Temperature-programmed Desorption Of Carbon Dioxide Research Articles

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.

Development of high microwave-absorptive bifunctional graphene oxide-based catalyst for biodiesel production

A novel heterogeneous bi-functional catalyst namely silicon carbide/sodium hydroxide-graphene oxide (SiC/NaOH-GO) was successfully developed and characterized using fourier transform infrared spectroscopy (FT-IR), thermogravimetry analysis (TGA), scanning electron microscope (SEM), energy disperse X-ray analysis (EDX), Brunauer–Emmett–Teller analysis (BET), X-ray diffraction (XRD), carbon dioxide temperature programmed-desorption of carbon dioxide (CO2-TPD) and ammonia temperature programmed-desorption (NH3-TPD). The catalyst was applied in microwave-assisted transesterification and esterification of binary model feedstock (rapeseed oil and oleic acid) containing 20% free fatty acid (FFA) and optimized using respond surface methodology (RSM) based on centre composite design. The study revealed that the optimum reaction conditions were 13:1 wt ratio of SiC/NaOH to GO, 5 wt% of catalyst loading, reaction temperature of 65 °C and 6 min reaction time to attain 96% of yield of transesterification and 92% of yield of esterification. Then, the optimized catalyst (13:1 wt ratio of SiC/NaOH) was applied in Chlorella vulgaris lipid with high free fatty acid content (26%) to further confirmed the ability of converting triglycerides and free fatty acid (FFA) to biodiesel simultaneously. The study revealed that 92% of FFA of microalgae lipid was converted and 81% of fatty acid methyl ester content (FAME) was attained under the optimum conditions of methanol to lipid molar ratio of 48, 5 min reaction time, 4 wt% catalyst and reaction temperature of 85 °C.

Kinetics of gas-phase photooxidation of p-xylene on nano TiO2 P25 thin film

In this investigation, the thin film of degussa P25 was obtained by dip coating method and calcined at 450 °C for 2 h (P25-450-2) and used as photocatalyst for gas-phase photooxidation of xylene. The physico-chemical properties of calcined P25-450-2 powder was studied by the methods of BET adsorption, XRD, FTIR, UV–vis, Raman spectroscopies, SEM, TEM, carbon dioxide temperature-programmed desorption . The thickness of the film was determined on the Alpha Step IQ KLA—Ctencor equipment and the point of zero charge (PZC) of the sample was determined by salt addition method. P25-450-2, having a band gap of 3.155 eV, is advisable to use UV lamps in photocatalytic reactions. The kinetics of gas-phase photooxidation of xylene reaction on the thin films of P25-450-2 under UV illumination was studied using a gradientless flow circulating system at atmospheric pressure and 40 °C. The obtained results showed that the kinetics of the given reaction should be written by fractional equations describing the dependence of the reaction rate on the concentration of adsorbed molecules of xylene and oxygen, dissociative adsorbed water vapor, and also on the total intensity of light. The reaction was proposed to follow the Langmuir-Hinshelwood mechanism.

Hydroxyapatite supported gold nanocatalyst for base-free oxidative esterification of 5-hydroxymethyl-2-furfural to 2,5-furan dimethylcarboxylate with air as oxidant

A series of gold (Au) nanocatalysts has been prepared for base-free protocol-oxidative esterification of lignocellulosic biomass derived 5-hydroxymethyl-2-furfural (HMF) to 2,5-furan dimethylcarboxylate (FDMC) in the presence of air. The prepared Au-based nanocatalysts are thoroughly characterized by various analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2-physisorption (adsorption–desorption) method, inductive coupled plasma-atomic emission (ICP-AES) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Moreover, the surface properties of Au-based nanocatalysts were investigated by temperature-programmed desorption of carbon dioxide (CO2-TPD) technique. For a comparison point of view, the activity tests of various prepared metal-based nanocatalysts have also been carried out. Among all, hydroxyapatite (HAP) supported Au nanocatalyst (Au/HAP) prepared by homogeneous deposition–precipitation (HDP) method was found to be the best to give 89.3% yield of FDMC from oxidative esterification of HMF in the presence of air. The excellent yield of FDMC could be attributed to stronger basic sites on the surface of the catalyst. Furthermore, Au/HAP nanocatalyst was simply recovered and reused, which retained its original activity even after five consecutive times without significant loss of original activity, supporting its reusability and stability.

The investigation of the role of basic lanthanum (La) species on the improvement of catalytic activity and stability of HZSM-5 material for eliminating methanethiol-(CH3SH)

Lanthanum (La)-doped HZSM-5 and HZSM-5 catalysts were prepared to investigate the natural roles of La addition on the catalytic performance of HZSM-5 for decomposing methanethiol (CH3SH). Compared to HZSM-5, the incorporation of La species into HZSM-5 catalyst not only decreased the intrinsic activation energy (from 51.4 kJ/mol to 40.6 kJ/mol) but also largely improved the stability. Based on the characterizations of X-ray diffraction pattern (XRD), N2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of carbon dioxide (CO2-TPD), temperature-programmed desorption of ammonia (NH3-TPD), and temperature programmed desorption of CH3SH (CH3SH-TPD), the promotional role of La species on the catalytic activity was demonstrated to be the contribution of the surface active oxygen species within lanthanum oxy-carbonates composites, which not only might act as new active sites for converting CH3SH into CO2 but also could decrease the activation temperature for the dehydrogenation of CH3SH into intermediate, dimethyl sulfide (CH3SCH3). The enhanced stability of La doped HZSM-5 was attributed to the synergistic effect of the decrease in the strong acid sites as well as the formed CO2 and surface lanthanum oxy-carbonates layer. The rapid deactivation of HZSM-5 was due to the formation of deposited coke irrespective of deposited sulfur species. The nature, amount and type of deposited coke were investigated in detail via the characterization of FTIR, Raman spectroscopy, temperature programmed oxidation of oxygen (O2-TPO), thermogravmetric analysis (TGA). A facile and rapid regeneration method was used to regenerate spent La doped HZSM-5 and no significant deactivation was observed even after three cycles of deactivation-regeneration.

Bifunctional electrocatalysts for oxygen reduction/evolution reactions derived from NiCoFe LDH materials

Materials obtained from thermal treatment of thermally treated NiCoFe-layered double hydroxides (LDH) with different Ni:Co ratios were evaluated as bifunctional catalysts for Oxygen Reduction Evolution and Evolution Reduction Reactions in alkaline media. The structural properties of synthesized materials were characterized by X-ray diffraction, Fourier-transform infrared, Raman, and X-ray photoelectron spectroscopies, whereas the basicity of each material was evaluated by temperature-programmed desorption of carbon dioxide. The results revealed the presence of inverse spinel structure with different compositions and a NiO phase with different amounts in the sample, while the electrochemical results showed a high activity towards oxygen reactions. The sample with higher amount of NiO and the lowest substitution grade on tetrahedral sites in the spinel-type structure exhibited the best catalytic activity.

High-Performance Arsine Removal Using CuOx/TiO2 Sorbents under Low-Temperature Conditions

In this work, copper-based titanium sorbents (CuOx/TiO2) synthesized by sol–gel method were used to remove arsine (AsH3) at low temperatures. The Cu content, calcination temperature, pH, oxygen concentration, and reaction temperature were the five key factors that were determined and analyzed in this work. The optimum breakthrough adsorption capacity for arsine was promising and had the value of 534.3 mg/g for the Cu content of 20 wt %, calcination temperature of 400 °C, pH of 10, oxygen concentration of 2%, and reaction temperature of 120 °C. The chemical and structural features of the initial and arsine-exposed sorbents were analyzed using the Brunauer–Emmett–Teller method, X-ray diffraction analysis, temperature-programmed desorption of carbon dioxide, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. It was found that the contents of anatase and rutile TiO2 in sorbents could be regulated by changing the pH of sorbents. Additionally, at pH of 1...

Reactivity of cyclohexene using ordered mesoporous materials based on calcined CoFeAl hydrotalcite-supported CoMo catalysts

Co2+, Fe3+ and Al3+ tertiary hydrotalcite-type solids were synthesized, calcined and impregnated with Mo (15 wt% MoO3) and Co (3Mo:Co) in order to get different catalytic precursors: CoMo/CoFeAl. As-synthesized hydrotalcites and their catalytic precursors were characterized by different physicochemical techniques, such as: X-ray fluorescence, N2 adsorption–desorption isotherms (BET specific surface area, BJH pore volume and diameter), Fourier transform infrared spectroscopy, X-ray diffraction and temperature-programmed desorption of carbon dioxide. These CoMo/CoFeAl catalytic precursors were previously pre-sulfided with CS2 and tested in the cyclohexene hydrogenation reaction. Results indicated that these sulfide catalysts showed very low activity in comparison with the conventional CoMo/Al2O3 catalyst used as reference, possibly to their high basicity. These catalysts could have the advantage of retaining the octane number of gasoline, by low hydrogenation of olefins.

Ionic Liquid-Assisted Synthesis of Mesoporous Carbons with Surface-Enriched Nitrogen for the Hydrogen Evolution Reaction.

Heteroatom-doped carbon materials are promising metal-free catalysts for the hydrogen evolution reaction (HER) at low voltage with high durability. However, many of the active sites introduced by heteroatom doping are hardly accessible within the bulk carbon structure and consequently contribute little to the catalytic activity. Here we report a facile ionic liquid-assisted method for synthesizing mesoporous nitrogen-doped carbons, enabling enrichment of nitrogen atoms at the pore surface, demonstrated by X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption of carbon dioxide (CO2-TPD). The resulting metal-free nitrogen-doped mesoporous carbons exhibit a remarkable electrocatalytic activity in HER. The accessible and efficient utilization of nitrogen atoms is responsible for the superior HER catalytic activity.

Enhanced CO2 Adsorption Performance on Hierarchical Porous ZSM-5 Zeolite

Hierarchical porous ZSM-5 (HP-ZSM-5) was constructed using organosilanes as the growth inhibitors for CO2 capture. The properties of adsorbents were characterized by X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, temperature-programmed desorption of carbon dioxide, and 27Al magic angle spinning nuclear magnetic resonance. It was found that HP-ZSM-5 samples synthesized by organosilanes had a significant effect on the microstructure and morphology. CO2 adsorption capacity of HP-ZSM-5 was up to 58.26 cm3 g–1 at 0 °C and 1 bar, significantly higher than that of the ZSM-5 sample. The effective improvement of CO2 adsorption performance mainly originated from the micro-/mesoporous composite structure and complex surface morphology, which can provide low-resistant pathways for CO2 through the porous network. Besides, in situ Fourier transform infrared spectroscopy was carried out to study the adsorption process on adsorbents, and the results indicated that a faster physical adsorption ...

Cleaner hydrothermal hydrogenolysis of glycerol to 1,2-propanediol over Cu/oxide catalysts without addition of external hydrogen

The hydrogenolysis of glycerol is considered a sustainable process to produce 1,2-propanediol (1,2-PDO). However, the development of a cost-effective solid catalyst and a cleaner process minus the addition of external hydrogen remains a challenge. In the present work, a series of Cu/oxide (SiO2, MgO, Al2O3, and ZnO) catalysts were prepared and evaluated for the hydrothermal hydrogenolysis of glycerol. The relationships of structure-catalytic properties were probed by thermogravimetric analysis (TG), powder X-ray diffraction (XRD), nitrogen adsorption-desorption, temperature-programmed desorption of carbon dioxide (CO2-TPD), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS). The catalytic activity of Cu/oxide catalysts was in the order of Cu/Al2O3<Cu/SiO2≈Cu/ZnO<Cu/MgO. The Cu/MgO catalysts were identified as highly active catalysts for the hydrothermal hydrogenolysis of glycerol under autogenic pressure without the addition of external hydrogen. When 1.0g Cu/MgO (Cu/MgO=0.5, molar ratio) catalyst and 50g 20wt% aqueous glycerol solution as the feedstock was loaded in a batch autoclave reactor, the conversion of glycerol reached 55% with a selectivity of 68% to 1,2-propanediol at 473K after 6h. Cu0 was identified as the active species both for the catalytic in situ aqueous-phase reforming of glycerol and for the hydrothermal hydrogenolysis of glycerol. The support basicity played a role in stabilizing the Cu nanoparticles on the support surface. During the catalytic reaction, part of Cu species leached from the MgO support into solvent and meanwhile part of Cu species on the support surface aggregated. The basicity and acidity of the solvent affected the behavior of the Cu/MgO catalysts. This work shows that hydrothermal hydrogenolysis process of glycerol is a facile process and the cost-effective Cu/MgO is worth further development for future industrial practice.

Characterization and parametric study of mesoporous calcium titanate catalyst for transesterification of waste cooking oil into biodiesel

Mesoporous calcium titanate (MCT) catalyst was synthesized via a sol-gel-hydrothermal method and investigated as a catalyst for biodiesel production from waste cooking oil (WCO). Calcium was supported on titanate in order to increase their surface area, stability and consequently, improve its performance in the transesterification of WCO to biodiesel. Synthesized catalyst was characterized with powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), N2 physisorption, Fourier transform-infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and carbon dioxide temperature-programmed desorption (CO2-TPD). The catalyst possessed high surface area, basicity and stability than calcium oxide (CaO) catalyst. The highest biodiesel yield achieved was 80.0% in 3:1 of methanol to WCO molar ratio, 0.2wt.% of MCT catalyst for 1h at 65°C. Reusability study suggested that this catalyst can be recycled for five successive runs.

CO2 methanation and co-methanation of CO and CO2 over Mn-promoted Ni/Al2O3 catalysts

A series of Mn-promoted 15 wt-% Ni/Al2O3 catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al2O3 catalysts for CO2 methanation and the comethanation of CO and CO2 in a fixed-bed reactor was investigated. The catalysts were characterized by N2 physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and highresolution transmission electron microscopy. The presence of Mn increased the number of CO2 adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al2O3 catalysts had improved CO2 methanation activity especially at low temperatures (250 to 400 °C). The Mn content was varied from 0.86% to 2.54% and the best CO2 conversion was achieved with the 1.71Mn-Ni/Al2O3 catalyst. The co-methanation tests on the 1.71Mn-Ni/Al2O3 catalyst indicated that adding Mn markedly enhanced the CO2 methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO2 methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process.

A cataluminescence sensor with fast response to diethyl ether based on layered double oxide nanoparticles.

This work proposed a cataluminescence (CTL) sensor for rapid and highly selective detection of diethyl ether using Mg-Al-layered double oxide (Mg-Al LDO). The linear range of the CTL intensity versus the concentration of diethyl ether was 0.1-8.0mM, with a correlation coefficient (R) of 0.9915. The limit of detection (signal-to-noise ratio (S/N) = 3) was 0.02mM. The half decay time was ~15s, indicating a fast CTL process. The CTL sensor showed an excellent selectivity toward diethyl ether and good operational stability. Relative standard deviation (RSD) was less than 3% in 20 consecutive measurements for diethyl ether. The CTL process was monitored by gas chromatography-mass spectrometry (GC/MS), pH indicator, and CTL spectrum. The results showed that the strong CTL signals were from the specific basic sites of Mg-Al LDO nanoparticle, which was further confirmed by temperature-programmed desorption of carbon dioxide (CO2-TPD). This work not only provides a facile approach to obtain a CTL sensor based on LDO but also systematically investigates the catalytic mechanism of LDO. Graphical abstract ᅟ.

Montmorillonite-supported KF/CaO: a new solid base catalyst for biodiesel production

Biodiesel is an alternative to petroleum-derived diesel fuel; development of a high-efficiency base catalyst to be used in heterogeneous biodiesel production is still a challenge. In this paper, a novel solid base catalyst, KF- and CaO-supported montmorillonite (KCa/MMT) was successfully synthesized by a facile impregnation method, and used for producing biodiesel in transesterification of commercial soybean oil with methanol. The catalysts were characterized by X-ray diffraction, carbon dioxide temperature-programmed desorption and scanning electron microscopy. Effects of the parameters, such as the loading amount of KF, the amount of KCa/MMT, and the methanol to oil molar ratios, on the yield of biodiesel were investigated. A maximum biodiesel yield of 98 % was obtained under the optimal reaction conditions. The separated catalyst can be directly used in the next round of reactions and gave a satisfactory yield. Furthermore, analysis of the catalyst's tolerance to oil-containing water or free fatty acids, and a kinetic study were also carried out. Koros–Nowak tests were designed and conducted, and it was proven that the heat and mass transfer were not limited by the reaction rate.

Surface Characteristics of Porous Coconut Shell Carbon Impregnated with Bimetallic Catalysts

Selective Catalytic Reduction catalyst (Cu-Mn/CSC) was derived from coconut shell carbon (CSC). The bimetallic catalysts, Copper and Manganese (Cu-Mn), were deposited onto CSC using wet impregnation technique while the calcination stage was performed under low temperature ambient air. The samples were then characterized using nitrogen adsorption-and-desorption, carbon dioxide temperature-programmed desorption, ammonia temperature-programmed desorption, hydrogen temperature-programmed reduction as well as scanning electron microscopy. The results showed that the synthesis process increased the external surface area and regulated the distribution of slit-shape pores on Cu-Mn/CSC. Besides, Cu-Mn was found to be reduced and the surface has more acidic groups compared to basic. These findings indicated the potential of using CSC as a precursor for NOx-Selective Catalytic Reduction catalyst.

Preparation of Novel Ethylene Glycol Monomethyl Ether Fatty Acid Monoester Biodiesel Using Calcined Sodium Silicate

A series of ethylene glycol monomethyl ether (EGME) fatty acid monoesters were prepared by the transesterification of different fatty acid methyl esters (FAMEs) with EGME. A solid basic catalyst, namely, calcined sodium silicate, was used. Various parameters, such as the calcination temperature, amount of catalyst, molar ratio of FAME/EGME, reaction temperature, and time on the yield of EGMEML (ML = methyl laurate), were optimized; the reusability of calcined sodium silicate was also examined. Calcined sodium silicate was also used as a catalyst for examining the catalytic activity of soybean oil biodiesel with EGME. Thermogravimetry, X-ray diffraction, carbon dioxide temperature-programmed desorption, Fourier transform infrared spectroscopy, and scanning electron microscopy were employed to characterize the properties of calcined sodium silicate. The results indicated that calcined sodium silicate was effective for the synthesis of novel biodiesel by FAMEs, with EGME as reactants. Centrifugation and deca...

Modified Cuo/ZnO/Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Catalysts for Methanol Synthesis from Co and CO&lt;sub&gt;2&lt;/sub&gt; Co-Hydrogenation

A series of CuO-ZnO-Al2O3catalysts modified by different promoter were prepared by co-precipitation or incipient wet impregnation and characterized by X-ray diffraction (XRD), N2physisorption, hydrogen temperature-programmed reduction (H2-TPR) and carbon dioxide temperature-programmed desorption (CO2-TPD). The modified catalysts were tested for methanol synthesis from CO/CO2co-hydrogenation in a fixed bed reactor with feed containing CO, CO2and H2(CO:CO2:H2=1.0:1.08:6.24, volume radio). It is revealed that the catalysts modified by Zr, Mg, Ca has higher activity of methanol synthesis by CO and CO2co-hydrogenation. Especially, the addition of Zr enhances the conversion of total carbon and the selectivity of methanol, which is due to the improved surface area, much more active sites, and the synergistically interaction between CuO and ZnO caused by the addition of Zr promoter.

Carbon dioxide reforming of methane for syngas production over La-promoted NiMgAl catalysts derived from hydrotalcites

La-promoted NiMgAl mixed-oxide catalysts derived from hydrotalcite were synthesized by coprecipitation for the carbon dioxide reforming of methane. X-ray diffraction, thermogravimetric analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy, temperature-programmed desorption of carbon dioxide, hydrogen chemisorption and transmission electron microscopy were used to investigate the structure and deactivation characteristics of the catalysts. The catalysts exhibited a narrow Ni-metal particle-size distribution between 5 and 11nm. The presence of lanthanum evidently improved reforming activity in the temperature range of 600–700°C, because the introduction of lanthanum into the NiMgAl catalysts increased the total amount of basic sites and the surface Ni content. The activity of the Ni0.5Mg2.5Al0.9La0.1O4.5 catalyst was slightly higher than those of the other lanthanum-containing catalysts. The addition of lanthanum improved the stability of the NiMgAl catalysts significantly because of the suppression of coke deposition. Lanthanum effectively inhibited coking by increasing the basicity of the catalysts, forming the La2O2CO3 phase and improving nickel metal dispersion.