Incipient Wetness Impregnation Research Articles

Efficient catalysis of acetylene semi-hydrogenation through synergistic action of supported ionic liquid-nickel catalyst

In the semi-hydrogenation of acetylene, nickel-based catalysts offer a promising alternative to precious metal palladium catalysts. Despite the positive hydrogenation activity of nickel-based catalysts, there is still room for improvement in terms of their selectivity and stability. In this study, a simple incipient wetness impregnation method was employed to prepare Ni(OAC)2-IL/Al2O3 catalyst and its performance in the selective hydrogenation of acetylene was investigated. It was found that under the conditions of 170 °C and a space velocity of 600 h−1, the 3 % Ni(OAC)2-IL/Al2O3 catalyst achieved a 95.3 % acetylene conversion with an 85.6 % ethylene selectivity. Furthermore, the catalyst exhibited outstanding stability over a 100 hour test. TEM, XPS and C2H4-TPD experiments showed that the Ni species were encapsulated in the ionic liquids (ILs), and the interaction between the metal ions, nickel, and the ILs ensured a high dispersion and stability of the actives on the carriers, and the electronic effect between the ionic nickel and the ionic liquids increased the electron cloud density of the Ni, which improved the catalyst selectivity, which is the main reason for its excellent catalytic performance.

Deposition of Pd, Pt, and PdPt Nanoparticles on TiO2 Powder Using Supercritical Fluid Reactive Deposition: Application in the Direct Synthesis of H2O2.

In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium dioxide (TiO2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 K and 15.6 MPa enabled the deposition of uniform mono- and bimetallic nanoparticles smaller than 3 nm on TiO2. Electron-dispersive X-ray spectroscopy demonstrated the formation of alloy-type structures for the bimetallic PdPt nanoparticles. H2O2 is an excellent oxidizing reagent for the production of fine and bulk chemicals. However, until today, the design and preparation of catalysts with high H2O2 selectivity and productivity remain a great challenge. The focus of this study was on answering the questions of (a) whether the catalysts produced are suitable for the direct synthesis of hydrogen peroxide (H2O2) in the liquid phase and (b) how the metal type affects the catalytic properties. It was found that the metal type (Pd or Pt) influenced the catalytic performance strongly; the mean productivity of the mono- and bimetallic catalysts decreased in the following order: Pd > PdPt > Pt. Furthermore, all catalysts prepared by SFRD showed a significantly higher mean productivity compared to the catalyst prepared by incipient wetness impregnation.

Boosting photocatalytic water splitting of TiO2 using metal (Ru, Co, or Ni) co-catalysts for hydrogen generation

The photocatalytic activity of titanium dioxide (TiO2) nanoparticles toward hydrogen generation can be significantly improved via the loading of various metals e.g., Ru, Co, Ni as co-catalysts. The metal co-catalysts are loaded into TiO2 nanoparticles via different deposition methods; incipient wet impregnation (Imp), hydrothermal (HT), or photocatalytic deposition (PCD). Among all of the tested materials, 0.1 wt% Ru–TiO2 (Imp) provided the highest initial hydrogen catalytic rate of 23.9 mmol h−1 g−1, compared to 10.82 and 16.55 mmol h−1 g−1 for 0.3 wt% Ni–TiO2 (Imp) and 0.3 wt% Co–TiO2 (Imp), respectively. The loading procedures, co-catalyst metals type, and their loading play a significant role in elevating the photocatalytic activity of pristine TiO2 semiconductors toward hydrogen generation. Redox transition metals e.g., Co and Ni exhibit comparable photocatalytic performance to expensive elements such as Ru.

Tailoring the dielectric properties of bentonite for advanced capacitor Applications: The role of ruthenium and strontium incorporation

This study utilized incipient wetness impregnation to synthesize bentonite materials and to enhance their physical characteristics with ruthenium (Ru) and strontium (Sr) ions. The atomic composition of the materials was confirm confirmed via the analysis of the EDX measurements. X-ray crystallography indicates that the materials have almost similar diffraction peak profiles, and that the addition of Sr increases the crystallinity of the bentonite grains. Dielectric and electrical properties, measured between 25 °C and 55 °C at frequencies of 1 kHz −1 MHz, revealed that the real and imaginary impedances increased upon the introduction of 5 % Ru and 5 % Sr, possibly due to Ru and Sr segregation into the grain boundaries, increasing the resistance of the bentonite granular structure. For all materials, the observed saturation of the real electric modulus at high frequencies, and the reduction of the permittivity with increasing frequency, may be explained by the Maxwell-Wagner interfacial polarization and Koop's empirical theory. This trend is more pronounced for the bentonite with Sr, highlighting the essence of the present work for engineering interfacial polarisation applications associated with supercapacitors and batteries.

Conversion of Sunan Candlenut Oil to Aromatic Hydrocarbons with Hydrocracking Process Over Nano-HZSM-5 Catalyst

In this paper, the catalysts (Nano-HZSM-5 and Fe-La/nano HZSM-5) were prepared with incipient wetness impregnation and applied for hydrocracking of Sunan candlenut oil. The hydrocracking process was conducted in a batch reactor with a pressure of 20-30 bar H2 gas for 2 h under various temperatures. The results demonstrated that hydrocracking of Sunan candlenut oil using nano HZSM-5 and Fe-La/NHZ catalysts could be converted into aromatic hydrocarbons, and the reaction temperature affected hydrocarbon production. The aromatic compounds, such as propyl-benzene, 1-ethyl-3-methylbenzene, heptyl-benzene, 2-ethyl-naphthalene, etc., reached 35.51% over the Fe-La/NHZ_2 catalyst. In all cases, the zeolite-based catalysts are the most suitable to produce aromatic hydrocarbons. Metal impregnated (Fe and La) on nano HZSM-5 catalyst could improve the aromatics compounds due to increased metal and acid sites. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Luminescence of Lanthanide Complexes in Mesoporous Silica Matrices: A Textbook Example of Tris‐Dipicolinate Europium Complex Adsorbed in SBA‐15

AbstractThe incorporation of luminescent lanthanide complexes in inorganic matrices opens appealing possibilities in the rational upstream conception of new luminescent materials with easier recyclability. In this regard, the influence of SBA‐15 mesoporous silica, as a host matrix, on the photophysical properties of europium‐trisdipicolinate cesium salt is investigated. The lanthanide complex can be completely and reversibly adsorbed on the silica, using incipient wetness impregnation (IWI) in WATER, without the need of anchoring groups or covalent bonding on the silica surface. This specific procedure allows the homogeneous dispersion of the lanthanide complex into the host silica matrix. Appropriately assessing the photophysical properties of the targeted luminescent material proved remarkably challenging, demanding utmost caution, particularly due to the strong scattering of the mesoporous matrices. Additionally, while the observations confirm an important increase of luminescence lifetimes of lanthanide complexes upon integration into these mediums, this variation is attributed to the differing refractive indexes and not to specific surface interactions or confinement effect. Indeed, it appeared that previous literature precedents depicted erroneous exhalations of the complexes intrinsic quantum yield due to the repeated use of erroneous refractive index values. In the meantime, the luminance of these materials under UV irradiation improves drastically in comparison to what is obtained with the physical dispersion of micro‐crystals of the lanthanide complex onto silica. It is demonstrated that this improvement is due to a reduced inner filter effect in the adsorbed samples. In this regard, IWI of lanthanide complexes in the mesoporous matrices method could be of interest in the development of recyclable emitting layers, less demanding in terms of emitter quantity.

Tri‐reforming of Methane over a Hydroxyapatite Supported Nickel Catalyst

AbstractFor the first time, a catalyst containing 5 wt. % Ni supported on a hydroxyapatite support (HAP) has been synthesized and evaluated in tri‐reforming of methane (TRM) for synthetic gas (syngas) production. Nickel nanoparticles could be easily formed on HAP surface by using the conventional incipient wetness impregnation technique. In TRM, under unfavorable reaction conditions from the thermodynamic point of view (e. g. medium reforming temperature of 700–800 °C, low steam‐to‐carbon ratio, etc.), this catalyst showed high methane conversion (up to 90 %), however, some deactivations took place. The latter could be explained by both the thermal sintering of nickel nanoparticles and the solid carbon formation. The impact of the main operational parameters has been studied. Increasing the reaction temperature, the molar ratios of oxygen‐to‐carbon and steam‐to‐carbon are favorable for the methane conversion and mostly for the stability of the catalyst. High methane conversion of ca. 90 % with a perfect catalytic stability during 300 hours‐on‐stream could be achieved at 800 °C and 1.4 bar, using a mixture containing low ratio of oxidant‐to‐carbon (molar ratio of CH4/CO2/H2O/O2/N2=1.0/0.67/0.9/0.1/0). These results offer the opportunity to further design an optimal Ni/HAP catalyst by improving metal‐support interaction and downsizing nickel nanoparticles.

Revealing the mechanisms of NH3 adsorption and reactions in catalytic NOx reduction over Cux/CHA zeolites by in situ DRIFTS spectroscopy

Adsorption and activation of NH3 on Cu-SSZ-13 were essential for NOx removal, however, their important role at the molecular level remains unclear. In this work, the Al-rich Cu/SSZ-13 (Cux/CHA) catalysts were synthesized by the incipient-wetness impregnation method, and the NH3-SCR performance was investigated. It is found that high Cu content promoted the formation of Z-[Cu(OH)]+ and CuOx particles, enhanced the adsorption capacity of NOx, and increased the intra-zeolite oxolation process in the Cux/CHA catalysts. In situ DRIFTS results showed that the Z-[Cu(OH)(NH3)x]+(x<3) exhibited analogous properties to B-NH4+, but it would convert to Z-[Cu(OH)(NH3)3]+ with increasing NH3 adsorption time and exhibit L-NH3 properties. Those findings could provide a new insight into understanding the adsorption and activation of NH3 in low-temperature reactions, as well as new ideas for improving NOx conversion during cold start.

Insights into the Construction of Robust Pt Clusters with Satisfactory Stability on CeO2 for the Catalytic Oxidation of CO.

Improving the efficiency of platinum group metals (Pt, Pd, Rh, etc.) in catalytic oxidation reactions remains an urgent topic. The conflict between the low-temperature activity and high-temperature stability of noble metals can hardly reach a consensus. For instance, Pt cluster catalysts supported on CeO2 with high low-temperature activity will suffer from deactivation due to the redispersion under high-temperature lean-burn reaction conditions. Herein, two Pt1/CeO2 prepared by the incipient wetness impregnation method using different Pt precursors possessed varied Pt-O and Pt-O-Ce coordination numbers (CNs). They showed various priorities in CO oxidation versus NH3 selective catalytic oxidation, materials with higher CNPt-O-Ce selectively catalyzing NH3 oxidation to N2 more superior, conversely materials with lower CNPt-O-Ce performing better in CO oxidation. After activation by H2 reduction, both formed massive Pt clusters on the CeO2 surface but showed drastically distinct stability in lean-burn CO oxidation reactions. By summarizing the experimental results of high-angle annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, Raman spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy, etc., it is beyond doubt that the difference in the initial states of Pt1 due to distinct precursors indeed determine the redispersion behavior of the reduced Pt clusters on CeO2. Materials with lower CNPt-O-Ce and higher CNPt-O are more likely to form robust Pt clusters, as they are not conducive to Pt anchoring, thus restricting the reversible structural evolution occurring under lean-burn CO oxidation and reductive conditions. This approach serves as a guide for the convenient and efficient construction and exploration of robust Pt cluster catalysts.

In situ activated CoAg bimetallic catalyst for selective hydrodeoxygenation of syringol to cyclohexanol

Development of highly effective catalysts for selective hydrodeoxygenation (HDO) of syringol, a model compound of lignin, to cyclohexanol (CYHAOL) is a challenge due to the intricate molecular structure of syringol. Herein, we have synthesized an in–situ activated cobalt–silver bimetallic catalyst, CoAg/SiO2, through a simple incipient–wetness impregnation method. The catalyst without pre–reduction treatment attained a complete conversion with 93.8 mol% CYHAOL selectivity under moderate reaction conditions. Characterizations including HRTEM, XPS, XRD, NH3–TPD, and H2–TPR unanimously revealed the structure–activity relationship of the catalyst. In the reaction system, Ag promoted the in–situ reduction of Co3O4 to form a polycrystalline–structure complex (CoOx) containing oxygen vacancies. Ag also combines with Co to construct strong acid sites. The synergy of CoOx, oxygen vacancies, Ag, and acid sites demonstrates a high–efficiency HDO of syringol to CYHAOL. CoAg/SiO2 exonerates the pre–reduction treatment, simplifying the preparation and maintenance process and preventing severe sintering of the metals.

Effect of preparation conditions of nanocrystalline Pd/MgO catalysts on their performance in selective hydrogenation of acetylene

In the present work, an alkoxide sol-gel method was applied to prepare Pd/MgO catalysts. The sol-gel procedure was followed by supercritical drying (aerogels) or conventional drying (xerogels) in a furnace. These materials were compared with the impregnated samples. The Pd loading was 1 wt% in all the cases. The as-prepared catalysts were characterized by a set of physicochemical methods. Both the type of the Pd precursor and the preparation route were found to affect the porous structure of the materials as well as the dispersion of the palladium particles and their localization over the MgO support. Both the xerogel and incipient wetness impregnation methods lead to a narrower pore size distribution in comparison to the aerogel technique. The most dispersed particles with an average size of ∼ 2.0–2.2 nm were observed for the samples prepared by xerogel and impregnation methods. In the case of aerogel-prepared samples, metallic palladium particles possess bimodal distribution with average diameters of 4.3 and 8.4 nm. The best catalytic performance in acetylene hydrogenation to ethylene (50 % acetylene conversion at 37 °C with selectivity ∼60 %) was observed for the Pd/MgO catalyst prepared via the aerogel route using [Pd(NH3)4](NO3)2. Compared to other samples, this material is characterized by relatively weak metal-support interactions and the availability of active sites for reactants, which ensures the kinetic mode of the hydrogenation reaction (Ea = 74.9 kJ/mol).

High-Performance Ir1/CeO2 Single-Atom Catalyst for the Oxidation of Toluene.

The elimination of toluene is an obligatory target with increasing VOC emission in recent years. This study successfully prepared a single-atom Ir catalyst (Ir1/CeO2) by a simple incipient wetness impregnation method, confirmed by in situ CO DRIFTS and AC-HAADF-STEM. Compared to the cluster Ir catalyst (Ir/CeO2-C), Ir1/CeO2 exhibited excellent catalytic performance, stability, and water resistance for the oxidation of toluene. By Raman, H2-TPR, O2-TPD, and XPS experiments, abundant oxygen defects and a unique Ir3+-Ov-Ce3+ structure were formed for the Ir1/CeO2 sample because it had a lower oxygen vacancy formation energy. Furthermore, the DFT results revealed that the Ir1/CeO2 sample had a lower ring-opening energy barrier and adsorption energy of the ring-opening products, which was the rate-determining step for the oxidation of toluene. This work provides instructive insights into the construction of Ir/CeO2 catalysts for the highly efficient removal of VOCs.

Hydrothermally Ce modified HZSM-5 zeolite enhancing its strong acidity and Brønsted/Lewis acid ratio: Stably boosting ethylene/propylene ratio for cracking n-heptane

Modulating zeolite acidity by conventional metal impregnation is a challenge in preparing hydrocarbon cracking catalyst, which often eliminates its intrinsic strong acidity, resulting in reduced the hydrocarbon conversion capacity and low light olefins (C2=-C4=) yield. Here, the Ce/HZ5-HM and CeO2/HZ5-HM catalysts were readily prepared by hydrothermally modifying HZSM-5 zeolite (HZ5) with cerium salts (Ce3+) and cerium oxide (CeO2), respectively. Comparatively, Ce/HZ5-IW catalyst was obtained by modifying HZ5 with Ce3+ using the incipient wetness impregnation. It is revealed that, compared to HZ5, Ce/HZ5-HM and CeO2/HZ5-HM catalysts have an increased ratio of strong/weak (S/W) acid and Brønsted/Lewis (B/L) acid, while Ce/HZ5-IW sample has reduced strong acidity. Further, the Ce/HZ5-HM exhibits higher acid strength, acid density, and B/L value than that of CeO2/HZ5-HM sample. When applied to cracking n-heptane reaction, compared with HZ5 and Ce/HZ5-IW, heptane conversion and ethylene yield on Ce/HZ5-HM and CeO2/HZ5-HM catalysts increase by 6–11 % and 7–9 %, yielding the ratio of ethylene/propylene (E/P) more than 1. Moreover, Ce/HZ5-HM and CeO2/HZ5-HM catalysts perform a lifetime of 117 h and 150 h, with four-to-five times longer than that of HZ5 zeolite (∼29 h) and Ce/HZ5-IW catalyst (∼39 h). The characterization results demonstrate that, adopting hydrothermal method ensures more Ce3+ interacting with the silanol groups in Ce/HZ5-HM, generating the new Brønsted acid sites and makes CeOx species incorporating into the hydroxyl nest of zeolite, which can heal the defective sites and improve stabilization of acidity and framework structure of zeolite. Therefore, the above two catalysts can highlight the monomolecular cracking reaction, low coke deposit rate, long catalytic stability.

Fischer-tropsch synthesis: effect of temperature and iron-cobalt ratio in Fe-Co/meso-HZSM-5 catalyst on liquid product distribution

The Fischer-Tropsch synthesis converted hydrogen and carbon monoxide into linear hydrocarbons as liquid fuel. Iron and cobalt were used as polymerization catalyst, that impregnated on HZSM-5. The Fe-Co/HZSM-5 could be applied as bifunction catalyst which combined polymerizing synthesis gas and long chain hydrocarbon cracking for making biofuel. The objective of this study is observing the effect of temperature and composition of iron and cobalt combination, supported by HSZM-5 (Fe-Co/HZSM-5) catalyst on fuel product composition. The results obtained from this study would be used to find optimum condition for various iron and cobalt ratio in the catalyst. The mesoHZSM-5 was prepared from ammonium ZSM-5 over calcination, desilication, and dispersion. The mixed solution consisted of Co(NO3)2.6H2O and Fe(NO3)3.9H2O were used as precursor for incipient wetness impregnation on HZSM-5. The catalyst performance was observed in a continuous fixed bed reactor using Fe-Co/meso-HZSM-5 catalyst with synthesis gas at various composition iron and cobalt ratio (10–40 % wt. Fe in Co), various temperature (225–275 °C) at 20 bars. All catalysts were reduced in situ in the reactor. The 10Fe-90Co/mesoHZSM-5 catalyst was more suitable for FTS at 250 °C with alkane (20.49 %) as the main product and alcohol as the by-product (79.51 %). The others catalysts composition of 20–40 % Fe (by weight) in Fe-Co were more suitable for FTS at 225–250°C because under these conditions, alkanes as the main product were obtained in relatively higher compositions compared to other compounds. The mechanism of paraffins, olefins, aldehydes and alcohols formation in this FTS reaction followed the hydrogen assisted CO dissociation with CO-insertion mechanism

Boosting the selective hydrogenation of biphenyl to cyclohexylbenzene over bimetallic Ni-Ru/SiO2 catalyst via enhancing strong metal-support interaction

Tuning the metal-support interaction (MSI) between highly dispersed nanosized metal particles and the support plays a pivotal role in the activity and selectivity of polyaromatics selective hydrogenation. In this work, the supported bimetallic Ni-Ru/SiO2-SEA catalyst was prepared by a strong electrostatic adsorption (SEA) strategy, and applied for the selective hydrogenation of biphenyl (BP) to cyclohexylbenzene (CHB). Compared to the catalysts prepared by the conventional incipient wetness impregnation method and Ni/SiO2-SEA, the significant effects of MSI and hydrogen spillover on Ni-Ru/SiO2-SEA facilitated the highly exposed and uniformly dispersed electron-deficient Niδ+ (0 < δ < 2) species, which could enhance adsorption and activation of the electron-withdrawing phenyl group and H2, thereby promoting the efficient and selective conversion of BP to CHB. At the conditions of 160 ℃ and 2 MPa H2 pressure, BP conversion over Ni-Ru/SiO2-SEA reached nearly 100 % within 3 h, achieving a remarkable selectivity of 97.9 % towards CHB, along with a high turnover frequency of 2756.9 h−1 for the active metallic Ni sites. Importantly, according to the kinetic simulations, the hydrogenation rate constant of Ni-Ru/SiO2-SEA was the highest (2.76 × 10-2 mol·g−1·h−1) among the employed catalysts. Moreover, after six consecutive cycles, no obvious decline in hydrogenation efficiency was observed, confirming the remarkable activity and stability of Ni-Ru/SiO2-SEA. Furthermore, the activation of BP and desorption of CHB pathway on the Niδ+ species were elaborated through temperature-programmed desorption characterization, highlighting the prominent contribution of MSI in enhancing the selective hydrogenation of polyaromatics.

Engineering biochar-supported nickel catalysts for efficient CO2 methanation

Carbon dioxide methanation is a promising approach to convert captured CO2 into green natural gas. Developing high performance biochar-supported nickel catalysts promotes a circular economy and the application of sustainable catalysts. Western red cedar biochar was produced via pyrolysis at 400, 500, and 600 °C and loaded with nickel via incipient wetness impregnation. Methanation was done at 400, 500, and 600 °C with the highest methane yield of 59% achieved at 500 °C with 10 wt.% Ni loading. This is comparable to a γ-Al2O3 supported catalyst prepared and tested similarly, which achieved a methane yield of 53%. Biochar-supported catalysts showed deactivation whereby methane yield decreased from 59% to 51% over 5 h, likely due to coking and/or the sintering of nickel. Various space velocities were tested, and results demonstrated that with a space velocity of 37.5 mL/g.min methane selectivity was 89% after 1 h on stream compared to methane selectivity of 42%, which was achieved at a space velocity of 112.5 mL/g.min. This shows that a much higher rate of deactivation is observed at higher space velocities. Increasing the nickel loading from 5 wt.% to 10 wt.% increased methane yield from 40% to 58% after 1 h on stream. The higher loading also showed significantly less deactivation. Future work focusing on the extent and impact of metal-support interactions and metal dispersion on catalytic performance and deactivation during CO2 methanation is recommended.

Dilute Alloy Catalysts for the Synthesis of Isobutanol via the Guerbet Route: A Comprehensive Study

This study investigates the potential of bimetallic alloy catalysts, specifically Ni99Pt1, Cu99Ni1, Cu99Fe1, Fe99Pt1, and Fe99Pd1, for the synthesis of isobutanol via the Guerbet route. The catalysts were synthesized with a doping of 1 at% Ni, Fe, Pt, and Pd in the base metals Fe, Cu, and Ni. The catalytic properties of these bimetallic alloy catalysts were explored for their potential for promoting the Guerbet reaction. The study aims to test the usability of the theoretically predicted d-band values in the synthesized bimetallic catalysts, which were prepared by means of incipient wetness impregnation, and shows that doping amounts smaller than 1 at% already significantly improved the catalytic activity of the base metals. In particular, the doping of nickel with platinum yielded an effective catalyst for the synthesis of isobutanol via the Guerbet pathway. The Ni99Pt1/C catalyst from the presented experiments had the highest Space Time Yield (STY) and is, therefore, also a promising catalyst for the hydrogen-borrowing reactions class.

Fabricating mesoporous titanium nanocomposites with high adsorption and photolysis performance by using rice husk ash as a renewable support source

Rice husk (RH) is a valuable and renewable source of bioenergy. Once RH has been burned to produce thermal energy, RH ash (RHA) remains, and this ash can be used as a sustainable resource to improve the circular economy. In this study, we used RHA as a silicon source to fabricate RH-SBA-15. Incipient wetness impregnation was then employed to directly incorporate TiO2 nanocrystals into the mesopores of the RH-SBA-15. XRD and TEM confirmed the successful integration of TiO2 into the framework of RH-SBA-15, with the hexagonal array and ordered mesostructure of RH-SBA-15 being unchanged. FTIR and XPS revealed the formation of Ti–O–Si bonds on the surface of RH-SBA-15, which enhanced the activity of TiO2. The pore volume and surface area of TiO2/RH-SBA-15 were 0.292–0.604 cm3/g and 170–366 m2/g. Photocatalytic tests were conducted to examine the catalysts used in the degradation of Reactive Blue 4 (RB4). The results indicated that TiO2/RH-SBA-15 exhibited 63% higher catalytic efficiency than that did bare TiO2. The surface adsorption of RH-SBA-15 and the high photolytic activity of TiO2 resulted in an improvement in RB4 degradation. The photoactivity increased with decreasing solution pH and calcination temperature and increasing catalyst mass. A TiO2 ratio of 25% resulted in the highest photoactivity, yielding a composite that completely eliminated RB4 within 5 h. The catalyst composites had high stability and photoactivity after four cycles. Overall, the method used in this study for fabricating mesoporous photocatalysts from recycled RHA is valuable for bio-waste disposal and wastewater purification.

Effect of Nb as dopant of hydrotalcite catalysts during the ethanol condensation to optimize n-Butanol production

The present study optimizes Cu-supported catalysts on hydrotalcite for the synthesis of n-butanol whose interest is in its use as biofuel, due to its superior performance in comparison with other short-chain alcohols. The catalytic performance was improved by adding Nb to the catalytic formulation. In this way, several Cu-Nb catalysts supported on hydrotalcites (Mg/Al) with different Nb loadings were synthesized by incipient wetness impregnation and characterized by H2−temperature-programmed reduction, X-ray diffraction, N2 physisorption, CO2− and NH3−thermo-programmed desorption and X-ray photoelectron spectroscopy. It was shown that the incorporation of Nb promoted a suitable balance between the acid-basic and redox sites, modulating the Cu0/Cu+ dehydrogenation/hydrogenation properties for the n-BuOH production. The synthesis of multiple value-added products (n-BuOH, acetaldehyde, ethyl acetate, and 1-hexanol) was achieved in both the liquid− (at 180 ºC) and gas−phase (150−350 ºC), where it was demonstrated that both the n-BuOH selectivity and ethanol conversion improved with the Nb addition. The performance of the catalysts under time on stream and their recycling is also described.

Inhibition of methane formation during the water gas shift reaction by Sn doping of Co-CeO2 catalysts

Co-Ce-Sn catalysts were developed for application in the water gas shift reaction (WGSR) at intermediate temperatures (350–400 °C). Ceria-based supports with tin loadings ranging from 2.5% to 30% mol (CeSn(X%)) were synthesized via co-precipitation. Using these supports, cobalt catalysts were developed using the incipient wetness impregnation method, yielding Co-Ce-Sn catalysts (15Co/CeSn(X%)). Physicochemical techniques were employed to characterize the supports and catalysts. XRD and Raman spectroscopy analyses confirmed the presence of solid solutions between CeO2-SnO2 oxides. Notably, a higher Sn loading increased specific surface area and decreased support basicity. H2-TPR and XPS analyses of the catalysts indicated a higher metal-support interaction in the presence of tin. Under all conditions evaluated, the 15Co/CeSn(5%) material was active and presented 100% selectivity towards H2. While the 15Co/CeO2 material presented methane formation. Both samples were stable over 15 hours in the WGSR at 350°C. These findings suggest that the tin loading enhances hydrogen selectivity compared to samples without tin, due to the inhibition of methane formation. Raman spectroscopy analysis of used samples revealed the presence of carbon deposits in the 15Co/CeO2 sample but not in the 15Co/CeSn(5%) sample, suggesting that tin would also have disfavored the carbon formation during the WGSR.