Reforming of methane and propane with supported Ni catalysts was investigated for the production of hydrogen for polymer electrolyte fuel cells (PEFCs). Supported Ni catalysts were prepared from Mg(Ni)–Al hydrotalicite-like compounds (HTlcs) as the precursor. The precursors were prepared by the co-precipitation method from nitrates of the metal components, thermally decomposed, and then in-situ reduced to form supported Ni catalysts. Ni2+ can effectively replace the Mg2+ site in the HTlcs, resulting in the formation of highly dispersed and stable Ni metal particles on supported Ni catalysts. Supported Ni catalysts prepared by this method showed higher activity than catalysts prepared by the conventional impregnation method such as Ni/α-Al2O3 and Ni/MgO. Moreover, the activity and stability of supported Ni catalysts were improved by combining a small amount of noble metals by adopting the "memory effect," which allows the reconstitution of the original hydrotalcite-like structure, and were effective for the production of hydrogen under the daily start-up and shutd-own operations.
Nanocelluloses with widths of <100 nm are prepared from abundant plant celluloses with or without chemical, enzymatic or physicochemical pretreatment by mechanical disintegration in water, and thus are bio-based and reproducible nanomaterials. In the 21st century, preparations and characterizations of various nanocelluloses and nanocellulose-containing composite materials have been extensively and intensively studied, and some of them have unique optical/mechanical/thermal/gas-barrier/catalytic properties applicable to high-tech material fields. In our laboratory, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidations of various polysaccharides including celluloses have been studied from 1995, and found to be the most efficient pretreatment for native plant celluloses to be converted to completely individual TEMPO-oxidized cellulose nanofibers (TOCNs) with homogeneous ∼3 nm widths and high aspect ratios. In this review paper, our recently reported papers concerning the following fundamental studies of fibrous TEMPO-oxidized celluloses (TOCs) and TOCNs are summarized and introduced: (1) determination of absolute molecular masses/molecular mass distributions of TOCs and TOCNs, (2) determination of aspect ratios of TOCNs from intrinsic viscosities of dilute TOCN/water dispersions, (3) simple and efficient surface hydrophobization of the originally hydrophilic TOCNs by counterion exchange treatments, and (4) preparation and characterization of transparent TOCN aerogels with low densities, high specific surface areas, low thermal conductivities and high mechanical performances.
Adequate information-gathering activities play a crucial role in making a rational decision under uncertainty in resource development. How adequate a particular information-gathering activity is can be quantified by using the concept of the value of information (VOI), which measures the possible increase of monetary value expected from an observation made by the information-gathering activity. In order to evaluate the VOI, one needs to model prior probability distributions for uncertain parameters, a monetary value function for each decision option, and a likelihood function representing the reliability of an observation. Among them, one often has little knowledge about a likelihood function, which is thus difficult to model. In this paper, we study the effects of likelihood functions on the VOI analysis in the context of resource development. Through numerical experiments, we show how the VOI is affected by the choice of a likelihood function. Moreover, we discuss how to include unknown bias of an observation in the definition of the VOI, and show its effect on the VOI analysis.
A criterion using the average amount of information, entropy of primary variables is developed in order to determine convergence of optimization calculations by the iterative Latin hypercube sampling (ILHS) as the multi-point search. In the ILHS, lengths of sample spaces are decreased as the process of optimal solution search advances. In this research, convergence of the optimization process is evaluated by calculating entropy of sample space length. Specifically the difference between normalized entropy and binary entropy function (BEF), "dη" is calculated and evaluated. The criterion is validated by well placement optimization problems about CO2 geological storage. The number of function evaluations is decreased by 70 to 80 %, keeping optimal solutions after the criterion is applied. Additionally, the criterion is available for problems including both continuous and dummy variables, which have a different convergence behavior.