Incipient Wetness Impregnation Catalyst Research Articles

Effects of Pt site distributions on the catalytic performance of Pt/SAPO-11 for n-dodecane hydroisomerization

A series Pt/SAPO-11 were prepared by using incipient wetness impregnation (IWI) and colloidal impregnation (CI) methods. TEM, STEM, CO-FTIR and H2 chemisorption were employed to study the effects of preparation method on the distributions of Pt sites. The catalytic performance of Pt/SAPO-11 was evaluated by using n-dodecane as the model reactant in a fixed-bed reactor. The characterization results suggested that the Pt sites on IWI catalyst could be mainly distributed near the micropore mouth of SAPO-11, while the Pt sites on CI catalyst could be mainly distributed on the external surface. In n-dodecane hydroisomerization, IWI catalyst showed higher activity and isomerization selectivity than CI catalyst. Possible relationships between the distributions of Pt sites and the catalytic performance of Pt/SAPO-11 were discussed.

Chemoselective hydrogenation of cinnamaldehyde at atmospheric pressure over combustion synthesized Pd catalysts

A series of Pd-supported metal oxides (Al2O3, Fe2O3 and CeO2) have been prepared by a single step solution combustion synthesis (SCS) method. Their catalytic performance was evaluated for the selective hydrogenation of cinnamaldehyde (CAL) to hydrocinnamaldehyde (HCAL) under atmospheric pressure of hydrogen at 100 °C. Among these materials, combustion synthesized Pd (2 at.%)/Al2O3 catalyst exhibits the highest CAL conversion (69%) with complete HCAL selectivity. The analogous catalyst prepared by the incipient wetness impregnation (IWI) method shows an initially similar activity. X-ray diffraction and high resolution transmission electron microscopy analyses of the as prepared SCS sample show fine dispersion of PdO over the γ-Al2O3 support. On ageing, a major portion of PdO is reduced to metallic Pd (Pd2+:Pd0 = 36:64 for the SCS catalyst and Pd2+:Pd0 = 26:74 for the IWI catalyst from X-ray photoelectron spectroscopy studies) suggesting comparatively more ionic character of palladium in the SCS catalyst. In the hydrogen atmosphere, without distinguishing the reductive pretreatment of catalyst and the beginning of hydrogenation subsequent to CAL addition, the Pd-species undergoes rearrangement to form a core–shell like structure of Pd (core)–PdO (periphery) covered with alumina layer, bringing in additional stability to the Pd-species in the SCS catalyst and making it highly recyclable. The analogous IWI catalyst, on the contrary, contains a mixed Pd–PdO ensemble that does not increase the stability causing continuous loss of activity in the consecutive cycles of hydrogenation.

Fischer–Tropsch Synthesis: Influence of Acid Treatment and Preparation Method on Carbon Nanotube Supported Ruthenium Catalysts

The influences of nitric acid treatment on a carbon nanotube (CNT) support and the preparation method, incipient wetness impregnation (IWI) versus chemical vapor deposition (CVD), on catalytic performance during Fischer–Tropsch (FT) synthesis were examined using a slurry phase reactor. Acid treated CNT (ACNT) supported Ru catalysts exhibited higher activities compared to Ru supported on untreated CNTs (UCNTs). The acid-treated CVD catalyst had higher initial CO conversion (smaller average Ru particle size) but sintered more due to a greater tendency for Ru to be deposited exterior to CNT channels relative to IWI. After the initial decline and leveling off period, the ACNT IWI catalyst had the highest steady activity among the catalysts tested. The ACNT IWI catalyst also displayed greater oxygenate selectivity (∼17%) compared to ACNT CVD (∼12%) and UCNT IWI (∼10%) catalysts at similar conversions. Acid treatment created adsorption sites on the CNT surface that anchor Ru precursors and promote CO insertion ...

Coatings of active and heat-resistant cobalt-aluminium xerogel catalysts

The application of catalytically coated metallic foams in catalytic processes has a high potential for exothermic catalytic reactions such as CO2 methanation or Fischer-Tropsch synthesis due to good heat conductivity, improved turbulent flow properties and high catalyst efficiencies. But the preparation of homogenous catalyst coats without pore blocking is challenging with conventional wash coating techniques. Here, we report on a stable and additive free colloidal CoAlOOH suspension (sol) for the preparation of catalytically active Co/Al2O3 xerogel catalysts and coatings. Powders with 18wt% Co3O4 prepared from this additive free synthesis route show a catalytic activity in Fischer-Tropsch synthesis and CO2 methanation which is similar to a catalyst prepared by incipient wetness impregnation (IWI) after activating the material under flowing hydrogen at 430°C. Yet, the xerogel catalyst exhibits a much higher thermal stability as compared to the IWI catalyst, as demonstrated in catalytic tests after different heat agings between 430°C and 580°C. It was also found that the addition of polyethylene glycol (PEG) to the sol influences the catalytic properties of the formed xerogels negatively. Only non-reducible cobalt spinels were formed from a CoAlOOH sol with 20wt% PEG. Metallic foams with pores sizes between 450 and 1200μm were coated with the additive free CoAlOOH sol, which resulted in homogenous xerogel layers. First catalytic tests of the coated metal foams (1200μm) showed good performance in CO2 methanation.

Synergetic Behavior of TiO2‐Supported Pd(z)Pt(1−z) Catalysts in the Green Synthesis of Methyl Formate

AbstractMethyl formate (MF) is a valuable platform molecule, the industrial production of which is far from being green. In this contribution, TiO2‐supported Pd(z)Pt(1−z) catalysts were found to be effective in the green synthesis of methyl formate (MF)—at T=323 K and ambient pressure—through methanol (MeOH) oxidation. Two series of catalysts with similar bulk Pd/(Pd+Pt) molar ratios, z, were prepared; one by a water‐in‐oil microemulsion (MicE) method and the other by an incipient wetness impregnation (IWI). The MicE method led to more efficient catalysts owing to a weak influence of z on particle size distributions and nanoparticles composition. Pd(z)Pt(1−z)‐MicE catalysts exhibited strong synergistic effects for MF production but weak synergistic effects for MeOH conversion. The catalytic performance of Pd(z)Pt(1−z)‐MicE was superior to that of Pd(z)Pt(1−z)‐IWI catalysts despite the latter displaying synergetic effects during the reaction. The catalytic behavior of TiO2‐supported Pd(z)Pt(1−z) catalysts was explained from correlations between XRD, TEM, and X‐ray photoelectron spectroscopy characterizations.

Quantitative Nuclear Magnetic Resonance Spectroscopy as a Tool To Evaluate Chemical Modification of Deep Hydrotreated Recycled Lube Oils

The applications of 1H and 13C nuclear magnetic resonance (NMR) and two-dimensional 1H/13C NMR spectroscopy have been shown to be useful techniques for the qualitative and quantitative characterization of hydrotreated recycled lube oils. The addition of hydrogen to aromatic and alkene hydrocarbons can be quantitatively and selectively measured. The decrease of oxygen/nitrogen/sulfur species can also be inferred from the reduction of specific resonances in the NMR spectra. Treated recycled lube oil was subsequently hydrotreated with Pd catalysts deposited by either atomic layer deposition (ALD) or incipient wetness impregnation (IWI) on a SiO2/Al2O3 support. In both cases, much lower hydrogenation temperatures were required than had been observed with typical NiMo or CoMo on Al2O3. In addition, the ALD-deposited catalyst was more effective for the reduction of aromatics and heteroatom components than the IWI catalyst. The lube oil fractions were of high purity (low aromaticity and low heteroatom content) even at low reaction severity.

Comparison of differently synthesized Ni(Al)MCM-48 catalysts in the ethene to propene reaction

MCM-48 has been prepared by four synthesis routes varying in hydrothermal treatment, pH, surfactant and silica source. These materials have been functionalized with nickel and aluminum via incipient wetness impregnation (IWI) and template ion exchange (TIE). The support and the final catalysts were characterized using nitrogen physisorption, powder X-ray diffractometry (PXRD) and ICP-OES. Textural analysis showed that the definite structure of the support was retained with IWI and was partly affected by TIE. Upon IWI small nickel oxide particles on the surface were formed, whereas with TIE no nickel-related crystalline phases could be detected. The optimal nickel and aluminum loadings were found for IWI- and TIE-MCM-48 concerning the catalytic activity in the ethene to propene reaction (ETP). With ethene conversion of over 40% propene selectivity of up to 56% could be reached with IWI and TIE catalysts. The preparation method of the MCM-48 had more influence on the activity of the TIE catalysts than of the IWI ones.

Thermally Impregnated Ni−Olivine Catalysts for Tar Removal by Steam Reforming in Biomass Gasifiers

A novel and potentially economic preparation technique, thermally impregnation (TI), was developed to incorporate catalytic active materials (i.e., Ni) onto olivine. The approach allows for the synthesis of attrition-resistant Ni−olivine catalysts. Comparative studies were performed over Ni−olivine catalysts prepared by TI and traditional incipient wetness impregnation (IWI), as well as olivine without Ni. Various characterization techniques such as BET surface area analysis, temperature-programmed reaction/oxidation/reduction, XRD, and XPS were performed to examine the catalysts. The Ni−olivine catalyst prepared by TI demonstrated improved activity and “coke selectivity” compared to the olivine support, indicating that Ni is necessary for enhanced activity. Additionally, the Ni−olivine catalyst prepared by TI showed similar high-temperature activity and decreased coke deposition rates compared to similar formulations prepared by IWI. Stronger interactions between Ni and the olivine support for the TI catalyst were responsible for the improved catalytic properties compared to IWI catalysts. Moreover, effects of pretreatment and reaction parameters such as temperature and time-on-stream (TOS) were studied. The reaction network in simulated biomass-derived syngas was also investigated to probe the possible reactions occurring in a biomass gasifier. The Ni−olivine catalyst prepared by TI possessed catalytic activity for several reactions such as the water gas shift (WGS), reverse WGS, methanation, and Boudouard reactions.

Preparation and characterization of inexpensive heterogeneous catalysts for air pollution control: Two case studies

Relatively inexpensive heterogeneous catalysts for two reactions of great importance in air pollution control, NO reduction and VOC combustion, were prepared and characterized. Apart from their common practical goal and the frequent need for simultaneous removal of air pollutants, these reactions share a similar redox mechanism, in which the formulation of more effective catalysts requires an enhancement of oxygen transfer.For NO reduction, supported catalysts were prepared by adding a metal (Cu, Co, K) using ion exchange (IE) and incipient wetness impregnation (IWI) to chars obtained from pyrolysis of a subbituminous coal. The effects of pyrolysis temperature, between 550 and 1000°C, on selected catalyst characteristics (e.g., BET surface area, XRD spectrum, support reactivity in O2) are reported. For IE catalysts, the surface area increased in the presence of the metals while the opposite occurred for IWI catalysts. For the Co-IE catalysts, the highest surface area was obtained at 700°C. The XRD results showed that, except for Cu (which exhibited sharp Cu0 peaks), the catalysts may be highly dispersed (or amorphous) on the carbon surface. For the C–O2 reaction the order of (re)activity was K≫Co>Cu for IE catalysts and K>Cu>Co for IWI catalysts. For NO reduction the orders were K>Co>Cu (IE catalysts) and Cu>Co>K (IWI catalysts). In all cases the catalytic (re)activity for NO reduction was lower than that exhibited for the C–O2 reaction. The K-IE and Cu-IWI catalysts appeared to be the most promising ones, although further improvements in catalytic activity will be desirable. Some surprising results regarding CO and CO2 selectivity are also reported, especially for Co catalysts.In VOC combustion, the effect of the nature of ion B (Fe and Ni) on the partial substitution of ion A (Ca for La) in ABO3 perovskites (e.g., LaFeO3 and LaNiO3) and on their catalytic activity was studied. The perovskite-type oxides were characterized by means of surface area measurements, XRD, temperature-programmed desorption (TPD) and temperature-programmed reduction (TPR). The effect of partial substitution of La3+ by Ca2+ was more significant for the La1−xCaxFeO3 perovskites. In this case, the electronic perturbation is compensated by an oxidation state increase of part of Fe3+ to Fe4+. The TPD results revealed that, at higher substitution levels, oxygen vacancies are also formed to preserve electroneutrality. For the La1−xCaxNiO3 perovskites, the characterization results showed no evidence of large differences in electronic properties as calcium substitution increases. The La1−xCaxNiO3 perovskites exhibited lower activity than the simple LaNiO3 perovskite, whereas for the La1−xCaxFeO3 substituted perovskites the most active catalyst (exhibiting the lowest ignition temperature) was obtained at the highest substitution level, La0.6Ca0.4FeO3.The performance of both groups of catalysts is briefly discussed in terms of redox processes, in which the interplay between oxygen transfer and electron transfer requires further elucidation for the improvement of catalytic activity.

Nano-structured CeO 2 supported Cu-Pd bimetallic catalysts for the oxygen-assisted water–gas-shift reaction

The present work focuses on the development of novel Cu-Pd bimetallic catalysts supported on nano-sized high-surface-area CeO 2 for the oxygen-assisted water–gas-shift (OWGS) reaction. High-surface-area CeO 2 was synthesized by urea gelation (UG) and template-assisted (TA) methods. The UG method offered CeO 2 with a BET surface area of about 215 m 2/g, significantly higher than that of commercially available CeO 2. Cu and Pd were supported on CeO 2 synthesized by the UG and TA methods and their catalytic performance in the OWGS reaction was investigated systematically. Catalysts with about 30 wt% Cu and 1 wt% Pd were found to exhibit a maximum CO conversion close to 100%. The effect of metal loading method and the influence of CeO 2 support on the catalytic performance were also investigated. The results indicated that Cu and Pd loaded by incipient wetness impregnation (IWI) exhibited better performance than that prepared by deposition–precipitation (DP) method. The difference in the catalytic activity was related to the lower Cu surface concentration, better Cu–Ce and Pd–Ce interactions and improved reducibility of Cu and Pd in the IWI catalyst as determined by the X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) studies. A direct relation between BET surface area of the CeO 2 support and CO conversion was also observed. The Cu-Pd bimetallic catalysts supported on high-surface-area CeO 2 synthesized by UG method exhibited at least two-fold higher CO conversion than the commercial CeO 2 or that obtained by TA method. The catalyst retains about 100% CO conversion even under extremely high H 2 concentration.

Study of preparation parameters of powder and pelletized Pt/KL catalysts for n-hexane aromatization

Pt/KL powder and pelletized catalysts were synthesized by different methods including ion exchange (IE), incipient wetness impregnation (IWI), and vapor phase impregnation (VPI) methods. A detailed characterization was conducted on the various samples in order to determine the distributions of Pt particle size and location resulting from each preparation, as well as the relationships between these distributions and the catalytic performance. The catalysts were pretreated at two different reduction temperatures — 400 and 500°C — to investigate the sensitivity of each catalyst to thermal treatment. All catalysts showed high dispersion, with H/Pt ratios greater than unity. However, FTIR of adsorbed CO showed that more important than dispersion, it is the distribution of Pt cluster size and location, which influences the resulting catalytic stability. Standard IE catalysts were found to have a high fraction of Pt particles external to the L-zeolite and were the most sensitive to thermal treatment, displaying Pt migration out of the L-zeolite. These catalysts deactivated rapidly by coke formation. The addition of excess K + ions in the exchange solution and a longer aging period, as suggested in the patent literature, improves the Pt dispersion. IWI and VPI catalysts showed a majority of Pt clusters inside the L-zeolite channels. However, after high temperature reduction treatment, the IWI catalysts displayed particle growth inside the channels, in contrast with the VPI. The IWI catalysts were found to deactivate to about half their initial activity, while the VPI maintained the highest activity and stability. Different VPI methods including a moderate vacuum and a helium flow technique were examined and they showed similar Pt cluster distributions and catalytic performance to the catalysts synthesized using high vacuum. Preparation directly on the pellet for the methods investigated in this work (standard IE, IWI, and VPI) resulted in large fractions of Pt clusters external to the pores and likely on the binder. Thus, rapid deactivation by coke formation was evident. These results indicate that pelletized catalysts prepared by any of these techniques would require preparation on the powder prior to pellet extrusion.

Effect of KCl Addition Method on the Pt/Kl Catalyst for the Aromatization of Hexane

The influence of the method for loading platinum precursor and adding KCl, KCl loading content, calcination temperature, KCl addition procedure, various additives, and water washing on the activity and selectivity of Pt/KL catalysts for hexane reforming reaction has been investigated. The catalyst preparation methods involve ion exchange (IE), incipient wetness impregnation (IWI), and coimpregnation with KCl (IWI-KCl). The Pt/KL catalysts prepared by ion exchange with [Pt(NH3)4]Cl2 followed by impregnation with KCl (IE-KCl) gave much higher activity and selectivity for benzene formation than the catalysts prepared by coimpregnation of KL zeolite with [Pt(NH3)4]Cl2 and KCl. The IE-KCl catalyst with KCl/Pt molar ratio of 4.5 showed 100.0% conversion of hexane and 89.3% yield of benzene at 743 K and 0.2 MPa. The IE-KCl catalysts exhibited lower H/Pt ratios than the IE catalyst. The KCl addition procedures markedly affected the activity and selectivity of the Pt/KL catalyst; the addition of KCl to the IE sample prior to calcination and reduction was necessary for the catalyst to exhibit the high activity in benzene formation. It has also been found that the performance of Pt/KL catalysts is markedly affected by the calcination temperature. With the IE-KCl catalysts, however, the decrease in the benzene yield caused by high-temperature calcination was not as serious as with the IE catalyst. In contrast, with the IWI and IWI-KCl catalysts, the activity for benzene production was highly sensitive to the calcination at high temperature, drastically decreasing by calcination at 823 K. The Cl species on the IE-KCl catalysts may have existed in the state of KCl.

Comparison of Pt/KL catalysts prepared by ion exchange or incipient wetness impregnation

Pt/KL catalysts prepared by ion exchange (IE), incipient wetness impregnation (IWI), and coimpregnation with KCl (IWI + KCI) have been characterized by dynamic techniques, chemisorption of H 2 and CO, Fourier transform-infrared spectroscopy (FT-IR) of adsorbed CO, and catalytic tests using n-hexane ( n-C6) and methylcyclopentane (MCP) conversions as probe reactions. Temperature-programmed reduction (TPR) shows significant differences between the IE and IWI catalysts. After calcination up to 400°C, the IWI samples contain Pt 4+ ions that are reduced at 250°C, but IE samples contain Pt 2+ particles that are reduced at 11°C, besides two Pt 2+ species with TPR peaks at 80 and 150°C. High-resolution electron microscopy, adsorption, FT-IR, and catalytic results consistently show that, after reduction, the IWI catalysts contain smaller Pt particles located inside the zeolite channels, while the IE sample has larger particles, some of which are on the external surface. At high temperature, excess KCI reacts with zeolite protons, forming HCl which escapes. In comparison to the IE samples, the IWI catalysts are less acidic, less active for n-C 6 conversion, more selective for dehydrocyclization, but less selective for hydrogenolysis, and they deactivate less. Since hydrogenolysis requires large Pt ensembles, the small Pt particles in the IWI catalysts produce less C 1C 5 compounds and less coke. The product distribution of MCP ring opening shows higher than statistical selectivity toward 3-methylpentane, suggesting that the MCP molecule becomes oriented inside the zeolite channels.