PDF Publication Title:
Text from PDF Page: 023
Fig. 10. Determination of the enthalpy and entropy of adsorption for H2 in Na- ZSM-5 using variable-temperature infra-red measurements. http://www.rsc.org/ejga/CS/2005/b407049f-ga.gif Reproduced with permission from the Royal Society of Chemistry @2005. range corresponds to Brønsted acid O2H groups located within large cavities while the lower range represents O2H groups vibrating in smaller voids. Adsorbed molecules may be denied adsorption in the smaller cavities (formed by rings of lower than eight members). When N2 is adsorbed into H-ZSM-5, the band at 3616 cm 1 from Brønsted acid sites begins to decrease in intensity while the band from silanols at 3747 cm 1 is barely affected. However, a new broad band from hydrogen-bonded OH2N2 complexes grows-in at around 3500 cm 1, simultaneously with the activation of the N2N stretching vibration at 2331 cm 1. From the temperature dependence of these band intensities, values58 of DH 1⁄4 19:7ð+0:5Þ kJ mol 1 and DS 1⁄4 125ð+0:5Þ J mol 1yK were obtained for the enthalpy and entropy of adsorption for N2 on H-ZSM-5 which is close to the heat of adsorption of 19 kJ mol 1 deduced from microcalorimetry measurements59. When molecular hydrogen is adsorbed in alkali-metal cation exchanged zeolites at 77K, the main adsorption band is observed in the region 4070– 4100cm1, from the fundamental H2H stretching mode of the adsorbed H2 molecule. Cations and their neighbouring framework oxygen atoms provide centres for adsorption of H2 for which the vibrational frequency is reduced from the 4136 cm 1 Raman-active band measured for the free molecule in the gas phase. Values of DH 1⁄4 10:3ð+0:5ÞkJ mol 1 and DS 1⁄4 121ð+10ÞJ mol 1 K 1 were obtained for H2 adsorbed in Na-HSM-5 (Figure 10) 60. The enthalpy of adsorption may be compared with the enthalpy for the liquefaction of hydrogen gas, which at a temperature of 20.45 K www.scienceprogress.co.uk Properties and applications of zeolites 245 Black plate (245,1)PDF Image | Properties and applications of zeolites
PDF Search Title:
Properties and applications of zeolitesOriginal File Name Searched:
003685010x12800828155007.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |