璃封接剂固定在不锈钢底座上,膜的有效面积为6.8 cm2,在膜的下方填放Ni/Al2O3催化剂。实验发现：在850℃,空气注入速率55ml/min,甲烷注入速率22ml/min时,甲烷基本全部转化为合成气,合成气的生产速率达10ml/min,甲烷的转化率99%,氢气的选择性99%,一氧化碳的选择性也大于95%以上,同时在空气侧,获得的富氮气体中的氮气浓度高达99.9%。值得指出的是,基于透氧膜的合成气/氮气联产新工艺具有简单高效的特点,有可能在合成氨和尿素工业中得到应用。合成气中H2/CO比例接近2,也可以用于F-T反应制备液体燃料,此时氮气可以单独用来为其它反应提供氮源。第六章研究了非对称平板膜反应器短堆(short stack)的POM性能。短堆由两片YSZ-LSCrF平板膜构成,膜总有效面积为16cm2,Ni/Al2O3作为催化剂置于两片膜之间。在8000C、CH4注入量为30ml/min时(膜的另一侧暴露于环境空气),氧渗透速率为1.25ml cm-2min-1,CH4转化率达到76%,CO、H2的选择大于75%。与单片膜反应器相比,短堆反应器的POM性能略有降低,主要与短堆的结构设计(如催化剂的置放、反应气体的分布等)有关。短堆膜反应器的研究,验证了平板膜堆状反应器的可行性,为开发实用型POM膜反应器提供了重要基础。第七章对本论文的工作进行了总结,并对下一步的研发工作提出了建议,尤其对P O M膜反应器技术的发展和应用作了展望。
[Abstract]:The ceramic oxygen permeable membrane material is capable of conducting oxygen ions and electrons at the same time, and can selectively enable oxygen to pass through the oxygen partial pressure gradient. The material is prepared into oxygen permeable membrane, which can be used to separate oxygen from the air and change the traditional industrial oxygen making process. The ceramic membrane is coupled with the methane partial oxidation process to form a ceramic membrane. It can significantly reduce the production cost of synthetic gas and has great economic and environmental benefits. In order to realize commercial application, oxygen permeable membrane must have high oxygen permeability and sufficient stability under harsh conditions. In the early laboratory study, yttrium oxide stabilized zirconia Zr0.84Y0.16O1.92 (YS Z) the two phase mixed conductor material formed with (LSCrF) has good stability. The phase conversion method is used to prepare a ceramic membrane with a thin functional layer and a thick finger pore layer, which can significantly improve the oxygen permeation performance of the oxygen permeable membrane. In the first chapter, the oxygen permeation principle and application prospect of the ceramic oxygen permeable membrane were introduced, and the process of preparing asymmetric membrane by phase transformation was introduced, and the research status of the plate membrane was introduced. The second chapter studied the improved phase transformation of the YSZ-LSCrF asymmetric ceramic membrane. The ceramic permeable membrane prepared by the phase conversion method usually has a typical asymmetric structure, including dense functional layer, finger hole layer and low porosity skin layer covering the surface of the finger hole. In the case of low porosity, the resistance of the skin layer to gas is larger, so removing the skin layer is the increase of oxygen permeability. In this paper, the YSZ-LSCrF asymmetric flat membrane of the skin layer with graphite sacrificial layer is studied systematically. In the process of preparation, the upper layer is graphite slurry, the lower layer is YSZ-LSCrF ceramic paste, the double layer casting technology is used to prepare wet blank with water as flocculant. The air is dry. The prepared blank is three layers of structure: the relatively dense skin layer is graphite, the finger hole layer and the sponge layer are the ceramic powder of the oxygen permeable membrane. In the later sintering process, the graphite layer combustion is removed, the ceramic powder layer is retained, and the asymmetric ceramic permeable film is formed by the finger hole layer and 150 mu m thickness to the thickness. Due to the use of graphite sacrifice in the preparation process, the skin layer is completely removed and the finger hole is completely exposed, thus greatly improving the gas transport properties of the porous support layer. In order to compare, the asymmetric flat film containing the skin layer is prepared by the single-layer phase transformation method, and the two structures are made. The oxygen permeable membrane was tested and studied. During the test, the dense side of the oxygen permeable membrane was exposed in the air and the porous side was blown by 30ml/min He. The experimental results showed that the oxygen permeation rate of the skin layer samples was 1.08 x 10-8molcm-2s-1 at 850, and the skin layer samples were 2.57 x 10-9molcm-2s-1. without skin under the air/CO gradient. The oxygen permeation performance test of the skin layer samples shows that the oxygen permeation rate is up to 2.26 x 10-7molcm-2s-1. at 850. The results show that the improved phase conversion technique and the asymmetric oxygen permeable membrane prepared with the porous support with straight hole structure can significantly reduce the concentration polarization of the oxygen permeable film and increase the oxygen permeation of the oxygen permeable membrane. The improvement of permeability rate of oxygen permeable membrane is of great significance for promoting the industrial application of the ceramic oxygen permeable membrane. In the third chapter, the effect of surface modification on the oxygen permeation behavior of asymmetric flat film is studied. The asymmetric oxygen permeable membrane prepared by the improved phase transformation flow method has a thinner functional layer and good gas transport. The performance of the porous support, at this time the oxygen permeation process of the oxygen permeable membrane, will become surface oxygen exchange. Therefore, the surface modification of the membrane is studied to improve the oxygen exchange rate of the surface and to further improve the oxygen permeability of the asymmetric membrane of the straight hole structure. Three samples are prepared for the porous support of the straight hole structure. The YSZ-LSCrF asymmetric oxygen permeable membrane is used to prepare a homogeneous layer of YSZ-LSCrF porous layer on the compact side. When the finger hole is impregnated with SDC nanoparticles at.850 C, the oxygen permeation rate of the membrane only modified by the air/He gradient is 1.5 x 10-8molcm-2min-1; for the sample with only the compact side, the oxygen permeation rate is the same. 2.81 x 10-8molcm-2min-1, the oxygen permeation rate increased to 3.83 x 10-8molcm-2min-1 for the surface of the dense membrane and the pores in the porous support body, and the oxygen permeation rate increased to 50%, to 170% and to 270%., respectively, and the oxygen permeation of the three samples after the sweep gas He was switched to CO. At the air/CO gradient, the oxygen permeation rate reached 6.82 x 10-7mol cm-2 S-1 under the air/CO gradient, and the oxygen permeation rate increased under the gradient of 1 ml (STP) cm-2 min-1.air/CO, which was mainly attributable to the increase of the oxygen partial pressure gradient at the two side of the membrane. The experimental results also showed the test sample. The phase composition and microstructure of the.YSZ-LSCrF film have no changes in the air / reduction atmosphere. Therefore, the YSZ-LSCrF oxygen permeable membrane has a good application prospect in the membrane reactor. The fourth chapter studies the partial oxidation of methane based on the YSZ-LSCrF flat film (partial oxidation of metha). NE, POM) synthesis gas process. The YSZ-LSCrF asymmetric flat film is fixed on the stainless steel base with a glass ring sealing agent. The effective area of the film is 13 cm2, and the Ni/Al2O3 catalyst is filled under the membrane. Methane is converted to syngas through the two steps of oxidation reformer (oxidation/reforming). The oxidation reaction occurs on the surface of the membrane, CH4, H2, CO. In response to oxygen derived from the air, H2O, CO2 is generated, and the reformer is carried out on the catalytic bed. The H2O, CO2 reaction generated by CH4 and oxidation is converted to H2. When CH4 injection is 32ml/min at 800, the O2 ratio of CH4 to the osmosis is close to 2:1, and the conversion rate is up to 90%, and the oxygen permeation rate is also more than 95%. The 1.4 mlcm-2 min-1. oxygen permeable membrane and catalyst can maintain good stability under the reactor condition. The new process of synthesis gas based on POM of oxygen permeable membrane is expected to be applied. In the fifth chapter, a new process of CO production of synthetic gas and nitrogen based on ceramic oxygen permeable film is put forward and experimentally studied. The YSZ-LSCrF plate membrane is immobilized on the stainless steel base with a glass sealing agent. The effective area of the film is 6.8 cm2, and the Ni/Al2O3 catalyst is filled under the membrane. It is found that at 850, the air injection rate is 55ml/min, and the methane injection rate is 22ml/min, the methane is basically converted into synthetic gas. The production rate of gas is up to 10ml/min, the conversion rate of methane is 99%, the selectivity of hydrogen is 99%, the selectivity of carbon monoxide is more than 95%. At the same time, the nitrogen concentration in the nitrogen rich gas obtained at the air side is as high as 99.9%.. It is worth pointing out that the new process of syngas / nitrogen production based on oxygen permeable membrane has the characteristics of simple and efficient, and it is possible to be The application of synthetic ammonia and urea industry. The proportion of H2/CO in synthetic gas is close to 2, and it can also be used in F-T reaction to prepare liquid fuel. At this time nitrogen can be used to provide nitrogen source for other reactions. The sixth chapter studies the POM energy of the short pile (short stack) of asymmetric flat membrane reactor. The short pile is composed of two pieces of YSZ-LSCrF flat film, and the film is always available. The effect area is 16cm2, Ni/Al2O3 as catalyst is placed between two films. When 8000C, CH4 injection is 30ml/min (the other side of the membrane is exposed to ambient air), oxygen permeation rate is 1.25ml cm-2min-1, CH4 conversion rate reaches 76%, CO, H2 is larger than 75%. and monolithic membrane reactor, the POM performance of short reactor is slightly lower, mainly and short. The structural design of the reactor (such as the placement of the catalyst, the distribution of the reaction gas, etc.). The research on the short reactor reactor has verified the feasibility of the plate reactor reactor and provided an important basis for the development of the practical POM membrane reactor. The seventh chapters have made a summary of the work in this paper, and put forward some suggestions for the next step of research and development. The development and application of P O M membrane reactor technology are prospected.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ116.1

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