Fouling deposits recovered from depropanizer and debutanizer reboilers in three ethylene plants (A, B, C) were measured by elemental analysis, X-ray diffraction, infrared spectroscopy, pyrolysis, and ¹³C-nuclear magnetic resonance (NMR). The deposits contained organic compounds and ash, which was mainly Fe₃O₄. Elemental analysis indicated that the hydrogen/carbon ratios of the deposits were roughly equal at approximately 1.4 mol/mol, except for samples recovered from the reboiler not fed with high carbon number components and samples containing water. The deposits contained carbonyl functional groups, and the amount of oxygen varied. Molecular structure analysis of organic compounds in the deposits was conducted based on the results of pyrolysis measurement and NMR measurement. The molecular structure of the deposits in depropanizer reboilers in the plant C was estimated as the molecule composed of 1,3-butadiene and isobutene. The ¹³C chemical shift distribution of the molecule estimated by ChemDraw was very close to the distribution of the ¹³C-NMR spectrum. The molecular structure of the deposits in the depropanizer reboilers in the plants A and B was estimated as polymers composed of cycloalkene. The molecular structure of deposits in the debutanizer reboilers in the plants A, B, and C was estimated as cyclopentadiene and polymer containing ketones and carboxylic acids.

CO₂ methanation technology is attracting attention from the viewpoint of carbon circulation. This technology enables H₂ and the CO₂ extracted from flue gas to be used as raw materials to produce CH₄, and utilizes a catalytic reactor based on the Sabatier reaction. However, it is also known that the temperature of the catalyst layer rapidly increases at the initial stage of the reaction, and the sharp temperature increase becomes remarkable as the reactor becomes larger. Based on the issues above, in the present study, the reaction properties were firstly examined focusing on CO₂ conversion and the peak temperature of the catalyst layer for five kinds of catalyst using a double tubular reactor. As a result, the increase in the peak temperature is up to 143°C, and it was found that the peak temperature must be suppressed. Next, the authors made a prototype reactor with a catalyst thickness of 3 mm, in which the test gas and a heat medium are a crossflow, and attempted to reduce the peak temperature for the selected catalyst (METH^®134) having the lowest peak temperature. The result was the rise of maximum peak temperature was 23°C or less. The temperature was significantly lower compared to that of 48°C for the double tubular reactor. It was predicted that thinning the catalyst layer would be effective in reducing the peak temperature.

The present study investigates a method for selective separation and recovery of Au(III) from aqueous solution by using Noria, which is a ladder-type cyclic oligomer organic compound. The effect of solution pH on the solubility of Noria and the ability to reduce and recover Au(III) selectively from mixed solutions containing various metal ions were examined. Based on a series of experimental results, we attempted to develop a selective recovery process for Au(III).

pH adjustment enables the reversible dissolution and precipitation of Noria. It was elucidated that only Au(III) is reduced and recovered selectively as Au particles from the mixed solutions containing various ions of base metals and precious metals. Only the reduced Au particles could be recovered successfully, by the alkali dissolution of Noria containing Au particles. It was found that the Noria dissolved in an alkali solution can be regenerated as a reductant for Au(III) by an acid precipitation. It was thereby shown that there is a possibility of establishing an innovative Au(III) separation and recovery process using Noria.