Highly selective conversion of CO2 to methanol on the CuZnO–ZrO2 solid solution with the assistance of plasma

CuZnO–ZrO₂–C was prepared by a co-precipitation method. For comparison, CuZnO–ZrO₂–PC and CuZnO–ZrO₂–CP were prepared by glow discharge plasma. The catalysts were characterized via the XRD, N₂ adsorption–desorption, TEM, SEM, EDS, XPS, CO₂-TPD and H₂-TPR techniques. The catalysts were comparatively investigated for CO₂ conversion and methanol selectivity in a fixed-bed reactor under the condition of 2 MPa, 250 °C, H₂/CO₂ = 3/1 and GHSV = 12 000 mL g⁻¹ h⁻¹. The results showed that the activities of the catalysts increased in the order of CuZnO–ZrO₂–PC > CuZnO–ZrO₂–CP > CuZnO–ZrO₂–C. Moreover, the CO₂ conversion of CuZnO–ZrO₂–C increased by 38.9% via treatment with glow discharge plasma. The results are well explained based on the CO₂-TPD and H₂-TPR characterizations of the catalysts.

CuZnO–ZrO₂–C was prepared by a co-precipitation method.     

Template-free synthesis of monolithic carbon xerogels with hierarchical porosity from resorcinol and formaldehyde via hydrothermal reaction

Monolithic carbon xerogels with hierarchical porosity were prepared from resorcinol (R) and formaldehyde (F) via a base-catalysed hydrothermal polycondensation reaction, without a template and supercritical drying. First, an aqueous solution of resorcinol, formaldehyde and sodium carbonate was prepared by varying R/W (25–45) and R/C (1–10k) ratios to produce monolithic RF gels. The reaction was carried out in a pressurized Teflon mould at 100 °C for 6 h to give a co-continuous pore structure via spinodal decomposition and a tenacious gel to avoid supercritical drying. Next, the RF gels were dried for 42 h at 60 °C and another 6 h at 100 °C to produce RF xerogels without cracks, followed by pyrolysis in a tube furnace at 900 °C for 2 h under N₂ flow, and then activation at 1000 °C for 2, 4 or 6 h under CO₂ flow. Finally, the carbon xerogels were characterized by SEM and N₂ adsorption–desorption measurements. Monolithic RF gels were obtained from all combinations of R/W and R/C, but the gels from R/W = 45 exhibited a co-continuous large-pore structure, providing a specific surface area (SSA) of ∼650 m² g⁻¹, which increased to 3311 m² g⁻¹ (for R/C = 10k) at 6 h of CO₂ activation without exhibiting cracks. N₂ isotherms demonstrated that micro- and meso-pores were introduced via activation, forming hierarchical porosity in combination with large pores from spinodal decomposition without using a template.

Monolithic porous carbon with hierarchical porosity via a one-step template-free hydrothermal polycondensation reaction with resorcinol and formaldehyde.     

Water adsorbancy of high surface area layered double hydroxides (AMO-LDHs)

Understanding the water adsorbancy of highly dispersed, high surface area layered double hydroxide (LDH) is of great importance as it directly relates to their hydrophobicity and subsequent use as additives in LDH-polymer nanocomposites. In this study, we have investigated the water vapour uptake response of highly dispersed, high surface area aqueous miscible organic-LDHs (AMO-LDHs) in two relative humidity atmospheres (RH99 and RH60) at 20 °C. We observed that AMO-Mg₃Al–CO₃ and AMO-Zn₂MgAl–CO₃ exhibited very high water vapour uptake in an RH99 atmosphere at 20 °C (56 wt% and 20 wt% for Mg₃Al–CO₃ and Zn₂MgAl–CO₃ LDH respectively after 120 h). The crystallinity in both ab-plane and c-axis of the LDHs increased with increasing exposure uptake. The water vapour adsorption capacity of the AMO-LDHs can be dramatically reduced by treatment with stearic acid.

Water adsorbancy of high surface area layered double hydroxides in different relative humidity was investigated. High water inhibition can be achieved via surface modification of LDHs with stearic acid via acid–base reaction.     

MOF-5 derived carbon as material for CO2 absorption

In our study we prepared MOF-5 derived carbon to reveal the thermodynamics of CO₂ absorption processes in great detail. Porous carbon material was prepared from a metal–organic framework (MOF-5) via carbonization at 1000 °C. The obtained structure consists only of carbon and exhibits a BET specific surface area, total pore volume and micropore volume of 1884 m² g⁻¹, 1.84 cm³ g⁻¹ and 0.59 cm³ g⁻¹, respectively. Structural analysis allowed the assumption that this material is an ideal candidate for efficient CO₂ absorption. The CO₂ uptake was 2.43 mmol g⁻¹ at 25 °C and 1 bar. Additionally, the absorption over a wide range of temperatures (25, 40, 60, 80 and 100 °C) and pressures (in range of 0–40 bar) was investigated. It is shown that the CO₂ absorption isotherm fits a multitemperature Sips model. The calculated Sips equation parameters allows the isosteric heat of adsorption to be obtained. The isosteric heat of adsorption for CO₂ decreased substantially with an increase in surface coverage by gas molecules. This indicates a negligible intermolecular interaction between CO₂ molecules. A decrease in the isosteric heat of adsorption with surface coverage is a result of the disappearance of favourable adsorption sites.

In our study we prepared MOF-5 derived carbon to reveal the thermodynamics of CO₂ absorption processes in great detail.     

Cu catalysts supported on CaO/MgO for glycerol conversion to lactic acid in alkaline medium employing a continuous flow reaction system

The production of lactic acid (LA) from glycerol in alkaline medium was investigated using Cu catalysts supported on CaO, MgO and xCaO/MgO (x = 5, 10, 15 wt%), employing a continuous flow reaction system over a period of 30 h. In addition to assessing the effect of the composition of the catalytic support, the influence of the temperature (200–260 °C), NaOH/glycerol molar ratio (0.5–1.5), hydroxide type (NaOH and KOH), as well as the influence of concentration (10 and 20 vol%) and purity of glycerol was investigated. The catalysts were prepared by a wet impregnation method and characterized by XRF, XRD, N₂ adsorption–desorption, H₂-TPR and CO₂-TPD. The catalytic tests showed that the use of NaOH results in higher yields to LA. Cu catalysts supported on xCaO/MgO exhibited better catalytic performance than the CuCa and CuMg catalysts. The LA yield increases with the increase of the reaction temperature from 200 to 240 °C, and then decreases with a subsequent increase to 260 °C. NaOH/glycerol molar ratios greater than 1.25 are not necessary, since high yield to LA (96.9%) was obtained in the catalytic test performed using a molar ratio of 1.25. The catalysts showed excellent stability without evidence of deactivation over the evaluated period.

The production of lactic acid (LA) from glycerol in alkaline medium was investigated using Cu catalysts supported on CaO, MgO and xCaO/MgO (x = 5, 10, 15 wt%), employing a continuous flow reaction system over a period of 30 h.     

Zinc(ii) and cadmium(ii) amorphous metal–organic frameworks (aMOFs): study of activation process and high-pressure adsorption of greenhouse gases

Two novel amorphous metal–organic frameworks (aMOFs) with chemical composition {[Zn₂(MTA)]·4H₂O·3DMF}_n (UPJS-13) and {[Cd₂(MTA)]·5H₂O·4DMF}_n (UPJS-14) built from Zn(ii) and Cd(ii) ions and extended tetrahedral tetraazo-tetracarboxylic acid (H₄MTA) as a linker were prepared and characterised. Nitrogen adsorption measurements were performed on as-synthesized (AS), ethanol exchanged (EX) and freeze-dried (FD) materials at different activation temperatures of 60, 80, 100, 120, 150 and 200 °C to obtain the best textural properties. The largest surface areas of 830 m² g⁻¹ for UPJS-13 (FD) and 1057 m² g⁻¹ for UPJS-14 (FD) were calculated from the nitrogen adsorption isotherms for freeze-dried materials activated at mild activation temperature (80 °C). Subsequently, the prepared compounds were tested as adsorbents of greenhouse gases, carbon dioxide and methane, measured at high pressures. The maximal adsorption capacities were 30.01 wt% CO₂ and 4.84 wt% CH₄ for UPJS-13 (FD) and 24.56 wt% CO₂ and 6.38 wt% CH₄ for UPJS-14 (FD) at 20 bar and 30 °C.

Two novel amorphous metal–organic frameworks UPJS-13 and UPJS-14, constructed of Zn(ii)/Cd(ii) ions and extended tetrahedral linker were prepared, characterised and applied as adsorbents for carbon dioxide and methane.     

An amine-bifunctionalization strategy with Beta/KIT-6 composite as a support for CO2 adsorbent preparation

An amine-bifunctionalized composite strategy was used to fabricate grafted-impregnated micro-/mesoporous composites for carbon dioxide capture. The micro-/mesoporous Beta/KIT-6 (BK) composite containing a high-silica zeolite with a three-dimensional twelve-membered ring crossing channel system and cubic structural silica was used as a support, and 3-aminopropyltrimethoxysilane (APTS) and tetraethylenepentamine (TEPA) were used as the grafted and impregnated components, respectively. The amine efficiency, adsorption kinetics, thermal stability, regeneration performance, and the effects of impregnated amine loadings (30–60%) and temperatures (40–90 °C) on the CO₂ adsorption performance were investigated using a thermal gravimetric analyzer (TGA) in the mixed gases (15 vol% CO₂ and 85 vol% N₂). At 60 °C, the bifunctionalized Beta/KIT-6 (1 mL APTS g⁻¹ BK) displayed the highest CO₂ adsorption capacity of 5.12 mmol g⁻¹ at a TEPA loading of 50%. The kinetic model fitting results showed that the CO₂ adsorption process was a combination of physical and chemical adsorption, wherein the chemical adsorption is dominant. After five adsorption/desorption cycle regenerations, the saturated adsorption capacity of the composite material was 4.86 mmol g⁻¹, which was only 5.1% lower than the original adsorption capacity. The composites demonstrated excellent CO₂ adsorption performance, indicating the promising future of these adsorbents for CO₂ capture from actual flue gas after desulfurization.

CO₂ adsorption curves of A-BK-TEPA-50 at 40, 60, 75, 80 and 90 °C.     

Polyetherimide hollow fiber membranes for CO2 absorption and stripping in membrane contactor application

Porous asymmetric polyetherimide (PEI) hollow fiber membranes with various non-solvent additives, e.g. lithium chloride, methanol and phosphoric acid (PA) were prepared for CO₂ absorption and stripping process in a membrane contractor. The PEI membranes were characterized via gas permeation, liquid entry pressure of water (LEPw), contact angle and field emission scanning electronic microscopy analysis. The CO₂ absorption and stripping performance was evaluated via the membrane contactor system. Addition of non-solvent additives increased the LEPw and membrane porosity of the PEI membrane with the formation of various membrane microstructures and contact angles. Absorption test was performed at 40 °C showed that the PEI–PA membrane produced the highest absorption flux of 2.7 × 10⁻² mol m⁻² s⁻¹ at 0.85 m s⁻¹ of liquid velocity. Further testing on PEI–PA membrane was conducted on CO₂ stripping at 60 °C, 70 °C to 80 °C and the results indicated that the stripping flux was lower compared to the absorption flux. Stripping tests at 80 °C produced the highest stripping flux which might due to the increase in equilibrium partial pressure of CO₂ in the liquid absorbent. Modification of PEI membrane via incorporation of additive can enhanced the performance of a membrane contactor via increasing the absorption and stripping flux.

Porous asymmetric polyetherimide (PEI) hollow fiber membranes with various non-solvent additives, e.g. lithium chloride, methanol and phosphoric acid (PA) were prepared for a CO₂ absorption and stripping process in a membrane contractor.     

Experimental study on light volatile products from thermal decomposition of lignin monomer model compounds: effect of temperature,residence time and methoxyl group

In order to investigate the effects of temperature, residence time (RT) and methoxyl (OCH₃) on the product distribution and vapor phase reactions during pyrolysis of complex solid fuels, three model phenolic representatives, phenol, guaiacol and syringol, were pyrolyzed at a residence time of 0.7 s, over a temperature range of 400 °C–950 °C, and at temperatures of 650 °C and 750 °C, in a RT region of 0.1 s–4.2 s. Increasing yields of CO and C₁–C₅ light hydrocarbons (LHs) with RT at 650 °C and 750 °C indicated that ring-reduction/CO elimination of phenolic compounds happened at 650 °C, and dramatically at 750 °C. The addition of OCH₃ affects the product distribution and ring-reduction pathways: C₅ LHs from phenol, C₂ LHs, C₄ LHs and C₅ LHs from guaiacol, and C₁–C₂ LHs from syringol. CO₂ yields increase with the addition of OCH₃. CO₂ was formed via benzoyl and a four-membered ring, which would compete with the CO formation. The addition of OCH₃ promotes the formation of coke and tar. The decomposition pathways are discussed, based on the experimental data, focusing on ring-reduction reactions and the formation of CO/CO₂ and C₁–C₅ LHs.

Effects of temperature, residence time and methoxyl on the decomposition of phenol, guaiacol and syringol, were investigated. Thermal decomposition pathways of the three model compounds were discussed based on ring reduction/CO elimination reactions.     

Single-walled carbon nanotubes/lithium borohydride composites for hydrogen storage: role of in situ formed LiB(OH)4, Li2CO3 and LiBO2 by oxidation and nitrogen annealing

Lithium Borohydride (LiBH₄), from the family of complex hydrides has received much attention as a potential hydrogen storage material due to its high hydrogen energy densities in terms of weight (18.5 wt%) and volume (121 kg H₂ per mol). However, utilization of LiBH₄ as a hydrogen carrier in off- or on-board applications is hindered by its unfavorable thermodynamics and low stability in air. In this study, we have synthesized an air stable SWCNT@LiBH₄ composite using a facile ultrasonication assisted impregnation method followed by oxidation at 300 °C under ambient conditions (SWLiB-A). Further, part of the oxidized sample is treated at 500 °C under nitrogen atmosphere (SWLiB-N). Upon oxidation in air, the in situ formation of lithium borate hydroxide (LiB(OH)₄) and lithium carbonate (Li₂CO₃) on the surface of the composite (SWLiB@LiBH₄) is observed. But in the case of SWLiB-N, the surface hydroxyl groups [OH₄]⁻ completely vanished leaving porous LiBH₄ with SWCNT, LiBO₂ and Li₂CO₃ phases. Hydrogen adsorption/desorption experiments carried out at 100 °C under 5 bar H₂ pressure showed the highest hydrogen adsorption capacity of 4.0 wt% for SWLiB-A and 4.3 wt% for SWLiB-N composites in the desorption temperature range of 153–368 °C and 108–433 °C respectively. The observed storage capacity of SWLiB-A is due to the H⁺ and H⁻ coupling between in situ formed Li⁺[B(OH)₄]⁻, Li²⁺[CO₃]⁻ and Li⁺[BH₄]⁻. Whereas in SWLiB-N, the presence of positively charged Li and B atoms and LiBO₂ acts as a catalyst which resulted in reduced de-hydrogenation temperature (108 °C) as compared to bulk LiBH₄. Moreover, it is inferred that the formation of intermediate phases such as Li⁺[B(OH)₄]⁻, Li²⁺[CO₃]⁻ (SWLiB-A) and Li⁺[BO₂]⁻ (SWLiB-N) on the surface of the composites not only stabilizes the composite under ambient conditions but also resulted in enhanced de- and re-hydrogenation kinetics through catalytic effects. Further, these intermediates also act as a barrier for the loss of boron and lithium through diborane release from the composites upon dehydrogenation. Furthermore, the role of in situ formed intermediates such as LiB(OH)₄, Li₂CO₃ and LiBO₂ on the stability of the composite under ambient conditions and the hydrogen storage properties of the SWCNT@LiBH₄ composite are reported for the first time.

In situ formed Li⁺[B(OH)₄]⁻, Li²⁺[CO₃]⁻ & Li⁺[BO₂]⁻ on the surface of SWCNT@LiBH₄ not only stabilizes the composites in ambient conditions but also enhanced the de- and re-hydrogenation kinetics of the composites through catalytic effect.     

Barium promoted Ni/Sm2O3 catalysts for enhanced CO2 methanation

Low temperature CO₂ methanation is a favorable pathway to achieve high selectivity to methane while increasing the stability of the catalysts. A Ba promoted Ni/Sm₂O₃ catalyst was investigated for CO₂ methanation at atmospheric pressure with the temperature ranging from 200–450 °C. 5Ni–5Ba/Sm₂O₃ showed significant enhancement of CO₂ conversion particularly at temperatures ≤ 300 °C compared to Ni/Sm₂O₃. Incorporation of Ba into 5Ni/Sm₂O₃ improved the basicity of the catalysts and transformed the morphology of Sm₂O₃ from random structure into uniform groundnut shape nanoparticles. The uniformity of Sm₂O₃ created interparticle porosity that may be responsible for efficient heat transfer during a long catalytic reaction. Ba is also postulated to catalyze oxygen vacancy formation on Sm₂O₃ under a reducing environment presumably via isomorphic substitution. The disappearance of a high temperature (∼600 °C) reduction peak in H₂-TPR analysis revealed the reducibility of NiO following impregnation with Ba. However, further increasing the Ba loading to 15% formed BaNiO₃–BaNiO_2.36 phases which consequently reduced the activity of the Ni–Ba/Sm₂O₃ catalyst at low temperature. Ni was suggested to segregate from BaNiO₃–BaNiO_2.36 at high temperature thus exhibiting comparable activity with Ni/Sm₂O₃ at 450 °C.

Low temperature CO₂ methanation on 5Ni–5Ba/Sm₂O₃ is a favorable pathway to achieve high selectivity to methane while increasing the stability of the catalysts.     

Promoting dry reforming of methane via bifunctional NiO/dolomite catalysts for production of hydrogen-rich syngas

Extensive effort has been focused on the advancement of an efficient catalyst for CO₂ reforming of CH₄ to achieve optimum catalytic activity together with cost-effectiveness and high resistance to catalyst deactivation. In this study, for the first time, a new catalytic support/catalyst system of bifunctional NiO/dolomite has been synthesized by a wet impregnation method using low-cost materials, and it shows unique performance in terms of amphoteric sites and self-reduction properties. The catalysts were loaded into a continuous micro-reactor equipped with an online GC-TCD system. The reaction was carried out with a gas mixture consisting of CH₄ and CO₂ in the ratio of 1 : 1 flowing 30 ml min⁻¹ at 800 °C for 10 h. The physicochemical properties of the synthesized catalysts were determined by various methods including X-ray diffraction (XRD), N₂ adsorption–desorption, H₂ temperature-programmed reduction (H₂-TPR), temperature-programmed desorption of CO₂ (TPD-CO₂), and temperature-programmed desorption of NH₃ (TPD-NH₃). The highest catalytic performance of the DRM reaction was shown by the 10% NiO/dolomite catalyst (CH₄ & CO₂ conversion, χCH₄; χCO₂ ∼ 98% and H₂ selectivity, S_H2 = 75%; H₂/CO ∼ 1 : 1 respectively). Bifunctional properties of amphoteric sites on the catalyst and self-reduction behaviour of the NiO/dolomite catalyst improved dry reforming of the CH₄ process by enhancing CH₄ and CO₂ conversion without involving a catalyst reduction step, and the catalyst was constantly active for more than 10 h.

Catalytic conversion of methane dry reforming via NiO/Dolomite catalysts.     

Facile synthesis of polyoxometalates tethered to post Fe-BTC frameworks for esterification of free fatty acids to biodiesel

A phosphomolybdic acid (PMA) was sequentially incorporated into highly porous metal–organic frameworks (MOFs, Fe-BTC) by using a facile one-pot synthesis method, and the prepared composite (PMA/Fe-BTC) was employed as an efficient and stable solid acid catalyst for biodiesel production. N₂ adsorption–desorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric (TG) analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization techniques were employed to reveal the structure–performance relationship. The effects of reaction parameters like catalyst amount, reaction time and temperature were further investigated. This solid acid gave good catalytic performance in the esterification of free fatty acids with methanol, which is attributed to large surface area and thermal stability. The PMA/Fe-BTC was successfully reused for up to six cycles and exhibited high stability. From the kinetic study performed at different reaction temperatures (140 °C, 150 °C and 160 °C) E_a = 49.5 kJ mol⁻¹ was obtained. In addition, due to the high activity presented in various esterifications of free fatty acids, this composite catalytic material has immense potential for industrial biodiesel production.

Phosphomolybdic acid was sequentially incorporated into a highly porous metal–organic framework by a one-pot synthesis method, and the prepared composite was used as an efficient and stable solid acid catalyst for biodiesel production.     

Experimental and theoretical study of CO2 adsorption by activated clay using statistical physics modeling

The objective of this paper was to study CO₂ adsorption on activated clay in the framework of geological storage. The activation of clay was characterized via scanning electron microscopy, N₂ adsorption–desorption isotherms, and X-ray diffraction. The adsorption isotherms were generated at different temperatures, namely, 298 K, 323 K, and 353 K. Based on the experimental result, a new model was simulated and interpreted using a multi-layer model with two interaction energies. The physicochemical parameters that described the CO₂ adsorption process were determined by physical statistical formalism. The characteristic parameters of the CO₂ adsorption isotherm such as the number of carbon dioxide molecules per site (n), the receptor site densities (NM), and the energetic parameters were investigated. In addition, the thermodynamic functions that governed the adsorption process such as the internal energy, entropy, and Gibbs free energy were determined by a statistical physics model. Thus, the results showed that CO₂ adsorption on activated clay was spontaneous and exothermic in nature.

The objective of this paper was to study CO₂ adsorption on activated clay in the framework of geological storage.     

The preparation of synthetic graphite materials with hierarchical pores from lignite by one-step impregnation and their characterization as dye absorbents

Herein, synthetic graphite materials with hierarchical pores and large specific surface area were successfully prepared by one-step impregnation with lignite as the carbon source, sulfuric acid (H₂SO₄) as the oxidant, and phosphoric acid (H₃PO₄) as the activator. The microstructural characteristics of synthetic graphite were investigated via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Moreover, the pore parameters were studied by nitrogen adsorption–desorption. The results showed that synthetic graphite had a perfect orderly layered structure with high graphitization degree and a well-developed multistage pore structure with pore sizes ranging from nanometer to micrometer. The specific surface area and pore volume were 415.29 m² g⁻¹ and 0.67 cm³ g⁻¹, respectively. The results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) showed that the impregnation pretreatment provided polar groups containing oxygen to the surfaces. These unique characteristics make synthetic graphite possess good adsorption capacity for dye pollutants (the adsorption rate of the methyl orange solution was 99.9% within 60 min at 50 °C, and the pH value of the solution was 3). The effects of temperature and pH value on the adsorption capacity were studied. The repeatability of the adsorption performance was also tested, and the adsorption rate was 84.6% of the initial adsorption rate after five cycles.

Herein, synthetic graphite materials with hierarchical pores and large specific surface area were prepared by one-step impregnation with lignite as the carbon source, H₂SO₄ as the oxidant, and H₃PO₄ as the activator.     

A series of four novel alkaline earth metal–organic frameworks constructed of Ca(ii), Sr(ii), Ba(ii) ions and tetrahedral MTB linker: structural diversity,stability study and low/high-pressure gas adsorption properties

A series of four novel microporous alkaline earth metal–organic frameworks (AE-MOFs) containing methanetetrabenzoate linker (MTB) with composition {[Ca₄(μ₈-MTB)₂]·2DMF·4H₂O}_n (UPJS-6), {[Ca₄(μ₄-O)(μ₈-MTB)_3/2(H₂O)₄]·4DMF·4H₂O}_n (UPJS-7), {[Sr₃(μ₇-MTB)_3/2]·4DMF·7H₂O}_n (UPJS-8) and {[Ba₃(μ₇-MTB)_3/2(H₂O)₆]·2DMF·4H₂O}_n (UPJS-9) (UPJS = University of Pavol Jozef Safarik) have been successfully prepared and characterized. The framework stability and thermal robustness of prepared materials were investigated using thermogravimetric analysis (TGA) and high-energy powder X-ray diffraction (HE-PXRD). MOFs were tested as adsorbents for different gases at various pressures and temperatures. Nitrogen and argon adsorption showed that the activated samples have moderate BET surface areas: 103 m² g⁻¹ (N₂)/126 m² g⁻¹ (Ar) for UPJS-7′′, 320 m² g⁻¹ (N₂)/358 m² g⁻¹ (Ar) for UPJS-9′′ and UPJS-8′′ adsorbs only a limited amount of N₂ and Ar. It should be noted that all prepared compounds adsorb carbon dioxide with storage capacities ranging from 3.9 to 2.4 wt% at 20 °C and 1 atm, and 16.4–13.5 wt% at 30 °C and 20 bar. Methane adsorption isotherms show no adsorption at low pressures and with increasing pressure the storage capacity increases to 4.0–2.9 wt% of CH₄ at 30 °C and 20 bar. Compounds displayed the highest hydrogen uptake of 3.7–1.8 wt% at −196 °C and 800 Torr among MTB containing MOFs.

Four novel microporous alkaline earth metal–organic frameworks (AE-MOFs) containing methanetetrabenzoate linker (MTB): UPJS-6, UPJS-7, UPJS-8 and UPJS-9 have been successfully prepared, characterized and tested as adsorbents for different gases.     

Ethylene-bridged polysilsesquioxane/hollow silica particle hybrid film for thermal insulation material

Ethylene-bridged polysilsesquioxane (EBPSQ) was prepared by the sol–gel reaction of bis(triethoxysilyl)ethane. The whitish slurry was prepared by mixing EBPSQ and hollow silica particles (HSPs) with a median diameter of 18–65 μm at 80 °C, and it formed a hybrid film by heating at 80 and 120 °C for 1 h at each temperature, then at 200 °C for 20 min. The surface temperatures of EBPSQ films containing 10 wt% and 20 wt% of HSPs (90.2 °C–90.5 °C) were lower than those of EBPSQ films (93.6 °C), when the films on the duralumin plate were heated at 100 °C for 10 min from the bottom of the duralumin plate. The thermal conductivity/heat flux (k/q) obtained from the temperature difference between the surface temperature and bottom temperature of the films and the film thickness also decreased with adding the HSPs. EBPSQ film without HSPs exhibited T⁵_d of 258 °C and T¹⁰_d of 275 °C. However, EBPSQ film containing 20 wt% of HSPs exhibited high thermal stability, and T⁵_d and T¹⁰_d were 299 °C and 315 °C, respectively. Interestingly, T⁵_d and T¹⁰_d of the hybrid films increased with an increase in the number of HSPs. Overall, it was shown that HSPs could improve the thermal insulation properties and thermal stability.

Ethylene-bridged polysilsesquioxane/hollow silica particle hybrid films were prepared by the sol–gel reaction. The hybrid film containing hollow silica particles exhibited good thermal insulation properties and thermal stability.     

Hierarchically ordered macro–mesoporous anatase TiO2 prepared by pearl oyster shell and triblock copolymer dual templates for high photocatalytic activity

Hierarchically ordered macro–mesoporous anatase TiO₂ is prepared by combining the supramolecular-templating self-assembly of amphiphilic triblock copolymer P123 with a natural pearl oyster shell in a hard-templating process by a facile sol–gel reaction. The obtained materials are characterized by Raman spectroscopy, X-ray diffraction, N₂ adsorption–desorption analysis, scanning electron microscopy, and transmission electron microscopy. The results demonstrate that all TiO₂ materials obtained after calcination at various temperatures are in the anatase phase, and interestingly the resultant ordered structure of both macropores and mesopores are well-preserved after calcination at 350 °C or 450 °C, with the walls of macropores composed of ordered mesopores. However, upon calcination at 550 °C or 650 °C, while the ordered macroporous structures remain well-preserved, the mesoporous structures collapse. The photocatalytic activities of the resulting TiO₂ materials are also evaluated by photodegradation of rhodamine B under UV light irradiation. The prepared TiO₂ calcined at 450 °C shows the highest photocatalytic activity.

Hierarchically ordered macro–mesoporous anatase TiO₂ with photocatalytic activity was prepared using triblock copolymer P123 and natural pearl oyster shell as dual templates.     

Performance of gamma-Al2O3 decorated with potassium salts in the removal of CS2 from C5 cracked distillate

Deep desulfurization is a key process for the production of high value-added products from C₅ distillates. In this work, different potassium salt modified gamma-Al₂O₃ adsorbents were prepared by an incipient-wetness impregnation method and characterized by N₂ adsorption–desorption, SEM-EDS, TEM, CO₂-TPD, XRD, FT-IR, and IC. The C₅ distillate with a 1200 μg mL⁻¹ sulfur content is desulfurized to less than 10 μg mL⁻¹ within 24 hours by the static adsorption method. For the desulfurization in the fix-bed reactor, the breakthrough sulfur capacity of K₂CO₃-decorated gamma-Al₂O₃ reaches 0.76 wt% under the optimized conditions, viz., at 30 °C, with a sulfur content of 50 μg mL⁻¹ in the raw oil, and a liquid hourly space velocity of 1 h⁻¹. The desulfurization activity of the exhausted adsorbent can be recovered after regeneration. Selective adsorption of CS₂ includes three processes: adsorption, hydrolysis, and oxidation. CS₂ is first adsorbed on the adsorbent and hydrolyzed to form H₂S. H₂S is further oxidized to form S/SO₄²⁻, and then deposits on the surface of the adsorbent. Adsorption, hydrolysis, and oxidation all play essential roles in the removal process of CS₂.

Deep desulfurization is a key process for the production of high value-added products from C₅ distillates.     

Treatment of phenol by catalytic wet air oxidation: a comparative study of copper and nickel supported on γ-alumina,ceria and γ-alumina–ceria

Cu, Ni, CuO and NiO catalysts, prepared by wet impregnation with urea and supported on γ-Al₂O₃, CeO₂, and Al₂O₃–CeO₂, were evaluated for Catalytic Wet Air Oxidation (CWAO) of phenol in a batch reactor under a milder condition (120 °C and 10 bar O₂). The synthesized samples, at their calcined and/or their reduced form, were characterized by XRD, H₂-TPR, N₂ adsorption–desorption, SEM-EDS and DR-UV-Vis to explain the differences observed in their catalytic activity towards the studied reaction. The influence of the support on the efficiency of CWAO of phenol at 120 °C and 10 bar of pure oxygen has been examined and compared over nickel and copper species. The SEM-EDS results reveal that the spherical crystalline Cu and Ni were successfully deposited on the surface of γ-Al₂O₃, CeO₂, Al₂O₃–CeO₂ within 16–90 nm and that they were highly homogeneously dispersed. It was found that catalysts prepared from impregnation solutions of Cu(NO₃)₂·3H₂O and Ni(NO₃)₂·6H₂O with urea addition had different textural characteristics and degrees of dispersion of Cu and Ni species. The urea addition in the traditional wet impregnation method was essential to improve the reducibility and degree of dispersion in Ni, and to a lesser extent, in Cu. According to the characterization analysis of H₂-TPR and UV-VIS RD a structure–activity relationship can be determined. The chemical oxygen demand (COD) and GC analyses confirmed the effect of calcined and reduced species for Cu and Ni applied to the catalytic oxidation of phenol, showing their significant impact in the final performance of the catalyst.

Influence of the calcination and reduction treatment effects used to activate catalysts on the global catalytic performance on phenol oxidation over different supports.