1. The ketene method This method is a more commonly used method in international industrial production. Acetic acid is cracked at high temperature to generate ketene, and then condensed with crotonaldehyde to form polyester, and then hydrolyzed and refined to obtain the finished product. Raw material consumption quota: ketene 510kg/t, crotonaldehyde 1100kg/t.

2. The malonic acid method is obtained by condensation and decarboxylation of malonic acid and crotonaldehyde.

3. The acetone method is obtained by the condensation of acetone and crotonaldehyde, followed by dehydrogenation.

4. The butadiene method uses butadiene and acetic acid as raw materials, in the presence of a manganese acetate catalyst, and compressed at 140°C to prepare γ-ethylene-γ-butyrolactone. Butyrolactone is ring-opened to obtain sorbic acid under the action of acidic ion exchange resin.

5. Acetic acid is cracked at high temperature to generate ketene, and then condensed with crotonaldehyde to form polyester, and then hydrolyzed and refined to obtain the finished product.

6. Tobacco: OR, 44; OR, 26. At 0ºC, crotonaldehyde and ketene are reacted under the catalysis of boron trifluoride; or 2-crotonaldehyde and malonic acid are prepared by heating in the presence of pyridine.