Micromeritics Tristar II

Power to gas systems is one of the most interesting long-term energy storage solutions. As a result of the high exothermicity of the CO2 methanation reaction, the catalyst in the methanation subsystem is subjected to thermal stress. Therefore, the performance of a commercial Ni/Al2O3 catalyst was investigated over a series of 100 hour-long tests and in-process relevant conditions, i.e. 5 bar from 270 to 500 °C. Different characterization techniques were employed to determine the mechanism of the observed performance loss (N2 physisorption, XRD, TPO). The TPO analysis excluded carbon deposition as a possible cause of catalyst aging. The BET analysis evidenced a severe reduction in the total surface area for the catalyst samples tested at higher temperatures. Furthermore, a direct correlation was found between the catalyst activity decline and the drop of the catalyst specific surface. In order to correctly design a reliable methanation reactor, it is essential to have a kinetic model that includes also the aging kinetics. For this purpose, the second set of experiments was carried out, in order to determine the intrinsic kinetics of the catalyst. The kinetic parameters were identified by using nonlinear regression analysis. Finally, a power-law aging model was proposed to consider the performance loss in time.

Eduard Alexandru Morosanu, Fabio Salomone, Raffaele Pirone, Samir Bensaid. Catalysts, 10 (3), 283, 2020.

In this paper, a comprehensive study was carried out on the application of perovskite catalyst in dry reforming of CH4. The perovskite catalyst was prepared using a sol–gel method. The prepared samples were characterized by N2 adsorption/desorption, TPR, XRD, CO2-TPD, TGA, TPO, Raman, and SEM techniques. In addition, the effect of operating pressure, namely, 1 bar, 3 bar, 5 bar, and 7 bar, temperature (500–800 °C) was evaluated. The characterization results indicated that catalysts operated at 1 bar, gas hourly space velocity of 84000 (mL/g/h) gave the best catalytic performance. CH4 and CO2 conversions of 77 and 80% were obtained at 1 bar and at 700 °C reaction temperature. The increase of reaction temperatures from 500 °C to 800 °C increased the reaction rate and hence the methane and carbon dioxide conversions were increased. A unity ratio of H2/CO was obtained at 1 bar for temperatures 600 °C and above. Similarly, the time on stream tests, obtained at a 700 °C reaction temperature, showed that the best ratio in terms of the closeness of unity and the stable profile could be attained when the pressure was set to 1 bar. The TGA analysis showed the drop of mass due to oxidation of carbon deposits, which started at 500 °C. The catalyst operated at 1 bar produced the least amount of carbon, equivalent to 35% weight loss, while the 3 and 5 bar operated catalysts generated carbon formation, equivalent to 65% weight loss. However, the 7 bar operated catalyst resulted the highest accumulation of carbon formation, equivalent to 83% weight reduction. Hence, the TGA profile indicated the relative carbon deposition on the catalyst, which was dependent of the operated pressure and hence confirmed the suitability operation pressure of 1 bar. The characterizations of the Raman, EDX, TGA, and TPO all presented the formation of carbon.

Anis Hamza Fakeeha, Ahmed Sadeq Al-Fatesh, Jehad K. Abu-Dahrieh, Ahmed Aidid Ibrahim, Samsudeen Olajide Kasim, Ahmed Elhag Abasaeed. Catalysts, 10 (4), 379, 2020.

Three different Advanced Oxidation Processes (AOPs) have been investigated for the degradation of the imidacloprid pesticide in water: photocatalysis, Fenton and photo-Fenton reactions. For these tests, we have compared the performance of two types of CeO2, employed as a non-conventional photocatalyst/Fenton-like material. The first one has been prepared by chemical precipitation with KOH, while the second one has been obtained by exposing the as-synthetized CeO2 to solar irradiation in H2 stream. This latter treatment led to obtain a more defective CeO2 (coded as “grey CeO2”) with the formation of Ce3+ sites on the surface of CeO2, as determined by Raman and X-ray Photoelectron Spectroscopy (XPS) characterizations. This peculiar feature has been demonstrated as beneficial for the solar photo–Fenton reaction, with the best performance exhibited by the grey CeO2. On the contrary, the bare CeO2 showed a photocatalytic activity higher with respect to the grey CeO2, due to the higher exposed surface area and the lower band-gap. The easy synthetic procedures of CeO2 reported here, allows to tune and modify the physico-chemical properties of CeO2, allowing a choice of different CeO2 samples on the basis of the specific AOPs for water remediation. Furthermore, neither of the samples have shown any critical toxicity.

Roberto Fiorenza, Stefano Andrea Balsamo, Luisa D’Urso, Salvatore Sciré, Maria Violetta Brundo, Roberta Pecoraro, Elena Maria Scalisi, Vittorio Privitera, Giuliana Impellizzeri. Catalysts, 10 (4), 446, 2020.

The synergetic effects of Co oxides on the Ni/CoAl (NCA) catalysts were observed at an optimal molar ratio of Al/Co = 2 (NCA(2)) due to the partial formations of thermally stable spinel CoAl2O4 phases for the steam reforming of propane (SRP). The optimal content of the spinel CoAl2O4 phases on the NCA(2) was responsible for the formation of the relatively active oxophilic metallic Co nanoparticles with a smaller amount of less active NiAl2O4 on the surfaces by preserving the relative amount of metallic Co of 68% and 52% in the reduced and used catalysts, which enhanced the catalytic activity and stability with the largest specific rate of 1.37 C3H8/(Ni + Co)h−1 among the tested NCA catalysts. The larger or smaller amounts of Co metal on the less active NCA mainly caused the preferential formation of larger aggregated Ni nanoparticles ~16 nm in size due to their weaker interactions, or induced the smaller formations of active metal phases by selectively forming the spinel NiAl2O4 phases with ~60% in the NCA(4), resulting in a fast deactivation.

Kyung Soo Park, Min Hye Jeong, Jong Wook Bae. Catalysts, 10 (4), 461, 2020.

This study reports the catalytic properties of Ag nanoparticles dispersed on mixed ionic and electronic conducting layers of LSCF (La0.6Sr0.4Co0.2Fe0.8O3) for propene combustion. A commercial and a synthesized LSCF powder were deposited by screen-printing or spin-coating on dense yttria-stabilized zirconia (YSZ) substrates, an oxygen ion conductor. Equal loadings (50 µg) of Ag nanoparticles were dispersed via drop-casting on the LSCF layers. Electrochemical and catalytic properties have been investigated up to 300 °C with and without Ag in a propene/oxygen feed. The Ag nanoparticles do not influence the electrochemical reduction of oxygen, suggesting that the rate-determining step is the charge transfer at the triple phase boundaries YSZ/LSCF/gas. The anodic electrochemical performances correlate well with the catalytic activity for propene oxidation. This suggests that the diffusion of promoting oxygen ions from YSZ via LSCF grains can take place toward Ag nanoparticles and promote their catalytic activity. The best specific catalytic activity, achieved for a LSCF catalytic layer prepared by screen-printing from the commercial powder, is 800 times higher than that of a pure Ag screen-printed film.

Thai Giang Truong, Benjamin Rotonnelli, Mathilde Rieu, Jean-Paul Viricelle, Ioanna Kalaitzidou, Daniel Marinha, Laurence Burel, Angel Caravaca, Philippe Vernoux, Helena Kaper. Catalysts, 10 (7), 729, 2020.

A conventional Pt/CeO2/Al2O3 catalyst physically mixed with an ionic conductor (Mo- or Eu-doped ZrO2) was tested at high space velocity (20,000 h−1 and 80 L h−1 gcat−1) under model conditions (only with CO and H2O) and industrial conditions, with a realistic feed. The promoted system with the ionic conductor physically mixed showed better catalytic activity associated with better water dissociation and mobility, considered as a rate-determining step. The water activation was assessed by operando diffuse reflectance infrared fourier transformed spectroscopy (DRIFTS) studies under reaction conditions and the Mo-containing ionic conductor exhibited the presence of both dissociated (3724 cm−1) and physisorbed (5239 cm−1) water on the Eu-doped ZrO2 solid solution, which supports the appearance of proton conductivity by Grotthuss mechanism. Moreover, the band at 3633 cm−1 ascribed to hydrated Mo oxide, which increases with the temperature, explains the increase of catalytic activity when the physical mixture was used in a water gas shift (WGS) reaction.

Lole Jurado, Nuria García-Moncada, Luis F. Bobadilla, Francisca Romero-Sarria, José A. Odriozola. Catalysts, 10 (8), 841, 2020.

An aqueous impregnation method using manganese (II) nitrate precursor, followed by calcination at 400 °C, was carried out for the preparation of manganese doped hydroxyapatite catalysts (MnxHap; x = Mn wt.%: 2.5, 5.0, 10, 20, and 30 based on MnO2). Methods of characterization including inductively coupled plasma spectroscopy (ICP), N2 physisorption, X-ray Diffraction (XRD), Fourier-Transform Transmission Infrared (FT-IR), Raman, and Thermal gravimetric analysis (TGA/MS) analysis were used for the identification of Mn species and its surrounding environment. Raman spectroscopy indicated the presence of the ε-MnO2 phase for Mn20Hap and Mn30Hap in agreement with the XRD results and the presence of β-MnOOH species for Mn5Hap and Mn10Hap. The formaldehyde total oxidation was investigated on these catalysts and it was shown that Mn5Hap was the most active catalyst, achieving a normalized rate of formaldehyde (HCHO) conversion into CO2 per mole of Mn of 0.042 h−1 at a temperature of 145 °C. The well dispersed oxidized manganese species on Hap with a medium Mn AOS (average oxidation state) were mainly responsible for this performance. Since HCHO was retained on the surface of all catalysts during the catalytic test, the combined Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) experiment at room temperature and thermodesorption (TD)-FTIR identified formate species as their oxidation consumed surface OH groups. A stability test and moisture effect study showed that the presence of water vapor has a beneficial effect on the performances of the catalyst.

Dayan Chlala, Jean-Marc Giraudon, Madona Labaki, Jean-François Lamonier. Catalysts, 10 (12), 1422, 2020.

In this study, we report the fabrication of graphitic carbon nitride doped zinc oxide nanocomposites, g-C3N4/ZnO, (Zn-Us) by using different amount of urea. They were further characterized by X-ray Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman, UV-vis, Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) techniques. The prepared nanocomposites were used as photocatalysts for the mineralization of the light sensitive dyes Methylene Blue (MB) and Rose Bengal (RB) under UV light irradiation, and corresponding photo-mechanism was proposed. Benefiting from these photocatalytic characteristics, urea derived g-C3N4/ZnO photocatalysts have been found to have excellent photodegradation activity against the MB and RB for 6 h and 4 h, respectively. Under the given experimental conditions, the degradation percentage of fabricated Zn-Us were shown ~90% for both model dyes. Compared to cationic MB dye, anionic RB dye is more actively degraded on the surface of prepared photocatalysts. The results obtained can be effectively used for future practical applications in wastewater treatment

Fahad A. Alharthi, Abdulaziz Ali Alghamdi, Hamdah S. Alanazi, Amjad Abdullah Alsyahi, Naushad Ahmad. Catalysts, 10 (12), 1457, 2020.

Ordered mesoporous carbon (OMC) was employed as a support for palladium nanoparticles in catalysts for the gas phase hydrodechlorination (HDC) of trichloromethane (TCM). 1 wt% palladium was incorporated using three methods: incipient wetness (IW); a dilute solution (DS) method; and a solid-liquid (SL) method. The effect of the preparation method on catalyst structure and activity was investigated. Catalyst composition and nanostructure were studied using gas physisorption, high specification transmission electron microscopy and X-ray photoelectron spectroscopy. Catalytic conversion and product selectivities were determined in steady-state activity tests at temperatures between 70 and 300 °C. Two of the catalysts (IW and DS) showed excellent dispersion of fine Pd nanoparticles of average diameter ~2 nm. These materials showed excellent activity for HDC of TCM which compares favourably with the performance reported for Pd on amorphous carbon catalysts. In addition, they showed relatively high selectivities to the more valuable higher hydrocarbons. However, the SL method gave rise to catalysts with larger particles (~3 nm) and a less uniform palladium distribution. This resulted in lower conversion and lower selectivities to higher hydrocarbons and in more severe catalyst deactivation at the highest reaction temperatures.

Farzeen Sakina, Carlos Fernandez-Ruiz, Jorge Bedia, Luisa Gomez-Sainero, Richard Baker. Catalysts, 11 (1), 23, 2020.

A series of Ni-xSi/ZrO2 (x = 0, 0.1, 0.5, 1 wt%, the controlled contents of Si) catalysts with a controlled nickel content of 10 wt% were prepared by the co-impregnation method with ZrO2 as support and Si as a promoter. The effect of different amounts of Si on the catalytic performance was investigated for CO2 methanation with the stoichiometric H2/CO2 molar ratio (4/1). The catalysts were characterized by BET, XRF, H2-TPR, H2-TPD, H2-chemisorption, CO2-TPD, XRD, TEM, XPS, and TG-DSC. It was found that adding the appropriate amount of Si could improve the catalytic performance of Ni/ZrO2 catalyst at a low reaction temperature (250 °C). Among all the catalysts studied, the Ni-0.1Si/ZrO2 catalyst showed the highest catalytic activity, with H2 and CO2 conversion of 73.4% and 72.5%, respectively and the yield of CH4 was 72.2%. Meanwhile, the catalyst showed high stability and no deactivation within a 10 h test. Adding the appropriate amount of Si could enhance the interaction between Ni and ZrO2, and increase the Ni dispersion, the amounts of active sites including surface Ni0, oxygen vacancies, and strong basic sites on the catalyst surface. These might be the reasons for the high activity and selectivity of the Ni-0.1Si/ZrO2 catalyst.

Li Li, Ye Wang, Qing Zhao, Changwei Hu. Catalysts, 11 (1), 67, 2021.

The present work incorporates the synthesis of a multifunctional catalyst for the transesterification of waste cooking oil (WCO) to biodiesel and recovery of rare earth elements (REEs). For this purpose, TiO2 nanoparticles and TiO2 doped with lithium ions were prepared. The influence of lithium ions on the catalytic performance of TiO2 was attained by impregnation of the different molar ratios of lithium hydroxide to bare TiO2. Then each catalyst was screened for catalytic conversion of WCO to fatty acid methyl ester (FAME) and also for REEs recovery. All synthesized materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis, and Hammett indicator for the basicity test. The obtained biodiesel was characterized by gas chromatography with mass spectrometry (GC-MS), 1H, and 13C nuclear magnetic resonance (NMR). Moreover, the physical parameters of the synthesized biodiesel were also determined. The REEs recovery efficiency of synthesized nanomaterials was investigated, and the percentage of REEs removal was determined by inductively-coupled plasma optical emission spectroscopy (ICP-OES).

Indu Ambat, Varsha Srivastava, Esa Haapaniemi, Mika Sillanpää. Catalysts, 9 (11), 943, 2019.

The unabated abuse of antibiotics has created a selection pressure that has resulted in the development of antimicrobial resistance (AMR) among pathogenic bacteria. AMR has become a global health concern in recent times and is responsible for a high number of mortalities occurring across the globe. Owing to the slow development of antibiotics, new chemotherapeutic antimicrobials with a novel mode of action is required urgently. Therefore, in the current investigation, we green synthesized a nanocomposite comprising zinc oxide nanoparticles functionalized with extracellular polysaccharide xanthan gum (ZnO@XG). Synthesized nanomaterial was characterized by structurally and morphologically using UV-visible spectroscopy, XRD, FTIR, BET, SEM and TEM. Subinhibitory concentrations of ZnO@XG were used to determine quorum sensing inhibitory activity against Gram-negative pathogens, Chromobacterium violaceum, and Serratia marcescens. ZnO@XG reduced quorum sensing (QS) regulated virulence factors such as violacein (61%), chitinase (70%) in C. violaceum and prodigiosin (71%) and protease (72%) in S. marcescens at 128 µg/mL concentration. Significant (p ≤ 0.05) inhibition of biofilm formation as well as preformed mature biofilms was also recorded along with the impaired production of EPS, swarming motility and cell surface hydrophobicity in both the test pathogens. The findings of this study clearly highlight the potency of ZnO@XG against the QS controlled virulence factors of drug-resistant pathogens that may be developed as effective inhibitors of QS and biofilms to mitigate the threat of multidrug resistance (MDR). ZnO@XG may be used alone or in combination with antimicrobial drugs against MDR bacterial pathogens. Further, it can be utilized in the food industry to counter the menace of contamination and spoilage caused by the formation of biofilms.

Fohad Mabood Husain, Imran Hasan, Faizan Abul Qais, Rais Ahmad Khan, Pravej Alam, Ali Alsalme. Coatings, 10 (12), 1190, 2020.

Ti modification of mesoporous silica support has been reported as an effective way to enhance Cr–Ti–Si interactions that, in turn, impact the catalytic dehydrogenation of ethane with CO2. However, such modification necessitates a repeated, time-consuming and tedious process. In this work, a simple, fast and facile approach has been utilized to synthesize chromium-oxide-loaded titania–silica mesoporous nanocomposites. A series of Cr(y)/Ti(x)–Si mesoporous nanocomposite catalysts with varying Ti and Cr contents were prepared and tested in the dehydrogenation of ethane with carbon dioxide. The as-synthesized catalysts were characterized by XRD, TEM, SEM, BET, UV–Vis–DR, XPS and H2–TPR techniques. The effect of titanium content, as well as chromium loading on the performance of the prepared Cr(y)/Ti(x)–Si catalysts, was investigated. It was found that 2.2 and 8 wt % are the optimum titanium and chromium contents in the synthesized catalysts for obtaining the highest catalytic activity. The superior catalytic performance of the Cr(8)/Ti(2.2)–Si catalyst can be attributed to a higher dispersion of the Cr species, as well as a higher content of the redox Cr species on the surface of the Cr/Ti–Si catalyst. The results showed that the Cr(8)/Ti(2.2)–Si catalyst efficiently dehydrogenated C2H6 in the presence of CO2 giving a 52.3% ethane conversion and 48.0% ethylene yield at 700 °C reaction temperature.

Abdulrhman S. Al-Awadi, Ahmed Mohamed El-Toni, Saeed M. Al-Zahrani, Ahmed E. Abasaeed, Aslam Khan. Crystals, 10 (4), 322, 2020.