Catalytic Decomposition of Toxic Chemicals over Metal-Promoted Carbon Nanotubes

摘要

Effective decomposition of toxic gaseous compounds is important for pollution control at many chemical manufacturing plants. This study explores catalytic decomposition of phosphine (PH_3) using novel metal-promoted carbon nanotubes (CNTs). The cerium-promoted Co/CNTs catalysts (CoCe/ CNTs) are synthesized by means of coimpregnation method and reduced by three different methods (H_2, KBH_4, NaH_2PO_2·H_2O/ KBH_4) The morphology, structure, and composition of the catalysts are characterized using a number of analytical instrumentations including high-resolution transmission electron microscopy, X-ray diffraction. X-ray photoelectron spectroscopy, BET surface area measurement and inductively coupled plasma. The activity of the catalysts in PH_3 decomposition reaction is measured and correlated with their surface and structural properties. The characterization results show that the CoCe/CNTs catalyst reduced by H_2 possesses small particles and is shown thermally stable in PH_3 decomposition reaction. The activities of these catalysts are compared and are shown in the following sequence: CoCe/CNTs > Co/CNTs > CoCeBP/ CNTs> CoCeB/CNTs. The difference in reduction method results in the formation of different active phases during the PH3 decomposition reaction. After a catalytic activity test only the CoP phase is formed on CoCe/CNTs and Co/CNTs catalysts, whereas muliphases CoP, Co_2P, and Co phases are formed on CoCeBP/CNTs and CoCeB/CNTs. Results show that the CoP phase is formed predominantly on the CoCe/ CNTs and Co/CNTs catalysts and is found to likely be the most active phase for this reaction. Furthermore, the CoCe/CNTs catalyst exhibits not only highest activity but also long-term stability in PH_3 decomposition reaction. When operated in a fixed-bed reactor at 360 ℃, single-pass PH_3 conversion of about 99.8% can be achieved.