2.2.2 Kinetic study
The kinetic studies were conducted on a plug-flow fixed-bed reactor. The experimental set-up is depicted in Figure S1. The tubular reactor with the inner diameter of 4 mm and length of 10 cm was made of 316L stainless steel. Amberlyst 15 was dried at 378 K for 24 h until the content of water in the catalyst was below 1% as determined by the Karl Fischer method. Then, 1.0 g of the catalyst (d p< 0.5 mm) diluted with quartz sand (0.1 mm <d p < 0.8 mm) to avoid temperature runaway was loaded in the reaction zone. The remaining space was filled with quartz sand. Prior to the reaction, the catalyst bed was further purged with N2 at 373 K to remove water. After being cooled down to below the reaction temperature, cyclohexene and acetic acid with a prescribed molar ratio was continuously pumped into the reactor at a flow rate 60 g h–1. Each study was last for 2–3 h, during which the effluent was sampled several times to ensure that the reaction has reached the steady state. The reaction rate is calculated as follows:
in which C6 represents cyclohexene, while C6E represents the resulting ester. x represents the molar fraction, which is dimensionless.F is the total molar flow rate in mol h–1. AndW represents the catalyst mass with unit in kg. Both the thermodynamic and kinetic studies were repeated at least twice.