Modification Of Y Molecular Sieve And Its Research On Diesel Cracking Performance

In recent years,as the crude oil has become increasingly inferior,heavier,and the quality of clean oil has been accelerating,the contradiction between the increasing demand for chemical raw materials has become increasingly prominent.As the only technical means that can directly produce clean fuel and adjust products,hydrocracking has become the only way for refining and chemical companies to produce clean fuel or chemical products with high added value.The most important part of the hydrocracking process is the research and development of hydrocracking catalysts.The performance of the catalyst directly affects the quality of the processed products.Therefore,the research and development of hydrocracking catalysts is crucial.Y molecular sieve has a unique three-dimensional pore structure,and has suitable acidity,so it has become an excellent carrier for hydrocracking catalysts.Based on the industrial Na Y molecular sieve provided by Nankai Catalyst Factory,this thesis first investigated different ammonium exchange conditions(ammonium ion concentration,ammonium exchange time,and ammonium exchange times).The ammonium exchange process of the Y molecular sieve is the process of replacing the Na⁺ions on the molecular sieve with NH₄⁺ions.In this process,the Na⁺ions in the general Y molecular sieve super cage are first exchanged.As the degree of ammonium exchange further deepens,the Y molecular sieve The Na⁺ions in the sodalite cage are also exchanged.During the whole ammonium exchange process,the Na⁺ions in the Y molecular sieve hexagonal column cage are difficult to be exchanged.This is due to the small diameter of the hexagonal column cage and the inability of NH₄⁺ions to enter.The investigation results show that by controlling the concentration of ammonium ions,ammonium exchange time and ammonium exchange times,Na⁺ions can be replaced as much as possible under the premise of ensuring the stability of the Y molecular sieve framework structure,and the sodium content of the Y molecular sieve can be effectively reduced.On the basis of ammonium exchange,this thesis carried out calcination treatment of Y molecular sieve,and investigated the effect of calcination temperature on the structural stability of Y molecular sieve.The investigation results of the calcination treatment show that excessive high calcination temperature will cause the Y molecular sieve framework structure to collapse,so the calcination temperature should be controlled below 600?.In this paper,the hydrothermal treatment of Y molecular sieve was also investigated,and the effects of hydrothermal temperature,hydrothermal pressure and hydrothermal time on the pore structure,pore distribution,acidity(acid strength,acid type and acid amount)of Y molecular sieve were investigated.The investigation results of hydrothermal treatment show that the high-temperature hydrothermal treatment process of HY molecular sieve is the process of removing the framework aluminum of Y molecular sieve,and at the same time,the silicon atoms are inserted into the aluminum vacancies under the action of water vapor,which is a gradually stable process.In order to obtain a hydrocracking catalyst with excellent performance,the role of molecular sieve is very significant,so it is necessary to optimize the selection of hydrothermal temperature,hydrothermal time,hydrothermal pressure and other conditions in the process of hydrothermal modification of molecular sieve.Finally,the thesis carried out real oil evaluation experiments on the modified Y molecular sieve catalyst.The experimental results show that the catalyst prepared by screening the modified ultra-stable Y molecular sieve as the key cracking component has good hydrocracking performance.