Thermodynamic And Kinetic Studies On The Alkoxylation Of Camphene

In recent years, a variety of valuable monoterpenic ethers which can be used as flavors and fragrances in perfume and cosmetic products, or as additives in medicine and agricultural chemicals were developed from the alkoxylation of monoterpenes. Among them,2-methyl-3-isobornyl oxy-1-propanol (also known as isobornyl hydroxyl isobutyl ether) has valuably applicable in flavors and fragrances, cosmetics and other areas owing to long-lasting, woody, dry amber and cedar scents. So far, there have been no open literatures that are published to deal with isobornyl hydroxyl isobutyl ether.In this study, the alkoxylation of camphene with 2-methyl-1,3-propanediol was carried out in the presence of anhydrous macroporous and strong acid cation exchange resins. The effects of various parameters, such as agitation speed, catalyst type, solvent, initial mass ratio of reactants, reaction temperature and reusability of catalysts, were investigated in a 250 mL glass stirred tank reactor to optimize the reaction conditions. Thermodynamic parameters and kinetic parameters were derived by correlating experimental data, which provided experimental evidence and theoretical foundation for industrialization.Achievements obtained in this study are as follows:1. The conditions for the alkoxylation of camphene with 2-methyl-1, 3-propanediol under the catalytic action of anhydrous Lewatit 2620 were optimized as follows:agitation speed was 400 rpm; initial mass ratio of 2-methyl-1,3-propanediol to camphene was 1.5:1; catalyst loading based on the total mass of reactants was 20%; reaction temperature was 353 K and reaction time was 4 h. Under these optimum conditions, the conversion of camphene was 78.80% and the selectivity of isobornyl hydroxyl isobutyl ether was 93.5%. Besides, the catalysts showed good catalytic activity after reusing for eight times. Besides, the optimized reaction conditions were also verified in a 5 L double layer glass reaction kettle. From the perspective of conversion of camphene and selectivity of isobornyl hydroxyl isobutyl ether, result in the scale-up experiment is almost the same as the small-scale experiment, which providing evidence for industrial application by using industrial-grade camphene as the raw material.2. By lengthening the reaction time, thermodynamic equilibrium constants at 333-370 K were derived. To correct the nonideality of reactants, activities were introduced to the calculation. The UNIFAC group contribution method was used to calculate activity coefficients of reactants. The temperature dependence of reaction equilibrium constant was described as follows:3. The enthalpy changes calculated by three different methods (Gaussian 03, constant, a function of temperature) were compared. The value (-74.6±3.3 kJ/mol) calculated by the last method was closer to the theoretical value (-75.73 kJ/mol) than that given by the second method (-30.2±1.2 kJ/mol), which indicating the temperature dependence of enthalpy change was not negligible.4. A Langmuir-Hinshelwood-Hougen-Watson (LHHW) model based on activity was introduced to fit experimental data for the purpose of deriving kinetic parameters.Under optimal experiment conditions, the LHHW model can be written as:Results calculated from LHHW model are in satisfactory agreement with the experimental ones, which indicates that the LHHW model can be used to describe the kinetics for the alkoxylation of camphene with 2-methyl-1,3-propanediol in the presence of anhydrous Lewatit 2620.