Effect of cesium content on the structure and catalytic performances of heteropoly compounds in one-step synthesis of methylmethacrylate from methacrolein

Abstract

Keggin-type heteropoly compounds (HPCs) H 3.2−x Cs x Cu 0.25 As 0.1 PMo 11 VO 40 (x, 0-2.5) were used as catalysts for coupling reaction of methylmethacrylate (MMA) from methacrolein (MAL) in this study. And the catalytic performance of the HPCs was investigated in the oxidation-esterification coupling reaction. Moreover, the HPCs were characterized by NH 3 -TPD, TG-pyridine-adsorption/desorption, N 2 -adsorption/desorption, ICP, TG-DSC, FT-IR, XRD and TPR. These reactive results have been correlated to the acidity, surface area and reducibility. With the increasing of Cs content, surface area of the HPCs increased, while the acidity and reducibility decreased. Difference of the quantity of acid sites originated from the hydration protons being substituted by Cs + . Effects of Cs + content on the reducibility of the HPCs indicated that Cs + changed the structural stability of V as coordinating atoms and the proportion of the different reducible states of Mo 6+ .

Effect of vanadyl species in Keggin-type heteropoly catalysts in selective oxidation of methacrolein to methacrylic acid

“…1, four main vibration bands emerged around 1064, 961, 874, and 780 cm À1 before calcination. These vibration bands can be assigned to the PAO, Mo@O d , MoAO b AMo, and MoAO c AMo bands, respectively, which are characteristic of POMs with a Keggin structure [20]. Compared with the MoAO c AMo bands of HPA, those of HPAV, VHPA, and HVOPA were obviously red-shifted (from 780 to 794 cm À1 ) by the interaction of vanadyl species with the Keggin structure [21].…”

Cs(NH4)xH3–xPMo11VO40 Catalyzed Selective Oxidation of Methacrolein to Methacrylic Acid: Effects of NH4+ on the Structure and Catalytic Activity

“…Methacrylic acid (MAA), as an important chemical intermediate for synthesis of methyl methacrylate (MMA), was normally synthesized by selective oxidation of methacrolein (MAL) over Keggin-type polyoxometalates catalysts. − Among those screened, the cesium salts of 11-phosphomolybdovanadyl acids behaved with a good catalytic efficiency in the selective oxidation of MAL to MAA. − In recent years, ammonium-modified polyoxometalates received increasing attention − because they exhibited enhanced catalytic performance in the production of MAA . For instances, Otero Areán and Marosi found two extra-framework molybdenum ions coexisted in Cs x (NH 4 ) y H z PMo 12 O 40 , offering the conversion of 50.7% from MAL to MAA .…”

CsCu0.1H2.9PMo11VO40 catalyst synthesized via a high shear mixer facilitated precipitation method for selective oxidation of methacrolein to methacrylic acid

“…These absorption bands can be assigned to P–O stretching, terminal MoO stretching (MoO d ), Mo–O–Mo asymmetric stretching of a corner (Mo–O b –Mo), and edge (Mo–O c –Mo)-sharing bridged oxygens, respectively. 41 The emergence of a band at 1034 cm −1 in the spectra of CP-HSM was attributable to the V–O stretching bands of VO 2+ in the secondary structure. 42,43 Nevertheless, the band was not found in the spectra of CP.…”