Background technology
L-ascorbic acid (vitamin C, hereinafter referred to as Vc) is an essential vitamin for humans and animals and naturally exists in fresh vegetables and fruits. Vc has been widely used in fields such as medicine, food, cosmetics and animal breeding. However, the hydrogen of the enol hydroxyl group in Vc is easy to dissociate and is easily oxidized and destroyed by air and other oxidants. It will quickly undergo an irreversible decomposition reaction and lose the reducing ability of Vc. If any of the hydroxyl inorganic acids is esterified, the stability to heat, acid, and oxygen will be greatly enhanced.
L-ascorbic acid-2-phosphate salt is a derivative of L-ascorbic acid. It appears as a white or slightly yellow powder, odorless and tasteless; it is relatively resistant to light, heat and air. Stablize. L-ascorbic acid-2-phosphate salt has good environmental stability. Since the level of phosphatase is generally high in living organisms, the biological potency of L-ascorbic acid-2-phosphate salt is ideal.
So far, there are three main methods of ascorbic acid phosphorylation that are more important: ① Use phosphorus oxychloride for phosphorylation Reagent (for example, potassium hydroxide is mentioned in European Patent Publications 388,869 and 582,924 and U.S. Patent 4,179,445). This reaction requires the reaction of L-ascorbic acid with phosphorus oxychloride in the presence of pyridine to obtain L- Ascorbic acid-2-monophosphate salt while maintaining the pH at 12 to 13 with aqueous potassium hydroxide solution and cooling to 0°C. After the reaction is completed, the pyridine is evaporated, and the remaining mixture is spray-dried and converted into L-ascorbic acid-2-monophosphate salt feed products that can be directly sold. ② Use sodium trimetaphosphate as a phosphorylation reagent and L-ascorbic acid to perform phosphorylation under alkaline conditions (such as the method of U.S. Patent 4647672 and 5110950 and the document “Food and Feed Industry”, 2009, No. 12, 28~30 ), the obtained product is mainly L-ascorbic acid-2-polyphosphate instead of L-ascorbic acid-2-monophosphate; ③ Use L-ascorbic acid-2-polyphosphate and L-ascorbic acid under alkaline conditions The reaction prepares L-ascorbic acid-2-monophosphate salt (such as US Patent 6060937, and European Patent 97104554).
Based on the above literature, there are several problems:
1) Phosphorus oxychloride used in method ① has strong activity and poor selectivity. L-ascorbic acid is a polyhydroxy compound and pyridine must be used. Protect the 5 and 6 hydroxyl groups of L-ascorbic acid, otherwise there will be many side reactions, the product will have low potency, and the phosphorus oxychloride and chemical reagent pyridine used are toxic substances. In addition, the process conditions of this method are complicated and the cost is high. For these reasons, the method of phosphorylation with phosphorus oxychloride is an economically and ecologically unattractive method.
2) In method ②, external conditions are required to maintain the temperature of the reaction system, and the catalyst calcium chloride also needs to be added. For example, the method described in Food and Feed Industry, 2009, N0.12 uses L-ascorbic acid as raw material, sodium trimetaphosphate as phosphorylation reagent, and anhydrous calcium chloride as catalyst to prepare L-ascorbic acid polyphosphate. In this method, the reaction temperature is 28°C, the catalyst is calcium chloride, and the obtained product is mainly L-ascorbic acid polyphosphate. Since animals need to use the phosphatase in the body to decompose the phosphate groups on the molecular structure of L-ascorbic acid polyphosphate to directly produce free L-ascorbic acid before it can be absorbed and utilized, therefore the utilization rate of animals with food that stays in the body for a short time will be lower. reduce. In addition, using external conditions to maintain the reaction system will inevitably bring about power and energy costs and increase production costs. At the same time, using anhydrous calcium chloride as a catalyst increases raw material transportation and storage costs.
3) Method ③ is only to reduce the amount of phosphate contained in L-ascorbic acid-2-polyphosphate salt and increase the percentage content of L-ascorbic acid-2-monophosphate. The purpose is to convert all L-ascorbic acid-2-polyphosphate into monophosphate salts. The reaction time is long and nitrogen protection must be used. The equipment requirements are high, the reaction conditions are harsh, and the chemical reaction process is too complicated. In the final reaction mixture, Before spray drying, water must first be added for dilution to reduce the viscosity, which increases the energy required to dry this part of the water. Therefore, commercial operations will undoubtedly greatly increase the cost and cause unnecessary waste.
4) The method of preparing L-ascorbic acid-2-phosphate salt involved in the existing technology has poor coagulation properties of the reacted liquid and is not suitable for flash evaporation. Instead, spray drying is mostly used, which requires large equipment investment. , higher energy consumption and increased product manufacturing costs.
Therefore, exploring new processes for preparing L-ascorbic acid-2-phosphate ester salts, reducing manufacturing costs, simplifying operating steps, and improving animal bioavailability have always been problems that those skilled in the art are trying to solve. .
Content of the invention
The present invention provides a method for preparing L-ascorbic acid-2-phosphate ester salt, especially from L-ascorbic acid, L-sodium ascorbate, and sodium trimetaphosphate. A method for preparing L-ascorbic acid-2-phosphate salt by reacting with calcium hydroxide or calcium carbonate to overcome the shortcomings of the existing technology.
In order to achieve the purpose of the present invention, the preparation method of this L-ascorbic acid-2-phosphate ester salt includes the following steps:
a. Mix water, L-ascorbic acid, and L-ascorbic acid Sodium is added to the reaction kettle in a weight ratio of 0.5~2:1:0.2~1.0 and stirred for 0.5~1 hour;
b. Slowly add 20%~60% of sodium to the above solution Calcium hydroxide suspension or calcium carbonate suspension, adjust the pH value of the solution to 5~12;
c. Add sodium trimetaphosphate 0.6~1.8 times that of L-ascorbic acid under stirring in the solution of step b.� Carry out phosphorylation reaction, and use 20% to 60% calcium hydroxide suspension or calcium carbonate suspension to adjust the pH value of the reaction solution to 8 to 10 during the reaction;
d. The above-mentioned phosphoric acid After the reaction for 20 minutes to 1 hour, the reactant is left to solidify at room temperature for 2 to 10 hours, chopped, and then flash-dried to obtain an off-white or light yellow L-ascorbic acid-2-phosphate ester salt product.
Comparing the present invention with the existing method of preparing L-ascorbic acid-2-phosphate ester salt, it has the following beneficial effects: ① Since the intermediate reactant L-sodium ascorbate is added to the reactant during phosphorylation , which reduces the viscosity of the reaction system, not only increases the concentration of the reaction solution, but also reduces the viscosity of the reaction system, speeds up the mass transfer process, thereby speeding up the phosphorylation reaction speed, so that the reaction can be carried out by its own heat without the need for a catalyst and heating to greatly shorten the phosphorylation time. Compared with the existing process, the reaction speed can be increased by 3 to 6 times, and the reaction time can be shortened by about 80%. ② Since the reaction of the reaction raw materials does not require external heating and maintenance of the reaction temperature, the reaction can be carried out well by relying on its own exothermic conditions, thereby reducing power and energy consumption, greatly reducing production costs, and is incompatible with existing processes. By comparison, it can be converted into a consumption reduction of more than 10%. ③ Due to the high concentration of reactants and good reaction effects, the reaction liquid is left to stand and solidify for a significantly shorter period of time. After 2 to 10 hours, the materials can be fed for flash evaporation, which greatly reduces the waiting time for the flash evaporator and requires no modifications to the equipment or personnel. Without any increase, the production capacity can be increased by 30% and the cost can be reduced by more than 10%. ④ By not adding a catalyst, compared with the known method of adding a catalyst in DuPont in the United States in the prior art, the content of L-ascorbic acid-2-monophosphate salt in the product of the present invention is significantly increased, and can be detected by HPLC (calculated as ascorbic acid). Reaching more than 35%, the total amount of phosphorylated L-ascorbic acid is more than 37%, which meets the standard requirement that the total amount of phosphorylated L-ascorbic acid in feed additives is greater than 35%, which can greatly improve the bioavailability of animals.
Specific implementation methods
As shown in Figure 1, weigh 50Kg L-ascorbic acid and 19.8KgL respectively. – Sodium ascorbate, add it to the reaction kettle respectively and inject 30L purified water to dissolve for 30 minutes. Use 30% (W/W) calcium carbonate suspension to adjust the pH of the solution to 5, then add 50Kg sodium trimetaphosphate and perform a phosphorylation reaction. During the reaction, 20% (W/W) calcium hydroxide suspension was used to maintain the pH value of the solution at 8.5. After the phosphorylation reaction for 30 minutes, the resulting product was left to solidify at room temperature for 6 hours, chopped, and then flash-dried to obtain 149 grams of off-white or light yellow L-ascorbic acid-2-phosphate salt. The total amount of effectively phosphorylated L-ascorbic acid detected by UV detection was 37.46%, and the content of L-ascorbic acid-2-monophosphate salt detected by HPLC was 35.14%.
