CN114264740B - Method for measuring effective components in circulating catalyst for synthesizing methacrolein - Google Patents
Method for measuring effective components in circulating catalyst for synthesizing methacrolein Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 122
- 238000000034 method Methods 0.000 title claims abstract description 59
- STNJBCKSHOAVAJ-UHFFFAOYSA-N Methacrolein Chemical compound CC(=C)C=O STNJBCKSHOAVAJ-UHFFFAOYSA-N 0.000 title claims abstract description 47
- 230000002194 synthesizing effect Effects 0.000 title claims abstract description 25
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 64
- 239000006227 byproduct Substances 0.000 claims abstract description 51
- GNVRJGIVDSQCOP-UHFFFAOYSA-N n-ethyl-n-methylethanamine Chemical compound CCN(C)CC GNVRJGIVDSQCOP-UHFFFAOYSA-N 0.000 claims abstract description 39
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 32
- HPNMFZURTQLUMO-UHFFFAOYSA-N diethylamine Chemical compound CCNCC HPNMFZURTQLUMO-UHFFFAOYSA-N 0.000 claims abstract description 31
- 230000008569 process Effects 0.000 claims abstract description 26
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000004480 active ingredient Substances 0.000 claims abstract description 17
- 238000004817 gas chromatography Methods 0.000 claims abstract description 17
- 238000011084 recovery Methods 0.000 claims abstract description 15
- 238000004458 analytical method Methods 0.000 claims abstract description 14
- 239000000126 substance Substances 0.000 claims abstract description 10
- 239000002608 ionic liquid Substances 0.000 claims abstract description 9
- UEHUZQKLOWYOMO-UHFFFAOYSA-N diethylazanium;acetate Chemical group CC(O)=O.CCNCC UEHUZQKLOWYOMO-UHFFFAOYSA-N 0.000 claims abstract description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 24
- 238000004451 qualitative analysis Methods 0.000 claims description 17
- 238000004587 chromatography analysis Methods 0.000 claims description 15
- 239000007789 gas Substances 0.000 claims description 14
- 239000012088 reference solution Substances 0.000 claims description 8
- 239000012085 test solution Substances 0.000 claims description 8
- 238000005303 weighing Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 6
- 238000002347 injection Methods 0.000 claims description 6
- 239000007924 injection Substances 0.000 claims description 6
- 238000007036 catalytic synthesis reaction Methods 0.000 claims description 5
- 238000005481 NMR spectroscopy Methods 0.000 claims description 4
- 238000012937 correction Methods 0.000 claims description 4
- 238000004949 mass spectrometry Methods 0.000 claims description 4
- 239000013558 reference substance Substances 0.000 claims description 4
- 230000004044 response Effects 0.000 claims description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- 239000012159 carrier gas Substances 0.000 claims description 3
- 125000004122 cyclic group Chemical group 0.000 claims description 3
- 239000001307 helium Substances 0.000 claims description 3
- 229910052734 helium Inorganic materials 0.000 claims description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 3
- 239000001257 hydrogen Substances 0.000 claims description 3
- 229910052739 hydrogen Inorganic materials 0.000 claims description 3
- 238000007086 side reaction Methods 0.000 claims description 3
- 238000004064 recycling Methods 0.000 abstract description 9
- 230000015572 biosynthetic process Effects 0.000 abstract description 8
- 238000003786 synthesis reaction Methods 0.000 abstract description 8
- 238000001514 detection method Methods 0.000 abstract description 6
- 239000000243 solution Substances 0.000 description 22
- ROSDSFDQCJNGOL-UHFFFAOYSA-N Dimethylamine Chemical compound CNC ROSDSFDQCJNGOL-UHFFFAOYSA-N 0.000 description 19
- 238000002835 absorbance Methods 0.000 description 19
- 239000012295 chemical reaction liquid Substances 0.000 description 17
- 238000006243 chemical reaction Methods 0.000 description 16
- 238000006555 catalytic reaction Methods 0.000 description 12
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 230000003197 catalytic effect Effects 0.000 description 8
- 238000005259 measurement Methods 0.000 description 6
- 239000012086 standard solution Substances 0.000 description 5
- NBBJYMSMWIIQGU-UHFFFAOYSA-N Propionic aldehyde Chemical compound CCC=O NBBJYMSMWIIQGU-UHFFFAOYSA-N 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 230000008901 benefit Effects 0.000 description 3
- 239000012153 distilled water Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000001819 mass spectrum Methods 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- FUSUHKVFWTUUBE-UHFFFAOYSA-N buten-2-one Chemical compound CC(=O)C=C FUSUHKVFWTUUBE-UHFFFAOYSA-N 0.000 description 2
- ZTQSAGDEMFDKMZ-UHFFFAOYSA-N butyric aldehyde Natural products CCCC=O ZTQSAGDEMFDKMZ-UHFFFAOYSA-N 0.000 description 2
- 238000011088 calibration curve Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000007069 methylation reaction Methods 0.000 description 2
- -1 nitrogen-containing compound Chemical class 0.000 description 2
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 2
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000001052 transient effect Effects 0.000 description 2
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 description 1
- 125000004177 diethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 125000002147 dimethylamino group Chemical group [H]C([H])([H])N(*)C([H])([H])[H] 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 238000000655 nuclear magnetic resonance spectrum Methods 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 239000004323 potassium nitrate Substances 0.000 description 1
- 235000010333 potassium nitrate Nutrition 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000002798 spectrophotometry method Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/584—Recycling of catalysts
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- Investigating Or Analyzing Non-Biological Materials By The Use Of Chemical Means (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a method for measuring active ingredients in a circulating catalyst for synthesizing methacrolein, belongs to the technical field of chemical substance detection methods, and can solve the technical problem that the actual active ingredient content in the catalyst cannot be accurately measured due to the undefined type of byproducts in the existing methacrolein synthesis process, so that the catalyst recycling is difficult to realize. The technical scheme comprises the following steps: the circulating catalyst is a diethylamine-acetic acid ionic liquid catalyst, the active ingredients of the catalyst are diethylamine and acetic acid, and the measuring method comprises the following steps: determination of the content of byproducts: determining the content of the byproduct diethyl methylamine by gas chromatography; determination of the active ingredient in the circulating catalyst: and calculating the loss amount of the circulating catalyst in the recovery process by adopting a total nitrogen analysis method, and determining the loss amount of the diethylamine in the circulating catalyst in the recovery process by combining the content of the byproduct diethylamine, thereby obtaining the actual effective content of the diethylamine in the circulating catalyst.
Description
Technical Field
The invention belongs to the technical field of chemical substance detection methods, and particularly relates to a method for measuring active ingredients in a circulating catalyst for synthesizing methacrolein.
Background
Methacrolein (MAL for short) is an organic compound, which is mainly used for the production of copolymers and resins, and is a raw material for the production of methacrylic acid and a raw material for thermoplastic monomers.
At present, in the synthesis process of methacrolein, organic acid and aliphatic amine are usually adopted as catalysts (for example, acetic acid and diethylamine are adopted as catalysts for catalytic reaction), but the diethylamine-acetic acid ionic liquid catalyst has the problem that recycling is difficult to realize in the process of catalyzing the synthesis of methacrolein, because the diethylamine-acetic acid ionic liquid catalyst exists in a reaction liquid in the form of ionic liquid after the main catalytic component diethylamine and acetic acid react in the process of catalyzing the synthesis of methacrolein, side reactions occur in the reaction process, but the material structure and the reaction mechanism of byproducts are not clear, so that the content of the effective catalytic component diethylamine cannot be accurately quantified in the process of recycling the catalyst, thereby the conversion rate of propionaldehyde and the selectivity of methacrolein are difficult to control in the process of circularly catalyzing the synthesis of methacrolein,
Therefore, on the basis of qualitative and quantitative analysis of byproducts, the content of actual effective components in the catalyst is further defined, and is the key for realizing the recycling of the catalyst.
Disclosure of Invention
Aiming at the technical problems that the actual content of the effective components in the catalyst cannot be accurately measured due to the undefined type of the byproducts in the existing methacrolein synthesis process, and the catalyst recycling is difficult to realize, the invention provides the method for measuring the effective components in the circulating catalyst for synthesizing the methacrolein, which is simple and convenient to operate and high in accuracy, and the method can realize the recycling of the catalyst and achieve the aim of saving the production cost.
In order to achieve the above purpose, the invention adopts the following technical scheme:
The method for measuring the effective components in the circulating catalyst for synthesizing the methacrolein, wherein the circulating catalyst is a diethylamine-acetic acid ionic liquid catalyst, and the effective components are diethylamine and acetic acid, and the method for measuring the effective components comprises the following steps:
Determination of the content of byproducts: determining the content of the byproduct diethyl methylamine by gas chromatography;
determination of the active ingredient in the circulating catalyst: and calculating the loss amount of the circulating catalyst in the recovery process by adopting a total nitrogen analysis method, and determining the loss amount of the diethylamine in the circulating catalyst in the recovery process by combining the content of the diethylamine, thereby obtaining the actual effective content of the diethylamine as an effective component in the circulating catalyst.
Preferably, the method further comprises a byproduct qualitative analysis step before the byproduct content determination step.
Preferably, the qualitative analysis of the by-product dimethylamine in the circulating catalyst is performed by a method combining gas chromatography, nuclear magnetic resonance and mass spectrometry.
Preferably, in the by-product qualitative analysis and by-product content determination steps, the gas chromatography includes:
Taking absolute ethyl alcohol as an internal standard substance and an N, N-diethyl methylamine standard sample as a reference substance, weighing a certain amount of absolute ethyl alcohol and the N, N-diethyl methylamine standard sample to prepare a reference solution, performing chromatographic analysis to obtain a chromatogram of the reference solution, and calculating a correction factor f according to the following formula:
（I）
In the above formula (I), A s and A r are the peak areas or peak heights of the anhydrous ethanol and N, N-diethylmethylamine standard samples, respectively, and m s and m r are the amounts of the anhydrous ethanol and N, N-diethylmethylamine standard samples added, respectively;
taking absolute ethyl alcohol as an internal standard, taking the circulating catalyst as a sample to be detected, weighing a certain amount of absolute ethyl alcohol and the circulating catalyst to prepare a test solution, carrying out chromatographic analysis to obtain a chromatogram of the test solution, and calculating the content m i according to the chromatographic peak response value of the component of the sample to be detected containing the internal standard, wherein the formula is as follows:
（II）
A i and A s are the peak areas or peak heights of the sample to be measured and the internal standard, respectively, and ms is the amount of the internal standard added.
Preferably, in the by-product qualitative analysis and by-product content determination steps, the chromatographic conditions of the gas chromatography are:
Chromatographic column: KB-624;
column temperature: the initial temperature is 70 ℃, and the temperature is kept for 12min; heating at 70-240 deg.c and 40 deg.c/min for 20min;
Sample injection amount: 0.1-0.3 μl;
carrier gas: helium gas;
Split ratio: 20:1;
a detector: a hydrogen flame ionization detector; detector temperature: 300 ℃; sample injector: a split-flow sample injection device; injector temperature: 300 ℃.
Preferably, the sample amount is 0.1. Mu.l.
Compared with the prior art, the invention has the advantages and positive effects that:
1. According to the method for determining the effective components in the circulating catalyst for synthesizing the methacrolein, provided by the invention, qualitative analysis of a byproduct diethyl methylamine in the process of catalyzing and synthesizing the methacrolein is realized by a mode of combining gas chromatography, nuclear magnetic resonance and mass spectrum, and on the basis, the content of the effective catalytic active diethylamine in the circulating catalyst in the process of synthesizing the methacrolein is indirectly determined by determining the content of the byproduct diethyl methylamine, so that the technical problem that the content of the effective components diethylamine in the diethylamine-acetic acid ionic liquid cannot be determined is solved;
2. The method for measuring the effective components in the circulating catalyst for synthesizing the methacrolein effectively solves the problems that the catalyst is difficult to realize circulating recycling, so that the cost is too high and the economic benefit is not ideal in industrial production, and simultaneously, the problems that the conversion rate of propionaldehyde and the selectivity of the methacrolein are difficult to control stably when the effective components in the catalyst are not quantitatively analyzed are avoided;
3. The method for measuring the effective components in the circulating catalyst for synthesizing the methacrolein has the characteristics of simplicity and convenience in operation, high accuracy and the like.
Drawings
FIG. 1 is a liquid-gas chromatogram of a methacrolein reaction after first catalysis by a catalyst according to an embodiment of the present invention;
FIG. 2 is a liquid-gas chromatogram of a methacrolein reaction after a second catalysis by a catalyst according to an embodiment of the present invention;
FIG. 3 is a liquid-gas chromatogram of methacrolein reaction after third catalysis by the catalyst according to the embodiment of the invention;
FIG. 4 is a liquid-gas chromatogram of methacrolein reaction after the fourth catalysis of the catalyst provided by the embodiment of the invention;
FIG. 5 is a gas chromatogram of a liquid-oil phase of methacrolein reaction after third catalysis by the catalyst provided in the embodiment of the present invention;
FIG. 6 is a gas chromatogram of the third catalytic stage of the catalyst provided by the present invention after the addition of the diethylmethylamine standard to the methacrolein reaction liquid/oil phase;
FIG. 7 is a diagram of a standard quality spectrum of diethylmethylamine according to an embodiment of the invention;
FIG. 8 is a diagram showing the mass spectrum of diethylmethylamine in the homogeneous phase reaction solution according to the embodiment of the invention;
Fig. 9 is a gas chromatogram of a homogeneous phase reaction solution according to an embodiment of the present invention.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the invention provides a method for measuring active ingredients in a circulating catalyst for synthesizing methacrolein, wherein the circulating catalyst is a diethylamine-acetic acid ionic liquid catalyst, and the active ingredients are diethylamine and acetic acid, and the method comprises the following steps:
S1, measuring the content of byproducts: determining the content of the byproduct diethyl methylamine by gas chromatography;
S2, measuring active ingredients in the circulating catalyst: and calculating the loss amount of the circulating catalyst in the recovery process by adopting a total nitrogen analysis method, and determining the loss amount of the diethylamine in the circulating catalyst in the recovery process by combining the content of the diethylamine, so as to obtain the actual effective content of the diethylamine in the circulating catalyst.
In the above embodiment, a method for determining an active ingredient in a circulating catalyst for synthesizing methacrolein is provided, and qualitative analysis of a byproduct diethyl methylamine in the process of synthesizing methacrolein is realized by combining gas chromatography, nuclear magnetic resonance and mass spectrometry, and on the basis, the content of the active ingredient diethyl amine in the circulating catalyst in the process of synthesizing methacrolein is indirectly determined by determining the content of the byproduct diethyl methylamine, so that the technical problem that the content of the active ingredient diethyl amine in a diethyl amine-acetic acid ionic liquid cannot be determined is solved.
Furthermore, the invention has clear that in the process of circularly catalyzing and synthesizing the methacrolein (MAL for short), the loss of the active ingredient diethylamine in the catalyst is also existed in the recycling of the catalyst besides the methylation reaction of the active ingredient diethylamine in the catalyst to generate the diethylamine, and specifically:
(1) The method utilizes a total nitrogen analysis method (according to the specification of HJ 636-2012, hereinafter referred to as total nitrogen analysis method) to respectively determine the total nitrogen content in the catalyst solution when the catalyst amine content is 6.8 percent, and then carries out catalytic synthesis on methacrolein MAL;
(2) Collecting water phase in MAL reaction liquid for catalyst concentration recovery, removing excessive water in the reaction liquid by adopting a reduced pressure distillation method in the process, respectively analyzing and measuring total nitrogen content of the recovered catalyst and nitrogen content in the concentrated water phase by a total nitrogen analysis method after the mass of the concentrated catalyst is consistent with that of the fresh catalyst so as to determine whether loss exists in the process of circularly catalyzing and synthesizing MAL by the catalyst;
Based on the above experiments, the following conclusions were drawn:
According to the invention, the total nitrogen content in the recovered catalyst solution is obviously reduced compared with the total nitrogen content in the new catalyst in the catalyst recovery process through a total nitrogen analysis method, wherein the total nitrogen content in the new catalyst (6.8% concentration) is about 9500mg/L, and the total nitrogen content in the recovered catalyst solution after the first catalytic synthesis of MAL is 7000-800 mg/L; in experiments, the nitrogen loss in the recovered catalyst solution is related to the concentration and recovery conditions of the catalyst, the catalyst is heated at a higher temperature when the catalyst is recovered by normal pressure concentration, the nitrogen loss of the catalyst is also maximum, the total nitrogen content in the recovered catalyst solution is 7000-7500 mg/L, and the nitrogen content in the distilled water phase in the concentration process is 2000-2500 mg/L;
However, with the increase of the vacuum degree and the decrease of the heating temperature of the catalyst during the concentration and recovery of the catalyst, the nitrogen loss of the catalyst and the nitrogen loss of the recovered catalyst under normal pressure are reduced, at this time, the total nitrogen content in the recovered catalyst solution is 8000-8500 mg/L, and the nitrogen content in the distilled water phase in the concentration process is 1000-1500 mg/L.
The invention makes clear that the catalyst has the advantages that in the process of synthesizing MAL by circulating catalysis, the byproduct diethyl methylamine generated after the methylation reaction of diethylamine in each circulating catalysis process of the catalyst accounts for the proportion of the nitrogen-containing compound in the whole catalyst solution, and the contents of the effective catalytic component diethyl amine and the byproduct diethyl methylamine in the circulating recycled catalyst solution can be accurately calculated according to the total nitrogen in the circulating catalyst solution and the total nitrogen loss in the circulating recovery process of the catalyst, so that the catalytic stability in the process of synthesizing MAL in industrial production is stably controlled.
In a preferred embodiment, a qualitative analysis step of the by-product is further included before the by-product content determination step.
In a preferred embodiment, the qualitative analysis of the by-product dimethylamine in the circulating catalyst is performed by a method combining gas chromatography, nuclear magnetic resonance and mass spectrometry.
In the above preferred embodiment, the qualitative analysis of the by-product comprises the steps of:
(1) The method comprises the steps of recycling a circulating catalyst for catalyzing the synthesis of the methacrolein each time, carrying out a catalytic synthesis reaction of the methacrolein, and taking a reaction transient liquid and adding methanol in the reaction process, wherein the volume ratio of the reaction transient liquid to the methanol is 1:2, performing chromatographic analysis after the reaction liquid becomes a uniform phase, and comparing the components in each reaction system and the content change condition of each component;
(2) The homogeneous phase reaction liquid prepared in the step (1) is analyzed by a gas chromatograph-mass spectrometer, and the by-product generated in the catalysis process of the catalyst can be determined to be diethyl methylamine through preliminary analysis according to the determination result;
(3) Because most of the catalyst and the catalyst byproducts exist in the water phase reaction liquid, selecting the oil phase reaction liquid of the methylacrolein as a blank control group for chromatographic analysis to determine the composition of the methylacrolein, adding a small amount of dimethylamine standard substance into the oil phase reaction liquid, uniformly mixing and carrying out chromatographic analysis to verify the measurement result of the step (2);
(4) And (3) comparing the chromatographic peak position of the diethylmethylamine in the step (2) with the analysis result of the diethylmethylamine standard in the step (3) under the same detection condition, and determining that in the cyclic catalytic synthesis of the methacrolein, the catalyst undergoes side reaction to finally generate a byproduct diethylmethylamine, thereby losing the catalytic activity.
In a preferred embodiment, in the by-product qualitative analysis and by-product content determination steps, the gas chromatography includes:
Taking absolute ethyl alcohol as an internal standard substance and an N, N-diethyl methylamine standard sample as a reference substance, weighing a certain amount of absolute ethyl alcohol and the N, N-diethyl methylamine standard sample to prepare a reference solution, performing chromatographic analysis to obtain a chromatogram of the reference solution, and calculating a correction factor f according to the following formula:
（I）
In the above formula (I), A s and A r are the peak areas or peak heights of the anhydrous ethanol and N, N-diethylmethylamine standard samples, respectively, and m s and m r are the amounts of the anhydrous ethanol and N, N-diethylmethylamine standard samples added, respectively;
taking absolute ethyl alcohol as an internal standard, taking the circulating catalyst as a sample to be detected, weighing a certain amount of absolute ethyl alcohol and the circulating catalyst to prepare a test solution, carrying out chromatographic analysis to obtain a chromatogram of the test solution, and calculating the content m i according to the chromatographic peak response value of the component of the sample to be detected containing the internal standard, wherein the formula is as follows:
（II）
A i and a s are the peak areas or peak heights of the sample to be measured and the internal standard, respectively, and m s is the amount of the internal standard added.
In a preferred embodiment, in the by-product qualitative analysis and by-product content determination steps, the chromatographic conditions of the gas chromatography are:
Chromatographic column: KB-624;
column temperature: the initial temperature is 70 ℃, and the temperature is kept for 12min; heating at 70-240 deg.c and 40 deg.c/min for 20min;
Sample injection amount: 0.1-0.3 μl;
carrier gas: helium gas;
Split ratio: 20:1;
a detector: a hydrogen flame ionization detector; detector temperature: 300 ℃; sample injector: a split-flow sample injection device; injector temperature: 300 ℃.
In a preferred embodiment, the sample is introduced in an amount of 0.1. Mu.l.
In order to more clearly and in detail describe the method for measuring the effective components in the circulating catalyst for synthesizing methacrolein provided by the embodiment of the present invention, the following will describe in connection with the specific examples.
Example 1
The embodiment provides a qualitative analysis method of a byproduct diethyl methylamine, which comprises the following specific steps:
(1) In the process of circularly catalyzing and synthesizing the methacrolein by using the catalyst, respectively taking 10mL of the catalyst to catalyze the reaction liquid from the first catalysis time to the fourth catalysis time, adding 20mL of methanol for fully mixing, taking 1mL of a sample for gas chromatographic analysis after the reaction liquid and the methanol form a uniform solution (the experiment results are obtained after repeating six times of experiments), and finally obtaining a chromatographic analysis chart (shown in figures 1-4), wherein when the catalyst circularly catalyzes and synthesizes the methacrolein, the relative content of components which are out of peaks shows a remarkable increasing trend along with the increase of the circulation catalysis times of the catalyst when the reaction liquid is positioned for 9.25 min;
(2) The homogeneous phase reaction liquid prepared in the step (1) is analyzed by a gas chromatograph, so that a mass spectrum and a gas chromatograph (shown in figures 8-9) of the diethyl methylamine can be obtained, and a by-product generated in the catalytic process of the catalyst can be determined to be diethyl methylamine by preliminary analysis according to a determination result;
(3) According to the above results, selecting the methacrolein oil phase reaction liquid after the third reaction, and performing gas chromatography detection (the measurement result is shown in fig. 5), wherein the detection result shows that almost no byproduct dimethylamine exists in the methacrolein oil phase reaction liquid, therefore, selecting the methacrolein oil phase reaction liquid as a blank control group for performing chromatography analysis, adding a small amount of dimethylamine standard substance into the oil phase reaction liquid, uniformly mixing, and performing chromatography analysis (the measurement result is shown in fig. 6), and the method is used for verifying the measurement result of the step (2);
(4) The comparison of the chromatographic peak position of the dimethylamine in the step (2) and the analytical result of the dimethylamine standard in the step (3) under the same detection condition shows that the chromatographic peak time of the dimethylamine standard is about 9.25min, and the chromatographic peak time and the chromatographic shape of the dimethylamine which is a byproduct generated in the catalyst circulation process are basically consistent, so that the fact that the dimethylamine is generated in the methacrolein synthesis process can be verified and confirmed.
Example 2
The embodiment provides a method for measuring effective components in a circulating catalyst for synthesizing methacrolein, which specifically comprises the following steps:
(1) Determination of the content of byproducts: the content of the byproduct diethyl methylamine is determined by gas chromatography, and the method specifically comprises the following steps:
taking absolute ethyl alcohol as an internal standard substance and an N, N-diethyl methylamine standard sample as a reference substance, weighing a certain amount of absolute ethyl alcohol and the N, N-diethyl methylamine standard sample to prepare a reference solution, performing chromatographic analysis to obtain a chromatogram of the reference solution, and calculating a correction factor f, wherein the formula is as follows:
（I）
In the above formula (I), as and Ar are the peak areas or peak heights of the anhydrous ethanol and N, N-diethylmethylamine standard samples, respectively, and ms and mr are the amounts of the anhydrous ethanol and N, N-diethylmethylamine standard samples added, respectively;
Taking absolute ethyl alcohol as an internal standard, taking a circulating catalyst as a sample to be detected, weighing a certain amount of absolute ethyl alcohol and the circulating catalyst to prepare a test solution, carrying out chromatographic analysis to obtain a chromatogram of the test solution, and calculating the content m i according to the chromatographic peak response value of the component of the sample to be detected containing the internal standard, wherein the formula is as follows:
（II）
a i and a s are the peak areas or peak heights of the sample to be measured and the internal standard substance respectively, and m s is the amount of the internal standard substance added;
(2) Determination of the active ingredient in the circulating catalyst: calculating the loss amount of the circulating catalyst in the recovery process by adopting a total nitrogen analysis method (according to the specification of HJ 636-2012), and determining the loss amount of the diethylamine in the circulating catalyst in the recovery process by combining the content of the diethylamine, so as to obtain the actual effective contents of the diethylamine and the acetic acid in the circulating catalyst, wherein the total nitrogen analysis process comprises the following steps:
a) The method is as follows:
At 120-124 ℃, converting nitrogen of a nitrogen-containing compound in a sample into nitrate by using an alkaline potassium persulfate solution, respectively measuring absorbance A220 and absorbance A275 at the wavelength of 220nm and 275nm by adopting an ultraviolet spectrophotometry, calculating corrected absorbance A according to a formula (1), and enabling the total nitrogen (calculated by N) content to be in direct proportion to the corrected absorbance A.
A＝ A220－2A275（1）
B) The analysis step:
① Drawing of a Standard Curve
Respectively measuring 0.00mL, 0.20mL, 0.50mL, 1.00mL, 3.00mL and 7.00mL of standard potassium nitrate use solution in a 25mL glass colorimetric tube with a stopper, adding water to dilute to 10.00mL, adding 5.00mL of alkaline potassium persulfate solution, placing the colorimetric tube in a high-pressure steam sterilizer, heating to a top pressure valve for blowing, closing the valve, continuously heating to 120 ℃ for starting timing, and keeping the temperature between 120 ℃ and 124 ℃ for 30min. The vials were then removed, 1.0ml hydrochloric acid solution was added to each vial after the solution cooled and diluted with water to 25ml mark lines, and standard solutions were taken in 10mm quartz cuvettes to determine absorbance at wavelengths 220nm and 275nm, respectively. The corrected absorbance A b of zero concentration, the corrected absorbance A s of other standard series and the difference A r thereof are calculated according to formulas (2), (3) and (4), the total nitrogen (in terms of N) content (mug) is taken as an abscissa, the corresponding A r value is taken as an ordinate, and a calibration curve is drawn.
（2）
（3）
（4）
In the above formula:
A b: corrected absorbance of zero concentration (blank) solution; a b220: absorbance of zero concentration (blank) solution at wavelength 220 nm; a b275: absorbance of zero concentration (blank) solution at wavelength 275 nm; a s: corrected absorbance of the standard solution; a s220: absorbance of the standard solution at a wavelength of 220 nm; a s275: absorbance of the standard solution at a wavelength of 275 nm; a r: the standard solution corrects for the difference in absorbance from the zero concentration (blank) solution corrects for absorbance.
② Sample measurement
10.00Ml of the sample was measured in a 25ml glass cuvette with stopper and assayed according to the same procedure as in the standard curve.
③ Blank measurement
10.00Ml of distilled water was weighed into a 25ml glass cuvette with stopper and measured in the same manner as in the standard curve.
C) And (3) calculating results:
Calculating a corrected absorbance difference Ar of the sample and a corrected absorbance difference Ar of the blank test by referring to formulas (2) - (4), and calculating the mass concentration rho (mg/L) of total nitrogen in the sample according to formula (5).
（5）
Wherein:
ρ: the mass concentration of total nitrogen (in N) in the sample, mg/L; ar: the difference between the corrected absorbance of the sample and the corrected absorbance of the blank test; a: calibrating the intercept of the curve; b: the slope of the calibration curve; v: sample volume, mL; f: dilution factor.
Claims (3)
1. The method for measuring the effective components in the circulating catalyst for synthesizing the methacrolein is characterized in that the circulating catalyst is a diethylamine-acetic acid ionic liquid catalyst, the effective components are diethylamine and acetic acid, and the method comprises the following steps:
Qualitative analysis of byproducts: determining that in the cyclic catalytic synthesis process of the methacrolein, the catalyst undergoes side reaction to finally generate a byproduct diethyl methylamine by adopting a method combining gas chromatography, nuclear magnetic resonance and mass spectrometry, and carrying out qualitative analysis of the byproduct diethyl methylamine in the cyclic catalyst;
Determination of the content of byproducts: determining the content of the byproduct diethyl methylamine by gas chromatography;
Determination of the active ingredient in the circulating catalyst: calculating the loss amount of the circulating catalyst in the recovery process by adopting a total nitrogen analysis method, and determining the loss amount of diethylamine in the circulating catalyst in the recovery process by combining the content of the byproduct diethylamine, thereby obtaining the actual effective content of the effective component diethylamine in the circulating catalyst;
wherein in the steps of qualitative analysis of byproducts and determination of the content of the byproducts, the chromatographic conditions of the gas chromatography are as follows:
Chromatographic column: KB-624;
column temperature: the initial temperature is 70 ℃, and the temperature is kept for 12min; heating at 70-240 deg.c and 40 deg.c/min for 20min;
Sample injection amount: 0.1-0.3 μl;
carrier gas: helium gas;
Split ratio: 20:1;
a detector: a hydrogen flame ionization detector; detector temperature: 300 ℃; sample injector: a split-flow sample injection device; injector temperature: 300 ℃.
2. The method for determining an effective component in a circulating catalyst for synthesizing methacrolein according to claim 1, wherein in the by-product qualitative analysis and by-product content determination steps, the gas chromatography comprises:
Taking absolute ethyl alcohol as an internal standard substance and an N, N-diethyl methylamine standard sample as a reference substance, weighing a certain amount of absolute ethyl alcohol and the N, N-diethyl methylamine standard sample to prepare a reference solution, performing chromatographic analysis to obtain a chromatogram of the reference solution, and calculating a correction factor f according to the following formula:
（I）
In the above formula (I), A s and A r are the peak areas or peak heights of the anhydrous ethanol and N, N-diethylmethylamine standard samples, respectively, and m s and m r are the amounts of the anhydrous ethanol and N, N-diethylmethylamine standard samples added, respectively;
taking absolute ethyl alcohol as an internal standard, taking the circulating catalyst as a sample to be detected, weighing a certain amount of absolute ethyl alcohol and the circulating catalyst to prepare a test solution, carrying out chromatographic analysis to obtain a chromatogram of the test solution, and calculating the content m i according to the chromatographic peak response value of the component of the sample to be detected containing the internal standard, wherein the formula is as follows:
（II）
A i and a s are the peak areas or peak heights of the sample to be measured and the internal standard, respectively, and m s is the amount of the internal standard added.
3. The method for measuring an active ingredient in a circulating catalyst for synthesizing methacrolein according to claim 1, wherein the sample feeding amount is 0.1. Mu.l.
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