Preparation of monosodium 2-sulfoterephthalate to make a MIL-101(Cr)–SO3H catalyst

Abstract

MIL-101(Cr)-SO₃H has excellent thermal and chemical stabilities, making it an ideal porous acid catalyst for many organic reactions and petrochemical industries. However, there are some disadvantages such as the fact that it is not easy to mass produce crystalline MIL-101(Cr)-SO₃H and it is time-consuming to purchase the starting organic ligand of 2-sulfoterephthalate monosodium (sTA-Na). In this study, readily available p-xylene (1,4-dimethylbenzene) was used as the raw material for the lab-synthesis of sTA-Na. Some optimal conditions were studied and established to obtain a maximum sTA-Na yield of ∼75%. The prepared sTA-Na was characterized by FT-IR, PXRD, FE-SEM, NMR and MS spectroscopies, showing that its functional groups, molecular structure, and molecular weight are the same as those of the commercial counterpart from TCI company; however, their particle shapes and crystal phases are different. Then, the MIL-101(Cr)-SO₃H powder was prepared from the lab-synthesized sTA-Na and used as a catalyst in ethylene dichloride (EDC) cracking to produce a vinyl chloride monomer (VCM). The catalytic activity test in the EDC cracking showed that the reaction temperature can be lowered to 255 °C from 550 °C, while the percentage conversion (∼75%) and the selectivity (99.8%) remain unchanged or even better than those in current industrial processes, indicating that MIL-101(Cr)-SO₃H is a promising catalyst applied as an energy efficiency technology in the EDC cracking to produce VCM.