Sdudy On The Technology Of Coal Wax Cracking To Alpha Olefins

Because the huge market of alpha olefins, the research on the production technology of alpha olefins drew great attention increasingly by the research institutions and enterprises. And further optimization of the wax cracking technology for alpha olefins had become one of the main directions in China. At the same time, the research development and preliminary industrial test of the coal liquefaction technology were taken in the last few years. As the by-product of coal liquefaction, how to make full use of the coal liquefaction wax also received extensive attention. In this article, the laboratory tests of cracking were carried out using 54# semi-refined wax and coal wax, and the detailed cracking conditions and the yield and distribution of the product were investigated.Steam cracking experiments were carried out at a small scale device using 54# semi-refined wax as raw material. The effects of temperature, residence time and steam to wax ratio on the yield and distribution of the product were investigated and the optimum cracking conditions were observed. The reliability of experiment results obtained from the cracking apparatus was identified by comparing the results with those of industrial process. The optimum cracking conditions of 54# semi-refined wax were found as follows:preheating temperature of 530℃, cracking temperature of 670℃, residence time of 2.5s, steam to wax ratio of 16%. Under these conditions, the yield and selectivity of a-olefins reached to 18.6% and 62.3% respectively.On the basis of the cracking conditions of 54# semi-refined wax, the influences of the technological conditions of three coal liquefaction wax on the yield and composition of liquid olefins were observed. After the comparison of 1# and 2# coal cracking, the yield and quality of liquid olefins were analyzed with 54# semi-refined wax, and the reasons of these differences were also determined. By contrast of 54# semi-refined wax, the yield of coal liquefaction wax had obvious advantages, but the content of liquid olefins was lower relatively, and the diolefins and alkane content was higher. On their optimum conditions respectively, the alpha olefins yield of 1# and 2# wax was higher 16 and 10 percents than 54# semi-refined wax respectively, and the selectivity lower 13 and 17 percents respectively. Through the contrast of the cracking results between several waxes cracking in the laboratory and the industrial experiment, the original industrial plant could be used for the cracking of coal liquefaction wax. To improve the product of coal liquefaction wax, the waxes could be sweated or solvent to take off oil, distillated and hydrotreated. At last, the theory basis of the optimum conditions could be explained from the aspect of dynamics. Though carbon number distribution research of the product from wax cracking, ethylene, propylene and C4～18 alpha olefins could be separated. They could be widely applied in polyethylene, monomer in polyethylene, PAO and AOS, etc.