Study On Chloride Removal Of Waste Plastics Cracking Oil By Hydrogenation

Waste plastics cracking oil is a kind of liquid fuel produced by the catalytic cracking of waste plastics.The emergence of technologies for converting plastic waste to oil not only helps reduce the ecological environment pollution,but also facilitates the sustainable development and utilization of resources.However,due to the inevitable existence of PVC in the raw material resources,the chlorine content in cracking oil exceeds the standard seriously,which will have an adverse effect on subsequent processing and utilization.Therefore,it is of practical significance to conduct research on the purification and removal of chloride in waste plastics cracking oil.This paper tested the basic properties of waste plastics cracking oil firstly,found that except high content of chlorine,it also contained a certain amount of sulfur,nitrogen,oxygen,and metal elements like iron and calcium;the distillate with boiling point below 350?accounted a large proportion through distillation at atmospheric pressure;the distribution of chlorine content in various distillates indicated that the feedstock mainly contained low-boiling point organic chlorides,and which mostly concentrated in gasoline fraction with boiling point below 200?;the types of organic chlorides in three distillates were identified by using GC-ECD method and found 13 typical organic chlorides mainly including trichloroethylene,tetrachloroethylene,1,1,2,2-tetrachloroethane and 1,2,4-trichlorobenzene etc.The quantitative analytic results also confirmed that most organic chlorides could be identified.Secondly,the hydrodechlorination experiments using waste plastics cracking oil as the feedstock was carried out.Compared the performance of different hydrogenation catalysts and investigated the effect of the reaction process conditions on the dechlorination effect systematically by conducting Orthogonal experiments and single-factor experiments separately.The experimental results showed that increasing the reaction temperature,increasing the reaction pressure,decreasing the space velocity,and increasing the ratio of hydrogen to oil all helped to promote the hydrodechlorination reaction of the waste plastics cracking oil.The suitable reaction process conditions were a reaction temperature of 340–360?,a reaction pressure of 4–5MPa,a space velocity of 1.0–1.5h-1 and a ratio of hydrogen to oil of 600:1–800:1,all the removal rates of chloride in the feedstock could reach above 97%;then,in order to find the reason for the catalyst activity decreased too fast in the hydrodechlorination process,XRD,BET,ICP and other methods were used to characterize and analyze the hydrogenation catalyst before and after its use.It was found that the active metal component did not show serious chlorine poisoning.The main reason for the deactivation might be that the metal elements such as iron and calcium from the feedstock and unsaturated hydrocarbons caused carbon deposited on the catalyst surface to cover the active sites of the catalysts.Finally,the refining treatment of the residual chloride in the hydrodechlorination products of the waste plastics cracking oil by adsorption was studied.The static adsorption experiment method was used for selecting and preparing the highly effective adsorbents.Defined the suitable adsorption conditions which were a mass ratio of adsorbent to oil of 1:10,an adsorption temperature of 40?,an adsorption time of 4hours,and a shaking frequency of 120r/min,the dechlorination rate and equilibrium adsorption chlorine capacity could reach 69.57% and 0.40mg/g under these conditions.The results of ion exchange modification studies by different metal elements showed that the removal rate and equilibrium adsorption capacity of adsorbents by Ce⁴⁺modified were both increased,the dechlorination rate and equilibrium adsorption chlorine capacity rose to 80.99% and 0.47mg/g respectively.The regeneration experimental results showed that the regenerative stability of the adsorbents after Ce⁴⁺modification was also improved compared with unmodified samples.