Temperature-programmed Desorption Of Carbon Dioxide Research Articles

Performance of NiO doped on alkaline sludge from waste photovoltaic industries for catalytic dry reforming of methane.

Alkali sludge (AS) is waste abundantly generated from solar photovoltaic (PV) solar cell industries. Since this potential basic material is still underutilized, a combination with NiO catalyst might greatly influence coke resentence, especially in high-temperature thermochemical reactions (Arora and Prasad, RSC Adv. 6:108,668-108688, 2016). This paper investigated alkaline sludge containing 3CaO-2SiO2 doped with well-known NiO to enhance the dry reforming of methane (DRM) reaction. The wet-impregnation method was used to prepare the xNiO/AS (x = 5-15%) catalysts. Subsequently, all catalysts were tested by using X-ray diffraction (XRD), nitrogen adsorption/desorption (BET), temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of carbon dioxide (TPD-CO2), field emission scanning electron microscopy (FESEM-EDX), and X-ray photoelectron spectroscopy (XPS). The spent catalysts were analyzed by thermogravimetric analysis (TGA/DTG), transmission electron microscopy (TEM), and temperature-programmed oxidation (TPO). The catalytic performance of xNiO/AS catalysts was investigated in a fixed bed reactor connected with gas chromatography thermal conductivity detector (GC-TCD) at a CH4:CO2 flow rate of 30 mL-1 during a 10-h reaction by following (Shamsuddin et al., Int. J. Energy Res. 45:15,463-15,480, 2021d). For optimization parameters, the effects of NiO concentration (5, 10, and 15%), reaction temperature (700, 750, 800, 850, and 900 °C), catalyst loading (0.1, 0.2, 0.3, 0.4, and 0.5 g), and gas hourly space velocity (GHSV) range from 3000, 6000, 9000, 12,000, and 15,000 h-1 were evaluated. The results showed that physical characteristics such as BET surface area and porosity do not significantly impact NiO percentages of dispersion, whereas chemical characteristics like reducibility are crucial for the catalysts' efficient catalytic activity. Due to the active sites on the catalyst surface being more accessible, increased NiO dispersion resulted in higher reactant conversion. The catalytic performance on various parameters that showed 15%NiO/AS exhibited high reactant conversion up to 98% and 40-60% product selectivity in 700 °C, 0.2 g catalyst loading, and 12,000 h-1 GHSV. According to spent catalyst analyses, the catalyst was stable even after the DRM reaction. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. Synergetic effect of efficient NiO as active metal and medium basic sites from AS enhanced DRM catalytic activity and stability with low coke formation.

Catalytic Hydrodeoxygenation of Vanillin, a Bio-Oil Model Compound over Renewable Ni/Biochar Catalyst

This study aims to examine the hydrodeoxygenation (HDO) of vanillin, an oxygenated phenolic compound present in bio-oil, into creosol. Biochar residue generated when wood is slowly pyrolyzed is utilized as a catalyst support. To improve biochar’s physicochemical properties, H2SO4 (sulfuric acid) and KOH (potassium hydroxide) are used as chemical activators. By means of a wet impregnation method with nickel salt, an Ni/biochar catalyst was prepared and utilized in the HDO of vanillin using a 100 mL Parr reactor, catalyst loading 0.4–0.8 g, temperature 100 °C to 150 °C, hydrogen (H2) pressures of 30 to 50 bar, and a stirring rate of 1000 rpm. The prepared catalysts were characterized with the nitrogen-sorption isotherm technique, carbon dioxide temperature-programmed desorption (CO2-TPD), scanning electron microscopy (SEM) coupled with energy dispersed X-ray analysis (EDX), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). Based on chemical treatment, Ni/biochar (KOH) pore sizes were found to be dominated by mesopores, with a surface area increase of 64.7% and a volume increase of 65.3%, while Ni/biochar (H2SO4) was mostly microporous and mesoporous, with an area increase of 372.3% and a volume increase of 256.8% in comparison to Ni/biochar (74.84 m2g−1 and 0.095 cm3g−1). Vanillin conversion of up to 97% with 91.17% selectivity to p-creosol was obtained over Ni/biochar catalyst; in addition to being highly selective and active for p-creosol, a plausible fuel, the catalyst was stable after four cycles. Chemical treatments of the biochar support resulted in improved physicochemical properties, leading to improved catalytic performance in terms of vanillin conversion and p-creosol yield in the order Ni/biochar (H2SO4) > Ni/biochar (KOH) > Ni/biochar.

Mesoporous aluminas synthesis using carboxylic acids to enhance performance in CO2 adsorption

This work evaluated for the first time the effect of carbon chain size of different carboxylic acids (stearic and caprylic acid) and crystallization temperatures (60, 120, and 180 °C) on the structural, textural, morphological, basic, and mechanism properties of reaction in the synthesis of mesoporous aluminas (meso-Al2O3). Regarding the structure-directing agents (SDA) traditionally used in the synthesis of meso-Al2O3 (i.g. strong acids, strong bases, and synthetic polymers), carboxylic acids are non-toxic, biodegradable compounds of low commercial value, and can be obtained from renewable sources. The physical-chemical characterizations performed, including low and high-angle X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermal analysis (TG/DTG), nitrogen adsorption-desorption, temperature-programmed desorption of carbon dioxide (CO2-TPD), scanning electron microscopy (SEM), and transmission (TEM), confirmed the formation of mesostructured γ-Al2O3. No pore organization was observed, but a system of interconnected channels was provided by the wormhole-like structure. Mesoporous aluminas synthesized at 180 °C showed an increase in structural, textural (higher of 68 % in pore volume and 36% in pore diameter), and basic properties (around 19 %) about materials synthesized at 60 °C. This can be attributed to the increased degree of coordination of the carboxylic acid with aluminum during the hydrolysis-condensation reactions. Furthermore, stearic acid (longer carbon chain carboxylic acid) tends to bend during micellar aggregation, leading to pore sizes 33% smaller than caprylic acid (shorter carbon chain acid). Therefore, the best condition for meso-Al2O3 synthesis was obtained at 180 °C and using caprylic acid (CAP-180 °C) as SDA. The results of CO2 adsorption showed that all materials correlate better with the pseudo-first order model in the entire temperature range studied (10 – 50 °C), suggesting that diffusion through the interface gas-solid (external diffusion) is the limiting step of the adsorption process. The adsorbent CAP-180 °C showed high adsorption capacity (around 134.45 mgCO2/gads at 10 °C under atmospheric pressure) and elevated stability after eight cycles of adsorption-desorption, reaching adsorption capacity superior to other meso-Al2O3.

Hydroxyapatite Derived from Salmon Bone As Green Ecoefficient Support for Ceria-Doped Nickel Catalyst for CO2 Methanation.

Hydroxyapatite (HA) derived from salmon bone byproducts is used as a green support for the nanostructured nickel catalysts applied in the methanation of carbon dioxide (CO2). Undoped nickel catalysts and various ceria-doped nickel supported on hydroxyapatite (HA) were prepared by coimpregnation. Characteristics of the as-prepared catalysts were investigated by the various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), hydrogen temperature-programmed reduction (H2-TPR), carbon dioxide temperature-programmed desorption (CO2-TPD), and energy-dispersive X-ray spectroscopy (EDX). The catalyst activity was assessed throughout CO2 methanation in the low-temperature range of 225–350 °C with the molar ratio of H2/CO2 = 4/1. The function of HA and ceria provided a high dispersity of nickel particles over the catalyst surface with the size range of 24.5–25.8 nm, leading to improvement in the reduction and CO2 adsorption capacity of the catalysts as well as enhancing the catalytic efficiency in CO2 methanation. The 10Ni/HA catalyst reduced at suitable conditions of 400 °C for 2 h showed the highest catalytic performance among the tested catalysts. CO2 conversion and CH4 selectivity reached 76.6 and 100% at a reaction temperature of 350 °C, respectively. The results show that the Ni/HA sample doped with 6.0 wt % ceria was the best, with the CO2 conversion and the CH4 selectivity reaching 92.5% and 100%, respectively, at a reaction temperature of 325 °C.

Study the Stable Diatomite-supported Catalyst for Biodiesel Production

The stable of natural diatomite supported by potassium hydroxide (KOH) as catalysts were synthesized for biodiesel production. A heterogeneous base catalyst prepared by impregnating KOH onto diatomite was also used to synthesize biodiesel from palm oil. All samples have been thoroughly characterized by Wavelength Dispersive X-ray Fluorescence (WDXRF), X-ray diffraction (XRD), N2 adsorption/desorption, Scanning electron microscopy (SEM), Energy dispersive spectrometer (EDS), and Temperature-programmed desorption of carbon dioxide (CO2-TPD). The XRD, XRF, and SEM results confi rm that adding KOH to diatomite results in structural change. The SiO2 and K2O phases form in the diatomite structural matrix during impregnation and the total basicity amount of this compound promotes the transesterifi cation process. A maximum fatty acid methyl ester (FAME) content of 84.56% was obtained. The reaction conditions were as follows: molar ratio of oil to methanol 1:9, catalyst loading 5 wt%, reaction time 2 h, and reaction temperature 75 °C. This work provides a possible new method for converting KOH from a homogeneous to a heterogeneous catalyst (Diatomite/KOH) that may show stable reusability, avoiding the separation and pollution problems in the environment.

Synthesis of Magnetic Base Catalyst from Industrial Waste for Transesterification of Palm Oil

Industrial waste is produced in large amounts annually; without proper planning, the waste might cause a serious threat to the environment. Hence, an industrial waste-based heterogeneous magnetic catalyst was synthesized using carbide lime waste (CLW) as raw material for biodiesel production via transesterification of palm oil. The catalyst was successfully synthesized by the one-step impregnation method and calcination at 600 °C. The synthesized catalyst, C-CLW/g-Fe2O3, was characterized by temperature-programmed desorption of carbon dioxide (CO2-TPD), scanning electron microscopy (SEM), electron dispersive X-ray spectroscopy (EDX), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET), vibrating sample magnetometer (VSM), and Fourier transform infrared spectroscopy (FT-IR). The catalyst has a specific surface area of 18.54 m2/g and high basicity of 3,637.20 µmol/g. The catalytic performance shows that the optimum reaction conditions are 6 wt% catalyst loading, 12:1 methanol to oil molar ratio with the reaction time of 3 h at 60 °C to produce 90.5% biodiesel yield. The catalyst exhibits good catalytic activity and magnetism, indicating that the CLW can be a potential raw material for catalyst preparation and application in the biodiesel industry. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Highly Active Biphasic Anatase-Rutile Ni-Pd/TNPs Nanocatalyst for the Reforming and Cracking Reactions of Microplastic Waste Dissolved in Phenol.

Solvent-based recycling of plastic can offer the main improvement when it is employed for pyrolysis-catalytic steam reforming. In this research, plastic waste dissolved in phenol was used as a feed for catalytic cracking and steam reforming reactions for valuable liquid fuels and hydrogen production, which is gaining the attention of researchers globally. Microplastic wastes (MPWs) are tiny plastic particles that arise due to product creation and breakdown of larger plastics. They can be found mainly in several habitats, including seas and freshwater ecosystems. MPWs harm aquatic species, turtles, and birds and were chosen to recover in this study that can be reacted on the catalyst surface. Biphasic anatase-rutile TiO2 with spherical-shaped support for Ni and Pd metals with nanosized particles was synthesized via the hydrothermal treatment method, and its chemical and physical properties were characterized accordingly. According to temperature-programmed desorption of carbon dioxide (CO2-TPD) and temperature-programmed reduction of hydrogen (H2-TPR) results, the incorporation of Pd into Ni/TNPs enhanced the basicity of the support surface and the redox properties of catalysts, which were strongly linked to the improved hydrogen yield (71%) and phenol conversion (79%) at 600 °C. The Ni-Pd/TNPs nanocatalyst, with remarkable stability for 72 h of time on stream, is a promising catalyst for the MPW-phenol cracking and steam reforming reactions toward H2 production for clean energy generation and other environmental applications. Besides, this study has also highlighted the opportunities of overcoming the risk of microplastic waste and converting it into valuable fuels such as decamethyltetrasiloxane, phenanthrene, methyl palmitate, benzenepropanoic acid, benzoic acid, azulene, xanthene, anisole, biphenyl, phthalic acid, diisooctyl phthalate, etc.

Synthesis of ternary magnetic nanoparticles for enhanced catalytic conversion of biomass-derived methyl levulinate into γ-valerolactone

Conversion of levulinic acid and its esters into versatile γ-valerolactone (GVL) is a pivotal and challenging step in biorefineries, limited by high catalyst cost, the use of hydrogen atmosphere, or tedious catalyst preparation and recycling process. Here we have successfully synthesized a ternary magnetic nanoparticle catalyst (Al2O3-ZrO2/Fe3O4(5)), over which biomass-derived methyl levulinate (ML) can be quantitively converted to GVL with an extremely high selectivity of > 99% and yield of ~98% in the absence of molecular hydrogen. Al2O3-ZrO2/Fe3O4(5) incorporates simultaneously inexpensive alumina and zirconia onto magnetite support by a facile coprecipitation method, giving rise to a core-shell structure, well-distributed acid-base sites, and strong magnetism, as evidenced by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-angle annular dark-field scanning-TEM (HAADF-STEM), SEM-energy dispersive X-ray spectroscopy (SEM-EDX), temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed desorption of carbon dioxide (CO2-TPD), pyridine-adsorption infrared spectra (Py-IR), and vibrating sample magnetometry (VSM). Such characteristics enable it to be highly active and easily recycled by a magnet for at least five cycles with a slight loss of its catalytic activity, avoiding a time-consuming and energy-intensive reactivation process. It is found that there was a synergistic effect among the metal oxides, and the high efficiency and selectivity originating from such synergism are evidenced by kinetic studies. Furthermore, a reaction mechanism regarding the hydrogenation of ML to GVL is proposed by these findings, coupled with gas chromatography-mass spectrometry (GC-MS) analysis. Accordingly, this readily synthesized and recovered magnetic nanocatalyst for conversion of biomass-derived ML into GVL can provide an eco-friendly and safe way for biomass valorization.

Effect of Ni/Malaysian dolomite catalyst synthesis technique on deoxygenation reaction activity of waste cooking oil

Local carbonate mineral, Malaysian dolomite has the potential as a deoxygenation catalyst due to its high capacity of CaO–MgO which enhances oxygen compound removal and produces high-quality green fuel with desirable lighter hydrocarbon. In this work, the performance of Ni-doped-calcined Malaysian dolomite (Ni/CMD900) catalyst with different catalyst synthesis techniques (precipitation, impregnation, and co-precipitation) were compared on the deoxygenation of waste cooking oil (WCO) process for green fuel production. The physicochemical properties of the synthesized catalyst were investigated by X-ray diffraction, Brunauer-Emmette-Teller surface area, temperature-programmed desorption of carbon dioxide, X-ray fluorescence, scanning emission microscopy and transmission electron microscopy analysis while the liquid products were analyzed by gas chromatography-mass spectroscopy and Fourier-transform infrared spectroscopy. Evidently from the result of the observation, the preparation technique plays an important role in determining the physicochemical properties of the catalyst for deoxygenation reaction of WCO in which precipitation technique outperformed other methods. Synthesized Ni-Malaysian dolomite-based catalyst, PRE/Ni/CMD900 catalyst was found to be superior in deoxygenation reaction activity as compared to other catalysts with high conversion of WCO (68.0%), high yield of pyrolysis oil (36.4%), and less coke formation (32.0%).

Synthesis of Carbide Lime Derived Strong Base Catalyst for Biodiesel Production

Carbide lime is a result of acetylene production. Carbide lime made out of calcium hydroxide with minor amount of calcium carbonate. In this study, carbide lime was used as the raw material to synthesize a new base catalyst with high base strength. A strong base catalyst was prepared through calcination and impregnation with potassium fluoride. The structure and morphology of catalyst were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) The base strength was determined by Hammett Indicator test, temperature-programmed desorption of carbon dioxide (TPD-CO2). The surface area of the catalyst was determined by Brunauer-Emmet-Teller isotherm (BET). The catalytic performance was examined through transesterification reaction. Fatty acid methyl ester (FAME) was successfully synthesized with the presence of carbide lime derived catalyst. The highest biodiesel conversion rate for sunflower oil was 95.83% with 6 wt% of catalyst loading while palm oil was 88.07% with 3 wt% of catalyst loading. The presence of the ester functional group was determined by Fourier Transform Infrared Spectroscopy (FTIR) analysis.

Effect of TMB/P123 ratios on physicochemical properties of mesocellular foam carbon (MCF-C) as catalyst for ethanol dehydrogenation

The preparation of mesocellular foam carbon catalysts with different ratios of 1,3,5-trimethyl benzene (TMB)/P123 is represented for investigation in catalytic activity via ethanol dehydrogenation to acetaldehyde. The TMB was used as a swelling agent and P123 acted as template-structuring. The physicochemical properties of synthesized catalysts were determined using Brunauer-Emmett-Teller (BET) surface area analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM)–energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), ammonia temperature-programmed desorption (NH3-TPD), and carbon dioxide temperature-programmed desorption (CO2-TPD). The evidence suggested that various ratios of TMB/P123 can differently control the mesostructure including the pore size, specific surface area, and pore volume. Particularly, MCF-C 3.5 catalyst (TMB/P123 of 3.5) enhanced the catalytic via ethanol dehydrogenation. Interestingly, effectively controllable pore structure of catalysts is beneficial for the desorption of selective product such as acetaldehyde leading to remarkably increased yield of acetaldehyde. Furthermore, the MCF-C 3.5 evidently exhibited outstanding stability at temperature of 400 °C for 12 h. Thus, it can be reasonably selected the ratio of TMB/P123 as 3.5, which is dominantly facilitated either high diffusion of reactant or high stability without losing of the traditional structure compared with other ratios of TMB/P123.

Effect of V2O5 promoter on characteristics and performance of NiO/CeO2 catalyst in methane bi-reforming

In this work, a series of 10 wt% NiO/CeO2 catalysts (Ni/Ce) promoted by V2O5 with content varying in the range of 0–0.5 wt% was prepared by the co-impregnation method. The characteristics of the catalysts were investigated by several techniques including N2 physisorption (BET), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), EDS mapping, carbon dioxide temperature-programmed desorption (CO2-TPD), and hydrogen temperature-programmed reduction (H2-TPR). The activity of the catalyst was studied in the micro-flow system in a temperature range of 550 °C–800 °C, the feedstock composition CH4/CO2/H2O of 3.0/1.2/2.4 and the weight hourly space velocity (WHSV) of 30,000 ml.h−1.g−1. Adding V2O5 additive, on the one hand increases the reducibility and basicity of Ni/Ce catalyst, on the other hand reduces oxygen vacancies and increases the crystal size of CeO2, leading to various effects on catalyst activity depending on its content. Ni/Ce catalyst promoted with 0.3 wt% of V2O5 was the best among tested ones, on which at reaction temperature of 700 °C, the conversion of CH4 and CO2 reached 97% and 77% respectively, and the molar ratio of H2/CO was 2.1. Meanwhile, on non-promoted Ni/Ce catalyst, the corresponding quantities were 83%, 62% and 1.9, respectively. It is important to note that performance of both was stable for more than 30 h thanks to the better resistance to coke deposition and structural stability.

Comparative study of transition metal-doped calcined Malaysian dolomite catalysts for WCO deoxygenation reaction

In the present work, nickel (Ni), zinc (Zn), copper (Cu), cobalt (Co) and iron (Fe) are tested as catalyst dopants on Malaysian dolomite calcined at T = 900 °C (CMD900). The physicochemical properties of all synthesised catalyst are investigated by X-ray diffraction, Brunauer–Emmett–Teller surface area, temperature-programmed desorption of carbon dioxide and scanning emission microscopy. The synthesised catalysts are tested on the basis of the deoxygenation (DO) reaction of waste cooking oil to produce liquid fuels under N2 atmosphere. The chemical composition of the liquid product is identified by gas chromatography–mass spectroscopy. The overall study suggests that Ni/CMD900 catalyst exhibits the highest performance with over 67.0% conversion and high selectivity (80.2%) with a high proportion of saturated linear hydrocarbons that corresponds to green diesel. Result indicates that Ni/CMD900 is a highly potential DO catalyst with 19.8% oxygenated compound, which is favourable for decarboxylation and/or decarboxylation predominates.

Improving the performance of nickel catalyst supported on mesostructured silica nanoparticles in methanation of CO2-rich gas by urea–nitrate combustion

In this work, NiO supported mesostructured silica nanoparticles (MSN) were synthesized via the urea–nitrate combustion method using urea as fuel and nitrate salts as oxidants with the different urea/nitrate ratios and calcination duration. The physicochemical properties of catalysts were investigated by several techniques, including N2 physisorption measurements, powder X-ray diffraction, N2-BET isothermal adsorption, hydrogen temperature-programmed reduction, carbon dioxide temperature-programmed desorption, scanning electron microscopy and transmission electron microscopy. The obtained catalysts were employed in the methanation of CO2-rich gas at a temperature range of 225–400 °C with the CO2/H2 ratio of 1/4 and CO2 concentration of 20 mol%. The results showed that using the urea–nitrate combustion method in synthesizing catalysts led to improved physicochemical properties that increased the activity of NiO/MSN catalysts. The catalyst prepared with the urea/nitrate molar ratio of 3 and calcined at 600 °C for 3 h showed the highest catalytic performance in methanation of CO2-rich gas, reaching CO2 conversion of 96% and CH4 selectivity of 100% at 375 °C. The best catalyst has excellent stability in CO2 solo-hydrogenation at a reaction temperature of 375 °C during 30 h of reaction thanks to the resistance to coke formation. Besides, adding 1 mol% CO in the feedstock should be simultaneously conducted to surge the effectivity of CO2 methanation.

Photocatalytic activity of transition metals (Mn, Fe, Ag and Ni doped ZnO) nanomaterials synthesised via sol-gel method: Active sites over band gap

Dopants with varied stoichiometry values were examined to determine their performances on photocatalysis. The sol-gel method was successfully synthesised using transition metals, namely manganese (Mn), Iron (Fe), silver (Ag) and nickel (Ni), as dopants in ZnO nanostructure. Zn(1-x)Mn(x)O, Zn(1-x)Fe(x)O, Zn(1-x)Ag(x)O and Zn(1-x)Ni(x)O (x=10%) were characterised by using X-ray diffraction (XRD), BET surface area analysis, temperature-programmed desorption of carbon dioxide (TPD–CO2) and UV-Vis spectrophotometer. A phase study on Mn- and Fe-doped ZnO nanoparticles confirmed that both the dopants experienced exceptional crystallinity with single-phase but Ag- and Ni- produced a multi-phases structures. Active sites of catalyst is proven to be an additional factor contributing towards photocatalysis in this work besides band gap and surface area. Temperature-programmed desorption of carbon dioxide (TPD–CO2) showed that the incorporation of Ag into ZnO lattice has enhanced the number of active sites on the surface of the catalyst whereas incorporation of Mn, Fe and Ni in ZnO has reduced it as compared to pure ZnO. Photocatalytic degradation of methyl orange for all stoichiometry of Ag-doped ZnO nanoparticles resulted in lower degradation time. Interestingly, 10% of Ag-doped ZnO achieved the highest degradation rate as much as 97.47 % at 160 minutes, hence emerging as the best amongst all other compositions.

Comparative study on photocatalytic activity of transition metals (Ag and Ni)-doped ZnO nanomaterials synthesized via sol-gel method.

Ag and Ni/ZnO photocatalyst nanostructures were successfully synthesized by a sol–gel method. In this work, the photocatalyst sample was systematically studied based on several factors affecting the performance of photocatalyst, which are size, morphology, band gap, textural properties and the number of active sites presence on the surface of the nanocatalyst. X-ray diffraction revealed that Ag/ZnO nanomaterials experienced multiple phases, meanwhile for Ni/ZnO the phase of nanomaterials were pure and single phase for stoichiometry less than 5%. Field emission scanning electron microscope (FESEM) showed almost all of the synthesized nanomaterials possessed a mixture of nanorods and spherical-like shape morphology. The Ag/ZnO showed high photocatalytic activity, producing at least 14th trials of nanocatalyst reusability on degradation of methyl orange under UV irradiation. Interestingly, this phenomenon was not observed in larger surface area of Ni/ZnO nanomaterials which supposedly favour photocatalytic activity, but instead producing poor photocatalytic performance. The main reasons were studied and exposed by temperature-programmed desorption of carbon dioxide (TPD–CO2) which showed that incorporation of Ag into ZnO lattice has enhanced the number of active sites on the surface of the nanocatalyst. Whereas incorporation of Ni in ZnO has lowered the number of active sites with respect to undoped ZnO. Active sites measurement is effective and significant, providing opportunities in developing an intensive study as an additional factor.

Preparation of Na2O supported CNTs nanocatalyst for efficient biodiesel production from waste-oil

The present work demonstrated the preparation of sodium oxide impregnated on carbon nanotubes (CNTs) and its application as a heterogeneous catalyst for transesterification of waste cooking oil. The catalyst was prepared by impregnation of metal oxide such as sodium oxide, Na2O on the CNTs by calcination at 500 °C for 3 h. It was assumed that the positive metal ion which is Na+ (cations) possess Lewis acidity, whereby, high negativity of oxygen ions can acts as the Brønsted bases, which could enhance the activity of the catalyst. The characterization of synthesized Na2O impregnated-CNTs nanocatalyst was performed using Temperature-programmed desorption of carbon dioxide (TPD-CO2), X-ray diffraction (XRD), infrared spectroscopy and Field emission scanning electron microscope (FESEM). Herein, the mechanism of the transesterification process assisted by the Lewis acidic metal oxide on carbon support was proposed and explained. Series of reactions were carried out to determine the performance of the catalyst. It was found that the prepared Na2O(20 wt%)/CNTs catalysts yielded above 97% of FAME yield at 65 °C assisted by 3 wt% of catalyst amount and 20:1 of methanol-to-oil molar ratio in 3 h of reaction time. Moreover, the results on catalyst’s reusability indicated that the catalyst could last for 3 subsequent reaction cycles due to deactivation of the catalyst caused by leaching of metal oxides and poisioning effect on the active sites. It can be concluded that the prepared Lewis acidic carbon catalyst has a potential to catalyse the production of biodiesel from waste cooking oil (WCO).

Comparative Studies of Fischer-Tropsch Synthesis on Iron Catalysts Supported on Al2O3-Cr2O3 (2:1), Multi-Walled Carbon Nanotubes or BEA Zeolite Systems

The main goal of the presented paper is to study the influence of a range of support materials, i.e., multi-walled carbon nanotubes (MWCNTs), Al2O3-Cr2O3 (2:1), zeolite β-H and zeolite β-Na on the physicochemical and catalytic properties in Fischer-Tropsch (F-T) synthesis. All tested Fe catalysts were synthesized using the impregnation method. Their physicochemical properties were extensively investigated using various characterization techniques such as the Temperature-Programmed Reduction of hydrogen (TPR-H2), X-ray diffraction, Temperature-Programmed Desorption of ammonia (TPD-NH3), Temperature-Programmed Desorption of carbon dioxide (TPD-CO2), Fourier transform infrared spectrometry (FTIR), Brunauer Emmett Teller method (BET) and Thermogravimetric Differential Analysis coupled with Mass Spectrometer (TG-DTA-MS). Activity tests were performed in F-T synthesis using a high-pressure fixed bed reactor and a gas mixture of H2 and CO (50% CO and 50% H2). The correlation between the physicochemical properties and reactivity in F-T synthesis was determined. The highest activity was from a 40%Fe/Al2O3-Cr2O3 (2:1) system which exhibited 89.9% of CO conversion and 66.6% selectivity toward liquid products. This catalyst also exhibited the lowest acidity, but the highest quantity of iron carbides on its surface. In addition, in the case of iron catalysts supported on MWCNTs or a binary oxide system, the smallest amount of carbon deposit formed on the surface of the catalyst during the F-T process was confirmed.

Application of carbon nanotubes prepared from CH4/CO2 over Ni/MgO catalysts in CO2 capture using a BEA–AMP bi-solvent blend

Abstract Carbon nanotubes (CNTs) were synthesized by the chemical vapour deposition of methane and carbon dioxide over a Ni/MgO catalyst. The synthesized CNTs were then mixed with K/MgO catalyst at different ratios and used as the catalyst for CO2 absorption in butylethanolamine-2-amino-2-methyl-l-propanol bi-solvent blend. The catalysts were characterized using X-ray diffraction, scanning electron microscopy, butylethanolamine, thermal gravimetric analysis and temperature-programmed desorption of carbon dioxide in order to determine the characteristics responsible for good CO2-absorption performance. The results showed that, with the addition of a catalyst into the amine solution, the amine reached equilibrium CO2 loading faster than without a catalyst. Also, the increase in the CNT content of the KMgO/CNTs catalyst made the CO2 absorption reach equilibrium much more quickly compared with just KMgO alone and without a catalyst. The KMgO/CNTs at a ratio of 1:4 yielded the fastest time to reach CO2-loading equilibrium at 240 min, which was mainly due to the increase in strong basic sites as well as the highest total basic sites with an increase in CNT content. In addition, because of the extremely large specific surface area and pore volume generated due to the CNT, the number of exposed active centres per unit mass increased tremendously, leading to a corresponding tremendous increase in CO2 absorption.

K/Al-doped ZnO nanocomposite as bifunctional catalyst for photocatalysis and synthesis of dimethyl carbonate

In this paper, K/Al-doped ZnO nanocomposite was prepared by coprecipitation and impregnation method using sodium hydroxide as precipitation agent. The title material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV–Vis), Brunauer-Emmett-Teller (BET) and temperature-programmed desorption of carbon dioxide (CO2-TPD). K/Al-doped ZnO as photocatalyst exhibits highly efficient photocatalytic performance for degradation of four typical dyes (Methylene blue (MB), Congo red (CR), Rhodamine B (RhB) and Methyl orange (MO)) under UV-light irradiation. The photocatalytic decomposition rate in the order of CR (91.40%) > MB (82.47%) > RhB (54.96%) > MO (51.70%). The comparative experiments show that K/Al-doped ZnO composite possesses higher activity relative to ZnO, Al2O3 and Al-doped ZnO. Furthermore, the composite also has unique catalytic behavior for the one-pot synthesis of dimethyl carbonate (DMC) from methanol (MeOH), epoxy propane (PO) and CO2, which may be an effective and simple material to one-pot synthesize DMC in industry.