Direct partial oxidation of methane into methanol is a cornerstone of catalysis. The stepped conversion of methane into methanol currently involves activation at high temperature and reaction with methane at decreased temperature, which limits applicability of the technique. The first implementation of copper-containing zeolites in the production of methanol directly from methane is reported, using molecular oxygen under isothermal conditions at 200 °C. Copper-exchanged zeolite is activated with oxygen, reacts with methane, and is subsequently extracted with steam in a repeated cyclic process. Methanol yield increases with methane pressure, enabling reactivity with less reactive oxidized copper species. It is possible to produce methanol over catalysts that were inactive in prior state of the art systems. Characterization of the activated catalyst at low temperature revealed that the active sites are small clusters of copper, and not necessarily di- or tricopper sites, indicating that catalysts can be designed with greater flexibility than formerly proposed.

The characterization and reactive properties of copper zeolites with twelve framework topologies (MOR, EON, MAZ, MEI, BPH, FAU, LTL, MFI, HEU, FER, SZR, and CHA) are compared in the stepwise partial oxidation of methane into methanol. Cu2+ ion‐exchanged zeolite omega, a MAZ‐type material, reveals the highest yield (86 μmol g(cat.)−1) among these materials after high‐temperature activation and liquid methanol extraction. The high yield is ascribed to the relatively high density of copper–oxo active species, which form in its three‐dimensional 8‐membered (MB) ring channels. In situ UV/Vis studies show that diverse copper species form in different zeolites after high‐temperature activation, suggesting that there are no universally active species. Nonetheless, there are some dominant factors required for achieving high methanol yields: 1) highly dispersed copper–oxo species; 2) large amount of exchanged copper in small‐pore zeolites; 3) moderately high temperature of activation; and 4) use of proton form zeolite precursors. Cu‐omega and Cu‐mordenite, with the proton form of mordenite as the precursor, yield methanol after activation in oxygen and reaction with methane at only 200 °C, that is, under isothermal conditions.

Direct partial oxidation of methane into methanol is acornerstone of catalysis.The stepped conversion of methane into methanol currently involves activation at high temperature and reaction with methane at decreased temperature,w hich limits applicability of the technique.T he first implementation of copper-containing zeolites in the production of methanol directly from methane is reported, using molecular oxygen under isothermal conditions at 200 8 8C. Copper-exchanged zeolite is activated with oxygen, reacts with methane,a nd is subsequently extracted with steam in arepeated cyclic process. Methanol yield increases with methane pressure,e nabling reactivity with less reactive oxidized copper species.I ti s possible to produce methanol over catalysts that were inactive in prior state of the art systems.C haracterization of the activated catalyst at low temperature revealed that the active sites are small clusters of copper,a nd not necessarily di-or tricopper sites,i ndicating that catalysts can be designed with greater flexibility than formerly proposed.

The study of autoxidation of hemoglobin A followed by rapid chain separation revealed that the oxidation rates of a and 0 chains differ by a factor of ten. This difference was most evident at pH 6.5 but disappeared at pH 9.0. It is present but less pronounced in the case of isolated chains. Analogous results were obtained when Hb A was oxidized by K3[Fe(CN)sl. Lowering the oxygen pressure increased the rate of autoxidation, more so for 0 than for a! chains. Two factors thus govern the oxidation rate: (1) intrinsic oxidizability of cy being faster than p ; ( 2 ) the presence or absence of ligand. Decreasing O2 pressure affects the oxidation rate of 0 chains more than that of a! chains; 0 chains thus appear to have a lower affinity for oxygen.

The ferrous iron of hemoglobin is exposed continuously to high concentrations of oxygen and, thereby, is oxidized slowly to methemoglobin, a protein unable to carry oxygen. To restore hemoglobin function, methemoglobin (ferrihemoglobin) must be reduced to hemoglobin (ferrohemoglobin). Under physiological conditions, methemoglobin reduction is accomplished mainly by red cell NADH-cytochrome b5 reductase (NADH-methemoglobin reductase) so efficiently that there is insignificant amounts of methemoglobin in the circulating blood. However, should methemoglobin formation be increased--e.g., due to the presence of oxidant drugs, or an abnormal methemoglobin not amenable to reduction (hemoglobin M), or a deficiency in red cell cytochrome b5 reductase--methemoglobinemia will result. Most methemoglobinemias have no adverse clinical consequences and need not be treated. Under certain conditions, such as exposure to large amounts of oxidant or in young infants, rapid treatment is necessary. In hereditary cytochrome b5 deficiency, treatment is often directed at improving the poor cosmetic effect of persistent cyanosis with the minimum amount of drugs to give satisfactory clinical results.

No abstract

Physical properties and mathematical modeling of 5 melon (Cucumis melo L.) seeds and kernels 6 Abstract In the present research, some physical properties of Somsori and Varamin varieties of melon seeds and kernels were studied; three principal dimensions (length, width and thickness) of melon seeds and kernels were measured using image processing technique. Results indicated that mass of the Somsori and Varamin varieties seeds was equal to 0.043 and 0.052 g, respectively. The corresponding value for melon kernels was found to be 0.031 and 0.036, respectively. True density of the Somsori and Varamin varieties seeds was equal to 1182.612 and 1132.058 kg m À3 , respectively. The corresponding value for melon kernels was found to be 1479.731 and 1535.911 kg m À3 , respectively. Results showed that with increasing volume of container from 500 mL to 600 mL bulk density of the seeds increased. But with increasing volume of container from 600 mL to 1500 mL, bulk density of the seeds decreased. Also with increasing volume of container from 500 mL to 1000 mL bulk density of the kernels increased. But with increasing volume of container from 1000 mL to 1500 mL, bulk density of the kernels decreased. Values of coefficient of friction of seeds and kernels on rubber surface were more than the iron, galvanized and plywood surfaces, but values of coefficient of friction of seeds and kernels on galvanized surface were less the other surfaces. Comparison between three methods of measuring angle of repose showed that values based on pouring method and filling method were more and less than the other methods, respectively. ª 2015 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.