Decrease In BET Surface Area Research Articles

Developing Ni/SAPO-11 deoxygenation catalysts using yttrium modified SAPO-11 prepared by rice husk ash

To suppress the aggregation of metallic sites, a novel Ni/SAPO-Y deoxygenation catalyst is developed using yttrium modified SAPO-11 prepared by rice husk ash (RHA). Yttrium oxide interacts with silicon atoms to form Si-O-Y bonds, which enhance the bond strength of Si-O bonds and function as space barriers to inhibit the aggregation of Ni0 sites. In the catalytic evaluation, Ni/SAPO-Y exhibits a higher conversion due to an excellent dispersion of Ni0 sites. It is favorable for the decarboxylation and/ or decarbonylation of stearic acids on fine Ni0 particles with a low consumption of H2. In the catalyst cycle experiments, aggregation of Ni0 sites results in the deactivation of regenerated catalysts due to the removal of aluminium hydroxyl groups and decrease of BET surface area. A high acid retention of regenerated catalysts provide excellent isomerization activity (i.e., a yield for iso-paraffin (8.5-10.5%)). Besides the excellent performance of developed Ni/SAPO-Y catalysts, the current research proposes a disposal method for the agricultural waste rice husk.

Important role of pore-filling mechanism in separating naproxen from water by micro-mesoporous carbonaceous material.

Commercial micro-mesoporous carbonaceous material (MCM; 56.8% mesopores) was applied for investigating the removal phenomenon of naproxen drug in aqueous solutions through batch adsorption experiments. Results demonstrated that the adsorption capacity of MCM to naproxen was slightly affected by different pHeq (2.0-11) and ionic strength (0-1M NaCl). Adsorption kinetics, isotherms, thermodynamics, and mechanisms were evaluated at pH7.0. Adsorption kinetics indicated the rate constants for adsorption (0.2 × 10-3 L/(mg × min) and desorption (0.076/min) and the adsorption equilibrium constant (2.6 × 10-3 L/mg). Adsorption isotherm showed that MCM exhibited a high-affinity adsorption capacity to naproxen (even at low concentrations) and its Langmuir maximum adsorption capacity (Qmax ) was 252.7mg/g at 25°C. Adsorption thermodynamics proved that the adsorption process was endothermic and physisorption (ΔH° = 9.66 kJ/mol). The analysis result of pore size distribution demonstrated that the internal pore structure of MCM was appropriate for adsorbing naproxen molecules. Pore-filing mechanism (pore diffusion phenomenon) was confirmed by a considerable decrease in BET-surface area (585 m2 /g) and total pore volume (0.417 cm3 /g) of MCM after adsorbing naproxen (~1000 mg/L and pH7.0) at 5min (341 and 0.256), 60 min (191 and 0.205), 120 min (183 and 0.193), 360 min (144 and 0.175), and 24 h (71.6m2 /g and 0.123 cm3 /g, respectively). The pore diffusion occurred rapidly (even at the initial adsorption period of 5min). The FTIR technique was applied to identify the existence of C-H···π and n-π interaction. π-π interaction (evaluated through ID /IG ratio and C=C band) played a minor contribution in adsorption mechanisms. The ID /IG ratio (determined by the Raman technique) of MCM before adsorption (1.195) was similar to that after adsorption (1.190), and the wavenumber (C=C band; its FTIR spectrum) slightly shifted from 1638 to 1634 cm-1 after adsorption. A decrease in the Qmax value of MCM from 249 to 217 (H2 O2 -oxidized MCM) or to 224 mg/g (HNO3 -oxidized MCM) confirmed the presence ofπ-π interaction. Electrostatic attraction was a minor contribution. MCM can serve as a promising material for removing naproxen from water environment through a pore-filling mechanism. PRACTITIONER POINTS: Pore-filling mechanism was proposed by comparing textural properties of MCM before and after adsorbing naproxen. C-H···π and n-π interactions were identified via FTIR technique. π-π interaction was observed by FTIR and Raman techniques. Oxidation of MCM with HNO3 or H2 O2 was a helpful method to explore π-π interaction. Electrostatic attraction was explained through studies: effects of pH and NaCl along with desorption.

Photocatalytic degradation of gaseous pollutants on nanostructured TiO2 films of various thickness and surface area

This work deals with the preparation of TiO2 nanoparticulate layers of various mass (0.05 mg/cm2 to 2 mg/cm2) from three commercial nanopowder materials, P90, P25 and CG 300, their characterisation (profilometry, BET and SEM) and evaluation of their photocatalytic activity in the gaseous phase in a flow-through photoreactor according to the ISO standard (ISO 22197-2). Hexane was chosen as a single model pollutant and a mixture of four compounds, namely acetaldehyde, acetone, heptane and toluene was used for the evaluation of the efficiency of simultaneous removal of several pollutants. A linear dependence between the layer mass and the layer thickness for all materials was found. Up to a layer mass 0.5 mg/cm2, the immobilisation P90 and P25 powder did not result in a decrease in BET surface area, whereas with an increase in layer mass to 1 mg/cm2, a decrease of the BET surface was observed, being more significant in the case of P90. The photocatalytic conversion of hexane was comparable for all immobilised powders up to a layer mass of 0.5 mg/cm2. For higher layer mass, the photocatalytic conversion of hexane on P25 and P90 differ; the latter achieved about 30% higher conversion. In the case of the simultaneous degradation of four compounds, acetaldehyde was degraded best, followed by acetone and toluene; the least degraded compound was heptane. The measurement of released CO2 revealed that 90% of degraded hexane was mineralised to CO2 and water while for a mixture of 4 VOCs, the level of mineralisation was 83%.Graphical abstract

Tuning of Microenvironment in Covalent Organic Framework via Fluorination Strategy promotes Selective CO2 Capture.

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF, respectively, to demonstrate their relative effect on CO2 adsorption capacity and also CO2 /N2 selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m2 g-1 , total pore volume 0.3647 ccg-1 ), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m2 g-1 , total pore volume 0.2978 ccg-1 ). This fact leads to an enormous decrease in the CO2 adsorption capacity and CO2 /N2 selectivity of TF-COF, though it shows stronger affinity towards CO2 with a Qst of 37.76 KJ/mol. The more CO2 adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF. Further, PD-COF exhibited CO2 /N2 selectivity of 16.8, higher than that of TF-COF (CO2 /N2 selectivity 13.4).

Mechanism of thermally activated sodium persulfate–biochar skeleton treatment to improve the dewaterability of waste activated sludge

Sludge dewatering is a necessary process in the disposal of waste activated sludge (WAS). In this study, thermally activated sodium persulfate–biochar skeleton pretreatment was performed to improve the dewaterability of sludge, and its internal mechanism was systematically elucidated. The experimental results showed that, under optimal operating conditions, the water content of WAS could be reduced from 89.7% to 61.3% of the raw sludge. Under these conditions, the capillary suction time and specific resistance to filtration were roughly 23.23% and 59.57% of those in the raw sludge, respectively. This study proposes a relationship between organic matter migration and sludge physical structure that explains the dewaterability improvement mechanism. Separate thermal treatment caused organic matter such as proteins, polysaccharides, and humic substances to dissolve, releasing their bound water. Simultaneously, changes in the surface structure (pore size reductions and BET surface area increases) deteriorated the dewaterability of WAS. The reactive oxygen species generated by the thermally activated sodium persulfate further mineralized the organic matter, simplifying the floc surface structure (pore size increases and BET surface area decreases) and finally improving the dewaterability. Under these conditions, the addition of biochar increased the pore size, and further improved sludge dewaterability.

Friedlander condensation reaction catalysed by hafnium-based metal-organic framework

Heterogeneous catalysis using metal-organic frameworks (MOFs) is one of the attractive fields in recent years because MOFs offer tuneable properties and a broad range of active sites. In this context, synthesis and characterization of UiO-66(Hf)-(NHCOMe)2 (1) and its activated form (1′) are reported. The catalytic behavior of 1′ was investigated in the Friedlander condensation between 2-aminoacetophenone with acetylacetone under mild reaction conditions. The reaction between 2-aminoacetophenone and acetylacetone in the presence of 1′ afforded a quantitative yield of the desired product. On the other hand, the stability of 1′ was also examined by reusing the solid catalyst and characterizing the recovered solid catalyst by powder XRD, FESEM, 1H NMR, 13C NMR, ATR-IR and BET methods. These combined data indicate that the solid catalyst undergoes a structural change by losing its catalytic activity in the first reuse and becomes deactivated. Although no significant changes were observed between the fresh and the recovered solid by powder XRD, FESEM, 1H NMR, 13C NMR, ATR-IR, the significant decrease in BET surface area of the recovered solid suggests the possible pore blocking by the products.

Encapsulation of NiS and ZnS in analcime nanoparticles as novel nanocomposites for the effective photocatalytic degradation of orange G and methylene blue dyes

ABSTRACT Encapsulation of semiconductor materials in zeolites is one of the important types of composites that have been used as photocatalysts in the degradation of several organic dyes. The high surface area and uniform porous structure of the zeolite particles prevent the coagulation of the catalyst and ensure its stability and dispersion. The strong polarised electrostatic field of zeolites can decrease the energy consumption needed to facilitate the electrons transfer from the valence band to the conduction band. So, in this paper, ethylenediaminetetraacetic acid disodium salt dihydrate was used as an organic template to hydrothermally synthesise analcime nanoparticles. Besides, NiS and ZnS were encapsulated in the analcime nanoparticles as novel photocatalysts for the efficient degradation of orange G and methylene blue dyes. EDX, XRD, FE-SEM, FT-IR, HR-TEM, diffuse reflectance spectrophotometer, and nitrogen gas sorption instruments were used to characterise the novel photocatalysts. The XRD results confirmed that the encapsulation of NiS or ZnS in the analcime nanoparticles led to a decrease in the intensity of the peaks only without affecting their positions. The FE-SEM images confirmed that the encapsulation of NiS or ZnS in the analcime nanoparticles changed the surface of the analcime from small spherical particles into large spherical particles, in addition to the presence of irregular shapes. Besides, the nitrogen gas sorption analyser confirmed that the encapsulation of NiS or ZnS in the analcime nanoparticles led to an increase in average pore radius and total pore volume and a decrease in BET surface area. The percentage of photocatalytic degradation of orange G dye using NiS/analcime and ZnS/analcime composites is 63.60 and 70.50%, respectively. The percentage of photocatalytic degradation of methylene blue dye using NiS/analcime and ZnS/analcime composites is 88.76 and 98.31%, respectively.

Recycle of waste activated coke as an efficient sorbent for Hg0 removal from coal-fired flue gas

The desulfurized activated coke was recycled through thermal regeneration to recover Hg0 from coal-fired flue gas. And the thermal treated activated coke was also prepared for comparison. BET, acid-base titration, XPS and O2-TPD characterizations were performed to identify the structural and chemical properties. Although possessing decreased BET surface area and enlarged pore diameter after thermal treatment, AC-400 exhibited the enhanced Hg0 removal performance due to the generation of oxygen functional groups, while the treatment at 900 °C resulted in the decomposition of surface active oxygen species. Besides, not only the strengthened promotion on the formation of carbonyl and ester groups, but also the deposition of SO42− during regeneration should be responsible for the superior activity of regenerated desulfurized activated coke (RAC) for Hg0 removal. Besides, O2 addition could weaken the competition between NO/SO2 and Hg0, and facilitate the formation of Hg(NO3)2/HgSO4. In combination with Hg-TPD, the specific surface area was in closely correlation with the physisorption of Hg0 on activated coke, and the chemisorption, as the predominant mechanism, of Hg0 mainly depended on the surface active oxygen species. Moreover, when reacted at 60 °C, the Hg0 adsorption priority on RAC was as follows: ester ≥ carbonyl ≥ SO42− ≥ physisorption, and the carbonyl was the leading active sites for mercury adsorption.

Core shell Fe3O4@TiO2/silica aerogel nanocomposite; synthesis and study of structural, magnetic and photocatalytic properties

In this work, magnetic Fe3O4@TiO2 nanospheres supported by a mesoporous silica aerogel substrate were synthesized using simple combining procedure of sol-gel and ultrasound assisted reflux technique for photocatalytic activity. The characteristics study of the as-synthesized ternary nanocomposite showed highly dispersion and covering of the Fe3O4@TiO2 nanoparticles on the silica aerogel. The hydrophobic porous silica aerogel was prepared using industrial diatomite earth (DE) as a silica source by a sol-gel procedure under ambient pressure drying. The specifications results of the resulting silica aerogel revealed a fine particulate morphology with an average size of 26 nm, a low density of about 0.85 g/cm3 and a good degree of porosity with a BET surface area of 572 m2/g. In addition, the structural and morphological studies of the prepared Fe3O4@TiO2 also represented the formation of a pure Fe3O4@TiO2 phase with a core shell spherical morphology and an average particle size of 22 nm. The introduction of the Fe3O4@TiO2 on the silica aerogel nanoparticles led to increase the particle size to 38 nm and decrease of BET surface area to 347 m2/g confirming the formation of Fe3O4@TiO2/silica aerogel nanocomposite. The photocatalytic activity of the prepared ternary nanocomposite was also studied for the removal of tetracycline (TC) as an organic pollutant from water under visible light in details.

Silica and Silica-Titania Xerogels Doped with Iron(III) for Total Antioxidant Capacity Determination.

In order to design a sensor material for total antioxidant capacity determination we have prepared silica and silica–titania xerogels doped with iron(III) and modified with 1,10-phenanthroline. Titanium(IV) tetraethoxyde content in the precursors (titanium(IV) tetraethoxyde and tetraethyl orthosilicate) mixtures has been varied from 0 to 12.5% vol. Iron(III) concentrations in sol has been varied from 1 to 100 mM. The increase of titanium(IV) content has led to a decrease in BET surface area and average pore diameter and an increase of micropore surface area and volume, which has resulted in better iron(III) retention in the xerogels. Iron(III), immobilized in the xerogel matrix, retains its ability to form complexes with 1,10-phenanthroline and to be reduced to iron(II). Static capacities for 1,10-phenanthroline have been determined for all the iron(III) doped xerogels (0.207 mmol/g–0.239 mmol/g) and they are not dependent on the iron(III) content. Sensor materials—xerogels doped with iron(III) and modified with 1,10-phenanthroline—have been used for antioxidants (catechol, gallic and ascorbic acids, and sulphite) solid phase spectrophotometric determination. Limits of detection for catechol, gallic and ascorbic acids, and sulphite equal 7.8 × 10−6 M, 5.4 × 10−6 M, 1.2 × 10−5 M, and 3.1 × 10−4 M, respectively. The increase of titanium(IV) content in sensor material has led to an increase of the reaction rate and the sensitivity of determination. Proposed sensor materials have been applied for total antioxidant capacity (in gallic acid equivalents) determination in soft beverages, have demonstrated high stability, and can be stored up to 6 months at room temperature.

Unsaturated Zn–N2–O active sites derived from hydroxyl in graphene oxide and zinc atoms in core shell ZIF-8@ZIF-67 nanocomposites enhanced CO2 adsorption capacity

In order to form strengthened active sites for superior CO2 adsorption on core shell [email protected] nanocomposites, graphene oxide (GO) with oxygen-containing functional groups was used as support to synthesize hybrid adsorbents with unsaturated Zn–N2–O active sites. The results of XPS O 1s and FTIR analysis revealed that the Me–O functional group content in the 0.5 wt% graphene oxide (GO)-supported core shell [email protected] nanocomposite (38.9 at.%) was much higher than that in the 0.5 wt% reduced graphene oxide (RGO)-supported nanocomposite (19.4 at.%). This was because hydroxyl functional groups in the GO formed coordination bonds with zinc atoms in core shell [email protected] XPS N 1s spectra indicated that the incorporation of oxygen-containing functional groups in GO resulted in the transition of binding form from Me–N4 to Me–N2. The CO2 adsorption capacity of GO-supported core shell [email protected] gradually decreased from 2.15 to 1.30 mmol/g as GO weight percentage increased from 0.5 to 4 wt%, which was consistent with the decrease in BET surface area from 1378 to 585 m2/g and increase in peak pore diameter from 7.7 to 8.2 Å. Density functional theory (DFT) calculations demonstrated that unsaturated Zn–N2–O active sites in GO-supported core shell [email protected] nanocomposites resulted in a decreased OC⋯Zn interaction distance from 4.65 (Zn–N4 sites in core shell [email protected]) to 3.46 Å and an increased binding energy from 34.02 to 38.87 kJ/mol. Therefore, 0.5 wt% GO-supported core shell [email protected] nanocomposites exhibited the highest CO2 adsorption capacity of 2.15 mmol/g (at 273 K and 1 bar), 1.34 times higher than that of core-shell [email protected]

Efficient synthesis of magnetic nanoparticle-Musa acuminata peel composite for the adsorption of anionic dye

The impregnation of magnetite (Mt) nanoparticle (NPs) onto Musa acuminata peel (MApe), to form a novel magnetic combo (MApe-Mt) for the adsorption of anionic bromophenol blue (BPB) was studied. The SEM, EDX, BET, XRD, FTIR and TGA were used to characterize the adsorbents. The FTIR showed that the OH and CO groups were the major sites for BPB uptake onto the adsorbent materials. The average Mt crystalline size on MApe-Mt was 21.13 nm. SEM analysis revealed that Mt NPs were agglomerated on the surface of the MApe biosorbent, with an average Mt diameter of 25.97 nm. After Mt impregnation, a decrease in BET surface area (14.89 to 3.80 m2/g) and an increase in pore diameter (2.25–3.11 nm), pore volume (0.0052–0.01418 cm3/g) and pH point of zero charge (6.4–7.2) was obtained. The presence of Pb(II) ions in solution significantly decreased the uptake of BPB onto both MApe (66.1–43.8%) and MApe-Mt (80.3–59.1%), compared to other competing ions (Zn(II), Cd(II), Ni(II)) in the solution. Isotherm modeling showed that the Freundlich model best fitted the adsorption data (R2 > 0.994 and SSE < 0.0013). In addition, maximum monolayer uptake was enhanced from 6.04 to 8.12 mg/g after Mt impregnation. Kinetics were well described by the pseudo-first order and liquid film diffusion models. Thermodynamics revealed a physical, endothermic adsorption of BPB onto the adsorbents, with ΔHo values of 15.87–16.49 kJ/mol, corroborated by high desorption (over 90%) of BPB from the loaded materials. The viability of the prepared adsorbents was also revealed in its reusability for BPB uptake.

The investigation of hydrogenation behavior of furfural over sol–gel prepared Cu/ZrO2 catalysts

Hydrogenation of furfural over sol–gel Cu/ZrO2 catalysts was tested and selectivity to furfuryl alcohol (FA) and 2-methylfuran (MF) was investigated. Cu/ZrO2 catalysts were prepared by sol–gel method. BET, XRD, XPS, and TEM were used for characterization. The hydrogenation reactions were carried out by changing Cu content of the catalyst, the pressure, loading of catalyst, temperature, and time. The maximum 79.8% FA yield was obtained at 180 °C for 5 h under 1 MPa hydrogen pressure in the presence of 12% Cu containing non-noble metal catalysts. The maximum 56.4% MF yield was observed in the presence of 12% Cu containing metal catalysts at 200 °C under 2 MPa for 3 h. The increase in crystallinity of ZrO2 and decrease in BET surface area were observed after fifth use of 12% Cu containing catalyst. Although FA selectivity did not change, furfural conversion decreased from 100% to 58% at fifth reuse.

Synthesis of Pd/C catalyst using formaldehyde reduction method and application for ultrasound assisted transfer hydrogenation of corn oil

The current work focuses on synthesis of Pd/C catalyst initially based on formaldehyde reduction approach followed by detailed investigation into intensification of catalytic transfer hydrogenation (CTH) using ultrasound using the synthesized catalyst. The obtained catalyst was characterized by X-ray diffraction (XRD), BET surface analysis and FT-IR. The XRD characteristic peaks of palladium (Pd) at 2Ɵ angle of 39.5° and 68.1° coupled with a decrease in BET surface area for the obtained catalyst compared to activated carbon confirmed proper metal loading over activated carbon. The subsequent part of the work focused on understanding the effect of different operating parameters in CTH of corn oil to maximize the progress of reaction. Under the established best conditions of ultrasonic power as 120 W, frequency of 24 kHz, 60 °C, 600 rpm, 2% w/w as loading of catalyst, 50 mL as quantum of water, maximum reduction in the iodine value (selected as parameter to monitor the progress of the reaction) was obtained from initial of 124.46 g/100 g of corn oil to 93.61 g/100 g of corn oil. Comparison of the obtained results for ultrasound assisted approach with conventional approach also allowed demonstrating the process intensification aspects of applying ultrasound for catalytic transfer hydrogenation of corn oil.

Insight into SO2 poisoning over Cu-SAPO-18 used for NH3-SCR

Abstract The impact of SO2 poisoning on Cu-SAPO-18 physicochemical properties and its NH3-SCR reaction mechanism was investigated. After exposing Cu-SAPO-18 to SO2+O2 for 40 min, the sulfite and sulfate species were detected on Cu-SAPO-18 surface, which caused a small decrease in BET surface area and micropore volume, the increase in NH3 storage and the deactivation of some isolated Cu2+ sites. These could be interpreted by the slight micropore blocking, interaction between sulfates and NH3 forming new NH4+ species and the formation of Cu-sulfate, respectively. Additionally, it was observed that isolated Cu2+ ions in pear-shaped cavity of AEI structure, which are beneficial to good low-temperature deNOx activity, were more severely poisoned by SO2 than Cu2+ in the double 6-membered ring (D6R). Accordingly, the NH3-SCR activity below 350 °C was restrained by SO2. Moreover, the in-situ DRIFTS results indicate that Cu-SAPO-18 catalyzed NH3-SCR reaction predominantly proceeds through Langmuir−Hinshelwood (L−H) mechanism at low temperature. SO2 poisoning inhibited the adsorption of NO + O2 and NH3 on Cu2+ sites, thereby decreasing the formation of Cu−NOx and Cu−NH3 intermediates, evidently, the L−H mechanism was suppressed by SO2. Interestingly, the deactivated Cu-SAPO-18 could be regenerated under SCR gas at 550 °C and resumed at least most NH3-SCR activity.

The inflence of TiO2 structure on the complete decomposition of acetaldehyde gas

Crystallisation of amorphous TiO2 have been performed by two steps, the hydrothermal method and following heating in Ar at 450 °C or mild heating at 200 °C under vacuum. Both methods were successful in reducing the amount of OH groups on TiO2 surface, however heating at high temperature caused significant decrease of BET surface area and increase in mesoporosity of TiO2. Low hydroxylated surface of TiO2 caused, that acetaldehyde was adsorbed on its surface with chemical bounding and then could be decomposed via photocatalytic process. Although amount of acetaldehyde decomposed on TiO2 was comparable for both thermal heated samples, that than prepared at 200 °C under vacuum showed higher mineralisation degree and lower emission of formaldehyde from its surface. It appeared, that large pores present in sample heat treated at 450 °C favored diffusion of the formed byproducts from its surface and consequently lower mineralisation degree was obtained.

Effect of La-Fe/Si-MCM-41 catalysts and CaO additive on catalytic cracking of soybean oil for biofuel with low aromatics

La-Fe modified Si-MCM-41 (La-Fe/Si-MCM-41) catalysts were prepared by the wet impregnation method and used in catalytic cracking of soybean oil (CCS) for biofuel production. The catalysts were characterized by BET, XRD, XPS, Py-FTIR and CO2-TPD. The results showed that the aromatics content increased with the increase in B/L value, while the content of oxygenated compounds decreased, indicating that Brönsted acid sites were the major active sites for deoxygenation and aromatization reactions. Compared with Si-MCM-41, the Brönsted acidity of LFM-6 sharply decreased from 22.49 to 5.86 μmol g−1. Accordingly, the aromatics content was reduced from 37.51 wt.% to 14.52 wt.% which was lower than the limitation (15 wt.%) according to the global environmental legislation. However, for the LFM-6 catalyst, the excessive loss of Brönsted acid sites and sharp decrease in BET surface area and pore volume led to the decrease in deoxygenation. As a result, the fatty acids content increased from 2.71 wt.% to 16.67 wt.% and the acid value reached 35.20 mgKOH g−1. When the La-Fe loading increased to 15 wt.%, part of fatty acids were converted into ketones by the active sites on Fe2O3/La2O3 and strong Lewis acid sites on catalysts. Besides, the new weak Lewis acid and basic sites on Fe2O3/La2O3 exhibited the synergistic effect on promoting the generation of alkenes. The CaO/LFM-6 composite catalysts prepared by the mechanical mixing of LFM-6 and CaO were used in CCS to reduce the acid value of biofuel. LFM-6-C-3 was proved to be an effective catalyst for CCS to produce biofuel with low aromatics (12.31 wt.%) and fatty acids (2.76 wt.%) content.

Tuning phase evolution of β-MnO2 during microwave hydrothermal synthesis for high-performance aqueous Zn ion battery

Mild aqueous Zn–MnO2 battery attracts lots of attention in energy storage filed due to its low cost, high safety and environmental friendliness. To achieve high-performance in battery, phase evolution processes of MnO2 during synthesis and electrochemical reactions need to be understood. Herein, the phase evolution during microwave hydrothermal and correlated battery performance of β-MnO2 are studied. The results demonstrate a phase evolution mechanism from an initial mixture of vernadite, nsutite, and pyrolusite (β-MnO2) to a final single β-MnO2 phase, along with enhanced structure stability, increased Mn valence, and decreased BET surface area. It is found that only when microwave hydrothermal time (MHT) ≥ 120 min, β-MnO2 showing both high capacity and excellent cycling performance can be obtained. β-MnO2 prepared under a MHT of 120 min shows a high reversible capacity of 288 mA h g−1 with a median voltage of 1.36 V vs. Zn/Zn2+, and high capacity retentions of 91.8% after 200 cycles at 0.5C and 84.3% after 1000 cycles at 4C, respectively. In addition, the formation of inactive ZnMn2O4 during cycling is observed, which contributes to the capacity fading of β-MnO2 after long-term cycling. This research makes a step forward to the practical application of Zn–MnO2 batteries, and contributes to the large-scale energy storage field.

Enhanced photoelectrochemical hydrogenation of green-house gas CO2 to high-order solar fuel on coordinatively unsaturated metal-N sites containing carbonized Zn/Co ZIFs

Porous carbon-based catalysts facilitate CO2 photoelectrochemical reduction reaction (CO2PRR) through the high charge transfer ability and CO2 adsorption ability. However, the design of catalysts with high selectivity towards high-order solar fuels (such as ethanol and propanol) remains challenging. Herein, catalysts of carbonized Zn/Co Zeolitic Imidazolat Frameworks with various pyrolysis hours (xh-C-Zn/Co ZIFs) were synthesized and accessed for high selective CO2PRR for the first time. XRD and TEM analyses show that the C containing functional groups in pristine Zn/Co ZIF are carbonized and turned into amorphous porous carbon, while many Co and ZnO nanoparticles are formed during the pyrolysis process. Electrochemical characterizations of the catalysts prove that increasing pyrolysis time of Zn/Co ZIF from 1 h to 3 h, resulting in a decreased light current density from 3.3 mA/cm2 to 2.3 mA/cm2, which is much higher than that of Zn/Co ZIF (1.9 mA/cm2). Meanwhile, increasing pyrolysis time of Zn/Co ZIF from 1 h to 3 h results in decreased BET surface area and CO2 adsorption ability. XPS spectra suggest a decreased content of metal-nitrogen bonds in C–Zn/Co ZIF, which leads to the formation of coordinatively unsaturated metal-nitrogen sites. Density functional theory (DFT) calculations reveal that the coordinatively unsaturated CoN3V sites in C–Zn/Co ZIF had the highest catalytic activity towards high-order organics. The total carbon atom conversion rate reaches 5459 nmol/h·cm2 when 1h-C-Zn/Co ZIF is employed as catalyst in the CO2PRR system and the selectivity towards high-order solar fuel reaches 84%.

Facile fabrication of porous La doped ZnO granular nanocrystallites and their catalytic evaluation towards thermal decomposition of ammonium perchlorate

The present article expresses synthesis, characterization and catalytic activity of pure and La doped ZnO (La-ZnO) towards thermal decomposition of Ammonium Perchlorate (AP). The catalytic materials (La-ZnO) with 0–1.00% of doped La were synthesized by simple co-precipitation method and thoroughly characterized by several spectroscopic techniques like FT-IR, XRD, UV–Visible, PL, SEM-EDS and BET analysis. The XRD pattern of synthesized materials displayed wurtzite ZnO structure.The SEM images of the materials showed granular morphology where gradual increase in particle size and crystallite size was observed to be increased with increase in doped La concentration. The BET surface area of the materials was 28.203 to 15.830 m2/g and exhibited mesoporous nature. In catalytic studies for thermal decomposition of AP, the pure ZnO catalyst offered single stage decomposition of AP along with lowering high-thermal decomposition (HTD) temperature of AP by 105 OC. However, La doped ZnO showed slightly lower activity due to promotion of NO formation in oxidation of ammonia generated on initial decomposition of AP and decrease in BET surface area.