Effect Of Activation Conditions Research Articles

Absorption Characteristics of Phenolic-Based Carbon Fiber Absorbents

Phenolic-based fabrics are used as base materials for preparing carbon fiber absorbents by means of oxidation, carbonization, and activation in a continuous semi-open high-temperature furnace. The effect of activation conditions on the pore characteristics and absorption capabilities is studied. The results show that the pore diameter of specimens is within 100 Å, indicating micropore and mesopore structures. In addition, phenolic-based carbon fiber absorbents show over 50% absorption for four volatile organic compounds, and their regeneration capabilities can reach 100%.

Effects of activation conditions on BET specific surface area of activated carbon nanotubes

The effects of different activation conditions, including KOH/CNTs ratio, activation temperature, activation time, and nitrogen flow rate, on the specific surface area of activated carbon nanotubes (CNTs) prepared with KOH were investigated. The nanometer hollow tube structure of CNTs can be well preserved for the activated CNTs but their BET specific surface area is significantly enlarged. The best results of activated CNTs with larger BET specific surface areas can be achieved by optimizing the four factors amongst which the KOH/CNTs ratio is found to be dominant.

Carbonization and activation techniques for production of carbonaceous adsorbent

The present paper reviews carbonization and activation techniques for the production of carbonaceous adsorbents with the optimal properties for their intended purpose. The physical adsorption ability of the adsorbent increases with increase in specific surface area and with decrease in mean pore diameter. The chemical adsorption properties of the adsorbent are affected by surface functional groups such as carboxyl and phenolic hydroxyl, which influence the adsorption behavior of ionic compounds by dissociating into ions in aqueous solution. Regarding carbonization techniques, the paper discusses the pore-size distribution of charcoals prepared from various types of wood, the effect of carbonization temperature and gas atmosphere on the physical adsorption properties and on the surface functional groups of charcoal, and the effect of raw material other than wood. Regarding activation techniques, the basic principle of the steam activation method and the effect of activation conditions on pore-size distribution are discussed. In addition, the characteristics of the new air activation method are described. Regarding chemical activation, an outline is given of the characteristics of the alkali activation method, which produces activated carbon with high surface area.

03/02215 Effects of activation conditions on the activity of carbons from Fort Union lignites: Sharma, R. K. and Olson, E. S. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 63–64

03/02215 Effects of activation conditions on the activity of carbons from Fort Union lignites: Sharma, R. K. and Olson, E. S. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 63–64

Influence of Activation and the HDS Reaction on the Structure of Magnesium Fluoride-Supported Ru Catalysts Derived from Ruthenium Chloride Hydrate

The effect of activation conditions and the hydrodesulfurization (HDS) process on the structure of Ru/MgF2 prepared from RuCl3⋅nH2O precursor catalysts was studied. During the first 6-7 h of the HDS process significant differences in activities were detected between samples pretreated in 50% H2S/H2 and in 50% H2S/He. During this transient time, the Ru/MgF2 catalyst pretreated in 50% H2S/H2 increased in activity while the activity of that pretreated in H2S/He decreased. XRD, TPR and quantitative analysis of sulfur content revealed that directly after activation in H2S/He crystalline ruthenium sulfide is the main component of the surface, whereas after activation in H2S/H2 both RuS2 and metallic Ru are present on the surface. These differences decrease during the thiophene HDS process. Despite the different pretreatment conditions, the composition of the surface tends to “equilibrate”, which results in similar activity after prolonged reaction time.

Attrition resistance of spray-dried iron F–T catalysts: Effect of activation conditions

The focus of the research reported herein was to investigate the effects of phase changes, as occur during Fe catalyst activation and Fischer–Tropsch synthesis, on Fe catalyst attrition resistance. Different activation conditions (CO, H 2 or syngas) were applied prior to attrition testing to a selected spray-dried Fe catalyst containing 9.1 wt.% binder SiO 2, which had been shown to have the highest attrition resistance in our early study of calcined catalysts. Although, XRD indicated that different Fe phase compositions resulted in the differently activated catalyst samples, chemical attrition was not observed for any of the samples. The BET surface areas of the activated samples were smaller than that of the calcined precursor but no significant changes in pore volume and particle size were found. The attrition resistances of the differently activated catalyst samples were found to be similar to that of the calcined catalyst for this spray-dried Fe catalyst. Attrition resistance was found previously to be governed by catalyst particle density, which has been shown earlier to relate to the SiO 2 network in catalysts. It is therefore suggested that the type and concentration of SiO 2 that is incorporated during the preparation of spray-dried Fe catalysts have a much more significant impact on catalyst attrition than Fe phase change during activation in the presence of CO, H 2 or H 2+CO.

A microcalorimetric investigation of heteropolyacids

Differential heats of ammonia sorption onto and into heteropolyacids (HPA's) of tungsten and molybdenum (HPW, HSiW, HPMo and HSiMo) were measured microcalorimetrically to characterize the acidic properties of these metal oxygen cluster compounds (MOCC's). An effect of activation conditions was observed in that a lower activation temperature resulted in a higher differential heat of sorption but a lower number of acidic sites accessible for NH 3. Complementary investigations, i.e., TG, XRD, TPD of water-containing species and ammonia as well as 1H MAS NMR experiments, were carried out. These provided evidence that structural and acid properties as well as site accessibility of the HPA's significantly depend on H 2O (or H 5O + 2) and NH 3 loading. A comparison of the results of microcalorimetry of NH 3 sorption into and TPD of NH 3 from HPA's suggests that the former technique is more reliable in order to elucidate acidic properties of HPA's.

The effects of activation conditions on the porous structure of NiMo-Al 2O 3 catalyst

The results of investigating the porous structure of oxide, reduced and sulphided forms of alumina-supported nickel molybdena catalysts are presented. Microdistribution of the pores was determined by low-temperature nitrogen adsorption, and macrodistribution was determined by mercury porosimetry. The changes in pore-size distribution of different forms of NiMo-Al 2O 3 catalyst are discussed in relation to the conditions of its activation.