Catalytic combustion of toluene on platinum-containing monolithic carbon aerogels

Monolithic organic aerogels were prepared by the sol–gel procedure from the polymerisation reaction of resorcinol and formaldehyde in water. The organic aerogels were heat treated in inert atmosphere at either 500 or 1000 °C to obtain the carbon aerogels. The catalysts were prepared by impregnation with an aqueous solution of [Pt(NH₃)₄]Cl₂ or by dissolving this salt in the initial aerogel mixture. Supported catalysts were pretreated in He at 400 °C or H₂ at 300 °C before their characterization by H₂ chemisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy or before testing their catalytic activity. Catalyst activities in toluene combustion were evaluated by conversion versus temperature (light-off curves) and conversion versus time catalytic tests. In the case of catalysts prepared by impregnation, the light-off curves for the total combustion of toluene were shifted to lower temperatures with increasing Pt particle size. This suggests that the reaction was sensitive to the Pt structure within the dispersion range of these catalysts. However, the reverse occurred with catalysts prepared by mixing the precursor in the initial aerogel mixture. Results found could be due to the different surface Pt content of these catalysts as revealed by X-ray photoelectron spectroscopy. This difference was related to the growth of large three-dimensional Pt particles on the surface of the less dispersed catalyst. This means that there is a critical Pt particle size above which the toluene combustion activity decreases with increasing Pt particle size, due to the reduction in active surface sites available for the combustion reaction. Other effect that might influence the activity of these last catalysts is the encapsulation of some Pt particles by the carbon matrix.     

Comparison of the activity of Ru and Pt catalysts for the oxidation of carbon by NO2

The role of two catalysts Pt/Al₂O₃ and Ru/NaY on the oxidation of carbon by NO₂ was investigated in the temperature range 300–400 °C. In the case of Pt/Al₂O₃ no significant catalytic effect on the carbon oxidation rate is observed although decomposition of NO₂ takes place on the noble metal and leads to the formation of NO. This result suggests that the amount of the oxygen atoms transferred from the metallic surface sites to the carbon surface to form C(O) complex is negligible. In contrast, in presence of Ru/NaY the oxidation rate of carbon by NO₂ is markedly increased. Hence, a significant part of the formed O through catalytic decomposition of NO₂ on Ru surface sites is transferred to the carbon surface leading to a larger amount of C(O) complexes on the carbon surface. Thus, the ruthenium surface is a generator of active oxygen species that are spilled over on the carbon surface at 350 °C.     

VOC deep oxidation over Pt catalysts using hydrophobic supports

The active hydrophobic-supported Pt catalysts were synthesized for VOC deep oxidation at low temperature (less than 200°C). The destruction of VOC could cost less at lower temperature due to less energy consumption. The advantage using hydrophobic support was that moistures from atmosphere and oxidation would not be adsorbed on the surface. Thus the active sites would not be cloaked and catalyst activity could be maintained, especially at low temperature. The hydrophobicity of supports was characterized by wetting angles. Porous SDB (styrene divinylbenzene copolymer) was found near 113°, indicating high hydrophobicity. Three Pt catalysts were prepared on SDB and activated carbons by incipient wetness method. Specific surface areas were measured by nitrogen adsorption. The thermal stability of SDB catalyst was examined by TGA, and found no degradation below 200°C in air. The surface compositions of catalysts were analyzed by EDS. XRD showed that Pt was well dispersed on supports after hydrogen reduction at 160°C. The chemical states of Pt were investigated by XPS, and suggested that the oxidized Pt^IV might be the active sites in the reaction. The deep oxidation of toluene/air mixture was carried out to test the activity of catalysts. Pt/SDB showed the highest activity among the catalysts and could completely oxidize 90 ppm toluene/air at VHSV=21 000 h⁻¹, 150°C. Redox mechanism was proposed to reveal the enhanced kinetic rates. The results suggested that the rate of toluene oxidation might be enhanced due to the fact that water, one of the products, was expelled from the hydrophobic surface.     

Catalytic activation of ceramic filter elements for combined particle separation, NOx removal and VOC total oxidation

The development of a catalytically active filter element for combined particle separation and NO_x removal or VOC total oxidation, respectively, is presented. For NO_x removal by selective catalytic reduction (SCR) a catalytic coating based on a TiO₂–V₂O₅–WO₃ catalyst system was developed on a ceramic filter element. Different TiO₂ sols of tailor-made mean particle size between 40 and 190 nm were prepared by the sol–gel process and used for the impregnation of filter element cylinders by the incipient wetness technique. The obtained TiO₂-impregnated sintered filter element cylinders exhibit BET surface areas in the range between 0.5 and 1.3 m²/g. Selected TiO₂-impregnated filter element cylinders of high BET surface area were catalytically activated by impregnation with a V₂O₅ and WO₃ precursor solution. The obtained catalytic filter element cylinders show high SCR activity leading to 96% NO conversion at 300 °C, a filtration velocity of 2 cm/s and an NO inlet concentration of 500 vol.-ppm. The corresponding differential pressures fulfill the requirements for typical hot gas filtration applications. For VOC total oxidation, a TiO₂-impregnated filter element support was catalytically activated with a Pt/V₂O₅ system. Complete oxidation of propene with 100% selectivity to CO₂ was achieved at 300 °C, a filtration velocity of 2 cm/s and a propene inlet concentration of 300 vol.-ppm.     

Methanol partial oxidation on carbon-supported Pt and Pd catalysts

Different Pt and Pd catalysts supported on an activated carbon were prepared by using different metal precursors. Prepared catalysts were pretreated at 400 °C under different atmospheres to decompose the precursor compound and reduce the metal. After pretreatments, the supported catalysts were characterized by H₂ chemisorption, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy to know their metal dispersion, particle size, distribution and oxidation state. Afterwards, the catalysts were tested in methanol partial oxidation with two different O₂/CH₃OH molar ratios. Results obtained in this reaction were compared with those obtained for methanol decomposition in inert atmosphere. For Pt catalysts, there was an increase in methanol conversion and hydrogen production and a decrease in carbon monoxide production under oxidizing conditions. Both methanol conversion and partial oxidation reactions appear to be sensitive to Pt particle structure in the particle size range studied. Results obtained under oxidizing conditions differed between Pd and Pt catalysts. Finally, catalytic activity in methanol partial oxidation was more affected by Pt than Pd particle size in the size range studied.     

Oxidation of H2S on activated carbon KAU and influence of the surface state

Properties of the oxidized activated carbon KAU treated at different temperatures in inert atmosphere were studied by means of DTA, Boehm titration, XPS and AFM methods and their catalytic activity in H₂S oxidation by air was determined. XPS analysis has shown the existence of three types of oxygen species on carbon catalysts surface. The content of oxygen containing groups determined by Boehm titration is correlated with their amount obtained by XPS. Catalytic activity of the KAU catalysts in selective oxidation of hydrogen sulfide is connected with chemisorbed charged oxygen species (O_3.1 oxygen type with BE 536.8–537.7 eV) present on the carbons surface.

Formation of dense sulfur layer (islands of sulfur) on the carbons surface and removal of active oxygen species are the reason of the catalysts deactivation in H₂S selective oxidation. The treatment of deactivated catalyst in inert atmosphere at 300 °C gives full regeneration of the catalyst activity at low temperature reaction but only its partial reducing at high reaction temperature. The last case is connected with transformation of chemisorbed charged oxygen species into CO groups.

The KAU samples treated in flow of inert gas at 900–1000 °C were very active in H₂S oxidation to elemental sulfur transforming up to 51–57 mmol H₂S/g catalyst at 180 °C with formation of 1.7–1.9 g S_x/g catalyst.     

A comparative study of TiO2 supported noble metal catalysts for the oxidation of formaldehyde at room temperature

The TiO₂ supported noble metal (Au, Rh, Pd and Pt) catalysts were prepared by impregnation method and characterized by means of X-ray diffraction (XRD) and BET. These catalysts were tested for the catalytic oxidation of formaldehyde (HCHO). It was found that the order of activity was Pt/TiO₂  Rh/TiO₂ > Pd/TiO₂ > Au/TiO₂  TiO₂. HCHO could be completely oxidized into CO₂ and H₂O over Pt/TiO₂ in a gas hourly space velocity (GHSV) of 50,000 h⁻¹ even at room temperature. In contrast, the other catalysts were much less effective for HCHO oxidation at the same reaction conditions. HCHO conversion to CO₂ was only 20% over the Rh/TiO₂ at 20 °C. The Pd/TiO₂ and Au/TiO₂ showed no activities for HCHO oxidation at 20 °C. The different activities of the noble metals for HCHO oxidation were studied with respect to the behavior of adsorbed species on the catalysts surface at room temperature using in situ DRIFTS. The results show that the activities of the TiO₂ supported Pt, Rh, Pd and Au catalysts for HCHO oxidation are closely related to their capacities for the formation of formate species and the formate decomposition into CO species. Based on in situ DRIFTS studies, a simplified reaction scheme of HCHO oxidation was also proposed.     

Catalytic combustion of methane over bimetallic Pd–Pt catalysts: The influence of support materials

The effect of support material on the catalytic performance for methane combustion has been studied for bimetallic palladium–platinum catalysts and compared with a monometallic palladium catalyst on alumina. The catalytic activities of the various catalysts were measured in a tubular reactor, in which both the activity and stability of methane conversion were monitored. In addition, all catalysts were analysed by temperature-programmed oxidation and in situ XRD operating at high temperatures in order to study the oxidation/reduction properties.

The activity of the monometallic palladium catalyst decreases under steady-state conditions, even at a temperature as low as 470 °C. In situ XRD results showed that no decomposition of bulk PdO into metallic palladium occurred at temperatures below 800 °C. Hence, the reason for the drop in activity is probably not connected to the bulk PdO decomposition.

All Pd–Pt catalysts, independently of the support, have considerably more stable methane conversion than the monometallic palladium catalyst. However, dissimilarities in activity and ability to reoxidise PdO were observed for the various support materials. Pd–Pt supported on Al₂O₃ was the most active catalyst in the low-temperature region, Pd–Pt supported on ceria-stabilised ZrO₂ was the most active between 620 and 800 °C, whereas Pd–Pt supported on LaMnAl₁₁O₁₉ was superior for temperatures above 800 °C. The ability to reoxidise metallic Pd into PdO was observed to vary between the supports. The alumina sample showed a very slow reoxidation, whereas ceria-stabilised ZrO₂ was clearly faster.     

Comparative study of Pt-based catalysts on different supports in the low-temperature de-NOx-SCR with propene

Pt-based catalysts have been prepared using supports of different nature (γ-Al₂O₃, ZSM-5, USY, and activated carbon (ROXN)) for the C₃H₆-SCR of NO_x in the presence of excess oxygen. Nitrogen adsorption at 77 K, pH measurements, temperature-programmed desorption of propene, and H₂ chemisorption were used for the characterization of the different supports and catalysts. The performance of these catalysts has been compared in terms of de-NO_x activity, hydrocarbon adsorption and combustion at low temperature, and selectivity to N₂. Maximum NO_x conversions for all the catalysts were achieved in the temperature range of 200–250°C. The order of activity was, Pt-USY>Pt/ROXNPt-ZSM-5Pt/Al₂O₃. At temperatures above 300°C only Pt/ROXN maintains a high activity caused by the consumption of the support, while the other catalysts present a strong deactivation. Propene combustion starts at the same temperature for all the catalytic systems (160°C). Complete hydrocarbon combustion is directly related to the acidity of the support, thus determining the temperature of the maximum NO_x reduction. The support play an important role in the reaction mechanism through the hydrocarbon activation. N₂O formation was observed for all the catalysts. N₂ selectivity ranges from 15 to 30% with the order, Pt/ROXN>Pt-USYPt/Al₂O₃>Pt-ZSM-5. The catalytic systems exhibit a stable operation under isothermal conditions during time-on-stream experiments.     

Monodispersed gold nanoparticles supported on γ-Al2O3 for enhancement of low-temperature catalytic oxidation of CO

Monodispersed nano-Au/γ-Al₂O₃ catalysts for low-temperature oxidation of CO have been prepared via a modified colloidal deposition route, which involves the deposition of dodecanethiolate self-assembled monolayer (SAM)-protected gold nanoparticles (C₁₂ nano-Au) in hexane on γ-Al₂O₃ at room temperature. The diameter of the gold nanoparticles deposited on the support is 2.5 ± 0.8 nm after thermal treatment, and their valence states comprise both the metallic and oxidized states. It is found that the thermal treatment temperature affects significantly the catalytic activity of the catalysts in the processing steps. The catalyst treated at 190 °C exhibits considerably higher activity as compared to catalysts treated at 165 and 250 °C. A 2.0-wt.% nano-Au/γ-Al₂O₃ catalyst treated at 190 °C for 15 h maintains the catalytic activity at nearly 100% CO oxidation for at least 800 h at 15 °C, at least 600 h at 0 °C, and even longer than 450 h at −5 °C. Evidently, the catalysts obtained using this preparation route show high catalytic activity, particularly at low temperatures, and a good long-term stability.     

MnOx/Pt/Al2O3 catalysts for CO oxidation in H2-rich streams

The catalytic activity of Pt on alumina catalysts, with and without MnO_x incorporated to the catalyst formulation, for CO oxidation in H₂-free as well as in H₂-rich stream (PROX) has been studied in the temperature range of 25–250 °C. The effect of catalyst preparation (by successive impregnation or by co-impregnation of Mn and Pt) and Mn content in the catalyst performance has been studied. A low Mn content (2 wt.%) has been found not to improve the catalyst activity compared to the base catalyst. However, catalysts prepared by successive impregnation with 8 and 15 wt.% Mn have shown a lower operation temperature for maximum CO conversion than the base catalyst with an enhanced catalyst activity at low temperatures with respect to Pt/Al₂O₃. A maximum CO conversion of 89.8%, with selectivity of 44.9% and CO yield of 40.3% could be reached over a catalyst with 15 wt.% Mn operating at 139 °C and λ = 2. The effect of the presence of 5 vol.% CO₂ and 5 vol.% H₂O in the feedstream on catalysts performance has also been studied and discussed. The presence of CO₂ in the feedstream enhances the catalytic performance of all the studied catalysts at high temperature, whereas the presence of steam inhibits catalysts with higher MnO_x content.     

Activity and product distribution of alumina supported platinum and palladium catalysts in the gas-phase oxidative decomposition of chlorinated hydrocarbons

The complete catalytic oxidation of 1,2-dichloroethane (DCE) and trichloroethylene (TCE) over alumina supported noble metal catalysts (Pt and Pd) was evaluated. Experiments were performed at conditions of lean hydrocarbon concentration (around 1000 ppm) in air, between 250°C and 550°C in a conventional fixed bed reactor. The catalysts were prepared in a range of metal contents from 0.1 to 1 wt%. Palladium catalysts resulted to be more active than platinum catalysts in the oxidation of both chlorinated volatile organic compounds. DCE was completely destructed at 375°C, whereas TCE required 550°C. HCl was the only chlorine-containing product in the oxidation of DCE in the range of 250–400°C. Tetrachloroethylene was observed as an intermediate in the oxidation of TCE, being formed to a significant extent between 400°C and 525°C. CO was also detected in the oxidation of both DCE and TCE over Pd catalysts, though at temperatures of complete destruction, CO₂ was the only carbon-containing product. The Pt catalysts were selective to CO₂ at the studied conditions.     

Catalytic combustion over platinum group catalysts: fuel-lean versus fuel-rich operation

Performance data are presented for methane oxidation on alumina-supported Pd, Pt, and Rh catalysts under both fuel-rich and fuel-lean conditions. Catalyst activity was measured in a micro-scale isothermal reactor at temperatures between 300 and 800 °C. Non-isothermal (near adiabatic) temperature and reaction data were obtained in a full-length (non-differential) sub-scale reactor operating at high pressure (0.9 MPa) and constant inlet temperature, simulating actual reactor operation in catalytic combustion applications.

Under fuel-lean conditions, Pd catalyst was the most active, although deactivation occurred above 650 °C, with reactivation upon cooling. Rh catalyst also deactivated above 750 °C, but did not reactivate. Pt catalyst was active above 600 °C. Fuel-lean reaction products were CO₂ and H₂O for all three catalysts.

The same catalysts tested under fuel-rich conditions demonstrated much higher activity. In addition, a ‘lightoff’ temperature was found (between 450 and 600 °C), where a stepwise increase in reaction rate was observed. Following ‘lightoff’ partial oxidation products (CO, H₂) appeared in the mixture, and their concentration increased with increasing temperature. All three catalysts exhibited this behavior.

High-pressure (0.9 MPa) sub-scale reactor and combustor data are shown, demonstrating the benefits of fuel-rich operation over the catalyst for ultra-low emissions combustion.     

Potential rare-earth modified CeO2 catalysts for soot oxidation: Part III. Effect of dopant loading and calcination temperature on catalytic activity with O2 and NO + O2

CeO₂ and CeReO_x_y catalysts are prepared by the calcination at different temperatures (y = 500–1000 °C) and having a different composition (Re = La³⁺ or Pr^3+/4+_, 0–90 wt.%). The catalysts are characterised by XRD, H₂-TPR, Raman, and BET surface area. The soot oxidation is studied with O₂ and NO + O₂ in the tight and loose contact conditions, respectively. CeO₂ sinters between 800–900 °C due to a grain growth, leading to an increased crystallite size and a decreased BET surface area. La³⁺ or Pr^3+/4+ hinders the grain growth of CeO₂ and, thereby, improving the surface catalytic properties. Using O₂ as an oxidant, an improved soot oxidation is observed over CeLaO_x_y and CePrO_x_y in the whole dopant weight loading and calcination temperature range studied, compared with CeO₂. Using NO + O₂, the soot conversion decreased over CeLaO_x_y catalysts calcined below 800 °C compared with the soot oxidation over CeO₂_y. CePrO_x_y, on the other hand, showed a superior soot oxidation activity in the whole composition and calcination temperature range using NO + O₂. The improvement in the soot oxidation activity over the various catalysts with O₂ can be explained based on an improvement in the external surface area. The superior soot oxidation activity of CePrO_x_y with NO + O₂ is explained by the changes in the redox properties of the catalyst as well as surface area. CePrO_x_y, having 50 wt.% of dopant, is found to be the best catalyst due to synergism between cerium and praseodymium compared to pure components. NO into NO₂ oxidation activity, that determines soot oxidation activity, is improved over all CePrO_x catalysts.     

Dechlorination of chlorinated hydrocarbons by catalytic steam reforming

Past research in this laboratory on catalytic steam reforming of chlorinated hydrocarbons demonstrated extremely high levels of destruction (0.99999+) at 600–750 °C, with GHSVs as high as 2.5 × 10⁵ h⁻¹. Feasible operation was demonstrated with chlorinated alkanes, alkenes, aromatics and PCBs using Pt/γ-Al₂O₃ catalysts. The major mechanism for deactivation with trichloroethylene was sintering of the γ-Al₂O₃ support and encapsulation of Pt crystallites.

Evidence is presented here that ZrO₂ is a superior support for steam reforming of trichloroethylene (TCE), due to its low acidity and ability to store oxygen. Formulations of 0.8 wt.% Pt/ZrO₂ tested at a GHSV of 20,000 h⁻¹ and a H₂O/C ratio of 20 operated for 42 days at 750 °C, with only slight carbon deposits in the first 15% of the catalyst bed. No pyrolysis was found, and the product CO/CO₂ ratio was at equilibrium, indicating high water gas shift activity with very low CO concentrations. Kinetic measurements revealed a pseudo-first order rate equation, sintering of the support and Pt was much less than with γ-Al₂O₃ supports, and no encapsulation was detected. Slow deactivation occurred due to deposition of catalytic carbon. This carbon was removed by combustion with air, and the rate of deactivation indicated the 42-day run would have lasted seven months.     

The nature of low temperature deactivation of CoCr2O4 and CrOx/γ-Al2O3 catalysts for the oxidative decomposition of trichloroethylene

The CoCr₂O₄ and CrO_x/γ-Al₂O₃ catalysts were used for the oxidative decomposition of trichloroethylene (TCE). Both catalysts showed an initial deactivation at low temperatures around 280 °C, mainly due to the dissociative adsorption of reactant TCE. This was confirmed by the temperature programmed oxidation of TCE where the carbon oxides were formed up to a temperature below 300 °C. Possible changes in the oxidation state of chromium species were observed with XANES and ESR. During the oxidation reaction at low temperatures, the Cr(VI) species were reduced to Cr(III) species, which seemed to be coupled with TCE adsorption. At higher temperatures, however, the Cr(VI) species appeared again and the catalytic activity was completely recovered.     

Potential rare-earth modified CeO2 catalysts for soot oxidation part II: Characterisation and catalytic activity with NO + O2

Ceria (CeO₂) and rare-earth modified ceria (CeReO_x with Re = La³⁺, Pr^3+/4+, Sm³⁺, Y³⁺) supports and Pt impregnated supports are studied for the soot oxidation under a loose contact with the catalyst with the feed gas, containing NO + O₂. The catalysts are characterised by XRD, H₂-TPR, DRIFT and Raman spectroscopy. Among the single component oxides, CeO₂ is significantly more active compared with the other lanthanide oxides used in this study. Doping CeO₂ with Pr^3+/4+ and La³⁺ improved, however, the soot oxidation activity of the resulting solid solutions. This improvement is correlated with the surface area in the case of CeLaO_x and to the surface area and redox properties of CePrO_x catalyst. The NO conversion to NO₂ over these catalysts is responsible for the soot oxidation activity. If the activity per unit surface area is compared CePrO_x is the most active one. This indicates that though La³⁺ can stabilise the surface area of the catalyst in fact it decreases the soot oxidation activity of Ce⁴⁺. The lattice oxygen participates in NO conversion to NO₂ and the rate of this lattice oxygen transfer is much faster on CePrO_x. In general, the improvement of the soot oxidation is observed over the Pt impregnated CeO₂ and CeReO_x catalysts, and can be correlated to the presence of Pt°. The surface reduction of the supports in the presence of Pt occurred below 100 °C. The surface redox properties of the support in the Pt catalysts do not have a significant role in the NO to NO₂ conversion. In spite of the lower surface area, the Pt/CeYO_x and Pt/CeO₂ catalysts are found to be more active due to larger Pt crystal sizes. The presence of Pt also improved the CO conversion to CO₂ over these catalysts. The activation energy for the soot oxidation with NO + O₂ is found to be around 50 kJ/mol.     

Novel low temperature NOx storage-reduction catalysts for diesel light-duty engine emissions based on hydrotalcite compounds

A series of Pt and Pt,Cu supported catalysts were prepared by wet impregnation of Mg–Al supports obtained from hydrotalcite-type (HT) precursor compounds. These novel NO_x storage-reduction (NO_xSR) catalysts show improved performances in NO_x storage than Pt,Ba/alumina NO_xSR catalysts at reaction temperatures lower than 200 °C. These catalysts show also improved resistance to deactivation by SO₂. The effect is attributed to the formation of well dispersed Mg(Al)O particles which show good NO_x storage properties. The promoted low temperature activity is explained by the lower basicity of the Mg(Al)O mixed oxide in comparison to BaO, which induces on one hand a lower inhibition on Pt activity (NO to NO₂ oxidation and/or hydrocarbon oxidation) due to electronic effect, and on the other hand a lower thermal stability of the stored NO_x. The presence of Cu slightly inhibits activity at low temperature, although improves activity and resistance to deactivation at 300 °C. On these catalysts FT-IR characterization evidences the formation of a Pt–Cu alloy after reduction.     

Catalytic effect of platinum on the kinetics of carbon oxidation by NO2 and O2

The effect of a commercial Pt/Al₂O₃ catalyst on the oxidation by NO₂ and O₂ of a model soot (carbon black) in conditions close to automotive exhaust gas aftertreatment is investigated. Isothermal oxidations of a physical mixture of carbon black and catalyst in a fixed bed reactor were performed in the temperature range 300–450 °C. The experimental results indicate that no significant effect of the Pt catalyst on the direct oxidation of carbon by O₂ and NO₂ is observed. However, in presence of NO₂–O₂ mixture, it is found that besides the well established catalytic reoxidation of NO into NO₂, Pt also exerts a catalytic effect on the cooperative carbon–NO₂–O₂ oxidation reaction. An overall mechanism involving the formation of atomic oxygen over Pt sites followed by its transfer to the carbon surface is established. Thus, the presence of Pt catalyst increases the surface concentration of –C(O) complexes which then react with NO₂ leading to an enhanced carbon consumption. The resulting kinetic equation allows to model more precisely the catalytic regeneration of soot traps for automotive applications.     

The reduction of perchlorate by hydrogenation catalysts

Perchlorate competes with thyroid uptake of iodide, an essential nutrient for the production of thyroid hormones. Despite the extensive attempts to reduce perchlorate in aqueous solution, the process is slow and requires high temperatures even in the presence of catalysts. Therefore, perchlorate reduction under hydrogen atmosphere was employed. Monometallic and bimetallic Pt based catalysts (e.g., Pt/C, Ni-Pt/C, Co-Pt/C, and W-Pt/C) supported on activated carbon were prepared by successive incipient wet impregnation method and used for gas-phase reduction of perchlorate pre-adsorbed onto the activated carbon. The catalysts were characterized for hydrogen chemisorption and XPS. Hydrogen uptake was in the order: Co-Pt/C > W-Pt/C ≈ Pt/C > Ni-Pt/C. The least H₂ uptake by Ni-Pt/C was likely due to lower dispersion on activated carbon surface with 11.5% vs. 36% for Pt/C. There was a good correlation between hydrogen uptake by impregnated activated carbon (IAC) and perchlorate reduction. The Co-Pt/C exhibited the highest hydrogen uptake and the best perchlorate reduction while Ni-Pt/C was the least reducing system. When Co-Pt/C was used almost 90% of perchlorate was reduced at 25 °C and initial surface concentration of perchlorate of 11.47 mg g⁻¹ in 24 h. The reaction rate increased 10-folds when the reaction temperature was raised to 75 °C. In 24 h reaction time, increase of temperature from 25 to 75 °C resulted in additional 10% (Co-Pt/C) and 30% (Ni-Pt/C) increase in perchlorate reduction for Co-Pt/AC and Ni-Pt/AC, respectively, which brought the reduction efficiency close to 100%. The only reaction product that evolved was Cl⁻, indicating that the cleavage of the first oxygen atom of perchlorate was the rate-limiting step. The lowest activation energy for the reduction of perchlorate was 39.5 kJ mol⁻¹ for Co-Pt/C. Results also showed that the activation of gaseous hydrogen molecules on metal catalysts was the major reducing step, although deposited metals also participated in the perchlorate reduction directly. Results of XPS analysis revealed that during adsorption/reduction some portion of the second metal in the bimetallic catalysts was lost due to dissolution while Pt was very stable.