Abstract
The aim of this study is to investigate the transformation of hydrogen-donor solvent tetralin in the direct liquefaction process of coal. Pure tetralin liquid as well as mixture of tetralin and Wucaiwan coal (WCW) were separately reacted under a liquefaction condition, and constituents of liquid product were analyzed by GC-MS. The results show that after the tetralin liquid reacts with high-pressure hydrogen, 90% of the reaction product is in liquid state, the gaseous products mainly include alkane gas and COx gas. When the reaction temperatures were set at 380 and 420°C, respectively, the corresponding transformation rates of tetralin can be 34.72 and 52.74%. At 380°C, the tetralin mainly plays a role of passing active hydrogen, while at 420°C, it mainly occurs dehydrogenation transformation to provide active hydrogen, as well as generate naphthalene, methyl indan, and substituted benzene, etc. Taking tetralin as the hydrogen-donor solvent, the WCW was performed liquefaction reaction, and the obtained results show that the transformation rates of tetralin are 69.76 and 83.86% at liquefaction temperatures of 380 and 420°C, respectively. Tetralin mainly occur to dehydrogenation transformation to generate naphthalene, followed by methyl indan, where contents order of main constituents of the liquefaction products were: naphthalene> tetralin > methyl indan.
Highlights
Direct liquefaction of coal is an effective measure for clean utilization of coal, which converts solid coal (H/C ratio ≈ 0.8) to liquid fuels (H/C ratio ≈ 2) by adding hydrogen (Ren et al, 2010; Vasireddy et al, 2011)
When the pure tetralin liquid reacts at liquefaction conditions, the tetralin mainly exists in a liquid state, while part of it may transform into gas and solid
In the reaction process of tetralin and high-pressure hydrogen, part of tetralin plays a role of transferring hydrogen, and the remaining part tends to provide hydrogen through its own dehydrogenation transformation
Summary
Direct liquefaction of coal is an effective measure for clean utilization of coal, which converts solid coal (H/C ratio ≈ 0.8) to liquid fuels (H/C ratio ≈ 2) by adding hydrogen (Ren et al, 2010; Vasireddy et al, 2011). It is vital to provide enough hydrogen in a timely manner to stabilize free radicals from coal pyrolysis for getting more liquid fuels and inhibiting coke formation in the direct liquefaction process (Shui et al, 2010). It has been found solvent as a media plays a very important role in liquefaction process of coal (Mochida et al, 1990; Xue et al, 1999; Yan et al, 2001; Zhang et al, 2009), such as dissolving, providing, and passing active hydrogen as well as stabilizing free radicals, etc. Studies have revealed that tetralin is a kind of excellent hydrogen-donor solvent
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