A method for detecting boron trifluoride complexes and their impurities.

Abstract

This invention relates to the field of chemical process analysis technology, and particularly to a method for detecting boron trifluoride complexes and their impurities. The method involves treating highly corrosive samples with corrosion-resistant materials and sequentially detecting each component using commercially available independent equipment: a UV spectrophotometer is used to determine the main component of boron trifluoride and total acid; a mid-infrared ATR spectrometer is used to directly determine the water content and free organic acids in the underrived original sample, with the total acid concentration directly determined by the UV method. This invention requires no integrated system, completes the full analysis within 180 seconds, and has an inorganic acid concentration calculation error of <±3%, making it suitable for quality control of highly corrosive samples.

Description

Technical Field

[0001] This invention relates to the field of chemical process analysis technology, and in particular to a method for detecting boron trifluoride complexes and their impurity components. Background Technology

[0002] Boron trifluoride (BF3) complexes are important catalysts for alkylation, polymerization, and isomerization reactions, and their purity directly affects the performance and economic benefits of downstream products. Taking BF3·diethyl ether complex as an example, its purity directly affects catalytic activity, and the requirements are typically: free inorganic acids (HF, H2SO4) ≤ 0.03 wt%, moisture ≤ 0.05 wt%, and free organic acids (calculated as acetic acid) ≤ 0.02 wt%. To facilitate a comprehensive assessment of the impact of acid impurities on catalytic performance, the total acid concentration is defined as the mass percentage of all protic acids (including free inorganic acids, such as HF, and organic acids) measured by the indigo carmine bleaching method, with an upper limit of 0.05 wt%. Free organic acids (such as acetic acid) are quantified separately to distinguish the contribution of inorganic and organic acids when necessary. If any indicator exceeds the limit or the total acid exceeds 0.05 wt%, the sample is deemed unqualified. Therefore, developing a rapid multi-component detection method suitable for this highly corrosive system is of great significance.

[0003] Currently, the detection of boron trifluoride complexes mainly relies on offline methods. Gas chromatography (GC) analysis requires sample neutralization with alkali to avoid column damage, but alkaline conditions trigger irreversible hydrolysis of BF3, leading to systematically low main component detection values ​​(decomposition rate 15-22%). While Karl Fischer titration is the standard method for moisture detection, its long single-analysis cycle of up to 30 minutes fails to meet process quality control requirements, and it cannot distinguish between moisture and acid impurities. Ion chromatography (IC) for quantifying free acids often results in NaBF4 precipitate formation during pretreatment, which easily clogs the column, with a recovery rate of only 60-80%. These methods generally suffer from problems such as detection lag, complex sample pretreatment, and poor selectivity.

[0004] In recent years, near-infrared (NIR) online technology has attracted attention due to its fast response speed. However, its moisture detection relies on OH overtone absorption (the intensity of which is only 1 / 100 of the mid-infrared fundamental peak). Without complex model correction, the actual detection limit is usually only about 0.1 wt%, which is difficult to reliably meet the high purity requirement of 0.05 wt%. Acids lack characteristic overtone peaks and can only be measured indirectly, resulting in large errors. Furthermore, the C=O vibration of carboxylic acids in free organic acids overlaps severely with the OH overtone peak of moisture in the NIR region, and the model prediction error often exceeds 15%.

[0005] Therefore, there is an urgent need for a method that can quickly, accurately, and with corrosion resistance, and can simultaneously detect multiple components in boron trifluoride complexes. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a method for detecting boron trifluoride complexes and their impurity components.

[0007] This invention is achieved through the following technical solution: A method for detecting boron trifluoride complexes and their impurities includes the following steps: S1. Take the sample to be tested, add salicylaldehyde derivatizing reagent, and irradiate the sample under a 254nm ultraviolet lamp for 90±10 seconds to generate a 322nm characteristic absorber, which is recorded as the derivatizing solution. S2. Transfer the derivatized solution to a corrosion-resistant quartz cuvette, collect the 200-600 nm spectrum using a UV-Vis spectrophotometer, and determine the concentration of boron trifluoride main component based on the third derivative spectroscopy at 322 nm. S3. Take another underived sample, add indigo carmine indicator, and monitor the rate of change of absorbance at 610 nm over time using the same UV-Vis spectrophotometer. Calculate the total acid concentration C. total wt% S4. Take another underived sample and drop it directly onto the Al2O3-coated ZnSe crystal surface of the mid-infrared ATR attachment. Collect samples at 1400-1800 cm⁻¹ using a Fourier transform mid-infrared spectrometer. -1 Spectrum, resolution 4cm -1 The obtained spectrum was processed using the second derivative. The second derivative spectrum was then plotted at 1640 cm⁻¹. -1 The second-order peak is used to determine the water content, with a peak size of 1715 cm⁻¹. -1 Quantitative analysis of free organic acids based on the area of ​​the second-order peak; S5. The total acid concentration C measured in step S3 total wt% and the free organic acid concentration C measured in step S4 org Substitute wt% into the following formula to calculate the concentration of inorganic acid: C inorg wt%: C inorg =0.95×C total – 0.32×C org The coefficients were determined by multiple regression analysis of 120 standard samples. S6. Determine whether the sample is qualified based on the conditions.

[0008] Furthermore, in step S1, the derivatizing reagent is a 0.1 mol / L salicylaldehyde (salicylaldehyde concentration is 0.1 mol / L)-ethanol solution, and the volume ratio of the test sample to the salicylaldehyde-ethanol solution is 1:1.7.

[0009] Furthermore, in step S2, the third derivative spectroscopy method uses the Savitzky-Golay algorithm with a window width of 11 nm and a quantitative accuracy of ±0.8%.

[0010] Furthermore, in step S3, the total acid concentration is calculated as hydrofluoric acid HF, and includes both inorganic and organic acids.

[0011] Furthermore, in step S4, the ZnSe crystal surface of the mid-infrared ATR accessory is coated with a 2μm Al2O3 anti-corrosion coating, and the crystal thickness is 3mm.

[0012] Furthermore, in step S4, the second derivative processing adopts the Savitzky-Golay algorithm with a window of 9 points. The detection limit for moisture detection is ≤0.015wt%, and the detection limit for free organic acids, calculated as acetic acid, is ≤0.005wt%.

[0013] Furthermore, when the moisture content is greater than 0.05 wt%, the total acid concentration is greater than 0.05 wt%, the inorganic acid concentration is greater than 0.03 wt%, or the free organic acid concentration is greater than 0.02 wt%, the sample is deemed unqualified.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) High precision: The detection limit of moisture in this invention is 0.015wt%, acid is 0.005wt%, and the calculation error of inorganic acid concentration is <±3%, which is better than the near-infrared method; (2) Fast: The single-sample full analysis of this invention takes about 180 seconds (90 seconds of derivatization + 60 seconds of ultraviolet scanning + 30 seconds of infrared acquisition + calculation), which is 94% shorter than the offline GC method; (3) Simple equipment: This invention uses standard laboratory instruments, which do not require integration and have low cost per test; (4) Parameter synergistic inventiveness: This invention uses 254nm / 90s / 322nm third derivative / 610nm / 1640cm -1 / 1715cm -1 / 4cm -1 The combination of model coefficients 0.95 and -0.32, individually known but synergistically solved the specific challenge of multi-component detection of BF3 complexes, and deviations from either parameter led to a significant decrease in accuracy. Attached Figure Description

[0015] The present invention will now be further described with reference to the accompanying drawings.

[0016] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is the ultraviolet spectrum of the boron trifluoride acetic acid complex sample detected by the method of the present invention; Figure 3 This is the infrared spectrum of a boron trifluoride acetic acid complex sample detected by the method of the present invention. Detailed Implementation

[0017] The present invention will now be further described with reference to the accompanying drawings.

[0018] Example 1

[0019] I. Precise setting and collaborative optimization of detection parameters 1. Parameters of ultraviolet derivatization reaction UV excitation wavelength 254nm: This invention discovered that under 254nm UV excitation, salicylaldehyde and the BF3·acetic acid complex can rapidly react to generate a stable photochemical reaction product with characteristic absorption at 322nm. Kinetic studies show that the conversion rate can reach over 99% within 90 seconds, and the absorbance of the product at 322nm exhibits good linearity with the BF3 concentration in the range of 0.5-60wt% (R0). 2 =0.999), proving that this method can be used for the indirect quantification of principal components of BF3.

[0020] Reaction time 90±10 seconds: Kinetic studies showed that the conversion rate was approximately 85% at 60 seconds and over 99% at 90 seconds. After 120 seconds, the byproduct borate ester (318nm absorption) was significantly enhanced (peak height increase >0.02). A reaction time of 90 seconds was selected to balance complete conversion with minimal interference.

[0021] The concentration of the derivatizing reagent is 0.1 mol / L: salicylaldehyde-ethanol solution, with a sample to reagent volume ratio of 1:1.7 to ensure sufficient stoichiometry for the derivatization reaction.

[0022] The detection wavelength is 322 nm: the characteristic absorption peak of Schiff base derivatives, which differs from the 318 nm peak of borate esters by only 4 nm. Conventional ultraviolet light cannot distinguish them. This invention uses third-derivative spectroscopy (Savitzky-Golay algorithm, window width 11 nm) to effectively separate them, improving the quantitative accuracy from ±5% to ±0.8%.

[0023] Experimental verification: LC-MS analysis showed that the molecular weight of this product is [M+H]. + =226.1, this derivative has a characteristic absorption at 322 nm, and its absorbance shows good linearity with BF3 concentration in the range of 0.5-60 wt% (R0). 2 =0.999), proving that this method can be used for the indirect quantification of principal components of BF3.

[0024] 2. Free acid detection parameters Indigo carmine indicator (0.01%): undergoes irreversible oxidative fading under acidic conditions, following first-order kinetics, with the rate constant linearly related to the acid concentration (R² > 0.998).

[0025] Monitoring wavelength 610nm: the maximum absorption wavelength of indigo carmine, with minimal background interference, measurement time 120 seconds, detection limit 0.005wt%.

[0026] 3. Detection parameters for moisture and free organic acids Moisture content: 1640cm -1 OH bending vibration peak. Traditional mid-infrared water peak width (1630 cm). -1 While the peak height was close to the concentration (near 0.01-0.5 wt%), experiments showed that the peak height and concentration were linearly correlated (R²=0.999) in the range of 0.01-0.5 wt%, with a detection limit of 0.015 wt%, which is an order of magnitude higher than that of the near-infrared frequency doubling method (0.1 wt%).

[0027] Free organic acids: 1715cm -1 The C=O stretching vibration peak. The characteristic sharp peak of carboxylic acid and the broad peak of water were separated by ATR technology and second-order differential processing with a resolution >95%, avoiding water masking. The peak area, calculated as acetic acid, showed good linearity in the range of 0.005-0.2 wt%.

[0028] Infrared resolution 4cm -1 It can distinguish adjacent peaks while ensuring the signal-to-noise ratio.

[0029] Note: The determination of moisture and free organic acids must be performed using the original, underrived sample. Derivatized liquids should not be used, as the ethanol and water in the derivatization reagents may cause serious interference.

[0030] 4. Detection and Compensation Model for Acidic Substances Total acid concentration C measured by ultraviolet channel (indigo carmine bleaching method) total (Including the full contribution of inorganic and organic acids) and the infrared channel (1715cm) -1 The concentration of free organic acids C obtained by measuring peak area org There is signal cross-interference (calculated as acetic acid): free organic acids partially respond to the UV bleaching method, and inorganic acids also have a slight effect on the infrared C=O peak area. Through multiple regression analysis of 120 standard samples (BF3 complex matrix, with different concentrations of HF and acetic acid added), a method for determining the inorganic acid concentration C0 was established. inorg Compensation model: C inorg =0.95×C total –0.32×C org ; In the formula: C total The total acid concentration (wt%) was determined by ultraviolet light method, C org The concentration of free organic acids (wt%) was measured by infrared spectroscopy.

[0031] This invention can rapidly determine the total acid concentration C. total As a preliminary screening criterion (when C) total(Concentrations >0.05wt% are directly deemed unqualified). More importantly, the compensation model can accurately calculate the concentration C of more corrosive inorganic acids. inorg This model provides crucial data for process optimization and catalyst activity evaluation. It reduces the calculation error of inorganic acid concentration from ±18% to <3%, which is one of the core inventive aspects of this invention.

[0032] II. Systematic Application of Corrosion-Resistant Materials in the Testing Process In this method, all components in contact with highly corrosive samples (pH < 1, HF > 1000 ppm) are made of corrosion-resistant materials. .

[0033] Although some of the above materials are known, their application in a complete system for the detection of boron trifluoride complexes has not been previously reported, and their synergy with detection parameters ensures the feasibility and long-term stability of the method.

[0034] III. Equipment independence and ease of operation .

[0035] Example 2 like Figure 1 As shown, the overall process flow is as follows: 1. Preparation and Calibration Wear HF protective equipment and operate inside a fume hood.

[0036] Turn on the UV lamp (Zhongshi Walker PHRE-15) and preheat for 5 minutes, setting the wavelength to 254nm.

[0037] Turn on the UV spectrophotometer (Shimadzu UV-2600), perform a self-test, and set the scanning range to 200-600nm, slit width to 2nm, and medium-speed scanning.

[0038] Turn on the infrared spectrometer (Thermo Fisher Nicolet iS50), preheat the ATR accessory for 30 minutes, collect the background spectrum (air), and set the resolution to 4cm. -1 32 scans, range 4000-400cm -1 .

[0039] 2. Sample Derivatization Accurately transfer 1.00 mL of boron trifluoride-acetic acid complex sample (density approximately 1.05 g / mL, mass approximately 1.05 g) into a 10 mL quartz tube (with PTFE inner cap) using a PTFE pipette.

[0040] Add 1.70 mL of 0.1 mol / L salicylaldehyde-ethanol derivatizing reagent, tighten the cap and shake well.

[0041] Place the test tube 5 cm directly below the UV lamp and irradiate for 90 seconds (controlled by a timer).

[0042] 3. Principal component determination of BF3 The derivatized reaction solution was transferred to a 1 cm optical path quartz cuvette (with a PTFE coating on the inner wall).

[0043] Place the sample in a UV spectrophotometer, scan the absorption spectrum from 200 to 600 nm, and record the absorbance at 322 nm.

[0044] The third derivative was processed using the instrument's built-in software (UVProbe) (Savitzky-Golay, 11nm window), and the third derivative value at 322nm was read.

[0045] Substituting the values ​​into the pre-established standard curve (BF3 concentration vs. third-order peak height y = 0.0185x + 0.0005, R² = 0.9993), the calculated BF3 concentration is 53.0 wt% (the UV spectrum of the boron trifluoride acetic acid complex sample is shown in the figure). Figure 2 (As shown).

[0046] 4. Total acidity determination Take another 0.50 mL of the original sample (boron trifluoride-acetic acid complex sample) into another quartz test tube, add 0.10 mL of 0.01% indigo carmine indicator, and mix well.

[0047] Transfer the sample to a 1cm optical path quartz cuvette, place it in a UV spectrophotometer, set the time scan mode to wavelength 610nm, take a reading every 10 seconds for 120 seconds.

[0048] Record the change in absorbance A with time t, and plot the ln(A0 / A) ~ t graph with slope k = 0.0220 s. -1 .

[0049] Substituting into the total acid standard curve (k vs. total acid concentration, equivalent concentration based on HF), y = 0.60x + 0.001, R0 2 =0.998), resulting in a total acid concentration of 0.035wt%.

[0050] 5. Determination of moisture and free organic acids Take another 0.20 mL of the original underived sample (boron trifluoride-acetic acid complex sample) and add it directly to the surface of the ZnSe crystal (which has been coated with a 2 μm Al2O3 coating) on ​​the ATR accessory using a PTFE dropper, so that the liquid completely covers the crystal.

[0051] The infrared spectrometer was started to collect spectra (the infrared spectrum of the boron trifluoride acetic acid complex sample is shown in the figure). Figure 3 (As shown), range 1400-1800cm-1 4cm resolution -1 , scanned 32 times.

[0052] The acquired spectra were processed using the second derivative (Savitzky-Golay algorithm, 9-point window).

[0053] Measured 1640cm -1 The peak height of the second guide (baseline correction) is substituted into the moisture standard curve (peak height vs. H2O content, y = 0.0125x + 0.002, R0). 2 = 0.999), yielding a moisture content of 0.042wt% (this value is acceptable, retain the original data).

[0054] Measured 1715cm -1 Peak area of ​​the second derivative (integration range 1700-1730 cm⁻¹) -1 Substituting this into the free organic acid standard curve (peak area vs. acetic acid content, y = 0.028x + 0.001, R0), we find the value of y. 2 =0.997), yielding 0.015 wt% free organic acid (calculated as acetic acid).

[0055] 6. Quality Judgment Calculate the inorganic acid concentration using the formula: C_inorg=0.95×C_total–0.32×C_org=0.95×0.035–0.32×0.015=0.03325–0.0048=0.02845wt% (about 0.028wt%).

[0056] Judgment: Moisture 0.042wt% < 0.05wt%, Total acid concentration 0.035wt% < 0.05wt%, Free organic acid 0.015wt% < 0.02wt%, Inorganic acid concentration 0.028wt% < 0.03wt%. Overall judgment: Sample is qualified.

[0057] Example 3: The impact of parameter deviation on detection accuracy (comparative experiment) To demonstrate the critical significance of parameter selection in this invention, the following comparative experiment was conducted (samples were the same as in Example 1): .

[0058] The results show that the parameter range defined by the present invention has a criticality, and deviations will significantly affect the detection accuracy or equipment lifespan.

[0059] Industrial Application Prospects This invention's method is applicable to quality control laboratories of boron trifluoride complex (such as BF3·diethyl ether, BF3·methanol, BF3·acetic acid, etc.) manufacturers, third-party testing institutions, and small and medium-sized factories lacking online analysis capabilities. This combination of detection parameters can be developed into a standard operating procedure (SOP), potentially becoming an industry-recommended method, particularly suitable for the rapid and accurate analysis of highly corrosive, multi-component samples.

Claims

1. A method for detecting boron trifluoride complexes and their impurity components, characterized in that, Includes the following steps: Step S1: Take the sample to be tested, add salicylaldehyde derivatizing reagent, the derivatizing reagent is 0.1 mol / L salicylaldehyde-ethanol solution, the volume ratio of the sample to the salicylaldehyde-ethanol solution is 1:1.7, irradiate the reaction under a 254 nm ultraviolet lamp for 90±10 seconds, and generate a 322 nm characteristic absorber, which is recorded as the derivatizing solution. Step S2: Transfer the derivatized solution to a corrosion-resistant quartz cuvette, collect the 200-600 nm spectrum using a UV-Vis spectrophotometer, and determine the concentration of boron trifluoride main component based on the third derivative spectroscopy at 322 nm. Step S3: Take another underived sample, add indigo carmine indicator, and monitor the rate of change of absorbance at 610 nm over time using the same UV-Vis spectrophotometer. Calculate the total acid concentration C. total wt% Step S4: Take another underived sample and drop it directly onto the Al2O3-coated ZnSe crystal surface of a mid-infrared ATR attachment. Collect samples at 1400-1800 cm⁻¹ using a Fourier transform mid-infrared spectrometer. -1 The spectrum was processed by second derivative, and the second derivative spectrum was plotted at 1640 cm⁻¹. -1 The second-order peak is used to determine the water content, with a peak size of 1715 cm⁻¹. -1 Quantitative analysis of free organic acids based on the area of ​​the second-order peak; Step S5: Utilize the total acid concentration C measured in step S3. total wt% and the free organic acid concentration C measured in step S4 org The inorganic acid concentration is obtained by weight (wt%). Step S6: Determine whether the sample is qualified based on the conditions; The sample is deemed unqualified when the moisture content is greater than 0.05 wt%, the total acid concentration is greater than 0.05 wt%, the inorganic acid concentration is greater than 0.03 wt%, or the free organic acid concentration is greater than 0.02 wt%.

2. The method for detecting boron trifluoride complexes and their impurity components according to claim 1, characterized in that: In step S2, the third derivative spectroscopy method uses the Savitzky-Golay algorithm with a window width of 11 nm and a quantitative accuracy of ±0.8%.

3. The method for detecting boron trifluoride complexes and their impurities according to claim 1, characterized in that: In step S3, the total acid concentration is expressed as hydrofluoric acid (HF) and includes both inorganic and organic acids.

4. The method for detecting boron trifluoride complexes and their impurities according to claim 1, characterized in that: In step S4, the ZnSe crystal surface of the mid-infrared ATR accessory is coated with a 2μm Al2O3 anti-corrosion coating, and the crystal thickness is 3mm.

5. The method for detecting boron trifluoride complexes and their impurities according to claim 1, characterized in that: In step S4, the second derivative processing adopts the Savitzky-Golay algorithm with a window of 9 points. The detection limit for moisture detection is ≤0.015wt%, and the detection limit for free organic acids, calculated as acetic acid, is ≤0.005wt%.

6. The method for detecting boron trifluoride complexes and their impurity components according to claim 1, characterized in that: In step S5, the concentration of inorganic acid is calculated: C inorg wt%: C inorg =0.95×C total – 0.32×C org .

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