Assessment of CO2 capture options from various points in steam methane reforming for hydrogen production

Steam methane reforming (SMR) is currently the main hydrogen production process in industry, but it has high emissions of CO₂, at almost 7 kg CO₂/kg H₂ on average, and is responsible for about 3% of global industrial sector CO₂ emissions. Here, the results are reported of an investigation of the effect of steam-to-carbon ratio (S/C) on CO₂ capture criteria from various locations in the process, i.e. synthesis gas stream (location 1), pressure swing adsorber (PSA) tail gas (location 2), and furnace flue gases (location 3). The CO₂ capture criteria considered in this study are CO₂ partial pressure, CO₂ concentration, and CO₂ mass ratio compared to the final exhaust stream, which is furnace flue gases. The CO₂ capture number (N_cc) is proposed as measure of capture favourability, defined as the product of the three above capture criteria. A weighting of unity is used for each criterion. The best S/C ratio, in terms of providing better capture option, is determined. CO₂ removal from synthesis gas after the shift unit is found to be the best location for CO₂ capture due to its high partial pressure of CO₂. However, furnace flue gases, containing almost 50% of the CO₂ in produced in the process, are of great significance environmentally. Consequently, the effects of oxygen enrichment of the furnace feed are investigated, and it is found that this measure improves the CO₂ capture conditions for lower S/C ratios. Consequently, for an S/C ratio of 2.5, CO₂ capture from a flue gas stream is competitive with two other locations provided higher weighting factors are considered for the full presence of CO₂ in the flue gases stream. Considering carbon removal from flue gases, the ratio of hydrogen production rate and N_cc increases with rising reformer temperature.     

Insights into the visible light photocatalytic activity of S-doped hydrated TiO2

Cationic doping of TiO₂ anatase with sulphur represents a facile method to improve catalytic and photocatalytic activity for hydrogen production and extend the action spectrum of TiO₂ into the visible light region. However, there is a lot of misunderstanding when trying to explain the experimental findings and suggest theoretical models. In the present computational research work, novel theoretical models are put forward representing fully hydroxylated small anatase nanoparticles with S(IV) and S(VI) doping in various surface positions and in the bulk. It was found that sulfur in the doped anatase nanoparticles preserves its typical coordination geometries of trigonal pyramid for S(IV) and tetrahedron for S(VI). Doping in the anatase surface is much more energetically favorable compared to doping in the bulk. Doping with S(IV) causes decrease of the band gap from 3.22 to 2.65 eV while S(VI) doping could decrease E_g only to 2.96 eV. Location of photogenerated electrons and holes depends strongly on the position of dopant atoms and their valent state. Contrary to some experimental works, no strong and extended visible light absorption bands could be found with cationic doped hydroxylated anatase nanoparticles. However, improved charges separation is observed indeed and causes improved photocatalytic hydrogen production.     

冷喷涂设备及冷喷涂技术应用研究进展

冷喷涂技术相比于传统热喷涂技术有许多优势,例如喷涂温度低,涂层氧含量低,孔隙率低,在喷涂过程中不易发生氧化、烧损、相变等现象,这使得传统喷涂技术难以制备的氧敏感、热敏感、非晶、纳米材料涂层成为可能。从冷喷涂技术原理出发,介绍了各类冷喷涂设备及冷喷涂涂层的沉积机理,详细阐述了冷喷涂涂层结合机理和结合方式(机械咬合、物理结合、冶金结合、化学结合),介绍了各类冷喷涂装备(高压和低压冷喷涂系统、真空冷喷涂系统、激光辅助冷喷涂系统、静电辅助冷喷涂系统、脉冲气体冷喷涂系统和激波风洞冷喷涂系统)及其研究现状。综述了近几年冷喷涂技术在防腐涂层、耐磨涂层、生物医用、抗菌涂层、电子工业、功能涂层、修复与再制造等领域的研究和应用现状,最后对冷喷涂技术的应用和发展前景进行了展望。     

用组合模型预测聚合物驱产油量

聚合物驱产油量预测结果的可靠性直接关系到油田开发年度规划和中长期规划的部署,因此预测模型的选择尤为重要。在简要介绍组合预测模型的基础上,建立了基于Weibull 预测、HCZ 预测和广义翁氏预测3 种单项预测方法的最优加权法组合预测模型;以预测误差平方和最小为准则确定最优组合预测模型中的加权系数,实现产量预测模型的最优组合,并利用实际生产数据通过与Weibull 预测模型、HCZ 预测模型和广义翁氏模型的预测精度对比分析,验证了组合模型的有效性和实用性。     

MoS2 confined on graphene by triethanolamine for enhancing electrocatalytic hydrogen evolution performance

The reduction of active sites due to reunion and slow electron transfer rates and low electronegativity greatly reduced the catalytic performance of many two-dimensional materials. In this paper, we synthesized composites for partially reducing graphene oxide and molybdenum disulfide (MoS₂@prGO) by one-step hydrothermal method. With the addition of triethanolamine, MoS₂ is highly dispersed on the prGO carrier and converted into the 1T phase MoS₂ (50.4%). Meanwhile, it helps to increase the electron transfer rate of the MoS₂@prGO composites. MoS₂@prGO composites presents a high electron cloud density due to the existence of N atoms and prGO, which promotes the occurrence of hydrogen ion conversion hydrogen reaction and decreases the electrocatalytic hydrogen evolution overpotential. MoS₂@prGO composites exhibits an overpotential of 263 mV at 10 mA/cm² and a small Tafel slope of 60 mV/dec. This work is devoted to offer a new prospect and direction for the improvement of electrochemical HER performance.     

A quantitative study of the morphology of montmorillonite filled thermosets based on a tailor made homogenisation model

Thermoset/montmorillonite nanocomposites were fabricated and their elastic modulus was measured using experimental modal analysis. The morphology of the nanocomposite was considered as a distribution of several components: exfoliated clay platelets, intercalated clay layers, primary particles and clay agglomerates. A novel homogenisation model, which involves a five-phase sequence based on the Halpin–Tsai equations, was developed to calculate the elastic modulus of the nanocomposites. This model was then used to quantify the morphology of the nanocomposites by back calculating the exfoliation, intercalation and agglomeration fractions from the measured values of the elastic modulus. Additionally, this approach led to quantify the efficiency of the fabrication process, which proved to be optimal for 2.5% clay content.     

Chemical analysis of wear tracks on magnetic disks by TOF-SIMS

Surface reactions on magnetic recording disks have been studied during sliding with ceramic sliders in the main chamber of TOF-SIMS. Chemical change of lubricant oil in the wear track was observed by the chemical image of TOF-SIMS. The magnetic disk surface was covered with perfluoroalkyl polyether lubricant (Fomblin Zdol). The Si tip slider surface was covered with Al₂O₃, DLC, TiN or c-BN coating. Experimental conditions were as follows: 0.8 mN of load and a sliding speed of 0.01 m/s. Lubricant oils were decomposed with Al₂O₃ and TiN slider surfaces. Metal (Al, Ti) fluorides were detected by TOF-SIMS in the sliding track. Material transfer occurred by chemical wear of slider material. From TOF-SIMS observation, the decomposition of lubricant molecules was initiated at the end group of molecules (-CF₂CH₂OH). On the other hand, DLC and c-BN sliders suppressed the decomposition reaction of PFPE oils. In conclusion, hard and chemical inert materials such as DLC and c-BN are suitable for a long-life HDI.     

Optimization and analysis of an integrated energy system based on wind power utilization and on-site hydrogen refueling station

An integrated energy system coupled with wind turbines and an on-site hydrogen refueling station is proposed to simulate the future scenario, which can meet the demands of cooling, heating, power and hydrogen. The system was modeled to calculate the capacity and annual operation of each equipment with the total annual cost as the optimization objective. This study evaluates the performance of the system based on the results. When the system is configured with 0–10 wind turbines, the economics, energy consumption and carbon emissions improve as the scale of wind turbines increases. Energy utilization and wind power utilization are above 66.79% and 99.73%, respectively. The on-off coefficient of the power generation unit can affect energy efficiency. When the system contains 5 turbines, 91% of the hydrogen can be self-produced with the minimum amount of energy redundancy.     

Alternate and random (co)polymers composed of anthracene and chloromethylstyrene units through controlled radical ring-opening polymerization: Synthesis,post-functionalization,and optical properties

A cyclic monomer containing the chloromethyl unit 10-methylene-9,10-dihydroanthryl-9-spiro(4′-chloromethylphenyl)cyclopropane (MDCMS) was polymerized using a controlled radical ring-opening polymerization via a reversible addition-fragmentation chain transfer (RAFT) process to afford a nonconjugated alternate polymer composed of anthracene and chloromethylstyrene (CMS) units. Well-defined random copolymers were obtained through the ring-opening RAFT copolymerization. Various functional groups were incorporated into the alternate polymer. The alternate polymer containing imidazole rings exhibited fluorescence quenching as a result of charge transfer. Fluorescence resonance energy transfer (FRET) was observed in the alternate polymers containing naphthalene and thiophene rings. The random copolymers obtained by copolymerization followed by post-functionalizations exhibited characteristic optoelectronic properties that differed from those of the alternate polymers.     

Modeling localized corrosion of pipeline steels in oilfield produced water environments

A model for the estimation of the time evolution of maximum depth of localized corrosion defects caused under oilfield produced water environments has been developed. It takes into consideration the chemical composition of the produced water and other physical parameters. Immersion tests were conducted using coupons of an API 5L X60 pipeline steel under different experimental conditions and periods. The time dependence of the maximum pit depth was modeled as a power function of time, which was successfully fitted to the obtained experimental data using regression analysis. The main result of this analysis was represented by a holistic model which includes the most important variables involved in the pipeline internal corrosion process in produced waters.