Incipient Wetness Impregnation Method Research Articles

Direct synthesis of H2O2 over Pd/C catalysts prepared by the incipient wetness impregnation method: Effect of heat treatment on catalytic activity

Although various Pd/C catalysts have been applied in the direct synthesis of H2O2, unsatisfactory H2O2 yields have been achieved. We systematically investigated the effect of heat treatment on the physicochemical properties of Pd/C catalyst, and thereby on the catalytic performance in the direct synthesis of H2O2. Pd/C catalysts prepared by the incipient wetness method were subjected to different heat treatments and applied in H2O2 synthesis. The calcination temperature was found to have a key role in determining the Pd nanoparticle (NP) size; calcination at 523 K yielded highly oxidized and small Pd NPs corresponding to the sub-nano domain (1.4–2.5 nm). This Pd/C catalyst is superior not only in promoting H2O2 formation, but also in suppressing the subsequent unfavorable H2O2 decomposition and hydrogenation, which explains its excellent H2O2 productivity (as high as 4,443 mmol H2O2/g Pd·h) and selectivity (94.5%). On the other hand, the reaction performance of the Pd/C catalysts calcined at a higher temperature (673 K) or reduced under hydrogen was sharply reduced owing to the formation of larger Pd NPs or the enhancement of the metallic nature of Pd, respectively The amount of residual Cl ion on Pd/C catalyst after heat treatment also had an impact on the catalytic activity as it affected the pH of reaction solution. These results clearly demonstrate that an efficient Pd/C catalyst can be realized by fine tuning the conditions of heat treatment during catalyst preparation.

Dehydrogenation of a mixture of light alkanes on supported platinum metals in a reducing atmosphere

A mixture of light alkanes simulates associated gas of oil production, the growth of oil and gas production in the world, and especially in Kazakhstan, leads to the fact that associated gases of oil production continue to be flared, causing significant harm to the environment, at a time when they are a valuable petrochemical feedstock. Active and selective catalysts are needed to convert inert alkanes to olefins. We prepared 3% Pt, Pd, Ru on γ – Al2O3 by the incipient wetness impregnation method. The transformation of a mixture of light alkanes C1-C4 has been carried out on a laboratory flow-bench apparatus in four modes at atmospheric pressure and temperatures of 350-500oC. The freshly prepared and spent catalysts were investigated by physicochemical methods TEM, SEM and BET. The maximum yield is formed for 3% Ru / γ – Al2O3 when a mixture of light alkanes with water is fed together at 500 ° C. We assume that water shifts the equilibrium in the system, resulting in the formation of dissipative structures that affect the activity of catalysts.

Preparation, Characterization and Catalytic Activity of CrSBA-15 for 2-Propanol Decomposition

The chromium mesoporous materials have been used in many catalytic reactions. Some studies have been devoted to determining the nature of chromium species and to characterizing the chemical structure. The different chromium species depend on synthetic methods and the support used. In this work we prepared mesoporous SBA-15 supported chromium materials referred to in this document as xCrSBA-15, was prepared by the incipient wetness impregnation method. The materials were characterized by X-ray diffraction (XRD), nitrogen (N2) adsorption–desorption isotherms, hydrogen temperature-programmed reduction (H₂-TPR), scanning electron microscopic (SEM), energy dispersive X-ray spectroscopy (EDS), diffuse reflectance ultraviolet-visible (UV–vis) and Fourier transform IR (FT-IR). Chromium in SBA-15 forms different types of chromates and Cr₂O₃, causing morphological and textural changes and generating different catalytic centers. The catalytic conversion of 2-propanol to xCrSBA-15 materials were carried out by in a quartz reactor with a loading of 30 mg of the material at 300°C. Before the catalytic test, the material was activated in two ways: with N₂ and reduced at a H₂/Ar flow (MxCrSBA-15). The catalytic conversion of 2-propanol to xCrSBA-15 did not increase with reduction (MxCrSBA-15) but decreased deactivation. All the materials had an acidic behavior, which is related to the chromate species in the materials. These results suggest that the more acidic materials favor the formation of coke during the deactivation process, and coke reduces the Cr³⁺ to Cr²⁺ species, thus decreasing the acidity of the materials.

Hydrogen and carbon monoxide derivation over metal supported on fibrous silica KCC-1

Methane is the major component of natural gas that greatly contributes to a rise in global concentration of greenhouse gases. The greenhouses gases emission can be significantly reduced by partial oxidation of methane (POM) to the syngas. Additionally, syngas is an important gas material for the production of valuable chemicals and fuels in the industry. In this study, mesoporous silica KCC-1 catalyst was successfully prepared by using microwave assisted hydrothermal technique. Meanwhile, Rh/KCC-1 catalyst was prepared by incipient wetness impregnation method using (RhCl3.xH2O) as a precursor. Their catalytic activity towards POM reaction was investigated by using fixed bed quartz reactor. Physicochemical properties of both catalysts were characterized with field emission spectroscopy (FESEM), nitrogen physisorption and pyrrole probed infrared spectroscopy. The results obtained suggest that KCC-1 and Rh/KCC-1 exhibited spherical morphology with a high surface area of 812 and 700 m2/g, respectively. In addition, both catalysts demonstrated a uniform mesopores with the presence of inter and intra-particle porosity. Pyrrole probed IR spectroscopy results showed that Rh/KCC-1 has low concentration of basic sites than KCC-1. The reduction of basic sites concentration gave a better selectivity of syngas product which caused the suppression of side reactions. Rh/KCC-1 exhibited better catalytic activity than KCC-1 with 99.92% conversion of methane and 97.54% selectivity of H2 at 973 K. It was noteworthy that the addition of Rh significantly increased the rate of methane conversion and selectivity towards main product.

Effects of Ce over TiO2 supported MnOx-based Catalyst for NOx Reduction by Ammonia

Ce modified MnOx-based catalysts have attracted much attention due to its high activity for selective catalytic reduction of NOx by NH3 (NH3-SCR) at low-temperatures. However, the most important role of Ce on the NH3-SCR performance of MnOx-based catalysts has not been confirmed. Herein, the typical Ce-Mn/TiO2 catalyst was synthesized through incipient-wetness impregnation method, the positive role of Ce on Ce-Mn/TiO2 catalyst in the NH3-SCR process was revealed by combining different activity tests (including NO oxidation and NH3 oxidation) and characterizations (including XRD, XPS and He-TPDMS experiments). It was found that the introduction of Ce can promote the dispersion of MnOx on TiO2 support. Meanwhile, the doping of Ce in MnOx can also increase the content of Mn4+ species. The Mn4+ species plays a crucial role in NO oxidation reaction, which can trigger the “Fast SCR” reaction and promote the conversion of NOx. This work provides insight into the catalyst design for NH3-SCR process at low-temperature.

Influence of sulfating method on La–Ni–S2O82–/ZrO2–Al2O3 solid superacid catalyst for n-pentane isomerization

La–Ni–S2O82–/ZrO2–Al2O3 catalysts were successfully prepared by two different methods of sulfate impregnation, and the physico-chemical properties of the catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, pyridine adsorption–infrared spectroscopy, and X-ray photoelectron spectroscopy techniques. Catalytic activities were evaluated in a fixed-bed flow reactor using n-pentane isomerization as the probe reaction. Compared with catalyst La–Ni–S2O82–/ZrO2–Al2O3-I, prepared by the traditional impregnation method, the catalyst La–Ni–S2O82–/ZrO2–Al2O3-W, prepared by the incipient-wetness impregnation method, possessed higher pore volume, pore size, sulfur content, and stronger Brønsted acid sites. The catalytic activity for La–Ni–S2O82–/ZrO2–Al2O3-W was maintained at around 56% within 3000 min with an isopentane selectivity of 88% which showed much greater stability than that of La–Ni–S2O82–/ZrO2–Al2O3-I. This can be attributed to the fact that (1) the large pore size and pore volume of La–Ni–S2O82–/ZrO2–Al2O3-W can largely suppress carbon deposition and (2) the more numerous and stronger Brønsted acid sites for La–Ni–S2O82–/ZrO2–Al2O3-W guaranteed to provide enough acid sites for isomerization during the reaction process.

A recyclable heterogeneous-homogeneous-heterogeneous NiO/AlOOH catalysis system for hydrocarboxylation of acetylene to acrylic acid.

Concerns about the high-valued utilization of coal- and natural gas-based acetylene has provided particular impetus for exploration of acrylic acid (AA) production via one-step hydrocarboxylation reaction. Motivated by simple recovery, recycling and reuse of the catalyst, we report a high-performance NiO/AlOOH catalyst with AA space-time-yield of 412 gAA gcat.−1 h−1, obtainable by a simple incipient wetness impregnation method. Detailed kinetic and controlled experiments confirmed that nickel species on such a solid catalyst provide a heterogeneous–homogeneous–heterogeneous catalytic cycle where the chelates formed between CO and leached nickel act as the active species. The thorough recovery of leached nickel species improves the catalyst stability greatly. These preliminary findings indicate further prospects for new heterogeneous catalyst design in traditional homogeneous catalytic systems.

Catalytic steam reforming of JP-10 over Ni/SBA-15

As the only H2 resource on aircraft from the steam reforming of the jet fuels on board, catalytic steam reforming of JP-10 (one of Jet fuels) over nickel-based catalyst Ni/SBA-15 were first carried out in a fixed bed tube reactor to produce hydrogen on-site or on board. A series of Ni/SBA-15 catalysts with different Ni content (3, 5, 8 and 10.8 wt%) were prepared by a modified incipient wetness impregnation method with addition of sucrose as ligand. And the effect of operation conditions of temperature (630–700 °C), nickel loading, liquid hour space velocity (LHSV = 5, 10, 15 ml/gcat·h), steam to carbon molar ratio (S/C = 3, 5) on the catalytic activity and selectivity was investigated. It was found that 8Ni/SBA-15 was the optimal catalyst for steam reforming of JP-10 even with a higher LHSV and fuel gas concentration, and approximately 100% conversion of JP-10 with over 80% selectivity to hydrogen under the recommended experimental conditions of 680 °C, S/C of 5, LHSV of 10 ml/gcat·h. The catalytic activity of 8Ni/SBA-15 dropped slowly to 84% after 6.5 h in the stability test and the carbon deposited was less with just 6% mass loss from TGA measurement (coke deposition rate 0.01gC/gcath), which ascribed to possible reasons including confine effect of mesochannel of SBA-15, strengthened structure of mesochannels due to embeded Ni particles, and higher temperature to suppress the main carbon producing reaction.

Role of TiO2-based photocatalysts on the synthesis of the pharmaceutical precursor benzhydrol by UVA-LED radiation

The influence of several reactional parameters was investigated on the photocatalytic reduction of benzophenone to the pharmaceutical precursor benzhydrol under UVA-LED radiation. The optical semiconductor titanium dioxide was loaded with 1.0 wt.% of noble metals (Pd, Pt and Au) by incipient wetness impregnation method. The TiO2-based materials were characterized by various techniques. Results showed that the benzhydrol selectivity is highly influenced by the nature of the solvent and the presence of KOH (acting as nucleophilic agent). The most efficient system was obtained using 2-propanol, 5.0 mM of KOH and 0.1 g L−1 of catalyst, achieving 100 % selectivity of benzhydrol after 10 min reaction. Among the TiO2-based materials, the Pd/TiO2 showed high efficiency for benzhydrol formation (in absence KOH) with an enhancing of c.a. 49 % compared with neat TiO2. The decrease of photoluminescence intensity observed for Pd/TiO2 material suggests an effective electron transfer from TiO2 to Pd nanoparticles.

Catalytic wet peroxide oxidation of phenol on Fe-ZSM-5/PSSF membrane catalysts: Effect of framework Fe by hydrothermal synthesis

Two kinds of zeolite membrane catalysts, Fe–ZSM-5/PSSF and Fe2O3/ZSM-5/PSSF, were synthesized by hydrothermal method and incipient wetness impregnation method respectively, and tested for catalytic wet peroxide oxidation (CWPO) of phenol in the fixed bed reactor. The paper-like stainless steel fiber (PSSF) were prepared by a combined papermaking and sintering process. Then hydrothermal and impregnation methods were applied to coat Fe–ZSM-5 as well as Fe2O3/ZSM-5 membrane catalyst on PSSF respectively. Framework Fe3+ species on the Fe–ZSM-5/PSSF zeolite membrane catalysts were characterized and tested for phenol oxidation in the fixed bed reactor. In addition, the effects of Si/Fe, temperature and residence time on catalyst performance were investigated. Results showed that Fe–ZSM-5/PSSF with Si/Fe = 120 showed highest activity. Higher temperature and longer residence time can improve the catalytic performance and the existence of the framework Fe3+ species over Fe–ZSM-5/PSSF can enhance the catalytic efficiency of phenol, with phenol conversion of over 99.0% and TOC conversion of 55.6% under condition of 4 cm bed height, 2 mL/min feed flow rate and 80 °C. Catalytic activity of Fe–ZSM-5/PSSF was dramatically increased compared to the Fe2O3/ZSM-5/PSSF, indicating the key role of framework Fe3+ played in the CWPO process. Finally, the stability test results showed that a relatively low decrease in activity of Fe–ZSM-5/PSSF (Si/Fe = 120) can be found after three consecutive runs (21 h).

The relationship between acidity, dispersion of nickel, and performance of Ni/Al-SBA-15 catalyst on eugenol hydrodeoxygenation

Catalytic hydrodeoxygenation (HDO) is considered as one of the most efficient methods for lignin-derived bio-oils upgrading. To reveal the relationship between the characters of Ni/Al-SBA-15 and the catalytic activity of eugenol hydrodeoxygenation in aqueous phase, Al-SBA-15 with different Si/Al ratios were synthesized using acid free method and corresponding Ni/Al-SBA-15 catalysts were prepared by incipient wetness impregnation method. The physicochemical characteristics were obtained by advanced instruments. The highest degree of nickel dispersion on Al-SBA-15 was obtained when the Si/Al ratio was 132 and the corresponding smallest average active nickel particle diameter is 38 nm. The adsorption and dispersion of nickel onto Al-SBA-15 was significantly relevant with the ratios of Brønsted acid site to Lewis acid site as well as the ratios of weak acid site to strong acid site. HDO experiments were carried out over Ni/Al-SBA-15 with different Si/Al ratios. 16Ni/S2-R catalyst with high quantity of acid sites and good dispersion of nickel showed high catalytic activity during hydrodeoxygenation of eugenol. A possible reaction mechanism was concluded based on the reaction results.

Improved Catalytic Performance of Ethane Dehydrogenation in the Presence of CO2 over Zr-Promoted Cr/SiO2.

The Zr-, Ce-, Sr-, and Sn-promoted Cr/SiO2 catalysts were prepared by the incipient wetness impregnation method, then characterized by N2 adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, H2-TPR, CO2-TPD, UV–vis, high-angle annular dark-field imaging–scanning transmission electron microscopy—energy dispersive X-ray spectroscopy elemental mapping, Raman, and thermogravimetric techniques to study the structural evolution under the preparation/reaction conditions, and applied to catalyze ethane oxidative dehydrogenation with CO2. The results suggested that the Cr6+ species were indispensable for activating the dehydrogenation reaction thanks to the oxidation–reduction cycle between Cr6+ and Cr3+. The type of the promotor also affected significantly the ability of replenishing the lattice oxygen through the disassociation of CO2, leading to the different catalytic performances. The Zr-promoted sample had the best performance in converting the reactants as well as the catalytic stability.

Profound synergetic effect of metal oxide promoters and TiO2–SiO2 binary support in cobalt Fischer‐Tropsch catalyst

AbstractA series of cobalt catalysts supported on TiO2, SiO2, or a mixture of them, incorporated with some added oxides from Groups III, IV, and V of transition metals, were prepared using the incipient wetness impregnation method. For better evaluation of catalysts, the physicochemical properties of catalysts were investigated using brunauer‐emmett‐teller (BET), H2‐TPR, NH3‐TPD, X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy techniques. The performance of catalysts was studied in a fixed‐bed reactor at 220°C, 24 bar, gas hourly space velocity (GHSV) of 2 L/h/gcat., and H2 to CO ratio of 2. The results indicate that CeO2 and ZrO2 as promoters can enhance the CO conversion and catalyst activity and enhance the selectivities of higher‐molecular‐weight products. On the contrary, the presence of V2O5 as a promoter undesirably suppressed CO conversion and, consequently, catalytic performance. The results show that the catalyst included CeO2, was supported on a binary mixture of SiO2 and TiO2, and has significant improved activity and C5+ selectivity. From the reactor test, values of 156.48 mmol COconv./gCo/h activity, and 0.17 gC3+/(h.gcat.) productivity have been obtained for this catalyst.

A New One-Pot Sequential Reduction-Deposition Method for the synthesis of Silica-supported NiPt and CuPt Bimetallic Catalysts

A one-pot redox deposition method is described to prepare silica-supported bimetallic NiPt and CuPt catalysts using differences in standard reduction potentials. The synthesis involved the initial reduction of non-noble metal ions (Ni2+ and Cu2+) by NaBH4, followed by reduction of Pt ions by these reduced metals. Alloy formation and phase purity were established by X-ray diffraction (XRD), bulk composition by X-ray fluorescence (XRF), and surface composition by X-ray photoelectron spectroscopy (XPS). Alloy formation was enhanced by increase in the amount of base metals available to reduce Pt, or through the use of excess NaBH4 after redox deposition. The catalysts were evaluated for methane oxidation at 300-400 °C and atmospheric pressure. Reference samples prepared using the incipient wetness impregnation (IW) method had inferior performance and characteristics. The redox deposition method provides a simple and versatile protocol for the preparation of bimetallic alloys between noble metals and base metals.

A novel strategy to design PtPd bimetallic catalysts for efficient methane combustion

A new two-step method of combining colloid synthesis and incipient wetness impregnation routes was followed for the synthesis of a Pt-PdO bimetallic catalyst for methane combustion. The catalyst was characterized by powder XRD, XPS, TPO and in-situ DRIFTS. The results have demonstrated that there is almost no PtPd alloy formed over the bimetallic catalyst. Compared with the bimetallic catalyst of same nominal composition prepared by the traditional incipient wetness impregnation method, the redox properties of the catalyst were significantly improved. The catalyst showed an exceptional low-temperature activity for methane oxidation. It was found that the concentration of hydroxyl groups over the catalyst was greatly reduced during methane combustion. The present study may provide a general method for the preparation of bimetallic nanoparticles with high activity towards other heterogeneous catalytic reactions.

Degradation of Ethylene Glycol Through Photo-Fenton Heterogeneous System

This work describes the ethylene glycol degradation in a photo-Fenton heterogeneous system. Iron-doped TiO2 photocatalysts prepared by different methods (incipient wet impregnation and sol-gel method), as well as the corresponding un-doped material were examined in this process. Different values of initial pH and H2O2 concentration were tested during the experiments. A lower photoactivity was observed for the un-doped materials than for the Fe-doped materials. Optimum results of initial pH and H2O2 concentrations were found to be 3.0 and 1,000 mg/L, respectively. Furthermore, the highest degradation percentage of ethylene glycol (61 %) was achieved for the material synthetized by sol-gel method. Such catalytic performance is explained on the basis of structural/morphological and electronic characterization results, reached by XRD, UV-vis DRS and XPS techniques. To the best of our knowledge, this is the first report related with the ethylene glycol degradation using Iron-doped TiO2 in a photo-Fenton heterogeneous system.

Catalytic conversion of 5-hydroxymethylfurfural (5-HMF) over Pd-Ru/FAU zeolite catalysts

We present this study on FAU-type zeolites were prepared varying the Si/Al ratio (4, 5 and 6) and crystallization time (4, 6 and 8 h) to produce a highly pure and homogeneous material with enhanced surface area values. Bimetallic Pd-Ru and Pt-Ru (0.5 wt.% of each metal) were impregnated onto the zeolites matrix by the incipient wetness impregnation method. The materials were characterized by X-ray diffraction (XRD), nitrogen physisorption, Fourier Transform Infrared spectroscopy (FT-IR), Scattering Electronic Microscopy (SEM), Scattering and Transmission Microscopy (STEM), temperature-programmed desorption (TPD), temperature-programmed desorption (TPR) and Inductively Couples Plasma- Mass Spectrometer (ICP-MS). Results indicated that using lower Si/Al ratios favored the catalytic activity. Also, the longest crystallization time had a positive effect on surface area, homogeneous particle size distribution and crystallinity. The catalytic performance in the esterification of 5-hydroxymethylfurfural (5-HMF) to produce 5-acetoxymethylfurfural (AcMF) was investigated. The maximum 5-HMF conversion of 87.28 % was achieved using pure zeolite with relation Si/Al = 5, and 8 h of crystallization. Pd-Ru supported onto same zeolite showed a conversion of 84.22 %. The highest selectivity towards AcMF of 71.29 % with pure zeolite Si/Al = 5 and 8 h of crystallization was achieved, followed by Pd-Ru/FAU with Si/Al = 5 and 8 h of crystallization, achieving 60.42 %. Finally, results shown that the interaction between the properties of zeolitic support and the metallic species, specifically Pd, had a positive effect in the catalytic process the pristine zeolite showed improved catalytic characteristics related to its acid strength.

NO reduction by CO over CoOx/CeO2 catalysts: Effect of support calcination temperature on activity

CeO2 supported CoOx catalysts showed promising results in many NO reduction processes including NO reduction by CO. In this work, a series of CeO2 supports with different calcination temperatures (as received-800 °C calcination) were prepared, followed by the synthesis of a series of CoOx/CeO2 catalysts with a surface density of 2.5 Co/nm2 using the incipient wetness impregnation method. To understand the physicochemical properties of catalysts, various characterizations techniques, including BET, Raman spectroscopy, XRD, and H2-TPR, were performed. The results showed that as calcination temperature increased, physical properties of supporting materials were changed. Surface CoOx improved the reducibility of CeO2, but it was not affected by the support calcination temperatures confirmed by H2-TPR. The presence of CoOx was crucial to enhance the catalytic activity during the NO reduction by CO reaction, rather than physical properties (surface area, pore size, particle size) of the catalyst.

Multifunctional and Environmentally Friendly TiO2-SiO2 Mesoporous Materials for Sustainable Green Buildings.

This work deals with the formulation of environmentally friendly, cheap, and readily-available materials for green building applications, providing the function of air purificator by improving the safety and the comfort of an indoor environment. High surface area TiO2–SiO2 samples, prepared by a simple, cost effective, and scalable synthetic approach, proved to be effective in maximizing the properties of each component, i.e., the photocatalytic properties of titania and the high surface area of silica. TiO2 was introduced onto an ordered mesoporous silica Santa Barbara Amorphous-15 (SBA-15), that is featured by interesting insulating features, by using an incipient wetness impregnation method. The photocatalytic activity was evaluated in gas phase oxidation of ethylbenzene, which was selected as model volatile organic compound (VOC) molecule. The morphological, textural and structural features along with the electronic properties, the hydrophilicity and heat capacity of the materials were investigated in depth by scanning electron microscopy, powder X-ray diffraction, N2 physisorption, diffuse reflectance UV-Vis, FT-IR spectroscopies, and modulated DSC (MDSC) dynamic scan. Outstanding performances in the ethylbenzene abatement results are promising for further application in the green building sector.

Hydrogen production over Co-promoted Mo-S water gas shift catalysts supported on ZrO2

A series of CoMo-S/ZrO2 catalysts were prepared by modifying Co and Mo content using incipient wetness impregnation method, investigated in the water gas shift (WGS) reaction in the presence of H2S and characterized by TEM, XRD, Raman, TPR, and XPS. The supported CoMo-S catalyst corresponding to the CoMo-O monolayer coverage displayed the presence of highly dispersed CoMo-S species that were characterized by the highest extent of sulfidation. The presence of cobalt facilitated the formation of active CoMo-S species that were more H2S-dependent as compared to Mo-S entities. The Co/Mo = 0.3 catalyst at monolayer CoMo-O coverage was the most active and thermally stable, as well as the least H2S-dependent during 4 weeks of WGS reaction among all catalysts investigated.