Study On Phase Equilibria And Technological Process Optimization Of 1,3-Butadiene Production From Ethanol

1,3-Butadiene(BD),mainly extracted from petroleum fuels,is a most essential raw material at the core of the chemical industry.It is mainly used for synthetic styrene butadiene rubber(SBR),acrylonitrile butadiene styrene(ABS)and so on a very wide range of uses.Currently,there are two techniques widely used for the production of 1,3-butadiene.One is dehydrogenation of butene or butane.The other is extraction from the unsaturated hydrocarbon mixtures of ethylene cracking.However,since the limitation of non-renewable resources,using bio-ethanol as an alternative material for producing 1,3-butadiene has received worldwide attention.In this design and simulation process of 1,3-butadiene from ethanol,phase equilibrium data is basic and significant information for calculation.So,isobaric vapor-liquid equilibrium(VLE)data for three binary systems of acetaldehyde + ethanol,acetaldehyde + ethyl acetate,acetaldehyde + 1-butanol were determined with a modified Rose-Williams equilibrium still at 101.3 kPa.The experimental data were confirmed by the area method of Herington and point-to-point method of Van Ness.Activity coefficients models,Wilson,NRTL and UNIQUAC were carried out to correlate the experimental VLE values.Wilson and NRTL models showed a good agreement and the binary interaction parameters were estimated.The butadiene production technology was researched to simplify the process and improve the recovery of raw materials.This process included dehydrogenation reactor and butadiene reactor.Cooling system was followed by the products of butadiene reactor.And then the vapor phase fed into butadiene extraction and purification system.In absorption-desorption process,two separation schemes were designed,which were desorption column with liquid side stream process and desorption column without liquid side stream.Results showed that,in desorption column with liquid side stream process,butadiene concentration in off-gas from absorption column dropped from 0.5 wt% to below 100 ppm and the amount of fresh absorbent reduced by 26%,respectively.Then the crude butadiene was purified to qualified products.Special distillation methods were used to recovery acetaldehyde and ethanol in the liquid phase,the recovery of acetaldehyde was 99.98% and the recovery rate of ethanol reached 99.95%.Exergy analysis was carried out to improve energy efficiency.The total exergy loss of this process was calculated.It was found that acetaldehyde and ethanol recovery system was the most important part of exergy loss distribution in the whole process.Thus,a heat integrated distillation scheme was simulatively proposed,the overhead vapor of ethanol column integrated with aldehyde and alcohol separation column,diethyl ether column and acetaldehyde column.To make a further optimization,sensitivity analysis was done to seek appropriate parameters.This scheme presented 26.82% less exergy loss than the previous scheme.This paper can provide useful guidance for industrial production of butadiene process from ethanol.