The carbonation of epoxidized vegetable oils is a crucial step in the preparation of nonisocyanate polyurethane. Several research groups have screened homogeneous catalysts such as tetra-n-butylammonium bromide for this reaction, but the research devoted to the use of heterogeneous catalysts and on the application of kinetic modeling is rare. Hence, to develop this process on an industrial scale, an appropriate heterogeneous catalyst should be found and a kinetic model developed. A catalyst consisting of an ionic liquid supported on carboxymethyl cellulose has been proved to be a suitable heterogeneous catalyst for this carbonation reaction. A catalyst based on 1-hydroxypropyl-3-n-butylimidazolium chloride and niobium(V) chloride supported on protonated carboxymethyl cellulose (HBimCl-NbCl5/HCMC) was synthesized and tested for the carbonation of epoxidized fatty acid methyl ester. Effects of the catalyst particle size, agitation speed, catalyst loading, and reaction temperature on the reaction kinetics were investigated. The carbonation reaction proceeded efficiently at a temperature of 443.15 K, agitation speed of 500 rpm, and using native catalyst particles with a median diameter of 652 μm. A kinetic model was developed to simulate the conversion of the epoxide group with time.