Liquefaction residue of Heishan bituminous coal (HLR) was subject to two hydroconversion reactions under 5 MPa initial pressure of hydrogen at 300°C for 3 h, without catalyst and with acid supported catalyst (ASC), respectively. The reaction products were analyzed with gas chromatography/mass spectrometer (GC/MS). The results show that 222 organic compounds were detected totally in the products and they can be divided into alkanes, aromatic hydrocarbons (AHCs), phenols, ketones, ethers, and other species (OSs). The yield of hydroconversion over the ASC is much higher than that without catalyst. The most abundant products are aromatic hydrocarbons in the reaction products from both catalytic and noncatalytic reactions of HLR. The yield of aromatic hydrocarbons in the reaction product from hydroconversion with the ACS is considerably higher than that from hydroconversion without a catalyst.
Direct coal liquefaction is a significant process for transforming coal to liquid fuel and chemicals, in which considerable coal liquefaction residue (CLR) is generated. The residue obtained by the process of direct liquefaction is about 30 wt% of raw coal [
Catalyst plays a very important role for cutting off the chemical bonds in the macromolecule structure of coal and solid acid is a kind of the important and efficient catalysts in direct coal liquefaction [
In this study, a kind of acid supported catalyst (ASC) was prepared and ASC-catalyzed hydroconversion of a CLR from Heishan bituminous coal was investigated.
The liquefaction residue of Heishan bituminous coal (HLR) was obtained by direct liquefaction under 19 MPa H2 at 455°C. The HLR was ground to <75
Proximate and ultimate analyses (
Proximate analysis | Ultimate analysis (daf) | ||||||
---|---|---|---|---|---|---|---|
|
|
|
C | H | N | O |
S |
0.19 | 21.64 | 39.07 | 75.09 | 1.29 | 1.36 | 24.42 | 3.79 |
Solvent cyclohexane and petroleum ether (PE) were commercially purchased and then distillated using a rotary evaporator (BÜCHI Labortechnik AG, Flawil, Switzerland). Activated carbon (AC) and antimony pentachloride (SbCl5) were commercially available. AC was ground to <75
1 g HLR, 0.4 g ASC, and cyclohexane (30 mL) were put into a stainless autoclave (60 mL volume) with magnetic stirrer. After being purged with N2 three times to remove air from the autoclave, the autoclave was pressurized with H2 to 5 MPa, then heated to 300°C at a rate of 20°C/min, and kept for 3 h. After that, in an ice bath, the autoclave was cooled rapidly. The reaction mixture which was thoroughly removed from the autoclave using PE as solvent was filtrated by a membrane filter with pore size of 0.8
The organic compounds in the reaction product were identified with gas chromatography/mass spectrometer (GC/MS; Hewlett-Packard Company, Hewlett-Packard 6890/5973) and quantified with gas chromatography (GC; HP 6890). Fourier transform infrared (FTIR) was collected at room temperature on a Nicolet Magna IR-560 infrared spectrometer. N2 adsorption-desorption isotherms were determined by an Autosorb-1-MP specific surface area and pore size analyzer at 77 K from Quantachrome Instruments Company to obtain pore volume, average pore diameter, and surface area of the AC and ASC.
As a comparison reaction, the procedure of noncatalytic hydroconversion (NCHC) is the same with the catalytic hydroconversion (CHC) but without any catalyst.
As Figure
FTIR spectra of the AC and ASC.
The yields of NCHC and CHC of HLR are 35.49% and 57.11%, respectively. Compared with the NCHC, the yield of CHC is remarkably improved. These data show that the ASC plays a significant role to promote the decomposition of HLR.
The reaction products from NCHC and CHC of HLR are simplified as RPNC and RPC, respectively. Figures
Alkanes detected in the reaction product from NCHC and CHC of HLR.
Peak | Compounds | NCHC | CHC |
---|---|---|---|
4 | Methylcyclohexane | √ | |
59 | Pentadecane | √ | |
70 | Hexadecane | √ | |
89 | Heptadecane | √ | √ |
106 | Octadecane | √ | √ |
107 | 8-Methylheptadecane | √ | √ |
128 | Eicosane | √ |
Phenols detected in the reaction product from NCHC and CHC of HLR.
Peak | Compounds | NCHC | CHC |
---|---|---|---|
22 |
|
√ | |
24 |
|
√ | |
32 | 3-Ethylphenol | √ | |
34 | 3,4-Dimethylphenol | √ | |
40 | 2-Ethyl-6-methylphenol | √ | |
47 | 2,3-Dihydro-1 |
√ | |
61 | 2,4,6-Triisopropylphenol | √ | |
118 | ( |
√ | √ |
119 | ( |
√ | |
167 | Chrysen-6-ol | √ | √ |
Total ion chromatogram of the reaction product from NCHC of HLR.
Total ion chromatogram of the reaction product from CHC of HLR.
As shown in Figure
Distribution of group components in the reaction products from NCHC and CHC of HLR.
As listed in Table
In total, 171 AHCs were detected in the reaction products, including 81 and 130 AHCs appearing from RPNC and RPC, respectively, as shown in Table S.1 (supplementary data). The yields of AHCs are 9.7 and 42.1 mg·g−1 (daf) and the relative contents are 73.0% and 82.5% in the RPNC and RPC, respectively. 14 homologues of benzene, 7 homologues of fluorine, 17 homologues of naphthalene, 7 homologues of anthracene, 6 homologues of phenanthrene, and 30 condensed arenes with carbon atoms number greater than 4 were found in the RPNC. AHCs detected in the RPC include 33 homologues of benzene, 9 homologues of fluorine, 26 homologues of naphthalene, 10 homologues of anthracene, 12 homologues of phenanthrene, 4 homologues of indene, and 36 condensed arenes with carbon atoms number greater than 4. Among them, the yield of benzoperylene (peak 175) is the most and the relative content is 13.4% in the RPC of HLR. Secondly, the relative content of 2-methylbenzoperylene (peak 221) is 10.4%. The AHCs in the RPC (42.1 mg·g−1, daf) are remarkably higher than those in the RPNC (9.7 mg·g−1, daf). Our previous investigation showed that
As exhibited in Table
Organic compounds of the reaction product from RPNC and RPC detected by GC/MS include alkanes, AHCs, phenols, ketones, ethers, and OSs. The yield of CHC is obviously improved compared with the NCHC and it shows that the ASC plays a significant role to promote the decomposition of HLR. Much more AHCs and phenols were released from RPC than those from RPNC. The hydroconversion of HLR under 300°C over the ASC not only provides an efficient approach for producing lots of value-added chemicals from the residue but also provides the information of macromolecular structures of the residue.
The authors declare that they have no competing interests.
This work was subsidized by the National Natural Science Foundation of China (Grant no. 21506248), the Basic Research Program of Jiangsu Province (Grant no. BK20130171), Fundamental Research Fund for the Central Universities (China University of Mining & Technology) (Grant no. 2013QNA16), the Scientific Research Foundation of Key Laboratory of Coal-based CO2 Capture and Geological Storage of Jiangsu Province (China University of Mining and Technology) (Grant no. 2015A03).