Research On The Hydrogen Supply And Hydrogenation Behavior Of Circulating Solvents During Direct Coal Liquefaction

Direct coal liquefaction(DCL)can not only use coal resources efficiently and cleanly,lessen oil import,safeguard national energy security,but also provide high-quality chemicals to promote economic development.With DCL developing and the research and improvement of hydrogen donor solvents(HDSs),breakthrough improvements have been made in the technology.A thorough understanding of the composition and properties of circulating solvents for DCL is the key to the preparation of HDSs with excellent capability.It is of great significance to improve coal conversion and oil yields.However,due to the complex composition of coal liquefaction solvents,there is currently a lack of indepth study of solvents.Taking tetrahydronaphthalene and naphthalene as references,the experiment selected several circulating solvents,and investigated the influence of alkyl side chain,aromatic ring number and isomerization on its hydrogenation ability during the hydrogenation and hydrogenation process of the circulating solvent.For the research on the hydrogen supply capacity of circulating solvents,two coal model compounds,benzyl phenyl ether and dibenzyl ether,were hydrogenated with various circulating solvents under nitrogen and iron-based catalysts.As temperature and time change,the hydrogen supply behavior of alkyl tetrahydronaphthalene and tetrahydronaphthalene and the model compound showed great consistency.Hydrogen donor performance of the circulating solvent increases as the number of rings increases.Both indene hydrogenation products have hydrogen donating activity,but the hydrogen donating performance of the two substances is lower than that of tetralin under the same conditions.Hydrocarbon bonding energy of different solvents is calculated by molecular simulation.It is found that the introduction of alkyl groups can effectively improve the hydrogen supply capacity of the circulating solvents.The experimental results are consistent with simulation calculations.For the hydrogenation process of a cyclic solvent,experiment investigated the effects of catalyst,reaction pressure,and temperature on the solvent hydrogenation process.The results show that a palladium-carbon catalyst has better catalytic activity than iron-sulfur catalysts and nickel-molybdenum catalysts;increasing reaction pressure and temperature can increase hydrogenation rate,but will reduce hydrogenation equilibrium conversion rate and promote the ring-opening reaction.Research on the hydrogenation experiment of 1-methylnaphthalene found that due to the influence of the methyl group,hydrogen is more likely to be added without methyl on the aromatic ring.At the same time,it was determined that 1-methylnaphthalene can obtain a more suitable hydrogenation reaction rate and conversion rate under the conditions of 320? and 3 MPa hydrogen initial pressure,and under this condition,44.15 wt%and 51.23 wt%of methyl-tetrahydronaphthalene or ethyl-tetrahydronaphthalene were prepared.In addition,the experiment compared the hydrogenation process of several groups of solvents.The results show that:monocyclic compounds have good hydrogenation ability under the catalysis of palladium-carbon at a lower temperature.With the increase of the number of rings,the hydrogenation ability of the circulating solvent gradually decreases,and the introduction of methyl groups will enhance the circulating solvent Hydrogenation capacity.