Papers by Keyword: Activity

Abstract: The increasing demand for producing dimethyl ether from synthesis gas explains the renewed interest in studying the activity and stability of catalysts. In the present work, resource catalytic testing of ZSM-5 zeolites was carried out in the one-step synthesis of dimethyl ether from synthesis gas for 120 hours. Formation of condensation products was observed on zeolite surface after catalytic tests which leads to lower catalytic activity of samples. Condensation products were investigated by thermal analysis in an oxidizing atmosphere. Textural characteristics of zeolites before and after reaction were investigated. It was shown that methanol significantly contribute to formation of condensation products on the catalyst surface in the process of dimethyl ether production.

Abstract: Different methods are used to prepare gallium-containing zeolites of a ZSM-5 structure. Their acidic and structural characteristics are investigated and the effect of the method of gallium introduction into a zeolite on distribution and ratio of acid sites of different strengths, as well as on pore volume and diameter is determined. The relationship between the localization of gallium introduced into a zeolite by different methods and its electronic state and the catalytic activity and selectivity of the resulting contacts in the course of propane aromatization is established. The Ga-containing zeolite prepared by impregnation is found to be the most efficient catalyst for conversion of propane into aromatic hydrocarbons.

Abstract: Denpasar City is the capital of Bali Province with the population of about 0.9 million. Denpasar City has experienced high increase in private vehicles use and long trip distance to reach activity locations. The objective of this study is to investigate the accessibility of residents to several activities location in Denpasar City. The activities considered in this study included shopping centers, schools and health facility. Accessibility values were calculated based on Hansen’s Index.This study found that the activities in Denpasar City were not evenly distributed. Several zones mainly located in the center of the city had high accessibility values whilst zones located in the north of Denpasar City had low accessibility values. This has caused long average trip distance travelled by resident of Denpasar City to reach location of activities. In order to reduce the average trip distance, a policy intervention is required to re-arrange location of activities in Denpasar City in the future in the form of mix-used development.

Abstract: The usability of the clay fraction as one of the criteria in the assessment of liquefaction susceptibility is questionable since year 2001. The use of plasticity index to replace clay fraction as a controlling parameter in the criterion is proposed. This paper aims to compare the usability of different parameter in describing the cyclic behaviour of sand-fines mixtures with various plasticity characteristics. The sand-fines mixtures were reconstituted by mixing clean sand with two types of plastic fines at different percentages by weight, at a standardized ratio of 80% of clean sand with 20% of plastic fines. All soil samples were mixed using the dry tamping method to achieve a constant relative density of 20% throughout the specimen. The soil specimens are tested with stress controlled cyclic triaxial apparatus under consolidated undrained condition, with an effective confining pressure of 100kPa. The soil specimens were considered liquefy when the value of pore pressure is equivalent to the initial cell pressure, resulting zeroes effective stress in soil specimen. The results showed that the liquefaction resistance of the sand-fines mixtures increased as the value of plasticity index increased. The plasticity index is a better indicator to describe the liquefaction susceptibility of sand-fines mixtures compare to clay content, plastic limit and activity.

Abstract: Nowadays construction waste piles. For this phenomenon , this paper studied the mortar activity under different dosage of construction waste brick powder . The results show that with the increase of construction waste material content of brick powder, the mortar strength plummet .

Abstract: s. Using industrial waste residue as concrete mineral admixture has become a direction of the development of the green concrete. Nickel slag is mainly introduced, and the chemical composition and preparation of nickel slag powder, and study its physical properties, activity, volume stability and mechanical properties. According to nickel slag powder admixture amount of replacing cement, admixture fineness, mixed with admixture of concrete changes between the intensity of the three, put forward suitable fineness of slag powder and nickel content of concrete.

Abstract: Combined with recent observation data, the paper conclude that the debris flow break-out in high frequency in Jiangjia Ravine, and they belong to rainstorm type, which concentrated in the rainy season, especially during Jun to Aug. As a typical gully of viscous debris flow, the debris flow move with the bed process and obvious feature of surge. The intermittent flow possesses features of high intensity of delivery and long intermittent period. There have obvious relevance between the amount of sediment delivery and the surges of debris-flow break-out at the same year.

Abstract: Work is devoted to the study of new catalysts on the basis of polymermetalyc complexes of transition metals in the oxidation of toluene. Catalytic agents on the basis of iron (III) complexes with the copolymer polietilenimin-polyacrylic acid put on a silicate substrate have been investigated. Special attention is paid to study influence of physical and chemical parameters on oxidation process, to fixing of kinetic and thermodynamic indexes of process.

Abstract: Ni catalysts supported on γ-Al₂O₃ supports modified by different MgO precoating weight were prepared by impregnation method. The surface area, pore diameter and Ni crystallite size were investigated by N₂ adsorption/desorption (BET) and X-ray diffraction (XRD) methods. The reducing temperature and quantity information of reducible nickel species were obtained by H₂-TPR experiments. The CO₂ adsorption/desorption abilities of catalysts were investigated and the activity of catalysts were also measured. The coke resistance performance of catalysts for carbon dioxide reforming of methane (CDRM) was studied by CO₂ temperature programmed surface reaction (CO₂-TPSR). H₂-TPR results revealed that there were three kinds of Ni species on the supports. Appropriate modification amount of MgO could increase the surface nickel active sites which could be easily reduced and prevented the formation of NiAl₂O₄ spinel species. CO₂-TPD indicated that the addition of MgO increased the amount of CO₂ adsorption at lower temperatures. N₂ adsorption/desorption results disclosed that the excessive modification of MgO would decrease the surface area and pore size of the samples. The reforming reaction results showed that the activity was elevated from 58.62% to 65.95% over the Ni/MgO-Al₂O₃ when the Mg/Al ratio was 0.05 (wt.) and there was less coke evidenced by the CO₂-TPSR results comparing to the Ni/γ-Al₂O₃ catalyst.

Abstract: The key factors for activity of asbestos tailings acid leaching residue (ATALR) and activated process were researched by the way of orthoplan, so as to make a new type of high-active mineral admixture in cement-based material, named as porous silica fume (PSF). Then with the strength loss indexes designed, the sulfate attack resistance of cement-PSF mortars was evaluated, which was dunked in solution of sodium sulfate during from 6 to 12 months. The results indicated that thermal activated temperature and holding time was the key factor for compressive strength, while holding time and grinding time for flexural strength. The optimal activated process was the thermal activated temperature at800°C needing to hold for 1 hour before grinding for 20minuteswhilethe appropriate amount of PSF was 5%~12% in cement mortar. When 5%~8% PSF contained, the sulfate attack resistance of cement mortar can be improved obviously, and the role was similar to silica fume (SF). PSF activated from ATALR is helpful for resource utilization of asbestos tailings, in order to improve ecological environment in the asbestos mine town and promote cement-based material development.