新型Li_4SiO_4高温吸收CO_2的动力学研究

高温固体CO2吸收剂硅酸锂材料以其较高的吸收容量、优良的循环吸收稳定性成为研究热点。文中以廉价的、具有丰富孔结构的硅藻土和碳酸锂为原料,采用高温固相法于600℃下合成了可在高温直接吸收CO2的硅酸锂材料。XRD结果分析表明所制备的材料由Li4SiO4和少量的LiAlSi2O6相组成,用同步热重分析仪(TG-DSC)研究了在等温条件下硅酸锂材料吸收CO2的性能。用双指数模型拟合了硅酸锂材料吸收CO2的过程。结果表明:吸收CO2的温度不同,硅酸锂材料吸收CO2反应的控制步也不相同。表面反应速率常数与扩散速率常数的相对大小在很大程度上影响了硅酸锂材料吸收CO2的性能。     

Behaviors and kinetic models analysis of Li4SiO4 under various CO2 partial pressures

The absorption behaviors of Li₄SiO₄ sorbent under various CO₂ partial pressures and temperatures were investigated through numerical and experimental methods. It was found that Li₄SiO₄ showed poor absorption capacity at high temperatures (>525°C) under CO₂ partial pressure of 5066 Pa. This phenomenon was explained by the thermodynamic results from FactSage5.5 software. Meanwhile, a modified Jander‐Zhang model based on the double‐shell structure of the Li₄SiO₄ sorbent was developed to describe the absorption kinetic behaviors of CO₂ on Li₄SiO₄. The results showed that the modified Jander‐Zhang model could fit the kinetic experimental data well. Furthermore, the influence of steam on CO₂ absorption was also analyzed by the modified Jander‐Zhang model. The results showed that the activation energy in the absorption process with steam was smaller than that without steam, which indicated that the presence of steam could promote the CO₂ diffusion in product layer, therefore, improving the sorption capacity. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2153–2164, 2017     

Analysis of CO2 sorption/desorption kinetic behaviors and reaction mechanisms on Li4SiO4

The CO₂ sorption/desorption kinetic behaviors on Li₄SiO₄ were analyzed. The theoretical compositions of the sorption/desorption reactions were calculated using FactSage. The sorption/desorption process on Li₄SiO₄ was investigated by comparing the shrinking core, double exponential, and Avrami–Erofeev models. The Avrami–Erofeev model fits the kinetic thermogravimetric experimental data well and, together with the double‐shell mechanism, clearly explains the sorption/desorption mechanism. The sorption process is limited by the rate of the formation and growth of the crystals with double‐shell structure consisting of Li₂CO₃ and Li₂SiO₃. The whole desorption process is found to be controlled by the rate of the formation and growth of the Li₄SiO₄ crystals. Furthermore, the influence of steam on the CO₂ sorption process was analyzed. It has been observed that the presence of steam enhance the mobility of Li⁺ and, therefore, the rate of diffusion control stage. © 2012 American Institute of Chemical Engineers AIChE J, 59: 901–911, 2013     

硅酸锂吸收二氧化碳性能研究

通过高温固相反应法,合成出可在高温400～750℃之间直接吸收CO2的硅酸锂材料,借助热重分析仪研究了K元素的掺杂及CO2的浓度对硅酸锂材料性能的影响.试验结果表明,通过适当K元素的掺杂,能够提高硅酸锂材料吸收CO2的性能,当K元素的掺量x=0.02时,合成的硅酸锂材料在CO2气氛下于700℃保温20 min后,吸收量可达39％,吸收容量有明显提高.此外,气氛中CO2的浓度对硅酸锂材料吸收CO2的性能有较大影响.     

Strategies for CO2 capture from different CO2 emission sources by vacuum swing adsorption technology☆

Different VSA(Vacuum Swing Adsorption) cycles and process schemes have been evaluated to find suitable process configurations for effectively separating CO2 from flue gases from different industrial sectors. The cycles were studied using an adsorption simulator developed in our research group, which has been successfully used to predict experimental results over several years. Commercial zeolite APGIII and granular activated carbon were used as the adsorbents. Three-bed VSA cycles with- and without-product purge and 2-stage VSA systems have been investigated. It was found that for a feed gas containing 15% CO2(representing flue gas from power plants), high CO2 purities and recoveries could be obtained using a three-bed zeolite APGIII VSA unit for one stage capture, but with more stringent conditions such as deeper vacuum pressures of 1–3 k Pa. 2-stage VSA process operated in series allowed us to use simple process steps and operate at more realistic vacuum pressures. With a vacuum pressure of 10 k Pa, final CO2 purity of 95.3% with a recovery of 98.2% were obtained at specific power consumption of 0.55 MJ·(kg CO2)-1from feed gas containing15% CO2. These numbers compare very well with those obtained from a single stage process operating at1 k Pa vacuum pressure. The feed CO2 concentration was very influential in determining the desorption pressure necessary to achieve high separation efficiency. For feed gases containing N 30% CO2, a singlestage VSA capture process operating at moderate vacuum pressure and without a product purge, can achieve very high product purities and recoveries.     

高温下钙基吸附剂吸附CO2的研究

CaO基吸附剂是一种理想的CO2高温吸附剂。利用热重分析仪研究了由不同前体制备的CaO高温下对CO2的吸附性能。利用吸附仪测定了各吸附剂的比表面积等参数。实验发现CaO的最佳吸附温度范围为700—750℃;由CaC2O4.H2O制得的CaC2O4-CaO具有良好的吸附性能,在实验条件下,其吸附量为理论吸附量的89.1%;在较宽的CO2体积分数范围内,CaC2O4-CaO始终保持很高的吸附性能;吸收速率的大小受吸附剂比表面积、孔体积、孔结构等参数的共同影响。高温下,CaO基吸附剂吸附CO2的微观机理有待进一步研究。     

Effect of K2CO3 doping on CO2 sorption performance of silicate lithium-based sorbent prepared from citric acid treated sediment

In this paper, a low-cost and environmental-friendly leaching agent citric acid (C₆H₈O₇) was used to treat the sediment of Dianchi Lake (SDL) to synthesize lithium silicate (Li₄SiO₄) based CO₂ sorbent. The results were compared with that treated with strong acid. Moreover, the effects of preparation conditions, sorption conditions and desorption conditions on the CO₂ sorption performance of prepared Li₄SiO₄ were systematically studied. Under optimal conditions, the Li₄SiO₄ sorbent was successfully synthesized and its CO₂ sorption capacity reached 31.37% (mass), which is much higher than that synthesized from SDL treated with strong acid. It is speculated that the presence of some elements after C₆H₈O₇ treatment may promote the sorption of synthetic Li₄SiO₄ to CO₂. In addition, after doping with K₂CO₃, the CO₂ uptake increases from the original 12.02% and 22.12% to 23.96% and 32.41% (mass) under the 20% and 50% CO₂ partial pressure, respectively. More importantly, after doping K₂CO₃, the synthesized Li₄SiO₄ has a high cyclic stability under the low CO₂ partial pressure.     

乙二胺不同掺杂模式下多孔有机聚合物对CO2的吸附

利用嫁接法和浸渍法分别在以1,3,5-三苯基苯为单体的有机多孔聚合物（nTPB）上成功掺杂乙二胺,分别研究了乙二胺的不同掺杂模式对多孔聚合物的结构性质以及CO₂吸附性能的影响。结果表明,嫁接法和浸渍法皆可在nTPB上均匀掺杂乙二胺,且nTPB的比表面积和孔容均有所下降。在乙二胺掺杂量相同的前提下,由于浸渍法完全利用nTPB的孔道吸收乙二胺,nTPB的孔道堵塞更明显。两种掺杂乙二胺的模式均可显著提升nTPB对CO₂的吸附选择性,但只有嫁接法对nTPB的CO₂吸附量有明显促进（从4.4 mmol/g升高为5.2 mmol/g;0℃,10⁵ Pa）;浸渍法由于过度堵塞nTPB孔道,且乙二胺的吸附位点被包埋,导致CO₂的吸附量反而下降（仅有3.4 mmol/g;0℃,10⁵ Pa）。此外,嫁接法掺杂乙二胺的nTPB表现出与nTPB基质相同的良好重复利用性。     

Dynamics adsorption of the enhanced CH4 recovery by CO2 injection

The dynamic adsorption isotherms of CO₂-EGR were measured by using an Intelligent Gravimetric Analysis system. In the initial CO₂ injecting stage, all the injected CO₂ enters into the adsorbent and the mole fraction of CH₄ in the gas phase () is maintained at 1.0. The CH₄ recovery factor () increases. The duration of this stage (t_CD) depends on the selectivity of CO₂ over CH₄ (). An adsorbent with large has long t_CD. In the second stage, the injected CO₂ competes with CH₄ for adsorption. The cumulative of the second stage is much larger than that of the initial stage. However, decreases sharply. in the whole CO₂ injection is always larger than that before CO₂ injection, suggesting that CH₄ desorption results from the displacement of CO₂ rather than from pressure depletion.     

煤系高岭土为硅源制备硅酸锂及其对CO_2的吸附性能

以煤系高岭土酸处理除铝后剩余的物料为硅源,与Li2CO3通过高温固相反应合成了可在高温直接吸收CO2的硅酸锂材料。采用扫描电子显微镜（SEM）、X射线粉末衍射仪（XRD）分别观察和分析了所合成材料的表面形貌与结构特征,并使用差热-热重联用分析仪（DTA-TG）研究了硅酸锂材料吸收CO2的性能。实验结果表明,该材料具有较好的吸收CO2性能,吸收量可达31.07%（质量分数）。与以市售SiO2为硅源制取的硅酸锂相比,低温时高岭土-硅酸锂具有更快的吸收速率,具有明显的低温吸收CO2优势。     

CO hydrogenation over a RhVO4/SiO2 catalyst after H2 reduction

The hydrogenation of CO over a RhVO₄/SiO₂ catalyst has been investigated after H₂ reduction at 773 K. A strong metal–oxide interaction (SMOI) induced by the decomposition of RhVO₄ in H₂ enhanced not only the selectivity to C₂ oxygenates but also the CO conversion drastically, compared with an unpromoted Rh/SiO₂ catalyst. The selectivity of the RhVO₄/SiO₂ catalyst was similar to those of conventional V₂O₅‐promoted Rh/SiO₂ catalysts (V₂O₅–Rh/SiO₂), but the CO dissociation activity (and TOF) was much higher than for V₂O₅–Rh/SiO₂, and hence the yield of C₂ oxygenates was increased. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of different organic compounds on the preparation of CaO-based CO2 sorbents derived from wet mixing combustion synthesis

CaO based sorbents have great potential for commercial use to capture CO_2 of power plants. In the demand of producing sorbents with better cyclic performance, CaO-based sorbents derived from different kinds of calcium precursors, containing calcium carbonate(CC-CaO), calcium gluconate monohydrate(CG-CaO), calcium citrate(CCi-CaO) and calcium acetate monohydrate(CA-CaO), were tested cyclically and compared using simultaneous thermal analyzer(STA). And further study was conducted on the sorbents modified with citric acid monohydrate and 50% gluconic acid solution by wet mixing combustion synthesis. The modified sorbents showed better performance and higher pore parameters as well as porous microstructure with more organic acid added. After 20 cycles of carbonation and calcination, the C2CCi8(CaO: citric acid = 2:8 by mass ratio) and C2G8(CaO: gluconic acid = 2:8 by mass ratio) sorbent possess CO_2 capture capacity of 0.45 g·g~(-1)(g CO_2 per g sorbents) and 0.52 g·g~(-1) respectively. The citric acid was more effective for modification than gluconic acid for extended 50 cycles. Furthermore, good linear relationship between CaO conversion and specific surface area as well as pore volume were determined, of which the specific surface area showed closer correlation with CaO conversion.     

金属氧化物掺杂对钙基吸附剂吸附CO_2性能的影响

化石燃料火电厂排放的CO2约占全球CO2总排放量的1/3,采用化学吸附法直接脱除高温烟气中的CO2既可以减少系统的能量损失又可以保护环境。文中采用机械混合法制备金属氧化物掺杂的钙基吸附剂,并以静吸附量和CO2吸附率为评价指标,气相色谱为检测手段,在自制吸附剂评价装置上,研究不同金属氧化物的掺杂对钙基吸附剂吸附性性能的影响。实验表明,掺杂金属氧化物对钙基吸附剂的吸附性能有一定影响,其中质量分数为1%的Li2CO3掺杂的钙基吸附剂的静吸附容量与钙基吸附剂的理论吸附量比较接近,并且优于其他金属氧化物掺杂的钙基吸附剂。     

Ti(SO_4)_2/SiO_2催化合成油酸正丁酯

考察了 Ti(SO4 ) 2 /Si O2 在油酸丁酯合成反应中的催化性能 ,对影响酯化的条件进行了优化 ,优化条件如下 :0 .2 g Ti(SO4 ) 2 /g Si O2 ,油酸 0 .1 mol,丁醇 0 .2 mol,催化剂 1 g,反应温度 1 40°C,反应时间 6 0 min。优化条件下 ,油酸的酯化率 98%,收率 91 %。     

Li2O-CaO吸附剂吸附CO2的性能

采用机械混合法制备了Li2O-CaO吸附剂,在固定床管式反应器中研究了Li2O-CaO吸附剂的吸附性能,考察了吸附温度、空速及吸附剂粒径对静吸附容量的影响,确定了适宜的工艺条件,采用XRD和SEM对改进的钙基吸附剂进行了表征。结果表明,Li2O-CaO吸附剂对CO2有较好的吸附能力,在吸附温度600℃、空速8min-1、吸附剂粒径60～80目(0.18～0.28 mm)的条件下,静吸附容量达到了17.3891 mol/kg。     

锂离子电池正极材料Li2FeSiO4的研究进展

综述了合成Li2FeSiO4的方法,着重介绍了固相、溶胶-凝胶、水热、微波等几种主要的合成方法,并针对Li2FeSiO4电导率低的缺点,详细阐述了Li2FeSiO4电化学性能的改善方法,包括材料纳米化、孔状材料的制备、碳包覆和离子掺杂等。探讨了当前存在的问题及未来的研究方向。     

真空变温吸附捕集干烟道气中CO2的模拟研究

为减缓气候变化,减少CO₂的排放,对真空变温吸附(TVSA)从干烟道气中捕集CO₂进行了系统的研究。以沸石13X为吸附剂,设计了实验室规模的4塔连续进料的TVSA工艺,并建立数学模型进行数值模拟。模拟结果表明,通过四塔TVSA可获得纯度为97.54%,回收率为96.79%的CO₂产品气,其产率为1.7 mol· ( \mathrm{k} \mathrm{g} \text{?} \mathrm{a} \mathrm{d} \mathrm{s} ) ^-1·h^-1,能耗为3.14 \mathrm{M} \mathrm{J} · ( \mathrm{k} \mathrm{g} \text{?} \mathrm{C} {\mathrm{O}}_{\mathrm{2}} {)}_{}^{-\mathrm{1}} 。此外,考察了进料量、循环回流步骤时间、真空度对产品气纯度、回收率、吸附剂产率和工艺能耗的影响,并且分析了塔内压力与温度变化,详细探讨了塔内气固相浓度随轴向的分布。良好的工艺效果表明,TVSA有潜力成为一种能够生产高纯度高回收率的CO₂产品气,并具有良好经济效益的捕碳工艺。     

复合床层变压吸附法脱除合成气中微量CO和CO_2

采用分别装载活性炭和NA型吸附剂的复合床层的变压吸附工艺来脱除合成气中微量的CO和CO2,并利用Aspen-Adsim软件对其进行模拟和优化。模拟结果表明,吹扫气量对工艺性能有较大的影响,吹扫气由处在顺放步骤的吸附塔提供,因此在顺放步骤将床层压力降至较低压力,可获得较大的吹扫气量,此时的工艺性能也较优。模拟结果还表明,均压次数对工艺性能也有影响。在相同的顺放压降下,将变压吸附过程中的3次均压变为2次均压,可减少吸附剂用量,吸附剂产率更高,但塔底尾气量要相应增加。     

用于天然气吸附强化制氢的CO2吸附剂吸附率影响因素

采用TGA热重分析仪考察了温度、CO2浓度、升温速率及分解温度等操作条件和粒径对吸附剂吸附率的影响。研究表明,不同粒径的最佳吸附温度不同,粒径60～80μm吸附剂最佳吸附温度为650℃,吸附率达到75%;粒径1～1.8mm吸附剂最佳吸附温度为700℃,吸附率为67%。研究表明:对粒径60～80μm和1～1.8 mm的两种吸附剂,在CO2浓度分别高于30%、20%的情况下,提高CO2浓度不能提高CO2的吸附率。升温速率和分解温度对吸附率都有一定的影响。