CO2 Temperature-programmed Desorption Research Articles

Facet-Dependent selectivity of CeO2 nanoparticles in 2-Propanol conversion

CeO2 nanoshapes, cubes with dominant (100) facets and octahedra with dominant (111) facets, were synthesized to investigate the influence of surface structure on acid-base properties. An optimization of calcination temperatures, coupled with Raman and TEM, was employed to minimize the intrinsic (Frenkel-type) defect sites and their potential complications on the facet studies involved in this work. The acid-base properties of these CeO2 nanoshapes were characterized with in situ pyridine and CO2 adsorption using infrared spectroscopy and quantified using pyridine, ammonia, and CO2 temperature-programmed desorption (TPD). The (100) facet displayed weaker acid sites with lower site density than the (111) facet which had a similar density of base sites but those on the (100) facet were stronger. A strong correlation was observed between 2-propanol conversion and each facet’s acid-base properties. CeO2 cubes exhibited greater base-site catalyzed dehydrogenation to acetone while the more acidic CeO2 octahedra were more active in dehydration to propene.

Bimetallic metal organic framework-templated synthesis of a Cu-ZnO/Al2O3 catalyst with superior methanol selectivity for CO2 hydrogenation

It is highly desirable to develop inexpensive and highly selective catalyst for CO2 hydrogenation to methanol and Cu/ZnO/Al2O3 is a promising formulation. Herein, we report the design and synthesis of a Cu-ZnO/Al2O3 catalyst via a bimetallic metal organic framework (MOF)-templated strategy (termed Cu-ZnOMOF⊂Al2O3) and shed light on the role of the Cu-Zn@MOF precursor in this system for methanol synthesis. The developed Cu-ZnOMOF⊂Al2O3 exhibited high methanol selectivity (86.9%) and methanol space-time yield (407.2 gMeOH•kgcat−1•h−1) at higher CO2 conversion (9.1%) in comparison with the conventional Cu-ZnONO3/Al2O3 catalyst (79.6% and 209.0 gMeOH•kgcat−1•h−1, and 5.1%, respectively) at 240 ºC under 3.0 MPa. Spectroscopic characterization (TEM, XPS, EDX, in-situ DRIFTS) coupled with N2O chemisorption and temperature-programmed desorption of CO2 and H2 revealed that the surface of the new Cu-ZnOMOF⊂Al2O3 catalyst possesses higher Cu dispersion, surface-enriched ZnO and more Cu-ZnO interfacial sites, which leads to higher capability for CO2 and H2 adsorption and activation. These are considered to be the origin of higher methanol selectivity and enhanced activity of the catalyst prepared by the MOF-templated strategy for CO2 hydrogenation. This work offers a novel approach to optimizing Cu-ZnO/Al2O3 catalyst for CO2 hydrogenation to methanol.

LOHC-bound hydrogen for catalytic NOx reduction from O2-rich exhaust gas

The present study demonstrates a novel method for the NOx reduction by H2 in lean exhaust gases using H2 released from a Liquid Organic Hydrogen Carrier (LOHC). The concept implies the simultaneous H2 production and H2-deNOx reaction, which both take place on the same catalyst. In a first approach, the catalyst was suspended in the LOHC, while the exhaust flowed through the slurry. The experiments performed with a O2-rich model exhaust and perhydro dibenzyltoluene as LOHC as well as Pd/C, Pt/C and Pt/Al2O3 catalysts evidenced the feasibility of this transfer hydrogenation. As a result, the Pd/C catalyst revealed best H2-deNOx performance providing NOx conversions up to 98% above 200 °C with almost selective N2 formation. The characterization of the catalysts by temperature-programmed desorption of CO suggested that the superiority of the Pd/C sample is associated with its pronounced number of active Pd sites. Furthermore, the investigations also showed some LOHC degradation during the exposure to the lean model exhaust yielding CO, CO2 and hydrocarbons.

Magnesium Impregnated on NaX Zeolite Synthesized from Cogon Grass Silica for Fast Production of Fructose via Microwave-Assisted Catalytic Glucose Isomerization

Fructose is a crucial intermediate in the production of several chemical platforms. Fructose is mainly produced from glucose isomerization either through immobilized enzymes or heterogeneous catalysts using a conventional heating source, and this is time-consuming. Thus, this work discloses a fast production of fructose via microwave-assisted catalytic glucose isomerization using Mg catalysts supported on NaX zeolite from cogon grass silica. The catalysts were prepared by the impregnation of magnesium nitrate solution and subsequently transformed into MgO on NaX by calcination. The effect of 3, 6 and 9 wt.% Mg content on NaX on the performance of glucose isomerized to fructose was tested at 90 °C for 15 min. The best catalyst was selected for studying the effect of reaction times of 5, 15, 30 and 60 min. Results from X-ray diffraction (XRD), N2 sorption and CO2 temperature-programmed desorption (CO2-TPD) suggested that crystallinity, surface area and micropore volume decrease but basicity increases with Mg content. The X-ray photoelectron spectroscopy (XPS) result confirmed the presence of mixed phases of MgO and Mg2CO3 in all catalysts. The glucose conversion enhanced with the Mg loading but the fructose yield gave the highest value with Mg of 6 wt.%, probably due to the tuning of high active sites and surface area. The greatest fructose selectivity and yield (71.9% and 25.8%) were obtained within 15 min by microwave-assisted catalytic reaction, shorter than the reported value in the literature, indicating a suitable reaction time. Mg (6 wt.%)/NaX catalyst preserves the original catalytic performance up to three cycles, indicating that it is a promising catalyst for fructose production.

Reduction of NOx by H2 on WOx-Promoted Pt/Al2O3/SiO2 Catalysts Under O2-Rich Conditions

This work addresses the reduction of NOx by H2 under O2-rich conditions using Al2O3/SiO2-supported Pt catalysts with different loads of WOx promotor. The samples were thoroughly characterised by N2 physisorption, temperature-programmed desorption of CO, scanning electron microscopy, X-ray diffraction, laser raman spectroscopy, X-ray photoelectron spectroscopy and diffuse reflectance infrared fourier transform spectroscopy with probe molecule CO. The catalytic studies of the samples without WOx showed pronounced NOx conversion below 200 °C, whereas highest efficiency was related to small Pt particles. The introduction of WOx provided increasing deNOx activity as well as N2 selectivity. This promoting effect was referred to an additional reaction path at the Pt-WOx/Al2O3/SiO2 interface, whereas an electronic activation of Pt by strong metal support interaction was excluded.Graphic

Tailoring the yttrium content in Ni-Ce-Y/SBA-15 mesoporous silicas for CO2 methanation

A series of nickel-cerium-promoted mesoporous silica (SBA-15) catalysts modified with different loadings of yttrium were synthesized by cetyltrimethylammonium bromide (CTAB)-assisted impregnation. The catalysts were tested in CO2 methanation reaction and characterized by N2 sorption, X-ray fluorescence (XRF), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (XRD), H2 chemisorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), CO2 temperature-programmed desorption (CO2-TPD), and thermogravimetric analysis coupled with mass spectrometry (TGA-MS). The best catalytic performance in CO2 methanation was found for Y-modified NiCe/SBA-15 catalysts compared to the unpromoted sample. The modification with 10 wt% of yttrium gave the highest CO2 conversion of 61% ± 2% at 350 °C. We attribute this increase to an improved dispersion of Ni, increased reducibility of Ni species, higher ratio of Ce3+/(Ce3+ + Ce4+), and increased moderate basicity found for 15Ni10Ce10Y/SBA-15. This paper shows that 10 wt% of Y loading not only improves the catalytic activity in CO2 methanation, but also gives stable performance. The tested 15Ni10Ce10Y/SBA-15 catalyst did not exhibit activity loss during 26 h of time-on-stream (TOS) experiment at 350 °C. Moreover, carbon deposits and sintered nickel particles could hardly be found in 15Ni10Ce10Y/SBA-15 catalyst used for 7 h.

Characterization of Ibuprofen-Loaded MgO by One-Step Mid- and Far-FT-IR Spectroscopy.

One-step mid- and far-Fourier-transform (FT)-IR spectroscopy is a facile and powerful tool that provides various information regarding chemical and crystal states. However, its potentially high applicability has not been sufficiently demonstrated. In the present study, ibuprofen (IB)-loaded MgO samples are prepared via different methods, and they are evaluated using scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction analysis (XRD), N2 adsorption-desorption measurement, CO2 temperature-programmed desorption technique (CO2-TPD), and FT-IR spectroscopy. The obtained results indicate that IB becomes ionized, amorphous, and/or dispersed by using MgO. Since the CO2-TPD result shows that MgO possesses basic surfaces, it is considerable that acid-base interactions cause the above different chemical states. Furthermore, the FT-IR spectra in mid- and far-IR regions also suggest that the above physical and chemical properties of IB-loaded MgO changes through the interactions. Therefore, the characterization results suggest that one-step mid- and far-FT-IR measurements can provide valuable information regarding the chemical and crystal states.

Using shrimp shells as based catalysts for FAME production from palm oil feedstock

In this study, waste shrimp shells from industry were used as a heterogeneous bio-based catalyst for trans-esterification reaction of fresh palm oil. CaO was prepared from shrimp shells calcination. Surface area, phase composition, and basicity of the calcined shrimp shell catalysts were studied using N2 adsorption (BET), X-ray diffraction (XRD), and CO2 temperature-programmed-desorption (CO2-TPD), respectively. The influence of shrimp shells calcination temperature and operation condition, methanol to palm oil ratio on trans-esterification reaction, were investigated. Five hours trans-esterification was carried out at 65℃ using different shrimp shell at four different calcination temperature: 700, 750, 800 and 850℃ with 9:1 methanol to palm oil ratio to determine the suitable calcined catalyst with the highest FAME yield. Methanol to palm oil ratios were varied from 6:1, 9:1, 12:1 and 15:1 with the selected catalyst. According to the results, the highest basic strength of mixed CaO and hydroxy-apatite phases were received by 800℃ calcined shrimp shell catalyst, with the highest FAME yield of 87.54% under the optimum condition reaction: 65℃ reaction temperature, 5 h reaction time, 9 wt% catalyst loading, and 9:1 methanol to palm oil ratio.

Neighboring Zn-Zr Sites in a Metal-Organic Framework for CO2 Hydrogenation.

ZrZnOx is active in catalyzing carbon dioxide (CO2) hydrogenation to methanol (MeOH) via a synergy between ZnOx and ZrOx. Here we report the construction of Zn2+-O-Zr4+ sites in a metal-organic framework (MOF) to reveal insights into the structural requirement for MeOH production. The Zn2+-O-Zr4+ sites are obtained by postsynthetic treatment of Zr6(μ3-O)4(μ3-OH)4 nodes of MOF-808 by ZnEt2 and a mild thermal treatment to remove capping ligands and afford exposed metal sites for catalysis. The resultant MOF-808-Zn catalyst exhibits >99% MeOH selectivity in CO2 hydrogenation at 250 °C and a high space-time yield of up to 190.7 mgMeOH gZn-1 h-1. The catalytic activity is stable for at least 100 h. X-ray absorption spectroscopy (XAS) analyses indicate the presence of Zn2+-O-Zr4+ centers instead of ZnmOn clusters. Temperature-programmed desorption (TPD) of hydrogen and H/D exchange tests show the activation of H2 by Zn2+ centers. Open Zr4+ sites are also critical, as Zn2+ centers supported on Zr-based nodes of other MOFs without open Zr4+ sites fail to produce MeOH. TPD of CO2 reveals the importance of bicarbonate decomposition under reaction conditions in generating open Zr4+ sites for CO2 activation. The well-defined local structures of metal-oxo nodes in MOFs provide a unique opportunity to elucidate structural details of bifunctional catalytic centers.

Effects of rhodium catalyst support and particle size on dry reforming of methane at moderate temperatures

• Dry reforming of methane at 400–600 °C over supported Rh catalysts was studied. • Catalyst activity depended on Rh particle size, support type, and acidic properties. • Specific activity increased with decreasing Rh particle size. • Rh/SiO 2 -TiO 2 performed the best, giving H 2 and CO yields of 1.8% and 4.2% at 400 °C. • Electron-deficient Rh δ+ species may improve the specific activity of the catalysts. Dry reforming of methane at 400–600°C was studied over Rh catalysts with different supports (SiO 2 , γ-Al 2 O 3 , α-Al 2 O 3 , TiO 2 , ZrO 2 , CeO 2 , Y 2 O 3 , SiO 2 -Al 2 O 3 , SiO 2 -MgO, SiO 2 -TiO 2 ), Rh particle sizes (1.5–15.6 nm), and acidic properties (acidic site density, 0.37–3.40 mmol g −1 ). Catalysts with a high density of strongly acidic sites (e.g., α-Al 2 O 3 , SiO 2 -MgO) showed low activity and gradually deactivated with time on stream; in contrast, catalysts with a low density of strongly acidic sites (e.g., TiO 2 , γ-Al 2 O 3 ) showed high, stable activity. Rh/SiO 2 -TiO 2 showed the best performance, with H 2 and CO yields of 1.8% and 4.2% at 400°C and yields 37.3% and 53.1% at 600°C, respectively. Catalyst activity depended strongly on Rh particle size; specific activity increased with decreasing particle size, indicating that Rh-catalyzed dry reforming of methane is structure-sensitive. The support type influenced not only the dispersion and reducibility of the Rh particles but also the specific activity of the catalysts. CO temperature-programmed desorption and FT-IR suggested that electron-deficient Rh δ+ species were generated by electronic interactions between the Rh particles and the support, and the number of these species strongly influenced the overall catalytic activity.

Cu/HZSM-5 Sorbent Treated by NH3 Plasma for Low-Temperature Simultaneous Adsorption-Oxidation of H2S and PH3.

In this study, an NH3 plasma-treated Cu/HZSM-5 sorbent was introduced to simultaneously remove H2S and PH3 in low-temperature and low-oxygen environments. The effects of the Cu loading amounts, modification methods, and plasma-treatment conditions on the adsorption-oxidation performance of the sorbents were investigated. From the performance test results, the sorbent treated by NH3 plasma with the specific energy input (SEI, electrical input energy to the unit volume of gas) value of 1 J·mL-1 (Cu/HZSM-5-[S1]) was identified as having the highest breakthrough capacities of 108.9 mg S·g-1 and 150.9 mg P·g-1 among all of the materials tested. After three times of regeneration, the sorbent can still maintain the ideal performance. The results of Fourier transform infrared (FT-IR) spectroscopy and CO2 temperature-programmed desorption (CO2-TPD) indicated that the NH3 plasma treatment can introduce amino groups (functional groups) onto the sorbent surface, which greatly increases the number and strength of the basic sites on the sorbent surface. Results of N2 adsorption/desorption isotherms and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) showed that the morphology of the sorbent changed after the plasma treatment, which exposed more active sites (copper species). In situ IR spectra showed that the amino groups are continuously consumed during the reaction process, indicating that these amino groups can help sorbents to capture gas molecules. Moreover, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses indicated that CuO is the main active species and the consumption of CuO and accumulation of the reaction products on the surface and inner pores of the sorbent are the primary reasons for the deactivation of the sorbent.

Tuning the intermediate reaction barriers by a CuPd catalyst to improve the selectivity of CO2 electroreduction to C2 products

Electrochemical CO2 reduction is a promising strategy for the utilization of CO2 and intermittent excess electricity. Cu is the only single metal catalyst that can electrochemically convert CO2 into multicarbon products. However, Cu exhibits an unfavorable activity and selectivity for the generation of C2 products because of the insufficient amount of CO* provided for the C-C coupling. Based on the strong CO2 adsorption and ultrafast reaction kinetics of CO* formation on Pd, an intimate CuPd(100) interface was designed to lower the intermediate reaction barriers and improve the efficiency of C2 product formation. Density functional theory (DFT) calculations showed that the CuPd(100) interface enhanced the CO2 adsorption and decreased the CO2* hydrogenation energy barrier, which was beneficial for the C-C coupling. The potential-determining step (PDS) barrier of CO2 to C2 products on the CuPd(100) interface was 0.61 eV, which was lower than that on Cu(100) (0.72 eV). Encouraged by the DFT calculation results, the CuPd(100) interface catalyst was prepared by a facile chemical solution method and characterized by transmission electron microscopy. CO2 temperature-programmed desorption and gas sensor experiments further confirmed the enhancement of the CO2 adsorption and CO2* hydrogenation ability of the CuPd(100) interface catalyst. Specifically, the obtained CuPd(100) interface catalyst exhibited a C2 Faradaic efficiency of 50.3% ± 1.2% at −1.4 VRHE in 0.1 M KHCO3, which was 2.1 times higher than that of the Cu catalyst (23.6% ± 1.5%). This study provides the basis for the rational design of Cu-based electrocatalysts for the generation of multicarbon products by fine-tuning the intermediate reaction barriers.

Enhanced CO2 methanation activity over Ni/CeO2 catalyst by one-pot method

Abstract Carbon dioxide hydrogenation for value-added chemicals has been regarded as a promising way for CO2 utilization. This paper describes the preparation of Ni/CeO2 catalysts derived from Ce-MOF precursor by impregnation or one-pot method and their application in carbon dioxide methanation. Various techniques were employed to characterize the prepared catalysts, including N2 adsorption–desorption, X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (SEM), H2-temperature programmed reduction (H2-TPR), H2-temperature programmed desorption (H2-TPD) and CO2-temperature programmed desorption (CO2-TPD). The results showed that compared with commercial CeO2 and CeO2 prepared by precipitation, CeO2 derived from Ce-MOF exhibited more oxygen vacancies and lower temperature reducibility, making it more beneficial for the adsorption and activation of CO2. Consequently, nickel supported on rod-shaped CeO2 derived from Ce-MOF exhibited higher CO2 conversion and methane selectivity at low temperatures. Furthermore, the Ni/CeO2−M-1 catalysts prepared by one-pot method showed superior activity since nickel could be partially incorporated into ceria lattice, leading to the formation of Ce1-xNixO2-y solid solutions and oxygen vacancies. The effect of nickel loading on the properties of the catalysts by one-pot method was also investigated, and the optimum Ni loading was 15 wt.% owing to the maximum number of oxygen vacancies being reached.

High-performance flake-like mesoporous magnesium oxide prepared by eggshell membrane template for carbon dioxide capture

The utilization of eggshell membrane (ESM) as a template can improve the structural properties of the synthesised adsorbent, further affecting its CO2 uptake capacity. In this study, a flake-like shape mesoporous magnesium oxide (MgO) adsorbent was synthesised via the ESM bio-templating method to form MgO-BT. The prepared adsorbents were characterised by field emission scanning electron microscopy equipped with an energy-dispersive X-ray (FESEM-EDX), X-ray diffraction (XRD), N2 physisorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and CO2-temperature programmed desorption (CO2-TPD). The flake-like shape MgO-BT possesses an improved surface area of 79 m2/g, which is higher than the MgO adsorbent prepared by the thermal decomposition method (MgO-TD). Also, ESM bio-templating method has resulted in the increase of MgO-BT's basic site which mainly composed of strong-basic attachment site. These improved MgO-BT's structural properties have led to the increased CO2 uptake capacity of 1.55 ​mmol/g, which is 6-times higher than MgO-TD (0.23 ​mmol/g) at ambient temperature and pressure under 100% CO2 flow condition. Moreover, under flue gas conditions, the MgO-BT has demonstrated a slight reduction in CO2 uptake (~15%), however, this value is still tremendously higher than MgO-TD. It can be concluded that the utilization of ESM as a bio-template in the MgO preparation stage has significantly influenced the physicochemical properties of the adsorbent, therefore leading to a high CO2 adsorption performance.

Characteristics and activity of Ni/CeO<sub>2</sub> catalyst modified by Cr<sub>2</sub>O<sub>3</sub> in combined steam and CO2 reforming of CH4

A series of 10%wtNiO/CeO2-nanorod catalyst without and with Cr2O3 additive was prepared by simultaneous impregnation method. Several techniques, including N2 physisorption measurements, X-ray powder diffraction (XRD), temperature-programmed reduction using H2 (H2-TPR), CO2 temperature-programmed desorption (CO2-TPD), scanning electron microscope (SEM) and transmission electron microscopy (TEM) were used to investigate catalysts’ physico-chemical properties. The activity of the catalysts in combined steam and CO2 reforming of CH4 (BRM) was investigated at temperature range of 550-800 °C. The results showed that 10%NiO0.1%Cr2O3/CeO2 catalyst had the best catalytic performance due to a better reducibility and basicity. At 700 °C and CH4:CO2:H2O molar ratio in feed stream of 3:1.2:2.4, both conversion of CH4 and CO2 on this catalyst reached 98.5%.

Mono‐ and Bimetallic Ni−Co Catalysts in Dry Reforming of Methane

AbstractSeveral bimetallic Ni−Co catalysts supported on θ‐Al2O3 together with 10 wt % Ni and 10 wt % Co on θ‐Al2O3 were prepared via the incipient wetness method, characterized by X‐ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy, temperature programmed reduction, temperature programmed CO2 desorption, Fourier Transformed Infrared Spectroscopy (FTIR) with pyridine adsorption‐desorption and tested in dry methane reforming at 700 °C in a fixed bed reactor. According to XRD the metal oxide crystallite sizes decreased from 20 nm for 10 wt % Co/θ‐Al2O3 to 13 nm for 5 wt % Ni‐5 wt % Co/θ‐Al2O3, which also showed formation of a mixed oxide alloy. The unit cell parameters for spinel in the fresh catalyst and fcc metal formed during the reaction followed the Vegard's rule. Although monometallic 10 wt % Co/θ‐Al2O3 exhibited high hydrogen consumption, desorption temperature was also high resulting in a rather low activity of 10 wt % Co/θ‐Al2O3 in comparison to bimetallic 5 wt % Ni‐5 wt % Co/θ‐Al2O3. The latter exhibited the highest initial activity for hydrogen formation due to its relatively small metal particle size. This catalyst suffered, however, from extensive coking. The most stable catalyst was 10 wt % Ni/θ‐Al2O3 for which the hydrogen yield decreased form 56 % to 45 % during 100 h time‐on‐stream. For this catalyst no sintering occurred, opposite to 10 wt % Co/θ‐Al2O3.

MnO2 polymorphs for catalytic carboxylation of 1-butanamine by CO2

N,N′-dibutylurea is an important fine chemical/intermediate with a wide range of applications. Here, the synthesis of N,N′-dibutylurea through catalytic carbonylation of 1-butanamine by CO2 over MnO2 heterogeneous catalysts was systematically investigated. Four polymorphs of MnO2, including α-MnO2, β-MnO2, δ-MnO2 and γ-MnO2 with various morphological shapes were synthesized by hydrothermal method through altering the synthesis conditions (raw materials or parameters). Significant impact of the lattice structure of the MnO2 oxides on the catalytic activity was demonstrated. Among them, δ-MnO2 possessed the most favorable catalytic activity with N,N′-dibutylurea yield as high as 85.78 % at 160 °C for 24 h in CO2, while it is only 76.70 % for the α-MnO2, although they showed the similar specific surface area of around 10 m2 g−1. To understand the different catalytic behaviors among the different structured MnO2, the catalysts were characterized by X-ray photoelectron spectroscopy and temperature-programmed desorption of CO2. It was discovered that the excellent performance of δ-MnO2 was ascribed to its high surface basicity from its high concentration of lattice oxygen on surface of MnO2, while the large amount of surface unsaturated coordination manganese also positively affected the catalytic performance of γ-MnO2. It suggests enhancement of surface basicity and defect concentration is critical for the development of superior MnO2-based catalysts for the green synthesis of N,N′-dibutylurea from catalytic carbonylation of 1-butanamine by CO2.

Synthesis of magnetic basic palm kernel shell catalyst for biodiesel production and characterisation and optimisation by Taguchi method

This paper illustrated the latest breakthroughs which involved the use of eco-friendly and recyclable magnetic palm kernel shell-derived catalysts (Fe-PKS and Fe-KOH-PKS) for methanolysis of palm oil to produce biodiesel. The magnetic catalyst is obtained from abundant carbon-based biomass, i.e. waste palm kernel shell using pyrolysis. Characterisation of the catalyst with field-emission Scanning Electron microscopy (FESEM), energy-dispersive X-Ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM), temperature-programmed desorption of CO2 (TPD-CO2) thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) analysis was conducted to correlate the catalyst characteristic with transesterification activity. The presence of KOH in the catalyst has beneficial effects on the catalyst performance in transesterification. Next, the L-9 orthogonal set-up of experimental factors established by the Taguchi method was employed to determine the optimal operating conditions for Fe-KOH-PKS catalyst. The highest biodiesel yield of 99.43% using Fe-KOH-PKS catalyst was achieved with optimal operating conditions of 7.5 wt% catalyst loading, 9:1 methanol to oil ratio at 65 °C after 2 h. The catalyst was reused for four cycles, with the final run of biodiesel yield of 70.1%. This reflects the synthesised magnetic waste catalyst from palm kernel shell has demonstrated satisfied reusability and good stability in producing biodiesel.

CO2 Methanation over Rare Earth Doped Ni-Based Mesoporous Ce0.8Zr0.2O2 with Enhanced Low-Temperature Activity

The Ni-based catalysts have a wide range of industrial applications due to its low cost, but its activity of CO2 methanation is not comparable to that of precious metal catalysts. In order to solve this problem, Ni-based mesoporous Ce0.8Zr0.2O2 solid solution catalysts doped with rare earth were prepared by the incipient impregnation method and directly used as catalysts for the methanation of CO2. The catalysts were characterized systematically by X-ray powder diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), energy-dispersed spectroscopy (EDS) mapping, X-ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2-TPR), CO2 temperature programmed desorption (CO2-TPD), and so on. The results show that Ni is highly dispersed in the mesoporous skeleton, forming a strong metal-skeleton interaction. Therefore, under the condition of CO2 methanation, the hot sintering of metallic Ni nanoparticles can be effectively inhibited so that these mesoporous catalysts have good stability without obvious deactivation. The rare earth doping can significantly increase the surface alkalinity of catalyst and enhance the chemisorption of CO2. In addition, the rare earth elements also act as electron modifiers to help activate CO2 molecules. Therefore, the rare earth doped Ni-based mesoporous Ce0.8Zr0.2O2 solid solution catalysts are expected to be an efficient catalyst for the methanation of CO2 at low-temperature.

Effect of electron tunneling through the oxide film grown on metal substrate upon the efficiency of molecular reaction over the oxide supported metal nanoparticles: A case of CO oxidation on Au/Al2O3/Mo(110)

Formation of gold nanosized particles supported by aluminum oxide film grown on Mo(110) substrate and oxidation of carbon monoxide molecules on their surface have been in-situ studied in ultra-high vacuum by means of Auger electron spectroscopy (AES), reflection-absorption infrared spectroscopy (RAIRS), low energy electron diffraction (LEED), atomic force microscopy (AFM), temperature programmed desorption (TPD) and work function measurements. The main focus was to follow how the thickness of the alumina film influences the efficiency of CO oxidation in an attempt to find out an evidence of possible effect of electron tunneling between the metal substrate and the Au particle through the oxide interlayer. Providing the largest degree of surface identity of the studied metal/oxide system at different thicknesses of the alumina film (2, 4, 6 and 8 monolayers), it was found that the CO oxidation efficiency, defined as CO2 to CO TPD peaks intensity ratio, as well as the activation energy of CO oxidation, exponentially depend upon the oxide film thickness. Taking into account the known fact that the CO oxidation efficiency depends on the amount of excess charge acquired by Au particle, the latter suggests that electron tunneling adds efficiency to the oxidation process, although not significantly.