CN114685262B

CN114685262B - Method for preparing ferulic acid from nigre

Info

Publication number: CN114685262B
Application number: CN202011611941.0A
Authority: CN
Inventors: 李磊; 丛芳; 黄超
Original assignee: Wilmar Shanghai Biotechnology Research and Development Center Co Ltd
Current assignee: Wilmar Shanghai Biotechnology Research and Development Center Co Ltd
Priority date: 2020-12-30
Filing date: 2020-12-30
Publication date: 2024-05-28
Anticipated expiration: 2040-12-30
Also published as: CN114685262A

Abstract

The invention relates to a method for preparing ferulic acid from nigre, which comprises the following steps: (1) Acid treatment is carried out on saponification liquid obtained by saponification of nigre to obtain an oil phase containing fatty acid and a water phase containing ferulic acid salt; (2) separating the oil phase and the aqueous phase; (3) separating ferulic acid from the aqueous phase by acid precipitation. The method can effectively separate fatty acid and ferulic acid, has simple process operation, does not change the existing equipment too much, and can realize production in factories quickly.

Description

Method for preparing ferulic acid from nigre

Technical Field

The present invention relates to a method for preparing ferulic acid from nigre.

Background

Ferulic acid (Ferulic Acid) is one of derivatives of cinnamic acid (also known as cinnamic acid, 3-phenyl-2-acrylic acid) with a chemical name of 4-hydroxy-3-methoxycinnamic acid. The ferulic acid has relative molecular weight 194.19, melting point 174 deg.c, slightly soluble in cold water, soluble in hot water, soluble in ethanol, methanol and acetone, insoluble in benzene and petroleum ether, and good pH stability.

The research for many years shows that the ferulic acid has multiple functions: has sedative effect on central nerve; anti-platelet aggregation and thrombosis; scavenging free radicals in the body; antibacterial and anti-inflammatory; protecting the cardiovascular system; increasing immunity; the product has good medicinal and edible values, and can be widely used in the fields of medicines, foods, cosmetics, pesticides, feed additives, etc.

Ferulic acid is commonly present in the plant kingdom and is widely distributed. The plant is mainly crosslinked with cell wall polysaccharide and lignin to form a part of cell wall, and is one of important effective components such as angelica, hemlock parsley, asafetida and the like. Wherein, the ferulic acid is also commonly existing in rice, mainly exists in the forms of cycloartenyl ferulate and sterol ferulate, commonly called oryzanol. In the rice oil processing process, most oryzanol can be remained in the soapstock, and the oryzanol content can be up to more than 30 percent (dry basis), so that the soapstock of the rice oil is an ideal raw material for producing ferulic acid.

The current methods for producing ferulic acid are mainly divided into four types: chemical synthesis, enzymatic hydrolysis, plant tissue culture and alkaline hydrolysis oryzanol. The main literature reports are as follows:

Deng Gong et al ("Process for preparing ferulic acid by alkaline hydrolysis of oryzanol by response surface method", "science and technology of food industry, 2013, stage 16) report that oryzanol is used as a raw material and alkaline hydrolysis thereof is optimized by response surface method to prepare ferulic acid. Based on a single factor experiment, three-factor and three-level experiments are carried out by using hydrolysis time, alkali concentration and substrate concentration as influencing factors and using a Box-Behnken center combination method, and response surface analysis is carried out by using ferulic acid yield as a response value. The result shows that the optimal technological conditions for preparing the ferulic acid by alkaline hydrolysis of oryzanol are as follows: the hydrolysis time is 12.5 hours, the alkali concentration (NaOH mass fraction) is 12%, the substrate concentration is 6.57mg/mL, the theoretical predicted value of the ferulic acid yield is 72.68%, the verification value is 71.33%, and the relative error with the predicted value is only 1.89%.

Zhang et al ("study of oryzanol production by Lip2 lipase of yarrowia lipolytica", "food industry science and technology, 2014, 22 nd) studied the enzymatic reaction system of yarrowia lipolytica (Yarrowia lipolytica) for the production of ferulic acid by the hydrolysis of oryzanol by lipase. The experiment shows that the yield of ferulic acid produced by hydrolyzing yarrowia lipolytica whole lipase powder (105U/mg) in 50mmol/L Tris-HCl pH7.0 (containing 7.5mmol/L Huang Dansuan sodium) and 100mmol/L sodium phosphate buffer pH6.0 (containing 1000U lipase) is 2.94%. In order to further improve the hydrolysis efficiency of lipase, the main component lip2 lipase gene in yarrowia lipolytica lipase is cloned and integrated into pichia pastoris GS115 genome to prepare lip2 lipase powder (70.1U/mg) by fermentation, and the hydrolysis oryzanol experiment is carried out in the enzymolysis system, and the experimental result shows that the ferulic acid yield is 2.87%.

Noor Hasyrierah Mohd Salleh et al, ("Optimization of alkaline hydrolysis of paddy straw for ferulic acid extraction",Industrial Crops and Products,2011, 11 months, volume 34, 3, pages 1635-1640) to improve the ferulic acid extraction rate by optimizing alkaline hydrolysis of straw in response to surface methods (RSM). The optimum process parameters were determined by screening temperature, naOH concentration and extraction time. After optimization, the ferulic acid content is improved from 0.518% to 0.817% (8.17 mg/g). The best conditions obtained in this study were temperature, naOH concentration and extraction time of 125 ℃,3.90m,2.30h.

Ma Shuyu et al ("oryzanol hydrolysis to ferulic acid", "Heilongjiang technological information", 2010, 14 th phase) determined the best process and purification method for oryzanol hydrolysis to ferulic acid. The method comprises the following steps: the optimal process for preparing the ferulic acid by oryzanol hydrolysis is determined by comparing the influences of different solvents, different reaction times and different alkali concentrations on oryzanol hydrolysis rate and ferulic acid yield and by orthogonal experiments, and the optimal purification method of the crude ferulic acid is determined by comparing the purification results of different purification methods. The results were: the optimal experimental condition of the reaction is that the reaction time is 9 hours, the alkali concentration is 25 percent, and the alcohol-alkali ratio is 5: and 5, the reaction solvent is n-butanol. The purification method comprises the following steps: dissolving in hot ethanol solution, cooling in ice water bath, and recrystallizing (sodium sulfite is added as antioxidant).

CN 101434535A discloses a method for preparing natural ferulic acid, after rice bran oil is squeezed from rice bran, rice husk and rice embryo bud or solvent is leached out, ferulic acid is extracted from by-products commonly called black feet after oryzanol is prepared from rice bran oil, fatty acid salt is used as dispersing agent, crude natural ferulic acid is prepared under the conditions of heating, pressurizing and stirring, and then pure ferulic acid is prepared through centrifugation, impurity removal, acid precipitation and refining. The final ferulic acid yield was 75%.

CN 109022501A discloses a method for obtaining ferulic acid by using waste, which comprises mixing distillers ' grains with bran, inoculating, culturing to obtain distillers ' grains solid fermentation product, extracting ferulic acid in distillers ' grains solid fermentation product by hot water extraction method.

The above documents are all researches on the production process of the ferulic acid, mainly focus on optimizing the preparation process of the ferulic acid, and few documents pay attention to recovering the ferulic acid from waste soapstock of rice oil.

Thus, there remains a need in the art for a more optimized process for preparing ferulic acid, including a process for preparing ferulic acid from waste soapstock containing ferulic acid and/or salts or esters thereof, produced by fat refining.

Disclosure of Invention

The invention relates to an acid method for preparing and separating ferulic acid in nigre. Specifically, the saponification liquid obtained by saponification of the soapstock is subjected to acid treatment, so that fatty acid in the saponification liquid is hydrochloric acid into fatty acid, and the ferulic acid exists in an aqueous phase in the form of salt, thereby realizing the separation of the ferulic acid.

In a first aspect, the present invention provides a method for preparing ferulic acid from soapstock, the method comprising the steps of:

(1) Acid treatment is carried out on saponification liquid obtained by saponification of nigre to obtain an oil phase containing fatty acid and a water phase containing ferulic acid salt;

(2) Separating the oil phase and the water phase;

(3) Separating ferulic acid from the aqueous phase by acid precipitation.

In one or more embodiments, the soapstock is produced from a fat refinery, such as from a rice oil refinery, or from a rice oil alkali treatment.

In one or more embodiments, the salt is an alkali metal salt, e.g., sodium salt, potassium salt.

In one or more embodiments, the acid used for the acid treatment is selected from mineral acids, preferably one or more selected from sulfuric acid, hydrochloric acid and phosphoric acid.

In one or more embodiments, the acid used in the acid treatment is sulfuric acid, the concentration of which in solution is 30-98%, preferably 30-50%.

In one or more embodiments, the acid used in the acid treatment is hydrochloric acid, the concentration of which solution is 5-10%.

In one or more embodiments, the acid used in the acid treatment is phosphoric acid, the concentration of which in solution is 20-40%.

In one or more embodiments, the acid precipitation includes adjusting the aqueous phase to a pH of 2-3 for 3-8 hours.

In one or more embodiments, the temperature of the reaction system is controlled between 50-70 ℃ during the acid treatment.

In one or more embodiments, the method comprises: adjusting pH of the saponified solution to below 7, such as 5-7 or 5.2-7, stirring thoroughly, separating oil phase and water phase, adjusting pH of water phase to 2-3, separating solid phase containing ferulic acid, and preparing ferulic acid; preferably, the pH of the saponified solution is adjusted to 7 or less within 30 minutes, and then allowed to react for 2 to 8 hours, during which stirring is performed.

In one or more embodiments, in the acid treatment, the pH is adjusted stepwise; wherein the stepwise adjustment of the pH comprises a first adjustment stage and a second adjustment stage.

In one or more embodiments, the first conditioning stage includes adjusting the pH of the saponified solution from an initial pH to 7.+ -. 0.3 at an average pH change rate of ≡0.1/min, preferably 0.1-0.3/min.

In one or more embodiments, the second conditioning stage includes adjusting the pH of the reaction system from about 7 to about 5.2 to about 5.4 at an average pH change rate of less than or equal to 0.05 per minute.

In one or more embodiments, in the second conditioning phase, the highest rate of pH change is no more than 0.08/min and the lowest rate of pH change is no less than 0.005/min.

In one or more embodiments, the conditioning time of the first conditioning stage is within 60 minutes.

In one or more embodiments, the conditioning time of the second conditioning phase is between 90 and 140 minutes.

In one or more embodiments, after the pH is adjusted to 5.2-5.4, the reaction is carried out for 2-6 hours, and then the oil phase and the aqueous phase are separated.

In one or more embodiments, in the first conditioning stage, the pH of the saponified solution is adjusted from the initial pH to 7.+ -. 0.3 in one or more portions, wherein the total conditioning time is within 60 minutes and the average rate of pH change throughout the first conditioning stage is greater than or equal to 0.1/minute, preferably from 0.1 to 0.3/minute.

In one or more embodiments, in the second conditioning stage, the pH of the saponified solution is adjusted from 7.+ -. 0.3 to 5.2-5.4 in one or more portions, wherein the total conditioning time is between 90-140 minutes, and the average pH change rate throughout the conditioning stage is less than or equal to 0.05/minute, preferably the highest pH change rate is no more than 0.08/minute, and the lowest pH change rate is no less than 0.005/minute.

In one or more embodiments, the second conditioning stage includes two stages, stage a adjusting the pH from 7±0.3 to an intermediate pH, such as 6±0.3, and stage b adjusting the pH of the reaction system from the intermediate pH to 5.2 to 5.4.

In one or more embodiments, the average rate of change of pH in stage A is in the range of 0.01 to 0.08 per minute; preferably, the highest pH change rate is not more than 0.08/min and the lowest pH change rate is not less than 0.01/min.

In one or more embodiments, the average rate of pH change of the B-stage is in the range of 0.005-0.02/min.

In one or more embodiments, the average rate of pH change of the B stage is lower than the average rate of pH change of the a stage.

In one or more embodiments, the rate of pH change of the B-stage is no more than 0.02/min at the highest and no less than 0.005/min at the lowest.

In one or more embodiments, the first conditioning stage comprises adjusting the pH of the saponified solution from an initial pH to 7+ -0.3 within 30 minutes, and entering the second conditioning stage after a period of reaction, wherein the total time of the first conditioning stage does not exceed 60 minutes, or entering the second conditioning stage directly after adjusting the pH of the saponified solution to 7+ -0.3 within 60 minutes.

In one or more embodiments, the second conditioning stage comprises a stage a comprising first conditioning the saponification liquor to a pH of from 7±0.3 to 6±0.3 at a first average pH change rate over 30 minutes, reacting for 20-40 minutes, or immediately after conditioning the saponification liquor to a pH of from 7±0.3 to 6±0.3 at a first average pH change rate over 60 minutes, and a stage B comprising conditioning the reaction system to a pH of from 6±0.3 to 5.2-5.4 at a second average pH change rate; preferably, the average pH change rate of stage A is in the range of 0.01-0.08/min, the second average pH change rate is in the range of 0.005-0.02/min, and the first average pH change rate is higher than the second average pH change rate.

In one or more embodiments, the method comprises:

(1) Adding the inorganic acid solution into the saponification liquid obtained by saponification of the soapstock at 50-70 ℃, reducing the pH of the saponification liquid to 7+/-0.3 within 30 minutes, and then stirring for 20-40 minutes;

(2) Adding the inorganic acid solution into the mixed solution after the reaction in the step (1), reducing the pH of the mixed solution from 7+/-0.3 to 6+/-0.3 in 30 minutes, and stirring for 20-40 minutes;

(3) Adding the inorganic acid solution into the mixed solution after the reaction in the step (2), reducing the pH of the mixed solution from 6+/-0.3 to 5.2-5.4 in 30 minutes, and then stirring for 2-6 hours, wherein the pH is maintained in the range of 5.2-5.4;

(4) Separating the oil phase and the water phase in the mixed solution after the reaction in the step (3);

(5) And (3) regulating the pH value of the water phase obtained in the step (4) to 2-3, and carrying out acid precipitation to precipitate the ferulic acid.

The second aspect of the invention provides the use of an inorganic acid in the preparation of ferulic acid from spent soapstock produced by refining of oil and fat; preferably, the mineral acid is selected from one or more of sulfuric acid, hydrochloric acid and phosphoric acid; preferably, the mineral acid is sulfuric acid, the concentration of which is 30-98%, preferably 30-50%, or the mineral acid is hydrochloric acid, the concentration of which is 5-10%, or the mineral acid is phosphoric acid, the concentration of which is 20-40%.

In one or more embodiments, the preparation is performed using the methods described in any of the embodiments of the invention.

Detailed Description

So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and in the event of a conflict, the present specification shall control.

The theory or mechanism described and disclosed herein, whether right or wrong, is not meant to limit the scope of the invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.

All features such as amounts, and concentrations recited herein are presented herein in a numerical range or a percent range format for brevity and convenience only. Accordingly, the description of a numerical range or percentage range should be considered to cover and specifically disclose all possible sub-ranges and individual values (including integers and fractions) within the range.

In this context, not all possible combinations of the individual technical features in the individual embodiments or examples are described in order to simplify the description. Accordingly, as long as there is no contradiction between the combinations of these technical features, any combination of the technical features in the respective embodiments or examples is possible, and all possible combinations should be considered as being within the scope of the present specification.

The main ingredient of the soapstock is sodium fatty acid, which is an emulsifier, so that the soapstock has the main characteristic of containing a large amount of water (about 50%), and the water cannot be separated by conventional means such as centrifugation and pH adjustment. Therefore, based on the characteristics of the soapstock, in the conventional production process of the ferulic acid, about 2-4% of the ferulic acid is still entrained by the water in the waste soapstock, so that the yield of the ferulic acid is reduced. The main components of the saponification liquid of waste soapstock are fatty acid salts, including linoleate, oleate, stearate, palmitate and the like, and are mainly sodium salts, the pKa of which is 4.77, 5.02, 4.75 and 4.95, and the pKa of ferulic acid is 4.58 (carboxyl) and 4.42 (phenolic hydroxyl), so that the difference between the pKa of ferulic acid and the pKa of fatty acid is small, and the ferulic acid cannot be separated by simply adjusting the pH value. The invention relates to a method for preparing and separating ferulic acid in saponification liquid of waste nigre by an acid method. Further, the present invention has found that if the pH of the acidification is controlled stepwise, the fatty acid in the saponified solution of waste soapstock can be more effectively hydrochlorinated to fatty acid, and the ferulic acid still exists in the aqueous phase in the form of salt, thereby more effectively separating fatty acid and ferulic acid. The process is simple to operate, does not change the existing equipment too much, and can realize production in factories quickly.

The acid method is to treat the saponification liquid of waste nigre by acid, especially inorganic acid, to make fatty acid in the saponification liquid of waste nigre hydrochloric acid into fatty acid, while ferulic acid still exists in salt form, then separate out ferulic acid in salt form in water phase, and acid out under acid condition, and separate out ferulic acid.

Acid precipitation as used herein refers to precipitation of ferulic acid from a solution under acidic conditions, e.g. at a pH of 2-3, to form a solid. The acid used for the acid precipitation is not particularly limited as long as it can adjust the pH to 2 to 3 and does not react with ferulic acid.

Acids suitable for use in the present invention are preferably inorganic acids, more preferably strong acids, i.e., acids having a pKa of less than 1, including but not limited to sulfuric acid, hydrochloric acid, and phosphoric acid. The concentration of the acid solution to be used is not particularly limited as long as it can provide a sufficient amount of protons within the conditions defined in the method of the present invention, and the pH of the reaction system is reduced within the range defined in the present invention. For example, the invention may be practiced using the highest concentration sulfuric acid solution (about 98%), hydrochloric acid solution (about 37%) or phosphoric acid solution (about 85%) known in the art. It should be understood that in general, the saponification liquid (containing soapstock and water) used for the reaction may have a mass of water 1.5 to 3 times the mass of soapstock, i.e., the water content may be 60 to 75%; however, when a highly concentrated acid solution (e.g., 98% concentrated sulfuric acid) is used, the water content in the saponified solution is preferably not less than 80% by weight, more preferably not less than 90% by weight, for sufficient contact of the reactants. In some embodiments, the concentration of the sulfuric acid solution may be 30-98wt%. Preferably, the concentration of the sulfuric acid solution is 30-50wt%. In some embodiments, the concentration of hydrochloric acid solution used may be 5-10wt%. In some embodiments, the concentration of phosphoric acid solution used may be 20-40wt%.

In the invention, nigre has the meaning known in the art, and generally refers to a byproduct produced in the process of alkali refining animal and vegetable oil and fat, and is a product of a deacidification section. The soapstock is generally subjected to saponification treatment, i.e., alkali treatment of the soapstock to react with the grease remaining in the soapstock and produce fatty acid salts. Saponification reaction conditions of soapstock are well known in the art. For example, depending on the composition of the soapstock, the saponification reaction temperature may be 110-130 ℃, the alkali addition may be 15-30% of the dry soapstock mass, the alkali may be solid caustic soda flakes, and the water addition may be 150-300% of the dry soapstock mass.

Saponification treatment is carried out on nigre to obtain saponification liquid, namely the raw material for preparing ferulic acid. The saponification liquid generally contains fatty acid salts and ferulic acid salts, and the types of the salts are related to alkali refining and alkali used for saponification treatment, and can be sodium salts, calcium salts and the like. The soapstock suitable for use in the present invention may be soapstock from alkali refining of various oils and fats, as long as it contains ferulic acid. In a specific embodiment, the soapstock may be soapstock from alkali refining of rice oil, and the saponified solution is a saponified solution obtained after saponification of soapstock from alkali refining of rice oil.

The method for preparing ferulic acid from nigre (preferably waste nigre generated by refining grease) comprises the following steps:

(2) Separating the oil phase and the water phase;

(3) Separating ferulic acid from the aqueous phase by acid precipitation.

In general, the pH of the saponified solution is adjusted to 7 or less, for example, 5 to 7 or 5.2 to 7, and after the reaction with stirring, the oil phase and the water phase are separated, and the pH of the water phase is adjusted to 2 to 3 to precipitate ferulic acid, thereby obtaining ferulic acid. In some embodiments, the pH of the saponified solution is adjusted to below 7 within 30 minutes and then allowed to react for 2-8 hours, during which time agitation is performed. In some embodiments, the aqueous phase is acidified for 3 to 8 hours after the pH of the aqueous phase is adjusted to 2 to 3. Preferably, the acid treatment is performed using an inorganic acid, preferably using one or more of sulfuric acid, hydrochloric acid and phosphoric acid. Preferably, the concentration of the sulfuric acid solution is 30-50%; preferably, the concentration of the hydrochloric acid solution is 5-10%; preferably, the concentration of the phosphoric acid solution is 20-40%.

In general, the invention adjusts the pH of the reaction system by continuously adding an acid solution. In the reaction process, the temperature of the reaction system (saponification liquid) is controlled between 50 ℃ and 70 ℃. The acid precipitation may be performed at room temperature.

The present invention has found that if the pH of the acidification (i.e., acid treatment) is adjusted stepwise, the fatty acid in the waste soapstock can be more effectively hydrochloric acid to fatty acid, while the ferulic acid still exists in the aqueous phase in the form of salt, thereby more effectively separating the fatty acid from the ferulic acid. Specifically, the pH stepwise adjustment of the present invention includes a first adjustment stage (adjustment from pH of saponification liquid to about 7) and a second adjustment stage (adjustment from about 7 to reaction pH). Preferably, in the first adjustment stage, the pH value of the saponified solution is adjusted from an initial pH value to about 7 at an average pH value change rate of 0.1/min or more, preferably 0.1-0.3/min; preferably, the second adjustment stage adjusts the pH of the reaction system from about 7 to the reaction pH at an average pH change rate of less than or equal to 0.05/min (preferably the highest pH change rate is not more than 0.08/min, and the lowest pH change rate is not less than 0.005/min, i.e., the pH change range is 0.005-0.08/min). Preferably, the reaction pH is from 5.2 to 5.4. Preferably, the conditioning time of the first conditioning phase is within 60 minutes. Preferably, the conditioning time of the second conditioning phase is between 90 and 140 minutes. In some embodiments, prior to the first conditioning stage, a step of adjusting the saponification liquor pH of the spent soapstock to 13 is also included. In some embodiments, the step of adjusting the saponification liquor of the waste soapstock to pH 13 may be by reducing the pH to pH 13 by the addition of acid or increasing the pH to pH 13 by the addition of base.

In some embodiments, in the first conditioning stage, the pH of the saponified solution is adjusted from the initial pH to 7.+ -. 0.3 in one or more portions, wherein the total conditioning time of the entire conditioning stage is controlled to within 60 minutes, and the average rate of pH change of the entire first conditioning stage is greater than or equal to 0.1/minute, preferably from 0.1 to 0.3/minute. In some embodiments, in the second adjustment stage, the pH of the saponified solution is adjusted from 7.+ -. 0.3 to 5.2-5.4 in one or more portions, wherein the total adjustment time is between 90-140 minutes, and the average pH change rate throughout the adjustment stage is less than or equal to 0.05/minute, preferably the highest pH change rate is no more than 0.08/minute, and the lowest pH change rate is no less than 0.005/minute. In this context, the term "one or more times" means that, during the pH adjustment process, an acid solution may be continuously added, the pH of the saponification liquid may be directly adjusted to a preset pH value, or a part of the acid solution may be added first to adjust the pH value of the saponification liquid to a certain pH value, then the reaction is performed for a period of time, then the acid solution is continuously added to adjust the pH value to a certain pH value, then the reaction is performed for a period of time, and so on until the preset pH value is reached.

In some embodiments, during the first adjustment stage, the pH of the reaction system may be adjusted to about 7 in a short period of time, such as 10-20 minutes, and then reacted at that pH for a period of time, followed by a second adjustment, provided that the average rate of change of pH and preferably the total adjustment time throughout the first adjustment stage prior to the second adjustment meets the requirements described herein; alternatively, the initial pH of the saponification liquor may be adjusted to a set pH, such as 9, where the pH is reacted for a period of time, then to a next set pH, such as 8, where the reaction is followed by a period of time, such as 7, as desired, provided that the average rate of pH change throughout the stage and preferably the total adjustment time meet the requirements set forth herein. Likewise, in the second adjustment stage, the pH may be adjusted to a set pH value first, after a period of reaction, to a next set pH value, after a period of reaction, and so on until the final reaction pH value is reached, as long as the average rate of change of the pH value throughout the second adjustment stage and preferably the total adjustment time meet the requirements described herein. Herein, the average pH change rate= (initial pH value-target pH value)/time (min). For example, an initial pH of 13, a target pH of 7, and a total conditioning time of 60 minutes, the average pH change rate is (13-7)/60=0.1.

Preferably, the pH of the first adjustment stage of the present invention has an end pH of 7.+ -. 0.3 and the second adjustment stage has an end pH (i.e., reaction pH) of 5.2 to 5.4.

Preferably, in some embodiments, the second adjustment stage comprises two stages, stage a is to adjust the pH from the end pH of the first adjustment stage to an intermediate pH, which may be 6±0.3, and stage b is to adjust the pH of the reaction system from the intermediate pH to the reaction pH, i.e., 5.2-5.4. In a preferred embodiment, the average pH change rate in stage A is in the range of 0.01 to 0.08 per minute; preferably, the highest pH change rate is not more than 0.08/min and the lowest pH change rate is not less than 0.01/min. Preferably, the average pH change rate of the B-stage is in the range of 0.005-0.02/min, preferably the average pH change rate of the B-stage is lower than the average pH change rate of the A-stage. More preferably, the pH change rate of the B-stage is at most 0.02/min or more and at most 0.005/min or less. Preferably, the rate of change of pH in the second conditioning phase is gradually reduced from a relatively higher rate in the initial phase to a lower rate in the final conditioning phase.

In a preferred embodiment, the first adjustment stage adjusts the pH of the saponification liquor from the initial pH of the saponification liquor to 7+ -0.3; the second regulation stage comprises two stages, wherein the A stage firstly regulates the pH value of the saponified solution from 7+/-0.3 to 6+/-0.3 according to the first average pH value change rate, and the B stage secondly regulates the pH value from 6+/-0.3 to 5.2-5.4 according to the second average pH value change rate; wherein the first average pH value change rate is in the range of 0.01-0.08/min, the second average pH value change rate is in the range of 0.005-0.02/min, the first average pH value is higher than the second average pH value, and the pH change rate in the A stage is higher than the pH change rate in the B stage.

In some embodiments, the first conditioning stage comprises adjusting the pH of the saponified solution to 7+ -0.3 within 30 minutes, entering the second conditioning stage after a period of time, wherein the total time of the conditioning stages does not exceed 60 minutes, or entering the second conditioning stage directly after adjusting the pH of the saponified solution to 7+ -0.3 within a period of time (e.g., within 60 minutes); the second adjusting stage comprises an A stage and a B stage, wherein the A stage comprises the steps of firstly adjusting the pH value of the saponification liquid from 7+/-0.3 to 6+/-0.3 at a first average pH value change rate within 30 minutes, firstly reacting for a period of time (such as 20-40 minutes), then entering the B stage, or immediately entering the B stage after adjusting the pH value from 7+/-0.3 to 6+/-0.3 at a first average pH value change rate within a period of time (such as 60 minutes), and the B stage comprises the step of adjusting the pH value of a reaction system from 6+/-0.3 to 5.2-5.4 at a second average pH value change rate; preferably, the average pH change rate of stage A is in the range of 0.01-0.08/min, the second average pH change rate is in the range of 0.005-0.02/min, and the first average pH change rate is higher than the second average pH change rate.

After the pH of the saponified solution is adjusted to the reaction pH (5.2 to 5.4), the reaction is carried out for a period of time, preferably 2 to 6 hours, whereby the acid treatment of the saponified solution is completed.

The pH is adjusted and the reactants are fully contacted by stirring during the reaction.

In the acid treatment, the same or different acids may be used for each adjustment of the pH; when the same acid is used, the concentration of the acid solution may be the same or different, so long as the pH of the saponified solution can be adjusted to a set pH, and preferably the pH of the saponified solution can be adjusted to a set pH within the time defined in the present invention.

After the acid treatment, the oil phase and the water phase in the saponified solution can be separated by conventional technical means. The aqueous phase contains ferulic acid salt. The ferulic acid can be obtained by carrying out acid precipitation on the water phase, namely, adjusting the pH of the water phase to 2-3, and reacting for 3-8 hours. Likewise, stirring can be performed during the acid precipitation process to allow the ferulic acid to be sufficiently precipitated.

The invention further discovers that under the condition of adjusting the pH value in a sectional way, if the concentration of the used acid is further selected, the yield of the ferulic acid can be further improved. In particular, the present invention has found that higher yields of ferulic acid can be obtained using sulfuric acid solutions having concentrations of 30-50%. In a preferred embodiment, the acid treatment is carried out by stepwise adjustment of the pH of the saponification liquor. Preferably, the pH of the saponification liquid is adjusted from the initial pH to 7+/-0.3, the pH of the saponification liquid is adjusted from 7+/-0.3 to 6+/-0.3 after a period of reaction, the pH of the saponification liquid is adjusted from 6+/-0.3 to 5.2-5.4 after a period of reaction, and then the saponification liquid is reacted for a period of time, so that the acid treatment of the saponification liquid is completed. Preferably, each adjustment of the pH is completed within 30 minutes. Preferably, the pH of the saponification liquid is adjusted to 7+/-0.3, and the saponification liquid is reacted for 20-40 minutes; preferably, after the pH value of the saponification liquid is adjusted from 7+/-0.3 to 6+/-0.3, the saponification liquid is reacted for 20-60 minutes; preferably, the saponification liquid is reacted for 2-6 hours after the pH value of the saponification liquid is adjusted from 6+ -0.3 to 5.2-5.4. In a preferred embodiment, 30-50% sulfuric acid solution is used for the calculation process.

After the ferulic acid is separated, the ferulic acid can be dried. The method of drying is conventional in the art.

The invention will be illustrated by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the invention. Unless otherwise indicated, the methods, reagents and materials used in the examples are those conventional in the art, as well as those commercially available. Soapstock was purchased from the xingwang oil mill in the brocade market (where oryzanol content was 32.1% (dry basis), converted to ferulic acid content was 12.07%). The saponification method comprises the following steps: adding 200% of water and 120% of caustic soda flakes into the soapstock by mass, and reacting at 120 ℃ in a closed reaction kettle for 4 hours to obtain the product.

The calculation method of the ferulic acid yield comprises the following steps:

Ferulic acid yield = quality of product x ferulic acid purity/quality of oryzanol all converted to ferulic acid comparative example 1 (control of acidification pH at 7)

Placing saponified solution (containing nigre and water phase, the mass of water phase being 2 times of that of nigre) into beaker, stirring and heating to 60deg.C; adding concentrated sulfuric acid into the beaker, reducing the pH value of the system from 13 to 7 within 30min, and continuing to react for 4h; stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 32.95%.

Comparative example 2 (control of acidification pH 5.2, concentrated sulfuric acid)

Placing saponified solution (containing nigre and water phase, the mass of water phase being 2 times of that of nigre) into beaker, stirring and heating to 60deg.C; adding concentrated sulfuric acid into the beaker, reducing the pH value of the system from 13 to 7 within 30min, and continuing to react for 30min; slowly adding concentrated sulfuric acid into the beaker, reducing the pH value in the system from 7 to 6 within 30min, and stopping adding acid to react for 30min at the pH value; continuously adding concentrated sulfuric acid into the beaker in a slow flow manner, reducing the pH value in the system from 6 to 5.2 within 30min, and stopping adding acid, and reacting for 4h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.2. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 37.89%.

Example 1 (control of acidification pH 5.2, concentration of sulfuric acid solution 30%)

Placing saponified solution (containing nigre and water phase, the mass of water phase being 2 times of that of nigre) into beaker, stirring and heating to 60deg.C; adding 30% sulfuric acid solution into a beaker, reducing the pH value of the system from 13 to 7 within 30min, and continuing to react for 30min; slowly feeding sulfuric acid solution with the concentration of 30% into a beaker, reducing the pH value in the system from 7 to 6 within 30min, stopping adding acid, and reacting for 30min at the pH value; continuously feeding sulfuric acid solution with the concentration of 30% into a beaker slowly, reducing the pH value in the system from 6 to 5.2 in 30min, and stopping adding acid, and reacting for 4h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.2. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 57.72%.

Example 2 (control of acidification pH 5.4, concentration of sulfuric acid solution 30%)

Placing saponified solution (containing nigre and water phase, the mass of water phase being 2 times of that of nigre) into beaker, stirring and heating to 60deg.C; adding 30% sulfuric acid solution into a beaker, reducing the pH value of the system from 13 to 7 within 30min, and continuing to react for 30min; slowly feeding sulfuric acid solution with the concentration of 30% into a beaker, reducing the pH value in the system from 7 to 6 within 30min, stopping adding acid, and reacting for 30min at the pH value; continuously feeding sulfuric acid solution with the concentration of 30% into a beaker slowly, reducing the pH value in the system from 6 to 5.4 in 30min, and stopping adding acid, and reacting for 4h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.4. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 50.16%.

Example 3 (control of acidification pH 5.2, concentration of sulfuric acid solution 50%)

Placing saponified solution (containing nigre and water phase, the mass of water phase being 2 times of that of nigre) into beaker, stirring and heating to 60deg.C; adding 50% sulfuric acid solution into a beaker, reducing the pH value of the system from 13 to 7 within 30min, and continuing to react for 30min; slowly feeding sulfuric acid solution with the concentration of 50% into a beaker, reducing the pH value in the system from 7 to 6 within 30min, stopping adding acid, and reacting for 30min at the pH value; continuously feeding 50% sulfuric acid solution slowly into the beaker, reducing the pH value in the system from 6 to 5.2 within 30min, and stopping adding acid, and reacting for 4h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.2. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 48.23%.

Example 4 (control of acidification pH 5.4, concentration of sulfuric acid solution 50%)

Placing saponified solution (containing nigre and water phase, the mass of water phase being 2 times of that of nigre) into beaker, stirring and heating to 60deg.C; adding 50% sulfuric acid solution into a beaker, reducing the pH value of the system from 13 to 7 within 30min, and continuing to react for 30min; slowly feeding sulfuric acid solution with the concentration of 50% into a beaker, reducing the pH value in the system from 7 to 6 within 30min, stopping adding acid, and reacting for 30min at the pH value; continuously feeding 50% sulfuric acid solution slowly into the beaker, reducing the pH value in the system from 6 to 5.4 within 30min, and stopping adding acid, and reacting for 4h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.4. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 49.82%.

Example 5 (control of the Water content of the System, acidification pH 5.4, sulfuric acid concentration 98%)

Placing saponified solution (containing waste soapstock and water phase, wherein the mass of the water phase is 2 times of that of the waste soapstock) into a beaker, adding pure water with the mass equal to that of the saponified solution, stirring and heating to 60 ℃; adding concentrated sulfuric acid into the beaker, reducing the pH value of the system from 13 to 7 within 30min, and continuing to react for 30min; slowly adding concentrated sulfuric acid into the beaker, reducing the pH value in the system from 7 to 6 within 30min, and stopping adding acid to react for 30min at the pH value; continuously adding concentrated sulfuric acid into the beaker in a slow flow manner, reducing the pH value in the system from 6 to 5.4 within 30min, and stopping adding acid, and reacting for 4h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.4. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is 42.31 percent.

Example 6 (control of acidification pH 5.4, concentration of hydrochloric acid solution 8%)

Placing saponified solution (containing waste soapstock and water phase, wherein the mass of the water phase is 2 times of that of the waste soapstock) into a beaker, adding pure water with the mass equal to that of the saponified solution, stirring and heating to 60 ℃; hydrochloric acid with the concentration of 8% is fed into a beaker, the pH value of the system is reduced from 13 to 6.9 within 30min, and the reaction is continued for 40min; slowly feeding hydrochloric acid with the concentration of 8% into the beaker, reducing the pH value in the system from 7 to 6.1 within 30min, stopping feeding the hydrochloric acid, and reacting for 50min at the pH value; continuously feeding hydrochloric acid with the concentration of 8% into the beaker slowly, reducing the pH value in the system from 6 to 5.4 within 30min, and stopping adding acid, and reacting for 5h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.4. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 6 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is 45.29 percent.

Example 7 (control of acidification pH 5.2, concentration of phosphoric acid solution 35%)

Placing saponified solution (containing waste soapstock and water phase, wherein the mass of the water phase is 2 times of that of the waste soapstock) into a beaker, adding pure water with the mass equal to that of the saponified solution, stirring and heating to 60 ℃; adding 35% phosphoric acid solution into the beaker, reducing the pH value of the system from 13 to 7.1 within 30min, and continuing to react for 25min; slowly feeding a phosphoric acid solution with the concentration of 35% into a beaker, reducing the pH value in the system from 7 to 5.9 within 30min, stopping adding phosphoric acid, and reacting for 45min at the pH value; continuously feeding 35% phosphoric acid solution into the beaker slowly, reducing the pH value in the system from 6 to 5.4 in 30min, and stopping adding acid, and reacting for 5h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.2. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 6 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is 49.22 percent.

Example 8 (control of acidification pH 5.2, concentration of sulfuric acid solution 30-50%)

Placing saponified solution (containing waste soapstock and water phase, wherein the mass of the water phase is 2 times of that of the waste soapstock) into a beaker, stirring and heating to 60 ℃; adding 30% sulfuric acid solution into a beaker, reducing the pH value of the system from 13 to 7 within 30min, and continuing to react for 30min; slowly feeding sulfuric acid solution with the concentration of 50% into a beaker, reducing the pH value in the system from 7 to 6 within 30min, stopping adding acid, and reacting for 30min at the pH value; continuously feeding 35% sulfuric acid solution slowly into the beaker, reducing the pH value in the system from 6 to 5.2 in 30min, and stopping adding acid, and reacting for 4h at the pH value. The pH value of the system can rise in the reaction process, and acid is added dropwise in time to maintain the pH value to be 5.2. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is 48.22 percent.

Example 9 (control of acidification pH 5.2, concentration of sulfuric acid solution 30%)

Placing saponified solution (containing nigre and water phase, the mass of water phase being 2 times of that of nigre) into beaker, stirring and heating to 60deg.C; adding 30% sulfuric acid solution into a beaker in a flowing way to reduce the pH value of the system from 13 to 7, and controlling the change rate of the pH value to be 0.15/min; slowly feeding sulfuric acid solution with the concentration of 30% into the beaker to reduce the pH value from 7 to 6, wherein the pH value change rate is 0.05/min; continuously feeding sulfuric acid solution with the concentration of 30% into the beaker slowly so as to reduce the pH value in the system from 6 to 5.2, wherein the pH value change rate is 0.01/min, and reacting for 2h at the pH value. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 49.88%.

Example 10 (control of acidification pH 5.2, concentration of sulfuric acid solution 30%)

Placing saponified solution (containing waste soapstock and water phase, wherein the mass of the water phase is 2 times of that of the waste soapstock) into a beaker, stirring and heating to 60 ℃; adding 30% sulfuric acid solution into a beaker in a flowing way to reduce the pH value of the system from 13 to 7, and controlling the change rate of the pH value to be 0.2/min; slowly feeding sulfuric acid solution with the concentration of 30% into the beaker to reduce the pH value from 7 to 6, wherein the pH value change rate is 0.07/min; continuously feeding sulfuric acid solution with the concentration of 30% into the beaker slowly so as to reduce the pH value in the system from 6 to 5.2, wherein the pH value change rate is 0.008/min, and reacting for 2h at the pH value. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 46.20%.

Example 11 (control of acidification pH 5.2, concentration of sulfuric acid solution 40%)

Placing saponified solution (containing waste soapstock and water phase, wherein the mass of the water phase is 2 times of that of the waste soapstock) into a beaker, stirring and heating to 60 ℃; adding 40% sulfuric acid solution into a beaker in a flowing way to reduce the pH value of the system from 13 to 7, and controlling the change rate of the pH value to be 0.1/min; slowly feeding sulfuric acid solution with the concentration of 30% into the beaker to reduce the pH value from 7 to 6, wherein the pH value change rate is 0.02/min; continuously feeding sulfuric acid solution with the concentration of 30% into the beaker slowly so as to reduce the pH value in the system from 6 to 5.2, wherein the pH value change rate is 0.01/min, and reacting for 2h at the pH value. Stopping heating and stirring after the reaction is finished to thoroughly separate the oil phase and the water phase, adjusting the pH value of the separated water phase to 2-3 to separate out the ferulic acid, and filtering after acid separation for 5 hours to obtain the ferulic acid; and (3) drying the ferulic acid to obtain a ferulic acid product, wherein the yield of the ferulic acid is calculated to be 45.72%.

Claims

1. A method for preparing ferulic acid from soapstock, comprising the steps of:

In the acid treatment, the pH is adjusted in a sectional manner; wherein the step of adjusting the pH value comprises a first adjusting stage and a second adjusting stage; in the first adjusting stage, the pH value of the saponified solution is adjusted from the initial pH value to 7+/-0.3 in one or more times, wherein the total adjusting time is within 60 minutes, and the average pH value change rate of the whole first adjusting stage is 0.1-0.3/min;

The second adjusting stage adjusts the pH value at the average pH value change rate less than or equal to 0.05/min, the second adjusting stage comprises two stages, the A stage adjusts the pH value from 7+/-0.3 to the intermediate pH value of 6+/-0.3, and the average pH value change rate of the A stage is in the range of 0.01-0.08/min; b, adjusting the pH value of the reaction system from the intermediate pH value to 5.2-5.4; the average pH change rate of the B-stage is in the range of 0.005-0.02/min; the average pH change rate of the B stage is lower than that of the A stage;

The acid used in the acid treatment is sulfuric acid, the concentration of the solution is 30-50%, or the acid used in the acid treatment is hydrochloric acid, the concentration of the solution is 5-10%, or the acid used in the acid treatment is phosphoric acid, the concentration of the solution is 20-40%;

(2) Separating the oil phase and the water phase;

(3) Separating ferulic acid from the aqueous phase by acid precipitation.

2. The method of claim 1, wherein the method has one or more of the following features:

The soapstock is produced by refining grease;

The salt is an alkali metal salt;

The acid separation comprises the steps of adjusting the pH value of the water phase to 2-3 and reacting for 3-8 hours; and/or

In the acid treatment process, the temperature of the reaction system is controlled between 50 ℃ and 70 ℃.

3. The method of claim 2, wherein the method has one or more of the following features:

the soapstock is produced by refining rice oil or by alkali treatment of rice oil;

The alkali metal salt is sodium salt and/or potassium salt.

4. The method of any one of claims 1-2, wherein the method comprises one or more of the following features:

the adjusting time of the second adjusting stage is between 90 and 140 minutes;

after the pH is adjusted to 5.2-5.4, the reaction is carried out for 2-6 hours, and then the oil phase and the water phase are separated.

5. The method of claim 1, wherein the first conditioning stage comprises adjusting the pH of the saponified solution from an initial pH to 7±0.3 within 30 minutes, and entering the second conditioning stage after a period of reaction, wherein the total time of the conditioning stage does not exceed 60 minutes, or entering the second conditioning stage directly after adjusting the pH of the saponified solution to 7±0.3 within 60 minutes; and/or

The second regulation stage comprises a stage A and a stage B, wherein the stage A comprises the steps of regulating the pH value of the saponification liquid from 7+/-0.3 to 6+/-0.3 at a first average pH value change rate within 30 minutes, reacting for 20-40 minutes, entering the stage B, or regulating the pH value from 7+/-0.3 to 6+/-0.3 at a first average pH value change rate within 60 minutes, and immediately entering the stage B, and the stage B comprises the step of regulating the pH value of a reaction system from 6+/-0.3 to 5.2-5.4 at a second average pH value change rate.

6. The method of claim 5, wherein the first average rate of change of pH is higher than the second average rate of change of pH.

7. The method according to any one of claims 1-2, wherein the method comprises:

(1) Adding inorganic acid solution into saponification liquid obtained by saponification of soapstock at 50-70 ℃, reducing pH of the saponification liquid to 7+ -0.3 within 30 minutes, and stirring for 20-40 minutes;