Boleslaw S. Ignasiak

Polymeric structure of coal. 1. Role of ether bonds in constitution of high-rank vitrinite

Abstract Results of detailed studies on molecular weights of products from reductive alkylation of high-rank vitrinite are reported. It is concluded that the macromolecular network of vitrinite from a Cretaceous bituminous coal is composed of relatively small units (no. av. mol. weight 600–700) which are primarily linked by ether oxygen. A significant portion of these units (≈20 weight percent) is characterized by molecular weight substantially below 500. These findings seem to be consistent with results from mild hydrogenolysis and air oxidation of bituminous coals.

Polymeric structure of coal. 2. Structure and thermoplasticity of sulphur-rich Raša lignite☆

Abstract The methods of reduction and reductive alkylation with potassium in tetrahydrofuran and sodium in liquid ammonia have been applied to sulphur-rich, highly fluid (in carbonization) Rasa lignite. The results indicate that solubilization of coal by alkylation of the coal anion formed in liquid ammonia is a clean and defined process. It is concluded that the highly thermoplastic properties of Rasa coal result mainly from cleavage of CSC(COC) bridges, low contents of OH and lack of SH groups. In contrast to ‘normal’ bituminous coals investigated until now and characterized by wide distribution of the molecular weight of clusters formed on cleavage of ether bridges, about 80% (w/w) of Rasa lignite is built of units of almost uniform molecular weight (MW 500).

Oxidation studies on coking coal related to weathering. 3. The influence of acidic hydroxyl groups, created during oxidation, on the plasticity and dilatation of the weathered coking coal

Abstract A high-volatile bituminous coal possessing a high Gieseler fluidity and large dilatation was subjected to slight oxidation in air under chosen conditions. The resultant ‘oxycoal’ was treated with various chemical reagents in order to determine to what extent the original caking properties of this coal, as measured by Gieseler fluidity and dilatation, could be restored. Treatment with aqueous barium hydroxide or barium acetate solutions succeeded in doing so to a considerable degree. It is tentatively concluded that certain acidic hydroxyl groups formed in the course of oxidation are indirectly responsible for the deterioration of fluidity and dilatation — possibly via condensation reactions involving the hydroxyl groups — during subsequent pyrolysis of oxycoal. The presence of carboxyl groups appears to have no effect.

Polymeric structure of coal. 3. Re-examination of the role of ether bonds in reduction of molecular weight of a low-rank vitrinite treated with hydrogen donor☆

Abstract Although available literature does not unequivocally establish the presence of open ether bonds (ROR) in low-rank bituminous coals, formation of low-molecular-weight products on reacting such coals with hydrogen donors is usually interpreted in terms of scission of ether bridges. This lack of consistency could be justified by supposing that ethereal and hydroxyl functions in low-rank coals exist in phenoxyphenol-type structures. Ethers of this type have never been cleaved on treatment with sodium in liquid ammonia but, contrary to expectations based on extant literature, can be split by certain hydrogen donors. The results presented here indicate, however, that phenoxyphenol-type ethers do not exist in low-rank vitrinite and/or their cleavage does not result in lowering the molecular weight of the vitrinite. It is concluded that, unless non-reactive oxygen exists in low-rank vitrinite in dialkyl ether structures, formation of low-molecular-weight products on hydrogen donor treatment should be attributed mainly to CC bond cleavage.

Selective agglomeration of coal: analysis of laboratory batch test results

The results of 206 batch laboratory tests on selective agglomeration of three coals are reported. The effectiveness of the agglomeration process is analysed with the use of some new indices describing rejection of sulfur and mineral matter as well as recovery of coal matter. The influence of the process variables was examined by multiple linear regression. Correction calculus for measurement errors was used to estimate the accuracy of the experimental results.

Distribution of chemisorbed oxygen in mildly oxidized caking coal

Abstract A high-volatile A bituminous coal was oxidized with 18 O 2 at 100 °C for 72 h and the resultant ‘oxycoal’ heat-treated at atmospheric pressure and in vacuo at temperatures up to 430 °C. The 18 O content was determined in the ‘oxycoal’ before and after heat treatment, and in extracts and residues obtained from chloroform extraction of heat-treated ‘oxycoal’. In addition, unheated ‘oxycoal’ was extracted with pyridine and chloroform, and [ 18 O] was measured in the α-, β- and γ-fractions. The results support the view that decreased yields of chloroform-soluble matter (and corresponding loss of plasticity) associated with oxidation are mainly due to condensation reactions which reactive oxygen-bearing groups undergo during heat treatment, and that the extent of these reactions is markedly sensitive to pressure.

Application of non-reductive alkylation in liquid ammonia to studies on macromolecular structure of coals and bitumen-derived asphaltene

Abstract The reaction of non-reductive ethylation of a coal anion generated in the presence of a strong base (sodium and/or potassium amides) in liquid ammonia is an efficient method for coal solubilization. Under the reaction conditions used, over 50 wt % of vitrinites separated from carboniferous bituminous coals became soluble in chloroform. The chloroform extracts were characterized by relatively low molecular weights ranging from 600 to 12000. At the same time, Athabasca oil sand asphaltene, which, under reductive conditions, degrades relatively easily to lower molecular weight species, did not display any molecular weight changes on reacting with amides in liquid ammonia. This fact stresses the non-destructive character of non-reductive alkylation. It appears, therefore, that the molecular weights of chloroform soluble portions of ethylated vitrinites reflect the molecular size of the original vitrinites. These results contradict the concept of coal having a highly crosslinked macro-molecular structure.

Petrographic composition and liquefaction behaviour of North Dakota and Texas lignites

Abstract Two US lignites (from Texas and North Dakota) were fractionated by density with appropriately prepared mixtures of liquid halogenated and non-halogenated hydrocarbons. Petrographic analyses confirmed that the procedure resulted in density fractions enriched in specific macerals. Liquid yields obtained upon solubilization at 430 °C and 5.5 MPa hydrogen pressure decreased with increase in the density fraction for both lignites. On plotting the total solubilities of lignites and their density fractions versus their huminite contents a reasonably good linear correlation was obtained (particularly for North Dakota lignite). It is tentatively concluded that in North Dakota lignite, as opposed to Texas lignite, macerals other than huminite did not significantly contribute to generation of liquid products.

Structural characterization of non-reductively ethylated coal by 13C and 1H n.m.r.☆

Abstract A major portion of some coals can be solubilized by non-reductive ethylation. A part of the solubilized portion of a bituminous highly caking coal was studied by 1 H and 13 C nuclear magnetic resonance techniques. It was demonstrated that important structural information can be obtained by this method for the original insoluble material in coal. It was found that, in the investigated coal, about 40% of the aromatic carbon atoms are protonated and that 6–10% of total carbon atoms existed in original coal as active sites that were amenable to ethylation.

Selective Agglomeration During Pipelining of Slurries

Agglomeration of coals in a pipeline, using bridging liquids comprised mainly of bitumen, heavy oils and some inexpensive additives, has been investigated. Very encouraging results were obtained for low rank thermal coals. The potential of the pipeline agglomeration method for simultaneous beneficiation and hydraulic transportation of coal agglomerates is discussed in the context of immense Alberta reserves of subbituminous coals and low quality oils