Oxygen bleaching of kraft pulp catalysed by Mn(III)-substituted polyoxometalates

Perovskite-type Oxide LaMnO3: An Efficient and Recyclable Heterogeneous Catalyst for the Wet Aerobic Oxidation of Lignin to Aromatic Aldehydes

“…1. in the presence of peroxidase enzymes [3]. Aromatic aldehydes such as vanillin, syringaldehyde and p-hydroxybenzaldehyde as shown in Fig.…”

“…Moreover, Mn(II) iron solution [16], Mn(III)-substituted polyoxometalates [3] and Mn(IV) complex [17,18] are known to show interesting activities in the oxygen delignification of the bleaching process of pulps. On the other hand, it is well known that ABO 3 perovskite-type oxides, including LaMnO 3 , show high activity and stability in the hydrocarbon catalytic oxidation process, which is a promising alternative to noble metal catalysts for the wet process of hydrocarbon catalytic oxidation [19][20][21][22][23].…”

Transition metal substituted polyoxotungstates for the oxygen delignification of kraft pulp

“…The experimental conditions for the catalytic oxygen delignification (pulp consistency, catalyst concentration, pH, p 0 (O 2 ), temperature and time of reaction) were selected based on results previously obtained with mono-substituted Keggin-type anions XW 11 Mn III (X = P, Si, B) [6]. When necessary, the delignification conditions were adapted for the application of each particular catalyst.…”

“…1a), [PMo 12Àn V n -O 40 ] (3+n)À (n = [1][2][3][4][5], and a-[XW 11 Mn III (H 2 O)O 39 ] nÀ (X = P, B, Si) have been tested previously as catalysts for the oxygen delignification of kraft pulp [3][4][5][6]. Particularly, a www.elsevier.com/locate/apcata Applied Catalysis A: General 295 (2005) 134-141 highly selective delignification process was developed using a-[SiW 11 Mn III (H 2 O)O 39 ] 5À (or SiW 11 Mn III for short) [6]. The feasibility of POM-promoted pulp oxygen bleaching was recently confirmed in semi-industrial scale experiments [7].…”

“…The principles of the aerobic oxidative catalytic delignification/bleaching with POMs have been widely discussed previously [3][4][5][6][7]. Shortly, the main catalytic principle can be formulated as follows: POM having a kinetic barrier to lignin oxidation lower than that of dioxygen, oxidizes the lignin, and then, the reduced form of POM is re-oxidized by O 2 at the same stage.…”