In this study, X-ray Photoelectron Spectroscopy (XPS) was used to analyze the elements on the surface of subbituminous coal , and reverse flotation was introduced to float subbituminous coal. The effect of ultra-fine coal on the flotation behavior of silica in coal reverse flotation was discussed by comparing the flotation performance with two different artificial mixed flotation feedings, with ultra-fine coal (UFC, −45 μm) or without ultra-fine coal. The comparison results showed that the existence of UFC reduced the flotation rate and the recovery of silica, as well as the separation efficiency of subbituminous coal reverse flotation. Compared to the flotation performance of feeding with UFC, the concentrate ash content of feeding without UFC was lower (9.18%), and the separation efficiency was higher (68.69%). Total Organic Carbon Analyzer was used to test the adsorption quantity of collector by coal and silica to explain the mechanism. Conclusions were obtained that ultra-fine coal particles could adsorb more collector due to their larger specific surface area, leading to less collector left in the pulp to float silica particles. Selective flocculation reverse flotation method could increase the separation efficiency of coal reverse flotation with appropriate dosage flocculant .
A novel and highly active magnetic solid superacid (MSSA) with extraordinary separable and recyclable properties was facilely developed by impregnating trifluoromethanesulfonic acid onto mesoporous zirconia coated ferroferric oxide nanoparticles . The extraction residue (ER) from Piliqing subbituminous coal was subjected to non-catalytic hydrocracking (NCHC) and catalytic hydrocracking (CHC) in cyclohexane over MSSA at 300 °C. Detailed molecular compositions of the soluble portions from NCHC (SP NCHC ) and CHC (SP CHC ) were characterized with a Fourier transform infrared spectrometer and gas chromatograph/mass spectrometer (GC/MS). As a result, the yield of SP CHC is remarkably higher than that of SP NCHC and most of the GC/MS-detectable compounds in SP CHC are arenes, while SP NCHC contains alkanes, arenes, arenols, and ketones , indicating that MSSA effectively catalyzed the cleavage of C ar -C alk bridged bonds connecting some aromatic rings (ARs) and side chains on some ARs in the ER. Di(1-naphthyl)methane (DNM) and 9-benzylphenanthrene (9-BP) were used as coal-related model compounds (CRMCs) and their CHCs were investigated to further probe the catalysis of MSSA in the CHC of the ER. The result suggests that MSSA is highly active for cleaving the C ar -C alk bond in the CRMCs and generating naphthalene and phenanthrene under mild conditions. Based on the exploration of controlling reactions, the catalytic mechanism was discussed. MSSA could be easily separated and still active for the CHC of DNM after 3-times recycle.
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