Residual acid analysis method for alcohol compounds

Abstract

The invention discloses a residual acid analysis method for alcohol compounds. The method comprises the following steps: providing an organic solvent, and putting the organic solvent into a distiller to distill the organic solvent and obtain a purified organic solvent in a distillation middle section; mixing a basic inorganic compound with the purified organic solvent to produce a titration liquid; mixing a diol compound with the purified organic solvent to generate a sample to be detected; and carrying out acid-base titration on the to-be-detected sample by using the titration liquid so as to analyze the acid residual quantity of the diol compound. Wherein the equivalent concentration of the alkaline inorganic compound in the titration liquid is not more than 0.005 N. Therefore, the detection accuracy of the residual acid analysis of the alcohol compounds can reach the concentration grade which is low enough, and the detection limit is improved.

Description

Technical Field

[0001] The present invention relates to a compound analysis method, in particular to a residual acid analysis method of an alcohol compound. Background Art

[0002] In the prior art, when diol compounds (e.g., dihydroxyaromatic compounds) are used as raw materials in transesterification reactions, alkali metal hydroxides, such as potassium hydroxide (KOH) or sodium hydroxide (NaOH), are often used as auxiliary reagents to catalyze the transesterification. However, when the auxiliary reagent is used in trace amounts, excessive amounts of residual acid in the diol compound can affect the catalytic effect of the auxiliary reagent.

[0003] Taiwan Patent Publication No. TW I290537B discloses that an alkali metal hydroxide (e.g., NaOH) may be added to the reaction mixture for synthesizing polycarbonate (PC) to increase the activity of the polyhydrogen-polyborate catalyst. The amount of alkali metal hydroxide used is equivalent to about 10% of the dihydroxy aromatic compound used. -7 to 10 -5 If the above amount is converted into mg KOH / g (acid value analysis unit), it is approximately between 2.4×10 -6 to 2.4×10 -4 mg KOH / g.

[0004] However, residual acids in diol compounds (dihydroxyaromatic compounds), such as bisphenol A (BPA), may affect the reactivity of alkali metal hydroxides. Prior to the transesterification reaction, the residual acid in the diol compound must be adjusted to a concentration comparable to that of the alkali metal hydroxide to prevent the residual acid from affecting the reactivity of the alkali metal hydroxide (e.g., enhancing its catalytic effect).

[0005] The current standard test method for acid-base titration is ASTM D664, which specifies a minimum residual acid value of 0.05 to <0.1 mgKOH / g. Residual acid concentrations below 0.05 mgKOH / g are not measurable due to the detection limit. Therefore, it is impossible to accurately measure the residual acid in the aforementioned diol compounds, and therefore it is impossible to assess whether the residual acid in the diol compounds has been regulated to the same level as the alkali metal hydroxide dosage. In short, if the acid value in alcohol chemicals is less than 0.01 mgKOH / g, and the detection accuracy must reach 0.0001 mgKOH / g, it is difficult to achieve this. Furthermore, residual acid in alcohol chemicals can affect the reactivity of catalysts in subsequent chemical reactions, making accurate acid value measurement necessary.

[0006] Therefore, the inventors felt that the above-mentioned defects could be improved, and therefore devoted themselves to research and applied scientific principles, and finally proposed a reasonable design and effective improvement of the above-mentioned defects of the present invention. Summary of the Invention

[0007] The embodiment of the present invention provides a residual acid analysis method for alcohol compounds, which is used to effectively improve the defects that may occur in the existing technology.

[0008] An embodiment of the present invention discloses a method for analyzing residual acid in alcohol compounds, comprising: performing an organic solvent preparation operation, which includes: providing an organic solvent and placing the organic solvent in a distiller to distill the organic solvent; wherein the organic solvent preparation operation excludes at least the first 10% of the distilled liquid distilled from the distiller; and collecting the middle section of the distilled liquid distilled from the distiller to obtain a purified organic solvent; performing a titration liquid preparation operation, which includes: mixing an alkaline inorganic compound with at least a portion of the purified organic solvent to generate a titration liquid; performing a sample preparation operation, which includes: mixing a diol compound to be tested with at least another portion of the purified organic solvent to generate a sample to be tested; and performing a titration operation, which includes: performing an acid-base titration on the sample to be tested using the titration liquid to analyze the residual acid content of the diol compound.

[0009] Preferably, the normality of the basic inorganic compound in the titration liquid is not greater than 0.005N.

[0010] Preferably, the organic solvent is ethanol, the alkaline inorganic compound is potassium hydroxide, and the diol compound is a dihydroxy aromatic compound.

[0011] Preferably, the organic solvent preparation operation does not collect 10% to 15% of the distilled liquid in the front section distilled from the distiller; then collects 10% to 15% to 90 to 95% of the distilled liquid in the middle section distilled from the distiller; and does not collect 5% to 10% of the distilled liquid in the back section distilled from the distiller.

[0012] Preferably, the distilled liquid in the front section of the distiller contains low-boiling-point aldehyde compounds, and the distilled liquid in the back section of the distiller contains high-boiling-point acid compounds.

[0013] Preferably, before the distiller distills the organic solvent, the organic solvent preparation operation includes: purging the organic solvent with nitrogen gas for 10 to 30 minutes; and then, the distiller distills the organic solvent in an atmosphere filled with the nitrogen gas.

[0014] Preferably, the normality of the basic inorganic compound in the titration liquid is between 0.005N and 0.0001N.

[0015] Preferably, the normality of the basic inorganic compound in the titration liquid is between 0.005N and 0.0005N.

[0016] Preferably, the weight ratio of the diol compound to the organic solvent in the sample to be tested is between 1:1 and 1:4.

[0017] Preferably, the sample preparation operation further includes purifying the sample with nitrogen gas before analyzing the prepared sample.

[0018] Preferably, the titration operation is performed by potentiometric titration to perform acid-base titration.

[0019] In summary, the residual acid analysis method of alcohol compounds disclosed in the embodiments of the present invention can achieve a sufficiently low concentration level for the detection accuracy of the residual acid analysis of alcohol compounds, thereby improving the detection limit, through the technical solutions of "implementing an organic solvent preparation operation, which includes: providing an organic solvent, and placing the organic solvent in a distiller to distill the organic solvent; wherein the organic solvent preparation operation excludes at least the first 10% of the distilled liquid distilled from the distiller; and collecting the middle section of the distilled liquid distilled from the distiller to obtain a purified organic solvent" and "implementing a titration liquid preparation operation, which includes: mixing an alkaline inorganic compound with at least a portion of the purified organic solvent to generate a titration liquid" and "implementing a sample preparation operation, which includes: mixing a diol compound to be tested with at least another portion of the purified organic solvent to generate a sample to be tested" and "implementing a titration operation, which includes: performing acid-base titration on the sample to be tested using the titration liquid to analyze the residual acid of the diol compound".

[0020] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description and drawings of the present invention. However, such description and drawings are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the residual acid analysis method of alcohol compounds according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] The following is an explanation of the disclosed embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted in actual size. It is stated in advance. The following embodiments will further explain the relevant technical content of the present invention in detail, but the disclosed content is not intended to limit the scope of protection of the present invention.

[0023] It should be understood that although terms such as "first," "second," and "third" may be used herein to describe various materials or parameters, these materials or parameters should not be limited by these terms. These terms are primarily used to distinguish one material from another, or one parameter from another.

[0024] In addition, the term "or" used herein may include any one or more combinations of the associated listed items as appropriate.

[0025] In the prior art, alkali metal hydroxides (such as potassium hydroxide or sodium hydroxide) are often used as catalysts in transesterification reactions to synthesize polycarbonates. However, excessive residual acid in diol compounds (such as bisphenol A) can affect the catalytic effect, and the residual acid needs to be regulated to a concentration equivalent to the catalyst dosage. The current standard test method for acid-base titration (ASTM D664) cannot accurately detect residual acid concentrations below 0.05 mgKOH / g, making it impossible to effectively assess whether the residual acid content of the diol compound has been regulated to the appropriate concentration, which may affect the efficiency of the transesterification reaction and product quality.

[0026] [Analysis method for residual acid of alcohol compounds]

[0027] In order to solve the technical problems existing in the above-mentioned prior art, an embodiment of the present invention provides a residual acid analysis method for alcohol compounds, and the detection accuracy of the residual acid analysis can reach a concentration level of 0.0001 mg KOH / g.

[0028] See also Figure 1 As shown, the residual acid analysis method of alcohol compounds includes step S110, step S120, and step S130. It should be noted that the order of the steps and the actual operation method described in the embodiment of the present invention can be adjusted according to needs and are not limited to the embodiment described.

[0029] The step S110 is to prepare an organic solvent, which includes providing an organic solvent and placing the organic solvent in a distiller to distill the organic solvent.

[0030] The organic solvent preparation process does not collect the front portion (e.g., at least the first 10%, preferably the first 10% to 15%) of the distilled liquid from the distiller, thereby discarding the front portion of the distilled liquid. The middle portion (e.g., from the middle 10% to 15% to 90% to 95%) of the distilled liquid from the distiller is then collected to obtain a purified organic solvent from the middle portion, which is then used for later use. Furthermore, the organic solvent preparation process does not collect the rear portion (e.g., the rear 5% to 10%) of the distilled liquid from the distiller, thereby discarding the rear portion of the distilled liquid.

[0031] In one embodiment of the present invention, taking 5.0 kg of organic solvent as an example, the organic solvent preparation operation does not collect the first 15% of the distilled liquid distilled from the distiller (that is, the first 0.75 kg of distilled liquid is excluded); then, 15% to 95% of the distilled liquid in the middle section of the distilled liquid is collected (that is, the middle 4 kg of distilled liquid is collected as purified fresh organic solvent); and finally, the last 5% of the distilled liquid distilled from the distiller is not collected (that is, the last 0.25 kg of distilled liquid is excluded).

[0032] Furthermore, before the distiller distills the organic solvent, the organic solvent preparation process includes purging the organic solvent with nitrogen gas for a predetermined time of 10 to 30 minutes to remove trace impurities in the organic solvent and reduce the impact of trace impurities on subsequent residual acid analysis. The distiller then distills the organic solvent in an atmosphere filled with nitrogen gas. The distillation temperature of the organic solvent in the distiller is between 75°C and 80°C, and the gas pressure is atmospheric pressure.

[0033] The organic solvent preparation operation may be, for example, performed by inserting a nitrogen gas pipeline below the liquid surface of the organic solvent, so that the nitrogen gas purifies the organic solvent.

[0034] In one embodiment of the present invention, the organic solvent may be, for example, a monohydric alcohol organic solvent. For example, the organic solvent is ethanol (or anhydrous alcohol).

[0035] It is worth mentioning that during the organic solvent preparation process, the distilled liquid in the front section (such as the first 10% to 15% of the distilled liquid) distilled from the distiller contains low-boiling-point compounds (such as trace amounts of aldehyde compounds). The distilled liquid in the back section (such as the last 5% to 10% of the distilled liquid) distilled from the distiller contains high-boiling-point compounds (such as trace amounts of acid compounds). In other words, the purified organic solvent in the middle section collected during the organic solvent preparation process eliminates the trace amounts of aldehyde compounds in the distilled liquid in the front section and the trace amounts of acid compounds in the distilled liquid in the back section, thereby avoiding the influence of aldehyde compounds and acid compounds on the subsequent residual acid analysis. Furthermore, the purified organic solvent in the middle section collected during the organic solvent preparation process will be further used in subsequent operations.

[0036] The step S120 is to prepare a titration liquid, which includes mixing the alkaline inorganic compound with (at least a portion of) the purified organic solvent prepared in the step S110 to generate a titration liquid.

[0037] In one embodiment of the present invention, the basic inorganic compound is potassium hydroxide (e.g., reagent grade or analytical grade potassium hydroxide). The normality of the basic inorganic compound in the titration liquid is no more than 0.005N, preferably between 0.005N and 0.0001N, and particularly preferably between 0.005N and 0.0005N. For example, the normality of the basic inorganic compound in the titration liquid is 0.00075N, 0.001N, 0.002N, 0.003N, 0.004N, or 0.005N.

[0038] The titration liquid prepared in step S120, being within the aforementioned normality range, can help improve the detection limit of the acid value analysis during subsequent titration operations, for example, helping the detection accuracy of the residual acid analysis to reach a concentration level of 0.0001 mgKOH / g. Conversely, if the normality of the alkaline inorganic compound in the titration liquid exceeds 0.005N, the detection accuracy of the residual acid analysis will not reach a concentration level of 0.0001 mgKOH / g.

[0039] In one embodiment of the present invention, the titration liquid preparation operation further includes disposing a 0.05-2N hydrochloric acid standard solution (preferably a 0.1N hydrochloric acid standard solution purchased from Sigma-Aldrich) in an ethanol solution to confirm the equivalent concentration.

[0040] Step S130 is to prepare a sample to be tested, which includes mixing the diol compound to be tested with (at least another portion of) the purified organic solvent from step S110 to generate a liquid sample to be tested. The diol compound to be tested has an unknown amount of residual acid.

[0041] Furthermore, the weight ratio of the diol compound to the organic solvent is between 1:1 and 1:4, and preferably between 1:1 and 1:2.

[0042] For example, the sample preparation operation is to mix one kilogram of a diol compound with two kilograms of a purified organic solvent to generate the sample, but the present invention is not limited thereto.

[0043] The diol compound is further defined as a dihydroxy aromatic compound, and may be, for example, bisphenol A (BPA).

[0044] In one embodiment of the present invention, the sample preparation step involves mixing a diol compound and a purified organic solvent in a container (e.g., a three-necked flask) under a nitrogen atmosphere. The order of adding the materials may be to first add the diol compound, followed by the purified organic solvent under a nitrogen atmosphere, thereby generating the sample to be tested. The liquid temperature during mixing is maintained at 20-25°C, but the present invention is not limited thereto.

[0045] In one embodiment of the present invention, the sample preparation operation further includes purging the prepared sample with another nitrogen gas for a predetermined time of 10 minutes to 30 minutes before the subsequent acid value analysis to remove impurities that may be present in the diol compound, thereby reducing the impact of the impurities on the subsequent residual acid analysis.

[0046] Furthermore, the sample preparation operation may be, for example, inserting a nitrogen gas pipeline below the liquid level of the sample to be tested so that the nitrogen gas purifies the sample to be tested.

[0047] It is worth mentioning that the purified organic solvent in the above step S110 is preferably used within 24 hours (that is, configured as a titration liquid with the alkaline inorganic compound in step S120, and / or configured as a test sample with the diol compound in step S130) to avoid the organic solvent reacting with carbon dioxide in the air to generate other impurities, thereby affecting the accuracy of the detection.

[0048] Step S140 involves performing a titration operation, which includes performing an acid-base titration on the sample to be tested in step S130 using the titration liquid in step S120. After reaching the titration endpoint, the acid value of the diol compound, i.e., the residual acid content of the diol compound, is calculated. It is worth noting that the titration operation can be performed, for example, using potentiometric titration.

[0049] According to the above technical solution, the residual acid analysis method of alcohol compounds provided by the embodiment of the present invention can achieve a detection accuracy of residual acid analysis at a concentration level of 0.0001 mg KOH / g.

[0050] For example, the residual acid analysis method for alcohol compounds provided by the embodiments of the present invention can accurately quantify the residual acid content of diol compounds (e.g., BPA), thereby providing acid value information with an accuracy of 0.0001 mg KOH / g when the diol compounds are shipped to downstream production units or customers.

[0051] [Experimental data and test results]

[0052] In order to demonstrate the technical effect of the residual acid analysis method of the embodiment of the present invention, the following will be described with experimental data and experimental results. However, the protection scope of the present invention is not limited thereto.

[0053] <Experimental Example 1>

[0054] Solvent Purification: Place 5 kg of anhydrous alcohol (i.e., ethanol) in a distiller and distill under a nitrogen atmosphere. Do not collect the first 15% (0.75 kg) of the distilled liquid, and collect the remaining 15-95% (4 kg) of the distilled liquid as purified anhydrous alcohol. The remaining 5% (0.25 kg) of the distilled liquid is also not collected. Titration Liquid Preparation: Potassium hydroxide (KOH) and the purified anhydrous alcohol are mixed to create a titration liquid with a KOH concentration of 0.005 N. The concentration of this titration liquid is verified with 0.1 N HCl (Sigma-Aldrich hydrochloric acid standard solution in ethanol). Sample Preparation: Measure one kilogram of a BPA sample with an unknown residual acid content into a three-necked flask. Add two kilograms of purified anhydrous alcohol under a nitrogen atmosphere. After stirring, insert a nitrogen tube below the liquid surface to purge for 15 minutes to generate the sample to be tested. The liquid temperature is maintained at 20°C to 25°C. Acid value analysis: 150g of BPA sample was titrated potentiometrically with the titration liquid using a KEM (Kyoto Electron Industries) potentiometric automatic titrator. The acid value unit is 10E. -3 mgKOH / g. The acid value is calculated as follows.

[0055] Acid value = (KOH consumption (cc) × f × 56.1) / weight of the sample to be tested. KOH consumption (cc) is the number of cc of KOH used for titration after adding the sample, which represents the volume (in cubic centimeters or milliliters) of alkaline solution (potassium hydroxide, KOH) consumed during the titration. f is the specified equivalence factor for KOH. 56.1 is the molar mass of milligrams of potassium hydroxide (KOH), which is used to convert the amount of KOH consumed from volume to mass, thereby calculating the number of milligrams of KOH required to neutralize the free fatty acids in the sample. Weight of the sample to be tested (g): This is the mass of the sample to be tested (in grams). The acid value is determined by calculating the mass of potassium hydroxide required under specific conditions (after adjusting for the equivalence factor) to neutralize all free fatty acids in the sample. Finally, the acid value is expressed in milligrams of KOH / g of sample, a quantitative indicator that directly reflects the free fatty acid content in oils and fats or other substances.

[0056] The preparation methods of <Experimental Example 2> to <Experimental Example 8> are substantially the same as those of Experimental Example 1, except for the concentration of the titration liquid KOH and the titration amount of the sample to be tested, as shown in Table 1 below.

[0057] [Table 1]

[0058]

[0059] From the above experimental data, it can be seen that the acid value analyzed by the titration liquid with a KOH concentration of 0.001N to 0.005N in Experimental Examples 1 to 4 is approximately 13.1205 to 15.6923*10E -3 mgKOH / g, which shows that the acid value measurement results can be detected stably and at low enough concentration levels.

[0060] Experiments 2-4 used a 0.001N titrant and analyzed different grams of BPA sample (50-100g), yielding roughly the same results. Experiment 5, using a 0.0001N titrant, yielded a slightly higher acid value, but still within the acceptable analytical range.

[0061] From the above experimental data, it can be seen that the distilled and purified anhydrous alcohol is used for the preparation of the titration liquid and the sample to be tested, and the acid value information of the BPA sample to be tested can be analyzed by using a titration liquid with a KOH concentration of 0.0001N to 0.005N.

[0062] In addition, in Experiments 6 to 8, the titration liquid used a 0.01N titrant. However, due to the high KOH concentration in the titrant, the titration endpoint could not be determined. In other words, if a KOH concentration greater than 0.005N were used, the acid value information would not be analyzed.

[0063] In addition, it is worth mentioning that in the comparative example, an undistilled (unpurified) solvent was used, and the remaining preparation conditions (titration liquid configuration and test sample configuration) were the same as those in the above-mentioned Experimental Example 1. The test results of the comparative example showed that the titration endpoint could not be determined, and therefore the acid value information could not be analyzed.

[0064] [Beneficial Effects of Embodiments]

[0065] The beneficial effect of the present invention is that the residual acid analysis method of alcohol compounds provided in the embodiment of the present invention can achieve a sufficiently low concentration level for the detection accuracy of the residual acid analysis of alcohol compounds, thereby improving the detection limit, through the technical scheme of "implementing an organic solvent preparation operation, which includes: providing an organic solvent, and placing the organic solvent in a distiller to distill the organic solvent; wherein the organic solvent preparation operation excludes at least the first 10% of the distilled liquid distilled from the distiller; and collecting the middle section of the distilled liquid distilled from the distiller to obtain a purified organic solvent" and "implementing a titration liquid preparation operation, which includes: mixing an alkaline inorganic compound with at least a portion of the purified organic solvent to generate a titration liquid" and "implementing a sample preparation operation, which includes: mixing a diol compound to be tested with at least another portion of the purified organic solvent to generate a sample to be tested" and "implementing a titration operation, which includes: performing acid-base titration on the sample to be tested using the titration liquid to analyze the residual acid of the diol compound".

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention should fall within the scope of protection of the claims of the present invention.

Claims

1. A method for analyzing residual acid of alcohol compounds, characterized in that: The residual acid analysis method of the alcohol compound comprises: Performing an organic solvent preparation process, which includes: providing an organic solvent and placing the organic solvent in a distiller to distill the organic solvent; wherein the organic solvent preparation process removes at least the first 10% of the distilled liquid distilled from the distiller; and collecting the middle portion of the distilled liquid distilled from the distiller to obtain a purified organic solvent; Performing a titration liquid preparation operation, which includes: mixing a basic inorganic compound with at least a portion of the purified organic solvent to generate a titration liquid; wherein the normality concentration of the basic inorganic compound in the titration liquid is not greater than 0.005N; Performing a sample preparation operation includes: mixing the diol compound to be tested with at least another portion of the purified organic solvent to generate a sample to be tested; and The titration operation is performed, including: performing acid-base titration on the sample to be tested using the titration liquid to analyze the acid residue of the diol compound.

2. The residual acid analysis method of alcohol compounds according to claim 1, wherein The organic solvent is ethanol, the alkaline inorganic compound is potassium hydroxide, and the diol compound is a dihydroxy aromatic compound.

3. The residual acid analysis method of alcohol compounds according to claim 1, wherein The organic solvent preparation operation does not collect the first 10% to 15% of the distilled liquid distilled from the distiller; then collects the middle 10% to 15% to 90% to 95% of the distilled liquid distilled from the distiller to obtain the purified organic solvent; and does not collect the last 5% to 10% of the distilled liquid distilled from the distiller.

4. The residual acid analysis method of alcohol compounds according to claim 3, wherein The distilled liquid at the front section of the distiller contains low-boiling-point aldehyde compounds, and the distilled liquid at the rear section of the distiller contains high-boiling-point acid compounds.

5. The residual acid analysis method of alcohol compounds according to claim 1, wherein Before the distiller distills the organic solvent, the organic solvent preparation operation includes: purifying the organic solvent with nitrogen gas for 10 minutes to 30 minutes; and then, the distiller distills the organic solvent in an atmosphere filled with the nitrogen gas.

6. The method for analyzing residual acid of alcohol compounds according to claim 1, wherein The normality of the basic inorganic compound in the titration liquid is between 0.005N and 0.0001N.

7. The residual acid analysis method of alcohol compounds according to claim 6, characterized in that: The normality of the basic inorganic compound in the titration liquid is between 0.005N and 0.0005N.

8. The method for analyzing residual acid of alcohol compounds according to claim 1, wherein The weight ratio between the diol compound and the organic solvent in the sample to be tested is between 1:1 and 1:

4.

9. The method for analyzing residual acid of alcohol compounds according to claim 1, wherein The sample preparation operation further includes purifying the sample with nitrogen gas before analyzing the sample.

10. The method for analyzing residual acid of alcohol compounds according to claim 1, wherein: The titration operation is performed by using a potentiometric titration method.

Images