CO2 Capture from Flue Gas Based on Tetra-n-butylammonium Fluoride Hydrates at Near Ambient Temperature.

Semiclathrate hydrates of tetra-n-butylammonium fluoride (TBAF) are potential CO2 capture media because they can capture CO2 at near ambient temperature under moderate pressure such as below 1 MPa. In addition to other semiclathrate hydrates, CO2 capture properties of TBAF hydrates may vary with formation conditions such as aqueous composition and pressure because of their complex hydrate structures. In this study, we investigated CO2 capture properties of TBAF hydrates for simulated flue gas, that is, CO2 + N2 gas, by the gas separation test with three different parameters for each pressure and aqueous composition of TBAF in mass fraction (w TBAF). The CO2 capture amount in TBAF hydrates with w TBAF = 0.10 was smaller than that obtained with w TBAF = 0.20 and 0.30. The results found that gas pressure greatly changed the CO2 capture amount in TBAF hydrates, and the aqueous composition highly affected CO2 selectivity. The crystal morphology and single-crystal structure analyses suggested that polymorphism of TBAF hydrates with congruent aqueous solution may lower both the CO2 capture amount and selectivity. Our present results proposed that an aqueous solution with w TBAF = 0.20 is advantageous for the CO2 capture from flue gas compared to near congruent solutions of TBAF hydrates (w TBAF = 0.30) and dilute solution (w TBAF = 0.10).

Structure-driven CO2 selectivity and gas capacity of ionic clathrate hydrates.

Ionic clathrate hydrates can selectively capture small gas molecules such as CO2, N2, CH4 and H2. We investigated CO2 + N2 mixed gas separation properties of ionic clathrate hydrates formed with tetra-n-butylammonium bromide (TBAB), tetra-n-butylammonium chloride (TBAC), tetra-n-butylphosphonium bromide (TBPB) and tetra-n-butylphosphonium chloride (TBPC). The results showed that CO2 selectivity of TBAC hydrates was remarkably higher than those of the other hydrates despite less gas capacity of TBAC hydrates. The TBAB hydrates also showed irregularly high CO2 selectivity at a low pressure. X-ray diffraction and Raman spectroscopic analyses clarified that TBAC stably formed the tetragonal hydrate structure, and TBPB and TBPC formed the orthorhombic hydrate structure. The TBAB hydrates showed polymorphic phases which may consist of the both orthorhombic and tetragonal hydrate structures. These results showed that the tetragonal hydrate captured CO2 more efficiently than the orthorhombic hydrate, while the orthorhombic hydrate has the largest gas capacity among the basic four structures of ionic clathrate hydrates. The present study suggests new potential for improving gas capacity and selectivity of ionic clathrate hydrates by choosing suitable ionic guest substances for guest gas components.

Epidural blood patch therapy for chronic whiplash-associated disorder.

BACKGROUND: Despite the absence of objective neurological deficits, patients with chronic whiplash-associated disorder (WAD) complain of symptoms such as headache, dizziness, and nausea. These symptoms are also often experienced by patients with cerebrospinal fluid (CSF) leak. It was recently reported that radioisotope (RI) cisternography is useful in the diagnosis of intracranial hypotension due to CSF leak. We investigated the relation between chronic WAD and CSF leak by RI cisternography and evaluated whether epidural blood patch (EBP) administration is effective in the treatment of chronic WAD. METHODS: We studied 66 patients with chronic WAD with symptoms lasting longer than 3 mo. All patients underwent RI cisternography to determine the presence of CSF leak. In patients in whom CSF leak was identified, EBP was administered. Symptoms were assessed before, 1 wk after, and 6 mo after EBP. Work status was also assessed and follow-up RI cisternography was performed. RESULTS: Of the 66 patients, 37 showed CSF leak, and 36 of these patients received EBP 2.2 +/- 0.7 times. The mean duration of symptoms was 33 mo. One week after EBP, the percentage of patients with symptoms was decreased significantly compared with that before EBP; headache: 100% vs 17%, respectively, memory loss: 94% vs 28%, dizziness: 83% vs 47%, visual impairment: 81% vs 25%, nausea: 78% vs 42% (P < 0.01). These effects were also observed at the 6 month follow-up examination (P < 0.01). Work status was also significantly improved at follow-up. CONCLUSIONS: We conclude that CSF leak should be considered in some cases of chronic WAD and that EBP is an effective therapy for chronic WAD.

[Epidural blood patch as a successful treatment of Barrè-Lièou syndrome: report of two cases].

Barrè-Lièou syndrome accompanies neurological symptoms after neck sprain, and is often difficult to treat. We describe two young men with various neurological symptoms after traffic accident, who were diagnosed with Barrè-Lièou syndrome. Both case 1 (41-year-old man) and case 2 (34-year-old man) showed no abnormal findings in head and cervical X-ray, CT-scan and MRI. Only radionuclide cisternography (RNC) showed cerebrospinal fluid (CSF) leak into epidural space at thoracolumbar level. Three months (case 1) and four years (case 2) had passed after each accident. Two patients underwent epidural blood patch (EBP) for total of three times. The average volumes of the blood used for EBP were 30 ml (case 1) and 24 ml (case 2). The procedure improved various symptoms except for neck stiffness and dizziness. EBP had led to low back pain, which disappeared within three days. CSF leak vanished in RNC after EBP. Severe complication, for example epidural infection or neurological disorders due to hematoma, was not noticed. While neural blockade did not relieve pain before EBP, we could get good effect from neural blockade for remaining symptoms after EBP. We consider that Barrè-Lièou syndrome is due to CSF leak and EBP may be one of the useful treatments.