CN115552216A - In-situ real-time programmed temperature analysis method - Google Patents
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Abstract
An in-situ real-time temperature programmed analysis method, comprising: dropwise adding a sample to be tested to a sample coating area of at least one test sensor (1); carrying out temperature programming on a test sensor (1) within a first preset temperature range to obtain a baseline; the baseline is obtained by recording the resonance frequency change data of the test sensor (1) in the temperature programming process; carrying out temperature programming on the test sensor (1) within a second preset temperature range to obtain a measurement curve; the measurement curve is obtained by recording the resonance frequency change data of the test sensor (1) in the temperature programming process; and obtaining a temperature programming analysis curve according to the baseline and the measurement curve. The test sensor (1) with the heating and data acquisition functions is integrated to perform temperature programmed analysis on the sample to be detected, so that the hysteresis of the detection result is reduced, the accuracy is high, the response is sensitive, the temperature programmed analysis method is simplified, and the accurate quantitative analysis of the sample is realized.
Description
The invention relates to the technical field of analysis and measurement control, in particular to an in-situ real-time programmed temperature analysis method.
The catalytic reaction of molecules on the surface of the catalyst needs to go through a plurality of steps, wherein the most important is two steps of adsorption and surface reaction, so to clarify the action nature of the catalyst and the mechanism of the reaction molecules and the action thereof in the catalytic process, the properties of the catalyst, such as activity, active site distribution, active site content and the like, must be deeply studied. Temperature Programmed Analytical Technology (TPAT) is a widely used method for analyzing catalytic materials.
Due to the detection precision of a balance, the existing temperature programming analysis method basically detects the composition and concentration change of escaping gas by a mass spectrometer or a thermal conductivity detector to reversely deduce the change of a detection sample in the temperature programming process, and the weight change of the material cannot be obtained in situ and in real time. The limit of detection of such methods depends on the performance of the mass spectrometer or thermal conductivity detector. Therefore, the existing temperature programming analysis method can only realize qualitative or semi-quantitative analysis; the acquired data has a certain hysteresis effect, which affects the accuracy of the measurement result; in addition, the system for realizing the temperature programming analysis has the advantages of complex structure, high price and large sample demand.
Disclosure of Invention
The invention aims to solve the technical problems that the existing temperature programming analysis method needs to detect the escaping gas, cannot realize in-situ real-time acquisition of a temperature programming curve, and has high cost, low accuracy and hysteresis effect.
In order to solve the technical problem, an embodiment of the present application discloses an in-situ real-time temperature programming analysis method, including:
dropwise adding a sample to be tested in a sample coating area of at least one test sensor;
carrying out temperature programming on the test sensor within a first preset temperature range to obtain a baseline; the baseline is obtained by recording the resonance frequency change data of the test sensor in the temperature programming process;
carrying out temperature programming on the test sensor within a second preset temperature range to obtain a measurement curve; the measurement curve is obtained by recording the resonance frequency change data of the test sensor in the temperature programming process;
and obtaining a temperature programming analysis curve according to the baseline and the measurement curve.
Further, the test sensor is arranged in a sealed cabin with a sealed cavity structure;
the sealing cabin is provided with a gas guide port for communicating the cavity structure, and the gas guide port is used for introducing protective gas or reaction gas into the sealing cabin;
the protective gas is used for purging the test sensor; the reaction gas is used for reacting with the sample to be detected.
Further, the test sensor comprises a high-temperature heating part and a low-temperature collecting part;
the high-temperature heating part is provided with a heating element and the sample coating area, and the sample coating area is used for loading the test sample; the heating element is used for heating the sample coating area;
the low-temperature acquisition part is provided with a sensor driving unit and a signal detection unit, and the sensor driving unit is used for driving the test sensor to generate resonant frequency; the signal detection unit is used for detecting the resonant frequency of the test sensor.
Further, the reaction between the reaction gas and the sample to be detected at least includes an adsorption reaction, an oxidation reaction, a reduction reaction, and a vulcanization reaction.
Further, the programming the test sensor to a first preset temperature range to obtain a baseline includes:
introducing the protective gas into the sealed bin under a preset gas pressure;
carrying out temperature programming on the test sensor within the first preset temperature range;
acquiring the resonant frequency of the test sensor detected by the signal detection unit in the temperature programming process;
the baseline is obtained from data on changes in the resonant frequency.
Further, the temperature programming the test sensor in a second preset temperature range to obtain a measurement curve includes:
introducing the reaction gas into the sealed bin under a preset gas pressure;
carrying out temperature programming on the test sensor within the second preset temperature range;
acquiring the resonant frequency of the test sensor detected by the signal detection unit in the temperature programming process;
and obtaining the measuring curve according to the change data of the resonant frequency.
Further, the obtaining a temperature programming analysis curve according to the baseline and the measurement curve includes:
obtaining a frequency difference temperature curve according to the baseline and the measurement curve;
and processing the frequency difference temperature curve according to the type of the reaction between the reaction gas and the sample to be detected to obtain the temperature programming analysis curve.
Further, before the programming the temperature of the test sensor within the first preset temperature range to obtain the baseline, the method further includes:
placing the test sensor in the sealed bin;
and introducing the protective gas into the sealed cabin to blow the sample to be tested, the test sensor and the gas circuit.
Further, in the process of carrying out a temperature programmed desorption test according to the in-situ real-time temperature programmed analysis method, the reaction gas is an adsorptive gas, and the reaction between the reaction gas and the sample to be detected is an adsorption reaction; before the temperature programming is performed on the test sensor within a second preset temperature range to obtain a measurement curve, the method further includes:
introducing the adsorptive gas into the sealed bin under a preset pressure;
heating the sample to be detected to a first preset temperature to enable the surface adsorption degree of the sample to be detected to reach the maximum coverage degree;
and heating the sample to be detected to a second preset temperature, and removing the physical adsorption of the adsorptive gas molecules on the surface of the sample to be detected.
By adopting the technical scheme, the in-situ real-time programmed temperature analysis method has the following beneficial effects:
the in-situ real-time programmed temperature analysis method provided by the embodiment of the application performs programmed temperature analysis on a sample to be detected by adopting the test sensor which is integrated with heating and data acquisition functions, can realize simultaneous execution of a heating process and a detection process on the sample in the programmed temperature process, realizes in-situ real-time programmed temperature analysis, greatly reduces the hysteresis of a detection result, has high accuracy, sensitive reaction and low cost, greatly simplifies the programmed temperature analysis method, and realizes accurate quantitative analysis on the sample.
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a temperature programmed analyzer according to an embodiment of the present application;
FIG. 2 is a schematic structural diagram of a test sensor according to an embodiment of the present disclosure;
FIG. 3 is a schematic flow chart of an in-situ real-time temperature programmed analysis method according to an embodiment of the present application;
fig. 4 is a diagram of a frequency variation of a sample to be measured placed in a temperature programmed analyzer for heating according to an embodiment of the present disclosure;
FIG. 5 is a TPD graph of a ZSM-5 molecular sieve as a sample to be tested placed in a temperature programmed analyzer according to an embodiment of the present disclosure;
fig. 6 is a TPD graph of a sample to be measured, which is a beta molecular sieve, placed in a temperature programmed desorption analyzer according to the present application;
FIG. 7 shows a method for preparing gamma-Al sample 2 O 3 Putting the TPD curve chart of a temperature programmed desorption analyzer;
the following is a supplementary description of the drawings:
1-a test sensor; 11-a high temperature heating section; 12-a low temperature collection part; 121-a sensor drive unit; 122-a signal detection unit; 21-an atmosphere control system; 211-a shielding gas circuit; 212-reaction gas circuit; 213-a reversing valve; 214-a sealed bin; 22-analytical test System.
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the present application. In the description of the present application, it is to be understood that the terms "upper", "lower", "top", "bottom", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.
Several analysis and test methods commonly used in the temperature programmed analysis technology include temperature programmed desorption, temperature programmed reduction, temperature programmed oxidation, temperature programmed surface reaction, and the like.
The principle of Temperature Programmed Desorption (TPD) is: desorption occurs when molecules adsorbed on the surface of a solid are heated to a point where they overcome the potential barrier (commonly referred to as the desorption activation energy) they need to overcome to escape. The energy required for desorption is different due to the different binding capacities between different adsorbates and the same surface, or between the same adsorbate and adsorption centers of different nature on the surface. Therefore, the desorption experiment result not only reflects the binding capacity between the adsorbate and the solid surface, but also reflects the dynamic behavior under the temperature and the surface coverage when desorption occurs.
Temperature Programmed Reduction (TPR) is a reduction process that is carried out at constant temperature. If the sample is reduced in the temperature rise process, the concentration of the hydrogen in the gas phase changes along with the temperature change, and the change process is recorded to obtain the TPR graph of the hydrogen concentration along with the temperature change. The TPR is often used to characterize supported metal or transition metal oxide catalysts, and the analysis of the TPR results can obtain information on the interaction between the metal and the carrier, the valence state of the metal, whether an alloy is formed, and the like. When the valence state, aggregation state and carrier action of the loaded metal are changed, the reduction temperature and the reduced valence state of the loaded metal are changed, and if the consumption of hydrogen in the programmed heating reduction process, the reduction temperature and the like can be measured, some state parameters of the loaded metal can be obtained.
Temperature Programmed Oxidation (TPO) is a method for checking the degree of oxidation of a catalyst, and in general, in the case of a metal catalyst, a reaction gas of 2% oxygen/carrier gas mixture is passed through a sample by a pulse injection method or a steady gas flow method after the catalyst is subjected to reduction pretreatment as a base metal. The temperature of the sample is programmed to rise, and the oxidation reaction is carried out at a certain temperature, so that the proportion of the mixed gas is changed due to the consumption of oxygen, and the oxygen consumption of the sample is detected by a detector.
By Temperature Programmed Surface Reaction (TPSR) is meant that during the temperature programming, surface reactions and desorption occur simultaneously. Firstly, adsorbing and reacting the pretreated catalyst under reaction conditions, and then, raising the temperature from room temperature to a required temperature by a program, so that various surface species adsorbed on the catalyst are desorbed while reacting; the other is that the carrier gas used for desorption is a reactant, and in the process of temperature programming, the carrier gas (or a certain component in the carrier gas) reacts with a certain adsorbed species formed on the surface of the catalyst and desorbs the adsorbed species. Obviously, neither the reaction of the adsorbed species nor the desorption of the product is isolated. Therefore, TPSR is in essence closely related to TPD. The experimental results obtained for TPSR reflect the kinetics of reaction and desorption at a certain temperature and surface coverage.
A conventional temperature programmed analysis technique will be described with TPD as an example. In the prior art, the TPD analysis device mainly comprises a gas purification and switching unit, a reaction and temperature control unit and an analysis and detection unit. The gas purification and switching unit realizes the functions of gas purification and switching, the functions of reaction and temperature control in the electric furnace, and the functions of analysis and detection by a mass spectrometer or a thermal conductivity detector. The specific principle and steps are as follows: firstly, a sample to be detected is placed in a heating furnace, a gas valve is switched to ensure that carrier gas does not pass through the sample and only pretreatment gas passes through the sample. After the sample is pretreated by a certain temperature and a certain amount of gas, the gas valve is switched to enable the adsorbed gas to flow through the sample, after the adsorption is saturated, the carrier gas is continuously used for blowing the gas to balance the thermal conductivity base line so as to desorb the physical adsorption, and then the temperature is programmed. As the temperature of the sample rises, the adsorbed molecules previously adsorbed on the surface of the solid substance begin to desorb due to thermal motion. The concentration change of the desorbed substances in the effluent gas is detected, and a TPD curve can be obtained.
However, the conventional TPD analysis method can measure only the adsorbate concentration at a certain time, and a certain time is required for the adsorbate to desorb from the sample surface and flow into the analysis detection unit, i.e., the detection result has hysteresis of the desorbed adsorbate concentration with respect to temperature. Thereby obtaining inaccurate adsorbate concentration versus temperature changes at higher ramp rates, and even causing overlap of different desorption stages, resulting in test failure. And therefore can only be used at lower ramp rates. Furthermore, when the sample desorbs less adsorbate, the sensitivity of the detection device is not sufficient to detect the desorbed adsorbate. Moreover, the analysis and detection unit is an independent instrument, so that the temperature programmed desorption analysis device has a complex structure and is expensive.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a temperature programmed analyzer according to an embodiment of the present application, and as shown in fig. 1, the temperature programmed analyzer includes: capsule 214, atmosphere control system 21, and analytical test system 22.
The sealed cabin 214 has a sealed cavity structure, at least one test sensor 1 is arranged in the sealed cabin 214, and the test sensor 1 is used for collecting temperature programmed analysis data of a test sample. The test sensor 1 is a resonant micro-cantilever sensor with a self-heating function. The test sensor 1 includes a high-temperature heating part 11 and a low-temperature collection part 12, the high-temperature heating part 11 is provided with a heating element and a sample application region, the sample application region is used for loading a test sample, and the heating element is used for heating the sample application region. Low temperature collectionPortion 12 is connected with the inner wall of the cavity structure, and low temperature collection portion 12 is used for gathering the programming analysis data of the test sample in the sample coating area. Test sensor 1 is located within capsule 214. The sealed chamber 214 has a sealed cavity structure, and the low-temperature collection part 12 is connected with the inner wall of the cavity structure. A single test sensor 1 may be disposed within the capsule 214, or an array of multiple test sensors 1 may be disposed to achieve high throughput detection. The capsule 214 provides a sealed test environment for the test sensor 1. The test sensor 1 detects the adsorption and desorption conditions of the sample through the change of the measured mass of the sample. Depending on the geometry of the test sensor 1, the amount of gas adsorption or desorption resolvable by the test sensor 1 is 10 -15 g to 10 -6 g. The test sensor 1 provides the necessary temperature conditions for adsorption and desorption of the sample.
Fig. 2 is a schematic structural diagram of a test sensor 1 according to an embodiment of the present disclosure, and as shown in fig. 2, the test sensor 1 is an integrated resonant cantilever beam, the integrated resonant cantilever beam includes a fixed end and a cantilever end, the cantilever end is a mass-sensitive end of the test sensor 1, the high-temperature heating portion 11 is disposed at the cantilever end, and the low-temperature collecting portion 12 is at least partially disposed at the fixed end. The high-temperature heating part 11 is provided with a heating element for heating and measuring temperature. Alternatively, the heating element is a heating circuit provided when the test sensor 1 is prepared. The heating element is used for heating the sample to be measured and feeding back the temperature value of the sample coating area. Optionally, the heating element may achieve a heating temperature in the range of 25 ℃ to 1300 ℃. The low temperature collection unit 12 is used to detect the change in the mass of the sample and thereby detect the adsorption and desorption states of the sample. The low temperature collection part 12 is connected to an analysis and test system 22, and the analysis and test system 22 is used for controlling the test sensor 1 and processing the temperature programmed analysis data collected by the test sensor 1 to obtain a temperature programmed analysis curve of the test sample. The low temperature collection part 12 is provided with a sensor driving unit 121 and a signal detection unit 122, and both the sensor driving unit 121 and the signal detection unit 122 are connected with the analysis test system 22. The sensor driving unit 121 is used to drive the test sensor 1 to generate a resonant frequency. For the signal detection unit 122To detect the resonant frequency of the test sensor 1. The sensor driving unit 121 and the signal detecting unit 122 can form a closed loop, and realize resonance driving and resonance frequency detection of the integrated resonant cantilever. In some embodiments, a temperature control unit is further disposed in the low temperature collection portion 12, and the temperature control unit is connected to the heating element for controlling the temperature of the heating element. The low temperature collection part 12 monitors the mass change of the sample by testing the change of the resonant frequency of the cantilever beam, thereby realizing the monitoring of the adsorption and desorption states of the sample. The integrated resonant cantilever beam can realize a heating rate of more than 5000 ℃/s, the temperature control precision is within 0.5 ℃, and the temperature and the desorption process can be accurately corresponded. The minimum detection mass of the test sensor 1 is as small as 10 -15 Even trace desorption can also be reflected on the change of the resonance frequency of the cantilever beam, the detection sensitivity is high, and the dosage of the sample required by detection can be greatly reduced.
In the embodiment of the present application, as shown in fig. 1, different samples have different required atmospheres in the temperature programmed desorption test process, and in order to meet the requirements of different samples on the test atmospheres, the program analyzer further includes an atmosphere control system 21 that provides necessary atmosphere conditions for the whole temperature programmed desorption test process. The sealed cabin 214 is provided with an air guide port communicated with the cavity structure, and the atmosphere control system 21 is communicated with the sealed cabin 214 through the air guide port. The atmosphere control system 21 includes a shielding gas circuit 211 and a reaction gas circuit 212, and the shielding gas circuit 211 and the reaction gas circuit 212 are respectively connected to the gas guiding ports. The atmosphere control system 21 may effect switching between the shielding gas and the reactant gas. The shielding gas path 211 can be changed according to the test requirement, and the reaction gas path 212 can be changed according to the test requirement. As an alternative embodiment, the sealed cabin 214 is provided with two air guide ports, the shielding gas path 211 is connected with one of the air guide ports, and the reaction gas path 212 is connected with the other air guide port. Optionally, the shielding gas circuit 211 and the reaction gas circuit 212 are respectively provided with a control valve capable of controlling on/off of each gas circuit. As another alternative, the sealed chamber 214 is provided with a gas guide port, and the atmosphere control system 21 further comprises a gas reversing valve 213 for reversing the gasThe valve 213 has three-way ports, one of which is connected to the gas guide port, and the other two of which are connected to the shielding gas path 211 and the reaction gas path 212, respectively. In some embodiments, the atmosphere control system 21 further comprises a pressure control unit comprising a vacuum pump for evacuating the capsule 214, a pressure sensor and a controller; the air pressure sensor is used for detecting the air pressure inside the sealed cabin 214; the control unit is used for receiving the pressure signal sent by the air pressure sensor and controlling the starting and stopping of the vacuum pump according to the pressure signal. The pressure control range of the air pressure control unit is 10 -7 Mpa-10 -4 Mpa. As an alternative embodiment, the air pressure control unit is provided with an air extraction path for connecting the sealed cabin 214, and the air extraction path is used for extracting air from the sealed cabin 214 to make the pressure of the sealed cabin 214 reach the set working value. The air pumping path is connected with a vacuum pump, a flowmeter and a control valve for controlling the on-off of the air path; the air pressure control unit also comprises an air pressure sensor for detecting the pressure of the sealed cabin 214, and a controller connected with the control valve and the vacuum pump, wherein the controller is used for receiving a pressure signal of the air pressure sensor, controlling the vacuum pump to be started and the control valve to be opened when the air pressure of the sealed cabin 214 reaches a set air extraction value, and controlling the vacuum pump to be stopped and the control valve to be closed when the air pressure of the cavity to be detected reaches a set working value.
In the embodiment of the present application, as shown in fig. 1, the temperature programmed analyzer further includes an analysis and test system 22. The analysis test system 22 provides necessary driving signals and heating signals for the test sensor 1, and processes monitoring signals and temperature signals fed back by the test sensor 1. The analytical test system 22 is connected to the integrated test sensor 1, and the sealed chamber 214 is provided with a port for connecting the test sensor 1 to the analytical test system 22. The analysis and test system 22 is used for controlling and detecting the temperature of the mass-sensitive end of the test sensor 1, driving the test sensor 1 to work, and detecting the adsorption and desorption conditions of the sample at the mass-sensitive end. The analysis and test system 22 is respectively connected to the sensor driving unit 121 and the signal detection unit 122, and the analysis and test system 22 provides a signal for driving the quality sensor to normally operate, and receives a signal fed back by the element to measure the temperature. The analysis test system 22 receives the output signal of the signal detection unit 122 and analyzes the received result.
In the embodiment of the application, the heating and detection processes of the sample are simultaneously carried out, so that the hysteresis of analysis in the traditional process is greatly reduced; and the gas desorption quantity can be completely reflected in the change of the resonance frequency of the cantilever beam by detecting and heating simultaneously, so that the test is more sensitive and accurate. Compare with traditional temperature programming test equipment who relies on mass spectrograph or thermal conductivity detector analysis and detection, relies on electric stove heating and accuse temperature, the application temperature programming analysis appearance have the simple small and exquisite, can realize advantages such as accurate quantitative analysis, test time are short, can high flux detect of system.
Specific embodiments of an in-situ real-time temperature programmed analysis method according to the present application are described below. Fig. 3 is a schematic flow chart of an in-situ real-time temperature programmed analysis method provided in the embodiments of the present application, and the present specification provides the method operation steps as in the embodiments or the flow chart, but may include more or less operation steps based on conventional or non-inventive labor. The order of steps recited in the embodiments is merely one manner of performing the steps in a multitude of orders and does not represent the only order of execution. In practice, the system or server product may be implemented in sequential or parallel execution according to the embodiments or methods shown in the drawings. Specifically, as shown in fig. 3, the method includes the following steps:
s301: a sample to be tested is dropped onto the sample coated area of at least one test sensor 1.
In the embodiment of the present application, before dropping the sample to be tested on the sample application area of the at least one test sensor 1, the influence of the original contamination on the beam on the test is also removed. Specifically, the shielding gas path 211 is communicated with the sealed cabin 214, shielding gas is introduced into the sealed cabin 214, and the heating element is started to heat the sample coating area, so as to remove the contaminants on the sample coating area. The protective gas is inert gas, nitrogen or other gases which are not easy to react with the sample to be detected. In some embodiments, the sealed chamber 214 may be evacuated by turning on a vacuum pump, and a suitable voltage is applied to the heating element in the high-temperature heating portion 11 of the test sensor 1 under a vacuum environment to remove the influence of the original contamination on the beam on the test. After the contaminants are removed, the liquid containing the sample to be tested is accurately spotted into the sample application area of the test sensor 1. Optionally, the liquid containing the sample to be detected includes a solution of the sample to be detected, a suspension containing the sample to be detected, a colloid containing the sample to be detected, and the like. Optionally, the liquid containing the sample to be tested is obtained by the following method: the sample reagent to be detected is uniformly dispersed in the solvent, and the uniform dispersion of the sample reagent to be detected in the solvent can be realized by an ultrasonic stirring method. Optionally, the solvent includes a soluble liquid such as deionized water or ethanol.
S303: the test sensor 1 is programmed to warm up within a first preset temperature range to obtain a baseline.
In the embodiment of the present application, before performing temperature programming on the test sensor 1 within a first preset temperature range to obtain a baseline, the method further includes placing the test sensor 1 in the sealed bin 214, and then introducing a shielding gas into the sealed bin 214 to purge the sample to be tested, the test sensor 1, and the gas circuit. Specifically, in a protective gas atmosphere or a vacuum environment, the sample to be tested is pretreated at a certain temperature for a certain time by the sensor driving unit 121 and the heating element of the test sensor 1, so as to clean the surface of the sample to be tested. The baseline is obtained by recording the data of the resonant frequency change of the test sensor 1 during the temperature programming. As an alternative embodiment, the programming of the test sensor 1 to obtain a baseline within a first predetermined temperature range includes: protective gas is introduced into the sealed chamber 214 under a predetermined pressure. The temperature of the test sensor 1 is programmed to rise within a first predetermined temperature range. The resonance frequency of the test sensor 1 during the temperature programming detected by the signal detection unit 122 is acquired. A baseline is obtained from the data of the change in resonant frequency.
S305: the test sensor 1 is programmed to a second predetermined temperature range to obtain a measurement profile.
In the embodiment of the present application, the measurement curve is obtained by recording the data of the resonant frequency change of the test sensor 1 during the temperature programming process. As an alternative embodiment, the test sensor 1 is programmed to warm up within a second preset temperature range to obtain a measurement curve, which includes: reaction gas is introduced into the sealed chamber 214 under a predetermined pressure. And (3) carrying out temperature programming on the test sensor 1 within a second preset temperature range. The resonance frequency of the test sensor 1 detected by the signal detection unit 122 during the temperature programming is acquired. And obtaining a measuring curve according to the change data of the resonance frequency.
In the embodiment of the present application, the reaction gas includes at least adsorbate gas, oxidant gas, reductant gas, sulfur-containing gas, and the like. The reaction between the reaction gas and the sample to be detected at least includes adsorption reaction, oxidation reaction, reduction reaction, sulfurization reaction, etc. And controlling the atmosphere control system 21 to introduce reaction gas into the sealed bin 214 to react with the sample to be tested, and then carrying out temperature programming to obtain corresponding temperature programming test data. The temperature programmed test data is acquired by the low temperature acquisition part 12 of the test sensor 1 from the mass change signal of the sample to be tested in the sample application area, and then output to the analysis test system 22 for processing.
As an alternative, if the reaction gas is an adsorptive gas, the reaction between the reaction gas and the sample to be tested is an adsorptive reaction. Before the temperature of the test sensor 1 is programmed in the second preset temperature range to obtain the measurement curve, the method further includes: the adsorptive gas is introduced into the hermetic container 214 under a predetermined pressure. And heating the sample to be detected to a first preset temperature to enable the surface adsorption degree of the sample to be detected to reach the maximum coverage degree. Protective gas is introduced into the sealed chamber 214 under a predetermined pressure. And heating the sample to be detected to a second preset temperature, and removing the physical adsorption of the adsorbable gas molecules on the surface of the sample to be detected. In this embodiment, the low temperature collection unit 12 of the test sensor 1 collects a mass change signal of the sample to be tested in the sample application area and outputs the signal to the analysis test system 22 for processing, so that the sample adsorption coverage of the sample to be tested can be determined. The sample adsorption coverage of the sample to be tested can be the maximum coverage, namely the adsorption coverage is 1, and also can be other preset degree values. In some embodiments, before the reaction gas is introduced to react with the sample to be tested, the method further comprises removing the physical adsorption of the sample to be tested. Specifically, in a protective gas atmosphere or a vacuum environment, the physical adsorption of the sample to be tested is removed at a certain temperature for a certain time by the sensor driving unit 121 and the heating element of the test sensor 1.
S307: and obtaining a temperature programming analysis curve according to the base line and the measurement curve.
In an embodiment of the present application, the temperature programming analysis data includes temperature programming test data and temperature programming baseline data. And the temperature programmed test data is the mass change data of the substance along with the temperature change when the sample to be tested reacts with the reaction gas in the temperature programmed process. The temperature programming test data can be divided into temperature programming desorption data, temperature programming reduction data, temperature programming oxidation data, temperature programming vulcanization data, temperature programming carbonization data and the like according to different types of temperature programming tests. The temperature programmed baseline data is mass change data of the substance itself as the temperature changes.
As an alternative embodiment, obtaining a temperature-programmed analysis curve from the baseline and the measurement curves comprises: and obtaining a temperature curve of the frequency difference according to the baseline and the measurement curve. And processing the frequency difference temperature curve according to the type of the reaction between the reaction gas and the sample to be detected to obtain a temperature programming analysis curve. Specifically, after the temperature programming test data and the temperature programming baseline data are obtained, the analysis test system 22 processes the two data to obtain a temperature programming analysis curve. The following description will take an example of processing temperature programmed desorption data and temperature programmed baseline data. And subtracting the programmed temperature baseline data from the programmed temperature desorption data to obtain correction data, and then carrying out differential calculation on the correction data to obtain a programmed temperature analysis curve. As an optional implementation manner, the frequency-temperature curve measured in the above step, i.e., temperature programmed desorption data, is subtracted from the frequency-temperature curve measured in the subsequent step, i.e., temperature programmed baseline data, to obtain a frequency difference-temperature curve. And performing first differentiation on the obtained frequency-temperature curve to obtain the TPD curve of the sample.
As an optional implementation manner, the temperature programming method according to the embodiment of the present application includes the following steps:
coating: a sample to be tested is applied to the sample application area of at least one test sensor 1 by means of spraying or the like.
Pretreatment: the test sensor 1 is placed in the sealed chamber 214 and purged with an inert gas to remove the test sample, the test sensor 1 and the adsorbate on the gas path.
Baseline acquisition: and introducing inert gas into the sealed cabin 214 under the set air pressure, and programming the temperature of the test sensor 1 in the set temperature range, and recording the resonance frequency change data of the test sensor 1 in the programming temperature process as a baseline.
Temperature programming: under the set air pressure, inert gas or reaction gas is introduced into the sealed cabin 214, the temperature of the test sensor 1 is programmed in the set temperature range, and meanwhile, the resonance frequency change data of the test sensor 1 in the temperature programming process is recorded as a measurement curve.
Data processing: and deducting the measured baseline from the measured curve obtained in the previous step to obtain a frequency difference-temperature curve, and performing further data processing on the obtained frequency-temperature curve according to the requirements of different temperature programming types to obtain a temperature programming analysis curve of the test sample.
For temperature programmed desorption, prior to temperature programming, pre-adsorption and pre-desorption steps of the reaction gas are also included. Pre-adsorption: at a set pressure, adsorptive gas such as ammonia gas is introduced into the sealed cabin 214, the test sensor 1 is heated to a set temperature and kept unchanged, and adsorption of adsorptive gas molecules on the surface of the test sample is waited to reach the maximum coverage. Pre-desorption: under a set air pressure, inert gas is introduced into the sealed cabin 214, the test sensor 1 is heated to a set temperature and maintained for a period of time, and partial physical adsorption of the adsorbable gas molecules on the surface of the test sample is removed.
The in-situ real-time temperature programming analysis method comprises the steps of using a resonant micro-cantilever beam with a self-heating function as a test sensor 1, coating a sample to be tested on a sample coating area of at least one test sensor 1, placing the test sensor 1 into a sealed cabin 214, introducing reaction gas into the sealed cabin 214 to react with the sample to be tested, carrying out temperature programming on the test sample by using the heating function of the test sensor 1, recording mass change data of reaction gas molecules under the actions of absorption, desorption, oxidation, reduction, chemical reaction and the like generated on a surface interface of the test sample in the temperature raising process by using the weighing function of the test sensor 1, and obtaining a temperature programming analysis curve of the test sample after data processing. The temperature programming analysis test of the sample is realized through the test sensor 1 which is integrated with the heating and weighing functions, the temperature programming analysis process and the device are simplified, the accurate quantitative analysis and the high-flux detection can be realized, the test time is short, and the detection precision is high.
As an alternative embodiment, the in-situ real-time temperature programmed desorption method is specifically described below by taking temperature programmed desorption as an example.
With the atmosphere control system 21 switched to the shielding gas circuit 211, an appropriate temperature is applied in the first end of the integrated heating and temperature measurement test sensor 1 to remove the effect of the original contamination on the beam on the test.
And (4) transferring the sample. Uniformly dispersing a sample in a solvent, wherein the solvent optionally comprises a soluble liquid such as deionized water or ethanol; the dispersed sample solution is accurately dripped into the sample application area of the test sensor 1. The test sensor 1 coated with the sample is placed in the sealed chamber 214 and expanded in a corresponding atmosphere.
The atmosphere control system 21 switches to the reactant gas circuit 212 to connect the capsule 214 to the reactant gas circuit 212. By passing an adsorbate gas, e.g. NH 3 Until the sample adsorption coverage is 1.
The atmosphere control system 21 is switched to the shielding gas circuit 211 to connect the sealed cabin 214 with the shielding gas circuit 211, a temperature-raising program is arranged on the analysis and test system 22, the sample is heated by the high-temperature heating part 11 of the test sensor 1 connected with the analysis and test system 22, and the resonant frequency change of the test sensor 1 is collected in real time by the low-temperature collecting part 12 of the test sensor 1 connected with the analysis and test system 22, so that the adsorption and desorption states of the reaction sample are determined, and the measurement curve of the sample to be measured is obtained. The resonance frequency is decreased when the sample is adsorbed, and the resonance frequency is increased when the sample is desorbed. Fig. 4 is a frequency variation diagram of a sample to be measured being placed in a temperature programmed analyzer for heating according to an embodiment of the present disclosure.
The atmosphere control system 21 is switched to the shielding gas path 211 to connect the sealed cabin 214 with the shielding gas path 211, a temperature-raising program is set on the analysis and test system 22, the sample is heated by the high-temperature heating part 11 of the test sensor 1 connected with the analysis and test system 22, and the resonance frequency change of the test sensor 1 is collected in real time by the low-temperature collecting part 12 of the test sensor 1 connected with the analysis and test system 22 to obtain the baseline of the sample to be tested.
And finally, carrying out data processing on the test. And deducting the baseline from the measurement curve to obtain a frequency difference-temperature curve. And performing first differentiation on the obtained frequency-temperature curve to obtain the TPD curve of the sample.
In the embodiment of the present application, fig. 5 is a TPD graph of putting a to-be-detected sample, which is a ZSM-5 molecular sieve, into a temperature programming analyzer according to the embodiment of the present application, as shown in fig. 5, the to-be-detected sample is a powdered ZSM-5 molecular sieve, the ZSM-5 molecular sieve is dispersed into an ethanol solution, and a liquid is coated on a sample coating area of the test sensor 1. And then carrying out a temperature programmed desorption analysis experiment, and acquiring a resonance frequency change curve of a cantilever beam of the test sensor 1 in the temperature rise process in real time through the analysis test system 22, wherein the protective gas is argon, the reaction gas is ammonia, the temperature rise rate is 40 ℃/min, heating is stopped when the temperature rises to 500 ℃, and the test result is shown in fig. 5. As can be seen from fig. 5, the test results of the temperature programmed analyzer show: the ZSM-5 molecular sieve generates two desorption peaks, and the desorption rate reaches the maximum at 55 ℃ and 370 ℃. This indicates that the test results by the in-situ real-time temperature programmed analysis method described in the present application are consistent with the theoretical calculation results.
In the embodiment of the present application, fig. 6 is a TPD graph obtained by putting a sample to be tested, which is a beta molecular sieve, into a temperature programmed desorption analyzer, as shown in fig. 6, the sample to be tested is the beta molecular sieve, the beta molecular sieve is dispersed in an ethanol solution, and a liquid is coated on a sample coating area of the test sensor 1, and then a temperature programmed desorption analysis experiment is performed. The test results are shown in fig. 6, the beta molecular sieve generates two desorption peaks, and the desorption rate reaches the maximum at 80 ℃ and 330 ℃ respectively. This shows that the test results of the in-situ real-time temperature programmed analysis method described in the present application are consistent with the theoretical calculation results.
In the embodiment of the present application, fig. 7 shows that the sample to be tested is γ -Al according to the present application 2 O 3 TPD curve chart of the desorption analyzer with temperature programming, as shown in FIG. 7, the sample to be measured is gamma-Al 2 O 3 . gamma-Al using the temperature programmed analyzer described in this application 2 O 3 And carrying out temperature programmed desorption analysis, wherein the protective gas is argon, the reaction gas is ammonia, the temperature rise rate is 40 ℃/min, and the temperature is raised to 550 ℃ to stop heating. The test results are shown in FIG. 7, and the test results show that γ -Al 2 O 3 A desorption peak was produced, with the desorption rate reaching a maximum at 65 ℃. The result shows that the test result of the in-situ real-time temperature programming analysis method is consistent with the theoretical calculation result. That is to say, the program heating analyzer that this application provided has better implementability, and the program heating analyzer that this application provided has measurement accuracy height and simple structure's advantage.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (9)
- An in-situ real-time temperature programmed analysis method, comprising:dripping a sample to be tested on a sample coating area of at least one test sensor (1);carrying out temperature programming on the test sensor (1) within a first preset temperature range to obtain a baseline; the baseline is obtained by recording the resonance frequency change data of the test sensor (1) in the temperature programming process;carrying out temperature programming on the test sensor (1) within a second preset temperature range to obtain a measurement curve; the measurement curve is obtained by recording the resonance frequency change data of the test sensor (1) in the temperature programming process;and obtaining a temperature programming analysis curve according to the base line and the measurement curve.
- The in-situ real-time temperature-programmed analytical method of claim 1,the test sensor (1) is arranged in a sealed cabin (214) with a sealed cavity structure;the sealed cabin (214) is provided with a gas guide port for conducting the cavity structure, and the gas guide port is used for introducing protective gas or reaction gas into the sealed cabin (214);the protective gas is used for purging the test sensor (1); the reaction gas is used for reacting with the sample to be detected.
- The in-situ real-time temperature-programmed analytical method according to claim 2, wherein the test sensor (1) includes a high-temperature heating section (11) and a low-temperature collection section (12);the high-temperature heating part (11) is provided with a heating element and the sample coating area for loading the test sample; the heating element is used for heating the sample coating area;the low-temperature acquisition part (12) is provided with a sensor driving unit (121) and a signal detection unit (122), and the sensor driving unit (121) is used for driving the test sensor (1) to generate resonant frequency; the signal detection unit (122) is used for detecting the resonance frequency of the test sensor (1).
- The in-situ real-time temperature programmed analysis method according to claim 3, wherein the reaction of the reaction gas with the sample to be measured at least comprises an adsorption reaction, an oxidation reaction, a reduction reaction, and a sulfidation reaction.
- The in-situ real-time temperature programmed analytical method of claim 4, wherein the programming the test sensor (1) within a first preset temperature range to obtain a baseline comprises:introducing the protective gas into the sealed bin (214) under a preset pressure;carrying out temperature programming on the test sensor (1) within the first preset temperature range;acquiring the resonant frequency of the test sensor (1) detected by the signal detection unit (122) in the temperature programming process;the baseline is obtained from data on changes in the resonant frequency.
- The in-situ real-time temperature-programmed analytical method according to claim 5, wherein said programming the test sensor (1) within a second preset temperature range to obtain a measurement profile comprises:introducing the reaction gas into the sealed bin (214) under a preset pressure;carrying out temperature programming on the test sensor (1) within the second preset temperature range;acquiring the resonant frequency of the test sensor (1) detected by the signal detection unit (122) in the temperature programming process;and obtaining the measuring curve according to the change data of the resonant frequency.
- The in-situ real-time temperature programmed analysis method of claim 6, wherein the deriving a temperature programmed analysis curve from the baseline and the measurement curve comprises:obtaining a frequency difference temperature curve according to the baseline and the measurement curve;and processing the frequency difference temperature curve according to the type of the reaction between the reaction gas and the sample to be detected to obtain the temperature programming analysis curve.
- The in-situ real-time temperature-programmed analytical method of claim 2, wherein prior to programming the test sensor (1) within a first predetermined temperature range to obtain a baseline, further comprising:placing the test sensor (1) within the sealed bin (214);and introducing the protective gas into the sealed cabin (214) to purge the sample to be tested, the test sensor (1) and the gas circuit.
- The in-situ real-time temperature programmed analysis method according to claim 4, wherein during the temperature programmed desorption test according to the in-situ real-time temperature programmed analysis method, the reaction gas is an adsorptive gas, and the reaction between the reaction gas and the sample to be tested is an adsorption reaction; before the temperature programming is carried out on the test sensor (1) in a second preset temperature range to obtain a measurement curve, the method further comprises the following steps:introducing the adsorptive gas into the sealed bin (214) under a preset air pressure;heating the sample to be detected to a first preset temperature to enable the surface adsorption degree of the sample to be detected to reach the maximum coverage degree;and heating the sample to be detected to a second preset temperature, and removing the physical adsorption of the adsorptive gas molecules on the surface of the sample to be detected.
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| CN101477029B (en) * | 2009-01-16 | 2011-06-08 | 中国科学院上海微系统与信息技术研究所 | Surface stress sensitization method for improving resonance type ultra-thin cantilever beam transducer sensitivity |
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