NH3 Temperature-programmed Desorption Research Articles

Mesoporous silica supported phosphotungstic acid catalyst for glycerol dehydration to acrolein

Conversion of glycerol to acrolein is a useful reaction for value-added application of biodiesel-derived glycerol and bioenergy development. The high-performance solid acid catalyst is essential to this dehydration reaction. In this paper, tungsten-based heteropolyacids (HPA) were supported on non-ordered mesoporous silica (MSU-x) to increase their dispersion and used as catalysts for glycerol dehydration to acrolein. Aiming to reveal the surface structure of HPA and resulting acidic properties, as well as the relationship between acidic properties and dehydration activity, different loadings of H3PW12O40 were supported on MSU-x (10–50 wt%) and the catalysts were characterized by X-ray diffraction (XRD), BET, SEM/TEM, UV–vis diffuse reflectance spectra (DRS), Raman and FT-IR techniques. Their acidic properties were studied by NH3-Temperature Programmed Desorption (NH3-TPD) and Pyridine adsorption methods. The molecular structure and dispersion of H3PW12O40 supported on the catalysts was revealed. The Keggin unit preserved well but with different hydration level for various loadings. The total acid concentration and respective Brønsted/Lewis acid identification were calculated. The acrolein yield increased with H3PW12O40 loading until 30 wt% and showed less change with higher loadings. Based on the correlation of acrolein formation rate with acidic properties, the active role of Brønsted acid and the cooperative role of Brønsted/Lewis acid sites for glycerol dehydration to acrolein were discussed. This work provides new insight into the structure evolution of heteropolyacids and the catalyst design for the glycerol to acrolein.

Preparation, Characterization, and Kinetics Model of MoCo/γ-Al2O3 Catalysts for Oxidative Desulfurization of Light Naphtha

The subject of this work is to study the effect of pH, molybdenum content and some of the transition metals (such as Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel) on the catalyst properties and performance of oxidative desulfurization (ODS). To achieve this aim, the mesoporous 5%Co10%Mo/γ-Al2O3 catalyst was prepared by incipient wetness impregnation method. Then, the as-synthesized catalysts were characterized by X-Ray Diffraction (XRD), N2-adsorption/desorption, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Scanning Electron Microscopy (SEM) and NH3-Temperature Programmed Desorption (NH3-TPD). The catalytic activity was measured with catalytic ODS setup. The catalyst with 10wt%Mo (as an active metal) and 5wt%Co content (as a promoter) at pH=4 represented the optimum performance for oxidative desulfurization. The 5%Co10%Mo/γ-Al2O3 has the Surface Area =170.61 m2/g, Pore Volume =0.64 cm3/g, Average Pore Diameter = 15.18nm when these parameters were increased, it led to the best operation condition of sulfur removal. The SEM images showed that the application of Co and Mo metals reaches more homogenous impregnation. The NH3-TPD result introduced the strong acidic sites of 5%Co10%Mo/γ-Al2O3. The obtained results proved that the total sulfur (all kind of sulfur in the feed) of light naphtha decreased from 160ppm to 20ppm during ODS process with the optimized catalyst. In that case, the kinetics of oxidative desulfurization of the optimized catalyst (5%Co10%Mo/γ-Al2O3) was studied. Moreover, a kinetic affinity model was utilized to determine the kinetic parameters of this reaction and the modeling results showed good agreement with experimental data.

Catalytic Activity of Mixed Al2O3-ZrO2 Oxides for Glucose Conversion into 5-Hydroxymethylfurfural

In the present work, a series of catalysts based on aluminum and zirconium oxides was studied for the transformation of glucose into 5-hydroxymethylfurfural. These catalysts were characterized by using experimental techniques, such as X-ray diffraction, N2 adsorption–desorption at −196 °C, X-ray photoelectron spectroscopy, temperature-programmed desorption of NH3 and CO2, and scanning transmission electron microscopy. The catalytic behavior in glucose dehydration was evaluated in a water-methyl isobutyl ketone biphasic system, in the presence of CaCl2, in order to minimize losses due to unwanted secondary reactions. High glucose conversion and 5-hydroxymethylfurfural (HMF) yield values were obtained in the presence of an Al(Zr)Ox catalyst with an Al:Zr molar ratio of 7:3, reaching 97% and 47%, respectively, at 150 °C after 120 min. Under tested conditions, this catalyst retained most of its catalytic activity for four reuses.

Niobium Oxides as Heterogeneous Catalysts for Biginelli Multicomponent Reaction.

This study reports a simple, reusable, and recoverable niobium-based heterogeneous catalysts for Biginelli multicomponent reactions. Different methods of catalysts preparation were investigated. For this purpose, HY-340 (Nb2O5·nH2O) and Nb2O5 were chemically and/or thermally treated and investigated as catalysts for dihydropyrimidinones (DHPMs) production. The catalysts were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, temperature-programmed desorption of NH3, adsorption/desorption of N2 at -196 °C, and thermogravimetric and differential thermal analysis. The characterization results showed that niobium oxides have the potential to be used as catalysts because of high crystallinity and large surface area. Among the tested catalysts, Nb2O5 chemically treated (Nb2O5/T) showed the best catalytic performance. In the absence of solvents, 94% yield of DHPMs was achieved. Also, Nb2O5/T can be reused three times without a significant yield decrease. Additionally, a feasible reaction pathway was suggested based on the Knoevenagel mechanism for DHPM synthesis using niobium-based catalysts.

Effect of Phosphorus Modification on the Acidity, Nanostructure of the Active Phase, and Catalytic Performance of Residue Hydrodenitrogenation Catalysts.

A series of NiMoP(x)-Al catalysts with different phosphorus contents were prepared by the incipient wetness co-impregnation method. The effects of phosphorus modification on the acidity, active phase nanostructure, and catalytic properties of the residue hydrodenitrogenation catalysts were investigated to find the role of phosphorus in the catalytic mechanism. The results of temperature-programmed desorption of NH3 and pyridine IR spectroscopy of the catalysts indicate that phosphorus modification can increase the total acid and Brønsted acid. Transmission electron microscopy analysis shows that phosphorus modification increases the stacking number NA, reduces the slab length LA of the active MoS2 phase, and increases the Mo dispersion fMo, leading to the promotion of the sulfidation degree of the active Mo phase and thus increasing the denitrification rate. The catalyst with a 3.4 wt % P2O5 loading shows the highest Brønsted/Lewis acid ratio, the largest amount of three-layer active phases, the smallest LA, the highest fMo, the optimal sulfurization degree, and the highest denitrification rate, 63.6%, indicating the correlation between the nanostructure of the active phase and its catalytic property because of the addition of phosphorus.

A novel regeneration method for deactivated commercial NH3-SCR catalysts with promoted low-temperature activities.

A novel route is developed for regeneration of deactivated commercial NH3-SCR catalysts, which includes an initial in situ construction of anatase TiO2 porous film, followed by loading of MnOx, CeOx, and Mn-Ce mixed oxides as active components. The regenerated catalysts present largely improved low-temperature denitrification performance due to the synergetic effect of MnOx and CeOx. The denitrification efficiency could reach a high value of 97% at 200°C and 100% at 250°C when the Ce-Mn mixed oxides are loaded at the optimized molar quantity ratio of 10:9 (Ce:Mn). Properties and reaction mechanisms of the regenerated catalysts are investigated with characterizations of X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (NH3-TPD), H2 temperature-programmed reduction (H2-TPR), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Our results demonstrate that the adsorption and oxidation of NO plays a crucial role for these three catalysts even though a difference exists on the reaction pathways. Graphical abstract.

Insighting into the Effect of Acid Sites on the Catalytic Performance of HZSM-5 During the One-Step Preparation of Isoprene by Formaldehyde and Isobutene

In this paper, by changing the Si/Al ratio of the catalyst, the reaction temperature and the weight hourly space velocity, the optimal reaction conditions for the preparation of isoprene in one-step condensation of isobutene and formaldehyde on HZSM-5 molecular sieve catalyst was investigated. The catalysts were characterized by N2 adsorption–desorption, X-ray diffraction (XRD), NH3-temperature programmed desorption (NH3-TPD), thermogravimetric-differential scanning calorimetry (TG-DSC) analysis and Fourier transform infrared spectra of the adsorbed pyridine (Py-IR). The catalytic performance of this reaction was studied and the possible reaction network diagram was proposed. It is concluded that the active sites of gas phase condensation between formaldehyde and isobutene were medium strong Lewis acid sites. Meanwhile the strong acid sites would cause side reactions and carbon deposition. It is speculated that the active sites of the reaction of formaldehyde and isobutene are Lewis acid sites on the HZSM-5 catalyst. The mechanism is presumed to activate the formaldehyde molecule at the Lewis acid sites, and then the formaldehyde molecule is condensed with isobutene to form isoprene.

Critical roles of Cu(OH)2 in low-temperature moisture-induced degradation of Cu-SAPO-34 SCR catalyst: Correlating reversible and irreversible deactivation

Cu-SAPO-34 selective catalytic reduction (SCR) catalyst deactivates upon exposure to water vapor at temperatures lower than 100 °C, which deteriorates its application prospects. The deactivation under cycled aging-regeneration conditions can be categorized into two stages, namely reversible and irreversible deactivation. Based on SCR reaction tests, and characterizations with diffuse reflection infrared Fourier transform spectroscopy (DRIFTS), NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR), it is concluded that the transformation of active isolated Cu(II) ions to Cu(OH)2 is critical to both types of deactivation. Within the frame of reversible deactivation, Cu(OH)2 can be converted back to SCR active Cu(II) ions by interacting with Brønsted acid sites during high-temperature regeneration. However, interactions between Cu(OH)2 and hydrolyzed framework Al lead to the formation of CuAl2O4-like species, causing permanent loss of active Cu(II) ions and thus, irreversible deactivation.

Insight into the Property Modification of Zr‐Incorporated Alumina Binary Mixed Oxides by XRD, TEM, XPS, TPD and IR

AbstractAl2O3 is known to be the most stable aluminum oxide and shows a large variety of applications. Incorporating a second metal to alumina is regarded as an effective strategy to modify its pristine material property. In this work, the binary ZrXAlOY (0 < X ≤ 1) mixed oxides synthesized by co‐precipitation method were studied by X‐ray diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), NH3 temperature‐programmed desorption (NH3‐TPD) and pyridine adsorbed infrared (IR). It was disclosed that Zr incorporation (i. e., Zr content) and calcination temperature would bring about significant modifications on the material property of ZrXAlOY compounds, such as crystal structure, valence state, surface acidity etc. Among the series ZrXAlOY mixed oxides investigated, the Zr0.1AlOY solid calcined at 400 °C presented a highest reactive surface area and a strongest interaction between Zr4+ cations and Al3+ cations, located either in the homogeneously distributed Zr‐Al mixed oxide or at the ZrO2/Al2O3 interface. Thus an optimal proportion of Lewis acid sites with strong strength was obtained on this compound, which could be beneficial to acid‐catalyzed reactions either as catalyst or support material.

Enhanced catalytic activity of Pt/H-ZSM-12 via alkaline post-treatment for the hydroisomerization of n-hexane

Abstract Bifunctional Pt/H-ZSM-12 catalysts with enhanced inter-mesoporosity were prepared from synthesized ZSM-12 samples by alkaline post-treatments with or without the presence of the template in the zeolite pores, ammonium ion-exchange, and impregnation with Pt(NH3)4Cl2. Different techniques, such as N2 adsorption-desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), NH3 temperature-programmed desorption (NH3-TPD), and pyridine-adsorption infra-red spectroscopy (Py-IR), were used to characterize the synthesized samples. The prepared Pt/H-ZSM-12 catalysts were evaluated in the hydroisomerization of n-hexane. The results show that the template-containing ZSM-12 is a better parent for introducing abundant inter-mesopores by the alkaline post-treatment, accompanying with a better preservation of microporosity and strong acid sites, in comparison to the template-free ZSM-12 as the parent. In addition, the dispersion of Pt on the alkaline-treated zeolite is increased as well, which is also helpful to enhance the conversion of n-hexane and the selectivity for the dibranched hexanes.

Role of Br\xf8nsted and Lewis acidic sites in sulfonated Zr-MCM-41 for the catalytic reaction of cellulose into 5-hydroxymethyl furfural

A series of sulfonated Zr-MCM-41 samples were synthesized by the in-situ method followed by sulfonation using sulfuric acid for the catalytic study of cellulose to 5-hydroxymethyl furfural in batch condition. All synthesized catalysts were characterized by XRD, N2 adsorption–desorption isotherm, FT-IR, TEM, EDX, and NH3 temperature-programmed desorption analysis. The XRD and N2 adsorption–desorption isotherm results have confirmed that incorporated Zr4+ was substituted within the framework of silica MCM-41 with hexagonal pores. Similarly, the FT-IR and EDX results have proved that Zr-MCM-41 was sulfonated. The Brønsted acidic and Lewis acidic sites were identified by NH3-TPD analysis. Among the sulfonated Zr-MCM-41 catalysts, S-15Zr-MCM-41 has shown 70% cellulose conversion with 16.4% selectivity of 5-hydroxymethyl furfural at 170 °C for 2 h which was higher than other catalysts. It was attributed to the high ratio of Brønsted acidic to Lewis acidic sites.Graphic abstract

A novel design of silica-based completion nanofluids for heavy oil reservoirs

The main objective of this manuscript is the design of completion nanofluids (NanoCF) using silica nanoparticles based on the impact on the capillary number for being applied in heavy crude oil reservoirs. Six types of silica nanoparticles with different chemical nature were characterized by dynamic light scattering (DLS), point of zero charge (pHpzc), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), surface area (SBET), X-ray diffraction (XRD) and total surface acidity through temperature-programmed desorption of NH3 (TPD-NH3). Adsorption isotherms were constructed for understanding the non-ionic surfactant interaction with nanoparticles and rock surfaces, showing that a high adsorption affinity of the surfactant onto the rock surface, leaving less than 24% of free surfactant molecules able to migrate to the water/oil interface. Nevertheless, nanoparticle addition onto completion fluids (CF) could reduce the adsorbed surfactant onto the rock surface by 75%, which means more molecules of surfactant at the interface due to the nature of the obtained nanoparticles (NPS). The nanoparticles were selected based on the capillary number, showing that the best material reduced the interfacial tension between heavy crude oil and CF more than 76% and have the capacity to modify an initial oil-wet state to a water-wet rock surface. Finally, a coreflooding test was carried out at reservoir conditions (158 °F and 6.89 MPa) for evaluating the best completion nanofluid design based on the static tests, showing an increase of the oil effective permeability of 37% and incremental oil recovery of 3% in comparison to the completion fluid without nanoparticles. For the first time, novel completion nanofluids could allow stimulating the well from the beginning of the productive life.

Synthesis of HTLcs modified by K3PO4 for side chain alkylation of toluene with methanol

A series of calcined HTLcs catalysts were prepared and modified with potassium phosphate by impregnation method to clarify the influence of catalyst alkalinity on the side chain alkylation of toluene with methanol for synthesis of ethylbenzene and styrene. The catalysts were characterized by X-ray diffraction (XRD), N2 physical adsorption–desorption, Fourier-transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), X-ray photoelectron spectrometry (XPS), NH3 temperature-programmed desorption (NH3-TPD) and CO2 temperature-programmed desorption （CO2-TPD）. It was found that the selectivity of styrene was highest (39.25%) when the K3PO4 loading was 7.5 wt%. And the total yield of styrene and ethylbenzene could reach 65.08% with 10 wt% K3PO4 loading. This might due to the fact that the addition of K3PO4 could adjust the acid and basic sites of catalysts. In addition, appropriate strength and amount of basic sites were favorable to producing more styrene.

Catalyst Characteristics and Performance of Silica-Supported Zinc for Hydrodeoxygenation of Phenol

The present investigation aimed to study the physicochemical characteristics of supported catalysts comprising various percentages of zinc dispersed over SiO2. The physiochemical properties of these catalysts were surveyed by N2 physisorption (BET), thermogravimetry analysis (TGA), H2 temperature-programmed reduction, field-emission scanning electron microscopy (FESEM), inductively coupled plasma-optical emission spectrometry (ICP-OES), and NH3 temperature-programmed desorption (NH3-TPD). In addition, to examine the activity and performance of the catalysts for the hydrodeoxygenation (HDO) of the bio-oil oxygenated compounds, the experimental reaction runs, as well as stability and durability tests, were performed using 3% Zn/SiO2 as the catalyst. Characterization of silica-supported zinc catalysts revealed an even dispersion of the active site over the support in the various dopings of the zinc. The acidity of the calcinated catalysts elevated clearly up to 0.481 mmol/g. Moreover, characteristic outcomes indicate that elevating the doping of zinc metal led to interaction and substitution of proton sites on the SiO2 surface that finally resulted in an increase in the desorption temperature peak. The experiments were performed at temperature 500 °C, pressure 1 atm; weight hourly space velocity (WHSV) 0.32 (h−1); feed flow rate 0.5 (mL/min); and hydrogen flow rate 150 (mL/min). Based on the results, it was revealed that among all the prepared catalysts, that with 3% of zinc had the highest conversion efficiency up to 80%. However, the selectivity of the major products, analyzed by gas chromatography flame-ionization detection (GC-FID), was not influenced by the variation in the active site doping.

Synthesis of CoO–NiO promoted sulfated ZrO2 super-acid oleophilic catalyst via co-precipitation impregnation route for biodiesel production

Abstract This study focuses on the synthesis of a novel heterogeneous CoO–NiO promoted sulfated ZrO2 (CN/SZ) catalyst and investigating its catalytic efficiency as a transesterification reagent. Catalytic performance has also been compared with two reference catalysts viz., sulfated ZrO2 (SZ) and pure ZrO2 (Z). Prepared materials were characterized using X-ray diffraction (XRD) technique, N2- adsorption/desorption study, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDAX), Raman, Fourier Transformed Infrared (FTIR), and X-ray photoelectron (XP) spectroscopy techniques. Surface acidity and basicity were assessed by NH3 and CO2 temperature-programmed desorption (TPD) respectively that established high surface acidity and basicity of CN/SZ nanocatalyst. The reagent has shown supreme catalytic performance as only 0.2 wt% catalyst loading amount has provided 98.8% of biodiesel yield with 3:1 MeOH:Oil molar ratio at 65 °C for 2 h. Also, the reusability study has proved the efficacy of CN/SZ nanocatalyst that it can successfully be reused in five consecutive reaction cycles displaying promising results and the reactivated catalyst provided remarkably high biodiesel yield of 96.8%. Further, the mechanistic pathway of the simultaneous catalytic esterification of free fatty acid and transesterification of triglyceride occurring on catalyst surface has also been explored.

AlPO4-free MoP/γ-Al2O3 catalyst for methanation under low H2/CO

The MoP/γ-Al2O3 catalysts were prepared with phytic acid (PA) and phosphate as phosphorus precursors, respectively. Herein, we investigated the effect of the MoP loading amount on the catalytic methanation performance of the catalysts in the condition of low H2/CO ratios (H2/CO = 1:1). The X-ray diffraction (XRD), nuclear magnetic resonance (NMR), N2 adsorption–desorption, Raman spectroscopy (RS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), NH3-temperature programmed desorption (NH3-TPD) were undertaken to get the physical structures and chemical properties of the catalysts. The results showed that the MoP/γ-Al2O3 catalysts prepared by the PA method displayed higher methanation performance. It was because no AlPO4 was formed in the MoP/γ-Al2O3 catalysts prepared by the PA method. The optimum loading amount of the MoP/γ-Al2O3 catalyst was 28 wt%, which shows 80.1% CO conversion in initial. Besides, this work further studied the effect of H2S concentrations on methanation activity of the catalyst, the results showed that the Mo species on catalyst surface by sulfidation with H2S, resulting in the catalytic activity decreased.

Tailored Alkali Resistance of DeNOx Catalysts by Improving Redox Properties and Activating Adsorbed Reactive Species

SummaryIt is still challenging to develop strongly alkali-resistant catalysts for selective catalytic reduction of NOx with NH3. It is generally believed that the maintenance of acidity is the most important factor because of neutral effects of alkali. This work discovers that the redox properties rather than acidity play decisive roles in improving alkali resistance of some specific catalyst systems. K-poisoned Fe-decorated SO42−-modified CeZr oxide (Fe/SO42−/CeZr) catalysts show decreased acidity but reserve the high redox properties. The higher reactivity of NHx species induced by K poisoning compensates for the decreased amount of adsorbed NHx, leading to a desired reaction efficiency between adsorbed NHx and nitrate species. This study provides a unique perspective in designing an alkali-resistant deNOx catalyst via improving redox properties and activating the reactivities of NHx species rather than routinely increasing acidic sites for NHx adsorption, which is of significance for academic interests and practical applications.

Highly dispersed copper cobalt oxide nanoclusters decorated carbon nitride with efficient heterogeneous interfaces for enhanced H2 evolution

Photocatalytic reaction refers to a sophisticated heterogeneous catalyzing process. Exploring the interfacial reaction of catalysts will provide insights into efficient artificial photosynthetic system and promote its design. In this study, highly dispersed bimetallic CuCo2O4 nanoclusters decorated g-C3N4 heterojunction photocatalyst was produced by in-situ deposition of 0D CuCo2O4 spinel on the 2D g-C3N4 surface. Compared with CuO or Co3O4 modified g-C3N4, the optimal composite exhibits a significantly higher H2 evolution rate of 4187.6 μmol∙gcat−1∙h−1 with an apparent quantum yield (AQY) of 4.57% under the irradiation of monochromatic light (400 ± 7.5 nm) in the absence of noble metal. As suggested from the results of the photoelectrochemistry characterizations and NH3-temperature programmed desorption (NH3-TPD) analysis, CuCo2O4/g-C3N4 exhibited faster HER kinetics and considerable surface acidity sites, and it facilitated triethanolamine (TEOA) chemisorption and H2 evolution, further highlighting the merits of such mixed-metal compounds. Moreover, the transfer pathway of charge carriers between CuCo2O4 and g-C3N4 heterogeneous interface was demonstrated by photo-degradation of RhB and selective photo-deposition Pt nanoparticles.

Conversion of succinic acid over Ni and Co catalysts

Liquid-phase hydrogenation of succinic acid (SA) over supported Ni and Co catalysts was investigated at 200 °C and 6 MPa of H2. Reduced and passivated catalysts with the same surface metal density (2.5 atoms of metal per nm2 of support) were prepared by incipient wetness impregnation. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), CO-chemisorption, and temperature-programmed desorption of NH3 (TPD-NH3). The Ni and Co catalysts supported over SiO2 showed different product distribution, due to the adsorption of the SA over the surface of catalysts, determined by DFT calculations. The Co/SiO2, Co/SiO2-Al2O3, and Co/Al2O3 catalysts showed different product distribution, which was correlated with total acidity from TPD-NH3 results. In general, the Co catalysts promoted the hydrogenation process; however, the highest total acidity showed by Co/Al2O3 also promoted the dehydration process. Finally, the initial rate follows the trend according to the dispersion determined by CO-chemisorption.

Combined promoting effect of molybdenum on the bimetallic Al2O3-La2O3 catalysts for NOx reduction by CO

Promotional effect of molybdenum on bimetallic Al2O3-La2O3-based catalysts was investigated in the selective catalytic reduction (CO-SCR) reaction. The physicochemical properties of the solids were evaluated through X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), nitrogen physisorption analyses, Temperature programmed reduction (TPR), NH3-temperature programmed desorption (NH3-TPD) and Transmission electron microscopy (TEM). Structural characterizations confirmed the formation of porous nanostructured solids with molybdenum helping the dispersion of the Ni or Pt active sites close to the molybdenum particles. The catalysts have acid sites of medium to low strengths effectively enhancing the catalytic activity of the solids. Investigation of the various active sites revealed PtMo supported on Al2O3-La2O3 as the best catalyst using distinct temperatures and poisoning conditions in the CO-SCR reaction, rather than NiMo and CoMo counterparts. The oxidation of the species and phase transformation were more significant on the CoMo than NiMo catalyst, with the latter having a modest performance. The low interaction of the PtMo with the support provided the formation of a Pto and Mo6+ redox pair, which resulted in high CO and NOx adsorption to form CO2 and N2. This was due to the synergistic effect of valence-rich Mo transition oxides with Pt species, resulting in the inhibition of irreversible sulfatation and coking over PtMo/Al2O3-La2O3 catalyst.