Yasumasa Yamashita

Influence of alkali on the carbonization process—I: Carbonization of 3,5-dimethylphenol-formaldehyde resin with NaOH

Abstract 3,5-Dimethylphenol-formaldehyde resin was carbonized with NaOH. It was found that as the amount of NaOH increases, the temperature of the hydrogen gas evolution is significantly lowered and its amount increases enormously. This is explained by the substitution reactions of H with NaO-groups followed by the condensation reaction after the liberation of NaoH. The tarry product almost disappears because of the formation of the network structure. At a higher temperature, the evolution of CO increases considerably with the addition of NaOH. The large weight decrease at this temperature range is related to this CO evolution and to the sublimation of reduced metallic Na. The catalytic action of alkali in the steam gasification of coal or carbon may be explained by such reduction of alkali with carbon, accompanied by evolution of CO, and by a following reoxidation of the reduced metallic Na with steam to form the alkali again, evolving hydrogen gas.

A study on carbonization of phenol-formaldehyde resin labelled with deuterium and 13C

Abstract The carbonization mechanism of phenol-formaldehyde resins has been studied by using three types of isotope-labelled resin, which hold 1. (1) deuterium atoms in hydroxyl groups, 2. (2) deuterium atoms in methylene groups, 3. (3) 13C atoms in methylene groups, respectively. The resins were carbonized in vacuum, and evolved gases were found to consist mainly of water at temperature below 400°C, whereas of water, methane, carbon monoxide and hydrogen above it. The isotope ratio was determined using a mass spectrometer. From the D/H ratio in water produced at temperatures below 400°C, it is concluded that the dehydration process involves two major reactions: a series of curing reactions and dehydration between methylene and hydroxyl groups. Also, from the 13 C 12 C ratio in methane and carbon monoxide produced from the 13C-labelled resin, it is suggested that methane comes mainly from the methylene groups, while carbon monoxide from the benzene rings. Using this information, the carbonization mechanism is discussed in detail.

Influence of alkali on the carbonization process—II: Carbonization of various coals and asphalt with NaOH

Abstract Four kinds of coal, one weathered coal and one petroleum asphalt, were carbonized with 120 wt% NaOH. With the addition of NaOH, the amount of hydrogen evolved increases enormously and the temperature of its evolution is lowered by 200–300°C. The reaction is thought to be a dehydrogenation resulting from the addition of NaO- to the active methylene groups or to aromatic nuclei, followed by liberation of NaOH, and causing some condensation reactions. At a higher temperature a large amount of CO evolves. This evolution is due to a reduction of Na2O or Na2CO3 produced in an earlier step of the reaction, with residual carbon.

Influence of alkali on the carbonization process—III: Dependence on type of alkali and of alkali earth compounds

3,5-Dimethylphenol-formaldehyde resin was carbonized up to 1000°C with various kinds of alkali and alkali earth compounds added. The hydroxides of Li, Na, K, Sr and Ba reacted with the resin to produce large amounts of hydrogen and CO. The order of reactivity was, Li <K <Na and Ca, Mg ⪡ Sr <Ba. Carbonates evolve only a small amount of hydrogen, although evolution of CO was very large. Carbonates cannot react with reactive methylene groups or aromatic hydrogens, whereas hydroxides easily substitute these hydrogens with MO-, liberating hydrogen atoms. The reduction of carbonate with carbon takes place in a similar way as that with hydroxides. The lower the melting point of the alkali or alkali earth compounds is, the lower the temperature of evolution of hydrogen is. This may be due to the good wettability of lower melting alkali or alkali earth compounds.

Studies on structural changes of coal density-separated components during pyrolysis by means of solid-state 13C NMR spectra

Abstract Solid-state 13 C NMR spectra of density-separated components of four coals were measured to obtain insight into the structural changes in maceral groups during pyrolysis. Each sample was pyrolyzed at 573–973 K in N 2 flow at a heating rate of 3 K min −1 . In all the coals, the lighter components underwent greater structural changes than the heavier components. For lower rank coals, the structure changed significantly between 623 and 723 K, indicating that aromatization of the aliphatic moiety or the elimination of aliphatic side chains began at 623 K, and the condensation of the aromatic moiety began at 723 K. Pyrolytic reactivity was lower in higher rank coals. Aromatization of the aliphatic moiety or elimination of aliphatic side chains took place to a greater extent in lower than in higher rank coals. After pyrolysis at 773 K, the fractions of each carbon, as measured by solid-state 13 C NMR, were similar in all samples, which indicates that all samples had the same first-order structure after pyrolysis. Most of the reactivity of each sample was related to the proportion of aliphatic moieties present in each sample. Thus, it is concluded that the content of aliphatic moieties in each maceral group determines its reactivity.

Modification of pitches by poly (vinylidene chloride) and poly (vinyl chloride)

Abstract Poly(vinylidene chloride) — PVDC — and poly(vinyl chloride) — PVC — reacted with pitches at elevated temperature with an increase in the yield of residual carbon; the greater the aromaticity and ‘fixed carbon’ of the pitch, the greater the increase. PVDC especially had a remarkable effect. This increase of residual carbon may be due to an increase in the molecular weight of pitch produced by its reaction with PVDC or PVC via dehydrochlorination. This tends to elevate the softening point and increase the insolubility in solvents. It is clearly indicated from i.r. spectra that reaction takes place mainly between aromatic hydrogen in the pitch and chlorine in PVDC. X-ray diffraction profiles of the reaction products show that the pitch forms hard (non-graphitizing) carbon as the PVDC content in the mixture increases.

Study on reaction characteristics of coal hydrogasification.

In order to estimate a suitable condition for the production of high calorie gas by the hydrogasification of coal, Taiheiyo coal was gasified continuously with hydrogen, and the yield of each product or the composition of gas produced was measured. The experiments were carried out under conditions of 714-775°C and 0-50 kg/cm2G. The feed rate of the coal ranged from 0.256 to 1.47 kg/hr and of hydrogen ranged from 0.113 to 1.059 m3/hr.The volume of methane produced was in the range of 0.2 to 0.3 m3/kg-coal, and it depended strongly on the feeding ratio of coal to hydrogen. The other factors, such as the hydrogen pressure and the coal feed rate, did not affect obviously on the evolution of methan. The yield and the viscosity of tar decreased with the residence time of gas in a reactor. The coal conversion was ranged from 0.38-0.55 kg/kg-coal and it depended on the feeding ratio of coal to hydrogen. The total heat value of the residual char was in good linear relation to the coal conversion.

Specific Heat of Coal and Heat-treated Coal

True and practical specific heat of coals (C% 70∼93) were measured continuously with adiabastic method. Practical specific heat includes heat of chemical reaction, heat of vaporization and heat of phase transition. The error of the measurments did not exceed over ±5 per cent. True specific heat increases with measuring temperature for individual coal and decreases as the rank of coal approaches to the graphite. The relation between true and practical specific heat shows that coal of C% 70 has exothermic reaction at the higher temperature range than 250°C. Especially, it shows maximum values at about 380 and 600°C. Coals of C% 75∼85 have exothermic reaction at 400∼500°C and at the higher temperature range than 600°C, and endothermic reaction at about 550∼600°C. Coal of C% 93 shows exothermic reaction at about 680°C and endothermic one at the higher temperature than 650°C. The mechanisms of reactions occuring at each temperature region were estimated from the decomposed gases and was examined if it is reasonable or not from the view point of the results obtained in this measurment.

Catalytic Depolymerization of Coals (I)

The principal objective of this study was to find a selective reaction that would depolymerize coal under mild enough conditions to permit recovery of the unaltered monomeric units.Depolymerization reaction with sulphonic acids-phenols was found to be effective.Various rank of coals were treated at various temperatures with p-toluene sulphonic acid in phenol.Extensive depolymerization occurred and the solubility in pyridine and benzene-ethanol increased.The molecular weight calculated from the saturated weight is 300-450, which agreed well with the values determined experimentally for the pyridine soluble materials. The OH content of the reacted coals also increased, but a dehydration reaction took place simultaneously.