Vanadium impregnation

Catalyst Preparation. For most of the experiments conducted in this study, nickel or vanadium impregnated non-zeolitic particles were blended with metals-free high activity cracking component. This allowed us to examine the effects of the metals on the non-zeolitic component. The high activity zeolitic particles were prepared by in-situ zeolite synthesis on kaolin-based microspheres... 

Figure 8 illustrates the effect of temperature on vanadium mobility (measured on equilibrium catalysts from three FCC units) and the large impact of certain unit variables. For these measurements the coarse equilibrium catalyst was tested in a mobility test using the method described above by substituting sieved coarse equilibrium catalyst for vanadium impregnated catalyst. 

By comparing these results to those obtained using the vanadium porphyrin precursor, it can be concluded that vanadium from the porphyrin tends to stay on the matrix after thermal pretreatments (see Fig. 4), whereas vanadium from the naphthenate is preferentially associated with the zeolite after steaming, Fig. 9. These observations are in agreement with the report (1) that vanadium impregnated from vanadyl naphthenate migrated to the zeolite from the matrix surface during steam treatment. This different behavior of the two precursors... 

Promoters are sometimes added to the vanadium phosphoms oxide (VPO) catalyst during synthesis (129,130) to increase its overall activity and/or selectivity. Promoters may be added during formation of the catalyst precursor (VOHPO O.5H2O), or impregnated onto the surface of the precursor before transformation into its activated phase. They ate thought to play a twofold stmctural role in the catalyst (130). First, promoters facilitate transformation of the catalyst precursor into the desired vanadium phosphoms oxide active phase, while decreasing the amount of nonselective VPO phases in the catalyst. The second role of promoters is to participate in formation of a soHd solution which controls the activity of the catalyst. 

VOx supported on TiOi showed good catalytic activity in the selective oxidation of H2S to ammonium thiosulfate and elemental sulfur. V0x/Ti02 catalysts prepared by the precipitation-deposition method can achieve higher vanadium dispersions, and higher H2S conversions compared to those prepared by the impregnation method. 

V0x/Zr02 catalysts were designated as ZVx(y)pHz, where x gives the analytical vanadium content (weight percent), y specifies the preparation method (a, adsorption, i, impregnation or acac, acetylacetonate) and z the AV solution pH. The V-content was determined by atomic absorption (Varian Spectra AA-30) after the sample had been dissolved in a concentrated (40%) HF solution. 

The carriers were impregnated to different compositions in terms of vanadium content, K/V ratio, Na/V ratio, Cs/V ratio and sulphur content, cf. Fig. 8. The exact sulphur content is less important since the melt, according to reaction (2), takes up an equilibrium amount of SO3 corresponding to a sulphur to alkali metal molar ratio of about 1 during operation in synthesis gas. The impregnation was carried out by submerging the pellets for a period of time in a surplus of aqueous impregnation liquid prepared from sulphuric acid and water-... 

The carriers were impregnated and calcinated in the laboratory, and the activity was subsequently measured in the set-up shown in Fig. 9. The vanadium content was varied in the range 2-5 wt% and the molar ratios between alkali promoter and vanadium were varied in the ranges 0-4 for K/V, 0-2 for Na/V, and 0-3 for Cs/V. The sulphur content was about the same in all impregnations. The measured activities for 3 catalyst compositions A, B, and C impregnated on the same carrier and with the same vanadium content and molar ratios of K/V and Na/V are given in Table 1. The extrudates are made in the 9 mm Daisy form, which is the special 5-finned ring offered by Haldor Topsoe (Fig. 3). The observed pellet activity is reported as a pseudo-1st order rate constant calculated from... 

Catalysts were contaminated with nickel and vanadium according to the method of Mitchell ( ), using metal naphthenates. Prior to blending, all contaminated materials were steamed (1450 F, 4 hrs, 90% steam, 10% air) to age the metals. The selectivity effects of the metals on the non-zeolitic component were determined by blending impregnated non-zeolitic components with 20% of the steamed, uncontaminated high activity zeolitic component such that the overall blend yielded 70% conversion. 

In a series of experimental runs on virgin commercial catalysts and sieves then available and some of our experimental catalysts, we quickly learned that a catalyst impregnated with vanadium, and subjected to high temperatures in steam and air deactivated rapidly. Vanadium, especially in the +5 valence state, rapidly deactivated a catalyst by destroying zeolite crystallinity (Figure 17). In the presence of sodium, the deactivation rate of vanadium was even more severe. (lA-17)... 

The catalysts used in the pilot unit are both equilibrium catalysts from the FCCU at the Statoil Mongstad refinery, and impregnated and deactivated fresh catalysts from different vendors. The catalysts have been impregnated with nickel and vanadium naphthenates. The amount of metals has varied over the years, but the nickel to vanadium ratio has usually been 2 3. The deactivation procedure has also changed over the years, as new deactivation methods have been developed and existing deactivation methods have been improved. 

When discussing the suitability of the ARCO pilot unit for cracking atmospheric residues, this cannot be done without touching on the question about how to prepare the catalysts for testing. An equilibrium catalyst used in a commercial residue FCCU contains significant amounts of metal contaminants, especially nickel and vanadium. Fresh catalysts must therefore be impregnated with these metals and deactivated before the catalysts can be nsed in the pilot unit. We have shown that this... 

The catalysts were calcined at 600°C for 2 hours, and impregnated with nickel and vanadium naphthenates according to Mitchell [14] with a nickel to vanadium ratio... 

The Figures 10.1 and 10.3 present the TPO spectra of the samples with and without metals. For the sample impregnated with 4100 ppm vanadium, it was observed the appearance of a shoulder around 680°C that translates in a 10% increase in peak C area, compared to the metal-free catalyst as illustrated in Figure 10.3. Then, the signal C located around 61TC apparently corresponds to the contaminant coke produced by the hydro-dehydrogenation properties of vanadium. 

Ammonia is adsorbed on the surface of an SCR catalyst in a diffusion limited laminar flow regime. The ammonia combines with vanadium pentoxide V2O5, a catalytic metal impregnated on the surface of the catalyst, to form a Bronsted acid site. NOx reduction takes place on this acid site to form nitrogen and water. The spent -OH site is restored to -OH via oxidation to repeat the catalytic cycle. Once the vanadium site can no longer revert back into the -1-5 oxidative state, then that site is no longer active for NO reduction. Figure 17.7 shows the catalytic cycle for the SCR reactions. 

The SCR catalyst designed for FCCU regenerator flue gas service is a homogenous monolith, typically made from 1 mm thick material. Some catalysts are extruded clays that receive a wash coat of titanium dioxide before impregnation of the vanadium and tungsten metals. Another type involves painted plates of expanded metal... 

AIPO4-5 molecular sieve (BET surface area, 299 m g ) used in this study was prepared by the method of Wilson et al. [1j. VjOg/AIPO -S samples were prepared by impregnating with aqueous solutions of ammonium vanadate after removing templating agent in the AIPO -S by calcining at 530°C. The samples were dried at 110 C for 24 h then calcined in air at 550°C for 2 h. VAPO -S was prepared from gel mixture of phosphoric acid, pseudoboehmite, vanadium pentoxide, tri-propylamine and water (1.3 PrjN x AljOj PjOj 40 HjO) by crystallization at 165°C for 3 - 7 days [7. ... 

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