David C. Lynch

Hydrogen control of carbon deposit morphology

Abstract Carbon deposit morphology during catalytic disproportionation of CO is dependent on a number of variables. Hydrogen has a significant effect on the form of carbon deposited. It is proposed that the effect of hydrogen is to cause (or allow) open forms of carbon such as filaments to be produced. Hydrogen atoms serve to satisfy valences at the free edges of graphite planes. Without hydrogen, carbon will deposit in closed forms such as shells and nanotubes.

Catalytic disproportionation of CO in the absence of hydrogen: Encapsulating shell carbon formation

Abstract The catalytic disproportionation of CO in the absence of H2 resulted in carbon depositing as a lamellar form of graphite on the surface of the catalyst metal particles, as opposed to the filaments more commonly discussed in the literature. Carbon deposition on supported Ni and Co catalysts was investigated using TEM. The mechanism for this form of carbon deposition, and the tendency for specific numbers of layers of carbon to deposit on the specific catalyst metals, is discussed. It is stressed that some form of hydrogen must be present in order for filaments to form. Metal dusting of the catalyst caused by filament growth might be avoided by lamellar deposition, improving catalyst longevity. For regeneration of catalytic activity, the Boudouard reaction was used to remove deposited carbon from the catalyst surface.

Evaluation of the behavior of selenium in silicate slag

The solubility of Se in silica saturated iron silicate slag was examined at 1458 and 1523 K using a static distribution technique. The procedure involved equilibrating slag with a molten Cu-Se alloy. The final Se content of both the slag and metal phases was determined using hydride generation in conjunction with atomic absorption. The slag specimens were also analyzed for their ferrous and ferric ion content. The results of this investigation indicate that the solubility of selenium in slag increases as the Fe2+/Fe3+ ratio increases, and that the solubility is constant at lower values of that ratio. These results are consistent with the model proposed by Nagamoriet al.1,2 In that study selenium is postulated to exist in both a neutral state and as an Fe-Se complex. In this work a method is presented whereby one can evaluate the nature of Fe-Se complexes. Analysis of the data obtained in this study, and the data obtained by Nagamori and co-workers, suggests that the Fe-Se complex has an Fe/Se ratio of approximately 1∶2. This study also presents a method, for calculating the fraction of neutral selenium present in slag.

Thermochemical nature of minor elements in copper smelting mattes

AbstractEquilibrium distribution measurements of As, Sb, and Bi between molten copper and white metal were conducted at 1473 K using a static system. The results of this investigation have been used to evaluate the activity of those elements in white metal, and the results are compared to other data in the literature. An empirical model is presented and used to correlate the activity of As and Sb in matte as a function of the number of vacant electronegative sites in the matte, VS, and a parameter, ψ, used to represent the strength of the bond between Fe and the minor element in comparison to that which occurs with Cu. The activity coefficients of As and Sb in matte were found to be represented by the following equations:

PbO Solubility in Lead-Blast Furnace Slags

\log \gamma _{As} /\gamma _{As}^{SD = O} = - 0.256 + 93.0VS

Silicon refining process

\log \gamma _{Sb} /\gamma _{Sb}^{SD = O} = - 0.192 + 73.0VS