Yao Ning,Yuqi Yang,Dongming Shan,Shuxing Mei,Yibai Yan,Linjie Ding,Ying Zhang
Ethylene oligomerization plays an important role in industrial production. However, when taking the traditional non-metallocene catalysts and MOF catalysts for ethylene oligomerization, they typically require methylaluminoxane (MAO), aluminum alkyl, and other cocatalysts, which is neither environmentally friendly nor helpful in reducing production costs. Here, three sulfonic acid-modified MOFs (SA/MIL-101(Cr), UiO-66-NS and MIL-101(Cr)-NS) were prepared and used as catalysts for ethylene oligomerization at room temperature without using any cocatalysts. All of them exhibited excellent catalytic performances (e.g., 10SA/MIL-101(Cr), 21 953 g molCr−1 h−1, with C8 selectivity greater than 70.32%), and their oligomerization activity increased by almost tenfold compared to unmodified MOFs. The presence of Lewis acid (L acid) and Brønsted acid (B acid) sites in modified MOFs is the key to improved performances. In particular, the presence of B acid weakens the role of metal clusters and ligands in MOFs, making it easier for metal centers to bind to ethylene molecules for further oligomerization. This work first demonstrates that bifunctional MOF catalysts can catalyze ethylene tetramerization under mild conditions without cocatalysts.
The vanadium redox flow battery (VRFB) is a highly favorable tool for storing renewable energy, and the catalytic activity of electrode materials is crucial for its development. Taurine-functionalized carbon nanotubes (CNTs) were prepared with the aim of augmenting the redox process of vanadium ions and enhancing the efficiency of the VRFB. Sulfonated CNTs were synthesized through a simple modification process in a taurine solution and used as electrocatalysts for redox reactions involving VO2+/VO2+and V2+/V3+. The SO3H-CNTs modified at 60 °C for 2 h exhibit the best electrocatalytic activity, showing higher redox peak current values compared to pristine carboxylated CNTs (COOH-CNTs). Sulfonic acid groups added to the surface of CNTs increase active sites for redox reactions and act as carriers for mass transfer and bridges for charge transfer, accelerating the rate of the electrode reactions. A battery consisting of SO3H-CNTs as catalysts demonstrates the outstanding charge–discharge performance at a current density of 300 mA∙cm−2. This configuration displays voltage and energy efficiencies of 81.46% and 78.83%, respectively, representing enhancements of 6.15% and 6.12% compared to that equipped with conventional graphite felts (75.31%, 72.71%). This study illustrates that taurine-functionalized carbon nanotubes serve as an efficient and promising catalyst for both the anode and cathode, leading to the improved performance of the VRFB.
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