Preparation And Properties Of Ethylene Glycol/diethylene Glycol Dehydration Catalyst

As an important chemical raw materials,1,4-dioxane is more extensive in the solvent,extractant,metal surface treatment agent,dispersant and other aspects of the application.With the depletion of oil resource,it is the domestic trend of development to replace oil with coal as raw material for the production of chemical products in recent years.As the synthesis of ethylene glycol glycol route has been gradually achieved industrialization,ethylene glycol production capacity will be more and more,It will be the current research focus on developing the downstream products of ethylene glycol downstream product and enhancing the economic benefits of product.The traditional industry mainly use sulfuric acid or phosphoric acid with ethylene glycol dehydration synthesis of 1,4-dioxane,this method is not only erodes the equipment,but the side effects is serious,and lead to the product yield is not high.at the same time,the method produces large amounts of waste acid wastewater,so the focus of this research is to develop a high activity,good stability and cheap environmental protection catalyst.Compared with traditional liquid acid catalyst,solid acid catalyst has the advantages of low production cost,good stability of catalyst,simple separation and recovery,no corrosion of equipment and environmental pollution.In this paper,the effects of activated carbon,SiO₂,?-Al₂O₃ on the dehydration performance of ethylene glycol were firstly carried out by using ammonium phosphate as the active component,and the experiment showed that the active carbon was the best catalyst for the catalytic activity.Then activated carbon was used as the carrier,and the effects of the active components on the dehydration performance of ethylene glycol were investigated by using the active component?NH₄?3PO₄,?NH₄?₂SO₄ and NiSO₄.It was found that the catalytic activity of?NH₄?₃PO₄ was the best.In this paper,?NH4_?3PO₄/AC catalyst was prepared by impregnating,drying and calcining with activated carbon as carrier and?NH₄?₃PO₄ as the active component.XRD,SEM,TEM,XRF,EDS,BET and NH₃-TPD were used to characterize the catalyst,and the results show that the active component in the phosphate activated carbon spread evenly on the surface,no burning phenomenon of crystallization,and no damage to the graphite structure of activated carbon.According to the results of XRF and EDS,the actual load and theoretical value of active component phosphoric acid are similar.According to the results of BET and NH₃-TPD,it can be seen that the specific surface area of activated carbon supported catalyst is mainly composed of micropores and mesopores,and the surface of the catalyst is mainly weak acid sites and strong acid sites.This paper using ethylene glycol as raw material,based on fixed bed reactor,the factors that affect the photocatalytic activity of catalyst is investigated,such as reaction temperature,space velocity,catalyst calcination temperature,loading of active components.The results indicated that under the optimal conditions of the reaction temperature was 270 ?,the reaction space velocity was 0.3h-1,the catalyst calcination temperature was about 450 °C,the phosphoric acid loading was 8%,the catalytic activity was the highest,the conversion rate of ethylene glycol can reach more than 99%,1,4-dioxane selectivity up to 95%or so.Under the above reaction conditions,the ethylene glycol remained at a high conversion rate after 50 hours of batch reaction,and the selectivity of 1,4-dioxane was maintained at about 70%.The optimum reaction conditions were as follows:reaction temperature was 270 °C,reaction space velocity was 0.34h-1,catalyst calcination temperature was about 450 ?,phosphoric acid loading was 4-8%,12h diethylene glycol conversion rate was close to 100%,the selectivity of 1,4-dioxane was more than 90%.After 100 h of batch reaction,ethylene glycol remained at a high conversion rate and the selectivity of 1,4-dioxane was maintained at about 80%.Finally,the regeneration performance of the catalyst was further investigated on the basis of the previous research.The results showed that the catalytic activity of the catalyst was greatly improved by the method of high temperature thermal regeneration and secondary loading of the catalyst active component.In addition,the main by-product acetaldehyde in this experiment has a high added value,taking into account the economic point,the use of supported?NH₄?₃PO₄/AC catalyst for ethylene glycol/diethylene glycol dehydration Preparation of 1,4-dioxane,with high yield,simple reaction process,good catalyst activity,high stability,showing a broad industrial application prospect.