• Applied Chemistry for Engineering
• /
• v.4 no.4
• /
• pp.721-730
• /
• 1993

Various catalysts of $Cu_xH_3-{_{2x}}PMo_{12}O_{40}{\cdot}_nH_2O$ with different x-values have been prepared and characterized by thermal analysis, X-ray powder diffraction, infrared spectroscopy, BET surface-area measurement, electron microscopy, and temperature programmed desorption of ammonia. The properties of these catalysts in acrolein oxidation have been investigated in a continuous-flow fixed-bed reactor. The catalysts lost their water of crystallization at about $200^{\circ}C$ and their constitutional water between 300 and $400^{\circ}C$. The Keggin structure of the catalysts was identified by infrared spectroscopy. The decomposition of Keggin anion, $(PMo_{12}O_{40})^{3-}$, was increased with the increase of substituted copper content and identifiable $MoO_3$ and $P_2O_5$ as decomposition products were observed. The conversion of acrolein decreased with the increase of x probably due to the decrease of specific surface area and of total amount of acid sites. But specific reaction rate and selectivity to acrylic acid were maximized at x=1.0, and it showed specific acid site distributions.

• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.1
• /
• pp.26-34
• /
• 2010

The electrocatalystic prperties of Pt-Co and Pt-Ni with heteropolyacids (HPAs) entrapped in covalently cross-linked sulfonated poly(ether ether ketone) (CL-SPEEK)/HPA membranes were investigated for water electrolysis. The HP As, including molybdophosphoric acid (MoPA), and tungstophosphoric acid (TPA) were both used as membrane additives and electrocatalysts. The membrane electrode assembly (MEA) was prepared by a nonequilibrium impregnation-reduction (I-R) method. $Pt(NH_3)_4Cl_2$, $NiCl_2$ and $CoCl_2$ as electrocatalytic materials and $NaBH_4$ as reducing agent were used. I order to enhance electrocatalytic activity, the catalyst layer prepared above was electrodeposited (Dep) with HP A. Surface morphologies and physico-chemical properties of MEA were investigated by means of SEM, EDX and XRD. The electrocatalytic properties of composite membranes such as the cell voltage and coulombic charge in CV were in the order of magnitude: CL-SPEEK/MoPA40 (wt%) > CL-SPEEK/TPA30 > Nafion117. In the optimum cell applications for water electrolysis, the cell voltage of Pt/CL-SPEEK-MoPA40/Pt-Co (Dep-MoPA) and Pt/CL-SPEEK-TPA30/Pt-Co (Dep-TPA) was 1.75 Vat $80^{\circ}C$ and $1\;A/cm^2$ and voltage efficiency was 87.1%. Also, the observed activity of Pt-Co (84:16 atomic ratio by EDX) is a little higher than that of Pt-Ni (86: 14). The current density peak of electrodeposited electrodes were better a little than those of unactivated electrodes based on the same membranes.