Research On The Ethylene Glycol And 1,2-Butanediol Chemical Looping Separation New Process

Ethylene glycol(EG)is an important raw material for the synthesis of polyester fiber with great market potential.1,2-butanediol(1,2-BDO),which forms nearly equimolar azeotrope with EG,is by-produced in non-petroleum-based EG routes,resulting in low yield,high separation energy consumption and unguaranteed of product quality.In view of the above problems,this paper proposes an EG and 1,2-BDO chemical looping separation new process,in which EG and 1,2-BDO are converted into 2-ethyl-1,3-dioxolane(2ED)and 4-diethyl-1,3-dioxolane(24DED),2ED and 24DED are separated and hydrolyzed to reobtain EG and 1,2-BDO.Main research contents and results are as follows:(1)A reactant screening procedure consisting of prescreening,experiment validation and separation evaluation was proposed and propyl aldehyde was selected.Thermodynamics of acetals are studied experimentally,which fills the gap in basic data.(2)For the reaction and separation coupled process of mixed diols and propyl aldehyde,the kinetic data were measured with KRD001 as catalyst and the corresponding kinetic parameters were fitted.The law of phase transition of the reaction system was studied by NRTL model calculation.Results showed that there was a critical phase transition conversion in the reaction process and when aldehyde/diols mole ratio was within 0.5～1.9,the equilibrium system was two liquid phases.Based on the above study,a reaction phase-separation rectification coupled process was established,which realized the separation of 2ED and 24DED with high efficiency and low energy consumption.Further study showed that the energy consumption per kmol of 2ED output is the smallest when the aldehyde/EG mole ratio in the CSTR reactor is at 1.2.(3)For 2ED hydrolysis to obtain EG,reaction kinetics data are experimentally obtained and parameters are determined by regression.Pilot reactive distillation experiments of 2ED hydrolysis are carried out and the relative errors between the experimental results and the model calculation value are within 5%,which verify the accuracy of the reactive distillation model.Aldehyde-EG and EG-aldehyde processes are proposed,and the operation cost and capital cost of the aldehyde-EG process has been reduced by 54.1%and 32.2%by comparison.(4)The EG and 1,2-BDO chemical looping separation new process is evaluated from aspects of technology,economy,and environment.It theoretically achieves 100%EG recovery.The economic benefit is high with the internal profit reaching 237%,and it is environmentally friendly as the input potential environmental impacts(PEIs)per kg of EG is 4.73,and the output PEIs per kg of EG is 2.81,which shows great potential in practical application.