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Direct coal liquefaction residue (DCLR) could be extracted using dipropylamine (DPA) to afford extract with polycyclic aromatic structures, and the separation of extract and DPA as well as the recovery of DPA could be achieved by the nonthermal CO2-trigger at room temperature and atmosphere pressure, which would potentially gain huge energy savings. On the basis of preliminary single factor experiment, response surface methodology was used for optimizing DCLR extraction, and Box–Behnken experimental design was adopted, where extraction time, extraction temperature, and ratio of DPA to DCLR were chosen as the three independent variables, and extract yield was chosen as response variable. Among the three independent variables, DCLR extraction was mainly affected by extraction time and ratio of DPA to DCLR, and the two variables exhibited an interaction effect on the extract yield. The predicted extract yield would reach the peak under the optimized conditions, i.e., extraction time of 48 min, extraction temperature of 25°C, and DPA to DCLR ratio of 39 mL/g. In the practical experiment under the optimal conditions, the real extract yield was up to 29.42%, which was similar to the expected one. Response surface methodology proved to be applicable and useful for optimization of DCLR extraction. [ABSTRACT FROM PUBLISHER]

The effect of small molecular compounds in coal on quick direct coal liquefaction at high temperature was studied. The results showed that extraction with tetrahydrofuran just removed a portion of organic compounds, which were free or embedded in the macromolecular network structure in coal, without changing the macromolecular network of coal. However, removal of small molecular compounds in coal influenced the pyrolysis behavior and liquefaction performance of coal. The extracted coal exhibited better liquefaction activity in good donor solvent. The liquefaction conversion and yield of oils were higher than that of raw coal. The reason was that extraction with tetrahydrofuran made the relaxation of coal macromolecular network, and increased average pore size of extracted coal, which favored the diffusion of hydrogen-donating solvent into coal macromolecular network, thus increased the probability of collision of radicals and active hydrogen. The quick liquefaction experiment of extracted coal in poor hydrogen-donating solvents showed that the small molecular compounds played an important role as hydrogen donor during the quick liquefaction at high temperature without external active hydrogen resource. [ABSTRACT FROM PUBLISHER]

Tannin extract desulfurization technology is widely applied in China, however, in which there are sulfur-containing byproducts that can cause negative effects, such as reducing desulfurization efficiency and increasing operating cost etc. Thus, inhibiting side reactions and controlling byproducts is an important problem to be resolved. In this article, the cause of byproducts formation by thermodynamic analysis is reported. First, the reaction mechanism between HS−and pentavalent vanadium V(V) in desulfurization solution is researched, and it is conclude that HS−can transforms instantly into polysulfide ionsSx2−, thenSx2−forms the element sulfur. Thus,Sx2−is the main source to generate byproducts. Second, by calculating and comparing the Gibbs free energy change of side reactions, the results show thatSx2−is more active than HS−in solution and can react more easily with oxygen to produce byproducts. Therefore, quickening the transformation fromSx2−to element sulfur is a key measure to resolve the problem on side reaction. [ABSTRACT FROM PUBLISHER]