Thermodynamic And Kinetic Studies On The Reactions Catalyzed By Cation Exchange Resins

As a new type of environmental-friendly solid acid catalysts,cation exchange resins perform well in industrial reaction processes for high activity and stability,low cost and convenient recovery,which can avoid the problems of equipment corrosion,more by-products,environmental pollution and difficulty in continuous operation Recently,it has gradually become a hot area of green chemical industry that cation exchange resins were widely used in organic reactions such as esterification,alkoxylation,dehydration and hydration replacing mineral acids.Based on the optimized conditions,design and scale-up of the manufacturing processes can be guided by the thermodynamic and kinetic parameters of reaction systemsTwo types of esterification and one new type of alkoxylation system catalyzed by cation exchange resins were investigated in this paper.Effects of factors such as resin type,initial molar ratio of reagents and temperature were systematically studied under the premise of eliminating external diffusion,and the optimal conditions were obtained in lab.Thermodynamic parameters were modified by the UNIFAC group contribution method and a kinetic model describing the reaction well was proposedThe relevant progress made in this research is as follows1.Study on the synthesis of methyl laurate catalyzed by cation exchange resinThe optimized conditions on the esterification of lauric acid with methanol catalyzed by cation exchange resin in a 250mL glass stirred reactor are as follows:agitation speeds:400rpm;A39 as catalyst;catalyst loading:15wt%;initial molar ratio of acid and methanol was 1:3;temperature:333.15K.With non-ideal liquid mixing taken into account,Ke ranging from 318.15K to 333.15K which have been modified by the UNIFAC group contribution method can be expressed as follows:Ke=exp(727.9/T+1.408)E-R model is more accurate description on the reaction process than P-H model eliminating the influence of internal and external diffusion.The kinetic equation based on E-R mechanism is as follows:r=Mcat(kfaLAaMeOH-kraMLaH2O)/1+KMaMeOH+KMLaML Where kf=2.20×1011×exp(-10534/T)kr=5.37×1010×exp(-11262/T)KM=2.31×10-5×exp(2094.4/T)KML=4.55×10-4×exp(2279.0/T)2.Study on the synthesis of isoamyl acetate catalyzed by cation exchange resinEsterification of acetic acid with isoamyl alcohol catalyzed by cation exchange resin was studied in an IFBR system.The optimized conditions are as follows:volume flow rate:40mL/min;NKC-9 as catalyst;catalyst loading:20wt%;initial molar ratio of HAc and IAA was 1.2:1;temperature:323.15K.After correcting the non-ideality of liquid mixing by the UNIFAC group contribution method,the relationship between Ke and temperature ranging from 318.15K to 333.15K can be expressed as follows:Ke=exp(804.6/T+0.9603)On the premise that internal and external diffusion can be eliminated,LHHW model describes reaction process more accurately than PH model.The kinetic equation based on LHHW mechanism is as follows:r=Mcat(kfaHAcaIAA-kraIAAcaH2O)/(1+KHAcaHAc+KIAAaIAA+KIAAcaIAAc+KH2OaH2O)2 Where kf=6.23×109×exp(-7152.1/T)kr=2.38×109×exp(-7956.7/T)KHAc=1.05×10-3×exp(2660.4/T)KIAA=2.11×10-5×exp(3723.4/T)KIAAc=7.52×10-3×exp(2115.8/T)KH2O=2.40×10-4×exp(3072.6/T)3.Study on the alkoxylation of dihydromyrcene catalyzed by cation exchange resinDihydromyrcene is alkoxylated with 2-methyl-1,3-propanediol catalyzed by cation exchange resin in a 250mL glass stirred tank reactor.The optimized conditions are:agitation speeds of 400rpm,Lewatit2620 as catalyst,catalyst loading of 20wt%,initial molar ratio of 1:1 and temperature of 353.15K.Considering the non-ideality of liquid mixing,Ke between 343.15K and 363.15K modified by the UNIFAC group contribution method is:Ke?exp(5949.2/T-18.96)PH model is used to fit the kinetics ignoring the effect of inner and outer diffusion,and the equation can be expressed as:r=Mcat(kfaDHMaMPO-kraDHMPO)Where kf=2.99×108×exp(-10353/T)kr=5.14×1016×exp(-16302/T)...