Calcium Salts of Tungstophoric Acid Supported on Silica as Novel Catalysts for Tetrahydrofuran Polymerization

Abstract

The 12-tungstophoric acid (HPW) and its calcium salts Ca x/2 H 3-x PW 12 O 4 with the calcium content in the range 0 \ x \ 3 supported on silica were synthesized, and their catalytic properties were also studied in the polymerization of tetrahydrofuran under mild conditions. These catalysts were characterized by isothermal nitrogen adsorption/desorption, infrared spectroscopy, n-butylamine electrometric titration, and thermal analysis. The calcium salts presented strong acidity and high catalytic performance. When x = 2.0, the supported calcium salt CaH-PW 12 O 40 /SiO 2 calcined at 300°C gave the highest catalytic activity. However, a poor catalytic activity was only obtained over the Ca 1.5 PW 12 O 40 /SiO 2 catalyst substituting all protons of phosphotungstic acid, which was due to its weakest acidity. The CaHPW 12 O 40 /SiO 2 sample showed better reusability than normal HPW/SiO 2 catalyst, and reacted as a recyclable and effective catalyst for tetrahydrofuran polymerization.

Towards sustainable polymer chemistry with homogeneous metal-based catalysts

“…194 Since calcium is the most abundant element of the alkaline earth metals, numerous homogeneous catalysts exist. For example, a wide variety of calcium catalysts facilitate the ring-opening polymerization of lactide, 195,196 ε-caprolactone, 197 tetrahydrofuran, 198 and trimethylene carbonate (TMC). 172,199 In addition, certain catalysts, such as those depicted in Fig.…”

Effect of Silver Content on Catalytic Performances of SiO₂-Supported Silver Tungstophoric Acid for the Synthesis of Polytetrahydrofuran

“…18 The yield of reaction was measured with the following formula: Yield=m(PTMEG)/[m(THF) + m(ECH)] × 100% , THF is tetrahydrofuran. The viscosity-averaged molecular weight (Mη) of polytetrahydrofuran was calculated according to the formulas in the reference: 23…”