R.S. Mann

Thermal effect on the electron donating and accepting properties of Na-Y zeolite, and the reduction of SO2 and CO

Abstract A study was made of the formation of phenothiazine cation radical (TPQD+) and tetracyanoethylene anion radical (TCNE−) on the surface of Na-Y zeolite. It was observed using electron spin resonance (e.s.r.) that the number of cation formation sites decreased with higher activation temperature while the number of anion sites increased, the respective changes not being in proportion. The formation of the SO2− anion radical on Na-Y zeolite was studied at 450°C. It was observed that the e.s.r. line intensity of SO2− increased with the reaction time, and also with the length of degassing time during thermal activation. CO+ cation radicals were formed when the SO2-treated zeolite was heated at 450°C in contact with CO. The CO+ radicals disappeared either on prolonged heating or heating in the presence of air. The SO2 ions do not take part in the reduction of SO2− with the CO over zeolite. Mechanisms for the formation of CO+ and the other observed effects is discussed.

Electron spin resonance of vanadium pentoxide molybdenum trioxide catalysts

X‐ray, infrared, and electron spin resonance (ESR) studies were made on molybdenum trioxide catalysts doped with 0.25, 0.5, 2.0, 5.0, 10.0, and 20% by weight vanadium pentoxide. X‐ray diagrams indicate the existence of two kinds of patterns for catalysts containing more than 2% V2O5. All the samples produced ESR signals, including pure V2O5. For low dopant concentrations the signals were well resolved, and the paramagnetic center was identified as the VO2+ ion in the unit structure VO2+5O2−. The resonance lines increased in width as the dopant concentration was increased to 10%, and only a single broad line existed for 20% V2O5 or pure V2O5.

Electron spin resonance studies of some Canadian coals

Abstract Nine Canadian coals of different rank and composition were studied by electron spin resonance. For percentage of fixed carbon in the range of 43 to 78 wt%, the free radical g values were found to increase with decreasing carbon content, and did not level off for the low rank coals. The free radical linewidths are attributed to atomic species such as oxygen and not to protons of hydrogen.

Separation of acidic fraction from the Cold Lake bitumen asphaltenes and its relationship to enhanced oil recovery

Abstract Neutral and acidic fractions of cold lake bitumen asphaltene were separated on a KOH treated silica column. It was observed that the neutral fraction can be separated by using CHCl3 as solvent (eluent) while the acidic fraction can be separated by a CHCl3 + HCOOH mixture. While the distribution of VO2+ ion was approximately the same in the different fractions, the concentration of the radicals may be significantly more in the acidic fraction. The acidic fraction separated has the largest impact on decreasing the interfacial tension (IFT) between asphaltene (in toluene) and 25mM NaOH solution. It was also observed that adsorbed KOH on silica reacted with CHCl3 when the CHCl3 + HCOOH mixture was passed through the column.

Characterization of MoOs-zeolite prepared from ammonium molybdate

Abstract Mo03 zeolite (MoC)3-NaY zeolite) catalyst was prepared by the thermal decomposition of ammonium molybdate adsorbed in the NaY zeolite in aqueous media. The catalyst prepared thus was characte- rized by scanning electron microscope (SEM), measuring surface area (BET), X-ray diffraction, chemical analysis, effect of CO on adsorbed SO;, and the e.s.r. technique. The electron-accepting and -donating properties were also studied by measuring the concentration ofthiophenazine cation radical (TPQD*) and tetracyanoethylene anion radical (TONE ) formed. Ten percent M0+6 of MoOs-NaY zeolite when activated at 450°Cn vacuum changed to Mo+5 ions. The formation of Mo+3 was observed during 802 reduction by CO at 450°C.

Interaction of V2O5-NaY zeolite with H2S and SO2

Abstract V2O5-NaY zeolite catalyst was prepared by vacuum impregnation of ammonium metavanadate solution in water on NaY-zeolite (zeolite). The slurry was filtered, washed, dried, and calcined at 600°C. On heating the catalyst at 450°C in vacuum, VO2+ species were detected by e.s.r. It was observed that the electron-accepting and -donating sites increased when V2O5 or vanadium species were loaded on it. Vanadium species poisoned the active sites of the zeolite that were responsible for the formation of SO2− ions. Pretreated V2O5-NaY zeolite with SO2 plays an important role in the formation of VO2+ species when it is treated with H2S at room temperature. V2O5-NaY zeolite can be used for the reduction of SO2 by H2S.

Reaction of CO and SO2 over Cu-mordenite

Abstract A study is made of the chemisorption of CO and SO2 over Cu-mordenite by means of electron spin resonance (ESR). Two Cu2+ magnetic complexes are observed in Cu-mordenite, and the reaction with CO causes a differential reduction in their respective line intensities. For reaction at room temperature, the effect is reversible upon removal of the CO, but when the system is heated the catalyst changes irreversibly. Introduction of SO2 to the Cu-mordenite-CO system causes the reappearance of the Cu2+ spectrum in a single, different, magnetic complex. Models are proposed to explain the chemical processes operative in the reactions.

ESR study of SO2 on MnO2-alumina

SO3− radicals are formed during the reaction between SO2 and MnO2-alumina, which suggests that SO3− take part in the reduction of Mn4+ to Mn2+.AbstractВ ходе реакции между SO2 и MnO2/Al2O3 наблюдалось образование радикалов SO3−, откуда полагали, что SO3− принимает участие в восстановлении Mn4+ до Mn2+.

Pyrolysis of poplar bark

Abstract Pyrolysis of poplar bark is investigated in the temperature range of 573–1023 K. The effect of temperature on the gas production rate, gas yield and composition calorific value of gaseous products and carbon conversion is reported. Production of CO, CH 4 and CO 2 can be predicted by a model based on the assumption that reaction is the rate controlling step.

Characterization of clinoptilolite by interaction of H2S, CO, and SO2 by the e.s.r. technique

Abstract A study was made of the interaction of H2S, CO, and SO2 over activated clinoptilolite at 400°C using the electron spin resonance (e.s.r.) technique. It was observed that the CO- paramagnetic ions are formed over fresh activated clinoptilolite when treated with CO at ∼ 400°C. It was also observed that two types of SO2− ions, i.e., A-type SO2− with hyperfine structure (h.f.s.) and B-type SO2− without h.f.s. are formed over clinoptilolite depending on the experimental conditions. The B-type SO2− ion takes part in the reduction of SO2 by CO or H2S. The presence of CO over fresh activated clinoptilolite poisons the sites that are responsible for the formation of B-type SO2− ions. At room temperature, adsorbed H2S on the fresh activated clinoptilolite is responsible for the formation of paramagnetic Al3+ ions in the structure of clinoptilolite. Clinoptilolite has both electron-accepting and -donating sites. A plausible mechanism for the interaction of H2S, CO, and SO2 over activated clinoptilolite is discussed.