Hiroshi Fujitsu

Reduction of nitric oxide with activated PAN fibres

Abstract The reductive removal of nitric oxide from flue gases by reaction with polyacrylonitrile-based active carbon fibres (PAN-ACF) activated with sulphuric acid has been studied at 423–632 K, using a circulating flow reactor. Nitric oxide (0.67 mmol) was completely removed via reduction with 1 g activated carbon under optimum conditions in 210 and 60 min at 423 and 623 K, respectively. N 2 was formed as NO was removed. Some oxygen remained on the carbon surface at 423 K, but was desorbed as CO or CO 2 on subsequent heating to 623 K. The bimolecular reaction of NO reduction over PAN-ACF, and the possible active sites of oxygen surface groups are discussed in the light of a kinetic study and a comparison of the fibre activation at different temperatures.

Catalytic activity of PAN-based active carbon fibre (PAN-ACF) activated with sulphuric acid for reduction of nitric oxide with ammonia

Abstract Catalytic activity of PAN-ACF activated with sulphuric acid was studied in a closed circulating reactor for the reduction of nitric oxide with ammonia at 423 K. Its activity was enhanced by activation to five times that of the original ACF, being the highest of the active carbons examined in the study. Influences of activation conditions in terms of the impregnation level of sulphuric acid and the activation temperature, and the adsorption ability of the fibre against nitric oxide and ammonia revealed that ammonia, irreversibly adsorbed on the acid sites provided by sulphuric acid after its proper evacuation, is the major reactive species for the reduction. Some activation of nitric oxide is also assumed on the oxidized site of the carbon surface for easier fission of its N-O bond, since NO decomposition is enhanced by activation with sulphuric acid. Activity decreased with repeated runs and is discussed from the point of view of products as poisons.

Selective synthesis of dimethylamine (DMA) from methanol and ammonia over zeolites

Abstract The selective production of dimethylamine (DMA) from methanol and ammonia was studied over some zeolites and metal oxides at a temperature range of 300 ~ 450 °C under ambient pressures. Proton or alkali-earth ion-exchanged zeolons were found to show considerable selectivity around 50% (product mole base) at 400 °C. The selectivity for the sum of DMA and monomethylamine (MMA) which can be recycled again for DMA production was over 85% at the conversion level of 90%, indicating effective suppression of trimethylamine (TMA) formation over the zeolite. The selectivity is discussed in terms of the type, strength, and steric environment of the acidic active sites. The activation of ammonia, desorption of DMA, and the shape selective discrimination of the pore structure for TMA can be factors for the selectivity.

Catalytic activity of coke activated with sulphuric acid for the reduction of nitric oxide

Abstract The catalytic activity of coke activated with sulphuric acid for the reduction of nitric oxide with ammonia at 150 °C was investigated. With the original coke the yield of nitrogen after 90 min reaction was only 10% and activation of the coke by the impregnation in sulphuric acid and subsequent heat treatment at ≈450 °C markedly enhanced the activity to a nitrogen yield as much as 70%. The activity decreased in repeated runs probably because of a surface coverage effect of the water produced, but the activity could be restored by further heat treatment at 400 °C.

The influence of modifications to the surface groups of brown coal chars on their flue gas cleaning ability

Abstract The preparation and performance of brown coal derived chars for flue gas desulphurization and denitrogenation were investigated. Starting materials were a commerical char produced from Yallourn briquettes and a high surface area active carbon produced from Loy Yang brown coal by potassium hydroxide treatment. It was found that modification of the commercial Yallourn char surface functionalities via sulphuric acid activation followed by ammonia treatment at 673 K produced a carbon with a higher denitrogenation activity than that of polyacrylonitrile-based active carbon fibre (PAN-ACF) and 60% of the desulphurization ability of the most active PAN-ACF. The high surface area Loy Yang carbon did not produce any significant increase in denitrogenation activity after identical pretreatment. This behaviour is believed to result from the low chemical reactivity of the high surface area carbon towards the pretreatment process.

Carbonization properties of partially hydrogenated aromatic compounds—I: Carbonization of partially hydrogenated pyrene prepared by Birch reduction

Abstract The carbonization properties of pyrene hydrogenated by Birch reduction to a variable extent were studied at 600°C under atmospheric pressure, in order to examine the influence of partial hydrogenation on the carbonization reactivity. Pyrene, which did not yield any coke, produced coke with flow texture after partial hydrogenation. Carbon yield of partially hydrogenated pyrene sharply depended on the hydrogenation extent. The intermediate stage of the carbonization pursued by hot-stage microscopy followed the steps of nucleation, growth and coalescence of anisotropic sphere. Considerable fluidity was observed at the final stage of mesophase development prior to the complete solidification where the benzene insoluble content exceeded 90%. The carbonization mechanism was discussed from the view of the polymerization of hydrogenated pyrene in relation with its structure.

Enhanced reactivity of some lignites by deashing pretreatment in hydrogen-transferring liquefaction under atmospheric pressure

Abstract The reactivities of five lignites were studied in the hydrogen-transfer liquefaction process undet atmospheric pressure, using a hydrogenated petroleum pitch (HA240). Although asphaltene yield from Yallourn brown coal was as high as 70%, other lignites showed inferior yields. Pretreatment in boiling 0.4N hydrochloric acid enhanced the liquefaction reactivity significantly to the extent that the asphaltene yield from Berga lignite increased to as much as 70%.

A kinetic study on the effects of support on the catalytic performances of RhSiO2, RhAl2O3, and RhTiO2 in a COH2 reaction

The catalytic hydrogenation of CO with hydrogen over RhTiO2, RhAl2O3, and RhSiO2 reduced at 673 K was studied kinetically and by monitoring the behavior of adsorbed CO species with in situ FT-IR to reveal the origins of their markedly different activities. The higher activity of RhTiO2 is related to the much higher reactivity of its irreversibly adsorbed CO against hydrogen. The reactivity of 17% of irreversibly adsorbed CO on RhAl2O3 was comparable to the rate of catalytic reaction, suggesting that its very limited portion is the reactive intermediate. The reactivity of the irreversibly adsorbed species on RhSiO2 was much less, indicating that the reversibly adsorbed species is the reaction intermediate. The rate of carbon deposition and its reactivity against hydrogen were much less than the rate of catalytic reaction, ruling out a major contribution to the catalytic sequence. Thus, the extent of CO activation which is strongly influenced by the supports is the basis for providing markedly different activities for these catalysts.

Catalytic graphitization of fibrous and particulate carbons

Abstract Catalytic graphitization of carbon fibers, carbon black and anisopropic mesophase spheres by chromia and chromium compounds was studied to examine the influences of the amount of catalyst, procedures of catalyst dispersion and heating on the extent of graphitization. Catalyst addition as a liquid solution provided better dispersion than mixing of powdered catalyst with the carbons by grinding, and permitted graphitization of intact carbon fibers. However, the catalytic action caused restructuring of the fibers and the carbon black. Sequential heat treatments at temperatures

Carbonization of coals to produce anisotropic cokes. 1. Modifying activities of some additives in the co-carbonization of low-rank coals

Abstract Using low-rank coals, the modifying activities of some petroleum, coal tar and aromatic hydrocarbon additives have been examined to find procedures for their utilization in the preparation of blast furnace coke. Petroleum pitch, especially after hydrogenation, exhibited excellent modifying activity even with non-fusible coals. In contrast, the activity of coal tar was very limited with such coals. The napththenic component, revealed by n.m.r. of the additives, appears to be important in the co-carbonization by inducing fusibility and anisotropic development in such coals. Co-carbonization to recover the dehydrogenated additives was attempted. However, there was no development of the anisotropy in the resultant coke by dissolution of the coal particles although the coal particles were firmly fixed in the matrix. Acid-refluxing treatment of non-fusible coals was found to enhance their modification susceptibility, indicating that some of the acid-soluble mineral matter is important in the thermal depolymerization or fusion process of the coal.