| 简介 |
FIELD : chemical or physical processes.
SUBSTANCE : present application relates to a highly stable magnesium-modified molecular sieve of type Y, to its production and to a catalyst containing same. Magnesium-modified molecular sieve of type Y has content of oxides of rare-earth elements of 4 to 11 % by weight, content of magnesium oxide of 0.1 to 4 % by weight, sodium oxide content of 0.3 to 0.8 % by weight, a total pore volume of 0.33 to 0.39 ml/g, a percentage of the pore volume of secondary pores having a pore size of 2 to 100 nm, and total pore volume, constituting a modified Y-type molecular sieve of 10 to 30 %, a crystal lattice constant of 2.440 to 2.455 nm, percentage ratio of content of non-framework aluminum and total content of aluminum of modified molecular sieve of type Y, which is 13–19 %, and temperature of destruction of crystal lattice, component of not less than 1045 °C. Method of producing a magnesium-modified molecular sieve of type Y includes the following steps : (1) contacting the NaY molecular sieve with a solution of salts of rare-earth elements for an ion exchange reaction to obtain a rare-earth element-modified molecular sieve of type Y, having reduced content of sodium oxide; (2) calcining the molecular sieve of type Y obtained in step (1) at temperature of 350 to 480 °C, in an atmosphere containing from 30 to 90 vol. % steam, for 4.5 to 7 hours to obtain a molecular sieve of type Y, having a reduced crystal lattice constant; (3) contacting and reacting the molecular sieve of type Y obtained in step (2) with gaseous silicon tetrachloride to obtain an ultra-stable molecular sieve of type Y having a high content of silicon under the following conditions : weight ratio of SiCl4 and molecular sieve of type Y, in terms of dry substance, making 0.1 : 1 to 0.7 : 1, reaction temperature making from 200 to 650 °C, and reaction duration of 10 minutes to 5 hours; and (4) modifying the ultra-stable Y-type molecular sieve having a high content of silicon dioxide, obtained in step (3), with a magnesium compound to obtain a magnesium-modified Y-type molecular sieve.
EFFECT : increased activity of cracking of heavy oils and improved selectivity with respect to diesel fuel.
20 cl, 6 tbl, 24 ex |
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