Large and Highly Selective and Permeable CHA Zeolite Membranes

Large (100 cm2 membrane area) tubular chabazite (CHA) zeolite membranes (450 nm thick) were experimentally evaluated for the separation of CO2/CH4 in an industrial laboratory. An industrially relevant feed flow rate of 250 Ndm3/min was used. The feed pressure and temperature were varied in the ranges of 5–18 bar and 292–318 K, respectively. For a CO2/CH4 feed with a molar ratio of 1:1, the experimental CO2/CH4 selectivity was high at 205, and the CO2 permeance arrived at 52 × 10–7 mol/(m2·s·Pa) at 5 bar and 292 K. As far as we know, there is no report in the literature on large CHA membranes with such high permeability and selectivity. A high CO2/CH4 selectivity was also observed for a 1:4 CO2/CH4 feed. However, as indicated by mathematical modeling, concentration polarization was still an issue for membrane performance, especially at high operating pressures, even though the flow rate of the feed was relatively high. Without concentration polarization, the theoretical CO2/CH4 selectivity was 41% higher than the experimental value for a 1:1 CO2/CH4 feed at 18 bar. The corresponding CO2 permeance without concentration polarization was 23% higher than the experimentally observed value, reaching 34 × 10–7 mol/(m2·s·Pa). CHA membrane processes for the removal of CO2 from CH4 were designed, and the electricity consumption and module cost of the process were also estimated. All of the results in this study indicate a great potential of the large CHA membranes for biogas and natural gas upgrading; however, concentration polarization should be minimized in industrial processes

Ternary Adsorption of Methane, Water, and Carbon Dioxide in Zeolite Na-ZSM‑5 Studied Using in Situ ATR-FTIR Spectroscopy

The main component in biogas and natural gas is methane, but these gases also contain water and carbon dioxide that often have to be removed in order to increase the calorific value of the gas. Membrane and adsorbent-based technologies using zeolites are interesting alternatives for efficient separation of these components. To develop efficient processes, it is essential to know the adsorption properties of the zeolite. In the present work, adsorption of methane, carbon dioxide, and water from ternary mixtures in high silica zeolite Na-ZSM-5 was studied using in situ ATR (attenuated total reflection)–FTIR (Fourier transform infrared) spectroscopy. Adsorbed concentrations were extracted from the infrared spectra, and the obtained loadings were compared to values predicted by the ideal adsorbed solution theory (IAST). The IAST could not fully capture the adsorption behavior of this ternary mixture, indicating that the adsorbed phase is not behaving as an ideal mixture. The CO₂/CH₄ adsorption selectivities determined for the ternary mixtures were compared to selectivities determined for binary mixtures in our previous work, indicating that the presence of water slightly improves the CO₂/CH₄ adsorption selectivity at lower temperatures. Further, the results show that water and carbon dioxide are adsorbed preferentially over methane in high silica zeolite Na-ZSM-5

Individual mechanically ventilated patients with <i>community-acquired pneumonia</i> with positive result obtained with either IRIDICA PCR/electrospray ionization–mass spectrometry (PCR/ESI-MS) or culture on bronchoalveolar lavage (BAL).

<p>Support for positive PCR/ESI-MS results is indicated in bold.</p

Flow shart of the study patients.

<p>ICU, intensive care unit; BAL, bronchoalveolar lavage.</p

Combined results of IRIDICA PCR/electrospray ioization-mass spectrometry (PCR/ESI-MS) and culture on bronchoalveolar lavage (BAL) for individual pathogens (with > 1 positive result), in mechanically ventilated patients with and without pneumonia.

<p>Combined results of IRIDICA PCR/electrospray ioization-mass spectrometry (PCR/ESI-MS) and culture on bronchoalveolar lavage (BAL) for individual pathogens (with > 1 positive result), in mechanically ventilated patients with and without pneumonia.</p

Individual mechanically ventilated patients without pneumonia with positive result obtained with either IRIDICA PCR/electrospray ionization–mass spectrometry (PCR/ESI-MS) or culture on bronchoalveolar lavage (BAL).

<p>Support for positive PCR/ESI-MS results is indicated in bold.</p

Clinical and microbiological factors and their association with nasopharyngeal pneumococcal density.

<p>^a Solid tumor, blood malignancy, liver disease, renal disease, chronic obstructive pulmonary disease, heart disease, stroke, diabetes.</p><p>^b Serotypes 3, 6B, 11A, 12F, 19A, 19F, 23F, and 35B.</p><p>Univariate analysis on 57 patients if not otherwise stated.</p

Characteristics of patients with community-acquired pneumonia with pneumococcal DNA detected and not detected in nasopharyngeal (NP) aspirate.

<p>Data are presented as numbers (%), unless otherwise indicated.</p><p>^a<i>Streptococcus pneumoniae</i> detected by blood culture and/or culture of respiratory secretions and/or urinary antigen test.</p><p>^b Solid tumor, blood malignancy, liver disease, renal disease, chronic obstructive pulmonary disease, heart disease, stroke, diabetes.</p><p>Characteristics of patients with community-acquired pneumonia with pneumococcal DNA detected and not detected in nasopharyngeal (NP) aspirate.</p

Flow chart of the study population with and without nasopharyngeal aspirate tested with PCR for pneumococcal DNA.

<p>Flow chart of the study population with and without nasopharyngeal aspirate tested with PCR for pneumococcal DNA.</p

Characteristics of included patients.

<p>All patients were mechanically ventilated.</p