Ruthenium catalysts (5-15 wt.%) deposited on the high surface area magnesia (S BET = 94 m 2 /g), ... more Ruthenium catalysts (5-15 wt.%) deposited on the high surface area magnesia (S BET = 94 m 2 /g), magnesium-aluminum spinel (96 m 2 /g) and magnesia-alumina mixture (Mg:Al = 1:2 molar ratio, 65 m 2 /g) were characterized by the chemisorption techniques and tested in NH 3 synthesis. The chemisorption experiments (O 2 , CO) have shown that ruthenium is highly dispersed (FE = 60-95%), even if the Ru loading is high (∼15 wt.%). The catalytic properties (TOF) of small ruthenium particles supported on Mg-Al spinel (the most effective unpromoted systems) proved to be only slightly, by 40%, more advantageous in NH 3 synthesis at 400 • C and 63 bar than the properties of particles supported on MgO-Al 2 O 3 mixture (the least active system), TOF over the former being roughly independent of the Ru crystallite size (1.0-1.5 nm). In contrast, the activities of the Ba-doped samples differed significantly, i.e. the TOF values (63 or 90 bar, 400 • C) over optimally promoted Ba-Ru/MgO were by four to eight times higher than those over Ba-Ru/Mg-Al spinel and by 30 times higher than over Ba-Ru/MgO-Al 2 O 3 mixture. The effect of the support on the Ba promotion is discussed. Under comparable conditions (400 • C, 63 bar, 8.5% NH 3 and 400 • C, 90 bar, 11% NH 3), the Ba-Ru/MgO catalyst (10 wt.% Ru) was by several times more active than multipromoted fused iron, the comparison being based on the volumetric reaction rates.
The cobalt, iron and Co-Fe catalysts deposited on carbon were prepared, characterised (XRD, H 2 T... more The cobalt, iron and Co-Fe catalysts deposited on carbon were prepared, characterised (XRD, H 2 TPD) and studied in ammonia synthesis at 90 bar (H 2 :N 2 = 3:1). Partly graphitised carbon material obtained via high temperature treatment (1900 8C) of commercial activated carbon was used as a support for the active metals (10 wt.%) and barium or potassium were used as promoters. XRD studies of unpromoted materials have shown that cobalt (5-20% in Co + Fe) dissolves in the iron phase (alloy formation); the average sizes of crystallites (20-30 nm) are roughly independent of the metal kind (Co, Fe, Co-Fe). The effect of Ba and that of K on the catalyst performance proved to be strongly dependent on the choice of an active phase (Co or Fe or Co-Fe). In the case of Co/C, the promotional effect of barium was extremely large. Furthermore, the Ba-Co/ C system was found to be less inhibited by the ammonia product than Ba-Fe/C. At low temperature (400 8C) and at high conversion (8% NH 3 in the gas), the surface-based reaction rate (TOF) for Ba-Co/C is about six times higher than that for Ba-Fe/C.
The subjects of the research were barium-promoted ruthenium catalysts for ammonia synthesis suppo... more The subjects of the research were barium-promoted ruthenium catalysts for ammonia synthesis supported on graphitized carbon. The purpose of this work was to study in detail the process of an active Ba-Ru/C catalyst formation. Another goal was to characterize the active state of the Ba promoter, that is the state corresponding to ammonia synthesis conditions. In situ XRD and TPR-MS techniques were applied to monitor the changes in the Ba-Ru/C specimens when heating in hydrogen (or H 2 + N 2 ) and H 2 + Ar mixtures, respectively. The post-activation state of the catalyst was characterized chemically via interaction of the reduced samples with water vapour at 50 °C and also via interaction with oxygen at 0 °C. The above mentioned experiments were supplemented with those of ammonia synthesis. It was shown that ruthenium facilitates decomposition of the promoter's precursor (Ba(NO 3 ) 2 ) deposited onto the surface of Ru/C catalysts when heating the specimens in a hydrogen-containing stream. The Ba(NO 3 ) 2 /C reference materials, which do not contain ruthenium, are stable in a flowing H 2 + Ar mixture up to about 400 °C, whereas the Ba(NO 3 ) 2 decomposition starts at 100-120 °C in the Ba(NO 3 ) 2 -Ru/C systems (XRD, TPR-MS). The decomposition of Ba(NO 3 ) 2 in hydrogen leads to barium oxide (BaO) and metallic barium. Under steady-state conditions BaO is the only Ba-containing phase detected by the X-ray diffraction technique. Characterization of the post-activation catalysts showed that barium is partially reduced during the aforementioned operations and that these catalysts react with oxygen and water vapour. Based on the comparison of the O 2 consumption and H 2 evolution data one may deduce that the active form of the promoter is a mixture: Ba 0 + BaO. It can be stated that the temperature and content of the promoter (C Ba ) have a significant influence on NH 3 formation. The shape of reaction rate vs. barium content function is assumed to be an outcome of the promoter distribution on the active carbon surface and ruthenium surface. The trend of the integral reaction rate clearly reflects that of the Ru coverage by the barium-containing species, which is controlled by the heats of adsorption on ruthenium and carbon, respectively.
Przedstawiono rezultaty prac nad otrzymywaniem podłoża ceramicznego przeznaczonego do wytwarzania... more Przedstawiono rezultaty prac nad otrzymywaniem podłoża ceramicznego przeznaczonego do wytwarzania ozonu w wyładowaniach elektrycznych zachodzących na powierzchni dielektryka. Uzyskane materiały pozwalają na realizowanie dobrze rozwiniętych wyładowań powierzchniowych. Powierzchnia zewnętrzna podłoża ceramicznego może być w łatwy sposób modyfikowana poprzez nanoszenie krzemionkowej warstwy aktywnej.
The results of studies on the ozone synthesis under discharges generated on the surface of the ce... more The results of studies on the ozone synthesis under discharges generated on the surface of the ceramic actuator built as the concentric strips electrode system are presented. Experiments were carried out in pure oxygen, using the high voltage push-pull inverter. The ozonizer, in which the gas flows with variable linear velocity was used. The ozone concentrations and the process energy efficiency show the possibility of effective ozone generation in the reactors with non-conventionally organized discharge space. (Zastosowanie koncentrycznego elementu wyladowczego do syntezy ozonu w wyladowaniach powierzchniowych). Streszczenie. Przedstawiono wyniki badan nad syntezą ozonu w wyladowaniach powierzchniowych, wytwarzanych na powierzchni ceramicznego elementu wyladowczego (actuatora). Elektroda wysokonapieciowa actuatora skladala sie z zespolu koncentrycznych ściezek przewodzących. Eksperymenty prowadzono w czystym tlenie przy uzyciu zasilacza typu push-pull. Uzywano ozonatora, przez ktor...
ABSTRACT Preliminary studies on efficiency of ozone synthesis under bipolar pulse discharge condi... more ABSTRACT Preliminary studies on efficiency of ozone synthesis under bipolar pulse discharge conditions were carried out. Ozone synthesis from pure oxygen limited the number of process parameters. Selected results of these studies are presented.
Ruthenium catalysts (5-15 wt.%) deposited on the high surface area magnesia (S BET = 94 m 2 /g), ... more Ruthenium catalysts (5-15 wt.%) deposited on the high surface area magnesia (S BET = 94 m 2 /g), magnesium-aluminum spinel (96 m 2 /g) and magnesia-alumina mixture (Mg:Al = 1:2 molar ratio, 65 m 2 /g) were characterized by the chemisorption techniques and tested in NH 3 synthesis. The chemisorption experiments (O 2 , CO) have shown that ruthenium is highly dispersed (FE = 60-95%), even if the Ru loading is high (∼15 wt.%). The catalytic properties (TOF) of small ruthenium particles supported on Mg-Al spinel (the most effective unpromoted systems) proved to be only slightly, by 40%, more advantageous in NH 3 synthesis at 400 • C and 63 bar than the properties of particles supported on MgO-Al 2 O 3 mixture (the least active system), TOF over the former being roughly independent of the Ru crystallite size (1.0-1.5 nm). In contrast, the activities of the Ba-doped samples differed significantly, i.e. the TOF values (63 or 90 bar, 400 • C) over optimally promoted Ba-Ru/MgO were by four to eight times higher than those over Ba-Ru/Mg-Al spinel and by 30 times higher than over Ba-Ru/MgO-Al 2 O 3 mixture. The effect of the support on the Ba promotion is discussed. Under comparable conditions (400 • C, 63 bar, 8.5% NH 3 and 400 • C, 90 bar, 11% NH 3), the Ba-Ru/MgO catalyst (10 wt.% Ru) was by several times more active than multipromoted fused iron, the comparison being based on the volumetric reaction rates.
The cobalt, iron and Co-Fe catalysts deposited on carbon were prepared, characterised (XRD, H 2 T... more The cobalt, iron and Co-Fe catalysts deposited on carbon were prepared, characterised (XRD, H 2 TPD) and studied in ammonia synthesis at 90 bar (H 2 :N 2 = 3:1). Partly graphitised carbon material obtained via high temperature treatment (1900 8C) of commercial activated carbon was used as a support for the active metals (10 wt.%) and barium or potassium were used as promoters. XRD studies of unpromoted materials have shown that cobalt (5-20% in Co + Fe) dissolves in the iron phase (alloy formation); the average sizes of crystallites (20-30 nm) are roughly independent of the metal kind (Co, Fe, Co-Fe). The effect of Ba and that of K on the catalyst performance proved to be strongly dependent on the choice of an active phase (Co or Fe or Co-Fe). In the case of Co/C, the promotional effect of barium was extremely large. Furthermore, the Ba-Co/ C system was found to be less inhibited by the ammonia product than Ba-Fe/C. At low temperature (400 8C) and at high conversion (8% NH 3 in the gas), the surface-based reaction rate (TOF) for Ba-Co/C is about six times higher than that for Ba-Fe/C.
The subjects of the research were barium-promoted ruthenium catalysts for ammonia synthesis suppo... more The subjects of the research were barium-promoted ruthenium catalysts for ammonia synthesis supported on graphitized carbon. The purpose of this work was to study in detail the process of an active Ba-Ru/C catalyst formation. Another goal was to characterize the active state of the Ba promoter, that is the state corresponding to ammonia synthesis conditions. In situ XRD and TPR-MS techniques were applied to monitor the changes in the Ba-Ru/C specimens when heating in hydrogen (or H 2 + N 2 ) and H 2 + Ar mixtures, respectively. The post-activation state of the catalyst was characterized chemically via interaction of the reduced samples with water vapour at 50 °C and also via interaction with oxygen at 0 °C. The above mentioned experiments were supplemented with those of ammonia synthesis. It was shown that ruthenium facilitates decomposition of the promoter's precursor (Ba(NO 3 ) 2 ) deposited onto the surface of Ru/C catalysts when heating the specimens in a hydrogen-containing stream. The Ba(NO 3 ) 2 /C reference materials, which do not contain ruthenium, are stable in a flowing H 2 + Ar mixture up to about 400 °C, whereas the Ba(NO 3 ) 2 decomposition starts at 100-120 °C in the Ba(NO 3 ) 2 -Ru/C systems (XRD, TPR-MS). The decomposition of Ba(NO 3 ) 2 in hydrogen leads to barium oxide (BaO) and metallic barium. Under steady-state conditions BaO is the only Ba-containing phase detected by the X-ray diffraction technique. Characterization of the post-activation catalysts showed that barium is partially reduced during the aforementioned operations and that these catalysts react with oxygen and water vapour. Based on the comparison of the O 2 consumption and H 2 evolution data one may deduce that the active form of the promoter is a mixture: Ba 0 + BaO. It can be stated that the temperature and content of the promoter (C Ba ) have a significant influence on NH 3 formation. The shape of reaction rate vs. barium content function is assumed to be an outcome of the promoter distribution on the active carbon surface and ruthenium surface. The trend of the integral reaction rate clearly reflects that of the Ru coverage by the barium-containing species, which is controlled by the heats of adsorption on ruthenium and carbon, respectively.
Przedstawiono rezultaty prac nad otrzymywaniem podłoża ceramicznego przeznaczonego do wytwarzania... more Przedstawiono rezultaty prac nad otrzymywaniem podłoża ceramicznego przeznaczonego do wytwarzania ozonu w wyładowaniach elektrycznych zachodzących na powierzchni dielektryka. Uzyskane materiały pozwalają na realizowanie dobrze rozwiniętych wyładowań powierzchniowych. Powierzchnia zewnętrzna podłoża ceramicznego może być w łatwy sposób modyfikowana poprzez nanoszenie krzemionkowej warstwy aktywnej.
The results of studies on the ozone synthesis under discharges generated on the surface of the ce... more The results of studies on the ozone synthesis under discharges generated on the surface of the ceramic actuator built as the concentric strips electrode system are presented. Experiments were carried out in pure oxygen, using the high voltage push-pull inverter. The ozonizer, in which the gas flows with variable linear velocity was used. The ozone concentrations and the process energy efficiency show the possibility of effective ozone generation in the reactors with non-conventionally organized discharge space. (Zastosowanie koncentrycznego elementu wyladowczego do syntezy ozonu w wyladowaniach powierzchniowych). Streszczenie. Przedstawiono wyniki badan nad syntezą ozonu w wyladowaniach powierzchniowych, wytwarzanych na powierzchni ceramicznego elementu wyladowczego (actuatora). Elektroda wysokonapieciowa actuatora skladala sie z zespolu koncentrycznych ściezek przewodzących. Eksperymenty prowadzono w czystym tlenie przy uzyciu zasilacza typu push-pull. Uzywano ozonatora, przez ktor...
ABSTRACT Preliminary studies on efficiency of ozone synthesis under bipolar pulse discharge condi... more ABSTRACT Preliminary studies on efficiency of ozone synthesis under bipolar pulse discharge conditions were carried out. Ozone synthesis from pure oxygen limited the number of process parameters. Selected results of these studies are presented.
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