Liquefaction, natural yields

The present authors studied the solvolytic liquefaction process ( ,7) from chemical viewpoints on the solvents and the coals in previous paper ( 5). The basic idea of this process is that coals can be liquefied under atmospheric pressure when a suitable solvent of high boiling point assures the ability of coal extraction or solvolytic reactivity. The solvent may be hopefully derived from the petroleum asphaltene because of its effective utilization. Fig. 1 of a previous paper (8) may indicate an essential nature of this process. The liquefaction activity of a solvent was revealed to depend not only on its dissolving ability but also on its reactivity for the liquefying reaction according to the nature of the coal. Fusible coals were liquefied at high yield by the aid of aromatic solvents. However, coals which are non-fusible at liquefaction temperature are scarcely... 

Fundamental studies of coal liquefaction have shown that the structure of solvent molecules can determine the nature of liquid yields that result at any particular set of reaction conditions. One approach to understanding coal liquefaction chemistry is to use well-defined solvents or to study reactions of solvents with pure compounds which may represent bond-types that are likely present in coal [1,2]. It is postulated that one of the major routes in coal liquefaction is initiation by thermal activation to form free radicals which abstract hydrogen from any readily available source. The solvent may, therefore, function as a direct source of hydrogen (donor), indirect source of hydrogen (hydrogen-transfer agent), or may directly react with the coal (adduction). The actual role of solvent thus becomes a significant parameter. 

The engineering challenges include heat exchanger design, performance and accommodation of high pressures, temperatures and thermal stresses. If successfully developed the technology could be applied in the liquefaction of natural gas to provide a low-cost alternative to diesel fuel. So far one unit is reported built having a liquefaction capacity of about 35 kg/h. In this unit, 30% of the input natural gas stream was consumed as heat input, with a 70% yield of LNG. A future system with a capacity of about 700 kg/h LNG and with a projected liquefaction rate of 85 % of the input gas stream is under development. 

Conclusions When coal is contacted with a non-donor supercritical fluid a part of the coal instantaneously dissolves in the. supercritical fluid. The dissolved coal undergoes liquefaction reactions which are thermal in nature resulting in toluene soluble products being formed from coal. These products can subsequently undergo retrogressive reactions yielding insoluble material. Hence the toluene solubles show a maxima in conversion with time. 

Figures 2 and 3 contain yield curves for naphthalene and 1-methylindan as a function of reaction time for tetralin and tetralin plus coal, pyrite, or asphaltene. The asphaltene was a homogenized mixture of several samples isolated from coal liquefaction products during other work in our laboratory (9). This asphaltene sample contained essentially a negligible ash content (<0.1%). Therefore, it contains many organic structures similiar to those found in coal, but unlike coal, its reactions will be free of any complicating factors due to mineral matter. The yields of naphthalene and 1-methylindan are greater in the presence of asphaltene than in its absence, although not quite as high as in the presence of coal. This is additional evidence that these two products arise mainly from reactions associated with the presence of the organic portion of coaly matter. These reactions are quite likely free radical in nature.

Obtained data show that, the mixtures of the different types of the natural and synthetic organic polymers can be successfully converted with a high yield to light distillate fraction by pyrolysis under inert atmosphere and catalytic hydtopyrolysis in the autoclave conditions. The optimum tenqreiature of biomass / plastic mixtures conveision which coiresponds to the maximum yield of liquids is 390 - 400 C. In the CO liquefaction processes the interaction between products of natural and synthetic polymers thermal deconqwsition takes place. 

Again, it is necessary to proceed with caution when deriving molecular structures by mathematical manipulation of the data (Chapter 10) because of the complex nature of the liquid products. Nevertheless, these techniques do offer valuable primary information about these particular products, which, in turn, is of some assistance in understanding the means by which coal is degraded in, say, a liquefaction system and may therefore be of assistance in maximizing liquid yields. 

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