Oxygen

About: Oxygen is a research topic. Over the lifetime, 48149 publications have been published within this topic receiving 1113788 citations. The topic is also known as: O & Oxygen.

Dense perovskite membrane reactors for partial oxidation of methane to syngas

Abstract: The partial oxidation of methane to synthesis gas (syngas, CO + H2) was performed in a mixed-conducting perovskite dense membrane reactor at 850°C, in which oxygen was separated from air and simultaneously fed into the methane stream. Steady-state oxygen permeation rates for La1-xA′xFe0.8 Co0.2O3-δ perovskite membranes in nonreacting air/helium experiments were in the order of A′x = Ba0.8 > Ba0.6 > Ca0.6 > Sr0.6. Deep oxidation products were obtained from a La0.2 Ba0.8 Fe0.8 Co0.2 O3–δ disk-shaped membrane reactor without catalyst, with a 4.6% CH4 inlet stream. These products were further reformed to syngas when a downstream catalytic bed was added. Packing the 5% Ni/Al2O3 catalyst directly on the membrane reaction-side surface resulted in a slow fivefold increase in O2 permeation, and a fourfold increase in CH4 conversion. XRD, EDS, and SEM analyses revealed structure and composition changes on the membrane surfaces. Oxygen continuously transported from the air side appeared to stabilize the membrane interior, and the reactor was operated for up to 850 h.

Regulatory mechanisms of hemoglobin oxygen affinity in acidosis and alkalosis

Abstract: The recent reports of the effect of 2,3-diphosphoglycerate (2,3-DPG) on hemoglobin affinity for oxygen suggested that this substance may play a role in man's adaptation to acidosis and alkalosis.A study of the effect of induced acidosis and alkalosis on the oxyhemoglobin dissociation curve of normal man was therefore carried out, and the mechanisms involved in the physiological regulation of hemoglobin oxygen affinity examined.In acute changes of plasma pH there was no alteration in red cell 2,3-DPG content. However, there were changes in hemoglobin oxygen affinity and these correlated with changes in mean corpuscular hemoglobin concentration (MCHC). With maintained acidosis and alkalosis, red cell 2,3-DPG content was altered and correlated with the changes in hemoglobin oxygen affinity. Both of these mechanisms shift the hemoglobin oxygen dissociation curve opposite to the direct pH (Bohr) effect, and providing the rate of pH change is neither too rapid nor too large, they counteract the direct pH effect and the in vivo hemoglobin oxygen affinity remains unchanged. It is also shown that approximately 35% of the change in hemoglobin oxygen affinity resulting from an alteration in red cell 2,3-DPG, is explained by effect of 2,3-DPG on the red cell pH.