Studies On Catalytic Cracking Of Naphtha

With the rapid development of global economy, petrochemical industry has been in a high-speed growth period. In recent years, the rapid growth in demand for propylene derivatives especially for polypropylene stimulates the dramatic increase in demand for propylene in global scale. At present, the primary source of propylene is traditional steam cracking of naphtha and Fluid catalytic cracking, and steam cracking probably accounts for more than 60 percent in total production capacity with 34 percent of Fluid catalytic cracking. In recent years the catalytic cracking increasing the yield of propylene craft obtained a rapidly expand, because of having extensive feed stocks source and low production cost advantages. In some enterprises, naphtha may be used as catalytic cracking feed stock. But the study on catalytic cracking of naphtha for increasing low-carbon olefin has been rarely reported. The catalytic cracking of naphtha was explored on the pilot fluid catalytic cracking riser reactor. Influence of operating conditions temperature, residence time, catalyst to oil ratio or water-oil ratio on naphtha conversion and product distribution was investigated; the other three were kept unchanged. The results show that maximum propylene yields of naphtha catalytic cracking achieved at 17.22%, when LTB-2 catalyst was used, residence time was controlled at 3.4s, catalyst to oil ratio at 12, temperature at 600℃and without atomization water was injected. At the conditions, yields of dry gas and coke achieved 16.69% and 1.82%, conversion of naphtha achieved 51.06%.The impact of catalysts on naphtha catalytic cracking was investigated. The temperature was kept at 570℃, catalyst to oil ratio at 12 and without atomization water was injected, then naphtha conversion and product distribution were investigated respectively with LTB-2, LCC-2 and MLC-500 catalyst at the residence time of 2.6s, 3.0s and 3.5s. The results show that when LTB-2 catalyst was used maximum propylene yields achieved at 16.19%. At the same condition, yields of dry gas and coke achieved 10.97% and 1.09%, conversion of naphtha achieved 44.4%. An additives produced in was added in the LTB-2 catalyst with 20 percent, compared with pure LTB-2 catalyst at the same reaction conditions, the conversion of naphtha was increased 4.7 percentage points, propylene yield felt 5.77 percentage point, coke yield achieved 18.02%.The catalytic cracking characteristics of naphtha were compared with FCC gasoline. At the same operating conditions, both conversion and propylene yield for naphtha were lower than the FCC gasoline.