Views expressed in this editorial are those of the authors and not necessarily the views of the FCSE. The authors declare no competing financial interests.
Metal-organic frameworks (MOFs) have emerged as a class of promising membrane materials. UiO-66 is a prototypical and stable MOF material with a number of analogues. In this article, we review five approaches for fabricating UiO-66 polycrystalline membranes including in situ synthesis, secondary synthesis, biphase synthesis, gas-phase deposition and electrochemical deposition, as well as their applications in gas separation, pervaporation, nanofiltration and ion separation. On this basis, we propose possible methods for scalable synthesis of UiO-66 membranes and their potential separation applications in the future.
In the present work, ball milling was applied for the pretreatment of lignocellulose to obtain high conversion and bio-oil yield in supercritical ethanol. Ball milling substantially decreased the crystallinity and particle size of lignocellulose, thereby improving its accessibility in ethanol solvent. An increased bio-oil yield of 59.2% was obtained for the ball milled camphorwood sawdust at 300°C, compared with 39.6% for the original lignocellulose. Decreased crystallinity significantly benefited the conversion of the cellulose component from 60.8% to 91.7%, and decreased particle size was beneficial for the conversion of all components. The obtained bio-oil had a high phenolic content, as analyzed by gas chromatography-mass spectrometry. Methoxylation and retro-aldol condensation were observed during alcoholysis, and the reaction pathways of lignocellulose in supercritical ethanol were attributed to the action of free radicals.
A series of novel dense mixed conducting ceramic membranes based on K2NiF4-type (La1–xCax)2 (Ni0.75Cu0.25)O4+δ was successfully prepared through a sol-gel route. Their chemical compatibility, oxygen permeability, CO and CO2 tolerance, and long-term CO2 resistance regarding phase composition and crystal structure at different atmospheres were studied. The results show that higher Ca contents in the material lead to the formation of CaCO3. A constant oxygen permeation flux of about 0.63 mL·min−1·cm−2 at 1173 K through a 0.65 mm thick membrane was measured for (La0.9Ca0.1)2 (Ni0.75Cu0.25)O4+δ, using either helium or pure CO2 as sweep gas. Steady oxygen fluxes with no sign of deterioration of this membrane were observed with increasing CO2 concentration. The membrane showed excellent chemical stability towards CO2 for more than 1360 h and phase stability in presence of CO for 4 h at high temperature. In addition, this membrane did not deteriorate in a high-energy CO2 plasma. The present work demonstrates that this (La0.9Ca0.1)2(Ni0.75Cu0.25)O4+δ membrane is a promising chemically robust candidate for oxygen separation applications.
Based on the design of the fluorescent site of a fluorescent probe, we have created a unique system that changes its twisting response to sugar. Two probes were synthesized, in which phenylboronic acid and two kinds of aromatic fluorescent site (pyrene or anthracene) were conjugated by an amide bond. In the fluorescence measurement of pyrene-type probe 1, dimer fluorescence was observed at high pH. In induced circular dichroism (ICD) experiments, a response was observed only in the presence of glucose and γ-cyclodextrin, and no response was seen with fructose. On the other hand, in the fluorescence measurement of anthracene-type probe 2, dimer fluorescence was observed in the presence of both glucose and galactose, and the fluorescence was different from the case of fructose. When the ICD spectra of these inclusion complexes were measured, an inversion of the Cotton effect, which indicates a change in the twisted structure, was observed in galactose and glucose. These differences in response to monosaccharides may originate in the interaction between the fluorescent site and the cyclodextrin cavity.
The desulfurization by seawater and mineral carbonation have been paid more and more attention. In this study, the feasibility of magnesia and seawater for the integrated disposal of SO2 and CO2 in the simulated flue gas was investigated. The process was conducted by adding MgO in seawater to reinforce the absorption of SO2 and facilitate the mineralization of CO2 by calcium ions. The influences of various factors, including digestion time of magnesia, reaction temperature, and salinity were also investigated. The results show that the reaction temperature can effectively improve the carbonation reaction. After combing SO2 removal process with mineral carbonation, Ca2+ removal rate has a certain degree of decrease. The best carbonation condition is to use 1.5 times artificial seawater (the concentrations of reagents are 1.5 times of seawater) at 80°C and without digestion of magnesia. The desulfurization rate is close to 100% under any condition investigated, indicating that the seawater has a sufficient desulfurization capacity with adding magnesia. This work has demonstrated that a combination of the absorption of SO2 with the absorption and mineralization of CO2 is feasible.
The increasing demand of goods, the high competitiveness in the global marketplace as well as the need to minimize the ecological footprint lead multipurpose batch process industries to seek ways to maximize their productivity with a simultaneous reduction of raw materials and utility consumption and efficient use of processing units. Optimal scheduling of their processes can lead facilities towards this direction. Although a great number of mathematical models have been developed for such scheduling, they may still lead to large model sizes and computational time. In this work, we develop two novel mathematical models using the unit-specific event-based modelling approach in which consumption and production tasks related to the same states are allowed to take place at the same event points. The computational results demonstrate that both proposed mathematical models reduce the number of event points required. The proposed unit-specific event-based model is the most efficient since it both requires a smaller number of event points and significantly less computational time in most cases especially for those examples which are computationally expensive from existing models.
Membrane technology holds great potential in gas separation applications, especially carbon dioxide capture from industrial processes. To achieve this potential, the outputs from global research endeavours into membrane technologies must be trialled in industrial processes, which requires membrane-based pilot plants. These pilot plants are critical to the commercialization of membrane technology, be it as gas separation membranes or membrane gas-solvent contactors, as failure at the pilot plant level may delay the development of the technology for decades. Here, the author reports on his experience of operating membrane-based pilot plants for gas separation and contactor configurations as part of three industrial carbon capture initiatives: the Mulgrave project, H3 project and Vales Point project. Specifically, the challenges of developing and operating membrane pilot plants are presented, as well as the key learnings on how to successfully manage membrane pilot plants to achieve desired performance outcomes. The purpose is to assist membrane technologists in the carbon capture field to achieve successful outcomes for their technology innovations.
This paper compares the techno-economic performances of three technologies for CO2 capture from a lignite-based IGCC power plant located in the Czech Republic: (1) Physical absorption with a Rectisol-based process; (2) Polymeric CO2-selective membrane-based capture; (3) Low-temperature capture. The evaluations show that the IGCC plant with CO2 capture leads to costs of electricity between 91 and 120 €·MWh‒1, depending on the capture technology employed, compared to 65 €·MWh‒1 for the power plant without capture. This results in CO2 avoidance costs ranging from 42 to 84 €· tCO2, avoided‒1 , mainly linked to the losses in net power output. From both energy and cost points of view, the low-temperature and Rectisol based CO2 capture processes are the most efficient capture technologies. Furthermore, partial CO2 capture appears as a good mean to ensure early implementation due to the limited increase in CO2 avoidance cost when considering partial capture. To go beyond the two specific CO2-selective membranes considered, a cost/membrane property map for CO2-selective membranes was developed. This map emphasise the need to develop high performance membrane to compete with solvent technology. Finally, the cost of the whole CCS chain was estimated at 54 €·tC O2, avoided‒1 once pipeline transport and storage are taken into consideration.