Experimental Study On The Preparation Method Of Multi-functional Expandable Graphite

Graphite is crystal compound with layer structure. Expandable graphite is prepared when non-carbonaceous reactant inserted into the layers of graphite by chemical or electrochemical reaction. Expandable graphite is a kind of important inorganic non-metallic material, and it has a lot of good properties such as high catalytic activity. Expanded graphite is a good flame retardant and adsorption reagent. Because of these properties expandable graphite is widely applied in many fields. Under high temperature expanded graphite with porous structure is prepared when expandable graphite is inflated, and the expanded graphite with high specific surface area is a high-quality adsorption material. The expandable graphite has different expanded volume or initial expansion temperature when different intercalation process or reagent is used. In order to prepare the expandable graphite with excellent properties of adsorption, catalytic activity and anti-flame, the oxidant, intercalated agent, auxiliary intercalated agent and reaction temperature are optimized, and these properties are all characterized.Expanded graphite (EG) loaded titanium oxide is prepared with 50 mesh natural graphite as raw material, potassium permanganate as oxidant, sulfuric acid and titanium tetrachloride as intercalation reagent. First, the mass ratio of C to KMnO₄, C to H₂SO₄ (75%), C to titanium tetrachloride and reaction temperature is gained through Orthogonal experiment. Different kinds of graphite are evaluated with various characterization methods such as XRD,EDS,TG-MS, Simultaneously the structure parameters of EG is determined. Second, with EG loaded titanium oxide as adsorbent, its discoloring capability for wastewater that is simulated by methyl orange is investigated. As a result, methyl orange can be decolored very well with EG loaded titanium oxide as adsorbent.In the Experiment,the preparation method of expandable graphite with sulfuric acid and ferric chloride hexahydrate as intercalated agent is established. The influential factors on catalytic activity and expanded volume of expandable graphite such as temperature, the amount of KMnO₄, H₂SO₄ (75%) and FeCl₃ are investigated through the orthogonal test. XRD was adopted to characterize different kinds of graphite. Take esterification rate as the priority object, the feasible material proportion in the preparation of expandable graphite is: C: KMnO₄ : H₂SO₄(75%): FeCl₃ =1: 0.34: 3.9(75%): 0.15. The intercalation reaction is carried out at room temperature for 60 minutes, and the yield of isoamyl acetate reaches 86.0% with the expandable graphite used as solid acid catalyst. The research indicates that expandable graphite show higher catalytic activity for the esterification of acetic and isoamyl alcohol, and it is recycling, moderate and reusable.Suitable oxidant, intercalation reagent, ancillary intercalation reagent and reaction temperature are confirmed to prepare expandable graphite with excellent anti-flame property. First, method to determine the initial expansion temperature of the expandable graphite is established, and the feasible condition is confirmed to prepare the expandable graphite with different initial expansion temperature through orthogonal experiment. According to the optimized condition, expandable graphite with high or low initial expansion temperature is prepared, and various performance tests and characterization are carried on. Next, the anti-flame properties of these two kinds of expandable graphite are determined. The addition of 30% expandable graphite with high initial temperature can make EVA's oxygen index increase to 28.1% from 20%, and the addition of 20% expandable graphite with low initial temperature can make LDPE's oxygen index increase to 27.8% from 21%. Oxygen index test indicated that these two kinds of expandable graphite both have excellent anti-flame capability.