New Strategy To Enhance CO₂ Capture over a Nanoporous Polyethylenimine Sorbent

New Strategy To Enhance CO₂ Capture over a Nanoporous Polyethylenimine Sorben

Iron-Catalyzed Propylene Epoxidation by Nitrous Oxide: Studies on the Effects of Alkali Metal Salts

SBA-15-supported iron catalysts with and without alkali metal salt modifications were studied for propylene oxidation by nitrous oxide. The reaction route could be dramatically changed from allylic oxidation to epoxidation by modification of the FeOx/SBA-15 catalyst with alkali metal salts. The KCl-1 wt % FeOx/SBA-15 (K/Fe = 5) catalyst exhibited the best catalytic performances for propylene epoxidation, over which ca. 50% propylene oxide selectivity could be gained at a 10% propylene conversion at 648 K. Characterizations with diffuse reflectance UV−Vis, XANES, and Raman spectroscopic techniques revealed that the modification with KCl increased the dispersion of the iron species and changed the local coordination of iron into a tetrahedral configuration on the inner surface of SBA-15. This tetrahedrally coordinated iron site, which was probably stabilized by potassium ions, was proposed to account for the epoxidation of propylene by nitrous oxide. At the same time, the reactivity of lattice oxygen was inhibited, and the acidity of the FeOx/SBA-15 was eliminated. These changes should also contribute to the increase in the selectivity to propylene oxide. The counteranions in the alkali metal salts exerted a significant influence on the catalytic behaviors probably via an electronic effect

Ultra-Deep Adsorptive Desulfurization of Light-Irradiated Diesel Fuel over Supported TiO₂–CeO₂ Adsorbents

This study investigates ultra-deep adsorptive desulfurization (ADS) from light-irradiated diesel fuel over supported TiO2–CeO2 adsorbents. A 30-fold higher desulfurization capacity of 95 mL of fuel per gram of adsorbent (mL-F/g-sorb) or 1.143 mg of sulfur per gram of adsorbent (mg-S/g-sorb) was achieved from light-irradiated fuel over the original low-sulfur fuel containing about 15 ppm by weight (ppmw) of sulfur. The sulfur species on spent TiO2–CeO2/MCM-48 adsorbent was identified by sulfur K-edge XANES as sulfones and the adsorption selectivity to different compounds tested in a model fuel decreases in the order of indole > dibenzothiophenesulfone ≫ dibenzothiophene > 4-methyldibenzothiophene > benzothiophene > 4,6-dimethyldibenzothiophene > phenanthrene > 2-methylnaphthalene ∼ fluorene > naphthalene. The results suggest that during ADS of light-irradiated fuel, the original sulfur species were chemically transformed to sulfones, resulting in the significant increase in desulfurization capacity. For different supports for TiO2–CeO2 oxides, the ADS capacity increases with a decrease in the point of zero charge (PZC) value; for silica-supported TiO2–CeO2 oxides (the lowest PZC value of 2–4) with different surface areas, the ADS capacity increases monotonically with increasing surface area. The supported TiO2–CeO2/MCM-48 adsorbent can be regenerated using oxidative air treatment. The present study provides an attractive new path to achieve ultraclean fuel more effectively

Sulfuric Acid Modified Bentonite as the Support of Tetraethylene­pentamine for CO₂ Capture

In this work, an inexpensive and commercially available bentonite was modified by sulfuric acid and explored as the new type of support to immobilize tetraethylene­pentamine (TEPA) for CO₂ capture from flue gas. By applying sulfuric acid treatment, the textural properties, in particular, pore volume and surface area of bentonite, were significantly improved. Bentonite treated with 6 M sulfuric acid (Ben_H₂SO₄_6M) can reach a pore volume of 0.77 cc/g from that of the parent bentonite of 0.15 cc/g. With the maximum TEPA loading of 50 wt % onto the Ben_H₂SO₄_6M sorbent, the maximum CO₂ breakthrough sorption capacity reached 130 mg of CO₂/g of sorbent at 75 °C under a dry condition. With an addition of moisture to the simulated flue gas, the CO₂ sorption capacity can be further improved to 190 mg of CO₂ at 18 vol% of moisture addition sorbent due to the bicarbonate formation under a wet condition. The TEPA/Ben_H₂SO₄_6M sorbents show a good regenerability and thermal stability below 130 °C. The high CO₂ sorption capacity, positive effect of moisture addition, and low capital cost of the raw bentonite materials imply that TEPA/Ben_H₂SO₄_6M could be a promising sorbent for cost-efficient CO₂ capture from flue gas. The sulfuric acid treatment was demonstrated as an effective method for bentonite modification to immobilize TEPA for CO₂ capture

Promotional Effect of Dispersant Modification to ZnCr on CO₂ Hydrogenation into Aromatics over Hybrid Catalysts

The hybrid catalyst through coupling metal oxides and zeolite is a strategy for converting CO2 to the targeted hydrocarbons containing aromatics. Herein, we framed an active hybrid catalyst comprising ZnCr oxide and HZSM-5 zeolite for conversion of CO2 to aromatics. The usage of dispersants (PEG or TPABr) in the process of preparing ZnCr oxide is certainly effective to improve the yield of aromatics. Over the hybrid catalyst ZnCr-TPABr + HZSM-5 with TPABr as a dispersant, the total hydrocarbon (HCt) selectivity increases to 37.4% at 330 °C, obviously higher than that over the hybrid catalyst ZnCr-none + HZSM-5 without a dispersant (29.5%), wherein C5+ hydrocarbons in the HCt account for above 69%. Moreover, the proportion of aromatics in C5+ products is improved to 87.9 from 79.4%. Multitechnique characterizations demonstrate that the usage of the TPABr dispersant induces smaller crystal sizes, the formation of more nonstoichiometric ZnCrxOy spinels and oxygen vacancies, and the accumulation of ZnO on the surface of the ZnCr-TPABr oxide, which are in favor of the adsorption of CO2 and the formation of the intermediate methanol or its precursor, methoxyl, finally leading to the improved catalytic performance

Visible-Light-Promoted Trifluoromethylthiolation and Trifluoromethylselenolation of 1,4-Dihydropyridines

We report a metal-free trifluoromethylthiolation and trifluoromethylselenolation of 1,4-dihydropyridines with S-(trifluoromethyl) 4-methylbenzenesulfonothioate and Se-(trifluoromethyl) 4-methylbenzenesulfonoselenoate under visible light irradiation. This transformation was tolerated with a wide range of functional groups and provided an alternative and green strategy for the synthesis of trifluoromethylthioesters and trifluoromethylselenoesters

Synthesis of Biobased Poly(butylene Furandicarboxylate) Containing Polysulfone with Excellent Thermal Resistance Properties

A synthetic biopolymer derived from furandicarboxylic acid monomer and hydroxyethyl-terminated poly­(ether sulfone) is presented. The synthesis involves 4,4′-dichlorodiphenyl sulfone and 4,4-dihydroxydiphenyl sulfone, resulting in poly­(butylene furandicarboxylate)-poly­(ether sulfone) copolyesters (PBFES) through melt polycondensation with titanium-catalyzed polymerization. This facile method yields segmented polyesters incorporating polysulfone, creating a versatile group of high-temperature thermoplastics with adjustable thermomechanical properties. The PBFES copolyesters demonstrate an impressive tensile modulus of 2830 MPa and a tensile strength of 84 MPa for PBFES55. Additionally, the poly­(ether sulfone) unit imparts a relatively high glass transition temperature (Tg), ranging from 36.6 °C for poly­(butylene 2,5-furandicarboxylate) to 112.3 °C for PBFES62. Moreover, the complete amorphous film of PBFES exhibits excellent transparency and solvent resistance, making it suitable for applications, such as food packaging materials

Direct Oxidation of Methanol to Polyoxymethylene Dimethyl Ethers over FeMo@HZSM‑5 Core–Shell Catalyst

Direct oxidation of methanol to polyoxymethylene dimethyl ethers (PODEn) with longer C–O chains faces a challenge due to difficult matching of active sites. Herein, a core–shell catalyst composed of an iron molybdenum core and a zeolite shell has been designed, successfully realizing methanol oxidation to PODEn. The PODE2–6 selectivity reaches 41.0% at 85.6% methanol conversion over the FeMo@HZSM-5 catalyst. Combined with the designed experiments and characterizations, the special core–shell structure and the synergy between acid sites with different strengths and redox sites are the pivotal factors for promoting the chain growth of the C–O bond

DataSheet1_CO2 Hydrogenation to Olefin-Rich Hydrocarbons Over Fe-Cu Bimetallic Catalysts: An Investigation of Fe-Cu Interaction and Surface Species.PDF

Previously, we reported a strong Fe-Cu synergy in CO2 hydrogenation to olefin-rich C2+ hydrocarbons over the γ-Al2O3 supported bimetallic Fe-Cu catalysts. In this work, we aimed to clarify such a synergy by investigating the catalyst structure, Fe-Cu interaction, and catalyst surface properties through a series of characterizations. H2-TPR results showed that the addition of Cu made both Fe and Cu easier to reduce via the strong interaction between Fe and Cu. It was further confirmed by X-ray absorption spectroscopy (XAS) and TEM, which showed the presence of metallic Fe and Fe-Cu alloy phases in the reduced Fe-Cu(0.17) catalyst induced by Cu addition. By correlating TPD results with the reaction performance, we found that the addition of Cu enhanced both the moderately and strongly adsorbed H2 and CO2 species, consequently enhanced CO2 conversion and C2+ selectivity. Adding K increased the adsorbed-CO2/adsorbed-H2 ratio by greatly enhancing the moderately and strongly adsorbed CO2 and slightly suppressing the moderately and strongly adsorbed H2, resulting in a significantly increased O/P ratio in the produced hydrocarbons. The product distribution analysis and in situ DRIFTS suggested that CO2 hydrogenation over the Fe-Cu catalyst involved both an indirect route with CO as the primary product and a direct route to higher hydrocarbons.</p

Discovering Inherent Characteristics of Polyethylenimine-Functionalized Porous Materials for CO₂ Capture

CO2 capture is vital for addressing greenhouse gas (GHG)-based environmental issues worldwide. Amine-polymer/silica sorbents have been extensively studied for CO2 capture, but the fundamental understandings of polyethylenimine (PEI) loading effect, thermal effect, and CO2 sorption behavior are still lacking. Small-angle neutron scattering (SANS) offers promising opportunities for characterizing CO2 sorption behavior of PEI-functionalized SBA-15. Herein, in situ SANS has been used to investigate not only PEI loading distribution but also PEI thermal swelling and temperature-dependent CO2 sorption behavior of PEI-functionalized SBA-15. The results indicate that PEI could disperse on the mesopore surface for the sample with low PEI loading, while for the sample with high PEI loading, PEI could not only disperse on the mesopore surface but also partially fill in the mesopore as plugs. The sample with high PEI loading shows a two-stage swelling of PEI with increasing temperature from 25 to 120 °C in vacuum, in which the size of the intramolecular voids between PEI chains has no change from 25 to 75 °C but expands from 75 to 120 °C, whereas only a subtle swelling is observed up to 120 °C for the sample with low PEI loading. Besides the fact that in situ SANS successfully detects physisorbed CO2 on the mesopore surface and chemisorbed CO2 by the amine groups simultaneously: (1) the amount of physisorbed CO2 increases with increasing pressure but decreases with increasing temperature, and (2) the amount of chemisorbed CO2 has a trend of VCO2 (75 °C) > VCO2 (120 °C) > VCO2 (25 °C). The thermal swelling of PEI causes dilation of intramolecular voids and thus increases the accessibility of chemisorption sites, resulting in higher CO2 sorption capacity. Therefore, temperature and PEI swelling are essential factors for kinetic and thermodynamic controls of CO2 capture in amine-functionalized porous adsorbents