A magnesium-based metal organic framework (MOF), also known as Mg-MOF-74, was successfully synthesized, characterized, and evaluated for adsorption equilibria and kinetics of CO₂ and CH₄. The ...Mg-MOF-74 crystals were characterized with scanning electron microscopy for crystal structure, powder X-ray diffraction for phase structure, and nitrogen adsorption for pore textural properties. Adsorption equilibrium and kinetics of CO₂ and CH₄ on the Mg-MOF-74 adsorbent were measured in a volumetric adsorption unit at 278, 298, and 318K and pressures up to 1bar. It was found that the Mg-MOF-74 adsorbent prepared in this work has a median pore width of 10.2Å, a BET specific surface area of 1174m²/g, CO₂ and CH₄ adsorption capacities of 8.61mmolg⁻¹ (37.8wt.%) and 1.05mmolg⁻¹ (1.7wt.%), respectively, at 298K and 1bar. Both CO₂ and CH₄ adsorption capacities are significantly higher than those of zeolite 13X under similar conditions. The pressure-dependent equilibrium selectivity of CO₂ over CH₄ (qCO₂/qCH₄) in the Mg-MOF-74 adsorbent showed a trend similar to that of zeolite 13X and the intrinsic selectivity of Mg-MOF-74 at zero adsorption loading is 283 at 298K. The initial heats of adsorption of CO₂ and CH₄ on the Mg-MOF-74 adsorbent were found to be 73.0 and 18.5kJmol⁻¹, respectively. The adsorption kinetic measurements suggest that the diffusivities of CO₂ and CH₄ on Mg-MOF-74 were comparable to those on zeolite 13X. CH₄ showed relatively faster adsorption kinetics than CO₂ in both adsorbents. The diffusion time constants of CO₂ and CH₄ in the Mg-MOF-74 adsorbent at 298K were estimated to be 8.11×10⁻³ and 4.05×10⁻²s⁻¹, respectively, showing a modest kinetic selectivity of about 5 for the separation CH₄ from CO₂.
Non-noble metal catalyzed transfer hydrogenation of biomass using biomass-derived formic acid (FA) as hydrogen source is one of promising strategies for relieving fossil energy crisis. Since acidic ...FA would destroy and deactivate naked active sites, developing heterogeneous catalysts with stabilized structure and activity that are qualified in harsh conditions is highly desirable but challenging. Herein, mesoporous N-doped carbon encapsulated Co catalysts (Co-N-C) are synthesized through a facile carbonization of Co(phen)2(OAc)2 with nano-MgO as porogen agent. After acid treatment, the optimized Co-N-C-700 (pyrolyzed at 700 °C) could afford full furfural (FAL) conversion as well as >99% furfuryl alcohol (FOL) selectivity with only 3.5 equiv. FA at 150 °C for 6 h, exhibiting much superior performance than commercial Pd-, Pt- and Ru-based catalysts. Using molecular H2 as hydrogen source not only affords low conversion but also leads to over-hydrogenation of FOL and generation of furfuryl formate (FF). This catalyst is very stable in acidic FA and could be recycled 5 times without deactivation or leaching. Co-N-C-700 is also capable for gram-scale transfer hydrogenation of FAL and is versatile for other aldehydes with >90% yield of desired products. This work could promote the application of encapsulated Co-based catalysts for selective transformation of biomass in chemical industry.
Earth-abundant and acid-resistant Co encapsulated in mesoporous N-doped carbon (Co-N-C) is highly efficient for CTH of biomass-derived FAL to FOL with FA under base-free conditions, exhibiting much superior performance than commercial Pd-, Pt- and Ru-based catalysts. Display omitted
•Cobalt confined by mesoporous N-doped carbon was used for CTH of furfural with formic acid under base-free condition.•The optimized Co-N-C-700 shows 100 % furfural conversion as well as 99% furfuryl alcohol selectivity at 150 oC for 6 h.•Only 3.5 equiv. formic acid is enough for achieving high yield of alcohol.•H2 not only affords low conversion but also leads to over-hydrogenation of alcohol and generation of furfuryl formate.•Co-N-C-700 is scalable, tolerant to acid and could be recycled 5 times without deactivation or leaching.
Separation of olefin/paraffin is an energy-intensive and difficult separation process in petrochemical industry. Energy-efficient adsorption process is considered as a promising alternative to the ...traditional cryogenic distillation for separating olefin/paraffin mixtures. In this work, we explored the feasibility of adsorptive separation of olefin/paraffin mixtures using a magnesium-based metal–organic framework, Mg-MOF-74. Adsorption equilibria and kinetics of ethane, ethylene, propane, and propylene on a Mg-MOF-74 adsorbent were determined at 278, 298, and 318 K and pressures up to 100 kPa. A dual-site Sips model was used to correlate the adsorption equilibrium data, and a micropore diffusion model was applied to extract the diffusivities from the adsorption kinetics data. A grand canonical Monte Carlo simulation was conducted to calculate the adsorption isotherms and to elucidate the adsorption mechanisms. The simulation results showed that all four adsorbate molecules are preferentially adsorbed on the open metal sites where each metal site binds one adsorbate molecule. Propylene and propane have a stronger affinity to the Mg-MOF-74 adsorbent than ethane and ethylene because of their significant dipole moments. Adsorption equilibrium selectivity, combined equilibrium and kinetic selectivity, and adsorbent selection parameter for pressure swing adsorption processes were estimated. The relatively high values of adsorption selectivity suggest that it is feasible to separate ethylene/ethane, propylene/propane, and propylene/ethylene pairs in a vacuum swing adsorption process using Mg-MOF-74 as an adsorbent.
In present study, the performance and separation characteristics of five macroporous resins for the enrichment and purification of asiaticoside and madecassoside from
Centella asiatica extracts have ...been evaluated. The adsorption and desorption properties of total triterpene saponins (80% purity) on macroporous resins including HPD100, HPD300, X-5, AB-8 and D101 have been compared. According to our results, HPD100 offered higher adsorption and desorption capacities and higher adsorption speed for asiaticoside and madecassoside than other resins. Column packed with HPD100 resin was used to perform dynamic adsorption and desorption tests to optimize the separation process of asiaticoside and madecassoside from
C. asiatica extracts. After the treatment with gradient elution on HPD100 resin, the content of madecassoside in the product increased from 3.9 to 39.7%, and the recovery yield was 70.4%; for asiaticoside the content increased from 2.0 to 21.5%, and the recovery yield was 72.0%. The results showed that HPD100 resin revealed a good ability to separate madecassoside and asiaticoside, and the method can be referenced for the separation of other triterpene saponins from herbal raw materials.
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•ACs exhibited activity similar to Ru/C toward the denitrogenation and deoxygenation.•Bamboo stem AC provided the highest performance.•Leach ions and weak acids into the reaction ...solution catalyze the upgrading reaction.•ACs showed different roles from the noble metal for the upgrading of bio-oil.•All of the upgraded bio-oils had a large fraction (>80%) boiling below 350°C.
This study examined a two-stage (noncatalytic pretreatment followed by catalytic upgrading) hydrothermal processing of crude bio-oil produced from the hydrothermal liquefaction of duckweed. The activities of six activated carbons (ACs)-pine wood AC, coconut shell AC, bamboo stem AC, apricot pit AC, peach pit AC, and coal AC-toward the deoxygenation and denitrogenation of the pretreated duckweed bio-oil were determined in supercritical water at 400°C for 1h with the addition of 6MPa of H2 and 10wt% AC. All of the ACs exhibited activity similar to Ru/C toward the denitrogenation and deoxygenation of the pretreated duckweed bio-oil. Of the ACs tested, bamboo stem AC produced an upgraded bio-oil with the highest yield (76.3wt%), the highest fraction (90.13%) of material boiling below 350°C, and the highest energy density (44.1MJ/kg). Decreased ash and acidic groups in the pre-treated AC disfavored the production of upgraded bio-oil but aided denitrogenation and desulfurization. The ACs are suspected to leach ions and weak acids into the reaction solution, which would catalyze denitrogenation and desulfurization. The gases mainly consisted of unreacted H2, CO2 and CH4 together with small amounts of CxHy (x≤5, y≤12) hydrocarbon gases produced from the cracking of the upgraded bio-oil.
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•Highly active Pt/ZrO2 catalyst was synthesized by the atomic layer deposition.•Atomic layer deposition produced highly dispersed and uniform Pt particles.•Pt/ZrO2 showed excellent ...activity for the base-free oxidation of 5-HMF.•The highest 2,5-FDCA yield of 97% with a 5-HMF conversion of 100% was obtained.
The oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-furandicarboxylic acid (2,5-FDCA) under base-free condition is one of the most attractive reactions. This work first reported the synthesis of highly efficient oxidation of 5-HMF to 2,5-FDCA catalyst using the atomic layer deposition (ALD) to deposit Pt nanoparticles on low surface area zirconium oxide (ZrO2). Pt/ZrO2 synthesized by ALD showed excellent activity for the oxidation of 5-HMF to 2,5-FDCA in base-free solution compared with Pt/MOx synthesized by other methods in this work or reported already. The highly dispersed and uniform particle size of Pt particles were demonstrated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and temperature programmed desorption of CO (CO-TPD), which provided a striking improvement of the catalytic activity in the oxidation of 5-HMF. An enhanced CO adsorption property of Pt/ZrO2 obtained by ALD was also characterized by CO-TPD. The enhanced adsorption property of CO facilitated a stronger adsorption between catalyst and reactant/intermediates, which associated with the high dispersion and uniform particle size distribution of Pt particles to make the adsorbed reactant be efficiently converted to 2,5-FDCA.
Porous carbons with different textural properties exhibit great differences in CO2 adsorption capacity. It is generally known that narrow micropores contribute to higher CO2 adsorption capacity. ...However, it is still unclear what role each variable in the textural properties plays in CO2 adsorption. Herein, a deep neural network is trained as a generative model to direct the relationship between CO2 adsorption of porous carbons and corresponding textural properties. The trained neural network is further employed as an implicit model to estimate its ability to predict the CO2 adsorption capacity of unknown porous carbons. Interestingly, the practical CO2 adsorption amounts are in good agreement with predicted values using surface area, micropore and mesopore volumes as the input values simultaneously. This unprecedented deep learning neural network (DNN) approach, a type of machine learning algorithm, exhibits great potential to predict gas adsorption and guide the development of next‐generation carbons.
Learn on me: The artificial neural network, a type of machine learning algorithm, is used to model the relationship between CO2 adsorption capacity and the textural properties of porous carbon. Then, it is used as an implicit model to precisely predict the CO2 adsorption capacity of unknow porous carbons based on its textural properties.
Glycerol hydrogenolysis activity over Cu/Zn–Mg–Al–O catalysts depended strongly on its basicity and hydrogen spillover also enhanced its performance. The calculated TOF of surface Cu atom in ...Cu0.4/Zn0.6Mg5.0Al2O8.6 reached 26.6h−1 at 200°C in aqueous solution. Display omitted
► The acidity/basicity of Cu/Zn–Mg–Al–O catalysts could be manipulated via adjusting Zn/Mg ratio. ► The conversion of glycerol depended strongly on the basicity of Cu/Zn–Mg–Al–O. ► Hydrogen spillover from Cu to ZnO also enhanced its catalytic performance. ► Cu0.4/Zn0.6Mg5.0Al2O8.6 exhibited the best performance for hydrogenolysis of glycerol at 180°C. ► The TOF of surface Cu atom in Cu0.4/Zn0.6Mg5.0Al2O8.6 reached 26.6h−1 at 200°C.
A series of Cu0.4/Zn5.6−xMgxAl2O8.6 catalysts with different Zn/Mg ratios were prepared and used in hydrogenolysis of glycerol in aqueous solution. This reaction proceeded more easily and efficiently over Cu0.4/Zn0.6Mg5.0Al2O8.6 than Cu0.4/Mg5.6Al2O8.6 and Cu0.4/Zn5.6Al2O8.6. The selectivity of 1,2-propanediol is higher than 98.6% in all experiments over Cu0.4/Zn0.6Mg5.0Al2O8.6, and the activity of surface Cu atoms reached 26.6h−1 at 200°C. The structure, morphology, acidity (basicity), and adsorption ability of glycerol/hydrogen for these catalysts were characterized and discussed. It was concluded that the conversion of glycerol depended strongly on the basicity of these Cu-based catalysts and hydrogen spillover also enhanced its performance.
Al2O3-supported Cu and Ni monometallic as well as Cu–Ni bimetallic catalysts were synthesized using a coprecipitation method and studied for the in-situ hydrogenation of furfural (FAL) with ...isopropanol as the solvent and hydrogen donor. The Cu–Ni bimetallic catalysts showed improved activity toward the production of 2-methylfuran (2-MF) and 2-methyltetrahydrofuran (2-MTHF) over that of monometallic catalysts. The results indicated that isopropanol exhibited better performance than methanol for the in-situ hydrogenation of FAL to produce 2-MF and 2-MTHF under the same conditions. The reaction conditions such as the copper–nickel ratios, catalyst loading amount, reaction temperature, and time were optimized. After the reaction was complete, the supported Cu–Ni bimetallic catalyst could be reused four times without a significant loss in catalytic activity.
A Pt–Ni/AC bimetallic catalyst was prepared by atomic layer deposition of Pt nanoparticles on the surface of Ni/AC for base-free oxidation of 5-hydroxymethylfurfural (5-HMF) to ...2,5-furandicarboxylic acid (2,5-FDCA). A comparison of the Pt–Ni bimetallic catalyst with Ni and the Pt monometallic catalyst was demonstrated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and temperature-programmed desorption of CO (CO-TPD). Compared with the Ni/AC and Pt/AC (1.6 wt % Pt) catalysts, the bimetallic Pt–Ni/AC catalyst had a higher activity for the oxidation of 5-HMF to 2,5-FDCA, with only a 0.4 wt % Pt loading. A 97.5% yield of 2,5-FDCA with 100% 5-HMF conversion was obtained after 15 h at 100 °C. A mass-based activity value of 35.8 h–1 was obtained over the Pt–Ni/AC-15ALD catalyst. The combination of Pt with Ni increased the ability of Pt for CO adsorption and oxidation, thus increasing the activity of the Pt catalyst. Finally, the catalyst showed good reusability for at least four times without any reduction in the catalytic activity.
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