TPR Experiments Research Articles

Biogas reforming on La-promoted NiMgAl catalysts derived from hydrotalcite-like precursors

Hydrotalcite-like precursors have been synthesized in order to study the influence of lanthanum on the structure and the properties of the precursors, as well as on the catalytic activity and stability of their derived catalyst on biogas reforming. From XRD, and TPO characterization, we confirmed that hydrotalcite-like precursors where obtained. After calcination at 750 °C, Mg(Ni,Al)O solid solution was detected. High surface areas have been obtained finding the highest surface area on the catalyst without lanthanum. TPR experiments were performed in order to study the reducibility of the catalysts. One reduction peak was found in the catalyst without lanthanum while two peaks were observed in the catalysts with lanthanum. A reduction peak at 900 °C was observed over the sample without Ni and La. Catalytic tests, at 700 °C with a feed of CH 4:CO 2 1:1, were performed after appropriate reduction during 50 h. While a decrease on catalytic activity was observed with the addition and the increase of La content, an enhancement in the stability was observed. No sign of deactivation of the catalyst and no carbon deposition were found on the catalysts doped with lanthanum.

Cross metathesis of butene-2 and ethene to propene over Mo/MCM-22-Al 2O 3 catalysts with different Al 2O 3 contents

A series of 3.0Mo/MCM-22-Al 2O 3 catalysts with γ-Al 2O 3 contents in the range of 0-100 wt% were prepared and applied in the metathesis reaction of ethene and butene-2. Addition of γ-Al 2O 3 did not affect the structure of MCM-22 zeolite as evidenced by XRD and N 2 adsorption measurements. It was deduced from TPR experiments that γ-Al 2O 3 phase favored the formation of polymolybdate or multilayered Mo oxide, while more Al 2(MoO 4) 3 species were generated over MCM-22 zeolites. Alumina content in the support was directly related to the metathesis activity of ethene and butene-2 to propene. Mo species with higher valence (Mo 6+ or Mo 5+) contributed more to the excellent performance of catalyst than metallic Mo. The best catalyst activity and stability was obtained over 3.0Mo/(MCM-22-30%Al 2O 3) under the reaction condition of 1.0 MPa and 125 γC using N 2 as the pretreatment gas.

Selective catalytic reduction of NO by CO over CuO supported on SBA-15: Effect of CuO loading on the activity of catalysts

CuO supported on mesoporous silica SBA-15 was investigated as a catalyst for selective catalytic reduction of NO by CO. The CuO/SBA-15 catalysts were prepared by wet impregnation with copper loadings of 4.01–10.1 wt%. The catalysts were characterized by N 2 adsorption, XRD, ICP, H 2-temperature programmed reduction (TPR) and NO-temperature programmed desorption. The most active CuO/SBA-15 catalyst in this study was Cat-B, containing 8.67 wt% Cu on silica. This catalyst achieved 60% NO reduction in catalytic tests. Increasing the Cu loading to 10.1 wt% resulted in a less active catalyst (Cat-C) than for Cu loadings less than 10 wt%. The reduced activity of Cat-C for the NO + CO reaction was attributed to formation of bulk CuO aggregates on the SBA-15 particles and a Cu 2O phase at high Cu loadings, as confirmed by TPR experiments and XRD measurements.

Ethanol steam reforming and water gas shift over Co/ZnO catalytic honeycombs doped with Fe, Ni, Cu, Cr and Na

The effect of Fe, Ni, Cu, Cr, and Na (1%) addition over ZnO-supported Co (10%) honeycomb catalysts in the steam reforming of ethanol (ESR) and water gas shift reaction (WGS) for the production of hydrogen was studied. HRTEM and EEL spectroscopy revealed the formation of metal alloys between Co and Fe, Ni, Cu, and Cr. Catalysts promoted with Fe and Cr performed better in the ESR, and the sample promoted with Fe showed high activity for WGS at low temperature. As deduced from TPR and oxidation pulse experiments, alloy particles in catalysts promoted with Fe and Cr exhibited a rapid and higher degree of redox exchange between reduced and oxidized Co, which may explain the better catalytic performance.

Regeneration of a model NOX storage/reduction catalyst using hydrocarbons as the reductant

Regeneration of a model NOX storage and reduction (NSR) catalyst using hydrocarbons, H2, or CO as reducing agents was investigated. As previously shown, at low temperature, 200°C, H2 proved best, while both CO and hydrocarbons were found to poison Pt sites. At 250°C, again H2 was better but the decreased performance with CO and hydrocarbons was also due to slow kinetics and not solely as a result of Pt site poisoning. At T≥300°C, hydrocarbons were found to regenerate the catalyst as efficiently as CO and H2. Hydrocarbon steam reforming experiments were performed to investigate the improved performance at T≥300°C. Steam reforming did not occur with either dodecane or m-xylene below 450°C. Additionally, although propylene steam reforming occurred at 375°C, the small amount of H2 formed was insufficient for steam reforming to be the sole reason for improved regeneration. TPR experiments show that propylene was activated on the catalyst at T≥217°C and, under the conditions examined, the complete reduction of NO by propylene was achieved at 287°C. Furthermore, propylene was observed to reduce surface chemisorbed NOX species at T>200°C, with high rates by 264°C, with this activity ultimately resulting in the comparable performance with either CO or H2 at similar temperatures during NOX cycling experiments.

Pt,In and Pd,In catalysts for the hydrogenation of nitrates and nitrites in water. FTIR characterization and reaction studies

Pt,In and Pd,In catalysts supported on alumina or silica are active for the reduction of nitrate to N 2 in water, using H 2 as reducing agent. The characterization of the catalysts using FTIR of adsorbed CO shows the formation of both linear and bridged CO–Pd and CO–Pt bonds. Besides, carbonate species are formed due to the presence of OH groups provided by the support. The presence of In produces a shift in CO–Pd and CO–Pt bands, suggesting the formation of intermetallic particles. After use in reaction, the amount of CO–Pd and CO–Pt species strongly decreases, the main signals being those associated with carbonate groups. The proportion between bridged and linear species also changes after reaction. These results indicate the agglomeration of metallic particles during reaction, which is in agreement with TEM results. Increasing the In loading from 0.25 to 0.5 wt.% results in a moderate decrease in the nitrate conversion for all of the catalysts, which could be associated with a decrease of isolated Pd sites which are responsible for the dissociation of hydrogen. The experimental evidence for this point is the decrease of bridged CO adsorbed observed via FTIR for the samples with higher In loading and for all the catalysts. TPR experiments show low-temperature reduction peaks due to the presence of oxychloride and hydroxychloride particles in monometallic Pd and Pt catalysts. When In is present, the formation of Pd–In and Pt–In compounds provoke the shift of the reduction peaks and the appearance of new reduction signals.

Effect of Pt/Pd ratio on catalytic activity and redox behavior of bimetallic Pt–Pd/Al2O3 catalysts for CH4 combustion

In the present work CH4 combustion activity and reduction/oxidation behavior of bimetallic Pt–Pd/Al2O3 catalysts with constant Pd loading (2%, w/w) and different Pt/Pd atomic ratios (0, 0.10, 0.25 and 1) are investigated in the presence of alternated CH4 lean combustion/CH4-reducing pulses at 350°C. In the fresh samples, according to XRD and CH4-TPR measurements, Pd is always totally present as PdO and the CH4 combustion activity is progressively promoted by Pt addition. On the other hand the reactivity scale is substantially changed (Pt/Pd=0.10≥Pt/Pd=0>Pt/Pd=0.25≫Pt/Pd=1) after a conditioning treatment consisting of several reduction/oxidation cycles in CH4-containing atmosphere, which has a progressively positive effect on decreasing the Pt content. Indeed, such a treatment results in a 20-fold catalytic activity enhancement for the monometallic sample (Pt/Pd=0), whereas it has different effects on the bimetallic catalysts depending on the Pt/Pd ratio: for Pt/Pd=0.10 the activity markedly increases up to the highest level among the tested catalysts (fresh and conditioned); for Pt/Pd=0.25 the activity is substantially unchanged while for the Pt/Pd=1 it is completely suppressed after the first CH4-reducing pulse.Such different behavior is mainly related to the influence of Pt on bulk reduction/re-oxidation properties of palladium; TPO data indicate a strong inhibition of Pt on Pd oxidation, which is completely suppressed for the Pt/Pd-1 catalyst, thus explaining the wide loss of activity after reduction for Pt/Pd-1 and confirming that PdO is the most active phase. In the case of the samples with Pt/Pd=0.25 and Pt/Pd=0.10 the inhibiting effect of Pt on Pd oxidation is progressively reduced, resulting in a fraction of PdO formed at the end of the conditioning process equal to 35% and 85% of total Pd, respectively.In line with a Mars van Krevelen redox mechanism controlled by PdO surface reduction by CH4, for the monometallic sample the activity enhancement upon conditioning is associated with an increase of bulk PdO reducibility, as determined by CH4-TPR experiments. Such a correlation is not observed in bimetallic samples possibly due to the ability of metallic Pt to activate CH4 under net reducing conditions (CH4-TPR), which is suppressed under net oxidizing conditions (lean combustion).

Effect of ceria on the desulfation characteristics of model lean NO x trap catalysts

Using model powder catalysts and fully formulated monolithic lean NO x trap (LNT) catalysts, the effect of ceria on LNT desulfation behavior was investigated. TPR experiments performed on the model catalysts showed that each of the oxide phases present (BaO, CeO 2, and Al 2O 3) is able to store sulfur and that they possess distinct behavior in terms of the temperatures at which desulfation occurs. For a Pt/BaO/Al 2O 3 catalyst, addition of ceria was found to reduce the degree of sulfur accumulation on the BaO phase, particularly at high sulfur loadings, by contributing to sulfur capture. The importance of maintaining the Pt and Ba phases in close proximity for efficient LNT desulfation was also demonstrated; physically separating the Pt and Ba sites resulted in a shift of the desulfation temperature of the surface BaSO 4 by 20–40 °C towards higher temperature, i.e., towards the position characteristic of bulk BaSO 4. From the monolith studies, it was found that relative to a sample containing no ceria, samples containing La-stabilized CeO 2 or CeO 2–ZrO 2 showed a greater resistance to deactivation during sulfation (as reflected by the NO x storage efficiency), and required lower temperatures to restore the NO x storage efficiency to its pre-sulfation value. In addition to the ability of ceria to store sulfur and release it at relatively low temperatures under reducing conditions, these findings can be attributed to the high water–gas shift activity displayed Pt/CeO 2, which result in increased intra-catalyst concentrations of H 2 under rich conditions. The results also showed that precious metal loadings can significantly impact desulfation efficiency and that both high Rh and Pt loadings are beneficial for catalyst desulfation.

Autothermal reforming of methane over Rh/Ce 0.5Zr 0.5O 2 catalyst: Effects of the crystal structure of the supports

Autothermal reforming of methane (ATR) was studied over Rh catalysts supported on Ce 0.5Zr 0.5O 2 solid solution, which were synthesized by four different routes, including reverse micro-emulsion (ME), co-precipitation (CP), urea-combustion (UC) and sol–gel (SG) method. The textural and structural properties of the as-prepared solid solutions were carefully examined by means of BET, TEM, XRD and Raman techniques. Results showed that the ME sample exhibited a single cubic phase, whereas tetragonal or mixed phases such as cubic CeO 2-rich and tetragonal ZrO 2-rich phases, were found in the case of CP, UC and SG. Vegard's rule revealed that the homogeneity of these as-prepared solid solutions followed the order of ME > CP > UC > SG. TPR and CO-pulse experiments were adopted to evaluate the reducibility and the oxygen storage capacity (OSC) of the catalysts. It was found that the more homogenous the solid solution is, the more reducibility it is, i.e. both the reducibility and OSC followed the same order as that of homogeneity. Rh/ME showed the highest activity and H 2/CO ratio and such performance was maintained without significant loss during 10 h experiment. On the contrary, the other three catalysts having mixed phases showed remarkably deactivation in terms of H 2/CO due to the loss of BET area. To elucidate the resistance toward carbon formation of these catalysts, methane decomposition experiments and following temperature-programmed-oxidation (TPO) were studied. As expected, the resistance toward carbon formation could be enhanced by the improved OSC of the catalyst.

NOx storage and reduction properties of Pt/CexZr1−xO2 mixed oxides: Sulfur resistance and regeneration, and ammonia formation

The influence of the ceria-zirconia mixed oxide composition in Pt/CexZr1−xO2 catalysts was studied toward NOx storage capacity (NSC), including sulfur poisoning and sulfur regeneration, and NOx reduction efficiency in lean–rich cycling conditions. The results are compared with a Pt/Ba/Al model catalyst. The samples were characterized by N2 adsorption, XRD and H2-TPR. The behaviors of the ceria-zirconia supported catalysts are quite similar whatever their composition. They are sensitive to a reducing pretreatment which leads to an increase of (i) the cerium reducibility/oxygen mobility, (ii) the NO oxidation rate and (iii) the NOx storage capacity at 300 and 400°C. The sulfating treatment leads to a dramatic decrease of the NOx storage capacity for all catalysts, the decrease being more pronounced for the Zr-rich samples. H2-TPR experiments show that the sulfates amount and their stability tend to increase with the Zr content, but these sulfates are significantly less stable compared with Pt/Ba/Al. The sulfur elimination rates in rich mixture at 550°C are higher than 90% with the ceria-zirconia supported catalysts versus 56% with Pt/Ba/Al.The ceria-zirconia supported catalysts are able to convert NOx in lean–rich cycling condition. Compared with Pt/Ba/Al, the NOx conversions are a little lowered but the ammonia selectivity is significantly decreased with the Ce–Zr mixed oxides, with a beneficial influence of the cerium content.

Manganese oxide hollow structures with different phases: Synthesis, characterization and catalytic application

Abstract Manganese oxide hollow structures with different phases were synthesized by calcination using a γ-MnO2 hollow structure as a precursor. Our results revealed that the as-synthesized β-MnO2 and Mn2O3 still maintained the morphology of the precursor. Compared with the MnO2 reported and conventional MnO2, both the γ-MnO2 and β-MnO2 hollow structures showed a higher catalytic activity and an excellent selectivity in the aerobic oxidation of cinnamyl alcohol to cinnamyl aldehyde. The TPR experiments demonstrated that the reduced size of crystallite, hollow nature and higher BET specific surface area were responsible for their higher catalytic activity.

Computational thermal and kinetic analysis

Advanced software (TKS-SP2.0 version) for thermal and kinetic analysis, for determining the non-isothermal kinetic parameters of heterogeneous processes has been developed. The dynamic handle of conversion degree steps and ranges, heating rates and kinetic models, makes the evaluation of the kinetic parameters much faster, for TG, TPR and dilatometry experiments. The standard procedure for evaluating the kinetic triplet was implemented; several linear isoconversional methods (from generalized KAS to FWO, Li-Tang and Friedmann methods), IKP method, Perez-Maqueda et al. criterion (both by Differential equation) and Master plots method. The software is designed mainly for data processing of experimental files, but may also import other already transformed numeric data.

Towards practical application of lanthanum ferrite catalysts for NO reduction with H 2

A series of perovskite-type catalysts (LaFeO 3, La 0.8Sr 0.2FeO 3, Pd/La 0.8Sr 0.2FeO 3, La 0.8Sr 0.2Fe 0.9Pd 0.1O 3, La 0.7Sr 0.2Ce 0.1FeO 3, Pd/La 0.7Sr 0.2Ce 0.1FeO 3 and La 0.7Sr 0.2Ce 0.1Fe 0.9Pd 0.1O 3) has been prepared by the solution combustion synthesis method and fully characterized by XRD, BET, FESEM and TPD/R analyses. The performance of these catalysts towards the NO reduction mechanism by H 2 has been evaluated in a temperature-programmed reaction apparatus (TPRe) in the absence and in the presence of oxygen. The catalysts have been studied in the 25–350 °C temperature range, and significant catalytic activities were measured at 150–250 °C. Among the catalysts screened, La 0.8Sr 0.2Fe 0.9Pd 0.1O 3, showed the best performance. Hence, it was deposited directly over a ceramic honeycomb monolith by in situ SCS, tested in a lab-scale test rig, then submitted to the specific ageing protocol (thermal treatment at 500 °C for 96 h) in the presence of water vapour and sulfur dioxide, two potentially deactivating species present in diesel exhaust gases, and it showed a good compromise between satisfactory catalytic activity and stability. A mechanistic analysis is presented concerning the relationship between the observed activity and the reducibility of the B site, determined through TPR experiments. Some final conclusions are drawn on the perspective of the practical application of the investigated aftertreatment route for diesel exhaust gases.

NO SCR reduction by hydrogen generated in line on perovskite-type catalysts for automotive diesel exhaust gas treatment

This paper deals with the preparation (by solution combustion synthesis, SCS), characterization (by XRD, BET, FESEM and TPD/R analyses), catalytic activity evaluation (in a temperature-programmed reaction—TPRe apparatus), and the assessment of the reaction mechanism of NO reduction by H 2 in the presence of oxygen on a series of perovskite-type catalysts belonging to the LaFeO 3 family (LaFeO 3, La 0.8Sr 0.2FeO 3, Pd/La 0.8Sr 0.2FeO 3, La 0.8Sr 0.2Fe 0.9Pd 0.1O 3, La 0.7Sr 0.2Ce 0.1FeO 3, Pd/La 0.7Sr 0.2Ce 0.1FeO 3, La 0.7Sr 0.2Ce 0.1Fe 0.9Pd 0.1O 3). The catalysts have been studied in the 25–350 °C temperature range. Significant catalytic activities were measured at 150–250 °C. Among the catalysts screened, La 0.8Sr 0.2Fe 0.9Pd 0.1O 3, showed the best performance. Hence, it was deposited directly over a ceramic honeycomb monolith by in situ SCS and then tested in a lab-scale test rig. A mechanistic analysis is presented concerning the relationship between the observed activity and the reducibility of the B site, determined from TPR experiments, as well as the correlation between the observed oxygen inhibition and the proposed NO x reduction mechanism. Some final conclusions are drawn on the perspective of the practical application of the investigated after-treatment route for diesel exhaust gases.

Wet oxidation of phenol over transition metal oxide catalysts supported on Ce 0.65Zr 0.35O 2 prepared by continuous hydrothermal synthesis in supercritical water

The mixed oxide (Ce 0.65Zr 0.35O 2) prepared by supercritical synthesis was applied as a support of transition metal (Mn, Fe, Co, Ni, and Cu) oxide catalysts for catalytic wet oxidation (CWO) of phenol in view of their higher thermal stability, better oxygen storage capacity, and higher surface area. The prepared catalysts showed an enhanced catalytic activity for CWO of phenol due to the excellent redox properties of ceria-zirconia mixed oxide. Among the prepared catalysts, the CuO x /Ce 0.65Zr 0.35O 2 was the most effective catalyst in view of catalytic activity and CO 2 selectivity. The leached copper ions seem to contribute to the higher conversion of phenol over the CuO x /Ce 0.65Zr 0.35O 2 via homogeneous catalysis. The characterization with XPS, XANES, and TPR experiments confirmed that the active copper species in the CuO x /Ce 0.65Zr 0.35O 2 is highly dispersed Cu 2+ clusters. Although the MnO x /Ce 0.65Zr 0.35O 2 showed a high conversion of phenol and TOC, the converted phenol was mainly changed to carbon deposits on the surface of catalyst resulting in catalyst deactivation.

La0.8Sr0.2Ni0.4Fe0.6O3–Ce0.8Gd0.2O2–δ Nanocomposite as Mixed Ionic–Electronic Conducting Material for SOFC Cathode and Oxygen Permeable Membranes: Synthesis and Properties

Mixed ionic–electronic conducting nanocomposite La0.8Sr0.2Ni0.4Fe0.6O3 (LSNF)–Ce0.8Gd0.2O2– δ (GDC) was prepared via ultrasonic dispersion of nanocrystalline powders of perovskite and fluorite oxides in water with addition of surfactant, followed by drying and sintering up to 1300°C. Analysis of the real structure of nanocomposite (studied by XRD and TEM with EDX) and its surface composition (studied by XPS) revealed moderate redistribution of elements between phases favoring their epitaxy. Results of impedance spectroscopy, oxygen isotope exchange, O2 TPD and H2 TPR experiments revealed a positive effect of composite interfaces on the oxygen mobility and reactivity agreeing with the ambipolar transport behavior of MIEC composite. Preliminary testing of button-size cell with functionally graded LSNF–GDC cathode layer supported on thin YSZ layer covering Ni/YSZ cermet demonstrated high and stable performance, which is promising for its practical application.

Process investigation, electrochemical characterization and optimization of LiFePO 4/C composite from mechanical activation using sucrose as carbon source

LiFePO 4/C composite was synthesized by mechanical activation using sucrose as carbon source. High-energy ball milling facilitated phase formation during thermal treatment. TG–DSC and TPR experiments demonstrated sucrose was converted to CH x intermediate before completely decomposed to carbon. Ball milling time, calcination temperature and dwelling time all had significant impact on the discharge capacity and rate performance of the resulted power. The optimal process parameters are high-energy ball milling for 2–4 h followed by thermal treatment at 700 °C for 20 h. The product showed a capacity of 174 mAh/g at 0.1C rate and around 117 mAh/g at 20C rate with the capacity fade less than 10% after 50 cycles. Too low calcination temperature or insufficient calcination time, however, could result in the residual of CH x in the electrode and led to a decrease of electrode performance.

Co oxidation with oxygen in the presence of hydrogen on CoO/CeO2 and CuO/CoO/CeO2 catalysts

The catalytic activity of the CoO/CeO2 and CuO/CoO/CeO2 systems in selective CO oxidation in the presence of hydrogen at 20–450°C ([CuO] = 1.0–2.5%, [CoO] = 1.0–7.0%) is reported. The maximum CO conversion (X) decreases in the following order: CuO/CoO/CeO2 (X = 98–99%, T = 140–170°C) > CoO/CeO2 (X = 67–84%, T = 230–240°C) > CeO2 (X = 34%, T = 350°C). TPD, TPR, and EPR experiments have demonstrated that the high activity of CuO/CoO/CeO2 is due to the strong interaction of the supported copper and cobalt oxides with cerium dioxide, which yields Cu-Co-Ce-O clusters on the surface. The carbonyl group in the complexes Coδ+-CO and Cu+-CO is oxidized by oxygen of the Cu-Co-Ce-O clusters at 140–160°C and by oxygen of the Co-Ce-O clusters at 240°C. The decrease in the activity of the catalysts at high temperatures is due to the fact that hydrogen reduces the clusters on which CO oxidation takes place, yielding Co0 and Cu0 particles, which are inactive in CO oxidation. The hydrogenation of CO into methane at high temperatures is due to the appearance of Co0 particles in the catalysts.

Chromium oxide supported on MCM-41 as a highly active and selective catalyst for dehydrogenation of propane with CO2

Abstract Incipient wetness technique was used for a preparation of MCM-supported chromium oxide materials with a Cr loading ranging from 0.7 to 13.7 wt%. The obtained samples were characterized by XRD, UV–vis-DRS, H 2 -TPR and BET, and tested as catalysts in dehydrogenation of propane with CO 2 . The catalytic reaction was studied in a flow apparatus at 773–923 K. All the tested catalysts exhibited a good catalytic performance in the dehydrogenation of propane with CO 2 . The best results were achieved over the sample containing 6.8 wt% of Cr. In this case, the selectivity to propene was above 80%, while the conversion of propane increased from 21% (at 773 K) to 62% (at 923 K). The promoting effect of CO 2 on the yield of propene was found for all the studied catalysts. This effect was discussed on the basis of temperature-programmed reaction of CO 2 with H 2 as well as H 2 -TPR experiments after regeneration of the reduced catalyst with pure CO 2 . It was suggested that one of reasons of a higher yield of propene observed in the presence of CO 2 compared to that measured in the absence of CO 2 was coupling of the dehydrogenation of propane with the reverse water–gas shift reaction.

Total oxidation of propene at low temperature over Co3O4–CeO2 mixed oxides: Role of surface oxygen vacancies and bulk oxygen mobility in the catalytic activity

Abstract Co 3 O 4 , CeO 2 and Co 3 O 4 –CeO 2 mixed oxides with Co/Ce nominal atomic ratio 0.1:5, prepared by co-precipitation method with sodium carbonate, were tested in the oxidation of propene under lean condition and the catalyst stability was checked by performing three consecutive heating–cooling cycles. Characterization of the textural properties were performed by surface area measurement BET, X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Among the Co 3 O 4 –CeO 2 mixed oxides, Co 3 O 4 (30 wt%)–CeO 2 (70 wt%) gives the best activity attaining full propene conversion at 250 °C. This sample is characterized by the presence of Co 3 O 4 particles well dispersed and in good contact with ceria according to BET and XRD data and as evidenced by SEM micrographs. Oxygen temperature-programmed desorption (O 2 -TPD) and C 3 H 6 -temperature-programmed reduction (C 3 H 6 -TPR) experiments were carried out in order to study the surface and bulk oxygen mobility and to correlate it to the activity. At temperature around 200 °C, O 2 -TPD experiments showed the desorption of mobile surface oxygen species for the most active samples, Co 3 O 4 and Co 3 O 4 (30 wt%)–CeO 2 (70 wt%). C 3 H 6 -TPR experiments for both of the oxides also evidenced a high reactivity at low temperature, especially, for Co 3 O 4 (30 wt%)–CeO 2 (70 wt%) giving at 345 °C an intense peak of CO 2 formation. Conversely, the ceria sample showed by C 3 H 6 -TPR much less pronounced oxygen bulk mobility, starting to react with propene above 500 °C and forming only CO. In this case, the catalytic activity of ceria was explained in terms of formation of surface oxygen vacancies which are relevant to the propene oxidation in presence of gaseous oxygen.