Promising Isotope Effect in Pd77Ag23 for Hydrogen Separation

Pd–Ag alloys are largely used as hydrogen separation membranes and, as a consequence, the Pd–Ag–H system has been intensively studied. On the contrary, fewer information is available for the Pd–Ag–D system; thus, the aim of this work is to improve the knowledge of the isotope effect on the commercial Pd77Ag23 alloy, especially for temperature above 200 °C. In particular, deuterium absorption measurements are carried out in the Pd77Ag23 alloy in the temperature range between 79 and 400 °C and in the pressure range between 10−2 and 16 bar. In this exploited pressure (p) and composition (c) range, above 300 °C the pc isotherms display the typical shape of materials where only a solid solution of deuterium is present while at lower temperatures these curves seem to be better described by the coexistence of a solid solution and a deuteride in a large composition range. The obtained results are compared and discussed with the ones previously measured with the lightest hydrogen isotope. Such a comparison shows that the Pd77Ag23 alloy exhibits a clear inverse isotope effect, as the equilibrium pressure of the Pd–Ag–D system is higher than in Pd–Ag–H by a factor of ≈2 and the solubility of deuterium is about one half of that of hydrogen. In addition, the absorption measurements were used to assess the deuteration enthalpy that below 300 °C is ΔHdeut = 31.9 ± 0.3 kJ/mol, while for temperatures higher than 300 °C, ΔHdeut increases to 43 ± 1 kJ/mol. Additionally, in this case a comparison with the lighter isotope is given and both deuteration enthalpy values result lower than those reported for hydrogenation. The results described in this paper are of practical interest for applications operating above 200 °C, such as membranes or packing column, in which Pd77Ag23 has to interact with a gas stream containing both hydrogen isotopes.

Modeling Of Absorption Process In Packing Column Operating In The Emulsification Mode

A new approach to the mathematical modeling of packed absorption columns operating in the emulsification mode, which makes it possible to estimate the actual surface of the contact phase of the mass transfer products is presented. Equations for calculating the average diameter of the gas phase bubbles, the thickness of the liquid film between the bubbles in the packed absorption mass-exchange column operating in the emulsification mode are derived on the basis of the equality of the formation energy of the phase interface and the base of their overcoming the hydraulic resistance. A comparison of technological and geometric parameters of a typical packed absorption column with Raschig rings and a column with S-Aisi316Tiε-0.82 packing material based on the metalworked wastes.

The effect of increasing CO2concentration and flow rate on amine still performance in meeting gas sale specifications

The main purpose of this study is to examine the effect of increasing CO2removal and flow rate on performance of an amine still. The amine still is located in Field X in South East Sumatra at a new gas well producing gases with a rich CO2content. The still uses activated MDEA as the amine and has an IMTP 40-type packing column. Two film and desorption equilibrium curve theories were employed to analyse the amine still design conditions. Design equations were utilized to find the slope of the equilibrium curve. A slope of the equilibrium curve of 45° in the amine still is obtained in this study. The maximum liquid CO2composition of the amine still feedstock (xo) which can be separated to produce lean amine according to the specification design flow rate is 0.0307. The total flow rate of CO2-rich amine at xo= 0.029 is 761,157.6 kg/hour; the total flow rate of CO2-rich amine atxo= 0.0295 is 628,861.1 kg/hour; the total flow rate of CO2- rich amine at xo= 0.03 is 513,962.6 kg/hour; and the total flow rate of CO2-rich amine at xo= 0.0305 is 409,575.3 kg/hour.

Research on Purifying Hypocrellin by Molecularly Imprinted Solid Phase Extraction (MISPE)

Separation and purification of hypocrellin A (HA) and hypocrellin B (HB) are conducted for extracted concentrated solution of hypocrellin through dry packing of molecularly imprinted polymers (MIPs) of hypocrellin A and B and preparative solid phase extraction column. The result shows that the optimum packing column combination for mixed adsorption is H5 (i.e. MIP of hypocrellin A and B are respectively 10.5g and 4.5g), and that the elution sequence is hypocrellin A elution first and then hypocrellin B elution next after the eluent is changed.