Adsorption Breakthrough Research Articles

Miniplant-Scale Demonstration of Ethylene Adsorption Separation in Downstream of an Oxidative Coupling of Methane Process

Developing an efficient sorbent and adopting an ethylene adsorption separation unit in downstream of an oxidative coupling of methane (OCM) process were the main focus of the present study. Since the mole fraction of the generated ethylene in the OCM reactor outlet is relatively low, the processing cost of the accompanying components and thereby the separation cost per ton of ethylene using the conventional cryogenic separation are insupportable. Zeolite 13X was modified in this research, demonstrating outstanding ethylene adsorption capacity and selectivity. The conducted adsorption experiments at a miniplant-scale unit enabled monitoring the adsorption breakthrough times and measuring the sorbents’ capacity under different operating pressures in the range of 1–5 bar while processing different feed flow and feed compositions, representing the attachment of the adsorption unit to different parts of the OCM process. The modified zeolite 13X showed superior performance than the reference sorbents such as zeolite 4A and activated carbon. Physical treatment of zeolite 13X, by calcining it at 550 °C, proved to be efficient in increasing its adsorption capacity. Chemically treating zeolite 13X via copper exchange on the other side increased its ethylene adsorption selectivity in competition to CO2 adsorption. In processing the CO2-rich feed streams (with the CO2 content 2.25 times of its C2H4 content), the Cu-exchanged zeolite 13X showed a promising ethylene adsorption capacity of 0.46 molC2H4·kgs–1 combined with an adsorption selectivity of 0.45 molC2H4·molCO2. In processing the CO2-free feed streams (with the C2H4 content 2.75 times of its C2H6 content), using the calcined zeolite 13X secured the highest adsorption capacity of 1.4 molC2H4·kgs–1 along with an adsorption selectivity of 3.8 molC2H4·molC2H6 under 5 bar adsorption pressure. These indicate the promising potentials of the developed sorbents and the designed adsorption unit for processing the OCM reactor outlet gas stream before and after removal of its CO2 content.

Fixed-bed adsorption of bisphenol A onto organoclay: Characterisation, mathematical modelling and theoretical calculation of DFT-based chemical descriptors

Bisphenol A (BPA) is a noteworthy and ubiquitous chemical of concern. Up to this day, several methods of water remediation have already been tested, however, few studies have addressed the fixed-bed adsorption of this contaminant. In this regard, this work aimed to evaluate the continuous adsorption of BPA using an organoclay (Spectrogel® type-C) as an adsorbent. The material passed through a series of characterisation techniques to elucidate the impact of the contaminant uptake onto the organoclay. The effect of the operation conditions on the adsorption behaviour was evaluated through breakthrough curves and the calculation of mass transfer and efficiency parameters The system conducted at 0.6 mLmin−1 and 0.2 mmolL−1 obtained the highest removal (95%) until breakthrough point (19.29 h), as well as greater breakthrough and exhaustion adsorption capacities (0.0424 and 0.2151 mmolg−1, respectively). The breakthrough curves were correlated by five distinctive models and the modified dose response model showed the finest fitting to the data (R2 >0.97). Furthermore, the regeneration potential of the spent adsorbent was investigated. It was observed that NaOH solution was a satisfactory eluent. Moreover, density functional theory (DFT) calculations were studied to give further insights regarding BPA adsorption.

Influence of the water vapor on the activity of CuO/SBA-15 SOx adsorbents

Both the performance and regenerability of SO2 adsorbents made of CuO supported on SBA-15 ordered mesoporous silica were studied for a cyclic DeSOx process under wet and dry conditions. H2O vapor decreases the performance of a 16 wt% loading CuO/SBA-15 (16CuO/SBA-15) adsorbent along the adsorption/regeneration cycles performed at 400 °C. Indeed, the SO2 breakthrough adsorption capacity of this adsorbent after ten adsorption- regeneration cycles under wet conditions (5 vol% of H2O) decreases of 61% compared to the SO2 performance obtained under dry conditions. The impact of the temperature as well as the CuO loading on the performance and regenerability of CuO/SBA-15 sorbents were also investigated under dry and wet conditions. XRD, TEM/EDX, N2 physisorption characterizations of the adsorbents were performed after the last cycle to correlate the structural and textural properties of the adsorbents and therefore the copper species, with the performance of the adsorbents. Increasing the temperature up to 450 °C with or without water increases the SO2 adsorption capacity of the 16CuO/SBA-15 adsorbent with higher SO2 adsorption capacity at 450 °C with water than without water. In the presence of water vapor, the 8CuO/SBA-15 adsorbent presents the highest average loss of SO2 adsorption capacity at the breakthrough of around 71% when expressed in mgSO2/gCuO, compared to the ones obtained with the 16CuO/SBA-15 and the 26CuO/SBA-15 adsorbents. The increase of the CuO loading up to 26 wt%, shows that the contribution of the surface copper active phase highlighted by the desorption curves, decreases significantly for the highest CuO loading under wet conditions. Moreover, with or without water, the highest total SO2 adsorption capacities obtained after the tenth cycle are observed for the lowest CuO loading (8 wt% of CuO: 547 and 495 mgSO2/gCuO without and with H2O, respectively). These higher total SO2 adsorption capacities could be explained by a better CuO phase dispersion on the SBA-15 support, which makes the copper active species more reactive especially with H2O.

Drastically boosting volatile acetone capture enabled by N-doping activated carbon: An interesting deep surface digging effect

Affording the ultrahigh structural properties and rich surface groups in traditional activated carbon (AC) together to enable the efficient control of polar volatile organic chemicals (VOCs) is significant but challenged. Herein, we report the skilled construction of super activated carbon (AC) adsorbent (SBET = 4402 m2 g−1) via N-doping tactic to trigger the deep surface digging effect for banana peel-derived AC (SBET = 3897 m2 g−1) and remarkably reinforced the multilayer adsorption behavior by the post-implanted surface N species. Impressively, the resultant optimized adsorbent UC-5 shows nearly 1.83 folds enhancement of polar VOCs(volatile organic chemicals) that acetone adsorption capacity (44.89 mmol g−1) under 30 kPa of acetone partial pressure compared to the original AC (24.57 mmol g−1), which is known as the record acetone adsorption capacity. Besides, the boosting adsorption effect was well inherited and enlarged under a higher saturated vapor pressure of acetone in the static adsorption process, which was further evidenced by dynamic adsorption breakthrough experiments. The intensive studies revealed that the surface digging of the used urea dopant not only contributed to the enriching of surface N and improved the structural properties and thermal stability (575 °C) but also reserved more oxygen content of original AC compared to the resulted counterparts using melamine, which were together responsible for the drastic increase of acetone adsorption. This work provides the new possibility for the adsorption of polar VOCs gas via exploiting the outstanding structural properties and surface N interaction.

Fixed bed adsorption of Pb and Cu by iron modified bamboo, bagasse and tyre biochar

Biochar has been successfully used for remediation of inorganic and organic pollutant from aqueous and soil medium. Easy availability of raw materials, low-cost preparation, an alternative for solid waste management and efficient removal of pollutants make biochar a better option in comparison to conventional adsorbents. In the present study, effect of iron modified biochar (MBC) prepared from bamboo (Fe-BBm), bagasse (Fe-BBg) and tyre (Fe-Ty) was investigated on fixed bed adsorption of lead (Pb) and copper (Cu). Different doses of prepared biochar (BC) without modification (BBm, BBg and Ty) were also tested and compared. Mathematical parameters of breakthrough curves (BTC) were calculated to understand the adsorption of Pb and Cu by BC and MBC. The results revealed that equilibrium adsorption (qe) and removal efficiency (R%) increased with increase in dose of BC and MBC. MBC showed better breakthrough profile and adsorption than BC for Pb removal. Maximum removal of Pb (75.75%) and qe (0.15 mg/g) was done by 10% FeTy. In case of Cu removal, maximum removal (59.44%) and qe (0.12 mg/g) was found for 10% BBm. Experimental results were analysed by different models such as Thomas, Adam-Bohart and Wolborska. Experimental results of both Pb and Cu adsorption fitted well to Thomas model with R2 (0.94 for Pb and 0.93 for Cu). FeTy and BBm proved better adsorbents for Pb and Cu that can be upscaled for heavy metal removal from polluted fields and large-scale environmental applications.

Perfluoroalkyl substances (PFAS) adsorption in drinking water by granular activated carbon: Influence of activated carbon and PFAS characteristics

Perfluoroalkyl substances (PFAS) persistence in the environment leads to their presence in drinking water, that is of high concern due to their potential human health risk. Adsorption onto activated carbon (AC) has been identified as an effective technique to remove PFAS. Adsorption isotherms and breakthrough curves, determined by rapid small-scale column tests (RSSCTs), were studied for eight PFAS and four granular ACs, characterized by different origins, porosities and numbers of reactivation cycles. Both batch and RSSCT results highlighted the strong interaction of AC and PFAS characteristics in adsorption capacity. The most important factor affecting AC performance is the surface charge: a positively-charged AC showed higher adsorption capacities with greater Freundlich constants (KF) and later 50% breakthroughs compared to the AC with neutral surface. Among the positively-charged ACs, a microporous AC demonstrated higher adsorption capacities for hydrophilic and marginally hydrophobic PFAS, while the mesoporous AC performed better for more hydrophobic PFAS, possibly due to lower pore blockage by organic matter. These results were confirmed at full-scale through a one-year monitoring campaign, in which samples were collected at the inlets and outlets of GAC systems in 17 drinking water treatment plants spread in a wide urban area, where the four analyzed ACs are used.

Experimental and Numerical Investigation into the Heat- and Mass-Transfer Processes of n-Butane Adsorption on Activated Carbon.

In this work, the adsorption parameters of n-butane vapor on an absorbent were tested following the fixed-bed method. According to the corresponding experiments, the maximum adsorption capacity and breakthrough time of activated carbon (AC) are 0.2674 g·g–1 and 924 min, respectively. According to the two-energy-state model formula and the classical adsorption heat formula, the values of theoretical and actual adsorption heat of AC adsorbing n-butane are 5.48 and 5.56 kJ·mol–1, respectively. The model for adsorption of n-butane by an AC fixed bed is based on the analytical solutions to the mass, momentum, and energy conservation equations. The model is built using porous media zone in ANSYS Fluent, the implementation of the model into ANSYS Fluent under user-defined functions (UDFs) is also described, the mass source term Si and energy source term ST are loaded into Fluent through UDF, and then the mass- and heat-transfer processes of AC in the absorption of n-butane are simulated. Furthermore, the predictions by ANSYS Fluent are compared with in situ experimental data, and the deviation rate of breakthrough time and temperature of six monitoring points is less than 5%. The results verify the accuracy and feasibility of computational fluid dynamics (CFD). Therefore, the model can be used to predict the engineering application of the adsorption of organic gases by various porous media.

Evidence of the dominant role of particle size in controlling the dynamic adsorption breakthrough behavior of gaseous benzene in a microporous carbon bed system

To learn more about the competing roles of the key process variables (e.g., particle size vs. space velocity) in the adsorption of volatile organic compounds (VOCs), the breakthrough (BT) behavior of gaseous benzene (at 3 Pa) was investigated using microporous activated carbon (AC) beds built individually with each of four different particle size ranges (<0.6, 0.6–1.7, 1.7–2.36, and 2.36–5 mm) at three flow rates (300, 500, and 1000 mL min−1). The effects of each variable on AC performance were evaluated in relation to the occurrence patterns of BT. The key performance metrics (e.g., capacity and partition coefficient) generally increased with decreases in particle size and flow rate, reflecting the critical role of sorbent bed physical properties (e.g., surface area, space velocity, and residence time) in the adsorption process. The smallest particle group (<0.6 mm) exhibited the highest uptake rate in the initial BT stage in terms of breakthrough volume (BTV: L g−1) (e.g., BTV5% (5% BTV) = 424 L g−1). In contrast, the order for 100% BT was reversed to record the highest at the largest particle group (2.36 – 5 mm). The kinetic modeling suggests the dominant role of the pore-diffusion mechanism on the overall adsorption process with enhanced benzene uptake rate onto smaller carbon particle sizes at higher flow rates. Based on this work, we recommend accurate determination of the relative dominance between adsorbent particle size and space velocity to maximize the efficiency of air filtration systems for real-world applications.

Kinetic approach to modelling CO2 adsorption from humid air using amine-functionalized resin: Equilibrium isotherms and column dynamics

Humidity can up to double the adsorption capacity of CO2 in conditions relevant to direct air capture (DAC) on amine-functionalized adsorbents, but the treatment of this phenomenon in isotherm or kinetic models has been all but neglected in the literature. In this work, a kinetic model based on reaction mechanisms of CO2 adsorption on supported amines in dry and humid conditions is proposed. The kinetic model was used in modelling of humid CO2 adsorption isotherms and dynamics of fixed-bed CO2 adsorption from air. The improvement of equilibrium CO2 capacity by humidity was captured well by the kinetic model, leading to good fits of CO2 isotherms. At best, the dynamic model closely represented the whole shape of CO2 adsorption breakthrough curves in several-hour fixed-bed adsorption experiments. Therefore, the proposed kinetic model is expected to be useful in simulation of the DAC process based on supported amine-adsorbents.

Hexamethyldisiloxane removal from biogas using reduced graphene-oxide aerogels as adsorbents

Volatile methyl siloxane is a trace impurity in biogas produced by anaerobic bacteria. It decreases the energy utilization of biogas and thus needs to be removed. In this study, six reduced graphene-oxide aerogels (rGOAs) were prepared from industrial-grade multilayer graphene oxide by a hydrothermo-chemical reduction method in the presence of various amine additives, and the use of the rGOAs as adsorbents for hexamethyldisiloxane (L2) removal was investigated. The developed rGOAs were characterized via the Brunner-Emmet-Teller technique, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results revealed that the different pKa values of the amine molecules led to an increase in the rGOA contact angle, the specific surface area and the total pore volume in the following sequence: 0-rGOA < E-rGOA < A-rGOA < D-rGOA < T-rGOA < U-rGOA, representing the rGOAs without amine and those with ethylenediamine, aniline, diethylenetriamine, triethylenetetramine, and urea, respectively. Also, the adsorptive performance of the rGOAs materials for L2 was enhanced in this sequence. The adsorption capacities of rGOAs were significantly related to their textural properties and hydrophobicity. Moreover, U-rGOA exhibited the highest specific surface area (167.9 m2 g−1), total pore volume (0.737 cm3 g−1), and contact angle (146.8°), and its theory breakthrough adsorption capacity for L2 at 0 °C was 112.4 mg g−1. A lower bed-temperature, carrier gas flow rate, and inlet concentration were beneficial for the L2 adsorption by the U-rGOA. The spent U-rGOA adsorbent could be readily regenerated for reuse by heating at 80 °C. The results suggest that the rGOA materials have good application potential as adsorbents for methyl siloxane removal.

CO2 Adsorption in a Geopolymer-zeolite Composite: Experimental Dynamic Tests and Modelling Insights on Related Thermal Effects

CO2 adsorption process in a composite geopolymer/zeolite 13X material has been analysed for post combustion carbon capture application, in dynamic conditions for a CO2/N2 gas mixture. Such composite material represents a valid alternative to conventional sorbents owing to the affinity and synergy between zeolite and the geopolymer binder as well as improved mechanical resistance and lower cost. Experimental analysis has been focused both on complete adsorption tests to determine the material maximum adsorption capacity and on breakthrough tests in transient conditions in (cyclic adsorption/desorption). Particular care has been devoted to thermal effects associated to adsorption and their effect on adsorption capacity and kinetics.Experimental data have been employed to support the development of a novel numerical model, based on Sips adsorption approach for sorbent capacity, and capable to describe the adsorption process, accounting for both mass and energy transport in the sorbent bed. The model proved able to describe well the experimental data at different CO2 feed concentration, and thus it has been employed in a predictive way to inspect process operating parameters and sorbent bed design on the resulting adsorption capacity, breakthrough time, and temperature profile. In particular, the model compared the results obtained in a scaled-up configuration (suitable to an industrial application) with those of the lab-scale system.

Tetrazole-Functionalized Zirconium Metal-Organic Cages for Efficient C2 H2 /C2 H4 and C2 H2 /CO2 Separations.

Isoreticular functionalization is a well-elucidated strategy for pore environment tuning and the basis of gas separation performance in extended frameworks. The extension of this approach to discrete porous molecules such as metal-organic cages (MOCs) is conceptually straightforward but hindered by synthetic complications, especially stability concerns. We report the successful isoreticular functionalization of a zirconium MOC with tetrazole moiety by bottom-up synthesis. The title compound (ZrT-1-tetrazol) shows promising C2 H2 /CO2 and C2 H2 /C2 H4 separation performance, as demonstrated by adsorption isotherms, breakthrough experiments, and density functional theory calculations. The design analogy between MOFs and highly stable MOCs may guide the synthesis of novel porous materials for challenging separation applications.

Tetrazole‐Functionalized Zirconium Metal‐Organic Cages for Efficient C2H2/C2H4 and C2H2/CO2 Separations

AbstractIsoreticular functionalization is a well‐elucidated strategy for pore environment tuning and the basis of gas separation performance in extended frameworks. The extension of this approach to discrete porous molecules such as metal‐organic cages (MOCs) is conceptually straightforward but hindered by synthetic complications, especially stability concerns. We report the successful isoreticular functionalization of a zirconium MOC with tetrazole moiety by bottom‐up synthesis. The title compound (ZrT‐1‐tetrazol) shows promising C2H2/CO2 and C2H2/C2H4 separation performance, as demonstrated by adsorption isotherms, breakthrough experiments, and density functional theory calculations. The design analogy between MOFs and highly stable MOCs may guide the synthesis of novel porous materials for challenging separation applications.

Adsorption and desorption of gaseous naphthalene on carbonaceous sorbents: Insights into advantageous pore sizes and morphologies

Capturing and recovering naphthalene as a profitable chemical from hot flue gas are of significance in terms of environmental protection with economic benefits, for which the adsorption technology using high-performance sorbents provides the key step for success in practical applications. Carbonaceous materials with hydrophobic natures have been shown to render high affinities with non-polar naphthalene, but remain challenging due to difficulties in tackling the trade-off between adsorption and desorption. This work reports a systematic investigation with deeper insights into adsorption equilibria, kinetics and regenerabilities of gaseous naphthalene on typical carbonaceous sorbents originated from different texture properties, including ordered mesoporous carbons (CMK-3, CMK-5 and FDU-15), carbon nanotubes (SWCNT and MWCNT) and a coconut-shell-based activated carbon (AC). The adsorption isotherm and breakthrough curves at wide feed concentration ranges and temperature programmed desorption curves for each sorbent were obtained along with series of theoretical model fitting. FDU-15 and CMK-5 were demonstrated as superior sorbents with high maximum adsorption capacities (1.13 and 1.735 mmol/g) and low desorption activation energy (62.66 and 72.68 kJ/mol), respectively exhibiting advantages of the 3-dimensional diffusion-controlled desorption upon a hexagonal pore arrangement and the efficient adsorption upon a reasonable mesopore-micropore hierarchical structure, in contrast to poor kinetics on pure microporosity (AC) and 1-dimensional topologies (CNTs). Deeper insights into the morphology-affinity relationship revealed advantageous naphthalene transport behaviors over 3-dimensional ordered mesoporosities with appropriate coexisting microporosities and narrower primary size (2–5 nm) or diverse forms of mesopore, which contribute toward reaching comprehensive balances of sorption performances.

Fe-based metal organic framework derivative with enhanced Lewis acidity and hierarchical pores for excellent adsorption of oxygenated volatile organic compounds

A series of Fe-based metal organic framework derived materials were prepared by thermal treating MIL-100(Fe) in nitrogen atmosphere for adsorption removal of oxygenated volatile organic compounds (OVOCs) such as methanol, formaldehyde and acetone under dynamic conditions. The experimental results showed that the partially carbonized M-350 material obtained by calcining MIL-100(Fe) at 350 °C exhibited the best adsorption performance and high stability. The breakthrough adsorption capacity of M-350 for methanol was 61.5% higher than that of pure MIL-100 (Fe), and it was 24.7, 6.5 and 2.6 times higher than that of commercial activated carbon, ZSM-5 and SAPO-34 adsorbents, respectively. The excellent adsorption performance was attributed to the exposure of abundant coordinatively unsaturated iron metal sites acting as Lewis acid sites through high temperature calcination, which had a strong affinity for OVOCs. Meanwhile, a hierarchical porous structure and high specific surface area further promoted the adsorption. This work provides new insights into the further development of metal organic frameworks based functional materials for VOCs removal and purification.

Glycine based modification of activated carbons for VOCs adsorption

Activated carbons (ACs) derived from coconut husk were modified by impregnating with glycine, a non-polar fatty amino acids. The effect of this modification method on the physicochemical characteristics of ACs and adsorption performance of VOC were investigated and compared with ammonia modification. TEM, SEM and BET were used to identify morphology and pore structure, XPS and elemental analysis were applied to analyze surface chemistry of the tested ACs. The adsorption performance of the selected VOC of toluene was tested using a fixed-bed reactor. The results show that the breakthrough adsorption capacity of toluene over 10 wt% glycine modified AC was about 147% and 139% higher than that of the original and 5 wt% ammonia modified ACs, respectively, while the saturated adsorption capacities of glycine modified ACs were less than that of 5 wt% ammonia modified AC. Glycine can be deposited on the surface of ACs and form polypeptide chains by self-condensation, which is favorable to increase the nitrogen-containing groups and reduce the surface polarity of ACs. While ammonia modification was more beneficial to improving the specific surface area and pore volume. Therefore, ammonia/glycine composite modification technology was proposed. The improved breakthrough and saturated adsorption capacities of toluene reached 75.02 mg/g and 451.48 mg/g, respectively.

Bio-oils/FCC co-processing: Insights into the adsorption of guaiacol on Y zeolites with distinct acidity and textural properties

The guaiacol adsorption capacity of several Y zeolites with different physicochemical properties was tested by performing breakthrough adsorption experiments, in order to investigate the guaiacol adsorption on Fluid Catalytic Cracking catalysts during bio-oils/FCC feedstocks co-processing. X-Ray diffraction, nitrogen sorption measurements and pyridine adsorption followed by Infrared Spectroscopy were used to determine the framework Si/Al ratio, the textural parameters, and finally the nature and amount of acid sites. Klinkenberg model was used to fit the experimental data and to obtain the guaiacol adsorption capacity and ka (overall coefficient of mass transfer) and Ke (adsorption equilibrium constant) parameters, which are directly related to, respectively, kinetic and thermodynamic aspects. Ke values, and so guaiacol adsorption, were observed to increase with the total number of Brønsted and Lewis acid sites on the zeolites, as well as with the amount of Na exchange. Conversely, mesoporosity increases the diffusion rate of guaiacol inside the zeolite structure, leading to higher ka values and decreasing guaiacol retention. Overall, data show that guaiacol adsorption on the FCC catalysts, and so its impact on the activity, might decrease with the catalyst age, owing to the changes on the FCC catalyst properties taking place during operation.

Removal of hexavalent chromium by encapsulated chitosan-modified magnetic carbon nanotubes: Fixed-bed column study and modelling

A new type of composite adsorbent, encapsulated chitosan-modified magnetic carbon nanotubes (CS/MWCNTs/Fe) beads were used to remove hexavalent chromium (Cr(VI)) from aqueous solutions in a fixed-bed column. Among the various combination of operating parameters, we obtain a maximum volume of treated effluent (210 mL) under the following conditions: flow rate, 1 mL min−1; bed height, 8 cm; feed Cr(VI) concentration, 30 mg L−1; and solution pH, 4.0 ± 0.2. The corresponding adsorption capacity was 1.54 mg g-1 and the overall Cr(VI) removal efficiency was 54 %. In characterizing the dynamics of the adsorption process and breakthrough profiles, we found that the Thomas model and the Yoon-Nelson model both accurately described the breakthrough curves under all experimental conditions, while the Adams-Bohart model was applicable only for an early phase of dynamic behavior CtC0≤0.5 of the CS/MWCNTs/Fe beads column. Columns with shorter bed heights favored the global mass transfer rate, especially during the early breakthrough periods. Moreover, the bed depth service time (BDST) model was validated experimentally, enabling the prediction of service time of the adsorption bed at different outlet concentrations using hypothetical flow rates and inlet concentrations. Scaled-up study was performed to observe the column performance at higher throughputs. The high selectivity of Cr(VI) adsorption in the simulated wastewater in the presence of other heavy metals (copper and cadmium) and background anion (phosphate) suggests the applicability of CS/MWCNTs/Fe beads for Cr(VI) removal from industrial effluents.

Dihydroxyacetone Production: From Glycerol Catalytic Oxidation with Commercial Catalysts to Chromatographic Separation

A process for catalytic production of dihydroxyacetone through glycerol oxidation and dihydroxyacetone purification by chromatographic processes is herein presented. Glycerol oxidation over commercial Pt/AC and Pt–Bi/AC catalysts was performed on a batch reactor operating under base-free conditions, using water as a solvent and oxygen as the oxidant agent. The highest dihydroxyacetone yield obtained was 36%, using the Pt5%-Bi1.5%/AC catalyst, whereas the monometallic Pt/AC catalyst was selective to glyceric acid. It is herein reported for the first time dihydroxyacetone separation from unreacted glycerol and reaction byproducts (organic acids). Two commercial polystyrene-divinylbenzene ion-exchange resins were used as a stationary phase, one in the hydrogen form and the other in the calcium form, and water was used as the mobile phase. Adsorption equilibrium data for the species present in the reaction mixture were determined in both resins through single-component adsorption breakthrough experiments. A continuous chromatographic separation process was designed based on the simulated moving bed (SMB) technology and simulated using the gPROMS model builder software. A two SMB cascade was then considered, performing the pseudobinary mixture separation on the first SMB. The extract stream from the first SMB containing dihydroxyacetone and glycerol was fed to the second SMB, obtaining dihydroxyacetone with a purity of 97%. Considering the overall unit, a dihydroxyacetone productivity of 64 kgDHA (LAds day)−1 was obtained with an eluent consumption of 1218 LDes kgDHA–1.

Facile synthesis of hierarchical micro-mesoporous HKUST-1 by a mixed-linker defect strategy for enhanced adsorptive removal of benzothiophene from fuel

Developing high-efficiency adsorbents is crucial for removing aromatic sulfur containing compounds from the fossil fuels. HKUST-1 is considered as a promising candidate of adsorbents for deep desulfurization. However, the typical HKUST-1 possesses only micropores, which restricts the diffusion and limits the desulfurization capacity. Herein, we proposed a mixed-linker defect strategy to construct a bimodal micro-mesoporous HKUST-1 to enhance adsorptive removal of benzothiophene (BT) from fuels. A rapid microwave-assisted synthetic route was developed for preparing a series of micro-meso porous OH-HKUST-1-x (x = 0.1, 0.2 and 0.3) by adjusting the ratio of 5-hydroxyisophthalic acid to benzene-1,3,5-tricarboxylate acid. This series of hierarchically porous metal-organic frameworks (MOFs) features 0.7–0.8 nm and 3.4–3.8 nm micropore and mesopore, respectively. The effects of linker defects on the chemical and physical properties of the materials were systematically studied. The X-ray diffraction patterns showed that the as-synthesized OH-HKUST-1-x containing hydroxyl defects still retained the original crystal structure. The OH-HKUST-1-x exhibited a higher desulfurization efficiency in comparison with HKUST-1, because with increasing the mole ratio of the mixed linkers, larger pore diameters were generated. The bimodal micro-mesoporous structure facilitates adsorbates diffusion and leads to higher exposure of the unsaturated adsorptive site of Cu2+ than the microporous structure. The as-synthesized OH-HKUST-1-0.2 displayed the best performance towards adsorptive removal of BT, the static and breakthrough adsorption capacity achieved 26.30 mg S g−1 and 0.0490 mmol g−1, respectively. Additionally, after the OH-HKUST-1-0.2 was regenerated six times it still had a desulfurization performance as 88.3% of the fresh adsorbent.