Amount Of Adsorbed CO Research Articles

A novel (CaO/CeO2)@CeO2 composite adsorbent based on microinjection titration-calcination strategy for CO2 adsorption

A simultaneous titration-calcination strategy was proposed to synthesize core–shell type (CaCO3/Ce(OH)CO3)@Ce(OH)CO3 precursors by titrating Ca2+ and Ce3+ into aqueous CO2 storage material (CO2SM) solution simultaneously without adding any templating agents or surfactants. After calcination at 900 °C, the novel core–shell type (CaO/CeO2)@CeO2 composite adsorbent with the strong stability of adsorption cycle was synthesized. The effects of Ca/Ce doping ratio, CO2SM dosage, drop rate and temperature conditions on the CO2 adsorption performance on the composite adsorbent during the calcium cycle were investigated. The synthetic adsorbent with a Ca/Ce doping ratio of 24: 1 had the strongest CO2 capture performance during the calcium cycle, and it mainly consisted of CaO and CeO2. The CO2 adsorption amount still maintained at about 430 mg/g after 15 cycles under the adsorption–desorption conditions at 750 °C and 900 °C. (CaO/CeO2)@CeO2 composite adsorbent is a core–shell structure with CeO2 as the shell and CaO/CeO2 as the liner, in which CeO2 is uniformly dispersed in CaO pore channels, which gives the adsorbent a stable pore structure and enhances the anti-sintering performance of Ca-based adsorbent. Due to the special property of CeO2, it can also promote the ion migration during the carbonation process, thus maintaining the adsorption activity. Density functional theory (DFT) calculations successfully explain why CeO2 can be used as an inert dopant to promote the adsorption of CO2. After that, the synthesis mechanism of core–shell adsorbent and the reaction mechanism of CO2 adsorption are proposed in conjunction with the series characterization. This work provides a new strategy for the efficient synthesis of Ca-based adsorbents with special morphology and a new idea for CO2 capture.

Synthesis and CO2 adsorption kinetics of Aluminum Fumarate MOFs pellet with high recovery

As a promising CO2 adsorbent, Aluminum Fumarate (AlFu) metal organic frameworks (MOFs) were explored for pelletizing technology and CO2 adsorption characteristics. The effects of binder type (sodium carboxymethylcellulose (CMC), aluminum sol (AS)) and content (2.5 wt%-20 wt%), CO2 partial pressure (0.3 bar–1 bar) and temperature (35 °C–65 °C) on the mechanical performance and adsorption process were investigated. The results revealed that with the increase of binder mass, the pellet mechanical strength rose while the CO2 adsorption amount decreased. The AlFu pellet with 2.5 wt% CMC could retain the powder porosity and adsorption capacity. The mechanical strength of AlFu@CMC-2.5 wt% achieved 1.486 MPa, and the maximum adsorption capacity was 1.26 mmol/g at 35 °C and 1.0 bar. The CO2 adsorption capacity was increased with lower adsorption temperature and higher CO2 partial pressure. Compared with pseudo second order model and pseudo first order kinetic model, Avrami kinetic model could better describe the CO2 adsorption behavior of AlFu pellet. It indicated that the adsorption process was not a single physical or chemical adsorption. The rate-limiting kinetic analysis showed that the CO2 adsorption rate was determined by film diffusion and intraparticle diffusion rather than inter-particle diffusion.

Modification of silica supported nickel catalysts with lanthanum for stability improvement in methane reforming with CO2

Dry reforming of methane (DRM) with excessive methane composition at CH4/CO2 = 1.2:1 was studied over lanthanum modified silica supported nickel catalysts (Ni-xLa-SiO2, x: 1, 2, 4, and 6% in the target weight percent of La). The catalysts were prepared by ammonia evaporation method. Nickel phyllosilicate and La2O3 were the main phases in calcined catalysts. The modification of La enhanced the formation of 1:1 and Tran-2:1 nickel-phyllosilicate. There existed an optimum content of La loading at 1.50 wt% in Ni–2La–SiO2 which resulted in its highest reduction degree (95.3%). The catalysts with appropriate amounts of La exhibited higher amount of CO2 adsorption and created more medium and strong base centers. The sufficient number of exposed metallic nickel sites to catalyze the reforming reaction, as well as enough medium and strong basic sites in Ni–La–SiO2 interface to accomplish the carbon removal were two important factors to attenuate catalyst deactivation. The catalyst stability evaluated at 750 °C for 10 h followed the order: Ni–2La–SiO2 > Ni–4La–SiO2 > Ni–1La–SiO2 ≈ Ni–6La–SiO2 > Ni–SiO2. Ni–2La–SiO2 catalyst possessed the lowest deactivation behavior, whose CH4 conversion dropped from 60.2 to 55.9% after 30 h operation at 750 °C, indicating its high resistance against carbon deposition and sintering.

The comparison of adsorption characteristics of CO2/H2O and N2/H2O on activated carbon, activated alumina, zeolite 3A and 13X

• The adsorption of CO 2 /H 2 O and N 2 /H 2 O is compared by dynamic experiments. • Effects of flow rate, temperature and steam mole fraction are analyzed. • Activated carbon and activated alumina, zeolite 3A and 13X are compared. • CO 2 /H 2 O adsorption selectivity ranked as: 3A> 13X> alumina> activated carbon. • The thermal wave peak of N 2 /H 2 O is decayed and delayed comparing to CO 2 /H 2 O. The breakthrough curves and adsorption amounts of N 2 /H 2 O and CO 2 /H 2 O on activated carbon, activated alumina, zeolite 3A and zeolite 13X were studied experimentally. The experiments were conducted to investigate the effects of inlet steam mole fraction, flow rate and temperature. The effect of steam mole fraction on the thermal effect of adsorption was also studied. The results show that the breakthrough time and adsorption saturation time of adsorbates are decreased with increasing flow rate and temperature. When steam mole fraction increases, the breakthrough time and adsorption saturation time of adsorbates on zeolite 3A and 13X are decreased, while these of other adsorbents are increased. As steam mole fraction increases from 1% to 2%, the adsorption amount of CO 2 decreases by 2.2–45.4% and that of N 2 decreases by 12.2–19.1%. Zeolite 3A shows a good adsorption selectivity for CO 2 /H 2 O and N 2 /H 2 O. The thermal wave peak time of N 2 /H 2 O is 0.71–8.31 min longer than that of CO 2 /H 2 O, while the peak temperature of N 2 /H 2 O is 2–16 °C smaller than that of CO 2 /H 2 O. As steam mole fraction increases from 1% to 2%, the peak temperature of CO 2 /H 2 O increases by 1.63–11.55 °C and N 2 /H 2 O increases by 2.17–18.17 °C. The thermal wave peak of N 2 /H 2 O and CO 2 /H 2 O on activated carbon adsorption bed is the smallest among these four adsorbents.

Experimental Study on Renewable Porous Carbon Dioxide Adsorbent Materials for Space Shuttles

Porous adsorbent material is promising to be used to regeneratively remove CO2 from space shuttles. In this work, the amount and isosteric heat of CO2 adsorption in solid amine are experimentally studied at pressures ranging from 0 to 6 bar and temperatures ranging from 20 °C to 60 °C. The amount and isosteric heat of water adsorption in the solid amine is tested at different humidities (relative humidity 30–80%). The effective thermal conductivity of the solid amine at different atmospheres (air, N2, CO2 and water), pressures and temperatures is also investigated. The results show that the best temperature for CO2 adsorption in the solid amine is 45 °C under dry conditions. The amount of water adsorption increases with enhanced humidity, while the isosteric heat of water adsorption remains a constant value. The effective thermal conductivity of the solid amine increases with an increase in pressure. The adsorbed phase (CO2 and water) in the solid amine makes a contribution to improving the effective thermal conductivity of solid amine particles. The above findings can help design a better adsorption system in space.

Preparation and evaluation of fine-tuned micropore biochar by lignin impregnation for CO2 and VOCs adsorption

The pore structure of adsorbent plays a critical role during the CO2 and volatile organic compounds (VOCs) adsorption. To improve the adsorption performance, fine-tuned micropore biochar was prepared by impregnation using sodium lignosulfonate as precursor. And the impregnated biochar was characterized and used as adsorbent to adsorb CO2 and VOCs (benzene and acetone). The results showed that the specific surface area (SSA) and micropore volume (Vmicropore) of impregnated biochar increased 3.27 and 5.02 times, which enhanced the CO2 adsorption amount obviously (77.02–102.88 mg/g). The pore structure of biochar was critical to CO2 capture, and high SSA, large Vmicropore and narrow aperture were benefits for the adsorption. Both Avrami fractional model and Freundlich model fitted the adsorption better, indicating the CO2 adsorption on impregnated biochar was multilayer adsorption and determined by both physical and chemical mechanisms. The adsorption was overwhelming exothermic process, thus increasing the temperature from 0 ℃ to 65 ℃ would decrease the adsorption amount by 74.22%-79.40%. High reusability (93.98%-98.21%) after 10 times adsorption-desorption cycles acknowledged the biochar was promising CO2 adsorbents. In addition, the impregnated biochar exhibited excellent VOCs adsorption performance, with the adsorption amount being 31.35–61.14 mg/g and 44.67–80.99 mg/g for benzene and acetone, respectively. All the results showed lignin impregnated biochar is a promising adsorbent for CO2 capture and pollution adsorption.

Facile fabrication of mesoporosity silica as support for solid amine CO2 adsorbents with enhanced adsorption capacity and kinetics

Solid amine adsorbents show the excellent capture performance in flue gas CO2 separation. The pore structure of adsorbent plays a crucial role in improving adsorption performance. Herein, hierarchical mesoporous silica (HMS) support with large pore volume was prepared via one template without resorting to either additives or multi-templates. The pore structure of HMS support for polyethyleneimine (PEI) resulted in larger CO2 adsorption capacity and faster adsorption kinetics when compared to the SBA-15 support with the same amount of PEI loading. At the optimal PEI loading of 70 wt% on HMS, CO2 adsorption amount is 4.21 mmol/g at 75 °C with 15 vol% CO2. Simultaneously, HMS-PEI70% adsorbent is proved to be good stability during 20 adsorption cyclic. These results demonstrate that supports with hierarchical mesoporosity provide significant advantages for CO2 capture. Finally, considering the practical application of adsorbent, the influence of capture temperature and impurity gas on capture performance has been further investigated. CO2 adsorption capacity was enhanced with the presence of water, while the SO2 has the negative effect on the capture performance due to the competitive adsorption of sulfur dioxide. This work can provide a promising composite adsorbent to realize the efficient CO2 separation from the flue gas in the future.

Fabrication of azobenzene-functionalized porous polymers for selective CO2 capture

Many solid adsorbents have been prepared for the CO2 capture. In particular, the photoresponsive adsorbents have attracted extensive interests because of their tunable pore structure and variable responsive behaviors provoked by the external light. However, it is challenging to fabricate the photoresponsive adsorbents featured the big CO2 capacity and high CO2 selectivity. Herein, copolymerized between 4-phenylazobenzoyl chloride, 2,4,6-trichloro-1,3,5-triazine and melamine, a series of azobenzene-functionalized porous polymers (PTM-AZOs) are successfully synthesized. The PTM-AZOs are verified in possession of proper pore structures, large surface area and photoconductive properties through a series of characterization. The PTM-AZO-2 with the trans-isomerization exhibits the best CO2 adsorption amount of 2.7 mmol·g−1 (273 K and 0.1 MPa), while the CO2/N2 selectivity can reach 2459 and 607 on the trans- and cis-isomerization, respectively. The regulatable pore structures controlled by the photoresponsive azobenzene groups affect the CO2 capture performance of the PTM-AZOs.

Effect of pore structure on competitive sorption and diffusion of mixed methane and carbon dioxide in anthracite, South Qinshui Basin, China

A deep understanding of the competitive adsorption and diffusion of methane (CH4) and carbon dioxide (CO2) in coal is significant for implementing the CO2-ECBM project. For three high-rank coal samples, industrial analysis, coal maceral, and vitrinite reflectance (RO) determination, mercury injection test, and low-temperature nitrogen/carbon dioxide specific surface test were carried out, and the composition and pore structure of coal samples were studied systematically. Meanwhile, through the three mixed gases (75%CH4 + 25%CO2, 50%CH4 + 50%CO2, 25%CH4 + 75%CO2) adsorption and desorption test, the absolute adsorption amount, free phase and adsorption phase of CH4 and CO2 under different equilibrium pressures, and the equivalent diffusion coefficients of gas migration in the process of adsorption/desorption equilibrium were calculated. Finally, the relationship among the coal composition, pore structure, and the competitive adsorption and diffusion characteristics of methane and carbon dioxide mixture in coal were studied. The results show that: (1) the composition of coal has an important influence on the development of coal pore structure and the adsorption and transport of gas in coal. Supermicropore (<2 nm in size) is the prominent adsorption place. Furthermore, its development, which essentially determines the adsorption capacity of coal samples, is positively correlated with fixed carbon content, vitrinite content, and vitrinite reflectance. (2) When the pores >100 nm in size relatively developed, the coal samples have higher porosity, lower micropore diffusion, and a smaller desorption hysteresis index. Because the pore's connectivity is limit, its content has no apparent correlation with the permeability of coal samples and most of the adsorption and diffusion parameters. (3) The desorption hysteresis is mainly caused by the opposite migration direction of gas in the process of adsorption and desorption and the resulting dislocation of coal matrix swelling and shrinkage. The competitive adsorption of CH4 or CO2 and their separation index (SCO2/CH4) in coal samples decreases with the increase of adsorption equilibrium pressure. Also, the desorption process often shows a higher SCO2/CH4 value than that of the adsorption process. (4) During the adsorption process, the equivalent macro-diffusivities of the coal sample decrease as a power function with increasing pressure and increase with the carbon dioxide content increasing in the mixed gas. However, the equivalent micro-diffusivities change little with the different CH4 and CO2 mixtures migration in different coal samples. The equivalent diffusion coefficient of coal is positively correlated with macropore, mesopore, transitional and micropore content in coal samples.

Mechanical Force Induced Formation of Extrinsic Micropores in Coordination Polymers.

Mechanical force can be employed not only to efficiently synthesize new materials under environmentally friendly conditions but also to change the macroscopic and microscopic properties of materials. Although coordination polymers (CPs) are attractive functional materials because they possess high structural designability and diversity, mechanical force-induced structural and functional changes of CPs are challenging issues. In this study, two one-dimensional CPs, one a densely packed nonporous CP [Cu2(bza)4(pyr)] (1) and the other a porous CP [Cu2(1-nap)4(pyr)] (2) (bza = benzoate, 1-nap = 1-naphthoate and pyr = pyrimidine), were subjected to ball-milling to assess the effect of mechanical force on their porosities. Ball mill treatments were found to induce an amorphization and cause a 30 fold enhancement of the CO2 adsorption amount at 195 K and P/P0 ∼ 1 for 1 and a slightly decreased CO2 adsorption amount for 2. The results of thorough characterization studies suggest that the formation of extrinsic micropores in addition to extrinsic mesopores/macropores between particles takes place by ball milling.

Mixed polyamines promotes CO2 adsorption from air

The deployment of large-scale direct air capture (DAC) technology relies on the development of energy-efficient and cost-effective CO2 capture materials. The high desorption temperature of the current DAC adsorbents, especially the supported polyamines, is undesirable. In this work, the "mixed-polyamines" concept was adopted to prepare class 1 adsorbents by impregnating both tetraethylenepentamine (TEPA) and diethanolamine (DEA) into the mesoporous SBA-15. The synergy of TEPA and DEA influences the reaction mechanism between CO2 and amines sites, resulting in higher amine efficiency and lower regeneration temperature. Moreover, CO2 adsorption and desorption kinetics are enhanced by the introduction of hydroxyl groups from DEA. The desorption process of solid polyamines-loaded adsorbents fits well with the Avrami model under ultra-dilute CO2 concentrations. SBA-15 loaded mixed polyamine with a weight ratio of TEPA to DEA equaling to 4 shows a maximum CO2 adsorption amount of 1.93 mmol/g at 400 ppm CO2 and 25 °C, a fast adsorption rate of 1.82 mmol/(g·h), and a desorption rate of 0.26 mmol/(g·min) at 80 °C within the first 5 min, which is believed to be a promising DAC adsorbent for practical application.

Enhanced CO2 adsorption performance on amino-defective UiO-66 with 4-amino benzoic acid as the defective linker

UiO-66(Zr), one of the Zr-based metal–organic frameworks (MOFs), is a potential adsorbent for gas separation owing to its large surface area, easily tunable pore structure, and high chemical/thermal stability. Nevertheless, its CO2 adsorption amount is somewhat modest in comparison to that of various MOFs. In this study, 4-aminobenzoic acid (PABA) as amino-defective linker was mixed to terephthalic acid at various compositions in a one-step synthesis of UiO-66(Zr) framework. This new restructuring strategy produced defective UiO-66(Zr) with enhanced porosity owing to the missing-linker defects, simultaneously formed –NH2 groups in the framework, leading to the improvement of the CO2 capture capacity. At 298 K and 100 kPa, the defective UiO-66 modified with 10% PABA exhibited the highest CO2 uptake capacity of ~ 2.47 mmol g−1 and ideal adsorbed solution theory (IAST)-based CO2/N2 selectivity of ~ 46, which surpass many other CO2 benchmark adsorbents. This opens a new perspective for developing defective UiO-66(Zr) adsorbent contained amine functional groups, which can improve CO2 separation performance.

Preparation of Nitrogen-Doped Cellulose-Based Porous Carbon and Its Carbon Dioxide Adsorption Properties.

Nitrogen-doped cellulose-based porous carbon materials were obtained by hydrothermal method and KOH chemical activation together with melamine as a nitrogen-doping precursor. The effects of hydrothermal temperature on the microstructure and surface morphology of the products were mainly studied. Also, the carbon dioxide adsorption capacity of the prepared porous carbon was investigated. It was found that when the hydrothermal carbonization temperature was 270 °C and the mass ratio of cellulose and melamine was 1:1, the largest micropore specific surface area of 1703 m2·g–1 and micropore volume of 0.65 cm3·g–1 were obtained, with a nitrogen-doping composition of 1.68 atom %. At the temperature of 25 °C and under the pressure of 0.1, 0.2, 0.3, and 0.4 MPa, the adsorption amount of CO2 was 1.56, 3.79, 5.42, and 7.34 mmol·g–1, respectively. Also, the adsorption process of CO2 was in good accordance with the Freundlich isotherm model.

Amine‐impregnated silica zeolite from microalgae ash at different calcination temperatures for CO 2 capture

Microalgae is an excellent type of biomass for bio-energy production due to its high calorific value and fast growth. However, a large amount of ash would be generated during microalgae utilization. In this work, MCM41 was prepared from microalgae ash. The materials were calcined at different temperatures (450°C, 500°C, 550°C, and 600°C), and the effect of calcination temperature was investigated. Polyethyleneimine (PEI) was loaded in MCM41 by the impregnation method at different loading amounts (30%, 40%, 50%, and 60%). The CO2 capturing capacity was measured. The results showed that the MCM41 calcined at 450°C was the optimal material, which performed the most developed pore structure. Amine loading enhanced the CO2 capturing capacity of MCM41. The CO2 capturing capacity increased as PEI loading amount increased. The highest CO2 adsorption amount was 2.275 mmol/g with 60% amine loading at 25°C and 1 bar. Adsorption temperature had a mild impact on CO2 capture, and its CO2 adsorption amount decreased slightly with an increase in the adsorption temperature. It was considered that the CO2 uptake of amine-impregnated MCM41 kept stable at different temperatures below 100°C. Also, it showed good cyclic stability. After 10 cycles, the CO2 capturing capacity of 1.6 mmol/g was exhibited.

CO2 hydrogenation to light olefins over mixed Fe-Co-K-Al oxides catalysts prepared via precipitation and reduction methods

A series of Fe-Co-K-Al oxides catalysts were prepared by precipitation-reduction method using NH4OH as precipitating agent and NaBH4 as reducing agent. The effect of preparation methods including one-pot preparation (C1), without the addition of NH4OH (C2), precipitation followed by reduction (C3) and doubling NaBH4 content of C3 (C4) on the physicochemical properties of the catalysts as well as their catalytic CO2 hydrogenation to light olefins was investigated. The preparation methods had a significant influence on phase, reducibility and the amount and strength of CO2 and H2 adsorption with the catalysts surface. The structure–activity relationships indicated that the CO2 conversion was proportional to the amount of medium CO2 adsorption sites, while the O/P ratio increased with decreasing the amount of weak H2 adsorption sites. The C3 catalyst exhibited the highest light olefins yield of 16.58% at 350 °C and 20 bar. This was attributed to a significant reduction of weak adsorption of H2, while maintaining a high level of medium CO2 adsorption, inhibiting the hydrogenation of olefins to paraffins products and providing the relatively high CO2 conversion, respectively. Replacing the reducing gas from H2 to a gas mixture containing H2 and CO2 of the C3 catalyst (C5) was unable to reduce the iron species to metallic Fe, resulting in the formation of Fe3C which was less active for the production of hydrocarbon compared to Fe5C2 phase formed in the C3 catalyst.

Simultaneous impregnation of Ni and an additive via one-step melt-infiltration: Effect of alkaline-earth metal (Ca, Mg, Sr, and Ba) addition on Ni/γ-Al2O3 for CO2 methanation

As part of carbon energy recycling, the CO2 methanation process in the power to gas technology, which converts the electricity grid into a gas grid [CO2 + 4H2 (produced by surplus electricity) → CH4] using a catalytic process, has been developed in the countries such as Germany and Denmark. To achieve an efficient catalytic process, the design of low-cost and high-efficiency catalysts is required. In this study, highly loaded Ni/Al2O3 catalysts (30 wt%) were prepared using the alkaline-earth metals (Mg, Ca, Sr, and Ba) via one-step melt-infiltration (OSMI) method. The Ni active sites were investigated, and the effectiveness of each alkaline-earth metal (Ca, Mg, Sr, and Ba) was determined. The catalytic activity was investigated in the temperature range of 275–400 °C and weight gas hourly velocity (WHSV) of 160,000 mL·gcat−1·h−1 under atmospheric pressure. Ni and alkaline-earth metals were uniformly dispersed into the pore structure of the alumina support. The average metallic Ni particle size of each catalyst was similar (~11 nm), and no severe Ni sintering was observed even at a Ni loading of 30 wt%. Mg-promoted Ni/Al2O3 catalyst was unsuitable for the OSMI method because the reduction of the Ni active sites was not completely accomplished at 400 °C. Ca-promoted Ni/Al2O3 catalyst afforded the best catalytic activity among other metal-promoted Ni/Al2O3 catalysts. Ca increased the CO2 adsorption amount and reducibility of the Ni active sites, and the optimum Ca loading was 5 wt%. However, the over-loading of Ca (10 wt%) was harmful to the catalytic activity of the Ni active sites.

An electrostatic repulsion strategy construct ZIFs based liquids with permanent porosity for efficient CO2 capture

Porous liquids (PLs), as a novel liquid sorbent with permanent porosity, still present challenges such as high viscosity and melting temperatures. Herein, an efficient electrostatic repulsion strategy is proposed to engineer zeolitic imidazolate frameworks (ZIFs) type III PLs employing ZIF-8-g-BPEI nanoparticle stability dispersed into BPEI. The viscosity and melting temperatures of ZIF-8-g-BPEI PLs could be tailored via control particle size, grafting polymer, and concentration of porous nanoparticles. The existence of BPEI on the surface of ZIF-8-g-BPEI facilitates the stable dispersion of ZIFs nanoparticles in BPEI via the electrostatic repulsion as well as enhances CO2 adsorption capacity of PLs. Moreover, the CO2 adsorption amount of ZIF-8-g-BPEI-30 PLs is 6.5 times high than that of neat BPEI, suggesting the permanent free volume of ZIFs is retained in their corresponding PLs. Benefiting from the branched structure of BPEI grafted onto the outer surface of ZIFs , ZIF-8-g-BPEI-10 PLs remain liquified down to -71.1 °C, together with viscosity as 1.7 Pa·s−1 at 25 °C. Therefore, the electrostatic repulsion strategy opens an effective avenue to prepare novel liquid materials and shows numerous potential applications in gas adsorption and separation.

“Environmental phosphorylation” boosting photocatalytic CO2 reduction over polymeric carbon nitride grown on carbon paper at air-liquid-solid joint interfaces

The limited CO2 content in aqueous solution and low adsorption amount of CO2 on catalyst surface lead to poor photocatalytic CO2 reduction activity and selectivity. Herein, the design and fabrication of a novel photocatalytic architecture is reported, accomplished via chemical vapor deposition of polymeric carbon nitride on carbon paper. The as-obtained samples with a hydrophobic surface exhibit excellent CO2 transport and adsorption ability, as well as the building of triphase air-liquid-solid (CO2-H2O-catalyst) joint interfaces, eventually resulting in the inhibition of H2 evolution and great promotion of CO2 reduction with a selectivity of 78.6%. The addition of phosphate to reaction environment makes further improvement of CO2 photoreduction into carbon fuels with a selectivity of 93.8% and an apparent quantum yield of 0.4%. This work provides new insight for constructing efficient photocatalytic architecture of CO2 photoreduction in aqueous solution and demonstrates that phosphate could play a key role in this process.

Multi-objective genetic algorithm optimization with an artificial neural network for CO2/CH4 adsorption prediction in metal–organic framework

The industry requirement of separating gas mixtures via adsorption techniques is rapidly being imposed, as the adsorption method is regarded as superior in terms of thermodynamic efficiency and cost. Gas mixture adsorption investigations with metal–organic frameworks (MOFs) have been conducted both in experimental and molecular simulations. Molecular simulation studies are faster in predicting CO2 adsorption performance but are difficult to conduct because they require detailed information on the characteristics of the MOF. Therefore, in this study, the separation factor of CO2/CH4, the gas adsorption performance, and the heat of adsorption were predicted using artificial neural networks (ANNs). MOF texture properties that contribute to the performance are the input in this simulation. Operating working pressure and temperature are also inputs in this simulation. Optimization is conducted using the multiobjective genetic algorithm method to maximize the separation factor and CO2 uptake with mild heat of adsorption. Moreover, the optimal values will be determined via the technique for order of preference by similarity to the ideal solution (TOPSIS). Interestingly, the amount of CO2 adsorption, selectivity, and heat of adsorption are in satisfactory agreement with the values that are predicted by ANN with high validity regressing (R = 0.99). The output optimum point to get maximum capacity of CO2 and selectivity with mild heat of adsorption are 9.97 mmol/g, 362.92 kJ/kg, and 11.01 respectively. These results provide a basis for the use of machine learning algorithms in conjunction with multiobjective optimizations to investigate the output performance of gas adsorption under the requirements of industrial applications.

Effect of carbonization temperature on CO2 adsorption behavior of activated coal char

Nowadays, the increase of CO2 concentration caused by the utilization of traditional fossil fuels has a negative impact on the environment and human health. Therefore, there is an urgent need to explore effective measures to control CO2 emission. In this work, activated coal char for CO2 capture was prepared with different carbonization temperatures by two-step method with KOH as the activator. The effects of carbonization temperature and adsorption temperature on the CO2 adsorption performance of activated coal char were investigated. Elemental analysis, BET, XPS and SEM analysis of the activated coal char were performed. The results showed that the microporous structure has an important influence on the adsorption performance of activated coal char. With the increase of carbonization temperature, the microporous volume increases first following by a decrease and the amount of CO2 adsorption also shares the same trend. For the adsorption temperature, as the adsorption temperature rises, the CO2 adsorption capacity of activated coal char decreases. The maximum CO2 adsorption capacity of 4.8 mmol/g was achieved at optimal conditions of carbonization temperature 600 °C, adsorption temperature 0 °C and pressure 1 bar. In addition, the activated coal char with a carbonization temperature of 600 °C also shows good selectivity for CO2 over N2, which indicated its prospects in the practical CO2 capture applications.