ABSTRACT
Nanocrystalline ZSM-5 with a Si/Al ratio of 20 was synthesized using clear solutions and a hydrothermal synthesis procedure. The resulting ZSM-5 materials were characterized by powder X-ray diffraction, scanning electron microscopy (SEM), nitrogen adsorption isotherms, solid-state nuclear magnetic resonance, and toluene adsorption. A commercial ZSM-5 sample was similarly characterized for comparison with the synthesized materials. The particle sizes of the synthesized ZSM-5 samples were calculated using the measured external surface areas and were determined to be 15 and 60 nm. SEM images indicated that the ZSM-5 samples consist of agglomerated and possibly intergrown particles. Toluene adsorption measurements showed that the ZSM-5 sample with a particle size of 15 nm adsorbed approximately 50% more toluene than the other ZSM-5 samples, most likely due to the adsorption of toluene on the external surface. For the toluene adsorbed on the internal zeolite surface, approximately one toluene molecule was adsorbed per channel intersection for each of the ZSM-5 samples.
Subject(s)
Nanostructures/chemistry , Zeolites , Adsorption , Aluminum/chemistry , Crystallization , Magnetic Resonance Spectroscopy , Particle Size , Silicon/chemistry , Surface Properties , Zeolites/chemical synthesis , Zeolites/chemistryABSTRACT
Silicalite-1 powders with crystal sizes ranging from 20 to 1000 nm were synthesized by systematically varying synthesis gel composition, pressure, temperature, and time duration. These samples were characterized by powder X-ray diffraction, scanning electron microscopy, nitrogen adsorption isotherms, solid-state nuclear magnetic resonance, and toluene adsorption. The effect of crystal size on the physical properties of crystals is observed, including a large increase of both total and external surface area when crystal size decreases. The relationship between particle size and external surface area was modeled by assuming a cubic crystal geometry. The nanosized silicalite samples with crystal sizes less than 100 nm have a higher adsorption capacity for toluene, showing promising potential for its application in volatile organic compound removal.
ABSTRACT
Surgery of the upper abdomen is associated with the greatest demand for postoperative analgesia and also is marked by depressed pulmonary function, arterial hypoxemia, and pulmonary complications. Nitrous oxide (N2O) in concentrations of 15-25% is a potent analgesic and is relatively free of untoward side effects if administered for a maximum of 48 h. In the present study, the effect of N2O analgesia on postoperative lung function, in particular, the functional residual capacity (FRC), is examined. Eighteen cholecystectomy patients received either a narcotic (N = 11) or N2O (N = 7) for postoperative analgesia. N2O-treated patients had satisfactory analgesia and maintained FRC at normal levels. Narcotic treated patients had a fall of 22% in FRC. N2O had no effect on the formed elements in peripheral blood.
Subject(s)
Functional Residual Capacity , Lung Volume Measurements , Nitrous Oxide/therapeutic use , Pain, Postoperative/drug therapy , Cholecystectomy , Drug Evaluation , Humans , Middle Aged , Nitrous Oxide/pharmacologyABSTRACT
Helium detectors utilizing thermal conductivity are sensitive to the presence of nitrous oxide (N2O) and oxygen (O2). Measurement of the level of these gases within the spirometer may be used to obtain the true helium concentration for use in the calculation of functional residual capacity (FRC). Linear relationships were obtained relating the change (delta) in reading of the helium meter by nitrous oxide and oxygen. The regression equations are: delta O2 = 0.027 (%O2) - 0.513; delta N2O = -0.276 (%N2O). Failure to correct the helium reading for N2O will overestimate lung volume; elevations of O2 above 21% will underestimate the lung volume.
