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Preparation and development trend of sodium gluconate
Time:2018-09-08 17:07 Views:
Shenyang Xingzhenghe Chemical Co., Ltd. is a professional manufacturer of sodium gluconate, gluconolactone and gluconate. Welcome new and old customers to inquire. Tel: 13889850231Preparation and development trend of sodium gluconateSodium glucona
Shenyang Xingzhenghe Chemical Co., Ltd. is a professional manufacturer of sodium gluconate, gluconolactone and gluconate. Welcome new and old customers to inquire. Tel: 13889850231
Preparation and development trend of sodium gluconate
Sodium gluconate, also known as sodium pentahydroxy citrate, is a white or light yellow crystalline powder, soluble in water, slightly soluble in alcohol, insoluble in ether 0. Its molecular formula is C6~11O7Na, and its relative molecular mass is 218.14. Sodium gluconate is a deep processing product of glucose, and is also a basic raw material for preparing gluconolactone\gluconate (zinc\copper\ferrous salt).
It can be used as a nutritional supplement, curing agent, buffer, etc. in the food industry. It has good thermal stability and no deliquescence. It is widely used in water treatment, electroplating, metal and non-metal due to its excellent chelating properties. Various industrial sectors such as surface cleaning and cement production have a wide range of uses in the chemical, food, medicine, and light industry industries.
 
1. Status of production of sodium gluconate at home and abroad
 
At present, the annual production of sodium gluconate in the world is about 30,000 tons, the annual production in the United States is about 5,000 tons, and the annual production in Japan is about 12,000 tons. Compared with foreign countries, sodium gluconate in China is in terms of product quality, production scale and cost. There is a distance. At present, there are four manufacturers in China that use catalytic oxidation technology to produce sodium gluconate. The production capacity is about 400t/a. The products are mainly used as water stabilizers and bottle-washing agents, and are also used in the film industry. However, in general, the domestic market in China is not enough. In the past ten years, Japan’s annual export volume of sodium gluconate was 3000t. Above, the main export to the United States \ Southeast Asia \ Europe, etc., China needs further development efforts in this market. Will increase the production of food grade and industrial grade gluconate, and the proportion of sodium gluconate will also increase. It can be seen that the current production process of sodium gluconate in China is relatively low in cost compared with foreign countries. The use of new processes to produce sodium gluconate has important practical significance and significant economic benefits.

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Comparison of 2 preparation methods of sodium gluconate
 
At present, the production methods of sodium gluconate mainly include biological fermentation method, homogeneous chemical oxidation method, electrolytic oxidation method and heterogeneous catalytic oxidation method.
2.l Biological fermentation method
 
    The method includes fungal fermentation and bacterial fermentation, and there is also a fixed cell fermentation process in which a fermentation process of Aspergillus niger to produce sodium gluconate is more commonly used. The method comprises the steps of: adding a certain amount of nutrient substance to the glucose solution of 240-300 gL for sterilization, cooling to a suitable temperature to inoculate a volume fraction of Aspergillus niger seed solution of 10, and starting the stirring gas flow to adjust the p~ value of the fermentation liquid to be maintained at 6.0-6.5 The temperature is maintained during the fermentation of 32 to 34, and an antifoaming agent is added dropwise to eliminate the foam generated during the fermentation. The whole fermentation process takes about 20 hours. When the residual sugar is reduced to 1gL, it can be considered that after the fermentation is separated from the fermentation broth, the fermentation broth is crystallized by vacuum crystallization to obtain sodium gluconate crystals or spray-dried to obtain sodium gluconate powder. Product. The method has the characteristics of fast fermentation speed, easy control of fermentation process and easy product extraction. But at the same time, there are certain defects, such as the color of the product is not easy to control, and the degree of sterility is high. Since the 1950s, many people have studied the process of oxidizing glucose to sodium gluconate with air or hydrogen peroxide in the presence of enzymes and other catalysts. These include studies of immobilized cells and immobilized enzymes. Many scholars expect that the use of glucose oxidase as a catalyst for the oxidation of sodium sulphate is the future development direction. Biofermentation is still a very competitive method of competition, but the increase in oxygen consumption is a problem that is difficult to solve. If the use of hydrogen peroxide is not only expensive, but also toxic to glucose oxidase, it is economically superior to conventional fermentation methods and has a large distance.
2.2 homogeneous chemical oxidation
 
After the crystallized glucose is dissolved in water, the catalyst is added to control a certain temperature, the sodium hypochlorite solution is added dropwise, and the ionic membrane liquid alkali is added dropwise to control the pH value of the reaction system to shift the equilibrium to the direction of generating sodium gluconate, and the amount of residual sugar is determined by measuring the amount of residual sugar. The end point of the reaction is determined, and then the reaction solution is concentrated by filtration, and the solubility of sodium chloride is lower than that of sodium gluconate. After concentration, the sodium gluconate is precipitated after precipitation, and the sodium gluconate is purified to obtain a sodium gluconate content of 5 mass fraction. The above products.
The use of sodium hypochlorite oxidation to produce sodium gluconate has the advantages of high conversion rate, low process and low cost. However, in the middle step, many by-products are difficult to separate, so they are limited in application. On the basis of the improved sodium hypochlorite oxidation method in China, the Chinese researchers improved the process and increased the material concentration and reacted at room temperature. The industrial production conditions were met and the yield of the 100ta pilot plant was built around. The product sodium chloride is not easy to be separated in the product. For this reason, the oxidized reaction solution must be acidified with acid to convert the sodium gluconate formed into a lactone to be distilled off, and then extracted with an organic solvent to separate the sodium chloride from the lactone. . It is then neutralized with a base to convert the lactone to sodium gluconate. This process is cumbersome and costly.
2.3 electrolytic oxidation method
 
The method comprises adding a certain concentration of glucose solution into the electrolytic cell, and then adding a suitable electrolyte to constant current electrolysis at a certain current density at a certain temperature, and determining the industrial parameter varies depending on the electrolyte to be added, for example, when sodium bromide is used as the electrolyte. The glucose mass fraction is 23.5. The temperature is controlled at 40. The current density is 1Adm2. The electrolyte concentration is 2 mass fraction. During the electrolysis process, sodium carbonate can be added to the electrolysis at one time, and the electrolyte is concentrated and crystallized to obtain sodium gluconate crystal. Although the electrolytic oxidation method overcomes some shortcomings of the biological fermentation method and the homogeneous chemical oxidation method, the energy consumption in the industrial production is difficult to control, so it is rarely used in industrial production.


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2.4 Heterogeneous catalytic oxidation
 
A certain amount of glucose solution was prepared, added to a four-necked flask, and an appropriate amount of the catalyst was weighed and added to the flask to be kept at a constant temperature. The air is introduced and a certain concentration of NaO~ solution is continuously added to maintain a certain pH. After the reaction, the catalyst was recovered by cooling and suction filtration, and the filtrate was concentrated under reduced pressure, and crystallized and dried to obtain sodium gluconate crystals. The process is simple to react. Smooth and easy to control mild reaction conditions. It is a more advanced process. The catalyst commonly used in the production of sodium gluconate by heterogeneous catalytic oxidation is mainly palladium-based catalyst supported on activated carbon. Palladium-carbon catalyst is an excellent catalyst in palladium catalyst. It has good selectivity, strong anti-poisoning ability and easy recovery. It is the preferred catalyst for the selection of oxygen in fine organic chemicals. Although this catalyst shows good catalytic performance when catalyzing the oxidation of glucose, it also has the disadvantages of long oxidation time and many side reactions. Moreover, the catalyst has a reduced catalytic efficiency after being used for a certain number of cycles, and even has substantially no catalytic activity, so that the reaction time for decreasing the glucose conversion rate is prolonged. At this time, the catalyst must be scrapped and renewed, which correspondingly increases the consumption of the catalyst per unit product, and also makes the production cost of the sodium gluconate product higher. It can be seen that the performance of the catalyst is the key to this method. Catalytic oxidation is still the main method for the production of sodium gluconate in China. Its production accounts for more than 80. The preparation methods compare four methods for the preparation of sodium gluconate by glucose oxidation, which are widely studied in China. In industrial production, bio-fermentation and multi-phase catalytic oxidation are widely used. The multi-phase catalytic oxidation process has a process, a simple reaction, a mild condition and a variety of gas-liquid-solid three-phase mixed reactors at atmospheric pressure. The reaction temperature can be generally controlled below 60. The reaction time is short, the conversion rate is high, the three wastes are small and easy to handle. The key to this method is the performance of the catalyst and the number of cycles of use. As long as the appropriate catalyst system is selected, the catalyst is used multiple times to overcome the expensive price of the precious metal and the catalyst loss. The shortcomings of living, heterogeneous catalytic oxidation will have greater advantages and application potential.
3 development trend
 
The process of producing sodium gluconate by heterogeneous catalytic oxidation is simple, the oxidation time is short, the process time is greatly shortened, and the energy consumption is reduced, which is a research and development and promising technology. The superiority is unquestionable, but there are many problems in this method. First, there are problems in the preparation of the catalyst, such as washing difficulties and filtration difficulties. In the oxidation process, the catalyst is also less tolerant to impurities, and the activity and selectivity are decreased after a certain number of uses. These problems have been solved by research, and the recovery of palladium from the failed palladium-carbon catalyst has become a major economic and social benefit that has received more and more attention and attention.
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