Special care must be given in the purification of these large organic molecules due to their thermally sensitive nature. Exposure to sustained high temperatures can lead to decomposition and cracking of these components – which can alter their smell and color.
In order to keep temperatures low during their processing, many distillation columns are operated under vacuum conditions ranging from 0.7 – 400 mmHg. There are several challenges associated with the rectification of these components to high purities under these conditions:
- Low system pressure drop per theoretical stage
- Provide high number of theoretical stages and at short column heights
- Short residence times for heat sensitive products
- Proper distribution of low liquid load usual in vacuum operation
- Distillation columns are generally used for different lots/products and the liquid distributors must be robust enough to cover large liquid load ranges
Gauze packing is preferred in the flavor and fragrances industry since decades. Continuous and batch rectifications are used for the purification of many heat sensitive products that require high separation efficiency such as menthol, geraniol, citral, citronellol, eugenol, limonene, pinene, tocopherol and many others.