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The influence of holmium on catalytic properties of Fe or Cu-modified vermiculites

Samojeden Bogdan, Grzybek Teresa, Kowal Joanna, Szymaszek Agnieszka, Jabłońska Magdalena, Gläser Roger, Motak Monika

Physicochemical Problems of Mineral Processing

2019

Vol. 55, iss. 6

1484--1495

Natural layered clay, vermiculite, was modified and tested as catalyst for the selective catalytic reduction of NOx with ammonia (NH3-SCR). Its modification included the application of the blowing agent (azodicarbonamide), acid treatment and pillaring with Al2O3. Active phase (transition metals: Cu or Fe) was introduced via impregnation. The obtained materials were characterized by N2 sorption (texture), XRD (structure), DR-UV-Vis (oxidation state and aggregation of the active phase), H2-TPR (reducibility of the active phase), in situ DRIFTS (types of adsorbed species due to contact of the sample NH3) and NH3-TPD (type/strength of the acidic sites). The initial modification procedures (treatment with azodicarboamide) resulted in the increase of specific surface area of vermiculite. The introduction of transition metal ions provided a significant amount of acidic sites. The promoting impact of holmium was confirmed by the increased strength of the sites. The highest catalytic activity was exhibited by the sample Fe-containing vermiculite and doped with Ho.

Post-recoil thermal annealing study of 177Lu, 169Yb, 175Yb, 166Ho and 153Sm in different organometallic compounds

Nassan L., Achkar B., Yassine T.

Nukleonika

2011

Vol. 56, No. 2

185-190

Post-recoil thermal annealing study at different temperatures for different intervals of time of the recoiled isotopes 169Yb, 175Yb, 177Lu, 166Ho, and 153Sm resulting from the nuclear reactions 168Yb(n,gamma)169Yb, 174Yb(n,gamma)175Yb and 176Yb(n,gamma)177Yb → 177Lu, 165Ho(n,gamma)166Ho, 152Sm(n,gamma)153Sm, respectively in different organometallic compounds Yb(OCC(CH3)3CHCOC(CH3)3)3, Ho(OCC(CH3)3CHCOC(CH3)3)3, (C5H5)3Ho, and (C5H5)3Sm were carried out. The thermal annealing behaviors of 177Lu, 169Yb, 175Yb, 166Ho, and 153Sm were found to be different in the compounds under investigation. The differences in the patterns of the obtained isothermal curves were discussed. Depending on the post- -recoil thermal annealing manner the reactions taking place during thermal annealing were suggested.

Investigation of Heteropoly Niobotungstolanthanidate Ions Equilibria in the Aqueous Solutions at Different Ionic Strengths

Rozantsev G., Radio S., Kozlova T.

Polish Journal of Chemistry

2006

Vol. 80, nr 2

235-245

The condensation process in the system: Ln3+-H3Nb6O19 5 -WO4 2 -OH-(H+)-H2O (Ln = Ho, Nd; ni(Nb):ni(W) = 9:1) has been investigated. According to the results of potentiometric titrations, the model of the condensation process has been proposed. Diagrams of mixed heteropoly niobotungstolanthanidate anions (HPNTLA) distribution within an intervals ZH+ = [ni(H+ )]/[ni(W) + ni(Nb)] = 0.00÷0.30 and ZOH- = [_(OH-)]/[ni(W) + ni(Nb)] = 0.00÷0.36 have been drawn. It has been shown that at Z H+ > 0.30 there occurs a destruction of heteropolyanions (HPA). Concentration and thermodynamic constants of HPA formation have been determined. Existence of HPNTLA has been confirmed by chemical and IR-spectroscopic analyses of Tl6H4[HoNb9W(OH)8O28]ni4.0H2O, which was isolated from a solution with Z H+ = 0.08. It has also been shown, that HPNTLAkeeps the ratio of Nb:W = 9:1 within the entire interval ZOH-. The main destruction phases of Tl6H4[HoNb9W(OH)8O28]x4.0H2O have been determined by X-ray powder diffraction analysis.