P. Corbo

Catalytic oxidation of soot from diesel exhaust gases: 1. Screening of metal oxide catalysts by TG-DTG-DTA analysis

Abstract Thermal analysis was employed as a screening technique to evaluate the activity of catalysts for the oxidation of soot produced during combustion. Oxidation took place over metal-oxide-based catalysts at temperatures much lower than in the absence of catalyst. Best results were displayed by a Cu/V/K-supported catalyst which is very active at about 330 °C. In the absence of oxygen, 16% of soot was oxidised by the oxygen of the catalyst, suggesting that a redox mechanism is involved.

Catalytic combustion of carbon particulate

Abstract The catalytic combustion of carbon particulate was investigated with the aim of developing a catalyst for the abatement of soot in diesel exhausts. In the presence of a Cu/V/K based catalyst a strong increase of the rate of carbon combustion and a marked decrease of the apparent activation energy were observed. The carbon reactivity showed a linear dependence upon the initial ratio of the mass of catalyst to the mass of carbon and a square root dependence upon the oxygen partial pressure. However, catalytic combustion of diesel soot and partially graphitized carbon black confirmed previous results obtained for other carbon materials. In particular, kinetic data follow a model proposed for the catalytic combustion of amorphous carbon black [1]. An extension of this model, incorporating the influence of carbon-catalyst contact on the catalyst performances, has been presented.

Lean NOx reduction CuZSM5 catalysts: Evaluation of performance at the spark ignition engine exhaust

Abstract CuZSM5 catalysts, prepared by ion exchange of HZSM5 (Si/Al = 80), enable selective lean NOχ reduction at the spark ignition engine exhaust. All catalysts, even if exchanged to very high copper loading (556% apparent exchange level) give no evidence for segregated copper oxide phases. In the presence of water they are easily reduced in vacuum at 550°C and are stable to redox cycles (O2, vacuum) treatments. Increasing Cu content to about 200% apparent exchange level results in increasing NOχ, CO and HC conversions. From 200 to 550% exchange CuZSM5 catalysts give similar performances. Preliminary investigation shows that after catalytic tests there is evidence for CuO formation only in the copper-richest catalysts.

Ammonia removal from wastewater by natural zeolites. I. Ammonium ion exchange properties of an Italian phillipsite tuff

Abstract Physico-chemical characteristics and ammonium ion exchange properties of an Italian phillipsite tuff have been determined in comparison with Hector clinoptilolite. Sodium form of phillipsite was ion exchanged by solutions containing different competing cations. Ammonia uptake being comparable, phillipsite exhibited higher selectivity for NH4+. Breakthrough curves were modelled by numerical solutions based on constant pattern conditions.

Potentialities and limitations of lean de-NOx catalysts in reducing automotive exhaust emissions

Abstract The performance of Pt–γ-Al 2 O 3 and CuZSM5 de-NO x catalysts was evaluated at the exhaust of a lean-burn gasoline engine. It is shown that durability for zeolite catalysts and N 2 O formation for Pt catalysts are the main limitations which have to be still overcome to successfully apply the lean de-NO x technology.

Study of catalytic filters for soot particulate removal from exhaust gases

Two ceramic supports (sintered and foam) were employed for the preparation of catalytic filters for soot removal at diesel exhausts. Laboratory tests showed that while the foam filter is appropriate for small size and low engine backpressure, the sintered filter is more suitable for achieving high filtration efficiency. Tests carried out at the exhaust of a diesel engine showed that the catalytic filter can be continuously regenerated at operating conditions typical of diesel exhaust.

Investigation of Co-Based DeNOx Catalysts for the Treatment of Natural Gas Lean-Burn Engine Exhaust

The catalytic reduction of nitric oxide with methane in lean conditions has been investigated on cobalt-based powder and monolith catalysts such as Co-exchanged ferrierite, Co-exchanged beta zeolite and Co–ZrO2. From catalyst laboratory testing the following activity scale was obtained: Co-ferrierite > Co-beta >>> Co–ZrO2, suggesting a significant role of the support catalytic matrix. In the tests at the engine exhaust, the best results were obtained with Co-ferrierite, after water separation from the exhaust. However, in the presence of the high concentration of water, typical of the engine exhaust, the performances were dramatically reduced.

The effect of preparation and steaming on the catalytic properties of Cu-and Co-ZSM-5 in lean NOx reduction

Publisher Summary This chapter presents the effect of preparation and steaming on the catalytic properties of Cuand Co-ZSM-5 in lean NOx reduction. H-ZSM-5 zeolite with Si/AI=80 is easily overexchanged with copper and cobalt ions using metal acetate solutions. The reason for this is related very likely both to the presence in solution of polymeric Mx(OH)y(2X-y) + species and the structure defects (Si vacancies) in the H-ZSM-5. Moreover, in the case of Cu-ZSM-5, copper overexchange can be due to the formation of a copper hydroxyacetate, favoured by both higher temperature and concentration of copper acetate solution. The characterization of both Cu-ZSM-5 catalysts gives evidence for some modifications of the nature of copper species, but does not allow concluding that different modifications are induced by the preparation method. The formation of copper hydroxyacetate does not result in modifying the initial catalytic activity in the test at the gasoline engine exhaust. Nevertheless, preliminary results of durability test indicate that the deactivation rate is strongly affected by the preparation method of overexchanged Cu-ZSM-5 catalysts.

Lean NOx reduction on Cu-NaY and Cu-HZSM5 zeolites at the spark ignition engine exhaust

Abstract The lean NO x reduction on the Cu-NaY and Cu-HZSM5 catalysts has been investigated at the spark ignition engine exhaust. Catalysts prepared by exchange method at different Cu loadings were characterized by XRD, XPS, ESR and redox treatments with CO and O 2 . The results show similar performance of Cu-HZSM5 and Cu-NaY. Reaction rates, normalized with respect to the total copper, resulted five times higher for Cu-HZSM5 compared to Cu-NaY. The nature of sites active for the lean NO x reduction is compared with that for the NO decomposition. It is concluded that different sites are operated for the two reactions and that a much higher fraction of copper is involved in the lean NO x reduction compared to the NO decomposition.

Ammonia Removal from Municipal Water by Phillipsite

The performance of Italian phillipsite tuff has been investigated, with the objective of checking the utilization in the RIMNUT process for ammonium removal from municipal wastewater. Basic ion exchange properties have been determined in small-scale column tests with synthetic effluents. Attrition resistance was evaluated by fluidized bed test. Operation of 35 exhaustion/regeneration cycles with real secondary effluent was performed in an automatic laboratory pilot plant. Comparison with the performance of commercial clinoptilolite has shown that Italian phillipsite is an effective alternative for the utilization in ammonium removal processes.