Flexible hierarchical Pd/SiO₂-TiO₂ nanofibrous catalytic membrane for complete and continuous reduction of p-nitrophenol

Abstract

Flexible and hierarchical nanostructured Pd/SiO 2 -TiO 2 nanofibrous catalytic membranes were fabricated via combining electrospinning technique and a two-step hydrothermal method. The size and distribution of TiO 2 nanorods immobilised on SiO 2 nanofibrous membranes can be regulated via adjusting the dosage of TiCl 3 solution in the first step hydrothermal process. When using an optimal TiCl 3 solution dosage of 0.2 mL, a hierarchical structured Pd/SiO 2 -TiO 2 -0.2 nanofibrous catalytic membrane with uniformly dense TiO 2 nanorods loaded on SiO 2 nanofibers is obtained, and still shows good tensile strength and flexibility. The catalytic activity of Pd/SiO 2 -TiO 2 -0.2 increases 5 times as compared to Pd/SiO 2 -TiO 2 -0 in the reduction of p-nitrophenol (PNP) to p-aminophenol (PAP). The modification with TiO 2 nanorods can provide more surface areas for loading the Pd nanoparticles, thereby increased active sites. The three-dimensional open-cell network stacked and assembled by thousands of SiO 2 nanofibers and TiO 2 nanorods enhances the contact between the reactants and Pd nanoparticles. Both aspects contribute the superior catalytic activity of Pd/SiO 2 -TiO 2 -0.2. Furthermore, a continuous and complete conversion of PNP to PAP can be stably operated over 240 min in a gravity-driven catalytic membrane reactor constructed by Pd/SiO 2 -TiO 2 -0.2.

ZIF-Derived Co/Zn Bimetallic Catalytic Membrane with Abundant CNTs for Highly Efficient Reduction of p-Nitrophenol

“…The turnover frequency (TOF) values of the as-fabricated catalytic membranes were calculated and compared (Table ). ,,− Co0.2Zn0.4–920@CM has the highest TOF value among the as-fabricated catalytic membranes, which is about 7 times that of Co0.6Zn0–920@CM and 2.5 times that of Co0.2Zn0.4–770@CM. Meanwhile, Co0.2Zn0.4–920@CM has a high TOF value as compared to the reported catalysts at a lower molar ratio of NaBH 4 to PNP and a higher PNP concentration.…”

“…As compared to the powdered catalysts, the catalytic membranes have many advantages. On one hand, the catalytic membranes avoid the separation of the powdered catalysts from the reaction system, decreasing the cost of investment and making the production process simple. , On the other hand, continuous production process can be easily achieved in the catalytic membrane reactors, increasing the capacity of the reactors and reducing the discharge of pollutants. , Moreover, the reactants can be forced to pass through the catalytic membranes, eliminating the influence of the mass-transfer due to pore diffusion, thereby improving the catalytic performance . For example, Zhu et al applied UiO-66-NH 2 to modify the SiO 2 nanofibrous membrane and then loaded Pd NPs to achieve a catalytic membrane .…”

Porous Membrane Reactors for Liquid-Phase Heterogeneous Catalysis

“…The catalytic activity of the catalytic membrane obtained by calcination under a mixed atmosphere of H 2 and Ar (H 2 /Ar = 1:9 in volume) improved by a factor of 1.9, compared to that without TiO 2 modification and calcination, and 100% conversion of p -nitrophenol to p -aminophenol could be achieved. Pan et al fabricated a flexible and hierarchical nanostructured Pd/SiO 2 –TiO 2 nanofibrous catalytic membranes via combining electrospinning and a two-step hydrothermal method. The modification with TiO 2 nanorods could provide more surface areas for loading the Pd nanoparticles (from 4.05 mg m –2 to 389.94 mg m –2 ), thereby increasing the number of active sites.…”

High-Symmetry Co/Ni Triazine Polycarboxylate Diverse Frameworks Constructed by Mx(COO)y Building Blocks: Characterization and Catalytic Performance Evaluation of p-Nitrophenol

“…p -Nitrophenol (PNP) is one of the most common pollutants in wastewater from the chemical industry. Its frequent use in industry not only tends to destroy the ecosystem but also poses a risks to human health. − Considering the great harm caused by PNP to environmental pollution and human health, researchers have used various catalysts to catalyze the reduction of PNP to p -aminophenol (PAP). − PAP is an important organic chemical raw material and pharmaceutical intermediate, which can be used to prepare a variety of chemical products and can be used as anesthesia and analgesia as well as antipyretic drugs. − At present, catalytic hydrogenation is the major method for the catalytic reduction of PNP. Among them, the use of noble-metal catalysts to catalyze PNP has been reported in many literature reports. − In 2016, Sun et al synthesized Au/ZnO@ZIF-8 nanocomposite, which exhibited high catalytic activity for the reduction of PNP .…”