ZSM-5 Support Research Articles

Synthesis and application of ZSM-5/SAPO-34 and SAPO-34/ZSM-5 composite systems for propylene yield enhancement in propane dehydrogenation process

Two types of zeolitic composite systems with binary hierarchical structures comprising ZSM-5 and SAPO-34 molecular sieves were synthesized employing different procedures. Obtained products were served as catalytic carriers for propane dehydrogenation reaction so as to promote the physicochemical properties of ZSM-5 support, enhance the propylene yield and reduce the formation of light compounds. ZSM-5/SAPO-34 was fabricated in a series hydrothermal procedure employing pre-heated ZSM-5 suspension followed by secondary growth of SAPO-34 layer whereas SAPO-34/ZSM-5 was synthesized using tetrapropylammonium bromide exchanged-SAPO-34 crystals and pre-reacted ZSM-5 slurry in a hydrothermal one-step process. The products were characterized by XRD, FESEM, EDS, FTIR, NH3-TPD, and N2 adsorption–desorption techniques to investigate the textural and structural properties of composite architectures. The catalytic performance of the bimetallic Pt-Sn-based composites were evaluated in propane dehydrogenation reaction and compared with those of physical mixture and single ZSM-5-derived catalysts. Either of composites represented improved catalytic performance due to the synergetic effect between ZSM-5 and SAPO-34, which promoted the catalytic properties of the samples. Catalytic reactivity of the composite catalysts was strongly dependent on the synthesis method and employed zeolite/zeotype ratio. Best result was acquired for Pt–Sn-based SAPO-34/ZSM-5 (Si/Al=60) brand-new efficient composite with improved stability, boosted conversion and significant selectivity towards light olefins, propylene in particular.

Selective hydrogenation of D-glucose to D-sorbitol over Ru/ZSM-5 catalysts

Ru particles were introduced into the zeolite ZSM-5 (MFI) by either a conventional impregnation method or a one-step template-free process. The resultant materials were characterized by X-ray diffraction, N 2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, NH 3 and CO 2 temperature-programmed desorption. The results indicated that the Ru species in ZSM-5 catalysts prepared via the latter approach (designated as Ru/ZSM-5-TF) were highly dispersed in the ZSM-5 framework structure and this material exhibited high catalytic performance during the hydrogenation of D-glucose to D-sorbitol. The conversion of D-glucose was as high as 99.6% with D-sorbitol selectivity reaching 99.2%, exceeding the performance of Ru/ZSM-5 catalysts prepared by the conventional impregnation method with microporous or desilicated ZSM-5 supports. More importantly, this catalyst showed high stability against leaching and poisoning and could be reused several times. The extensive dispersion of the Ru species, strong interaction between the Ru species and the ZSM-5, and the suitable surface acidity-basicity balance of the Ru/ZSM-5-TF were all critical factors leading to excellent catalytic behavior and stability. d -glucose was selectively converted into D-sorbitol with a yield of 99.2% over a Ru/ZSM-5-TF catalyst synthesized via a template-free hydrothermal method. This catalyst could be recycled via a simple regeneration process.

Partial oxidation of methane with nitrous oxide forms synthesis gas over cobalt exchanged ZSM-5

Synthesis gas (CO+H2) is a versatile and significant resource. In this communication we show that cobalt loaded on ZSM-5 (Co-ZSM-5) catalyses the formation of synthesis gas from CH4, under partial oxidation conditions using N2O as oxidant. With O2 as oxidant over the same Co-ZSM-5 catalyst, cobalt on alumina and Fe-ZSM-5, only COx and H2O are formed. Isolated Co2+ sites in the ZSM-5 support are proposed as the active sites for H2 (synthesis gas) formation.

New insight into the activity of ZSM-5 supported Co and CoRu bifunctional Fischer–Tropsch synthesis catalyst

The PEG-additive method was used to prepare the ZSM-5 supported Co- and CoRu-based bifunctional Fischer–Tropsch synthesis (FTS) catalysts. This method facilitated the deposition of Co3O4 particles on the exterior surface of ZSM-5 support. The resultant catalyst had better reducibility than the conventional impregnation method derived catalyst. Although the PEG-additive protocol could improve the CO conversion on Co/ZSM-5 catalyst, the ZSM-5 supported Co catalyst adsorbed H species stronger than the SiO2 supported Co catalyst. As a result, the Co/ZSM-5 catalyst had lower turnover frequency (TOF) than Co/SiO2 catalyst. The presence of trace Ru promoter by the PEG-additive method could form bimetallic CoRu particles on CoRu/ZSM-5 catalyst. The Co–Ru synergistic effect improved the TOF value and the C5+ selectivity of CoRu/ZSM-5 catalyst by weakening the interaction between the H species and catalyst instead of altering the nature of Co0 sites. This effect allowed the CoRu/ZSM-5 catalyst produce more gasoline-range hydrocarbons than Co/ZSM-5 catalyst in the FTS reaction.

Oxidative dehydrogenation of n-butane over bimetallic mesoporous and microporous zeolites with CO2 as mild oxidant

Oxidative dehydrogenation of n-butane was tested using carbon dioxide as a mild oxidant over bimetallic Cr–V supported catalysts (MCM-41, ZSM-5, MCM-22 and mesoZSM-5). The textural properties of the catalysts were measured by means of XRD, N2 adsorption, SEM-EDX, Raman, H2-TPR, pyridine FT-IR, NH3 and CO2-TPD techniques. The metal content of Cr and V was maintained around 1.2 and 2.8 wt% for the catalytic test in packed bed reactor at different temperatures (525–600 °C) for 180 min. 1.2Cr2.8 V/MCM-41 and 1.2Cr2.8 V/ZSM-5 exhibited maximum conversion of 14 and 13.1 %, respectively at 10 min and 600 °C. Significantly, high butenes selectivity was observed over MCM-41 (86.27 %) than ZSM-5 support (58.1 %). The mesoporosity in ZSM-5 had a negative impact on conversion level (7.1 %) but improved the butenes selectivity slightly. 1.2Cr2.8 V/M-22 showed the highest cracking ability leading to overall reduced butenes selectivity (57.9 %). The study shows that over all catalysts, n-butane conversion is independent of CO2 conversion. 1.2Cr2.8 V/M-22 showed highest CO2 conversion in the range 2.35–2.2 % between 525 and 550 °C. The apparent activation energies of dehydrogenation and cracking reaction over the four catalysts were evaluated. The ratio of conversion to coke weight per cent over the four catalysts are observed in the following order: 1.2Cr2.8 V/M-41 > 1.2Cr2.8 V/Z-5 > 1.2Cr2.8 V/mesoZ-5 > 1.2Cr2.8 V/M-22.

Low temperature CO oxidation over Pd–Ce catalysts supported on ZSM-5 zeolites

A series of Pd–Ce supported ZSM-5 zeolite catalysts for CO oxidation at low temperature were prepared by co-impregnation method. The effect of Pd–Ce synergistic function, Ce loadings, and properties of ZSM-5 zeolite on low temperature CO catalytic oxidation was investigated in detailed. The results showed that the Pd and Ce loading on ZSM-5 zeolite support at the same time enhanced catalytic activity compared with only Pd or Ce loading on ZSM-5 zeolite support. The properties of ZSM-5 zeolite had a strong influence for CO oxidation. Through the research, the ZSM-5 zeolite with high silicon aluminum ratio and small size also was helpful for CO oxidation. Among these catalysts, the catalyst with 19wt% Ce loading displayed the highest catalytic activity. Chemical and physical properties of catalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). XRD and TEM showed that Pd species were highly dispersed on the surface of ZSM-5 zeolite, which was strongly dependent on the amounts of Ce loading and the interaction among Pd species, Ce promoter and ZSM-5 support. The addition of CeO2 improved the dispersion of Pd species over ZSM-5, and synergistic function of Pd and CeO2 enhanced the catalytic activity. XPS characterization indicated that as the addition of Ce increased, Pd species was easy to enrich on the surface of the catalyst.

Mn–Fe/ZSM5 as a low-temperature SCR catalyst to remove NOx from diesel engine exhaust

A Mn–Fe/ZSM5 catalyst has been developed for removing NOx from diesel engine exhausts and its excellent low-temperature SCR activity and N2 selectivity demonstrated in comparison with other representative SCR catalysts including CuZSM5 and a Cu-based commercial catalyst (COM). The well-dispersed MnO2 and the high NH3 adsorption capacity of the Mn–Fe/ZSM5 catalyst have been identified as the primary sources for its high deNOx activity for NH3/SCR. Hydrothermal stability and durability of the Mn–Fe/ZSM5 catalyst have been examined and compared to those of the CuZSM5 and COM catalysts. The hydrothermal stability of the catalyst improved upon the increase of Mn content and/or the addition of Er, the latter of which helps to stabilize the dispersion of MnOx on the catalyst surface during hydrothermal aging. The deNOx activity of the Mn–Fe/ZSM5 and its Er-promoted counterpart was less affected by HC poisoning, C3H6 poisoning in particular, compared to the CuZSM5 and COM catalysts, mainly due to the excellent C3H6 oxidation activity of MnO2. No poisoning of the Mn-based ZSM5 and CuZSM5 catalysts has been observed upon the addition of 2wt.% of K+ and Ca2+ to their surface, primarily due to the high NH3 adsorption capacity of the ZSM5 support, whereas the COM catalyst has been severely deactivated by the deposition of K+ and Ca2+. The deNOx activity of the Mn-based ZSM5 catalyst, particularly the Er-promoted one, was less affected by SO2 compared to the CuZSM5 and COM catalysts, although it was hardly regenerated at 500°C. Formation of MnSO4 on the catalytic surface appears to be the primary cause for the deactivation of the Mn-based ZSM5 catalysts in the presence of SO2 in the feed gas stream.

Effects of Zinc and Magnesium Addition to ZSM-5 on the Catalytic Performances in 1-hexene Aromatization Reaction

Effects of Zn and Mg addition on the catalytic performances of ZSM-5 in 1-hexene aromatization and isomerization were investigated. NH3-TPD and Pyridine-IR spectra revealed that the addition of Zn could increase the Lewis acidity amount of the support. And the catalytic aromatization activity was improved. Introduction of Mg resulted in a decrease of total acidity, especially for Brϕnsted acid sites which was beneficial for the high iso-paraffin and liquid product yield. The optimal modification way on ZSM-5 was obtained as addition of Mg with successive Zn introduction which may lead to the presence of Zn species inside of the zeolite channel evidenced by XPS results. The close proximity of Zn species to Brϕnsted acid sites may enhance the synergy effect between them in the aromatization reaction. The optimized Zn–Mg/HZSM-5 sample also exhibited good catalytic performance when using FCC gasoline as reactant. 2Zn–4Mg/AT-Z5 catalyst prepared by Mg addition with successive Zn introduction on modified ZSM-5 support showed optimal product distribution in 1-hexene aromatization reaction.

Aviation fuel production from lipids by a single-step route using hierarchical mesoporous zeolites

Hierarchical mesoporous molecular sieves with tunable zeolitic crystallinity, acidity and porosity were tailored to develop a single-step process for hydroconversion of triglycerides and free fatty acids obtained from algae and Jatropha seeds. Ni-W catalyst supported on acidic zeolitic ZSM-5 support with hierarchical structure and intra-crystalline mesoporosity with composition similar to that for typical hydrocracking catalyst could yield 40–45% C9–C15 hydrocarbons and high isomerization selectivity (isomer/n-alkane, i/n ~ 2–6) from Jatropha oil. While Ni-Mo catalysts on the same support furnished 40–50% kerosene range hydrocarbons with i/n ~ 3–13. For algal oil feed hydroconversion using sulfided Ni-Mo catalyst supported on high surface area semi-crystalline ZSM-5, unexpectedly high yield of jet-fuel range hydrocarbons (77%) with moderately high isomerization selectivity (i/n = 2.5) could be obtained.

Preparation of highly active platinum nanoparticles on ZSM-5 zeolite including cerium and titanium dioxides as photo-assisted deposition sites

Nano-sized Pt particles with high activities for CO oxidation have been successfully synthesized on the metal dioxide phases (CeO 2 and TiO 2) included within ZSM-5 zeolite by a photo-assisted deposition (PAD) method under UV-light irradiation. The obtained Pt nanoparticles on CeO 2 within ZSM-5 by the PAD method (PAD-Pt/CeO 2/ZSM-5) showed the highest catalytic activity for CO oxidation even at low temperature. The dispersion of Pt nanoparticles was investigated by CO adsorption, XAFS, and TEM analyses. The size of Pt nanoparticle of the PAD-Pt/CeO 2/ZSM-5 catalyst was determined to be 2 nm. In addition, this catalyst has unique morphology; the Pt nanoparticles were selectively deposited on the CeO 2 within ZSM-5 supports. It is found that the addition of CeO 2 into the catalyst supports is effective to synthesize highly active nano-sized Pt particles using the PAD method under UV-light irradiation.

Characteristics of lanthanum loaded TiO2-ZSM-5 photocatalysts: Decolorization and degradation processes of methyl orange

Abstract Novel photocatalytic materials were prepared by incorporation of lanthanum ions on TiO 2 supported ZSM-5. These materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectra (UV–vis DRS), atomic force microscopy (AFM), scanning electron microscopy SEM with energy dispersive X-ray analysis (EDX) and surface area (BET) measurements. XRD and FTIR results showed adsorption of TiO 2 and La 2 O 3 nanoparticles on the surface of ZSM-5 support. AFM and SEM images revealed obvious variations in the surface morphology of raw ZSM-5 after TiO 2 and La 2 O 3 loading. Photocatalytic activities of the supported catalysts were examined for decolorization and degradation processes of methyl orange (MO) solution under UV irradiation. Incorporation of lanthanum ions improved the photocatalytic activities of TiO 2 supported ZSM-5 catalysts. Effects of TiO 2 content, lanthanum ion content and calcination temperature were investigated. Quantum efficiencies, relative photonic efficiencies as well as reuse performances of the supported catalysts were also demonstrated. A rough model was postulated for TiO 2 and La 2 O 3 loading on the surface of ZSM-5.

Highly selective vapor phase nitration of toluene to 4-nitro toluene using modified and unmodified H3PO4/ZSM-5

Abstract The nitration of toluene has been studied in the vapor phase at various temperatures over a series of surface modified and unmodified ZSM-5 (Si/Al = 170) loaded with H 3 PO 4 , differing in the external surface treatment of the zeolites. All samples were characterized by X-ray diffraction, BET and FT-IR. The nature of acid sites of the supports, i.e., H 3 PO 4 /ZSM-5-surf-170 and H 3 PO 4 /ZSM-5-170 was determined using FT-IR-pyridine adsorption study. 2,4,6-Trimethyl pyridine adsorption was used for calculating the external surface acidity of the H 3 PO 4 /ZSM-5-surf-170 and H 3 PO 4 /ZSM-5-170. The superior performance of the externally blocked catalysts (modified) relevant to the H 3 PO 4 /ZSM-5-170 catalyst shows that by blocking the external surface area of the ZSM-5 support, it exhibits a superior catalytic selectivity than the unmodified catalyst. Catalysts containing 0–4.9 wt.% P were prepared using ZSM-5-surf-170 and ZSM-5-170, and their catalytic performance was determined for the vapor phase nitration of toluene to 4-nitrotoluene (4-NT), 2-nitrotoluene (2-NT) and oxidation products. The effect of reaction temperature, H 3 PO 4 content, feed ratio of toluene to HNO 3 , WHSV, TOS and carrier gas flow rate was also investigated.

Influence of the surface acidity of ZSM-5 support on the catalytic activity of Rh/ZSM-5 for hydrodearomatization of toluene

Rh/ZSM-5 catalysts with varied SiO 2/Al 2O 3 ratio (24–900) were prepared and characterized by powder X-ray diffraction, N 2 adsorption–desorption, temperature-programmed desorption of NH 3 and cyclohexanol dehydration model reaction. The hydrodearomatization of toluene was studied at different reaction temperature, reduction temperature, hydrogen partial pressures and in the presence of dibenzothiophene (sulfur compound) in a continuous-down-flow catalytic fixed bed reactor. The hydrodearomatization activity and the sulfur tolerance were observed to be strongly dependent on the acidity of the zeolites particularly upon the proximity between metallic and Brønsted acid sites and the concentration of the Brønsted acid sites.

Internal versus external surface active sites in ZSM-5 zeolite: Part 1. Fries rearrangement catalyzed by modified and unmodified H 3PO 4/ZSM-5

The Fries rearrangement of phenylacetate has been studied in the vapor-phase at 623 K over a series of surface modified and unmodified ZSM-5 (Si/Al = 60−170) loaded with H 3PO 4, differing in the external surface treatment of the zeolites. When the external surface of the zeolite is blocked with a surfactant before loading it with H 3PO 4, the selectivity to form the 4-hydroxyacetophenone was higher. This superior performance of the externally blocked catalysts, relative to the unmodified H 3PO 4/ZSM-5 catalyst, shows that by blocking the external surface area of the ZSM-5 support, it exhibits a superior catalytic selectivity than the unmodified catalyst. Catalysts containing 0–4.9 wt.% P were prepared using modified and unmodified ZSM-5 zeolites, and their catalytic performance for vapor-phase Fries rearrangement of phenylacetate to 2-hydroxyacetophenone (2-HAP), 4-hydroxyacetophenone (4-HAP) and 4-acetoxyacetophenone (4-AAP) was determined. The influence of the operating parameters on the performance of H 3PO 4/ZSM-5-surf catalysts was also investigated.

Characterization of bifunctional Pt/H[Ga]ZSM5 and Pt/H[Al]ZSM5 catalysts: II. Evidences of a Pt–Ga interaction

The purpose of this work is to elucidate how platinum supported on a gallosilicate of the MFI type interacts with extra-framework and/or framework gallium, thus affecting the properties of bifunctional catalysts of the Pt/H[Ga]MFI type. To this end, a gallosilicate and an aluminosilicate of the MFI type, with a Si/M atomic ratio ≅ 15 (M = Ga, Al) were synthesized and characterized by X-ray diffraction (XRD), nitrogen physical adsorption at −196 °C, and chemical analysis by ICP-AES. These zeolites were used as supports in the preparation of a series of bifunctional catalysts with varying Pt content: 0.10 wt.% Pt/H[Ga]ZSM5, 0.50 wt.% Pt/H[Ga]ZSM5, 1.00 wt.% Pt/H[Ga]ZSM5 and 1.00 wt.% Pt/H[Al]ZSM5, which were assessed by transmission electronic microscopy (TEM); dispersion of the supported phase was found to range within 50 and 80%. The supports (gallosilicate and aluminosilicate) as well as the bifunctional catalysts were characterized by X-ray photoelectron spectroscopy (XPS) to determine the chemical species on their surfaces. The presence of extra-structural gallium was observed in Pt/H[Ga]ZSM5, which could be found most probably as Ga 2O 3; the presence of Pt 0, Pt–O ads, and PtO in Pt/H[Ga]ZSM5 and Pt/H[Al]ZSM5 was also observed. It was also evidenced an increase in surface gallium concentration as the content of platinum increases in the Pt/H[Ga]ZSM5 solids. The bifunctional catalysts were catalytically tested under standard conditions by the acetone transformation reaction. The results of the catalytic test confirms that the 1.00 wt.% Pt/H[Al]MFI catalyst shows an initial global activity four times higher than the 1.00 wt.% Pt/H[Ga]MFI one, and additionally a selectivity to the desired product (methyl isobutyl ketone, MIBK), three times higher. The activity and selectivity results observed for the Pt/H[Ga]MFI solids are remarkably similar to those found for the pure H[Ga]ZSM5 support. These results clearly show that the platinum metallic centers on the Pt/H[Ga]ZSM5 catalysts are not active for the hydrogenation reactions of the olefinic and/or carbonylic double bonds, probably due to passivation caused by the gallium species on the surface of the bifunctional catalysts.

Regulation of the Dispersion of PdO through the Interaction with Acid Sites of Zeolite Studied by Extended X-ray Absorption Fine Structure

The structure of Pd interacted with acid sites of ZSM-5 was studied by using extended X-ray absorption fine structure (EXAFS). Dispersed PdO was generated on ZSM-5 upon the oxidation treatment, where the degree of dispersion was dependent on the acid amount of ZSM-5 support. The reduction of the dispersed PdO with H2 led to the formation of the agglomerated metal Pd, whose size was larger than ZSM-5 pore. The reoxidation of this metal Pd induced the disruption and the formation of the highly dispersed PdO in ZSM-5 (Si/Al2 = 24) again, which meant the formation of agglomerated metal Pd and dispersed PdO was reversible upon reduction and oxidation treatments. The reversible behavior of Pd was also found on Pd loaded on ZSM-5 with Si/Al2 ratio of 38 and 55, where the slightly aggregated PdO cluster was observed. The fact evidences the possibility to control the size of PdO simply through changing the acid amount of ZSM-5. The dispersion process of Pd from the agglomerated metal form to the dispersed PdO was followed over Pd/ZSM-5 (Si/Al2 = 24). The first step was the simple oxidation of the metal Pd to form agglomerated PdO, which occurred between 573 and 673 K. This was followed by the disruption of the agglomerated PdO into the dispersed PdO in the temperature range between 673 and 773 K. A novel method to regulate the degree of dispersion through the acid−base interaction between acid sites of zeolite and basic metal oxide was proposed.

A comparison between Cu-ZSM-5, Cu–S-1 and Cu–mesoporous-silica–alumina as catalysts for NO decomposition

We prepared H-ZSM-5 (Si/Al=80), amorphous mesoporous silica–alumina (MSA, Si/Al=90), and Silicalite-1 (S-1) according to the methods described by Bellussi and co-workers, and compared their ion-exchange capacity for copper ions. The Cu-ZSM-5, Cu–MSA and Cu–S-1 samples thus obtained have been investigated as catalysts for the NO decomposition reaction at 773 K. We found that using copper acetate solutions with concentrations in the range 0.008 M≤[Cu 2+]≤0.1 M, both at room temperature and at 323 K, it is very easy to prepare over-exchanged Cu-ZSM-5, Cu–S-1 and Cu–MSA catalysts. XRD and Vis–UV DRS techniques show that after thermal treatments of the fresh samples in air at 823 K for 4 h no segregation of CuO phase occurs, suggesting the presence of low nuclearity [Cu n O x (OH) y ] q+ species ( q=2( n− x)− y≥0). These results were confirmed by TPR studies. At 773 K only over-exchanged Cu-ZSM-5 catalysts showed NO decomposition activity (NO 1% in He, W/ F=0.1 gs/cm 3) with a turnover frequency essentially determined by the Si/Al ratio, in agreement with previous literature data. Instead, the activity of Cu–S-1 and Cu–MSA catalysts was not measurable under our experimental conditions. The present results confirm that the framework topology and the presence of framework AlO − 4 species are fundamental to develop active copper species for NO decomposition. It is demonstrated that the active sites in Cu-ZSM-5 consist of copper species strongly anchored to framework AlO − 4 species. The most active sites, as they occur only on ZSM-5 support with the lower Si/Al atomic ratios, might consist of dimeric Cu species (Cu +⋯Cu 2+⋯O −) strongly anchored to next-nearest-neighbour framework AlO 4 − species.

Selective catalytic reduction of NO over metal oxides incorporated zeolites

Selective catalytic reduction (SCR) of nitric oxide in an oxygen-rich atmosphere with propylene as a reductant has been investigated over supported La-Co-oxide (mixed metal oxide) catalysts prepared by the modified citrate method. Loading on ZSM-5 support gave greatly enhanced activity in the reduction of NO at relatively low temperatures. This SCR activity could be ascribed to incorporation of the mixed metal oxide into ZSM-5 as an amorphous perovskite phase via preparation.

Conversion of methane to benzene over Mo2C and Mo2C/ZSM-5 catalysts

The activation and dehydrogenation of CH2 on Mo2C and MO2C/ZSM-5 have been investigated under non-oxidizing conditions. Unsupported Mo2C exhibited very little activity towards methane decomposition at 973 K. The main reaction pathway was the decomposition of methane to give hydrogen and carbon with a trace amount of ethane. Mixing Mo2C with ZSM-5 support somewhat enhanced its catalytic activity, but did not change the products of the reaction. A dramatic change in the product formation occurred on partially oxidized Mo2C/ZSM-5 catalyst; besides some hydrocarbons benzene was produced with a selectivity of 70–80% at a conversion of 5–7%. Carburization of highly dispersed MoO3 on ZSM-5 also led to a very active catalyst: the conversion of methane at the steady state was 5–6% and the selectivity of benzene formation was 85%.

Role of the support and of adsorbed species on the behavior of Cu-based catalysts for No conversion

The catalytic behavior in NO conversion with NH 3 in the presence or absence of O 2 and in NH 3 oxidation to N 2 was studied on a series of copper samples on Al 2O 3, SiO 2, ZrO 2, TiO 2 and ZSM5 supports. The results provide evidence for the role of the support in the change in catalytic behavior of supported copper species, as well as the different influence on the reactivity in NO conversion and on the side reaction of ammonia oxidation. The latter reaction is inhibited considerably by the chemisorption of NO. In addition, the presence or absence of O 2 has considerable influence on the reactivity in NO conversion by ammonia and samples more active in the presence of O 2 are less active in the absence of O 2.