Liquefaction yields

The significant liquefaction yields that are presumed to have been derived from some macrinite-rich samples may attest to a contribution to conversion from this maceral. However, results from durains, and splint and cannel coals, which may contain large amounts of macrinite, generally have been variable (50). The conversion which we achieved with a coal containing 21% macrinite indicated that there was a contribution to the liquid products of batch hydrogenation from this maceral. Further, the residues examined from runs made with this coal at a series of temperatures contained no distinguishable macrinite product once a temperature of 425°C had been reached (66). 

In the present study, the liquefaction activities of pyrene, its derivatives, and decacyclene with coals of several ranks are studied to ascertain the previous ideas of liquefaction mechanism and to develop novel liquefaction process under atmospheric pressure. The coals used in the present study are non-fusible or fusible at relatively high temperature, and then gave small liquefaction yield with pyrene of a non-solvoly-tic solvent at 370°C. 

L.Y.=Liquefaction Yield(%) L.E.=Liquefyinq Efficiency (%) reaction temp.=390°C... 

Figure 1. Liquefaction yields vs. maximum fluidities in the fused state of coal (%), solvent (SRC pitch benzene soluble) (O), pyrene ((B), no solvent. Coal.sol-vent ratio = 1 3 reaction temperature = 390°C(8).

Figure 2. Effect of reaction temperature on coal liquefaction yield. Coal = It-mann solvent = decacyclene solvent.coal ratio = 3 1.

L.Y.=Liquefaction Yield L.E.=Liquefying Efficiency n =number of hydrogen atoms... 

The fusible coals can give a high liquefaction yield if the high fluidity during the liquefaction is maintained by the liquefaction solvent to prevent the carbonization. The properties of the solvent required for the high yield with this kind of coal are miscibility, low viscosity, radical quenching reactivity and thermal stability not to be carbonized at the liquefaction temperature as reported in literatures (12). 

In contrast, the non-fusible coal requires the solvation (extraction) or solvolytic reaction to be liquefied. The solvation of non-polar organic compounds including the pitch may be rather limitted, so that the solvolytic reaction is necessary for the high liquefaction yield between the coal and the solvent. 

Transalkylation might be expected another kind of the solvolitic reaction. However, the present results suggest low probability with alkylated pyrenes as suggested by the NMR analyses. Instead, the increased polarity by alkyl group or the enhanced reactivity of the carbonization precursor from alkylpyrene, especially ethylpyrene, may be responsible for a considerable liquefaction yield. The recovery of the solvent becomes difficult by its latter conversion as observed in the present study. 

Our initial conclusion from the FT-IR data on the residua is that it is the reduction in the carboxyl concentration which is most important to the improvements brought about by preliquefaction, and this reduction requires the catalyst but not the solvent and probably not the hydrogen. The major reasons for these conclusions are 1) pretreatments dry, with naphthalene (with hydrogen and nitrogen) and with tetralin, all reduced the carboxyl concentration, and the dry and naphthalene cases both produced improved liquefaction yields 2) the presence of hydrogen does not appear to make much difference between HC 1401-350 and NC 1401-350 and 3) the increased aromatics were not present in the dry preliquefaction residue (HCD 1401-350) and so, do not appear necessary for the improvement in liquefaction. 

Fig. 5. Liquefaction yields for donors of variable composition at 450°C and solvent/coal weight ratio of unity, (a) 1,2,3,10b-tetrahydrofluoranthene 4HFI (b) 1,2,3,4,5,6,7,8-octahy-droanthracene 8HAn (c) 1,2,3,4,5,6,7,8,9,10,11,12-dodecahydrotriphenylene 12HTp ...

Fig. 6. Influence of solvent/coal ratio on the liquefaction yields with different donors. Oil + asphaltene (4HF1), (8HAn) oil A (4HF1), O (8HAn) (3) gas (C) preasphaltene ( ) residue.

Active enough to give a high liquefaction yield but not active enough to reduce phenolic materials extensively to neutral alcohols and hydrocarbons. 

It is generally appreciated that the mineral matter associated with some coals may act as a catalyst for liquefaction. A common observation is that among bituminous coals from the eastern United States, those with a relatively high mineral matter content also provide relatively high liquefaction yields. Also, addition of coal-derived mineral matter increases the liquefaction yields from those coals with low mineral matter content. The involvement of pyrite in these effects has been fairly well established. The importance of clay and/or other minerals is less well defined. 

Table 2 Effects of heating rate and cooling rate on liquefaction yields of com stover. ...

Heating rate (°C/min) Cooling rate (°C/min) Liquefaction yield (% of total mass) Gas yield (% of the total gaseous products) ... 

Liquefaction yield (%) = (1 — weight of dried residue/dry weight of starting DDG) x 100... 

Liquefaction yield achieved by the liquefaction process were 80-98%, indicating that the selected liquefaction conditions, such as temperature, time, sulfuric acid content, and liquefaction solvent to DDG ratio, promoted the atmospheric pressure liquefaction process. These results are summarized in Table 1. Clearly, an increase in liquefaction time and temperature results in increased liquefaction yield. For instance, when the temperature was 160 °C, the liquefaction yield reaches 94.6% at 2 h, whereas further increase in temperature and time resulted in a depressed increase in liquefaction yield. A similar trend has also been observed in the case of liquefaction of com stover [3]. Typically, the increase of catalyst content should increase in the liquefaction yield. As can be seen in Table 1, 94.6% liquefaction yield was obtained at 3% sulfuric acid in 160 °C 2 h. However, the use of sulfuric acid will cause condensation of degraded residues and increase the viscosity of the liquefied materials. The amount of insoluble residue increased with decreasing liquefaction solventDDG ratio. When the liquefaction solvenl/DDG ratio reaches 5, the liquefaction yield is 97.8% after 2 h. A higher yield could be expected at even bigher liquelaction solvent/DDG ratio, but at the cost of more solvents or lower productivity. 

In an investigation that sought to clarify the effects of coal rank on liquefaction yields (106), a computer cluster analysis of some 100 U.S. coals... 

Earlier attempts to correlate the free radical intensity N of coals obtained in pyrolysis experiments with the liquefaction yields of coal were not very successful. For example, the work of Stenberg et al. in nine... 

The liquefaction yields in terms of product oil output is reported to be ca. 3 barrels per ton of coal feedstock in both Process 1 and 2. 

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