The increasing importance of CO
2
in reservoir engineering demands more accurate models for predicting interfacial tension (IFT). We investigated the use of neural networks to predict the IFT of ...ternary systems CO
2
/CH
4
/Water-Brine in a wide range of reservoir conditions, since the existing correlations do not capture all of the system's mechanisms. We introduced an optimization associated with k-fold cross validation to find optimal architecture and ensure an unbiased model. The average absolute relative error obtained is 1.33% (water) and 1.99% (brine) considerably more accurate than the best empirical models tested: 9.87% (water) and 19.11% (brine). Molecular dynamics simulation performed confirms the high superficial activity of CO
2
.
•Two polymeric mesoporous carbon were used as support for iron based catalysts.•Calcination of the iron catalyst did not modify the structure of these supports.•Fe was present in the form of iron ...carbides, α-Fe2O3 and Fe3O4.•C5+ hydrocarbon selectivity increased as oxygen groups were incorporated into the support.•The catalyst has presented satisfactory selectivity towards the production of C5+.
The aim of this work was to produce two iron-based catalysts supported on polymeric mesoporous carbon (PMC) support, analyze them and evaluate their use in Fischer–Tropsch synthesis (FTS). Two PMC supports differing only in synthesis steps were evaluated. The Fe-PMC catalysts were prepared by wet impregnation method and were characterized, before activation, by X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, temperature-programmed reduction (TPR), Mössbauer spectroscopy, Raman spectroscopy and scanning electron microscopy coupled to X-ray energy dispersion spectroscopy (SEM-EDS). Fischer–Tropsch synthesis was carried out to evaluate the activity of the catalysts. The synthesis was carried out in a slurry reactor operating at 513–543K, 20–30atm, and 1:1 CO:H2 molar ratio. X-ray diffraction showed that the calcined iron catalyst did not modify the structure of PMC and that Fe was present in the form of iron carbides, α-Fe2O3 and Fe3O4. The addition of iron in the supports lowered the specific surface area of the support. Fischer–Tropsch synthesis activity and C5+ hydrocarbon selectivity increased as oxygen groups were incorporated into the support. The Fe-PMC catalysts displayed moderate conversion (40%) and high selectivity towards the production of C5+ (72%, w/w).
Two types of zeolites (type X and type A) were synthesized from fly ash of two Brazilian coal based power plants via hydrothermal treatment after ash fusion with NaOH. The synthesized zeolites were ...characterized by means of XRF, XRD, SEM and gas adsorption (N
2
and CO
2
adsorption/desorption at − 196 and 0 °C, respectively). Pure CO
2
and N
2
adsorption equilibrium isotherms were performed at 50, 70 and 90 °C to measure the CO
2
adsorption capacity and selectivity of CO
2
over N
2
. CO
2
/N
2
binary isotherms (15/85% v/v) were also obtained at the same temperatures. Commercial zeolitic materials used for CO
2
/N
2
separation such as zeolite 13X and zeolite 4A underwent the same characterization and adsorption measurements as benchmarks to evaluate the performance of the synthesized zeolites. The synthesized materials from fly ash are promising low cost adsorbents for CO
2
separation, reaching
ca.
83% of the CO
2
adsorption capacity of their commercial counterparts at 0.15 bar and 50 °C.
The use of vessels filled with activated carbon to store and transport natural gas (NG) at moderate pressures (about 3.5
MPa) and ambient temperature (about 298
K) has been studied as a potential ...alternative to compressed natural gas at high pressures (ca. 20
MPa). The present study provides an experimental investigation of charge and discharge cycles of natural gas in a prototype storage vessel filled with activated carbon and analyses the effect of the gas composition on the adsorption capacity. The adsorption properties were evaluated by measuring isotherms for each component of NG in a magnetic suspension balance. The selectivities of the main constituents of natural gas in relation to methane were determined and the influence of the pressure on the selectivity was also observed. Although NG is composed mainly of methane (ca. 90% vol.), our experimental results indicate that the preferential adsorption of the heavier hydrocarbons and CO
2 should be properly taken into account for the evaluation of the behavior of adsorbed natural gas systems along several charge and discharge cycles.
Semi-dry flue gas desulfurization (FGD) technology is used by some coal-based power plants to remove sulfur dioxide from flue gas. In semi-dry FGD systems, SO
2
is removed by calcium-based sorbents ...in a reactive spray dryer, but the level of desulfurization is lower than in wet FGD systems. This work evaluates the effects of seven additives in the desulfurization of the flue gas: magnesium hydroxide, ammonium nitrate, ammonium acetate, ammonium phosphate, sodium hydroxide, citric acid, and urea. Slurries with calcium hydroxide concentrations of 10 and 20 wt% containing 2 and 4 wt% of an additive were applied in the removal of SO
2
. Additives containing ammonium intensified the removal of SO
2
and increased the yield of the reaction. The SO
2
content in the flue gas reduced by 73.8% when applying a slurry containing 4 wt% of ammonium nitrate and 10 wt% of Ca(OH)
2
. The use of this slurry increased the removal of SO
2
by 13.5% when compared to the best result obtained using calcium hydroxide slurry without any additive.
The increasing emissions of carbon dioxide have been pointed out as a major cause for global warming, as a consequence of the intensification of the greenhouse effect in our planet. Therefore, ...technologies of carbon capture and storage (CCS) have been developed with the purpose of reducing the concentration of CO
2
in gas emissions (flue gas). Thus, adsorption-based methods are a very promising cost-efficient technology, particularly in processes such as pressure swing adsorption (PSA). The knowledge of adsorption dynamics in fixed bed is of essential importance for the design of industrial scale units. The objective of the present work is to evaluate the suitability of activated carbons (AC) and metal organic-frameworks (MOF) samples for CO
2
capture by measuring multicomponent breakthrough curves. CO
2
–N
2
systems have been studied for this purpose and a model based on the linear driving force (LDF) approximation for the mass transfer was developed to simulate breakthrough curves under the same experimental conditions. The selectivity of the samples for the adsorption of CO
2
over N
2
was also evaluated and compared. Results suggest that the AC C141 has a great potential for the separation of CO
2
from N
2
at 348 K, since it presents a comparable selectivity (6.2) to the MOF sample Cu-BTC (8.0), and it is much more stable to contaminants present in flue gas scenarios, particularly water vapor. This may be explained by its narrow microporosity as compared to the other activated carbon samples. Despite the high microprosity, sample AC C141 also showed the fastest intraparticle kinetics (
D
c
/r
c
2
≈ 6.0 × 10
−2
s
−1
), which suits it for fast adsorption/desorption cycles as in PSA plants.
The separation of nitrogen and methane from hydrogen-rich mixtures is systematically investigated on a recently developed binder-free zeolite 5A. For this adsorbent, the present work provides a ...series of experimental data on adsorption isotherms and breakthrough curves of nitrogen and methane, as well as their mixtures in hydrogen. Isotherms were measured at temperatures of 283–313 K and pressures of up to 1.0 MPa. Breakthrough curves of CH4, N2, and CH4/N2 in H2 were obtained at temperatures of 300–305 K and pressures ranging from 0.1 to 6.05 MPa with different feed concentrations. An LDF-based model was developed to predict breakthrough curves using measured and calculated data as inputs. The number of parameters and the use of correlations were restricted to focus on the importance of measured values. For the given assumptions, the results show that the model predictions agree satisfactorily with the experiments under the different operating conditions applied.
The concentration of alkali metal vapors (especially sodium and potassium) ordinarily reaches more than 10ppm during agri-based biomass gasification, leading to several problems, as: corrosion of ...turbine blades, decreased catalytic activity and undesirable deposition on downstream equipment. Adsorption on aluminosilicates is thought to be an interesting option to reduce alkali concentration in syngas thus generated. Therefore, in this work, six samples of mineral sorbents were exposed to sodium vapors at high temperatures and under moisture conditions. Before and after sodium vapor exposure, samples were characterized by various analytical techniques, textural analysis, TGA, XRD and XRF, aimed at better understanding of the binding mechanisms and assessing their ability to remove sodium from the gas phase. The combination of all techniques allowed the confirmation of the sorption mechanisms, which is chemisorption in most cases, with the formation of silicates and aluminosilicate salts. Sorbents with higher Al content, such as green clay and bauxite, showed potential for the application of capturing alkali metal vapors at high temperatures in the presence of steam by fixing sodium as nepheline (NaAlSiO4). Sorbents with higher silica content (e.g., diatomite and kaolin) showed irreversible fixation of Na, which could not be recovered even upon acid leaching. The presence of elements other than Si and Al (e.g. Ca) also plays an important role in Na sorption.
•Sorption is an interesting option to reduce alkali concentration in syngas.•Aluminum content in the sorbent seems to play an important role on alkali retention.•Calcium oxide in the structure is also believed to improve the sorption capacity.•Chemisorption is the predominant mechanism of alkali retention on mineral adsorbents.
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