Method for synthesizing alkyl glycoside surfactant by one-step process

Abstract

The invention relates to a method for synthesizing an alkyl glycoside surfactant by a one-step process, which solves the problem that the residual quantity of glucose in a product material obtained by the existing one-step process for synthesizing the alkyl glycoside surfactant is high, and adopts the technical scheme that the method for synthesizing the alkyl glycoside surfactant by the one-step process comprises the following steps of: in the presence of an acid catalyst and an additive, adding a catalyst, alkyl alcohol and carbohydrate are subjected to an aldolization reaction to obtain a product material containing alkyl glycoside, the additive molecule comprises at least one selected from the group consisting of triose alcohol, butyl sugar alcohol, pentitol and hexitol, and the carbohydrate comprises glucose. The addition of the additive reduces the residual amount of glucose in the product material.

Description

Technical Field

[0001] This invention relates to a one-step process for synthesizing alkyl glycoside surfactants. Background Technology

[0002] Industrially, there are two main processes for synthesizing alkyl glycosides: one-step and two-step processes. The one-step process primarily uses fatty alcohols (usually C12-C14 fatty alcohols) and carbohydrates (commonly glucose or starch) as raw materials to prepare alkyl glucosides in one step. The two-step process mainly involves reacting a lower alcohol (such as n-butanol) with glucose to generate a lower alcohol glycoside (such as butyl glycoside), followed by an acetal exchange reaction between the fatty alcohol and the lower alcohol glycoside. The main reaction equation for the one-step process is as follows:

[0003]

[0004] n represents the degree of polymerization of glucose (typically around 1.1-3); R represents alkyl groups.

[0005] In industrial production, the one-step synthesis process typically involves adding a fatty alcohol to a reactor, starting stirring, adding glucose (the molar ratio of fatty alcohol to glucose is 2–6), adding an acidic catalyst (commonly p-toluenesulfonic acid, but other organic or inorganic acids can also be used), with the catalyst amount being 1.1–1.5% of the glucose (by mass). The reaction is carried out at an absolute pressure of 3–10 kPa and a temperature of 105–115°C. After the reaction is complete, the temperature is lowered to 70–80°C, and an alkali metal oxide or hydroxide (such as MgO or NaOH) is added. The pH is adjusted to 8–10, and the material is then transferred to a two-stage evaporator (falling film evaporator and scraped evaporator). Free fatty alcohols are removed at a temperature of 130–180°C and a pressure below 3.3 kPa (the removed fatty alcohols can be recycled). The material is then transferred to a stirred tank where process water is added to prepare an alkaline aqueous solution of alkyl glycosides with a concentration of about 50%. The pH is then adjusted to 10–12, and the material temperature is maintained at about 50–80°C. However, the reaction time in the existing technology is relatively long; otherwise, a shorter reaction time would result in a high content of unreacted glucose in the product. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the residual glucose content in the product obtained by the existing one-step process for synthesizing alkyl glycoside surfactants is high. The present invention provides a new one-step process for synthesizing alkyl glycoside surfactants, in which the product obtained by the synthesis reaction has a low content of unreacted glucose, thereby allowing for a suitable reduction in synthesis time.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] A one-step process for synthesizing alkyl glycoside surfactants includes: reacting an alkyl alcohol with a carbohydrate in the presence of an acidic catalyst and an additive to obtain a product containing an alkyl glycoside, wherein the additive includes at least one selected from the group consisting of triitol, butylol, pentitol, and hexitol, and the carbohydrate includes glucose.

[0009] The use of the above-mentioned additives significantly reduced the content of unreacted glucose in the product material.

[0010] In the above technical solution, the triitol is preferably glycerol.

[0011] In the above technical solution, the pentitol preferably includes at least one of the substances selected from the group consisting of xylitol, arabinitol, and ribitol.

[0012] In the above technical solution, the preferred additives include pentitol and hexitol. Hexitol alone is not effective in reducing the glucose content in the product material, but when pentitol and hexitol are used together, they have a synergistic effect in reducing the glucose content in the product material.

[0013] In the above technical solution, the preferred weight ratio of pentitol to hexitol is 0.05 to 0.8, for example, but not limited to, weight ratios of 0.06, 0.07, 0.08, 0.10, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.60, 0.65, 0.70, 0.75, etc.

[0014] In the above technical solution, the preferred hexitol is sorbitol.

[0015] The key technology of this invention is the use of additives in the acetal reaction of alkyl alcohols and carbohydrates. As for other process conditions required for the acetal reaction of alkyl alcohols and carbohydrates, as well as the process conditions for subsequent processing of the product materials, there are no particular restrictions. Those skilled in the art can still use the process conditions commonly used in the field.

[0016] In the above technical solution, the alkyl group in the alkyl alcohol is a C8 to C18 alkyl group. For example, but not limited to, C8 alkyl, C9 alkyl, C10 alkyl, C11 alkyl, C12 alkyl, C13 alkyl, C14 alkyl, C15 alkyl, C16 alkyl, C17 alkyl, C18 alkyl, etc., and the corresponding alkyl alcohol is at least one selected from the group consisting of C8 alkyl alcohol, C9 alkyl alcohol, C10 alkyl alcohol, C11 alkyl alcohol, C12 alkyl alcohol, C13 alkyl alcohol, C14 alkyl alcohol, C15 alkyl alcohol, C16 alkyl alcohol, C17 alkyl alcohol, and C18 alkyl alcohol. In the actual production of alkyl glycosides, C12-14 fatty alcohols are the most commonly used alkyl alcohols. C12-14 fatty alcohols are a mixture of n-dodecyl alcohol and n-tetradecyl alcohol. The typical weight ratio of C12 alcohol to C14 fatty alcohol in the market is 7:3, which is only a comparison. This is also the C12-14 fatty alcohol used in the specific implementation of this invention.

[0017] In the above technical solution, the preferred carbohydrate includes not only glucose, but also polysaccharides or monosaccharides other than glucose.

[0018] In the above technical solution, the polysaccharide is any sugar that can be hydrolyzed into glucose, and more preferably, the polysaccharide is starch.

[0019] In the above technical solution, the acidic catalyst is not particularly limited and can be any acidic catalyst known in the art. However, it is preferred that the acidic catalyst includes a compound containing a sulfonic acid group, and more preferably, the compound containing a sulfonic acid group includes aromatic sulfonic acids. For example, but not limited to, aromatic sulfonic acids are p-toluenesulfonic acid, dodecylbenzenesulfonic acid, or p-tert-butylbenzenesulfonic acid, etc.

[0020] In the above technical solution, the preferred method is that the molar ratio of alkyl alcohol to carbohydrate, based on the glucose structural units contained in the carbohydrate, is 2 to 6, for example, but not limited to, the molar ratio is 2.5, 3, 3.5, 4, 4.5, 5, 5.5, etc.

[0021] In the above technical solution, the preferred reaction temperature is 105–115°C.

[0022] Those skilled in the art know that the acetal reaction in the presence of an acidic catalyst is a reversible reaction that produces water, and timely removal of the water produced in the reaction is beneficial for the forward reaction. Those skilled in the art know that the main method for removing the water produced in the reaction is to reduce the absolute pressure to below atmospheric pressure, or to apply a vacuum. For example, to achieve dehydration, the reaction pressure, measured in absolute pressure gauges, can be 3–10 kPa, such as, but not limited to, 3.5 kPa, 4 kPa, 4.5 kPa, 5 kPa, 5.5 kPa, 6 kPa, 6.5 kPa, 7 kPa, 7.5 kPa, 8 kPa, 8.5 kPa, 9 kPa, 9.5 kPa, etc.

[0023] In the above technical solution, the preferred reaction time is 1 to 4 hours, such as, but not limited to, 1.5, 2, 2.5 hours, 3 hours, 3.5 hours, etc.

[0024] In the above technical solution, the preferred amount of acidic catalyst is 0.5% to 1.5% of the weight of carbohydrates. For example, but not limited to, 0.6%, 0.8%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, etc.

[0025] In the above technical solution, it is preferred that the amount of additive is greater than 0 and less than 1%, based on the weight of carbohydrates fed into the feed. For example, but not limited to, the amount of additive is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, etc., and it is even more preferred that the amount of additive is less than 0.5%.

[0026] In the above technical solution, the preferred method includes a step of neutralizing the product material.

[0027] In the above technical solution, the preferred method includes a step of removing free fatty alcohols.

[0028] In the above technical solution, the preferred method includes a decolorization step.

[0029] In the above technical solution, the preferred method includes a filtering step.

[0030] In this invention specification, the determination of glucose content in the product material adopts the direct titration method in GB5009.7-2016 (National Food Safety Standard for Determination of Reducing Sugars in Food). It should be noted that the sample preparation is carried out in accordance with the provisions of Section 5.1.4 of the standard. The specific method for sample preparation is as follows: Weigh 4 grams (accurate to 0.0001 g) of the alkyl glycoside synthesis product without the removal of fatty alcohol, place it in a 250 mL volumetric flask, add 50 mL of water, slowly add 5 mL of zinc acetate solution and 5 mL of potassium ferrocyanide solution, add water to the mark, mix well, let stand for 30 min, filter with dry filter paper, discard the initial filtrate, and keep the subsequent filtrate for later use.

[0031] The present invention will now be described in detail through examples and comparative examples. Detailed Implementation

[0032]

Comparative Example 1

[0033] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the temperature was raised and stirred. When the temperature reached 70°C, 3,700 kg of glucose was added, followed by 43 kg of p-toluenesulfonic acid. The circulation stirring was started, and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the material was transferred to a neutralization vessel. The neutralization vessel was neutralized to pH 9 with a 50% sodium hydroxide aqueous solution. The neutralized material was determined to contain 4.36% glucose by weight.

[0034] [Comparative Example 2]

[0035] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the temperature was raised and stirred. When the temperature reached 70°C, 3,700 kg of glucose and 14 kg of ethylene glycol were added, followed by 43 kg of p-toluenesulfonic acid. The circulation stirring was started, and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the material was transferred to a neutralization vessel. The neutralization vessel was neutralized with a 50% sodium hydroxide aqueous solution to a pH of 9 to obtain the neutralized material. The weight percentage of glucose remaining in the neutralized material was determined to be 3.98%.

[0036]

Example 1

[0037] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the temperature was raised and stirred. When the temperature reached 70°C, 3,700 kg of glucose and 14 kg of glycerol were added, followed by 43 kg of p-toluenesulfonic acid. The circulation stirring was started, and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the material was transferred to a neutralization vessel. The neutralization vessel was neutralized to pH 9 with a 50% sodium hydroxide aqueous solution. The neutralized material was determined to contain 2.69% glucose by weight.

[0038]

Example 2

[0039] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the temperature was raised and stirred. When the temperature reached 70°C, 3,700 kg of glucose and 14 kg of xylitol (CAS No. 87-99-0) were added, followed by 43 kg of p-toluenesulfonic acid. The circulation stirring was started, and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the material was transferred to a neutralization vessel. The neutralization vessel was neutralized to pH 9 with a 50% sodium hydroxide aqueous solution to obtain the neutralized material. The residual glucose content in the neutralized material was determined to be 1.51% by weight.

[0040]

Example 3

[0041] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the temperature was raised and stirred. When the temperature reached 70°C, 3,700 kg of glucose and 14 kg of sorbitol (CAS No. 50-70-4) were added, followed by 43 kg of p-toluenesulfonic acid. The circulation stirring was started, and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the material was transferred to a neutralization vessel. The neutralization vessel was neutralized to pH 9 with a 50% sodium hydroxide aqueous solution to obtain the neutralized material. The residual glucose content in the neutralized material was determined to be 2.96% by weight.

[0042]

Example 4

[0043] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the mixture was heated and stirred. When the temperature reached 70°C, 3,700 kg of glucose, 1 kg of xylitol (CAS No. 87-99-0), and 13 kg of sorbitol (CAS No. 50-70-4) were added, followed by 43 kg of p-toluenesulfonic acid. The mixture was then stirred and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the mixture was transferred to a neutralization vessel. The neutralization vessel was then neutralized to pH 9 with a 50% sodium hydroxide aqueous solution. The neutralized material was determined to contain 0.79% glucose by weight.

[0044]

Example 5

[0045] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the mixture was heated and stirred. When the temperature reached 70°C, 3,700 kg of glucose, 3 kg of xylitol (CAS No. 87-99-0), and 11 kg of sorbitol (CAS No. 50-70-4) were added, followed by 43 kg of p-toluenesulfonic acid. The mixture was then stirred and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the mixture was transferred to a neutralization vessel. The neutralization vessel was then neutralized to pH 9 with a 50% sodium hydroxide aqueous solution. The neutralized material was determined to contain 0.38% glucose by weight.

[0046]

Example 6

[0047] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the mixture was heated and stirred. When the temperature reached 70°C, 3,700 kg of glucose, 5 kg of xylitol (CAS No. 87-99-0), and 9 kg of sorbitol (CAS No. 50-70-4) were added, followed by 43 kg of p-toluenesulfonic acid. The mixture was then stirred and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the mixture was transferred to a neutralization vessel. The neutralization vessel was then neutralized to pH 9 with a 50% sodium hydroxide aqueous solution. The neutralized material was determined to contain 0.25% glucose by weight.

[0048]

Example 7

[0049] 16,200 kg of C12-14 fatty alcohol was added to the glycoside reaction vessel, and the temperature was raised and stirred. When the temperature reached 70°C, 3,700 kg of glucose, 6 kg of xylitol (CAS No. 87-99-0), and 8 kg of sorbitol (CAS No. 50-70-4) were added, followed by 43 kg of p-toluenesulfonic acid. The circulation stirring was started, and the internal pressure of the reaction vessel was controlled at 4.5 kPa. The temperature of the reaction vessel was raised to 110°C, and the reaction was carried out for 2 hours. After cooling to 70°C, the material was transferred to a neutralization vessel. The neutralization vessel was neutralized to pH 9 with a 50% sodium hydroxide aqueous solution to obtain the neutralized material. The residual glucose content in the neutralized material was determined to be 0.81% by weight.

Claims

1. A method for the synthesis of alkyl glycoside surfactants in a one-step process, comprising: An alkyl alcohol is reacted with a carbohydrate in the presence of an acidic catalyst and an additive molecule comprising at least one member selected from the group consisting of a triose alcohol, a tetrose alcohol, a pentose alcohol, and a hexose alcohol, the carbohydrate comprising glucose, to produce an alkyl glycoside-containing product mixture.

2. The method of claim 1, wherein: The triose alcohol is glycerol.

3. The method of claim 1, wherein: The pentose alcohol comprises at least one member selected from the group consisting of xylitol, arabitol, and ribitol.

4. The method of claim 1, wherein: The additive comprises a pentose alcohol and a hexose alcohol.

5. The method of claim 4, wherein: The hexose alcohol is sorbitol.

6. The method of claim 1, wherein The alkyl group in the alkyl alcohol is a C8-C18 alkyl group.

7. The method of claim 1 wherein The carbohydrate comprises, in addition to glucose, a polysaccharide or a monosaccharide other than glucose. The polysaccharide is one that is hydrolyzable to glucose, and more preferably the polysaccharide is starch.

8. The method of claim 1, wherein The acidic catalyst comprises a sulfonic acid group-containing compound.

9. The method of claim 1 wherein The molar ratio of the alkyl alcohol to the carbohydrate, based on the number of glucose structural units contained in the carbohydrate, is 2-6.

10. The method of claim 1, wherein The reaction temperature is 105-115°C. And / or preferably the absolute pressure of the reaction is 3-10 kPa. And / or preferably the reaction time is 1-4 hours. And / or preferably the amount of the acidic catalyst charged is 0.5-1.5% by weight of the carbohydrate. And / or preferably the amount of the additive charged, based on the weight of the carbohydrate charged, is more than 0 and 1% or less. And / or preferably the method comprises a step of neutralizing the product mixture, and more preferably a step of removing free fatty alcohol. And / or preferably a step of decolorizing. And / or preferably a step of filtering.

Images