Synthesis And Deacidification Of Polymethoxy Dimethyl Ether

Polyoxymethylene dimethyl ether(PODEn)has a high cetane number and oxygen content.It is a good diesel additive as it is very similar to diesel oil,and can be directly miscible.Used as a diesel addition,it can thereby improve the combustion efficiency of diesel engines thus reduce pollutant emissions.The key in synthesizing polymethoxy dimethyl ethers lies in the choice of low-cost raw materials and catalysts and the removal of large amounts of organic acids from the products.This thesis examined a method that utilizes the current excess capacity of the chemical product dimethyl ether(DME)as raw material to produce PODEn.Heterogeneous catalyst molecular sieves are used for synthesizing polyoxymethylene dimethyl ethers,and the development of cheap,efficient,and easily regenerated adsorbents for the removal of organic acids in products are achieved.1.The reaction to prepare polyoxymethylene dimethyl ether using dimethyl ether and oxygen as raw materials is divided into two stages.The first stage uses a tin-loaded MgO-Al2O3 carrier as a catalyst under appropriate preparation conditions(load of tin is 23%)and the optimal reaction process(reaction temperature 270 ?,reaction pressure 0.3MPa,DME/O2 is50:20)within the range of conditions,can generate methylal(DMM),methyl formate(MF),formaldehyde(FA)and other products;the second stage of the reaction is to add a certain percentage of DMM to the liquid product obtained in the first stage,and use the molecular sieve H? as a catalyst to react in the reaction vessel(reaction temperature80?,Reaction pressure 0.2 MPa),PODE3?8 two-stage product can be obtained.2.Use an MgO-Al2O3-La2O3 composite carrier(labeled as JK-6-2,JK-6-3,JK-9-2,and JK-9-3,respectively)with different material ratios as the adsorbent to remove the organic acids from two-stage product(PODE3?8).The optimal reaction process were determined under certain conditions(reaction temperature 30?,atmospheric pressure,liquid space velocity is7(/h),adsorbent particle size=0.425-0.6mm),and the adsorbent JK-9-2 was selected.At the same time,the adsorbent JK-9-2 is the best adsorbent with excellent adsorption and regenerability.Subsequent experiments have shown that zinc loading on the carrier can achieve better adsorption-regeneration effects.Through a series of zinc loading(2%to 10%)experiments,it is concluded that the JK-9-2 adsorbent loaded with 4%zinc has the most excellent adsorption-regeneration deacidification performance,in the case of particle size of 30-40 mesh(0.425-0.6mm),the amount of adsorbed acid can reach 28.85mg/ml.After several adsorption-regeneration cycles,the amount of adsorbed acid is not greatly reduced,stable around 12mg/ml.The adsorbent has good strength and does not affect the performance of the adsorbent due to insufficient strength.