Effects of Different Concentrations of Sulfate Ions on Carbonate Crude Oil Desorption:Experimental Analysis and Molecular Simulation

Low salinity water containing sulfate ions can significantly alter the surface wettability of carbonate rocks.Nevertheless,the impact of sulfate concentration on the desorption of oil film on the surface of carbonate rock is still unknown.This study examines the variations in the wettability of the surface of carbonate rocks in solutions containing varying amounts of sodium sulfate and pure water.The problem is addressed in the framework of molecular dynamics simulation(Material Studio software)and experiments.The experiment’s findings demonstrate that sodium sulfate can increase the rate at which oil moisture is turned into water moisture.The final contact angle is smaller than that of pure water.The results of the simulations show that many water molecules travel down the water channel under the influence of several powerful forces,including the electrostatic force,the van der Waals force and hydrogen bond,crowding out the oil molecules on the calcite’s surface and causing the oil film to separate.The relative concentration curve of water and oil molecules indicates that the separation rate of the oil film on the surface of calcite increases with the number of sulfate ions.

Quantum Tunneling Enhanced Hydrogen Desorption from Graphene Surface: Atomic versus Molecular Mechanism

We study the desorption mechanism of hydrogen isotopes from graphene surface using first-principles calculations,with focus on the effects of quantum tunneling.At low temperatures,quantum tunneling plays a dominant role in the desorption process of both hydrogen monomers and dimers.In the case of dimer desorption,two types of mechanisms,namely the traditional one-step desorption in the form of molecules(molecular mechanism),and the two-step desorption in the form of individual atoms(atomic mechanism),are studied and compared.For the ortho-dimers,the dominant desorption mechanism is found to switch from the molecular mechanism to the atomic mechanism above a critical temperature,which is∼300K and 200K for H and D,respectively.

Accelerating H^(*)desorption of hollow Mo_(2)C nanoreactor via in-situ grown carbon dots for electrocatalytic hydrogen evolution

Molybdenum carbide(Mo_(2)C)is a promising non-noble metal electrocatalyst with electronic structures similar to Pt for hydrogen evolution reaction(HER).However,strong H^(*)adsorption at the Mo sites hinders the improvement of HER performance.Here,we synthesized monodisperse hollow Mo_(2)C nanoreactors,in which the carbon dots(CD)were in situ formed onto the surface of Mo_(2)C through carburization reactions.According to finite element simulation and analysis,the CD@Mo_(2)C possesses better mesoscale diffusion properties than Mo_(2)C alone.The optimized CD@Mo_(2)C nanoreactor demonstrates superior HER performance in alkaline electrolyte with a low overpotential of 57 mV at 10 mA cm^(−2),which is better than most Mo_(2)C-based electrocatalysts.Moreover,CD@Mo_(2)C exhibits excellent electrochemical stability during 240 h,confirmed by operando Raman and X-ray diffraction(XRD).Density functional theory(DFT)calculations show that carbon dots cause the d-band center of CD@Mo_(2)C to shift away from Fermi level,promoting water dissociation and the desorption of H^(*).This study provides a reasonable strategy towards high-activity Mo-based HER eletrocatalysts by modulating the strength of Mo–H bonds.

Pore structure of low‑permeability coal and its deformation characteristics during the adsorption–desorption of CH4/N2

The pore structure of coal plays a key role in controlling the storage and migration of CH4/N2.The pore structure of coal is an important indicator to measure the gas extraction capability and the gas displacement efect of N2 injection.The deformation characteristic of coal during adsorption–desorption of CH4/N2 is an important factor afecting CH4 pumpability and N2 injectability.The pore structure characteristics of low-permeability coal were obtained by fuid intrusion method and photoelectric radiation technology.The multistage and connectivity of coal pores were analyzed.Subsequently,a simultaneous test experiment of CH4/N2 adsorption–desorption and coal deformation was carried out.The deformation characteristics of coal were clarifed and a coal strain model was constructed.Finally,the applicability of low-permeability coal to N2 injection for CH4 displacement technology was investigated.The results show that the micropores and transition pores of coal samples are relatively developed.The pore morphology of coal is dominated by semi-open pores.The pore structure of coal is highly complex and heterogeneous.Transition pores,mesopores and macropores of coal have good connectivity,while micropores have poor connectivity.Under constant triaxial stress,the adsorption capacity of the coal for CH4 is greater than that for N2,and the deformation capacity of the coal for CH4 adsorption is greater than that for N2 adsorption.The axial strain,circumferential strain,and volumetric strain during the entire process of CH4 and N2 adsorption/desorption in the coal can be divided into three stages.Coal adsorption–desorption deformation has the characteristics of anisotropy and gas-diference.A strain model for the adsorption–desorption of CH4/N2 from coal was established by considering the expansion stress of adsorbed gas on the coal matrix,the compression stress of free gas on the coal matrix,and the expansion stress of free gas on micropore fractures.N2 has good injectability in low-permeability coal seams and has the dual functions of improving coal seam permeability and enhancing gas fow,which can signifcantly improve the efectiveness of low-permeability coal seam gas control and promote the efcient utilization of gas resources.

Experimental and Numerical Research on Water Transport during Adsorption and Desorption in Cement-Based Materials

The durability of cement-based materials is related to water transport and storage in their pore network under different humidity conditions.To understand the mechanism and characteristics of water adsorption and desorption processes from the microscopic scale,this study introduces different points of view for the pore space model generation and numerical simulation of water transport by considering the“ink-bottle”effect.On the basis of the pore structure parameters(i.e.,pore size distribution and porosity)of cement paste and mortar with water-binder ratios of 0.3,0.4 and 0.5 obtained via mercury intrusion porosimetry,randomly formed 3D pore space models are generated using two-phase transformation on Gaussian random fields and verified via image analysis method of mathematical morphology.Considering the Kelvin-Laplace equation and the influence of“ink-bottle”pores,two numerical calculation scenarios based on mathematical morphology are proposed and applied to the generated model to simulate the adsorption-desorption process.The simulated adsorption and desorption curves are close to those of the experiment,verifying the effectiveness of the developed model and methods.The obtained results characterize water transport in cement-based materials during the variation of relative humidity and further explain the hysteresis effect due to“ink-bottle”pores from the microscopic scale.

Study of the Temperature-Programmed Desorption of Carbon Dioxide (CO2) on Zeolites X Modified with Bivalent Cations

Study of physisorbed and chemisorbed carbon dioxide (CO2) species was carried out on the NaX zeolite modified by cationic exchanges with bivalent cations (Ca2+ and Ba2+) by temperature-programmed desorption of CO2 (CO2-TPD). Others results were obtained by infrared to complete the study. The results of this research showed, in the physisorption region (213 - 473 K), that the cationic exchanges on NaX zeolite with bivalent cations increase slightly the interactions of CO2 molecule with adsorbents and/or cationic site. Indeed, the desorption energies of physisorbed CO2 obtained on the reference zeolite NaX (13.5 kJ·mol-1) are lower than that of exchanged zeolites E-CaX and E-BaX (15.77 and 15.17 kJ·mol-1 respectively). In the chemisorbed CO2 region (573 - 873 K), the desorption energies related to desorbed species (bidentate carbonates: CO32-) on the exchanged zeolites E-CaX and E-BaX are about 81 kJ·mol-1, higher than the desorbed species (bicarbonates: HCO32-) on the reference R-NaX (62 kJ·mol-1). In addition, the exchanged E-BaX zeolite develops the secondary adsorption sites corresponding to bicarbonates species with desorption energies of 35 kJ·mol-1 lower to desorption energies of bicarbonates noted on the reference zeolite NaX.

Desorption of Methylene Blue Adsorbed on Activated Carbon from Cocoa Pod Shell

Environmental protection has become a concern for the world. For this reason, the objective of this work is to remove methylene blue adsorbed on activated carbon. The coal used comes from cocoa pod shells. Before pyrolysis, the shells were ground, sieved and impregnated with orthophosphoric acid. Before desorption, the activated carbons were initially saturated with MB. These saturated coals were brought into contact with a sodium chloride (NaCl) solution and then stirred. The evolution of the resorbed MB concentration was monitored by spectrophotometry. The desorption tests showed a remarkable elimination from the first 10 minutes. The desorption kinetics comprises two phases: a rapid kinetics between 0 and 30 minutes and a slow kinetics between 30 and 60 minutes. The desorption of the dye reaches a concentration aqual to 0.84 mg/l at pH = 4 at temperature = 80°C. For modeling, the coefficient of the Langmuir II model is greater than or equal to O.9893. The model of Langmuir III is less than or equal to 0.9373. The Freundlich model coefficient is 0.9842 or less. The desorption is thefore carried out on energy-homogeneous adsorption sites and without any interaction between the adsorbed cations of the dye. Experimental parameters such as pH, temperature and concentration of sodium chloride (NaCl) solution influence the desorption of MB. And the model of Langmuir II describes well the process of desorption of the MB.

计算机模拟在物理化学BET多分子层吸附理论教学中的应用

BET多分子层吸附理论抽象但应用广泛,BET公式的推导过程涉及较多数学知识,学生很难透彻理解BET公式的物理意义。面对比表面分析仪输出的吸附脱附等温线和比表面积,学生只能生搬硬套,难以达到预期的教学效果。本文利用计算机模拟气体分子在固体表面的吸附脱附过程,通过调整吸附脱附常数,可分别得到第I、II、III类吸附等温线;结合实时可视化使学生能直观看到气体分子在固体表面的吸附脱附动力学,从而能更好地理解BET理论。计算机模拟辅助教学还能活跃课堂气氛,实现教与学互动,激发学生的求知欲和科研兴趣,提高教学质量。

深层页岩纳米孔隙中气水微观动用机理

深层页岩气已成为我国天然气产量增长最现实的领域之一。已有研究结果证实深层页岩纳米孔隙发育,但页岩储层在高温高压含水条件下气水的动用复杂程度加剧。传统页岩岩心尺度的解吸和驱替实验成本高、周期长,难以解析纳米孔隙中气水在深层储层条件下的微观动用机理。为此,基于分子模拟方法,在考虑气水质量扩散传递的基础上,提出了1套页岩气水动用模拟方法,并模拟了深层页岩双重介质复合纳米孔隙中的甲烷和水分在2种不同模式下的动用机理,并量化了甲烷吸附气、溶解气和自由气,揭示了孔隙水和甲烷不同赋存状态的微观动用机理。研究结果表明:①页岩中伊利石对甲烷的亲和性强于干酪根,伊利石亲水性远大于干酪根;②2种动用模式下,伊利石中赋存的水分基本不发生动用,干酪根表面水分团簇可发生动用;③双重介质复合纳米孔隙中,甲烷的自由气动用率最大,溶解气和吸附气动用率较低,是后期页岩气储量挖潜的重要潜在资源。结论认为,深层页岩纳米孔隙中气水的微观动用理论研究对深层页岩气可采储量评估、产能评价和提高采收率等方面具有重要理论意义。

基于全生命周期的污油泥热脱附处理技术评价

基于全生命周期评价(LCA)软件eFootprint和国内典型污油泥热脱附处理实际,从绿色和可持续性两个方面对污油泥热脱附技术进行评价。结果表明:污油泥热脱附处理过程中,主要评价指标按所产生的环境影响由大到小排列依次为可吸入无机物(RI)、富营养化潜值(EP)、竞争-土地使用(CLU)、臭氧层消耗潜值(ODP)和水资源消耗(WU);回收油和天然气是初级能源消耗(PED)、非生物质资源消耗潜值(ADP)、WU、全球增温潜势(GWP)、ODP等11项评价指标的主要贡献因素,蒸汽是影响RI的最主要因素;污油泥热脱附处理产生的回收油能够抵消热脱附处理过程的部分能源和资源消耗,从而减小PED、ADP、GWP等评价指标的数值;为了进一步提升污油泥热脱附处理技术的绿色和可持续性,建议提高能源效率,减少蒸汽消耗,回收蒸汽余热,优化尾气净化系统和器具清洗系统,减少废水排放和水分挥发。

开采保护层与预抽煤层瓦斯防突效果分析

为比较开采保护层与预抽煤层瓦斯防突效果,以1124(3)运顺开采保护层段和预抽煤层瓦斯段煤巷掘进为试验对象,统计了试验地点煤巷掘进期间残余瓦斯含量、钻屑瓦斯解吸指标K1、钻屑量等防突指标,采用假设检验方法推断了各防突指标是否有差别,分析了开采保护层段和预抽煤层瓦斯段各防突指标产生差别的原因,验证了开采保护层区域防突措施比预抽煤层瓦斯区域防突措施更加安全可靠。

南川地区浅层常压页岩气吸附解吸机理与开发实践

中国浅层常压页岩气勘探开发尚处于探索阶段,目前在四川盆地及周缘地区实施的多口浅层页岩气井钻遇含气层显示良好,初步揭示了浅层页岩气具有较大的勘探开发潜力。但浅层常压页岩中天然气的赋存状态以吸附气为主,勘探开发面临吸附解吸规律不清、针对性排采工艺尚待建立等问题。为此,以重庆市南川地区武隆区块常压页岩气田为对象,选取不同埋深条件下的岩心样品,开展了页岩储层评价与室内等温吸附实验,基于等温吸附曲线,建立了浅层页岩气吸附解吸模型并划分了吸附气3个解吸阶段,明确了浅层常压页岩气吸附解吸机理及其影响因素。研究结果表明:(1)浅层常压页岩气等温吸附曲线呈“厂”字形特征,随着储层压力下降,解吸速率从缓慢解吸突变至快速解吸;(2)通过对解吸效率曲线的曲率进行求解,可得到解吸速率突变拐点对应的“敏感解吸压力”,盆外浅层常压页岩气敏感解吸压力一般介于1.8~2.5 MPa;(3) PD1HF井开展降流压解吸试验,通过人工举升将井底流压降至2.5 MPa以下时吸附气快速解吸释放,气井产能达到原来的5倍以上,实现了浅层常压页岩气井产能的重大突破。结论认为,南川地区武隆区块浅层常压页岩气吸附解吸特征的明确及其开发实践的成功,对推动南川地区浅层常压页岩气效益开发及国内同类型浅层常压页岩气的开发具有重要指导意义。

BDD电催化耦合电解析处理载人航天器中冷凝废水的研究

为解决在硼掺杂的金刚石电极(BDD)电催化处理冷凝废水中,由于冷凝废水电导率低而导致处理能耗较高的问题,提出了BDD电催化耦合电解析的新方法处理冷凝废水。在BDD反应器内填充吸附有无机盐的混合阴阳离子交换树脂,电催化处理冷凝废水时吸附在树脂上的离子在电场作用下解析下来进入废水中,并进行交替的吸附、解析及定向运动,从而改善废水的导电性,电极两端电压显著降低,停止加电后,离子又能重新交换吸附在树脂上。以Na_(2)SO_(4),Na_(3)PO_(4)以及NaNO_(3)作为电解质时,对总有机碳(TOC)去除没有影响;而以NaCl作为电解质时,TOC去除率随着NaCl添加量的增加而降低。

变质程度对煤中瓦斯扩散规律的影响

为研究瓦斯的吸附解吸特性及扩散规律对煤层气产量和开采难易程度的影响,通过高压瓦斯吸附解吸试验,探讨了变质程度影响下煤样中瓦斯的扩散规律。结果表明:随煤样变质程度增大,大分子结构增多使吸附空间增大的同时也加快了吸附进程,导致吸附能力增强,同时煤中对吸附解吸起抑制作用的小分子物质变少,导致能产生解吸的气体量变大,解吸能力变强;相对于较高变质程度的煤,低变质程度煤中的惰质组和壳质组能提供较多的大孔隙,从而使扩散空间增大,此外,低变质程度煤的惰质组中开放型孔隙含量较高,能加快扩散速率,使瓦斯扩散能力随变质程度的增大而减弱。

煤中超临界CO_(2)解吸滞后机理及其对地质封存启示

将CO_(2)注入不可采煤层地质封存既是降低温室气体效应最理想选择之一,也是煤炭工业降低CO_(2)排放、实现低碳化可持续发展的必由之路,然而,煤层CO_(2)地质封存悬而未决的关键问题是:“注入煤层中的CO_(2)到底能否长期停留而安全封存?”。鉴于此,在弄清煤体CO_(2)解吸滞后规律的基础上,揭示超临界CO_(2)解吸滞后机理,建立煤层CO_(2)地质封存量化模型,探讨利用解吸滞后实现煤层CO_(2)长期安全封存。研究表明:煤中超临界态CO_(2)解吸滞后程度大于亚临界态CO_(2),在超临界阶段,吸附与解吸等温线形成近似“平行线”的稳定滞后特征;解吸滞后的本质原因是煤中微纳米级亲水性孔隙形成弯液面、产生强大毛细压力、渗吸液态水、截断并固定超临界CO_(2)流体、最终形成了CO_(2)残余封存,例如,煤中直径40~10 nm圆柱形无机孔隙可产生7.30~29.12 MPa毛细压力,足以封堵超临界态CO_(2);以九里山煤样解吸等温线数据为例,采用基于煤层CO_(2)解吸滞后的地质封存量化模型,评估出900~1500 m深部二1煤层封存总量稳定在35~37 m^(3)/t,其中,吸附封存约占80%,残余封存约占15%,而结构封存仅占5%;解吸滞后启示应尽可能采取措施提高煤层残余封存CO_(2)比例,原因是毛细堵塞的残余封存CO_(2)较围岩密封的游离和吸附CO_(2)更安全且没有泄露风险,煤层灰分、水分、孔隙尺寸和形貌等物性参数是影响残余封存效率的主要因素。

Mn_(3)O_(4)/CTS的制备及对含钼废水的解吸研究

因工业废水污染严重,该文研究制备了一种有效除钼吸附剂,探究对含钼废水的去除效果并找到最佳条件组合及最佳解吸方案。采用一步水解氧化法和交联法分别制备Mn_(3)O_(4)纳米粒子和Mn_(3)O_(4)/壳聚糖(Mn_(3)O_(4)/CTS)复合纳米粒子,使用正交法确定Mn_(3)O_(4)/CTS除钼的最佳组合,并将单因素控制变量法应用于解吸试验,分析不同解吸条件下的解吸性能。结果表明,无水乙醇12 mL、NaOH 110 mL、温度40℃、反应1.5 h为最佳制备Mn_(3)O_(4)粒子条件,除钼率达70%以上;Mn_(3)O_(4)/CTS粒子在壳聚糖与Mn_(3)O_(4)质量比为3∶1、乙酸30 mL、戊二醛2 mL、150 r/min转速下制备的除钼效果最佳,去除率为90.62%;影响除钼程度顺序为初始pH>吸附剂量>振荡速度>温度;确定最佳解吸液为0.05 mol/L的NaOH,解吸时间30 min,解吸温度40℃,在5次解吸后仍能满足除钼率超80%。制备的Mn_(3)O_(4)/CTS复合纳米粒子除钼效果好,具有优良且稳定的再生效果。

分形界面吸附行为初探

煤层气吸附解吸机理研究是揭示煤层气成藏机理及高效开发煤层气的基础。已有研究表明,煤储层孔隙结构非常复杂且具有分形特征,煤层气在孔-固界面的吸附行为明显受到煤孔隙结构特征的影响。对比分析几种常用气-固界面上的吸附模型,总结这些模型的特点和适用条件,指出当前吸附模型在分形界面吸附行为的描述和应用上均未摆脱吸附选择性的平稳假设,尚未考虑吸附厚度的尺度不变特征。而分形拓扑理论可以有效标定分形对象的尺度不变属性,为分形界面的等效表征提供了理论支撑。因此,结合上述模型对气-固界面吸附行为的描述,借助分形拓扑理论提出煤储层孔-固界面上分形吸附行为的相关假设及其控制机理,构建基于吸附拓扑的单层吸附模型。在此基础上,通过设置不同的吸附拓扑参数组合获取其等温吸附曲线,分析得出,随着吸附压力的升高,吸附覆盖率表现出指数、线性和对数3种不同的增长趋势,而吸附热表现为对数减小趋势。结果显示,不同的吸附拓扑参数组合会得到不同类型的等温吸附曲线,在一定程度上弥补了Langmuir方程只能描述单一类型等温吸附线的不足。为了验证吸附模型的适用性,结合沁水盆地武乡区块富有机质泥页岩的液氮吸附实验数据,对比了实际等温吸附曲线与模拟吸附曲线的差异。结果表明,通过调整各吸附拓扑参数之间的组合关系,可以使等温吸附模拟曲线与实际吸附曲线的趋势始终保持一致。最后,探讨了吸附解吸机理的研究方向,类比电子层提出了吸附层的概念,指出发展分形动力学描述模型是解释煤层气吸附解吸规律的关键。

新疆难解吸煤可溶有机质对瓦斯吸附解吸特征的影响研究

新疆焦煤公司煤层瓦斯难解吸,导致抽采难度增大。而煤中可溶有机质对瓦斯的吸附解吸有重要影响。为了研究其影响,使用四氢呋喃对煤中的可溶有机质进行抽提,采用低温氮吸附测试抽提前后煤的孔隙结构,利用煤岩高压瓦斯吸附装置进行抽提前后煤样的吸附解吸实验。研究结果表明:经过四氢呋喃抽提后,发现所有煤样的平均孔径、孔体积和比表面积均有不同程度的增大,认为煤中的可溶有机质被溶解,形成了新的微孔,同时原孔隙被扩大;4^(#)煤、5^(#)煤和6^(#)煤的吸附常数a分别减小了2.73%、16.09%、14.57%,4^(#)煤和5^(#)煤吸附常数b分别增大了12.18%、2.58%,6^(#)煤的吸附常数b减小了8.59%,煤的吸附能力降低,解吸速度增大,可溶有机质促进了煤对瓦斯的吸附。

PSA解吸气及液氮洗尾气替代天然气使用探索

介绍了PSA解吸气及液氮洗尾气替代天然气使用运行情况。通过对中国石化集团南京化学工业有限公司30万t/a合成氨装置和9万t/a制氢装置燃料气用户的流程及设备进行改造,实现了利用尾气进行气化炉烘炉和作为火炬的正常用燃料气,采用PSA解吸气和液氮洗尾气替代天然气,减少了天然气的耗量,节约了生产成本。

磁性氮化碳复合材料的制备及其对磷酸化肽的富集

蛋白质的磷酸化在细胞信号传导和疾病发生发展中起着重要作用,但磷酸化的动态变化和低丰度的特点使得对其直接分析有着较大的困难。为了解决磷酸化肽难离子化、检测丰度低的瓶颈问题,本研究制备了一种磁性氮化碳复合材料,结合基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS),建立了一种对复杂样品中低丰度磷酸化肽富集与分析的方法。采用电子显微镜、红外光谱分析及X射线衍射分析等手段对合成的磁性氮化碳材料进行表征。以酪蛋白酶解产物为实验模型,发现磁性氮化碳材料能够实现对磷酸化肽的高选择性富集和高灵敏度检测,检出限为0.1 fmol。选择脱脂牛奶、人唾液和人血清为实际分析样品,发现磁性氮化碳材料对微量蛋白生物样品中磷酸化肽的分析具有较高的应用潜力。