CN1490620A - Catalyst surface-characteristic comprehensive measuring device and application thereof - Google Patents
Catalyst surface-characteristic comprehensive measuring device and application thereof Download PDFInfo
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Abstract
The instrument comprises carrier gas inlet, working gas inlet, other gas inlet, gas flow meter, mixer, the first and the second four-way valve, the first and the second six-way valve, saturator, heating furnace with programmed control temperature, sample tube with internal-inserted thermocouple, heat conductive pool, cold-trap, chromatographic column, hydrogen flame detector sampling and displaying of computer and spectrogram printing. The instrument with above devices can apply techniques of programmed temperature for reduction de-addendum, surface reaction, oxidation and decomposition as well as H2-O2 titration to carry on surface performance test for catalyst and to obtain spectrogram for each abovesaid performance of the catalyst.
Description
Technical Field
The invention relates to a testing instrument, in particular to a comprehensive tester for surface properties of a catalyst and application thereof.
Technical Field
In heterogeneous catalytic research, great difficulties are encountered in explaining the catalytic activity and mechanism due to the complexity of the composition, structure and reaction kinetic system associated with the catalyst itself, thus hindering the selection of the optimal catalyst for a particular chemical process.
Although there are many characterization methods for catalysts at present, such as X-ray powder diffraction, electron microscopy, photoelectron spectroscopy, infrared spectroscopy, thermal analysis, etc., none of these techniques can give the properties of the catalyst under actual working conditions.
In addition to the respective limitations in terms of instruments and theories, the general physical methods, for example in combination with the adsorption process, can often deeply address the problems of the adsorption performance, surface structure, surface properties and kinetics of the catalyst. Therefore, chemisorption (desorption) has been widely used in the research of various types of catalysts as a main and effective means.
The Temperature Programmed Desorption (TPD) technology, as an advance of the Flash Desorption (FD) technology, was first proposed by y.amonomiya and r.j.cvetanovic in 1963, and then people rapidly expanded and improved the application and theoretical analysis of this technology in scientific research practice.
Mcnicol, Hirosh Miura and the like develop a Temperature Programmed Reduction (TPR) technology on the basis of a temperature programmed desorption technology.
Mccarty and a brenner, et al, developed Temperature Programmed Surface Reaction (TPSR) and Temperature Programmed Decomposition (TPDE) technologies, respectively.
Numerous researchers in the future developed Temperature Programmed Oxidation (TPO) technology, H2-O2Titration technique. The methods provide a plurality of technical means with high efficiency, high sensitivity and quickness for deeply researching the catalyst and revealing the nature of the catalytic action.
The defects and problems to be solved urgently exist in the current instruments and test methods:
the testing technology is realized on a self-made instrument with single function and complex operation. To date, there is no comprehensive instrument and testing method implemented on the instrument that integrates the above-described technologies for characterizing catalysts and catalytic reactions. The traditional test method is time-consuming, labor-consuming and large in error, and particularly, quantitative analysis is difficult.
Disclosure of Invention
The invention discloses a comprehensive tester for the surface property of a catalyst and a method for testing the surface property of the catalyst by adopting the tester, which aim to overcome the defects in the prior art and meet the requirements of scientific research and engineering design.
The technical scheme of the invention is as follows:
the apparatus of the invention comprises at least: the system comprises a carrier gas source inlet, a working gas source inlet, other gas source inlets, a gas flowmeter, a mixer, a first four-way valve, a second four-way valve, a first six-way valve, a second six-way valve, a saturator, a program temperature control heating furnace, asample tube with a thermocouple inserted therein, a thermal conductivity cell detector (thermal conductivity cell for short), a cold trap, a chromatographic column, a hydrogen flame detector, a computer sampling and displaying system and a spectrogram printing system.
The inlet of the carrier gas source is communicated with a mixer through a pipeline by a gas flowmeter, and the mixer is communicated with a first interface of a first four-way valve;
the inlet of the working gas source is communicated with the mixer and a first interface of the first four-way valve through a gas flowmeter; or the gas flow meter is directly communicated with the fourth interface of the first four-way valve, and the third interface of the first four-way valve is communicated with the third interface of the second four-way valve.
The other gas source inlets are communicated with a second interface of the second four-way valve through a gas flow meter, and a first interface of the second four-way valve is a vent;
a second interface of the first four-way valve is communicated with a gas inlet of the thermal conductivity cell reference arm, and a gas outlet of the thermal conductivity cell reference arm is communicated with a third interface of the first six-way valve;
a fourth interface of the second four-way valve is communicated with a first interface of the first six-way valve; the second interface of the first six-way valve is communicated with the fifth interface through a quantitative pipe, the sixth interface is communicated with the gas inlet of the saturator, and the fourth interface is communicated with the second interface of the second six-way valve through a first cold trap;
the first interface of the second six-way valve is communicated with the gas inlet of the sample tube, the third interface is connected with the second cold trap, the other end of the second cold trap is communicated with the gas inlet of the measuring arm of the thermal conductivity cell or is communicated with the hydrogen flame detector through the chromatographic column, the fourth interface is communicated with the gas outlet of the sample tube, the fifth interface is a vent, and the sixth interface is communicated with the gas outlet of the saturator.
The sample tube is arranged in the heating furnace.
The thermal conductivity cell (or hydrogen flame) detector and the electric signal output end of the thermocouple are connected with a computer sampling, spectrogram displaying and printing system by leads.
The instrument with the structure can adopt Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD) and H2-O2TitrationThe surface performance of the catalyst is tested by technologies such as (HOT), Temperature Programmed Surface Reaction (TPSR), Temperature Programmed Oxidation (TPO) or Temperature Programmed Decomposition (TPDE), and the above various performance spectrograms of the catalyst can be obtained.
The apparatus of the invention has simple structure and convenient operation, can integrate various testing technologies, can actually measure the properties of the catalyst under the actual working condition, and has the advantages of time saving, labor saving and small error.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
FIG. 2 shows TPR spectrum of Cu-containing hydrotalcite-like catalyst.
FIG. 3 is a TPR spectrum of CuO.
FIG. 4 shows H of iron trioxide catalyst2Desorption of the TPD spectrum.
FIG. 5 shows NH of a molybdenum-containing molecular sieve catalyst3Desorption of the TPD spectrum.
FIG. 6 shows a palladium catalyst (Pd/Al)2O3) HOT spectrum of (3).
FIG. 7 is a TPSR spectrum of Cu-containing hydrotalcite-like catalyst.
FIG. 8 is a TPO spectrum of a Zn-containing catalyst.
Fig. 9 is a TPDE spectrum of CuZnAlCe hydrotalcite-like catalyst.
Detailed Description
Referring to fig. 1, the apparatus of the present invention comprises:
the apparatus of the invention comprises at least: a carrier gas source inlet 18, a working gas source inlet 19, other gas source inlets 20, a gas flow meter 4, a mixer 5, a first four-way valve 6, a second four-way valve 7, a first six-way valve 8, a second six-way valve 11, a saturator 10, a program temperature control heating furnace 14, a sample tube 13 with a thermocouple inserted therein, a heat conducting cell 16, cold traps 12 and 14, a chromatographic column and hydrogen flame detector 17, a computer sampling and displaying system and a spectrogram printing system.
The carrier gas source inlet 18 is communicated with the mixer 5 through a pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 3 and a gas flowmeter 4, and the outlet of the mixer 5 is communicated with a first interface 401 of a first four-way valve 6;
the working gas source inlet 19 is communicated with the mixer 5 and a first interface 601 of the first four-way valve 6 through a pressure stabilizing valve 1, a drying pipe 2, a flow stabilizing valve 31 and a gas flow meter 4; or after passing through the pressure stabilizing valve 1, the drying pipe 2, the flow stabilizing valve 32 and the gas flowmeter 4, the gas flow stabilizer is directly communicated with a fourth interface 604 of the first four-way valve 6, and a third interface 603 of the first four-way valve 6 is communicated with a third interface 703 of the second four-way valve 7;
the other gas source inlet 20 is communicated with a second interface 702 of the second four-way valve 7 through a pressure stabilizing valve 1, a drying pipe 2, a flow stabilizing valve 3 and a gas flow meter 4, and a first interface 701 of the second four-way valve 7 is a vent;
the second interface 602 of the first four-way valve 6 is communicated with the gas inlet of the reference arm 1601 of the thermal conductivity cell 16, and the gas outlet of the reference arm 1601 of the thermal conductivity cell 16 is communicated with the third interface 803 of the first six-way valve 8;
a fourth interface 704 of the second four-way valve 7 is communicated with a first interface 801 of the first six-way valve 8; the second port 802 of the first six-way valve 8 is communicated with the fifth port 805 through the dosing pipe 9, the sixth port 806 is communicated with the gas inlet of the saturator 10, and the fourth port 804 is communicated with the second port 1102 of the second six-way valve 11 through the first cold trap 12;
the first port 1101 of the second six-way valve 11 is communicated with the gas inlet of the sample tube 13, the third port 1103 is connected with the second cold trap 15, the other end of the second cold trap 15 is communicated with the gas inlet of the measuring arm 1602 of the thermal conductivity cell 16 or the hydrogen flame detector 17 through the chromatographic column, the fourth port 1104 is communicated with the gas outlet of the sample tube 13, the fifth port 1105is a vent, and the sixth port 1106 is communicated with the gas outlet of the saturator 10.
The sample tube 13 is placed in a heating furnace 14.
The thermal conductivity cell (or hydrogen flame) detector and the electric signal output end of the thermocouple are connected with a computer sampling, spectrogram displaying and printing system by leads.
The basic principle of the method for testing the surface property of the catalyst by adopting the instrument and a Temperature Programmed Reduction (TPR) method is as follows:
TPR means that the catalyst is reduced during the temperature programming. It can provide the information of the interaction between metal oxides or between the metal oxides and the carrier in the reduction process of the supported metal catalyst. A pure metal oxide has a specific reduction temperature that can be used to characterize the properties of the oxide. If another oxide is introduced into the oxide, the two oxides are mixed together, and if the reduction temperature of each oxide is kept unchanged during the TPR process, the two oxides do not act with each other; on the other hand, if the two oxides undergo a solid-phase reaction and the properties of the oxides change, the original reduction temperature also changes. This change can be observed by the TPR method.
The TPR spectrogram can effectively see the hydrogen consumption of the supported oxide during reduction and the difficulty degree during reduction, and provide information such as interaction between the metal oxide and the carrier, the metal dispersibility on the surface of the carrier and the like. In addition, upon thermal decomposition of the two-component metal catalyst in the preparation of its oxide precursor, if the two oxides interact (or partially interact) with each other, the reduction property of the active component oxide will change, which can be observed by the TPR method. The basic equation is as follows:
2lnTm-lnβ+ln[H2]m＝ER/RTm+ln(FR/AR)
in the formula (H)2]m-hydrogen concentration at which the reduction rate reaches a maximum;
ER-reduction activation energy;
β - -heating rate;
a-denotes a pro-factor;
Tm-temperature at peak maximum;
r- -gas constant.
(2lnTm-lnβ+ln[H2]m) For 1/TmPlotting as a straight line, and determining E from the slope of the lineR. Changes in hydrogen concentration and flow rate cause TmThe variation in (c) was well consistent with the results obtained by the equation. This method is extremely sensitive, and the reduction can be detected only by consuming 1. mu. mol of hydrogen.
The method comprises the following steps:
(1) taking 0.2-0.3 g of a 20-80-mesh catalyst sample, putting the catalyst sample into a sample tube 13, adding a small amount of treated quartz sand at two ends of the sample tube, and loosely plugging a small amount of glass wool at a port;
(2) and (4) sample pretreatment. With He (or N)2) The first four-way valve 6 is switched to carry the gas, so that the first interface 601 and the second interface 602 of the first four-way valve 6 are in a communication position; switching the first six-way valve 8 to enable the third port 803 and the fourth port 804 of the first six-way valve 8 to be in a communication position; switching the second six-way valve 11 so that the first port 1101 and the secondport 1102 of the second six-way valve 11 are in a communication position, and the third port 1103 and the fourth port 1104 are in a communication position (TPR operation, not involving the second four-way valve 7);
at the moment, He enters from a carrier gas source inlet 18, flows into a first interface 601 of a first four-way valve 6 after passing through a pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 3, a gas flowmeter 4 and a mixer 5, flows out from a second interface 602, then flows into a gas inlet of a reference arm 1601 of a thermal conductivity cell 16, and flows out from an outlet; then flows into the third port 803 of the first six-way valve 8 and flows out from the fourth port 804; after passing through the first cold trap 12, the sample flows to the second port 1102 of the second six-way valve 11 and flows out from the first port 1101, and then flows into the gas inlet of the sample tube 13 and flows out from the outlet thereof; then flows into the fourth port 1104 of the second six-way valve 11 and flows out from the third port 1103; then flows through the second cold trap 15, flows into the gas inlet of the measuring arm 1602 of the thermal conductivity cell 16 and flows out of the outlet thereof to be discharged.
Enabling the He to pass through the sample tube 13 at the flow rate of 30-90 ml/min, simultaneously heating the heating furnace 14 at the speed of 3-20 ℃/min, heating the temperature from room temperature to 100-800 ℃, keeping the temperature for 1-3 hours, then introducing the He and reducing the temperature to room temperature, and closing a He source;
(3) with H2The reducing gas enters from the working gas source inlet 19 and flows through the pressure stabilizing valve 1, the drying tube 2, the flow stabilizing valve 31, the gas flowmeter 4 and the mixer 5. Adjusting H2Flow rate, then opening He gas source, H2mixing-He ina mixer 5, controlling the total flow rate at 30-90 ml/min to obtain 5-10% H2-He mixed gas;
at the moment, the positions of the four-way valve and the six-way valve are kept unchanged, namely the flowing path of the mixed gas is completely the same as the flowing path of the gas flow during sample pretreatment.
And (3) opening the detector and the computer sampling system, starting a temperature controller program after the baseline is stable, and heating the heating furnace 14 at the speed of 5-25 ℃/min to 400-800 ℃. A temperature programmed surface reduction was started.
(4) The voltage signals output by the thermocouple and the thermal conductivity cell 16 in the sample tube 13 are input into a computer for display and printing after A/D (analog/digital) conversion, and then the TPR spectrogram of the catalyst can be obtained.
The basic principle of testing the surface property of the catalyst by a Temperature Programmed Desorption (TPD) method by adopting the instrument is as follows:
the TPD technique is a flow method, and is suitable for basic research of application of a practical catalyst, and although advanced experimental instruments and research methods, such as photoelectron spectroscopy (XPS), Auger Electron Spectroscopy (AES), Low Energy Electron Diffraction (LEED), ion scattering (ISS), paramagnetic resonance (ESR), etc., are continuously present to research surface properties and active site sequences of the catalyst, it is very complicated. It can be said that the TPD technique is superior and there is considerable scope for development.
For a uniform surface, the basic equation for thermal desorption without reabsorption occurs:
2logTm-logβ＝Ed/2.303RTm+logEd/ARnθm n-1
the first-order desorption process can be simplified as follows:
2logTm-logβ＝Ed/2.303RTm+logEd/AR
in the formula
β - -rate of temperature rise;
Tm-temperature at which peak occurs;
Edactivation energy at desorption;
a-denotes a pro-factor;
n-desorption stage number;
θm------T＝Tmcoverage in time;
r- -gas constant.
Varying the ramp rate β yields the corresponding Tm. With (2 logT)mLog β) vs 1/TmDrawing a straight line, and determining E from the slope and intercept of the straight linedAnd A, from EdAnd A is the case of the energy distribution of the active center. Further according to Arrhenius equation, the desorption rate constant K can be obtaineddTemperature dependence of (a). The method comprises the following steps:
(1) loading the catalyst into a sample tube 13, adding a small amount of treated quartz sand at two ends, and loosely plugging a small amount of glass wool at the end;
(2) activating or surface cleaning the catalyst sample;
(3) adsorption of adsorbates by catalysts
I operation with adsorbate in liquid state
He gas is taken as other gas, and is introduced from the inlet 20 of other gas sources. Switching the second four-way valve 7 to place the second port 702 and the fourth port 704 of the second four-way valve 7 in a communicating position; switching the first six-way valve 8 to place the first interface 801 and the second interface 802 of the first six-way valve 8 in a communication position, and placing the fifth interface 805 and the sixth interface 806 in a communication position; switching the second six-way valve 11 to enable the first port 1101 and the sixth port 1106 of the second six-way valve 11 to be in a communication position, and enabling the fourth port 1104 and the fifth port 1105 to be in a communication position (adsorption operation of the catalyst on the adsorbate does not involve the first four-way valve);
at the moment, He gas is introduced from the inlet 20 of other gas sources, flows into the second interface 702 of the second four-way valve 7 through the pressure stabilizing valve 1, the drying tube 2, the flow stabilizing valve 3 and the gas flowmeter 4, and flows out of the fourth interface 704; then flows into the first interface 801 of the first six-way valve 8 and flows out from the second interface 802, and then flows into the fifth interface 805 of the six-way valve 8 through the quantitative pipe 9 and flows out from the sixth interface 806; then flows into a gas inlet of a liquid adsorbate saturator 10 with the volume of 1/5-1/3 and carries out adsorbate vapor from an outlet; the mixed gas (He and adsorbate vapor) flows in from the sixth port 1106 of the second six-way valve 11 and flows out from the first port 1101, then flows into the gas inlet of the sample tube 13, the sample in the tube is subjected to flow adsorption, and the residual gas flows from the gas outlet of the sample tube 13 to the fourth port 1104 of the second six-way valve 11 and is vented from the fifth port 1105.
Enabling the He gas to pass through a saturator at the flow speed of 10-60 ml/min, bringing the adsorbate vapor into the sample tube, and adsorbing for a certain time.
II operation with adsorbate in gaseous state
The He gas is directly replaced by the adsorbate gas (no adsorbate is required to be arranged in the saturator), and the gas flow rate and the gas flow are the same as those of the He gas.
Purging before III TPD
He gas is taken as carrier gas and enters from the inlet 18 of the carrier gas source, and the valve is switched, so that the first interface 601 and the second interface 602 of the first four-way valve 6 are in a communication position; the third port 803 and the fourth port 804 of the first six-way valve 8 are in a communicating position; the first port 1101 of the second six-way valve 11 is in a communication position with the second port 1102, and the coupling between the outlet of the sample tube 13 and the fourth port 1104 of the second six-way valve 11 is disconnected.
When in use, He gas enters from a carrier gas source inlet 18, flows into a first interface 601 of a first four-way valve 6 after passing through a pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 3, a gas flowmeter 4 and a mixer 5, flows out from a second interface 602, then flows into a reference arm gas inlet 1601 of a thermal conductivity cell 16, and flows out from an outlet; then flows into the third port 803 of the first six-way valve 8 and flows out from the fourth port 804; after passing through the first cold trap 12, the sample flows to the second port 1102 of the second six-way valve 11 and flows out from the first port 1101, and then flows into the gas inlet of the sample tube 13 and flows out directly from the outlet thereof to be discharged.
Blowing the pipeline and the sample for 1-3 hours at room temperature by He gas according to the gas path, wherein the flow rate of the He is 10-60 ml/min, and connecting the outlet of the sample tube 13 with the fourth interface 1104 of the second six-way valve 11 after blowing is finished;
at the moment, He gas enters from a carrier gas source inlet 18, flows into a first connector 601 of a first four-way valve 6 after passing through a pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 3, a gas flowmeter 4 and a mixer 5, flows out from a second connector 602, then flows into a gas inlet of a reference arm 1601 of a thermal conductivity cell 16, and flows out from an outlet; then flows into the third port 803 of the first six-way valve 8 and flows out from the fourth port 804; after passing through the first cold trap 12, the sample flows to the second port 1102 of the second six-way valve 11 and flows out from the first port 1101, and then flows into the gas inlet of the sample tube 13 and flows out from the gas outlet; then flows into the fourth port 1104 of the second six-way valve 11 and flows out from the third port 1103; after flowing through the second cold trap 15, the gas flows into the gas inlet of the measuring arm 1602 of the thermal conductivity cell 16 and flows out of the gas outlet to be discharged.
The purging operation before temperature programmed desorption is the same whether the adsorbate is liquid or gas.
(4) And opening the detector and the computer sampling system, starting a program of the heating furnace temperature control instrument after the baseline is stable, heating the heating furnace 14 at the speed of 5-25 ℃/min, heating the temperature from room temperature to 400-800 ℃, and starting temperature programmed desorption.
(5) The voltage signals output by the thermocouple and the thermal conductivity cell 16 in the sample tube 13 are input into a computer for displaying and printing after A/D (analog/digital) conversion, and then the TPD spectrogram of the catalyst can be obtained.
Using the above instrument through H2-O2The titration technique(HOT) method tests the surface properties of the catalyst, and the basic principle is that:
if the adsorbate is chemisorbed as a monolayer, there is a simple relationship between the number of saturated adsorbed gas molecules and the number of metal atoms on the catalyst surface. Therefore, the number of atoms of the surface metal can be directly determined by measuring the chemisorption amount of the adsorbate molecules on the surface of the adsorbent, and the dispersion state of the surface metal can be determined.
Given a known cross-sectional area of one metal atom, the specific surface of the metal can be calculated. If the atomic model of the surface metal is also known, the average grain size of the metal can also be calculated.
The method comprises the following steps:
0.2-1.0 g of 20-80 meshes of dry catalyst is taken and put into a sample tube 13, a small amount of treated quartz sand is added at two ends, and a small amount of glass wool is loosely plugged at the end.
(1) With H2The gas is working gas, the flow valve 31 is closed, and the flow stabilizing valve 32 is in an open state; switching valves to enable the first interface 601 and the second interface 602 of the first four-way valve 6 to be in a communication position, and enable the third interface 603 and the fourth interface 604 to be in a communication position; the third port 703 and the fourth port 704 of the second four-way valve 7 are in a communicating position; the first port 801 and the second port 802 of the first six-way valve 8 are in a communicating position, and the fifth port 805 and the sixth port 806 are in a communicating position; the first 1101 and sixth 1106 ports of the second six-way valve 11 are in a communicating position,the fourth port 1104 and the fifth port 1105 are in a communicating position.
At this time, H2Gas is introduced from a working gas source inlet 19 and passes through a pressure stabilizing valve 1, a drying tube 2 and a flow stabilizing valve32. After the gas flow meter 4, the gas flows in from the fourth port 604 of the first four-way valve 6 and flows out from the third port 603; then flows into a third interface 703 of the second four-way valve 7 and flows out from a fourth interface 704; then flows into the first port 803 of the first six-way valve 8 and flows out from the second port 802, and then flows into the fifth port 805 of the six-way valve 8 through the quantitative pipe 9 and flows out from the sixth port 806; then flows into the air inlet of the saturator 10 and flows out from the air outlet; then flows into the sixth port 1106 of the second six-way valve 11 and flows out of the first port 1101; then flows into the gas inlet of the sample tube 13, and flows from the gas outlet of the sample tube 13 to the fourth port 1104 of the second six-way valve 11 and is emptied from the fifth port 1105.
Make H2Gas passes through the sample tube 13 at a flow rate of 10-30 ml/min, the heating rate of the heating furnace 14 is 5-20 ℃/min, the gas is heated from room temperature to a certain temperature between 200-700 ℃ and then reduced at a constant temperature for 1-4 hours, and then the gas is cooled to a certain temperature between room temperature and 400 ℃ and then is kept at the constant temperature, and the temperature is kept constant in the subsequent experimental processes of 'chemical adsorption of oxygen' and 'hydrogen titration'. Mixing He (or N)2) Gas is taken as carrier gas and enters from a carrier gas source inlet 18, and passes through the sample tube 13 at the flow rate of 10-60 ml/min, and H is closed2And (4) qi. Introducing He (or N)2) The purpose of the gas is to remove residual H in the pipeline2Gas, He (or N)2) And (5) blowingfor 0.5-2 hours.
He (or N)2) When the gas purging is performed, the first connector 601 and the third connector 603 of the first four-way valve 6 are in a communication position; the third port 703 and the fourth port 704 of the second four-way valve 7 are in a communicating position; the first port 801 and the second port 802 of the first six-way valve 8 are in a communicating position, and the fifth port 805 and the sixth port 806 are in a communicating position; the first and sixth ports 1101, 1106 of the second six-way valve 11 are in a communicating position and the fourth port 1104 and the fifth port 1105 are in a communicating position.
When it is in this state, He (or N)2) Gas enters from a carrier gas source inlet 18, flows through a corresponding pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 3, a gas flow meter 4 and a mixer 5, flows into a first connector 601 of a first four-way valve 6 and flows out of a third connector 603; then flows into the firstA third interface 703 of the two-way valve 7 and a fourth interface 704; then flows into the first port 801 of the first six-way valve 8 and flows out from the second port 802, and then flows into the fifth port 805 of the six-way valve 8 through the quantitative pipe 9 and flows out from the sixth port 806; then flows into the air inlet of the saturator 10 and flows out from the air outlet; then flows into the sixth port 1106 of the second six-way valve 11 and flows out of the first port 1101; then flows into the gas inlet of the sample tube 13, and flows from the gas outlet of the sample tube 11 to the fourth port 1104 of the second six-way valve 11 and is vented from the fifth port 1105.
He (or N)2) At the end of the gas purge, the valves are switched to place the first and second ports 601, 602 of the first four-way valve 6 in a communicating position, the third and fourth ports 703, 704 ofthe second four-way valve 7 in a communicating position, and the first sixth portThe third and fourth ports 803, 804 of the through valve 8 are in a communicating position, the first and second ports 1101, 1102 of the second six-way valve 11 are in a communicating position, the third port 1103 and the fourth port 1104 are in a communicating position, the fifth port 1105 and the sixth port 1106 are in a communicating position, and then the thermal conductivity cell 16 is opened to the computer sampling system.
He (or N) after purging2) Gas still enters from a carrier gas source inlet 18, flows into a first connector 601 of a first four-way valve 6 and flows out of a second connector 602 after passing through a pressure stabilizing valve 1, a drying pipe 2, a flow stabilizing valve 3, a gas flow meter 4 and a mixer 5; then flows in from the gas inlet of the reference arm 1601 of the thermal conductivity cell 16 and flows out from the gas outlet; then flows into the third port 803 of the first six-way valve 8 and flows out from the fourth port 804; after passing through the first cold trap 12, the sample flows to the second port 1102 of the second six-way valve 11 and flows out from the first port 1101, and then flows into the gas inlet of the sample tube 13 and flows out from the outlet thereof; then flows into the fourth port 1104 of the second six-way valve 11 and flows out from the third port 1103; then flows through the second cold trap 15, flows into the gas inlet of the measuring arm 1602 of the thermal conductivity cell 16 and flows out of the outlet to be discharged.
(2) Chemical adsorption of oxygen
With O2The air is other working air, only the second four-way valve 7 is switched to ensure that the second four-way valve 7 is the first oneThe second port 702 and the fourth port 704 are in a communicating position, and the positions of the remaining valves areall kept constant, O2The air flow rate is 10-60 ml/min.
At this time, O2The air enters from the other air source inlets 20, flows through the corresponding pressure stabilizing valves 1, the drying pipes 2, the flow stabilizing valve 3 and the air flow meter 4, flows into the second interface 702 of the second four-way valve 7 and flows out from the fourth interface 704; then flows into the first port 801 of the first six-way valve 8 and flows out from the second port 802, and then flows into the fifth port 805 of the six-way valve 8 through the quantitative pipe 9 and flows out from the sixth port 806; then flows into the air inlet of the saturator 10 and flows out from the air outlet; and then to the sixth port 1106 of the second six-way valve 11 and to be vented from the fifth port 1105.
It can be seen that there are two paths of gas (He gas and O) in the instrument at the same time2Gas) flows along the respective gas paths at a constant rate while being incoherent.
Then, the positions of the remaining valves are kept unchanged, and only the first six-way valve 8 is switched. The first port 801 and the sixth port 806 of the first six-way valve 8 are brought into a communicating position, the second port 802 and the third port 803 are brought into a communicating position, and the fourth port 804 and the fifth port 805 are brought into a communicating position.
At this time O2The gas flows out at the fourth port 704 of the second four-way valve 7, flows into the first port 801 of the first six-way valve 8 and flows out at the sixth port 806 (no longer flows through the dosing pipe 9), and then flows into the gas inlet of the saturator 10 and flows out at the gas outlet; and then to the sixth port 1106 of the second six-way valve 11 and to be vented from the fifth port 1105.
The He gas flows out from the gas outlet of the reference arm 1601 of the heat conduction cell 16, flows into the third interface 803 of the first six-way valve 8 and flows out from the second interface 802, then flows into the quantitative pipe 9, and then flows into the O in the quantitative pipe 92The air is brought into the fifth interface 805 of the first six-way valve 8 and flows out of the fourth interface 804; then flows to a second six-way pipe after passing through a first cold trap 12O in the dosing tube 9 at the second port 1102 of the valve 11 and out of the first port 11012The gas flows into the sample tube 13 along with the He gas, and chemical adsorption occurs on the surface of the sample to consume part of O2Qi, the rest is derived fromThe sample tube 13 flows out from the outlet; then flows into the fourth port 1104 of the second six-way valve 11 and flows out from the third port 1103; then flows through the second cold trap 15, flows into the gas inlet of the measuring arm 1602 of the thermal conductivity cell 16 and flows out of the outlet to be discharged. It is apparent that the composition of the gas flowing through the reference arm 1601 of the thermal conductivity cell 16 is different from the composition of the gas flowing through the measurement arm 1602 of the thermal conductivity cell 16, resulting in a change in the voltage signal output by the thermal conductivity cell 16.
After 2-10 seconds, the first six-way valve 8 is switched back to the original position, even if the first interface 801 and the second interface 802 of the first six-way valve 8 are in the communication position, the third interface 803 and the fourth interface 804 are in the communication position, and the fifth interface 805 and the sixth interface 806 are in the communication position. At this time, He gas and O2The air flows along the respective air paths at a constant speed without mutual interference.
One-time switching back and forth of the first six-way valve 8 is called pulse feeding O2Once (will quantify O in the tube2Pulsed with He into the sample tube). As the number of pulse sampling increases, O2Saturated chemisorption was gradually reached on the sample surface. Pulse into O2Multiple times, measuring O in the effluent gas after each pulse2Until the sample in the sample tube is no longer in contact with O2Until effect (time O)2The spectral peak area of (a) will remain unchanged). The time interval of the two pulses is 2-10 min.
(3) Hydrogen titration
With H2Is working gas, H2The air flow rate is 10-60 ml/min. Switching the valves so that the third and fourth ports 603, 604 of the first four-way valve 6 are in a communicating position and the first and second ports 601, 602 are in a communicating position; the third and fourth ports 703, 704 of the second four-way valve 7 are in a communicating position; the first and second ports 801, 802 of the first six-way valve 8 are in a communicating position, the third and fourth ports 803, 804 are in a communicating position, and the fifth and sixth ports 805, 806 are in a communicating position; the first and second ports 1101, 1102 of the second six-way valve 11 are in a communicating position, the third and fourth ports 1103, 1104 are in a communicating position, and the fifth and sixth ports 1105, 1106 are in a communicating position.
When that is, H2The air enters from the inlet 19 of the working air source, flows through the corresponding pressure stabilizing valve 1, the drying tube 2, the flow stabilizing valve 32 (the flow stabilizing valve 31 is in a closed state) and the gas flow meter 4, flows into the fourth interface 604 of the first four-way valve 6 and flows out from the third interface 603; then flows into a third interface703 of the second four-way valve 7 and flows out from a fourth interface 704; then flows into the first port 801 of the first six-way valve 8 and flows out from the second port 802, and then flows into the fifth port 805 of the six-way valve 8 through the quantitative pipe 9 and flows out from the sixth port 806; then flows into the air inlet of the saturator 10 and flows out from the air outlet; and then to the sixth port 1106 of the second six-way valve 11 and out of the fifth port 1105 to be vented.
He gas still enters from the carrier gas source inlet 18, and the flow rate and the flow path of the He gas are unchanged.
At this time, two paths of gases (He gas and H gas) are simultaneously arranged in the instrument2Gas) flows along the respective gas paths at a constant rate while being incoherent.
Then, pulse into H2(e.g. pulse into O)2Operated in the same way), i.e. H2The gas is carried into the sample tube 13 by the carrier gas He in a pulse form, and is chemically adsorbed with O on the surface of the sample2Reacting, weighing H2And (4) titrating. The time interval of the two pulses is 2-10 min. Measuring H in the effluent gas after each pulse2Spectral peak area of (a); until in the effluent gas H2Until the peak area of (a) is unchanged.
The voltage signal changes output by the thermocouple and the thermal conductivity cell 16 in the sample tube 13 are respectively input into a computer for displaying and printing after A/D (analog/digital) conversion, and then an HOT spectrogram can be obtained.
(4) By each pulse into H2The dispersion degree, specific surface and grain size of the sample can be calculated according to the following formulas:
in the formula: a. theiIth pass H2Area of peak at time
AsStandard Peak area (Peak area constant at the end of titration)
VsPulse sample size (volumetric tube, ml)
VaH2Adsorption amount (ml)
II is to mix VaThe volume is converted to the standard state by the following formula
In the formula: t is room temperature (K); p is atmospheric pressure (mmHg)
III degree of Dispersion i.e. number of chemisorbed oxygen atoms [ O]]Or the number of surface active metal atoms [ M]*]With total number of metal atoms [ M]on the catalyst]The ratio of. Oxygen adsorption and hydrogen titration were performed as follows:
i.e. chemisorption, one Pt atom adsorbs one oxygen atom;
in titration, one oxygen atom chemically adsorbed on Pt consumes two hydrogen atoms, reacts to generate water,since Pt atoms adsorb one hydrogen atom after deoxidation on the carrier, the amount of hydrogen used for titration of the oxygen atom adsorbed on Pt is only 2/3 of the total hydrogen consumption, i.e. the number of Pt atoms on the surface (Pt)*) To consume H22/3 in number of molecules. The degree of dispersion was therefore calculated as follows:
in the formula: m is the atomic weight of the supported metal;w is the catalyst mass (g); p% is the weight percentage of the load metal in the catalyst; va 0(H2) In the standard state H2Adsorption amount (ml) of (1).
Specific surface area of IV
In the formula: n is a radical ofAIs Afugardro constant; σ is the cross-sectional area (cm) of the metal atom2)。
The V grain size is also called the average grain size. The calculation is based on the Hughes []model. The basic assumptions of Hughes are: all Pt grains are ideally of the same size, cubic with one face in contact with the support and the remaining five faces exposed, with one side length d of the cubic being related to the surface area S, volume V or density ρ, i.e.:
in the formula: s is specific surface area (cm)2(iv)/g); v is specific volume (cm)3(iv)/g); ρ is the density (g/cm) of Pt3)。
The basic principle of testing the surface property of the catalyst by a Temperature Programmed Surface Reaction (TPSR) method by adopting the instrument is as follows:
in the temperature programmed process, surface reaction and desorption occur simultaneously, which is called temperature programmed surface reaction. There are generally two approaches to this technique: firstly, adsorbing and reacting a pretreated catalyst under reaction conditions, and then, carrying out temperature programming from room temperature to a certain set temperature so as to desorb various surface species adsorbed on the surface of the catalyst while reacting; the other is that the carrier gas (or a component in the carrier gas) used for desorption is a reactant, and in the temperature programming process, the carrier gas (or a component in the carrier gas) reacts on the surface of the catalyst to form a certain adsorbed species which reacts and desorbs at the same time.
Considering ideal adsorption condition, the desorbed substance is not adsorbed any more, the molecules of the adsorbed species are adsorbed on the uniform catalyst surface, and the surface reaction rate gammaROr desorption rate γDCan be represented by the following general formula
γi＝-dθ/dt＝Kiθn＝Aiθnexp[-(Ei/RT)](1)
Ki: a reaction or desorption rate constant; θ: surface coverage; n: the number of reaction or desorption stages; ei: reaction or desorption activation energy; t: time; t: absolute temperature. Assuming here that the catalyst surface is homogeneous, i.e.iAs a quantity independent of theta.
The temperature is continuously changed during temperature programming, which conforms to the following formula
T＝To+ β t or dT/dT ═ β (2)
β heating rate, To: temperature at which reaction and desorption begin.
When TPSR is carried out, the reaction or desorption rate has a maximum with increasing temperature. The carrier gas brings the desorbed substances out of the catalyst, and a desorption peak proportional to the concentration of the desorbed substances can be obtained through the detection device. The peak area represents the size of the desorbed amount, TmThe peak temperature at which the desorption rate reached a maximum.
When the desorption peak has a maximum value, d γ/dt is 0,so that formula (1) is differentiated and made equal to zero, and the product can be obtained after finishing
2LogTm-Logβ＝Ei/2.303RTm+Log(Ei/AiR) (3)
Description of the formula EiAnd β, TmHave a definite quantitative relationship therebetween.
The method comprises the following steps:
(1) taking 0.2-1.0 g of a dried catalyst with 20-80 meshes as a sample, putting the sample into a sample tube 13, adding a small amount of treated quartz sand at two ends, and loosely plugging a small amount of glass wool at a port. Adding liquid reactants which account for 1/5-1/3 in the saturator 10.
(2) And (4) sample pretreatment. He gas is introduced from the inlet 20 of other gas source, the second four-way valve 7 is switched, and the second interface 702 and the fourth interface 704 of the second four-way valve 7 are in a communication position; switching the first six-way valve 8 to place the first interface 801 and the second interface 802 of the first six-way valve 8 in a communication position, and placing the fifth interface 805 and the sixth interface 806 in a communication position; the second six-way valve 11 is switched so that the first port 1101 and the sixth port 1106 of the second six-way valve 11 are in a communication position, and the fourth port 1104 and the fifth port 1105 are in a communication position (the adsorption operation of the liquid reactant by the catalyst does not involve the first four-way valve 6).
At the moment, He gas is introduced from the inlet 20 of other gas sources, flows into the second interface 702 of the second four-way valve 7 through the pressure stabilizing valve 1, the drying tube 2, the flow stabilizing valve 3 and the gas flowmeter 4, and flows out ofthe fourth interface 704; then flows into the first interface 801 of the first six-way valve 8 and flows out from the second interface 802, and then flows into the fifth interface 805 of the six-way valve 8 through the quantitative pipe 9 and flows out from the sixth interface 806; then flows into the gas inlet of saturator 10 and carries the reactant vapor out of the outlet; the mixed gas (He and reactant vapor) flows in from the sixth port 1106 of the second six-way valve 11 and flows out from the first port 1101, then flows into the gas inlet of the sample tube 13, the sample in the tube is subjected to flow adsorption, and the residual gas flows from the gas outlet of the sample tube 13 to the fourth port 1104 of the second six-way valve 11 and is vented from the fifth port 1105.
He gas passes through the saturator 10 at a flow rate of 10-60 ml/min, and reactant vapor is brought into the sample tube 13 which is constantly at a proper temperature, so that the sample is adsorbed for 1-3 hours. And after the adsorption is finished, closing the gas path to restore the temperature of the sample tube to the room temperature.
If the reactant is gaseous, the gaseous reactant can be directly introduced from other gas source inlets instead of He (the saturator does not need to be filled with the reactant).
He gas is introduced from a carrier gas source inlet 18, and the valve is switched, so that a first interface 601 and a second interface 602 of the first four-way valve 6 are in a communication position; the third port 603 and the fourth port 604 of the first six-way valve 6 are in a communication position; the first port 1101 of the second six-way valve 11 is in a communication position with the second port 1102, and the coupling between the outlet of the sample tube 13 and the fourth port 1104 of the second six-way valve 11 is disconnected.
When in use, He gas enters from a carrier gas source inlet 18, flows into a first interface 601 of a first four-way valve 6 after passing through a pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 3, a gas flow meter 4 and a mixer 5, and flows out from a second interface 602; then flows in from the gas inlet of the reference arm 1601 of the thermal conductivity cell 16 and flows out from the gas outlet; then flows into the third port 803 of the first six-way valve 8 and flows out from the fourth port 804; after passing through the first cold trap 12, the sample flows to the second port 1102 of the second six-way valve 11 and flows out from the first port 1101, and then flows into the gas inlet of the sample tube 13 and flows out directly from the outlet thereof to be discharged.
And (3) blowing the pipeline and the sample for 1-3 hours at room temperature by He according to the gas circuit at the flow rate of 10-60 ml/min to remove the reversibly adsorbed reactant.
After the purging is finished, the outlet of the sample tube 13 is connected to the fourth port 1104 of the second six-way valve 11. At the moment, He gas enters from a carrier gas source inlet 18, flows into a first connector 601 of a first four-way valve 6 after passing through a pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 3, a gas flowmeter 4 and a mixer 5, flows out from a second connector 602, then flows into a gas inlet of a reference arm 1601 of a thermal conductivity cell 16, and flows out from an outlet; then flows into the third port 803 of the first six-way valve 8 and flows out from the fourth port 804; after passing through the first cold trap 12, the sample flows to the second port 1102 of the second six-way valve 11 and flows out from the first port 1101, and then flows into the gas inlet of the sample tube 13 and flows out from the gas outlet; then flows into the fourth port 1104 of the second six-way valve 11 and flows out from the third port 1103; after flowing through the second cold trap 15, the gas flows into the gas inlet of the measuring arm 1602 of the thermal conductivity cell 16 and flows out of the gas outlet to be discharged.
He gas still maintained the flow rate through the sample while purging.
(3) And (3) opening the detector and the computer sampling system, starting a temperature controller program after the baseline is stable, and heating the heating furnace 14 at the speed of 5-25 ℃/min to 400-800 ℃. A temperature programmed surface reaction was initiated.
The voltage signal changes output by the thermocouple and the thermal conductivity cell 16 (or the hydrogen flame detector 17) in the sample tube 13 are respectively subjected to A/D (analog/digital) conversion and then input into a computer for displaying and printing, and a TPSR spectrogram can be obtained.
(4) For organic materials, the reaction mixture may be collected through a second cold trap 15 for a certain temperature interval. Then using inert carrier gas (He, N)2Etc.) are taken out, passed through a chromatographic column and detected by a hydrogen flame detector, the composition of the reaction mixture is analyzed by a computer sampling system and the result is printed.
The basic principle of testing the surface properties of the catalyst by a Temperature Programmed Oxidation (TPO) method using the above-described apparatus is as follows:
when O is present2When the mixed gas prepared by the inert gas He passes through the surface of the carbon deposited catalyst, the mixed gas and the O in the mixed gas are at a specific temperature for a specific carbon species2Oxidation reaction takes place, at which point O in the gas mixture will be consumed2Once the composition of the gas flowing through the reference arm and the composition of the gas flowing through the measurement arm of the thermal conductivity cell change, the output electrical signal of the thermal conductivity cell changes accordingly. O flowing over the surface of the sample if the temperature of the catalyst sample is changed at a certain ramp rate2At one temperature with one carbon species and at another temperature with another carbon species. Therefore, the temperature-time and thermal conductivity cell output signal-time curves can be obtained, and if the two curves are displayed in the same coordinate system, the obtained spectrogram is the TPO spectrum.
The TPO technology is mainly used for the research of carbon burning regeneration of the carbon deposition catalyst and is also used for researching the reaction of gas phase oxygen and the catalyst surface hydrogen adsorption and surface oxygen vacancy.
For the research on the carbon burning regeneration of the catalyst, TPO can continuously reflect the oxygen consumption condition of each temperature in the whole carbon burning process and indirectly reflect the carbon burning rate. The degree of non-uniformity of carbon species can be shown by the number, shape, etc. of oxygen consumption peaks, and the area of oxygen consumption peaks by TPO can be correlated with the amount of carbon deposition.
The method comprises the following steps:
(1) taking 0.2-1.0 g of a 20-80-mesh dry carbon deposition catalyst sample, putting the sample into a sample tube 13, adding a small amount of treated quartz sand at two ends, and loosely plugging a small amount of glass wool at a port.
Mixing O with2Enters from a working gas source inlet 19 and flows through a pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 31, a gas flow meter 4 and a mixer 5. He gas enters from a carrier gas source inlet 18, flows through a corresponding pressure stabilizing valve 1, a drying tube 2, a flow stabilizing valve 3 and a gas flowmeter 4, and then also enters a mixer 5. Two paths of gas are mixed in a mixer 5 to prepare O with the flow rate of 10-60 ml/min2+ He mixed gas (O)25-20% by volume).
The positions of the valves are: the first interface 601 and the second interface 602 of the first four-way valve 6 are in a communication position; the third port 603 and the fourth port 604 of the first six-way valve 6 are in a communication position; the first port 1101 of the second six-way valve 11 is in a communicating position with the second port 1102 and the third port 1103 is in a communicating position with the fourth port 1104 (TPO operation, not involving the second four-way valve).
At this time, the mixed gas flows out from the outlet of the mixer 5, then flows in from the first interface 601 of the first four-way valve 6, and flows out from the second interface 602; then flows in from the gas inlet of the reference arm 1601 of the thermal conductivity cell 16 and flows out from the gas outlet; then flows into the third port 803 of the first six-way valve 8 and flows out from the fourth port 804; after passing through the first cold trap 12, the sample flows to the second port 1102 of the second six-way valve 11 and flows out from the first port 1101, and then flows into the gas inlet of the sample tube 13 and flows out from the outlet thereof; then flows into the fourth port 1104 of the second six-way valve 11 and flows out from the third port 1103; then flows through the second cold trap 15, flows into the gas inlet of the measuring arm 1602 of the thermal conductivity cell 16 and flows out of the outlet to be discharged.
(3) Opening a thermal conductivity cell detector and a computer sampling system; the heating rate of the heating furnace 14 is set to 5-25 ℃/min, and the temperature is increased from room temperature to 400-800 ℃. The change of the voltage signals output by the thermocouple and the thermal conductivity cell 16 in the sample tube 13 are respectively input into a computer after A/D (analog/digital) conversion, after the base line is stabilized, a program of the heating furnace temperature controller is started, and the TPO spectrogram of the sample can be obtained through computer display and printing.
The basic principle of testing the surface property of the catalyst by a Temperature Programmed Decomposition (TPDE) method by adopting the instrument is as follows:
temperature programmed decomposition is a technique for studying the change of the property and state of a catalyst during heating and studying the law of the catalyst by taking the change as a function of temperature or time. I.e., a type of technique that dynamically measures the catalyst properties versus temperature at program ramp temperatures. When the sample is heated in the heating furnace, some substances on the surface of the sample will begin to be desorbed or decomposed and desorbed with the gradual increase of the temperature, and the desorbed substances are then carried into a thermal conductivity cell detector (or a multi-ion detector of a chromatograph-mass spectrometer) by inert carrier gas for detection.
The method comprises the following steps:
(1) taking 0.2-1.0 g of 20-80 meshes of dry catalyst, filling the dry catalyst into a sample tube 13, adding a small amount of treated quartz sand at two ends, and loosely plugging a small amount of glass wool at a port.
(2) Mixing He (or N)2) Gas is introduced from the carrier gas source inlet 18, and the valve is switched to enable the first connector 601 and the second connector 602 of the first four-way valve 6 to be in a communication position;the third port 803 and the fourth port 804 of the first six-way valve 8 are in a communicating position; the first port 1101 of the second six-way valve 11 is in a communicating position with the second port 1102, and the third port 1103 is in a communicating position with the fourth port 1104.
At this time, He (or N)2) Gas enters from a carrier gas source inlet 18, flows through a pressure stabilizing valve 1, a drying pipe 2, a flow stabilizing valve 3, a gas flowmeter 4 and a mixer 5, flows in from a first interface 601 of a first four-way valve 6, flows out from a second interface 602, then flows in from a gas inlet of a reference arm 1601 of a thermal conductivity cell 16, and flows out from an outlet; then flows into the third port 803 of the first six-way valve 8 and flows out from the fourth port 804; flows to the first cold trap 12The gas flows into the gas inlet of the sample tube 13 and flows out from the outlet of the two-six-way valve 11 through the second port 1102 and flows out from the first port 1101; then flows into the fourth port 1104 of the second six-way valve 11 and flows out from the third port 1103; after flowing through the second cold trap 15, the gas flows into the gas inlet of the measuring arm 1602 of the thermal conductivity cell 16 and flows out of the gas outlet to be discharged. The flow rate of the carrier gas He (or N2) is 20-60 ml/min.
(3) Opening a thermal conductivity cell detector and a computer sampling system; the heating rate of the heating furnace 14 is set to 5-25 ℃/min, and the temperature is increased from room temperature to 400-800 ℃. The voltage signal changes output by the thermocouple and the thermal conductivity cell 16 in the sample tube 13 are respectively input to the computer after A/D (analog/digital) conversion. And after the base line is stable, starting a program of the heating furnace temperature control instrument, and displaying and printing through a computer to obtain the TPDE spectrogram of the sample.
Example 1
The TPR test was carried out on the Cu-containing hydrotalcite-like catalyst using an instrument shown in FIG. 1.
1) 0.2g of calcined Cu-containing hydrotalcite-like compound was taken and reduced with H gas2Is H in25% of the mixed gas of-He (total flow rate of the mixed gas: 50 ml/min);
2) after the baseline is stable, carrying out temperature programmed reduction at the temperature rise rate of 10 ℃/min. The TPR spectrum is shown in FIG. 2.
For comparison, a TPR test of CuO was also performed.
1) Take 0.04g of dried CuO and reducing gas H2Is H in25% of the mixed gas of-He (total flow rate of the mixed gas: 50 ml/min);
2) after the baseline is stable, carrying out temperature programmed reduction at the temperature rise rate of 10 ℃/min. The TPR spectrum is shown in FIG. 3.
As can be seen from the figure, the TPR spectrogram of the Cu-containing hydrotalcite-like catalyst and CuO has only one peak, the highest peak temperature of the Cu-containing hydrotalcite-like catalyst is 262, the highest peak temperature of the CuO-containing hydrotalcite-like catalyst is 310, and the highest peak temperature of the Cu-containing hydrotalcite-like catalyst is reduced by 48 compared with that of the CuO-containing hydrotalcite-like catalyst. This shows that the Cu-containing hydrotalcite-like catalyst is changed in the reduction property of the active component copper oxide due to the presence and interaction of other oxides.
Example 2
The iron trioxide catalyst was subjected to a TPD test using an instrument as shown in fig. 1.
1) 0.8g of iron trioxide catalyst, reducing gas H2Is H in25% of the mixed gas of-He (total flow rate of the mixed gas: 50 ml/min); reducing for 2h at 450 ℃; then, the He is turned off, and H is turned on2(30ml/min) and cooled to room temperature (27 ℃).
2) Close H2Opening He (30ml/min) purge to remove reversibly adsorbed H2After the baseline is stable, H is carried out at the speed of 25 ℃/min2And (4) desorbing.
The peak-out direction can be adjusted by selecting the 'positive/negative' switch of the detector. The TPD spectrum is shown in FIG. 4.
As can be seen from fig. 4, the catalyst has only one broadened desorption peak, indicating that the energy distribution on the surface of the catalyst is relatively uniform; the peak temperature is 296 ℃, which shows that the absorption of H is high2The active center is of moderate strength.
Example 3
The TPD test was performed on the molybdenum containing molecular sieve catalyst using an instrument as shown in figure 1.
1) Taking 0.2g of catalyst which is roasted at high temperature, loading the catalyst into a sample tube, blowing the catalyst for 1h by He at 400 ℃, cooling the catalyst to 120 ℃, and after the temperature is constant, using the He to saturate NH by a saturator3The vapor is introduced into the sample tube for adsorption.
2) He (40ml/min) as carrier gas, purging to remove reversibly adsorbed NH3After the baseline is stable, the programmed temperature desorption is carried out at the speed of 10 ℃/min. The TPD spectrum is shown in FIG. 5.
The spectrogram shows that at least three adsorption centers (the highest peak temperature: 242℃, 325 ℃ and 472 ℃) exist on the surface of the catalyst, the energy distribution of the surface is uneven, and the weak acid center is taken as the main point.
Example 4
Using the apparatus shown in FIG. 1, palladium catalyst (Pd/Al)2O3) HOT testing was performed.
1) Adsorption of O2Then, using H2The HOT spectrum of the titration is shown in FIG. 6. As can be seen from the figure, no peak appears in the first five pulse injections, and H appears in the sixth time2The titration began to peak.
2) And (6) data processing. Each peak area is 157.798; 268.024, respectively; 270.976, respectively; 273.002, respectively; 277.182, respectively; 277.658, respectively; 277.607, respectively; 277.299, respectively; 277.361. substituting into corresponding calculation formula to obtain Va(H2)＝0.8488ml；Va 0(H2) 0.7571 ml. The mass of the catalyst weighed during measurement is 0.8g, and the percentage content of Pd in the catalyst is 0.99%; the dispersion R of Pd on the catalyst surface was calculated to be 0.303.
Example 5
The TPSR test was performed on the Cu-containing hydrotalcite-like catalyst using an instrument as shown in fig. 1.
1) Taking 1.0 g of the catalyst, taking cyclohexanol as a reactant, and taking N as carrier gas2And carrying out pretreatment according to steps.
2) Connecting the other end of the sample tube with the fourth interface 1104 of the second six-way valve 11, and connecting N2(40ml/min), after the base line is stable, carrying out temperature programming surface reaction at the speed of 10 ℃/min. The TPSR spectrum is shown in FIG. 7.
As can be seen from FIG. 7, two peaks appear on the TPSR spectrogram, and the highest peak temperatures are 80 ℃ and 188 ℃ respectively; the corresponding arbitrary units of area are 1449 and 2821. The composition analysis of the effluent corresponding to each peak (the cold trap of the device is used for collecting the effluent at different temperatures and a hydrogen flame detector is used for detecting the effluent) shows that the low-temperature peak is cyclohexanol, and the high-temperature peak is mainly the product cyclohexanone except a small amount of cyclohexanol. Two types of adsorption reaction centers of cyclohexanol exist on the surface of the catalyst, a low-temperature peak is a weak adsorption reaction center and has no influence on the conversion of cyclohexanol molecules, a high-temperature peak corresponds to a strong adsorption reaction center, and adsorbed cyclohexanol can generate dehydrogenation reaction on the center.
From the areas of the two peaks, the surface of the catalyst is mainly a strong adsorption reaction center, and the catalyst has higher activity on cyclohexanol conversion.
Example 6
The Zn containing catalyst was subjected to TPO testing using an instrument as shown in figure 1.
1) Weighing 0.3g of catalyst, loading the catalyst into a sample tube, introducing He to activate for 2h at 300 ℃, taking He as carrier gas to carry cyclohexanol vapor, and carrying out coke-hanging treatment on the sample. After 4h of reaction, purging with He for 1 h;
2) and (4) connecting the sample tube into a comprehensive tester device, and operating according to TPO (thermoplastic polyolefin) operation steps. The temperature programming rate was 10 deg.C/min. FIG. 8 is a TPO map of the catalyst.
As can be seen from FIG. 8, the 280 ℃ carbon burning had started and the about 600 ℃ carbon burning was completed. In the whole process of continuous carbon burning, three oxygen consumption peaks occur, and the highest peak temperatures are 319 ℃ (shoulder peak), 345 ℃ and 453 ℃ respectively. As can be seen from the asymmetry of the peak shape and the number of peaks, the carbon deposition species are complex. In addition, the area of the first two peaks is 1.5 times that of the last peak, which indicates that the total amount of the 280-360 ℃ carbon deposit species on the surface of the catalyst is more than that of the high-temperature carbon deposit species.
Example 7
The apparatus shown in fig. 1 was used to perform the TPDE test on CuZnAlCe hydrotalcite-like catalyst.
1) Weighing 0.1g of catalyst, loading the catalyst into a sample tube, and introducing carrier gas He (40 ml/min);
2) and (3) connecting the sample tube into a comprehensive determinator device, and operating according to TPDE (thermoplastic vulcanizate) operation steps. The temperature programming rate was 15 deg.C/min. Figure 9 is the TPDE spectrum of the catalyst.
As can be seen from FIG. 9, the sample was decomposed from 56 ℃ to 469 ℃. From the graph, the decomposition shows two flat-head peaks, the former lasts less than 1 minute, and the latter lasts nearly 9 minutes, which indicates that the decomposition process of the sample is complicated.
Claims (6)
1. A comprehensive tester for the surface properties of a catalyst is characterized by at least comprising: a carrier gas source inlet (18), a working gas source inlet (19), other gas source inlets (20), a gas flowmeter (4), a mixer (5), a first four-way valve (6), a second four-way valve (7), a first six-way valve (8), a second six-way valve (11), a saturator (10), a program temperature control heating furnace (14), a sample tube (13) with a thermocouple inserted therein, a heat conduction cell (16), cold traps (12, 14), a chromatographic column and hydrogen flame detector (17), a computer sampling and displaying system and a spectrogram printing system;
the carrier gas source inlet (18) is communicated with the mixer (5) through a gas flowmeter (4) by a pipeline, and the outlet of the mixer (5) is communicated with a first interface (601) of the first four-way valve (6);
the working gas source inlet (19) is communicated with the mixer (5) and a first interface (601) of the first four-way valve (6) through the flow stabilizing valve (31) and the gas flowmeter (4); or after passing through the flow stabilizing valve (32) and the gas flowmeter (4), the gas flow stabilizer is directly communicated with a fourth interface (604) of the first four-way valve (6), and a third interface (603) of the first four-way valve (6) is communicated with a third interface (703) of the second four-way valve (7);
the other gas source inlet (20) is communicated with a second interface (702) of a second four-way valve (7) through a gas flowmeter (4), and a first interface (701) of the second four-way valve (7) is a vent;
a second interface (602) of the first four-way valve (6) is communicated with a gas inlet of a reference arm (1601) of the heat conduction pool (16), and a gas outlet of the reference arm (1601) of the heat conduction pool (16) is communicated with a third interface (803) of the first six-way valve (8);
a fourth interface (704) of the second four-way valve (7) is communicated with a first interface (801) of the first six-way valve (8); a second interface (802) of the first six-way valve (8) is communicated with a fifth interface (805) through a dosing pipe (9), a sixth interface (806) is communicated with a gas inlet of the saturator (10), and a fourth interface (804) is communicated with a second interface (1102) of the second six-way valve (11) through a first cold trap (12);
a first interface (1101) of the second six-way valve (11) is communicated with a gas inlet of the sample tube (13), a third interface (1103) is connected with a second cold trap (15), the other end of the second cold trap (15) is communicated with a gas inlet of a measuring arm (1602) of a thermal conductivity cell (16) or is communicated with a hydrogen flame detector (17) through a chromatographic column, a fourth interface (1104) is communicated with a gas outlet of the sample tube (13), a fifth interface (1105) is an emptying port, and a sixth interface (1106) is communicated with a gas outlet of the saturator (10);
the sample tube (13) is arranged in a heating furnace (14);
the thermal conductivity cell (or hydrogen flame) detector and the electric signal output end of the thermocouple are connected with a computer sampling, spectrogram displaying and printing system by leads.
2. The apparatus as claimed in claim 1, wherein the carrier gas source inlet (18) is connected with the gas flow meter (4) through the pressure stabilizing valve (1), the drying tube (2) and the flow stabilizing valve (3).
3. The apparatus as claimed in claim 1, wherein the inlet (19) of the working gas source is connected with the mixer (5) and the first interface (601) of the first four-way valve (6) through the pressure stabilizing valve (1), the drying tube (2), the flow stabilizing valve (31) and the gas flow meter (4); or directly communicated with a fourth interface (604) of the first four-way valve (6) after passing through the pressure stabilizing valve (1), the drying pipe (2), the flow stabilizing valve (32) and the gas flowmeter (4);
4. the apparatus according to claim 1, wherein the other gas source inlet (20) is connected with the gas flow meter (4) through the pressure stabilizing valve (1), the drying tube (2) and the flow stabilizing valve (3).
5. The apparatus of any one of claims 1 to 4 for use in the testing of the surface properties of a catalyst.
6. Use according to claim 5, characterized in that a Temperature Programmed Reduction (TPR) process, a Temperature Programmed Desorption (TPD) process, H are used2-O2The surface properties of the catalyst are tested by one of titration technique (HOT), Temperature Programmed Surface Reaction (TPSR), Temperature Programmed Oxidation (TPO) or Temperature Programmed Decomposition (TPDE).
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