Study of Interactions between Ion-Exchanged Chromium and Impregnated Vanadium in USY Zeolite Material

Abstract

The steam treatment effect on the structure stability and acidity of ultrastable Y (USY) and Cr(III)-exchanged USY zeolites is investigated in the presence and absence of impregnated vanadium at 1000 up to 4000 ppm concentrations. Under steam-treatment conditions and in the presence of vanadium, the obtained results give evidence of the complete structure breakdown of an USY zeolite sample, which is nearly proportional to the percent dealumination; however, the structure breakdown of a Cr(III)-exchanged USY zeolite sample is limited even though the percent dealumination is still high. In addition, it is proved that the impregnated vanadium attacks selectively the strong acid sites, i.e., removes isolated framework Al atoms; however, although this action comes to completeness, the zeolite structure of the Cr(III)-exchanged USY sample is strong enough to keep its crystallinity at a high percentage. Finally, the acidity measurements give evidence that the Cr(III)-exchanged USY zeolite possesses medium strength acid sites that are absent in the pure USY zeolite material, which suggests that Cr may isomorphously replace Al of the zeolitic framework structure; these sites have vanished in samples with high vanadium content after steam treatment.

Role of nickel on vanadium poisoned FCC catalyst: A study of physiochemical properties

“…Above this amount, there is absolute loss of crystallinity (below detection limit), leading to excessive or complete zeolite structure collapse. This result disagrees with the report of Tsiatouras and Evmiridis [35] , in which the authors reported a total framework breakdown of USY zeolite at vanadium concentration of 40 0 0 mg/kg. However, the results are in close agreement with those obtained by Yang et al [20] , where absolute REY zeolite structure breakdown was observed when vanadium poison was up to 10,0 0 0 ppm (mg/kg) in the catalyst.…”

“…The degree of dealumination can be obtained as the difference between the metal free and metal contaminated samples according to Tsiatouras and Evmiridis [35] .…”

“…The most acceptable mechanism of vanadium poisoning of FCC catalyst involves reaction of V 2 O 5 with steam to form mobile vanadic acid (H 3 VO 4 or H 4 V 2 O 7 ) under regenerator conditions and subsequent action of this acid on the catalyst framework aluminum (Al) to form aluminum vanadate (AlVO 4 ) solid solution, which decomposes to continue acid leaching of the framework in a catalytic fashion, leading to dealumination, structure collapse and acid site losses [18,35] . From the experimental data given above, the presence of nickel in the catalyst does not cause any significant catalyst structure collapse and loss of active sites.…”

Synthesis of Uniform Mesoporous Zeolite ZSM-5 Catalyst for Friedel-Crafts Acylation

“…The high-temperature peak was attributed to the desorption of ammonia from strong Brønsted and Lewis acidic sites [30]. Furthermore, the low-temperature peak was attributed to ammonia weakly held or physically adsorbed on the zeolite, which might be due to the desorption of weakly adsorbed NH 3 on weak acidic or non-acidic sites [31], the weak Brønsted acidic sites [32], the Lewis acidic sites [33]; or the silanol groups [30]. The NH 3 -TPD results confirmed that the untreated zeolite catalyst possesses low acidic properties in comparison with the treated zeolite catalysts.…”

Location and Surface Species of Fluid Catalytic Cracking Catalyst Contaminants: Implications for Alleviating Catalyst Deactivation

“…The formation of nickel aluminate as a result of the interaction of nickel with alumina is widely recognized, while the formation of aluminum vanadate is under debate . Some researchers hold that AlVO 4 forms as a solid solution, which is transient during the lifetime of the FCC catalyst in the regenerator and is responsible for hydrolysis of Al atoms, leading to vanadium deactivation of the catalyst. , Using the V 51 MAS NMR technique, we detected the formation of orthovanadate (VO 4 3– ) in our previous study . Also, Kanervo et al observed two peaks on the TPR profile of alumina-supported vanadium catalyst (>5 wt % V) at greater than 800 °C.…”