Isomerization and hydration of fumaric acid under catalytic and noncatalytic conditions

摘要

Noncatalytic isomerization (R1) and hydration (R2) of fumaric acid (F) was carried out homogeneously and isothermally in an electric-heated batch reactor (reactor 1), in a microwave-heated tank reactor (reactor 2), and in an oven-heated tubular reactor (reactor 3) at temperatures between 448 and 623?K. The concentrations of F, malic acid (M), and maleic acid (Mx) were determined chromatographically at reaction times from zero up to 25,200?s. The variation in the rate constants for the forward reactions?R1 and R2 with temperature was estimated with an Arrhenius type equation by involving parameters tuned on the results obtained in the first reactor ( k ~(10,α)?=?1.08×10_(?1)?s_(?1), E ~(a1,α)/ R? =?5070?K, k ~(20,α)?=?1.62×10_(1)?M_(?1)s_(?1), E ~(a2,α)/ R? =?8331?K). The set of data from the experiments performed in the reactors 2 and 3 under a variety of operating conditions was used to validate the tuned kinetic parameters. To investigate the contribution of the noncatalytic consumption of F to the overall conversion with hydrochloric acid as catalyst, an available kinetic model that takes the concentration of HCl into account was modified. The old model, which was only able to estimate correctly the kinetics of acid-catalyzed conversion of F with HCl at concentrations higher than 0.65?M, can now describe the kinetics of the same reaction system properly without HCl, or at any amount of this catalyst.