煤加氢液化铁催化剂的穆斯堡尔谱研究 Ⅲ.内蒙红旗褐煤液化中的一种新的活性相——γFe相

MOSSBAUER SPECTRASCOPIC STUDY OF IRON CATALYST IN COAL HYDROLIQUEFACTION Ⅲ.THE NEW ACTIVITY PHASE γ-Fe IN HONGQI BROWN COAL LIQUEFACTION

用穆斯堡尔谱考察以化学形式结合到煤中的铁催化剂和以物理形式外加等量铁催化剂对内蒙红旗褐煤加氢液化的催化活性,发现残渣中γ-Fe/Fe_(1-x)S比越大,液化产率越高,表明γ-Fe是一种较Fe_(1-x)S活性更高的新的活性相。离子交换煤中的Fe^(3+)离子由于粒度细小,分布均匀,易转化为γ-Fe相,因而具有最高的催化活性。

Chinese Hongqi brown coal was ground to pass 100 mesh sieve and repeatedly floated in CCl_4 to remove pyrite and quartz. The float-fraction was washed with 5% H_2SO_4 solution.A portion of it was washed with distilled water and is referred to as an acid-washed coal. Another portion was slurried with 0.2mol/l Fe_2(SO_4)_3 aqueous solution with a 30:1 weight ratio of solution to dry coal(pH=4.0), and stirred for 15 h. It was then filtered and washed with distilled water to constant pH. This is referred to as Fe-exchanged coal. Results of measurements showed that the iron contents of raw coal(sample 2~*), acid-washed coal and Fe-exchanged coal(sample 1~*) were 1.15%, 0.4%, and 1.11% respectively. Sample 3~* was prepared by adding 0.71% of α-Fe_2O_3 powder(100 mesh) to the acid-washed coal. The iron contents of samples 1~* 2~* and 3~* were approximately equal.Two grams of a given sample was mixed with 0.05g of sulfur and tested for liquefaction. Six milliliters of a mixed solvent(tetralin/α-methylnaphthalene=1/3) was used in each run. All microautoclave runs were carried out at 430℃ and 8.0 MPa H_2 for 45 min.Mossbauer spectroscopy is used to investigate the different iron species present in coal samples.The hydroliquefaction results show that higher coal conversion is associated with greater γ-Fe/Fe_(1-x)S ratio in coal. It Seems reasonable to conclude that γ-Fe possesses higher catalytic activity than pyrrhotite Fe_(1-x)S.The formation of γ-Fe species during liquefaction is related to the dispersion of iron in the coal. The more finely dispersed the iron in the coal is, the more γ-Fe species will be formed. Ironexchanged coal which has the highest iron dispersion, is the most active among the samples tested.