The effect of the initial water of lignite on its liquefaction reactivity
In this paper, the effect of different initial water content of lignite on its direct liquefaction reactivity was studied. The results show that: initial water content in lignite can be used as hydrogen supplier and promote direct liquefaction reaction inducing higher total conversion rate, higher oil yield and lower pre-asphaltene / asphaltene yield, when the water content of lignite is of 20 ~ 30%. And the maximum of total conversion rate and oil yield is achieved 85.12% and 51.72%, respectively, when the water content of lignite is 25.33%. While the gas product yield and the pre-asphaltene /asphaltene yield is relatively lower, which is of 11.16% and 3.93%, respectively. This can be of practical significance to optimize the coal pre-treatment technology of direct liquefaction industry.
INTERACTIVE EFFECTS BETWEEN SOLVENT COMPONENTS : POSSIBLE CHEMICAL ORIGIN OF SYNERGY IN LIQUEFACTION AND COPROCESSING
The traditional mechanism for coal liquefaction ties liquefaction ability of a solvent with its scavenging ability and cannot explain synergistic effects between solvent components. Such effects are naturally anticipated by mechanisms that involve interaction between components to generate reactive components. This paper discusses three recent papers, in which beneficial effets of adding nondonor species to the donor solvent were reported, in light of the solvent-mediated hydrogenolysis model for coal liquefaction-a model we have previously proposed. The nondonor species, which in these cases are polycyclic aromatic hydrocarbons, are good acceptors of hydrogen and react with hydroaromatic donors to give cyclohexadienyl radicals, which are capable of engendering hydrogenolysis, thereby increasing the overall rates. The PCAH species also help minimize wasteful transfer of hydrogen that would otherwise lead to reduced but uncleaved products. In this case the beneficial effect is reflected in the efficiency of hydrogen utilization. Finally, we extend this line of reasoning to the context of coprocessing coals and heavy oils. We use semiquantitative estimates for the fate of aliphatic radicals in the presence and absence of PCAH components to suggest that the PCAH components provided by coals convert aliphatic radicals, which are ineffective in causing bond scission, into cyclohexadienyl radicals that can do so
Cognitive Correlaretes of Physics Achievement of Some Nigeria Senior Secondary Students
Some cognitive correlates of physics achievement of some Nigeria senior secondary students were considered in the study. Specifically, the study examined the relationship between measures of student’s field independency. Cognitive tasks, formal reasoning and their achievement in physics. Purposive and stratified random sampling techniques were employed to obtain a sample of 524 senior secondary two students from six education zones in Kogi State of Nigeria. Three instruments were used. They are science Reasoning Tasks (SRTs). Group Embedded Figures Test (GEFT) and Physics Achievement Test (PAT). Data analysis using multiple regressions reveals that measures of students’ fields’ independency and cognitive tasks predicted student’s achievement in physics generally. However, only measure of field independency predicted students’ achievement in physics in the higher order cognitive demand questions. Measures of formal reasoning had no significant relationship with students’ achievements in physics generally or in higher order cognitive demand questions in physics. However, the overall relationships between measures of field independency, cognitive tasks, formal reasoning and students’ achievement in physics generally and in higher order cognitive demand questions in physics were both significant. Educational implications of these findings were discussed.