Alkane detection method
By combining a homemade atmospheric pressure chemical ionization (APCI) ion source device with water radical cation (H2O)2+·, the problem of low efficiency of alkane C-H bond activation in traditional methods was solved, and rapid, energy-saving and environmentally friendly alkane C-H bond activation and detection were achieved.
Patent Information
- Application Number
- CN202510541914.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2025-09-12
AI Technical Summary
Traditional methods are difficult to activate the C-H bonds in alkanes efficiently and selectively, and have problems such as high cost and low reaction efficiency.
A homemade atmospheric pressure chemical ionization (APCI) ion source was used to activate the CH bonds in alkanes by reacting water radical cations (H2O)2+ with alkanes. The reaction progress was monitored in real time using mass spectrometry technology.
It achieves rapid, energy-saving, environmentally friendly and efficient activation of C-H bonds in alkanes, improving the selectivity and detection efficiency of the reaction.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the fields of chemical basis and economics, and in particular to a method for detecting alkanes. Background Art
[0002] Alkanes are saturated, acyclic hydrocarbons that are the primary components of natural gas and crude oil. Their C-H and C-C bonds have high dissociation energies, exhibiting significant chemical inertness. This makes traditional oxidation methods difficult to effectively activate these bonds, thus limiting their conversion to more valuable compounds. C-H bond activation has long been a research hotspot in catalysis, and the structural characteristics of alkanes, lacking either low-energy empty orbitals or high-energy filled orbitals, further complicate chemical reactions. Furthermore, the strong thermodynamic stability of C-H bonds in alkanes means that their cleavage requires overcoming a high energy barrier, presenting a major challenge in alkane oxidation. Currently, a key challenge in alkane oxidation lies in how to efficiently and selectively activate C-H bonds. However, traditional methods have numerous limitations: while high-temperature activation can cleave C-H bonds, it suffers from poor selectivity and is often accompanied by numerous side reactions; metal-catalyzed activation requires the use of expensive transition metal catalysts, resulting in prohibitively high reaction costs; photoelectrocatalytic activation relies on semiconductor and electrode materials, which contributes to their high costs; and biocatalytic activation suffers from low reaction efficiency, susceptibility to metal poisoning of biological cells, and poor reaction stability. Therefore, developing a green, low-cost, simple, efficient, and highly selective method for activating and oxidizing the CH bonds of alkanes is of vital importance for promoting the efficient utilization of alkanes. Furthermore, converting abundant and low-cost alkane feedstocks into valuable products, such as commodities, intermediates, and fine chemicals, would have significant economic impact.
[0003] Water is a key element of life, participating in nearly every chemical reaction within organisms and playing a vital role in numerous fields, including life sciences, daily life, and social production. For this reason, water research has always been a hot topic of intense interest to scientists worldwide. For example, water radical cations play a vital role in numerous key natural processes, such as proton transfer, hydrogen bonding, cell damage, and atmospheric and interstellar chemistry. These discoveries have fueled a sustained growth in global research on water radical cations. Significant progress has also been made in the field of applied research. Water radical cations demonstrate significant potential for application in radiobiology and clinical medicine, making them a research hotspot.
[0004] Water radical cation (H2O)2 +· It has high reactivity and strong oxidizing ability, and its source is simple. It has been successfully used to generate (H2O)2 by corona discharge under normal pressure conditions. +·Its significant redox properties can trigger both reduction and oxidation reactions. (H2O)2 +· As a primary ion in mass spectrometry analysis, it significantly improves the sensitivity and selectivity of mass spectrometry detection. Its strong oxidizing ability has been fully demonstrated in the oxidation of benzene, spontaneous oxidation of aromatic sulfones, efficient oxidation of double bond molecules C=C, and efficient activation of N≡N inert bond disproportionation reactions. It has great advantages in activating inert bond energy. (H2O)2 +· It has lone pairs of electrons and positive charge centers, as well as free radical activation centers, and is expected to activate C-H bonds through a free radical chain mechanism to oxidize alkanes, thereby playing a catalytic role in chemical reactions and further expanding its value in scientific research and practical applications. Summary of the Invention
[0005] The purpose of the present invention is to provide a method based on a homemade atmospheric pressure chemical ionization (APCI) ion source device to explore and observe the chemical reaction between n-hexane and water radical cations, and to use mass spectrometry to monitor the reaction process in real time. +· This invention provides a highly innovative approach to rapidly, energy-saving, environmentally friendly, and efficiently activating C-H bonds in alkanes. The technical solutions of the invention are as follows:
[0006] A method for detecting alkanes is to build an APCI ion source device, use nitrogen to transport water and alkane samples to the mass spectrometer port, and at the same time the APCI ion source device ionizes water to produce (H2O)2 +· , combined with mass spectrometry to monitor alkanes and (H2O)2 in real time +· The reaction products between them and the content of the reaction products are calculated.
[0007] Furthermore, the flow rate of the nitrogen gas is 10 to 100 mL / min.
[0008] Furthermore, the APCI ion source device includes a water delivery channel, an alkane sample delivery channel and an ion source generating device;
[0009] The ion source generating device comprises a stainless steel needle which is coaxially inserted into a fused silica capillary tube and is connected to a high voltage power supply.
[0010] Furthermore, the voltage applied to the stainless steel needle is 2.0-3.0 kV.
[0011] Furthermore, the water delivery channel and the alkane sample delivery channel are peek tubes with an inner diameter of 0.75 mm.
[0012] Furthermore, the outer diameter of the stainless steel discharge needle is 150 μm, and the end curvature radius is 30 μm; the inner diameter of the fused silica capillary is 0.25 mm, and the outer diameter is 0.40 mm.
[0013] Furthermore, the mass spectrometer real-time monitoring conditions are as follows: the temperature in the ion transfer capillary is maintained at 150°C, the capillary voltage is 1.0V, the lens voltage is 30.0V, and the pressure vacuum in the ion trap is set to 1×10 -5 torr.
[0014] Furthermore, the alkane and (H2O)2 +· The online reaction also includes isotope labeling experimental detection and high-resolution mass spectrometry detection.
[0015] Furthermore, the isotope labeling experiment is a D2O-H2O detection method, specifically: nitrogen is used to pass through the D2O and alkane sample delivery channels to promote solution bubbling, voltage is applied to the stainless steel needle of the ion source device, and the alkane sample is added to the sample bottle of the alkane sample channel. The alkane gas and the deuterated water radical cation cluster undergo an oxidation reaction at the needle tip, and the reaction progress changes are monitored in real time in the mass spectrometer.
[0016] The beneficial effects of the present invention are as follows: the present invention designs and builds a self-made atmospheric pressure chemical ionization (APCI) ion source device, studies a new method for detecting alkanes, and provides a novel method for detecting (H2O)2 +· The rapid, energy-saving, environmentally friendly and efficient activation of C-H bonds in alkanes provides a highly innovative approach, has extremely important scientific value and broad application prospects, and is expected to promote major breakthroughs and innovations in the research field. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:
[0018] Figure 1 This is a schematic structural diagram of an APCI ion source device for online detection of alkane mass spectrometry according to an embodiment of the present invention; wherein, 1-water delivery channel, 2-alkane sample delivery channel, 3-ion source generating device;
[0019] Figure 2 Mass spectrometric data for the oxidation of alkanes by D2O-labeled water radical cations to form alkyl peroxides m / z 118. (a) Mass spectrum of the ion signal of the alkyl peroxide when H2O is replaced by D2O; (b) fragment ion fragments of m / z 118 analyzed by multi-stage MS spectra (m / z 118 → m / z 99);
[0020] Figure 3 High-resolution mass spectrometric data of the reaction of n-hexane oxidation to produce peroxides induced by water radical cations.
[0021] Figure 4 Hexane C6H 14 Standard curve of sample concentration and mass spectrometry signal intensity. DETAILED DESCRIPTION
[0022] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it should not be understood as a limitation on the scope of protection of the present invention.
[0023] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.
[0024] In the description of the present invention, "several" means one or more, "many" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.
[0025] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.
[0026] See also Figures 1 to 3 , the APCI ion source device used in the alkane detection method proposed by the present invention ( Figure 1 ), specifically including a water delivery channel 1, an alkane sample delivery channel 2, and an ion source generating device 3.
[0027] The specific detection method is to build the APCI ion source device, use nitrogen to propel water and alkane samples to the mass spectrometer port, and at the same time the APCI ion source device ionizes water to produce (H2O)2 +· , combined with mass spectrometry to monitor alkanes and (H2O)2 in real time +· The reaction products between.
[0028] The ion source generating device comprises a stainless steel needle which is coaxially inserted into a fused silica capillary tube and is connected to a high voltage power supply.
[0029] Specifically, the voltage applied to the stainless steel needle in the ion source device is 2.0-3.0 kV.
[0030] The water delivery channel and the alkane sample delivery channel are peek tubes with an inner diameter of 0.75 mm.
[0031] The stainless steel discharge needle has an outer diameter of 150 μm and a terminal curvature radius of 30 μm; the fused silica capillary has an inner diameter of 0.25 mm and an outer diameter of 0.40 mm.
[0032] The mass spectrometry real-time detection conditions are as follows: the temperature in the ion transfer capillary is maintained at 150°C, the capillary voltage is 1.0V, the lens voltage is 30.0V, and the pressure vacuum in the ion trap is set to 1×10 -5 torr.
[0033] Based on the above device, the specific method for detecting alkanes includes:
[0034] In (H2O)2 +· The generation channel uses N2 to protect the carrier gas flow through the peek tube, and forms a H2O / N2 vapor atmosphere through bubbling in water. The H2O / N2 vapor enters the tip of the stainless steel discharge needle of the ion source generator through the capillary. Voltage is applied to the needle tip to ionize the H2O / N2 vapor to produce a high abundance of (H2O)2 +· Through another alkane injection channel, nitrogen carrier gas is used to propel the alkane solution into bubbles and then carry the alkane gas to the tip of the discharge needle, where it interacts with the (H2O)2 +· Oxidation reaction occurs. Taking n-hexane as an example, (H2O)2 +· The alkane peroxide m / z 117 generated by the oxidation reaction with hexane can be clearly monitored on the mass spectrometer, and the content of the reaction product can also be calculated.
[0035] The following are some examples to verify the results of the above alkane detection method:
[0036] Example 1
[0037] At room temperature and pressure, a homemade APCI ion source device was built. Nitrogen gas with a flow rate of 10 mL / min was introduced into the water and alkane sample delivery channels to promote solution bubbling. A voltage of 2.0 kV was applied to the stainless steel needle of the ion source device. At 2.5 min, hexane sample was added to the sample bottle of the injection channel. The alkane gas and (H2O)2 +· The cluster undergoes oxidation reaction at the needle tip, (H2O)2 +· The ion signal of m / z 117, the ion signal of hexane forming peroxide, decreased significantly, and the ion signal of m / z 117, the ion signal of hexane forming peroxide, increased significantly. The reaction progress changes were monitored in real time in the mass spectrometer.
[0038] Example 2
[0039] At room temperature and pressure, a homemade APCI ion source device was built. Nitrogen gas with a flow rate of 100 mL / min was introduced into the water and alkane sample delivery channels to promote solution bubbling. A voltage of 2.0 kV was applied to the stainless steel needle of the ion source device. At 2.5 min, hexane sample was added to the sample bottle of the injection channel. The alkane gas and (H2O)2 +· The cluster undergoes oxidation reaction at the needle tip, (H2O)2 +· The ion signal of m / z 117, the ion signal of hexane forming peroxide, decreased significantly, and the ion signal of m / z 117, the ion signal of hexane forming peroxide, increased significantly. The reaction progress changes were monitored in real time in the mass spectrometer.
[0040] Example 3
[0041] At room temperature and pressure, a homemade APCI ion source device was built. Nitrogen gas with a flow rate of 100 mL / min was introduced into the water and alkane sample delivery channels to promote solution bubbling. A voltage of 3.0 kV was applied to the stainless steel needle of the ion source device. At 2.5 min, hexane sample was added to the sample bottle of the injection channel. The alkane gas and (H2O)2 +· The cluster undergoes oxidation reaction at the needle tip, (H2O)2 +· The ion signal of m / z 117, the ion signal of hexane forming peroxide, decreased significantly, and the ion signal of m / z 117, the ion signal of hexane forming peroxide, increased significantly. The reaction progress changes were monitored in real time in the mass spectrometer.
[0042] Test 1: D2O was used instead of H2O in Example 3. A homemade APCI ion source device was built at room temperature and pressure. Nitrogen gas at a flow rate of 100 mL / min was introduced into the D2O and alkane sample delivery channels to promote solution bubbling. A voltage of 3.0 kV was applied to the stainless steel needle of the ion source device. At 2.5 minutes, a hexane sample was added to the sample bottle of the injection channel. The alkane gas and the deuterated water radical cation cluster underwent an oxidation reaction at the needle tip. The deuterated water radical cation signal decreased significantly. The reaction progress was monitored in real time in the mass spectrometer. When H2O was replaced by D2O, a mass spectrometric signal of a peroxide ion product m / z 118 was detected. The ion fragment of m / z 118 was detected by the multi-stage MS spectrum. The results are shown in FIG. Figure 2 .
[0043] Test 2: Based on Example 3, the oxidation reaction process of alkanes and water radical cation clusters at the needle tip was detected in the mass spectrometer, and the reaction of alkanes and (H2O)2 was monitored by coupling with a high-resolution mass spectrometer. +· The mass spectrometry signals of the target reaction products m / z 117 and m / z 99 further verified the alkane detection results. Figure 3 .
[0044] Test 3: Based on the reaction device, the positive relationship between sample concentration and mass spectrometry signal was used to draw the hexane C6H14 The standard curve of sample concentration and mass spectrometry signal intensity is shown in Figure 4 , according to the mass spectrometry signal and combined with the curve relationship, the concentration of alkanes is calculated.
[0045] The present invention designed and built an atmospheric pressure chemical ionization (APCI) ion source device, studied a new method for detecting alkanes, and used n-hexane samples to conduct experiments to explore the reaction between n-hexane and water radical cations (H2O)2 +· The chemical reaction between the two is monitored in real time by mass spectrometry, and the reaction process and content are accurately detected, which is (H2O)2 +· The rapid, energy-saving, environmentally friendly and efficient activation of C-H bonds in alkanes provides a highly innovative approach, has extremely important scientific value and broad application prospects, and is expected to promote major breakthroughs and innovations in the research field.
[0046] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
[0047] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.
Claims
1. A method for detecting alkanes, characterized in that: Build an APCI ion source device and use nitrogen to transport water and alkane samples to the mass spectrometer port. At the same time, the APCI ion source device ionizes water to produce (H2O)2 +· , combined with mass spectrometry to monitor alkanes and (H2O)2 in real time +· The reaction products between them and the content of the reaction products are calculated.
2. The method for detecting alkanes according to claim 1, wherein: The flow rate of the nitrogen gas is 10-100 mL / min.
3. The method for detecting alkanes according to claim 1, wherein: The APCI ion source device includes a water delivery channel, an alkane sample delivery channel and an ion source generating device; the ion source generating device includes a stainless steel needle coaxially inserted into a fused silica capillary, and the stainless steel needle is connected to a high-voltage power supply.
4. The method for detecting alkanes according to claim 3, wherein: The voltage applied to the stainless steel needle is 2.0 to 3.0 kV.
5. The method for detecting alkanes according to claim 3, wherein the water delivery channel and the alkane sample delivery channel are peek tubes with an inner diameter of 0.75 mm.
6. The method for detecting alkanes according to claim 3, wherein: The stainless steel discharge needle has an outer diameter of 150 μm and a terminal curvature radius of 30 μm; the fused silica capillary has an inner diameter of 0.25 mm and an outer diameter of 0.40 mm.
7. The method for detecting alkanes according to claim 1, wherein: The mass spectrometer real-time monitoring conditions were as follows: the temperature in the ion transfer capillary was maintained at 150°C, the capillary voltage was 1.0V, the lens voltage was 30.0V, and the pressure vacuum in the ion trap was set to 1×10 -5 torr.
8. The method for detecting alkanes according to claim 1, wherein: The alkane and (H2O)2 +· The online reaction also includes isotope labeling experimental detection and high-resolution mass spectrometry detection.
9. The method for detecting alkanes according to claim 8, wherein: The isotope labeling experiment is a D2O-H2O detection method. Specifically, nitrogen gas is introduced into the D2O and alkane sample delivery channels to promote solution bubbling. Voltage is applied to the stainless steel needle of the ion source generator. The alkane sample is added to the sample bottle of the alkane sample channel. The alkane gas and the deuterated water radical cation cluster undergo an oxidation reaction at the needle tip, and the reaction progress is monitored in real time within the mass spectrometer.