Toward rational design of amines for CO2 capture: Substituent effect on kinetic process for the reaction of monoethanolamine with CO2

Amines have been considered as promising candidates for post-combustion CO₂ capture. A mechanistic understanding for the chemical processes involved in the capture and release of CO₂ is important for the rational design of amines. In this study, the structural effects of amines on the kinetic competition among three typical products (carbamates, carbamic acids and bicarbonate) from amines + CO₂ were investigated, in contrast to previous thermodynamic studies to tune the reaction of amines with CO₂ based on desirable reaction enthalpy and reaction stoichiometry. We used a quantum chemical method to calculate the activation energies (E_a) for the reactions of a range of substituted monoethanolamines with CO₂ covering three pathways to the three products. The results indicate that the formation of carbamates is the most favorable, among the three considered products. In addition, we found that the E_a values for all pathways linearly correlate with pK_a of amines, and more importantly, the kinetic competition between carbamate and bicarbonate absorption pathways varies with pK_a of the amines, i.e. stronger basicity results in less difference in E_a. These results highlight the importance of the consideration of kinetic competition among different reaction pathways in amine design.     

Probing the potential of polyester for CO2 capture

Global warming, the major environmental issue confronted by humanity today, is caused by rising level of green house gases. Carbon capture and storage technologies offer potential for tapering CO2 emission in the atmosphere. Adsorption is believed to be a promising technology for CO2 capture. For this purpose, a polyester was synthesized by polycondensation of1,3,5-benzenetricarbonyl trichloride and cyanuric acid in pyridine and dichloromethane mixture. The polymer was then characterized using FT-IR, TGA, BET surface area and pore size analysis, FESEM and CO2 adsorption measurements. The CO2 adsorption capacities of the polyester were evaluated at a pressure of 1 bar and two different temperatures（273 and 298 K）.The performance of these materials to adsorb CO2 at atmospheric pressure was measured by optimum CO2 uptake of 0.244 mmol/g at 273 K. The synthesized polyester, therefore, has the potential to be exploited as CO2 adsorbent in pre-combustion capture process.     

Synthesis, characterization and experimental investigation of Cu-BTC as CO2 adsorbent from flue gas

Porous Cu-BTC material was synthesized by the solvothermal method. Powder X-ray diffraction (PXRD) was used to test the phase purity of the synthesized material and investigate its structural stability under the influence of flue gas components. The thermal stability of the material was determined through thermal gravimetric (TG) analysis. Scanning electron microscopy (SEM) was employed to study the microstructure of the material. Cu-BTC was demonstrated not only to have high CO₂ adsorption capacity but also good selectivity of CO₂ over N₂ by means of packed bed tests. The adsorption capacity of Cu-BTC for CO₂ was about 69 mL/g at 22°C. The influence of the main flue gas components on the CO₂ capacity of the material were discussed as well.     

粉煤灰用于碳捕集、利用及封存的研究进展

总结了国内外粉煤灰用于CO₂捕集、利用和封存的不同技术研究进展,同时对今后的研究和机遇进行了展望.粉煤灰自身可通过直接干式、半干式、湿式和间接方法对CO₂进行矿化捕集封存,在CO₂矿化的同时降低粉煤灰自身重金属的浸出,并且矿化后的粉煤灰因有效降低游离CaO和MgO的含量而更适合于制作混凝土添加剂.粉煤灰也可制成活性炭、沸石和多孔二氧化硅等产品,并对CO₂进行物理吸附捕集,制成产品的类型主要取决于粉煤灰自身的成分组成和理化性质.在CO₂利用方面,粉煤灰除了可拓展建材的利用途径外,还可制作CO₂多种化学工艺所需催化剂或催化剂载体,以及制作新型材料拟薄水铝石等.我国“双碳”目标的提出及燃煤电厂粉煤灰自身的理化特性为粉煤灰提供了一条新的综合利用途径.     

以粉煤灰为原料制备低温CO2吸附剂的工艺参数优化

利用高铝粉煤灰预脱硅液作为载体原料,通过使用胺基化合物对载体改性制备低温CO_2吸附剂.应用6 sigma中的工具,对制备工艺进行优化,得到理想的吸附剂,并对吸附剂样品进行表征.结果表明制备的CO_2吸附剂表现出良好的CO_2吸附性能.此类CO_2吸附剂具有吸附容量高(160 mg·g~(-1))、吸附速率快、对设备腐蚀低、成本低廉等特点,是一种极具工业应用潜力的CO_2吸附剂.     

PEI改性生物炭的制备及对CO2吸附性能的评价

采用超声辅助-水热法将聚乙烯亚胺（PEI）成功接枝到玉米芯生物炭表面,制备了PEI改性生物炭材料（PBC）,并通过X射线衍射（XRD）、扫描电子显微镜（SEM）、比表面积分析仪和傅里叶红外光谱仪（FTIR）等方法对其表征.结果表明,虽然PEI通过CN、C-N和离子键与生物炭表面的活性基团链接,但制备的PBC材料仍保持原生炭的无定型结构和形貌,且比表面积高达928.1 m²·g^-1.同时,还研究了PBC的吸附性能和热力学行为,结果表明,吸附过程符合Langmuir等温吸附机制,属于微孔单层吸附过程,而且随温度的降低,吸附量增大,在10、20和30℃时,饱和吸附量（Q_m）分别为6.47、4.75和2.64 mmol·g^-1.此外,PBC重复利用性能良好,容易实现热再生,即使循环利用10次,吸附性能也无显著变化（p>0.05）,且穿透吸附量（Q_B）保持在2.6~2.7 mmol·g^-1.     

低浓度CO2在聚苯胺/Y分子筛复合材料上的吸附

根据原位聚合方法将不同量的苯胺分别聚合在Y分子筛上,得到3种聚苯胺(PANI)/Y分子筛复合材料PANI-Y~(-1)、PANI-Y-2及PANI-Y-3,用傅立叶红外及氮气吸附实验表征了材料的结构特征,探讨了复合材料对常压下低浓度CO_2的吸附及再生性能.结果表明,苯胺在Y分子筛上成功聚合,复合材料的比表面积分别为52、54和35 m2·g~(-1),孔道由大孔和少量中孔组成,微孔极少.PANI负载量越大,材料的孔容越低.20℃下,初始体积分数为10%的CO_2在复合材料与Y分子筛上的吸附符合Logistic模型,吸附量的顺序为PANI-Y-2(2.09 mmol·g~(-1))PANI-Y-3(1.79 mmol·g~(-1))PANI-Y~(-1)(1.07 mmol·g~(-1))Y分子筛(0.80 mmol·g~(-1)),复合材料对CO_2的吸附受PANI负载量和比表面积的共同影响.在2%~10%的范围内,CO_2在复合材料上的吸附量随初始体积分数增加而增加;在25~65℃下,吸附量随温度升高而降低.80℃下,PANI-Y-2的4次热再生效率较差,仅68%;采用氨水/热再生相结合的方式脱附CO_2,再生率提高到94%.     

小浪底水库影响下的黄河花园口站和小浪底站pCO2特征及扩散通量

于2011年11月至2012年10月在黄河小浪底站和花园口站进行连续采样分析,根据亨利定律计算出表层水体二氧化碳分压(p CO2),研究了在小浪底水库"水沙调控"的影响下黄河花园口站和小浪底站表层水体p CO2特征及水-气CO2通量.结果表明,在小浪底水库正常调度期间,小浪底站表层水体p CO2在82~195 Pa之间,花园口站表层水体p CO2在99~228 Pa之间,且花园口站表层水体p CO2均高于同期的小浪底站;在小浪底水库调水调沙期间,两个水文站均表现为水库泄水期间的表层水体p CO2明显低于水库排沙期间的表层水体p CO2.无论是在小浪底水库正常调度期间还是在调水调沙期间,两个水文站表层水体p CO2均与DIC含量呈现显著的正相关关系.8、9月Ep CO2/AOU的比值高于生物好氧呼吸作用控制水体p CO2的理论下限0.62,因此8、9月生物好氧呼吸作用对水体p CO2的贡献比较明显.从全年来看小浪底站和花园口站平均水-气CO2扩散通量分别为0.486μmol·(m2·s)-1和0.588μmol·(m2·s)-1;在水库正常调度期间花园口站水-气CO2扩散通量明显高于同期的小浪底站;在小浪底水库调水调沙期间两个水文站均表现为水库泄水期间的水-气CO2扩散通量明显低于水库排沙期间的水-气CO2扩散通量.     

CO2 adsorption using TiO2 composite polymeric membranes: A kinetic study

CO₂ is the main greenhouse gas which causes global climatic changes on larger scale. Many techniques have been utilised to capture CO₂. Membrane gas separation is a fast growing CO₂ capture technique, particularly gas separation by composite membranes. The separation of CO₂ by a membrane is not just a process to physically sieve out of CO₂ through the controlled membrane pore size. It mainly depends upon diffusion and solubility of gases, particularly for composite dense membranes. The blended components in composite membranes have a high capability to adsorb CO₂. The adsorption kinetics of the gases may directly affect diffusion and solubility. In this study, we have investigated the adsorption behaviour of CO₂ in pure and composite membranes to explore the complete understanding of diffusion and solubility of CO₂ through membranes. Pure cellulose acetate (CA) and cellulose acetate-titania nanoparticle (CA-TiO₂) composite membranes were fabricated and characterised using SEM and FTIR analysis. The results indicated that the blended CA-TiO₂ membrane adsorbed more quantity of CO₂ gas as compared to pure CA membrane. The high CO₂ adsorption capacity may enhance the diffusion and solubility of CO₂ in the CA-TiO₂ composite membrane, which results in a better CO₂ separation. The experimental data was modelled by Pseudo first-order, pseudo second order and intra particle diffusion models. According to correlation factor R², the Pseudo second order model was fitted well with experimental data. The intra particle diffusion model revealed that adsorption in dense membranes was not solely consisting of intra particle diffusion.     

Optimization of CO2 adsorption capacity and cyclical adsorption/desorption on tetraethylenepentamine-supported surface-modified hydrotalcite

The objective of this research was to investigate CO_2adsorption capacity of tetraethylenepentamine-functionalized basic-modified calcined hydrotalcite(TEPA/b-c HT)sorbents at atmospheric pressure formed under varying TEPA loading levels,temperatures,sorbent weight to total gaseous flow rate(W/F)ratios and CO_2concentrations in the influent gas.The TEPA/b-c HT sorbents were characterized by means of X-ray diffraction(XRD),Fourier transform infrared spectrometry(FT–IR),thermal gravimetric analysis(TGA),Brunauer–Emmet–Teller(BET)analysis of nitrogen(N_2)adsorption/desorption and carbon–hydrogen–nitrogen(CHN)elemental analysis.Moreover,a full 2~4factorial design with three central points at a 95%confidence interval was used to screen important factor(s)on the CO_2adsorption capacity.It revealed that85.0%variation in the capacity came from the influence of four main factors and the15.0%one was from their interactions.A face-centered central composite design response surface method(FCCCD–RSM)was then employed to optimize the condition,the maximal capacity of 5.5–6.1 mmol/g was achieved when operating with a TEPA loading level of 39%–49%(W/W),temperature of 76–90°C,W/F ratio of 1.7–2.60(g·sec)/cm~3and CO_2concentration of 27%–41%(V/V).The model fitted sufficiently the experimental data with an error range of±1.5%.From cyclical adsorption/desorption and selectivity at the optimal condition,the 40%TEPA/b-c HT still expressed its effective performance after eight cycles.     

大气14CO2的时空分异特征及其在化石源CO2示踪中的应用

大气CO₂中放射性碳同位素(¹⁴C)的水平可以反映化石源CO₂的影响程度,这对于评估我国目前化石源CO₂的排放状况和制定节能减排政策具有重要的指导意义。本文在概述大气¹⁴CO₂采样和分析方法的基础上,简要介绍了大气¹⁴CO₂观测的起源和主要的源汇过程,重点论述了大气¹⁴CO₂的时空分异特征及其驱动因素;阐述了化石源CO₂浓度的估算方法及¹⁴CO₂在国内外化石源CO₂示踪中的应用现状,并对大气¹⁴CO₂观测在我国化石源CO₂示踪中的应用前景进行了展望;旨在为我国正确地开展大气¹⁴CO₂的观测研究,深刻地理解特定区域大气¹⁴CO₂的时空分异特征和化石源CO₂的分布状况提供参考。     

填料塔中DBU溶液对CO2脱除率的实验研究

温室效应日益受到各国政府和科学家的关注,如何实现CO2捕集成为温室气体减排的关键.本文通过搭建吸收CO2的填料塔,研究1,8-二氮杂双环[5,4,0]十一碳-7-烯(DBU)溶液浓度、DBU溶液流量、气体流量、液气比、入口CO2浓度、气体温度和填料层高度对CO2脱除率的影响.结果发现CO2脱除率随DBU溶液浓度、DBU溶液流量和液气比的增大而增大;随气体流量和入口CO2浓度的增加而下降;气体温度在30~40℃时,CO2脱除率达到最高;填料层高度对CO2脱除率也有一定影响,随着填料层高度的增加,CO2脱除率只有小幅增大,因此实际应用中要综合考虑脱除率和经济性,选择合适的填料高度.     

Enhanced CO2 adsorptive performance of PEI/SBA-15 adsorbent using phosphate ester based surfactants as additives

In this study,a series of polyetherimide/SBA-15: 2-D hexagonal P6 mm,Santa Barbara USA(PEI/SBA-15) adsorbents modified by phosphoric ester based surfactants(including tri(2-ethylhexyl)phosphate(TEP),bis(2-ethylhexyl) phosphate(BEP) and trimethyl phosphonoacetate(TMPA))were prepared for CO_2 adsorption.Experimental results indicated that the addition of TEP and BEP had positive effects on CO_2 adsorption capacity over PEI/SBA-15.In particular,the CO_2 adsorption amount could be improved by around 20% for 45PEI–5TEP/SBA-15 compared to the additive-free adsorbent.This could be attributed to the decrease of CO_2 diffusion resistance in the PEI bulk network due to the interactions between TEP and loaded PEI molecules,which was further confirmed by adsorption kinetics results.In addition,it was also found that the cyclic performance of the TEP-modified adsorbent was better than the surfactant-free one.This could be due to two main reasons,based on the results of in situ DRIFT and TG-DSC tests.First and more importantly,adsorbed CO_2 species could be desorbed more rapidly over TEP-modified adsorbent during the thermal desorption process.Furthermore,the enhanced thermal stability after TEP addition ensured lower degradation of amine groups during adsorption/desorption cycles.     

新安江水库二氧化碳排放的时空变化特征

新安江水库是我国华东地区最大的水库,面积580 km2,平均深度30 m,水库水体处于中贫营养状态.为了研究新安江水库中CO_2排放的时空变化特征,2014年12月至2015年12月采用静态浮箱法收集水库表面以分子扩散方式排放的CO_2,使用气相色谱仪分析CO_2浓度.结果表明,新安江水库CO_2排放通量从上游入库河流[(120.39±135.41)mg·(m~2·h)~(-1)]至库区主体[(36.65~61.94)mg·(m~2·h)~(-1)]呈下降趋势,而大坝下游河流中CO_2排放通量[(1 535.00±1 447.46)mg·(m~2·h)~(-1)]显著增加,约分别是上游入库河流和库区主体的13倍和25~42倍.但随着与大坝距离增加,大坝下游河流中CO_2排放通量显著下降,如7 km处的CO_2排放通量仅为出库水体处的20%.在库区主体中,CO_2排放通量具有明显的季节变化:CO_2排放通量在秋、冬季时为正值,最大值出现在冬季(12月或1月),说明此时库区表层水体是CO_2排放源;而CO_2排放通量在春、夏季为负值,最小值出现在春季(3、4或5月),说明此时库区表层水体是CO_2吸收汇,这可能与春、夏季时水体中藻类繁殖有关.所以,在调查水库表面CO_2排放时,应对水库的上游入库河流、库区主体和坝下河流进行全面长期的观测,才能避免低估水库中CO_2排放总量.     

Breakthrough CO2 adsorption in bio-based activated carbons

In this work, the effects of different methods of activation on CO₂ adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO₂ activation and Potassium hydroxide (KOH) activation. CO₂ adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25–65°C and inlet CO₂ concentration range of 10–30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N₂ and CO₂ adsorption at 77 and 273 K, respectively. Central composite design was used to evaluate the combined effects of temperature and concentration of CO₂ on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm³/g and surface area of 1400 m²/g had the highest CO₂ adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO₂ and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO₂ activated carbons remained remarkably stable after 50 cycles with low temperature (160°C) regeneration.     

Mesoporous carbon adsorbents from melamine-formaldehyde resin using nanocasting technique for CO2 adsorption

Mesoporous carbon adsorbents, having high nitrogen content, were synthesized via nanocasting technique with melamine–formaldehyde resin as precursor and mesoporous silica as template. A series of adsorbents were prepared by varying the carbonization temperature from 400 to 700°C. Adsorbents were characterized thoroughly by nitrogen sorption, X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), thermogravimetric analysis(TGA), elemental(CHN) analysis, Fourier transform infrared(FTIR) spectroscopy and Boehm titration. Carbonization temperature controlled the properties of the synthesized adsorbents ranging from surface area to their nitrogen content, which play major role in their application as adsorbents for CO_2 capture.The nanostructure of these materials was confirmed by XRD and TEM. Their nitrogen content decreased with an increase in carbonization temperature while other properties like surface area, pore volume, thermal stability and surface basicity increased with the carbonization temperature. These materials were evaluated for CO_2 adsorption by fixed-bed column adsorption experiments. Adsorbent synthesized at 700°C was found to have the highest surface area and surface basicity along with maximum CO_2 adsorption capacity among the synthesized adsorbents. Breakthrough time and CO_2 equilibrium adsorption capacity were investigated from the breakthrough curves and were found to decrease with increase in adsorption temperature. Adsorption process for carbon adsorbent–CO_2 system was found to be reversible with stable adsorption capacity over four consecutive adsorption–desorption cycles. From three isotherm models used to analyze the equilibrium data, Temkin isotherm model presented a nearly perfect fit implying the heterogeneous adsorbent surface.     

基于碳捕集的富氧燃煤烟气联合脱硫脱硝试验研究

富氧燃煤烟气压缩液化CO2的高压低温工况为NO氧化为易溶于水的NO2提供了十分有利的条件.基于小型高压吸收试验装置,采用配制的富氧燃煤模拟烟气,在高压常温下进行了NO、SO2、O2与H2O的吸收反应试验.根据反应前后的气液产物分析,测定了不同组分比例与不同压力下混合气体中NO与SO2的转化率.NO氧化与吸收试验表明,NO转化为HNO3的比率随压力升高而增加,在0.5 ～2 MPa之间增加很快,在2 ～3 MPa之间增速趋丁平缓,压力达3 MPa以上时,90％以上的NO均转化为稀硝酸,且初始NO浓度越高,NO的转化率越大.混合气体中同时存在5O2与NO的联合吸收试验发现,只有少量的NO转化成了NO3-,SO2向H2SO4的转化率随压力升高而增加,初始SO2浓度越大,转化率越高.分析表明,SO2与NO同时存在时SO2先行转化为SO3,NO充当了催化剂,但SO2转化为SO3的一次转化率小于35％,反应酸液产物的多次循环能使SO2的转化率达到90％以上.建议的工艺流程中需采用两座吸收反应塔顺序脱除SO2与NO并回收稀酸溶液,有望在富氧燃煤发电捕集CO2系统中降低脱硫脱硝成本,部分地弥补富氧燃烧机组发电成本的增加.     

MgO-based adsorbents for CO2 adsorption: Influence of structural and textural properties on the CO2 adsorption performance

A series of MgO-based adsorbents were prepared through solution–combustion synthesis and ball-milling process.The prepared MgO-based powders were characterized using X-ray diffraction,scanning electron microscopy,N_2 physisorption measurements,and employed as potential adsorbents for CO_2 adsorption.The influence of structural and textural properties of these adsorbents over the CO_2 adsorption behaviour was also investigated.The results showed that MgO-based products prepared by solution–combustion and ball-milling processes,were highly porous,fluffy,nanocrystalline structures in nature,which are unique physico-chemical properties that significantly contribute to enhance their CO_2 adsorption.It was found that the MgO synthesized by solution combustion process,using a molar ratio of urea to magnesium nitrate(2:1),and treated by ball-milling during 2.5 hr(MgO-BM2.5h),exhibited the maximum CO_2 adsorption capacity of 1.611 mmol/g at 25℃ and 1 atm,mainly via chemisorption.The CO_2 adsorption behaviour on the MgO-based adsorbents was correlated to their improved specific surface area,total pore volume,pore size distribution and crystallinity.The reusability of synthesized MgO-BM2.5h was confirmed by five consecutive CO_2adsorption–desorption times,without any significant loss of performance,that supports the potential of MgO-based adsorbent.The results confirmed that the special features of MgO prepared by solution–combustion and treated by ball-milling during 2.5 hr are favorable to be used as effective MgO-based adsorbent in post-combustion CO_2 capture technologies.     

水热溶剂对Cu/CeO2-TiO2催化CO2加氢制甲醇反应性能的影响

以高暴露（001）面锐钛矿TiO₂为载体,使用3种不同溶剂（甲醇、乙二醇和丙三醇）水热负载CeO₂,进而以CeO₂-TiO₂为载体采用硼氢化钠还原法负载Cu,合成Cu/CeO₂-TiO₂催化剂用于催化CO₂加氢制甲醇.XRD、SEM、BET、ICP-OES、XPS、H₂-TPR、EPR和CO₂-TPD等表征表明,以 甲醇/水为混合溶剂合成的CeO₂-TiO₂（CT-M）载体中CeO₂粒径较小、Ce³⁺浓度较高,更有利于Cu的负载与分散,形成紧密接触的三相界面;其负载Cu的催化剂CCT-M经焙烧、还原后形成的CuCeTi三相界面相互作用更强,可产生更多的表面Ce³⁺、氧空位和体相Ti³⁺,表面Ce³⁺、氧空位和体相Ti³⁺等缺陷有利于CO₂的吸附活化,较小粒径的Cu则可加速氢解离,因此,CCT-M具有更多的CO₂加氢反应活性位点,表现出最优的CO₂加氢产甲醇活性.     

腾格里沙漠民勤沙丘CO2浓度与昼夜变化规律研究

为查明沙漠区CO2浓度和对大气CO2的影响以及在全球碳循环中的作用,利用红外CO2监测仪于2009年9月对腾格里沙漠民勤实验点不同类型不同深度的沙层CO2含量变化进行了昼夜连续观测.根据12个钻孔CO2浓度的昼夜观测结果可知,民勤沙漠区不同观测点CO2浓度差异较大,各观测点昼夜CO2浓度变化在310×10-6～2 630×10-6之间;夜间沙层CO2浓度低,白天CO2浓度高;CO2浓度在深度上也有明显的差异,不同深度CO2浓度由大到小的顺序是:4 m(3m)2 m1m;与温带半湿润的西安地区相比,位于极端干旱区的民勤沙漠区CO2浓度显著低;CO2浓度昼夜变化明显,从当日09:00左右到次日09:00左右均呈现由低到高再到低的变化规律;在沙层水分一定的条件下,昼夜温度变化是造成沙层CO2浓度昼夜变化的主要原因,两者呈显著正相关关系;含水量较高沙层CO2浓度明显高于含水量较低沙层,沙层含水量高低是决定沙层CO2浓度的主要因素;4 m深度以上沙层CO2浓度均高于地表空气CO2浓度,表明极端干旱的沙漠区可能是CO2的来源区,也指示环境恶劣的裸露流动沙丘微生物活动产生的沙层CO2浓度仍然超过了大气CO2浓度.