Marie Ruwet

Influence of the preparation method on the V2O5/TiO2/SiO2 catalysts in selective catalytic reduction of nitric oxide with ammonia

The method of deposition of TiO2 on SiO2 and the activation procedure of the silica permits the control of the dispersion of both TiO2 and V2O5 on the surface of the catalysts. Activation of SiO2 by acidic treatment followed by deposition of isopropyl orthotitanate in n-heptane by reflux gives a support with titanium oxide close to monolayer coverage. The dispersion of vanadium oxide and its interaction with the support are then enhanced. The catalytic reduction of nitric oxide with ammonia at two different nitric oxide concentrations is evaluated at 693 and 773 K and correlated with the physicochemical properties of the solids.

Simultaneous removal of SO2/NOx from flue gases. Sorbent/catalyst design and performances

Abstract The kinetic and mechanistic aspects of the interaction of SO 2 with supported copper-based sorbent/catalysts, of the regeneration of the sorbent/catalyst by reductive treatment and of the interaction of the sulfated sorbent/catalyst with ammonia and NO x to form N 2 are discussed with reference to sorbent/catalyst and reactor design for efficient simultaneous removal of SO 2 /NO x from flue gases in a single stage reactor.

Selective Catalytic Reduction of Nitric-oxide With Ammonia Using Moo3/tio2 - Catalyst Structure and Activity

A series of titania supported MoO3 catalysts (0-20 wt.-% MoO3) were prepared by dry impregnation. The influence of the MoO3 content on their catalytic performance for the selective catalytic reduction (SCR) of nitric oxide by ammonia in the presence of oxygen, as well as on their textural and structural properties has been studied. The samples were characterized by XRD, XPS, IR, and BET and porosimetry measurements. The coverage of the TiO2 support by surface polymeric molybdenum species (where molybdenum is octahedrally coordinated) increases with the molybdenum loading. The formation of a layer of these interacting species on top of the titania surface is complete in the range 15-20 wt.-% MoO3. The formation of crystallites of bulk MoO3 starts before the completion of this surface layer (at around 10 wt.-% MoO3) and increases progressively as the molybdenum loading increases from 10 to 20 wt.-% MoO3. The SCR activity of the MoO3/TiO2 catalysts increases as the MoO3 content increases to 15 wt.-% and then, for a further increase of the molybdenum loading, it slightly decreases. No specific influence of the molybdenum content on the resistance of catalysts towards SO2 was observed; the same slight deactivation took place, when the SCR activity was measured in the presence of SO2 in the feed, for all samples. Our results indicate that the octahedrally coordinated polymeric molybdenum surface species are mainly responsible for the exhibited SCR activity of the MoO3/TiO2 catalysts.

Preparation, characterisation and catalytic behaviour of cobalt–niobia catalysts

Cobalt-niobia catalysts were prepared using the colloidal sol-gel technique. Niobium chloride or niobia oxide were used as precursor. The differences between the procedures used are due to the methods of preparation of the colloidal suspensions and gelification. The catalysts were characterised using adsorption and desorption curves of Kr and N-2 at 77 K, H-2-Chemisorption, XRD, FT-IR, XPS and electron microscopy investigations. Preparation of these catalysts without experimental precautions led to a very inhomogeneous structural and textural material. In contrast, the colloidal sol-gel technique controls both the structure of the niobia oxide and the tailoring of cobalt. A strong metal support interaction effect (SMSI) was present irrespective of the sample preparation variant. Although the rate of butane hydrogenolysis was low for all catalysts, a correlation between TOF and the catalyst crystallite size was found. Selectivity to methane, ethane, propane or to isomerization also depends on the catalyst crystallite size

A Way To Inhibit So2 Poisoning of Scr Catalysts By Fine-tuning of the Composition and the Preparation Method of the Support

Two series of mixed SiO2-TiO2 and Al2O3-TiO2 supports were prepared by the following methods : precipitation from TiCl4 solution with aqueous ammonia, impregnation with titanium isopropoxide solution in isopropanol, and grafting by reaction of TiCl4 with the hydroxyl groups of the main carrier (SiO2 or Al2O3). The vanadia catalysts, resulting from the impregnation of these mixed supports with an aqueous solution of vanadium oxalate, were tested in the selective catalytic reduction (SCR) of NO with NH3 in the presence of O2. BET, XRD and XPS were used to characterise the samples. All these catalysts were less active than a standard TiO2-V2O5 catalyst when tested with a SO2-free feed. However, in the presence of 4000ppm SO2 in the feed they were more resistant and more active than the TiO2-V2O5 catalyst. Our results indicate that the dispersion of TiO2 on the main carrier is a key factor for preparing a performant SCR catalyst. The grafting and impregnation methods for the Al2O3-TiO2 and the impregnation for the SiO2-TiO2 supports were found to be the most effective preparation techniques for dispersing TiO2, and for giving the most performant and resistant, towards SQ2 poisoning, catalysts.

Sol—gel synthesis of cobalt—niobia catalysts

Cobalt-niobia catalysts were prepared using different variants of the colloidal sol-gel technique and wetness impregnation. Characterization of these catalysts by XRD, FT-IR, XPS and TEM showed that phases structure as well as superficial composition depended on the preparation route. It was found that niobia exhibits a strong metal support interaction effect and this effect depends on the dimension of the metallic cobalt on the support surface. Reactivity of these catalysts was checked in n-butane hydrogenolysis, a well known structural sensitive reaction. The catalytic tests showed the influence of the catalysts features both on the reaction rate and selectivity.

Deactivation of Aluminas and Phosphates Catalysts in 1-Butanol Dehydration

Abstract The resistance to deactivation of aluminas(γ-Al 2 O 3 pure or modified with F -1 , Zn ++ , Na + ) and phosphates(B-PO 4 > Al-PO 4 , Ca-Ni-PO 4 ) catalysts was investigated with pure 1-butanol under various reaction conditions. In the corresponding laboratory tests, our catalysts are not subject to deactivation. An activity decrease and selectivity changes were observed after a run with synthetic acetonobutylic mixtures containing, in addition to 1-butanol, acetone, ethanol, acetic acid and water. After the catalytic tests, the coke content was low. The combined role of the presence of water and organic molecules other than 1-butanol (especially acetic acid) in the feed explains the catalytic activity decrease.

Solid state reaction in Mg-V-O-Sb catalysts

MgVO oxide with Mg/V atomic ratios of 2/2 and 3/2, were mixed mechanically with alpha-Sb2O4. Chemical changes during oxidative dehydrogenation of propane (ODP) and under calcination treatment were studied. In Mg/V(2/2) + alpha-Sb2O4, magnesium vanadate is contaminated during ODP and a new phase, MgSb2O6, was formed after only 1 day of calcination at 823 K. In Mg/V(3/2) + alpha-Sb2O4, no indication of surface contamination or new phase formation was detected during ODP or calcination. The catalytic performances of both mixtures are explained in the light of these results.