Nowadays, natural gas (NG) has been widely studied as an alternative to petroleum-based fuels. However, when extracted from unconventional sources, it is contaminated with N
2
. Its removal is ...industrially done by cryogenic distillation, which is an extremely energy-intensive process. Therefore, adsorption-based methods are of particular interest, and the application of metal–organic frameworks (MOFs) in adsorption-based processes focus on separating different mixtures. This way, the goal of this work was to test a functionalized zirconium-based MOF, the
UiO-66(Zr)
_
(COOH)
2
, to be used in a gas-phase simulated moving bed (SMB) process for the purification of nitrogen contaminated methane streams, which is the case of methane obtained from shale gas, landfill gas and coalbeds. The adsorbent material was supplied by KRICT (Korea Research Institute of Chemical Technology) as granules. Firstly, the adsorption isotherms of pure C
2
H
6
were determined at 303, 333, and 373 K. The dual-site Langmuir (DSL) isotherm was used to fit the experimental results. The equilibrium data for ethane was compared with previously measured data for CH
4
, N
2,
and CO
2
. The affinity of the gas towards the adsorbent has the following order,
CO
2
>
C
2
H
6
≫
CH
4
>
N
2
, from the most adsorbed to the less adsorbed at 303 K and 1.5 bar. At 333 K and 1.5 bar,
C
2
H
6
exhibits the highest uptake. Single, binary, and pseudo-ternary breakthrough curves were performed at 333 K and 1.5 bar. These experimental results allowed experimental validation of adsorption equilibrium predicted by the multicomponent extension of the DSL isotherm and the validation of the fixed-bed mathematical model, as well as the evaluation of the ability of the eluent of displacing the mixture and its own displacement by the mixture. Lastly, a gas-phase SMB process was designed, based on the simulation of the separation regions for each one of the target desorbents, operating at 303 K and 1.5 bar, using four-zone unit configuration (2–3–2–1), in a closed-loop. This process allows the production of a methane stream with 99.56% purity and 99.65% recovery and a nitrogen stream with 99.73% purity and a recovery of 99.58%, showing the potential of this technology for the separation of CH
4
/N
2
mixtures.
Abstract
Increasing greenhouse gas emissions contributing to the global climate change are a major concern of environmental protection. Developing adsorbents from low‐cost and renewable resources is ...an attractive strategy. On the other hand, the high capacity of production rates of municipal solid waste, besides high methane emissions, is the origin of some eco‐systemic challenges. The combination of the two environmental problems is considered by introducing the compost from a mechanical biological treatment of municipal solid wastes as a low‐cost source of adsorbent for CO
2
capture. The obtained compost was thermally and chemically activated and the CO
2
adsorption capacities of prepared samples were evaluated. Samples prepared sequentially with sulfuric acid and heated at 800 °C and vice versa, respectively, had the highest uptake capacities and were comparable with commercial adsorbents.
Thermal parametric pumping is a cyclic adsorptive process based on periodic changes in the bed temperature simultaneously with flow reversal. This is an innovative technology which may allow removing ...phenolic compounds from waste solutions to be recovered and recycled. The recovery and/or purification of liquid streams containing phenol and 4-nitrophenol by adsorptive parametric pumping was studied in this work. An automated parametric pumping pilot unit was operated in semi-continuous recuperative mode. The adsorbent used was the polymeric resin Sephabeads SP206 (Mitsubishi Kasei Corporation, Japan) and temperatures of the hot and the cold half-cycles were 333 and 293
K, respectively. Basic data were obtained from batch equilibrium experiments and fixed-bed adsorption. Different experimental conditions were run and two simplified models were used to simulate the results: an
equilibrium model and a
linear driving force (LDF) model. Experimental and simulated results using the
LDF model were in quite good agreement. Purification levels below three orders of magnitude lower than the concentration of the feed solution were obtained for phenol and 4-nitrophenol.
We studied binary adsorption equilibrium and kinetics of propane and propylene in carbon molecular sieve 4A (Takeda Corp., Tokyo, Japan). Adsorption equilibrium was measured at 373 K with a ...manometric−chromatographic unit at two different total pressures: 47 and 250 kPa. Equilibrium of the binary mixture was well predicted with the multicomponent multisite model equation based on pure gas data. The integral thermodynamic consistency test was applied to the set of data. Adsorption kinetics were measured in fixed-bed experiments at 343, 373, and 423 K with three different propylene molar fractions: 0.29, 0.55, and 0.80. The total pressure was also varied from 110 to 320 kPa. A temperature increase in the curves with high propylene molar fractions can be detrimental to the separation of propane−propylene mixtures by vacuum−pressure-swing adsorption.
A new true moving bed (TMB) adsorptive reactor model with a detailed particle approach is presented introducing the formulation of the mass balance for the solid phase in counter-current moving ...systems. The system studied here is the enzymatic inversion of sucrose into fructose and glucose and subsequent separation of glucose/fructose; the reaction occurs both in the outer fluid phase and inside particles. Model equations include film mass transfer, intra-particle diffusion resistance, axial dispersion for the outer fluid phase, plug flow of the solid phase and linear adsorption equilibrium of glucose/fructose. This new model is compared with previous LDF-type approximations for reactive systems and applied to pure separative TMB process. The numerical solution of model equations is obtained for transient and steady state with commercial and public domain packages (gPROMS and COLNEW). The influence of the particle size and reaction rate constant is analyzed in the
(
γ
2
×
γ
3
)
reactive/separation region.
► Breakthrough curves were used to study the adsorption of C8 isomers. ► The sorption parameters were determined from single component breakthrough curves. ► A model for predicting breakthrough ...curves of mixtures of xylenes was developed. ► We present the results of experiments with the real feed mixture of Parex process.
The adsorption of C8 isomers (p-xylene, m-xylene, o-xylene and ethylbenzene) was studied under the industrial operating conditions of the Parex process. Single- and multi-component breakthrough experiments were carried out on a Barium exchanged faujasite-type zeolite as adsorbent and p-diethylbenzene as desorbent. Equilibrium isotherms of the main components of the Parex process were obtained from single component breakthrough curves with different feed concentrations in i-octane. A mathematical model is presented which, jointly with the equilibrium experimental data, is capable of satisfactorily predicting the breakthrough curves of multi-component mixtures of xylenes, including the breakthrough curves of the real Parex feed mixture.
The industrial-scale adsorptive separation of p-xylene from a mixture of C8 aromatics in a four-section simulated moving bed (SMB) unit is analyzed through simulation. In the order to describe the ...behavior of the SMB unit by means of a mathematical model, two approaches were used: the true moving bed (TMB) approach and the SMB approach. Both approaches assume a constant selectivity nonstoichiometric Langmuir isotherm, an axial dispersion for the fluid flow, and a linear driving force for the intraparticle mass transfer. The TMB and SMB model predictions of steady-state performance of the SMB unit are very close. Therefore, the TMB model was selected to study the effect of the switching time period, adsorbent deactivation, and mass-transfer resistances on the process performance. The adsorbent deactivation which occurs during its lifetime will influence the SMB performance; to keep the p-xylene purity and acceptable recovery, the switching time should be decreased. The TMB package is a useful tool for fast visualization of the SMB process behavior under particular operating conditions. The novel “separation volume” methodology is used to find the operating conditions of the SMB unit in the presence of mass-transfer resistances.
Nuts have been part of the human diet since our early ancestors, and their use goes beyond nutritional purposes, for example, as aromatic sources for dairy products. This work explores the potential ...of almond (Prunus dulcis (Mill.) DA Webb), hazelnut (Corylus avellana L.), and walnut (Juglans regia L.) extracts as sources of food flavouring agents, suggesting a new added-value application for lower quality or excess production fruits. The extracts were obtained by supercritical fluid extraction with carbon dioxide and characterized by: quantification of the volatile fraction by HS-SPME GC-MS; sensory perception and description; and cytotoxicity against Vero cells. All extracts revealed potential as flavouring ingredients due to terpene abundance. No significant differences were observed for the minimal sensory perception, in which the odour threshold values ranged from 8.3 × 10
to 6.9 × 10
μg·mL
for walnuts and almonds extracts, respectively. In contrast, the cytotoxic potential differed significantly among the extracts, and P. dulcis extract presented lower cytotoxicity. Notes as woody, fresh, and green were identified in the volatile intensifiers obtained from the P. dulcis extract. Thus, almond extract was identified as the most promising ingredient to increase the sensory value of food products, namely bread. This potential was verified by an increase in the odour perception of bread after adding 4 μL of extract to each 100 g of bread dough. The quantified eucalyptol and d-limonene terpenes - found in the P. dulcis extract - have improved the release of the pleasant and natural volatile compounds from bread crust and crumb compared to the control bread chemical and sensory profiles.
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