Chemical Impregnation Research Articles

CeO2 added V2O5/TiO2 catalyst prepared by chemical vapor condensation (CVC) and impregnation method for enhanced NH3-SCR of NOx at low temperature

In this study, we confirm the role of CeO2 in promoting the catalytic activity of a selective catalytic reduction (SCR) catalyst, prepared using chemical vapor condensation (CVC)-TiO2 nanoparticles, and the effect of the V2O5-CeO2/CVC-TiO2 catalyst on the NH3-SCR of DeNOx with/without SO2 and water vapor process. The catalyst showed good SCR activity for NOx removal, and also exhibited enhanced SCR activity in the presence of SO2 and water vapor at low temperatures, significantly. In addition, the catalyst was characterized by various physicochemical analysis techniques. In summary, CeO2 existed in the amorphous (poor crystallinity) phase. The catalyst with added CeO2 contained more Ce3+ ions that provided more redox-active sites. CeO2 provided more surface chemisorbed oxygen, thus dramatically increasing reducibility, and more acid sites.

Optimum BET surface areas for activated carbon produced from textile sewage sludges and its application as dye removal

The purpose of this experimental study is to determine optimum preparation conditions for activated carbons obtained from textile sewage sludge (TSS) for removal of dyes from aqueous solutions. The textile sewage sludge activated carbon (TSSAC) was prepared by chemical activation with potassium hydroxide using Response Surface Methodology (RSM). The most influential factor on each experimental design responses was identified via ANNOVA analysis. Based on the central composite design (CCD), quadratic model was developed to correlate the preparation variables for one response which is the Brunauer–Emmelt–Teller (BET) surface area. RSM based on a three-variable CCD was used to determine the effect of pyrolyzed temperature (400–700 °C), carbonization time (45–180 min) and KOH: weight of TSS (wt%) impregnation ratio (0.5:1–1.5:1) on BET surface area. According to the results, pyrolyzed temperature and impregnation ratio were found as the significant factors for maximizing the BET surface area. The major effect which influences the BET surface area was found as pyrolyzed temperature. Both carbonization time and impregnation ratio of KOH had no significant effect. The optimum conditions for preparing TSSAC, based on response surface and contour plots, were found as follows: pyrolyzed temperature 700 °C, carbonization time of 45 min and chemical impregnation ratio of 0.5. The maximum and optimum BET surface area of TSSAC were found as 336 m2/g and 310.62 m2/g, respectively. Synozol Blue reactive (RSB) and Setapers Yellow–Brown (P2RFL) industrial textile dyes adsorption capacities were investigated. As expected the TSSAC which has the biggest BET surface area (336 m2/g) adsorbed dye best. The maximum (RSB) and (P2RFL) uptake capacities were found as 8.5383 mg/g and 5.4 mg/g, respectively. The results of this study indicated the applicability of TSSAC for removing industrial dyes from aqueous solution.

Optimization of preparation conditions for activated carbon from Brachystegia eurycoma seed hulls: A new precursor using central composite design

One of the drawbacks troubling agrarian countries like Nigeria is handling so many agricultural by-products lying as wastes thereby causing environmental contamination. Activated carbon production is a significant way of managing such waste materials which result in to waste minimization as well as massive cost saving. Physiochemical activation method was employed in this work for activated carbon production using Brachystegia eurycoma seed hulls (BESH) as new precursor materials. The preparation method involved treatment with potassium carbonate (K2CO3) as chemical activating agent. Central composite design (CCD) was applied to study the influence of activation temperature, chemical impregnation ratio (IR) and activation time on the physicochemical activation process. Based on the CCD, a quadratic model and a two-factor interaction (2FI) model were established for malachite green (MG) elimination in percentage and BESH-AC yield respectively. The prime conditions for BESH-AC production were found as 760°C (activation temperature), IR of 1.00 and 117min (activation time) ensuing into 91.41% of MG removal and 19.24% of BESH-AC yield. Characterization of the adsorbent revealed it to be mesoporous with large surface area attributed to intercalation of potassium ion. The equilibrium data for adsorption of MG on the optimum activated carbon were well represented by the Langmuir isotherm, giving maximum monolayer adsorption capacity as high as 370.37mg/g at 30°C.

Continuous selective oxidation of methane to methanol over Cu- and Fe-modified ZSM-5 catalysts in a flow reactor

The selective oxidation of methane to methanol is a key challenge in catalysis. Iron and copper modified ZSM-5 catalysts are shown to be effective for this reaction using H2O2 as the oxidant under continuous flow operation. Co-impregnation of ZSM-5 with Fe and Cu by chemical vapour impregnation yielded catalysts that showed high selectivity to methanol (>92% selectivity, 0.5% conversion), as the only product in the liquid phase. The catalysts investigated did not deactivate during continuous reaction, and methanol selectivity remained high. The effect of reaction pressure, temperature, hydrogen peroxide concentration and catalyst mass were investigated. An increase in any of these led to increased methane conversion, with high methanol selectivity (≥73%) maintained throughout. Catalysts were characterised using DR-FTIR, DR-UV-Vis and 27Al MAS-NMR spectroscopy.

CHARACTERIZATION OF PHOSPHORIC ACID IMPREGNATED ACTIVATED CARBON PRODUCED FROM HONEYDEW PEEL

The role of waste materials in producing activated carbon (AC) used in adsorption has been identified as an alternative to substitute commercial expensive wooden starting materials. The present study has chosen honeydew peel as an alternative starting material in activated carbon production because of it’s low cost, availabality and incurs minimal cost for waste management. The production involved chemical impregnation using 20% diluted phosphoric acid (H3PO4) prior to activation. To optimize the activation method, the effect of different activation temperatures (470°C - 550°C) on the physicochemical properties of the AC was studied. The results showed that the AC carbonized at 490°C possessed 942 mg/g iodine number, 997 m2/g surface area SBET and 0.56 ml/g total pore volume. FESEM images showed a high pore development as the activation temperature increased. FTIR indicated the presence of –OH, C=O bond in carboxylic acids, ketones, aldehydes, lactones and ester functional groups on the AC. The experimental results presented the potential use of honeydew peel as a precursor material in the preparation of inexpensive adsorbent for wastewater remediation.

Al grafted natural hydroxyapatite for neem oil transesterification: Kinetic study at optimal point

In this work, Al metal ions were doped on natural hydroxyapatite by wet chemical impregnation route. The hydroxyapatite was obtained from waste cooked fish bones after proper treatment. The developed catalyst was characterized. From BET analysis it was found that the surface area and pore volume has increased up to 157.96m2g−1 and 0.8062mLg−1 after Al doping followed by calcination. The FE-SEM micrographs showed the homogenous porous structure distribution on the surface of the Al doped catalyst. From TGA analysis, it was found that the catalyst was stable up to 1000°C. A comparison of the developed catalyst with other catalysts reported in literature confirmed the superiority of this catalyst. Doping of Al ion and calcination played a significant role during transesterification of neem (Azadirachta indica) oil which was clearly envisaged. The kinetics of transesterification was thoroughly studied at optimal condition, which was found out using response surface methodology. The physical properties of the transesterified product were calculated by following the usual ASTM protocols. The catalyst reusability was also studied.

Optimization of process variables by response surface methodology for malachite green dye removal using lime peel activated carbon

This study investigates the adsorptive removal of malachite green (MG) dye from aqueous solutions using chemically modified lime-peel-based activated carbon (LPAC). The adsorbent prepared was characterized using FTIR, SEM, Proximate analysis and BET techniques, respectively. Central composite design (CCD) in response surface methodology (RSM) was used to optimize the adsorption process. The effects of three variables: activation temperature, activation time and chemical impregnation ratio (IR) using KOH and their effects on percentage of dye removal and LPAC yield were investigated. Based on CCD design, quadratic models and two factor interactions (2FI) were developed correlating the adsorption variables to the two responses. Analysis of variance (ANOVA) was used to judge the adequacy of the model. The optimum conditions of MG dye removal using LPAC are: activation temperature (796 °C), activation time (1.0 h) and impregnation ratio (2.6), respectively. The percentage of MG dye removal obtained was 94.68 % resulting in 17.88 % LPAC yield. The percentage of error between predicted and experimental results for the removal of MG dye is 0.4 %. Model prediction was in good agreement with experimental results and LPAC was found to be effective in removing MG dye from aqueous solution.

Factor Affecting Microwave Assisted Preparation of Activated Carbon from Local Raw Materials

This study illustrates the preparation of activated carbon (AC) from Corn Cob (CC) via microwave assisted K2CO3 activation. The effect of operational parameters including chemical impregnation ratio (0.25-1.25), microwave power (90 – 800 W) and irradiation time (1 – 9 min) on the carbon yield and adsorption capability of derived Corn Cob Activated Carbon (CCAC) were investigated. The results indicated that the optimum conditions were as follows: microwave power of 600W, microwave radiation time of 5 min and the impregnation ratio of K2CO3 was 0.75 g/g. The optimum conditions resulted in CCAC with a maximum adsorption capacity of 275.32 mg/g for MB and carbon yield of 27.09%. The BET surface area, Langmuir surface area and total pore volume were determined to be 765 m2/g, 834 m2/g and 0.43 cm3/g, respectively.

Factor Affecting Microwave Assisted Preparation of Activated Carbon from Local Raw Materials

This study illustrates the preparation of activated carbon (AC) from Corn Cob (CC) via microwave assisted K2CO3 activation. The effect of operational parameters including chemical impregnation ratio (0.25-1.25), microwave power (90 – 800 W) and irradiation time (1 – 9 min) on the carbon yield and adsorption capability of derived Corn Cob Activated Carbon (CCAC) were investigated. The results indicated that the optimum conditions were as follows: microwave power of 600W, microwave radiation time of 5 min and the impregnation ratio of K2CO3 was 0.75 g/g. The optimum conditions resulted in CCAC with a maximum adsorption capacity of 275.32 mg/g for MB and carbon yield of 27.09%. The BET surface area, Langmuir surface area and total pore volume were determined to be 765 m2/g, 834 m2/g and 0.43 cm3/g, respectively.

Preparation and properties of carbon fiber-reinforced carbon and ceramic composites through a combination of chemical vapor infiltration and polymer impregnation pyrolysis

Carbon fiber-reinforced carbon composites (C/C), carbon fiber reinforced-carbon and silicon carbide binary matrix composites (C/C–SiC) and carbon fiber reinforced carbon–silicon–zirconium–oxygen matrix composites (C/C–Si–Zr–O) were prepared through a combination of chemical vapor infiltration (CVI) and polymer impregnation pyrolysis. The microscopic morphology, phase structure, mechanical properties and thermal conductivity of the C/C, C/C–SiC and C/C–Si–Zr–O composites were investigated by SEM, XRD, EDA and laser flash thermal conductive measurements. Results showed that the flexural strength of the C/C–Si–Zr–O composites was higher than that of the C/C and the C/C–SiC composites, which can be ascribed to their energy absorption mechanisms, such as fiber debonding and pull-out from the matrix. The C/C composites possessed the highest thermal conductivity (69.09 W/(m K) in the parallel direction and 25.28 W/(m K) in the vertical direction), which can be accounted for by the high thermal conductivity of the pyrocarbon matrix, a low porosity of the composites, a long phonon mean free path and fewer structural defects. [New Carbon Materials 2014, 29(6): 467–472]

Green synthesis of Pt-doped TiO2 nanocrystals with exposed (001) facets and mesoscopic void space for photo-splitting of water under solar irradiation.

We report a non-trivial facile chemical approach using ionic liquid ([bmim][Cl]) as a porogen for the synthesis of (001) faceted TiO2 nanocrystals having mesoscopic void space. This faceted TiO2 nanomaterial has been doped with Pt nanoclusters through chemical impregnation. The resulting Pt-doped TiO2 nanomaterials are thoroughly characterized by powder X-ray diffraction (PXRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), ultra high resolution transmission electron microscopy (UHR-TEM), energy dispersive X-ray spectrometry (EDX), UV-vis diffuse reflection spectroscopy (DRS) and N2 sorption studies. These Pt/TiO2 nanocrystals with (001) exposed facets are employed as efficient and benign catalysts for hydrogen production from pure water and methanol-water systems under one AM 1.5G sunlight illumination. The effect of platinum loading and methanol-water ratio on the photocatalytic activity of the faceted TiO2 nanocrystals are investigated and it is found that hydrogen evolution rates have been enhanced significantly upon Pt loading. Under optimized reaction conditions the highest photocatalytic activity of 11.2 mmol h(-1) g(-1) has been achieved over ca. 1.0 wt% Pt loaded Pt/TiO2 nanocrystals with (001) exposed facets, which is one of the highest hydrogen evolution rates over the noble metal/TiO2 system reported to date in the literature.

Enhancing Sustainable Recycle Solid Waste to Porous Activated Carbon for Methane Uptake

Potential agro wastes (i.e palm kernel shell and coconut shell) for producing low cost activated carbon (AC) was investigated. In this study, the activated carbon was produced by carbonization, chemical impregnation with KOH and microwave irradiation. The pyrolysis was carried out at 700 °C in an inert environment for 2 h. Microwave activation was carried out at 400W for 6 minutes. Characteristics of the material were investigated using Fourier transform infrared spectroscopy (FT-IR) analysis and scanning electrode microscopy (SEM). Methane adsorption equilibrium data on the activated carbons produced were obtained using static volumetric method. Microwave palm shell activated carbon (MPAC) and microwave coconut shell activated carbon (MCAC) recorded highest methane uptake of 2.489 and 1.929 mmol/g at 3 bar, 30°C. The adsorption data were correlated with Langmuir and Freundlich isotherms. The results shows that microwave activated carbon from palm shell and coconut shell have good methane adsorption characteristics.

Activated carbon xerogel–chitosan composite materials for catalytic wet peroxide oxidation under intensified process conditions

Different activated carbon xerogels (ACX) and ACX–chitosan composite materials were tested for the removal of the azo dye Orange II (OII) in aqueous solutions, either by pure adsorption or by catalytic wet peroxide oxidation (CWPO). The ACX materials were produced by activation of an organic resorcinol-formaldehyde xerogel (RFX), considering different activation procedures: chemical impregnation with H3PO4 at 773K (ACX-P), chemical impregnation with monoethanolamine at 773K (ACX–MEA) and alkali activation with KOH at 1073K using a 1:1 mass ratio of KOH/RFX (ACX-K). The ACX–chitosan composites were produced by oxidation of ACX with oxalic acid followed by treatment with chitosan gel.During screening studies in adsorption and CWPO tests, the composites ACX-K–chitosan and ACX-P–chitosan revealed the best performances among all the tested materials, namely OII removals between 69 and 73% were respectively obtained in CWPO after 150min (pH 3.0, T=323K, material load of 0.2gL−1, OII concentration of 100mgL−1 and hydrogen peroxide concentration of 1.18gL−1). In process intensification conditions, the CWPO process performance increased remarkably when using the ACX-P–chitosan composite. Complete OII removal in 90min and a TOC removal of 55% in 24h was achieved by CWPO, while less than 10% of OII was removed by pure adsorption (pH 3.5, T=353K, material load of 2.5gL−1, OII concentration of 4.5gL−1 and, in CWPO, hydrogen peroxide concentration of 25gL−1).The superior performance of the ACX–chitosan composite at intensified process conditions was more likely related with the high pollutant/catalyst ratio, which favors a more controllable H2O2 decomposition near the adsorbed pollutant species, thus avoiding parallel parasite reactions involving hydroxyl radicals and leading to a consequent higher efficiency of its usage. These conditions are of major interest in the treatment of highly polluted waste waters.

Carbon aerogel supported Pt–Zn catalyst and its oxygen reduction catalytic performance in magnesium-air batteries

Abstract

Influence of the Si–O–C interlayer on the oxidation behaviors and mechanisms of composites

Carbon fiber-reinforced Si–C–N matrix composite with a Si–O–C interlayer (C/Si–O–C/Si–C–N) was fabricated via chemical vapor infiltration and polymer impregnation and pyrolysis processes. The oxidation behaviors of C/Si–O–C/Si–C–N were investigated in air by comparing with that of C/Si–C–N using thermogravimetry and SEM techniques. The results indicate that the weight loss of the C/Si–O–C/Si–C–N increases with the increase in the temperature below 800 °C, decreases in the range of 800–1000 °C, and increases again above 1000 °C. The oxidation resistance of C/Si–O–C/Si–C–N was improved greatly as compared to C/Si–C–N within the temperature range from 600 to 1200 °C. The higher oxidation resistance of C/Si–O–C/Si–C–N results from the low density of crack, weak interfacial bond of Si–O–C interphase/matrix, and tight interfacial bond of interphase/carbon fiber. The weak interfacial bond between Si–O–C interphase is the main reason for improvement of oxidation resistance of C/Si–O–C/Si–C–N.

Recycling Wood Composite Panels: Characterizing Recycled Materials

Downgraded medium density fiberboard (MDF), particleboard (PB), and oriented strandboard (OSB) panels were individually subjected to steam explosion treatment. Downgraded MDF and PB panels were separately treated with thermal chemical impregnation using 0.5% butanetetracarboxylic acid (BTCA). And downgraded PB panels were processed with mechanical hammermilling. The pH, buffer capacity, fiber length, and particle size of these recycled materials were evaluated. After the steam explosion and thermal chemical impregnation treatments, the pH and buffer capacity of recycled urea formaldehyde resin (UF)-bonded MDF and PB furnishes increased and the fiber length decreased. The hammermilling of recycled PB was less likely to break particles down into sizes less than 1 mm2.

Impregnation of La0.4Ce0.6O1.8–La0.4Sr0.6TiO3 as solid oxide fuel cell anode in H2S-containing fuels

Active anodes were fabricated via wet chemical impregnation of optimized amount of La0.4Sr0.6TiO3 (L4ST) into La0.4Ce0.6O1.8 (LDC) pre-infiltrated porous yttria-stabilized zirconia (YSZ) matrix. Impregnations of 10 wt% LDC with 16 wt% L4ST significantly improved the performance of the fuel cell from 48 mW cm−2 for pure L4ST to 161 mW cm−2 for LDC–L4ST at 900 °C in H2. The contribution of the pre-loaded LDC to this improvement was investigated using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). The measurement results indicated that pre-infiltrated LDC increased the activity of the anode more effectively by decreasing the total polarization resistance of the cell from 3.3 Ω cm2 to 1.0 Ω cm2 in humidified H2 at 900 °C. More importantly, the LDC nano-deposits (<20 nm) behaved as an effective “adhesive” that substantially enhanced the wettability of L4ST on YSZ matrix, resulting in finer and more uniform structure of L4ST infiltrates. The LDC–L4ST cells also demonstrated significantly improved performances in 0.5% H2S–H2 and 0.5% H2S–CH4 with higher stability than cells with pure L4ST anode.

Activated carbons derived from residual biomass pyrolysis and their CO2 adsorption capacity

This research aimed to investigate the pyrolysis process of rapeseed oil cake/walnut shell mixture and to assess the pyrolysis products. The solid fraction was then subjected to high temperature treatment using CO2 65vol.% in nitrogen (N2) as activation agent to obtain activated carbons. The carbon samples were characterized by scanning electron microscopy (SEM), N2 adsorption at (−196.15°C) and measurements of mechanical strength. Two surface treatment methods, including ammonium (NH3) heat treatment and aqueous monoethanolamine (MEA) impregnation, were used to modify the surface properties of the carbons to increase their CO2 capture capacity. The influence of treatment conditions and chemical reagent type on carbons properties were investigated and discussed. The surface treatment changed the porous structure and surface chemistry and affected CO2 adsorption capacity. NH3 was found more effective than MEA under identical conditions. The NH3 treatment increased the surface area, especially at lower temperatures (600°C) while the chemical impregnation with MEA resulted in a decrease of the surface area. Both the NH3 treatment and monoethanolamine impregnation have increased the CO2 adsorption capacity at higher temperature due to the introduction of alkaline nitrogen groups on the surface of carbons that are selective to CO2 molecules.

Methane Adsorption on Chemically Modified Microwave Irradiated Palm Shell Porous Carbon

Low-cost palm shell was used as a precursor for preparation of porous carbons via chemical impregnation with K2CO3 and microwave heating. Volumetric adsorption setup was used to measure the adsorption capacity of methane at 303.15 K under pressure up to 4 bars. The methane adsorption data was modelled by Langmuir, Freundlich, and Dubinin–Radushkevich (DR) isotherm equations. Langmuir and Freundlich models were found to have the best fit than DR isotherm. The kinetics of methane adsorption on the microwave porous carbon followed pseudosecond-order model equation. The highest methane adsorption capacity obtained was 3.533 mmol/g at 4 bar and 303.15 K. It was noticed that there is increase in adsorption with increased in initial pressure. The porous carbon displayed good adsorption characteristics for methane.

Recyclable three-dimensional Ag nanoparticle-decorated TiO2 nanorod arrays for surface-enhanced Raman scattering

Multifunctional Ag nanoparticle-decorated TiO2 nanorod arrays were prepared by two simple processes. TiO2 nanorod arrays were first fabricated by the hydrothermal route and then Ag nanoparticles were decorated on the nanorods by the chemical reduction impregnation method. Three-dimensional Ag/TiO2 arrays were used as an active substrate for surface-enhanced Raman scattering (SERS). The results show that the detection limit for rhodamine 6G (R6G) was as low as 10−7M and the Raman enhancement factor was as large as 105. After calibrating the Raman peak intensities of R6G, it could be quantitatively detected. More importantly, the photocatalytic activity of TiO2 provides a self-cleaning capability to the SERS substrate, which can be recycled and used to degrade many Ag surface adsorbates such as R6G, methyl orange, Congo red, and methylene blue after exposure to visible light. The absorbed small molecules can all be rapidly and completely removed from the SERS substrate, which has been successfully reused four times without a decrease in accuracy or sensitivity. Our results reveal that the unique recyclable property not only paves a new way to solve the single-use problem of traditional SERS substrates but also provides more SERS platforms for multiple detections of other organic molecular species.