阅读说明：本技术 一种测定气体吸附剂变温再生能耗的方法 (Method for measuring temperature-changing regeneration energy consumption of gas adsorbent ) 是由 史全 罗积鹏 于 2020-05-25 设计创作，主要内容包括：本发明公开一种测定气体吸附剂变温再生能耗的方法,具体地说吸附剂变温再生能耗E由两部分组成：气体的脱附焓变ΔH-(des)和吸附剂显热ΔH-(sen)；其中脱附焓变ΔH-(des)通过计算吸附过程的吸附焓变ΔH-(ads),即在吸附温度T-(ads)和脱附温度T-(des)下吸附焓H-(ads)的差值得到,而吸附焓H-(ads)由相应温度T下的等量吸附热Q-(st,T)对吸附量q进行积分得到；其中显热ΔH-(sen)通过单位质量吸附剂的等压比热容C-(p,m)对温度T进行积分计算得到；吸附量q通过等温吸附实验或热重实验来测定；等量吸附热Q-(st,T)通过温度T附近两个不同温度下的等温吸附实验来测定；等压比热容C-(p,m)通过综合物性测量系统来测定；气体吸附、脱附的温度和压力由实际工况来决定。本发明具备测量快速,结果准确,且适用于绝大部分固体吸附剂等优点。(The invention discloses a method for measuring temperature swing regeneration energy consumption of a gas adsorbent, and particularly relates to a method for measuring temperature swing regeneration energy consumption E of the gas adsorbent, which comprises the following two parts: desorption enthalpy change Δ H of gas des And sensible heat of adsorbent Δ H sen (ii) a Wherein the desorption enthalpy change DeltaH des By calculating the change in enthalpy of adsorption Δ H of the adsorption process ads I.e. at the adsorption temperature T ads And desorption temperature T des Lower adsorption enthalpy H ads Is obtained while the adsorption enthalpy H is ads From the heat of adsorption Q of equal amount at the corresponding temperature T st,T Integrating the adsorption quantity q to obtain; in which sensible heat Δ H sen Isobaric specific heat capacity C by unit mass of adsorbent p,m Carrying out integral calculation on the temperature T to obtain; the adsorption quantity q is determined by an isothermal adsorption experiment or a thermogravimetric experiment; equivalent heat of adsorption Q st,T The temperature is measured by isothermal adsorption experiments at two different temperatures near the temperature T; isobaric specific heat capacity C p,m Measured by an integrated physical property measurement system; the temperature and pressure of gas adsorption and desorption are determined by actual working conditions. The inventionThe method has the advantages of quick measurement, accurate result, suitability for most solid adsorbents and the like.)

1. A method for measuring the temperature swing regeneration energy consumption of a gas adsorbent is characterized by comprising the following steps: the adsorbent temperature-swing regeneration energy consumption E consists of two parts: desorption enthalpy Change Δ H for releasing adsorbed gas_desAnd for heating the adsorbent to the desorption temperature T_desSensible heat Δ H of_sen(ii) a Wherein the desorption enthalpy change DeltaH_desBy calculating the change in enthalpy of adsorption Δ H of the adsorption process_adsI.e. at the adsorption temperature T_adsAnd desorption temperature T_desLower adsorption enthalpy H_adsIs obtained while the adsorption enthalpy H is_adsFrom the heat of adsorption Q of equal amount at the corresponding temperature T_st,TIntegrating the adsorption quantity q to obtain; in which sensible heat Δ H_senIsobaric specific heat capacity C by unit mass of adsorbent_p,mCarrying out integral calculation on the temperature T to obtain; wherein the adsorption quantity q is determined by an isothermal adsorption experiment or a thermogravimetric experiment; equivalent heat of adsorption Q_st,TThe method is characterized by comprising the following steps of (T +/-1-30) K, preferably T +/-5-25) K) measuring by isothermal adsorption experiments at two different temperatures near the temperature T; isobaric specific heat capacity C_p,mMeasured by a quantity Design Physical Property Measurement System (PPMS); adsorption temperature T_adsAdsorption pressure p_adsDesorption temperature T_desAnd a desorption pressure p_desDetermined and measured according to the working conditions of the adsorbent in actual useAnd (4) obtaining.

2. The method for determining the energy consumption for temperature swing regeneration of an adsorbent according to claim 1, wherein: adsorption temperature T_adsThe adsorption capacity q is measured by an isothermal adsorption experiment; desorption temperature T_desNext, if the adsorption amount q is large (q.gtoreq.5 mg/g), it can be measured by both isothermal adsorption experiments and thermogravimetric experiments, and if the adsorption amount q is small (q.gtoreq.5 mg/g)<5mg/g) using a thermogravimetric experiment.

3. The method for determining the energy consumption for temperature swing regeneration of an adsorbent according to claim 1, wherein: during calculation, the adsorption quantity q measured by the isothermal adsorption instrument is fitted with the data of the temperature T and the pressure p to form a function q ═ q_T(p) and substituting the obtained value into corresponding T, p to obtain the adsorption quantity q under the adsorption or desorption condition.

4. The method for determining the energy consumption for temperature swing regeneration of an adsorbent according to claim 1, wherein: the thermogravimetric determination method of the adsorption quantity q is as follows: accurately weighing the fully desorbed and activated adsorbent and transferring the adsorbent to a thermogravimetric instrument; ② introducing the pressure intensity into the instrument as desorption pressure p_desMaintaining the adsorbed gas for a period of time (1-10 h, preferably 2-5 h) to make the adsorbent reach adsorption equilibrium at room temperature; thirdly, the temperature is raised to the temperature T to be measured₁A temperature T of low delta T (5-50K, preferably 10-25K)₀(T₀＝T₁Delta T) and keeping the temperature for a period of time (1 to 10 hours, preferably 2 to 5 hours) to reach adsorption balance, and recording the unit weight loss delta m₀(ii) a Fourthly, the temperature is raised to the temperature T to be measured₁Keeping the temperature for a period of time, and recording the corresponding unit weight loss delta m₁，Δm₁And Δ m₀The difference is T₀、T₁Difference q between the adsorption amounts at two temperatures₁(q₁＝Δm₁-Δm₀) (ii) a Gradually raising temperature to higher temperature T_i(T_i＝T₀+ i.DELTA.T) and keeping the temperature for a period of time (1-10 h, preferably 2-5 h), and recording the corresponding unit weight loss DELTA m_iCalculating the difference q of the adsorption amount_i(q_i＝Δm_i-Δm₀) (ii) a Sixthly, repeating the step five until q_i+1And q is_iThe difference of (a) tends to be zero<0.5mg/g), i.e.. DELTA.m_i+1≈Δm_iAt this time, it can be identified as T_iThe adsorbent is completely desorbed, so that the adsorption capacity q at the temperature to be measured is delta m_i-Δm₁＝q_i-q₁。

5. The method for determining the energy consumption for temperature swing regeneration of an adsorbent according to claim 1, wherein: equivalent heat of adsorption Q_st,TDuring measurement, the smaller the temperature difference of the two isothermal adsorption experiments is, the better the temperature difference is (1-30K, preferably 1-10K); two temperatures T_a、T_bAdsorption capacity function q of_a＝q_Ta(p_a)、q_b＝q_Tb(p_b) Should be converted into a function p of pressure_a＝p_Ta(q_a)、p_b＝p_Tb(q_b) And substituting the equation into the Clausius-Clabelong equation to obtain a curve of the equivalent adsorption heat changing along with the adsorption quantity.

6. The method for determining the energy consumption for temperature swing regeneration of an adsorbent according to claim 1, wherein: specific heat capacity C measured by comprehensive physical property measuring system_p,mThe data with temperature T should be fitted to a modified Debye-Einstein equation to calculate the sensible heat Δ H_sen。

Technical Field

The invention relates to the field of adsorbents, in particular to a method for measuring temperature-changing regeneration energy consumption of a gas adsorbent.

Background

In recent decades, the global warming and climate change situation has become more severe and is increasingly affecting people's production and life. It is now generally accepted that excessive emissions of greenhouse gases, particularly carbon dioxide, are the main contributor. However largeCO in gas₂The concentration still increased year by year, from about 277ppm in 1750 to 412ppm with the highest history in 2019. In order to reduce the concentration of carbon dioxide in the atmosphere, researchers have proposed many possible measures. Among them, carbon capture and sequestration is one of the most promising measures, because it can effectively reduce carbon emissions without hindering social and economic development.

The industry currently uses amine detergents (e.g., 30 wt% monoethanolamine solutions) primarily to trap carbon, but they are corrosive and consume large amounts of energy to evaporate water during material regeneration, thereby affecting process economics. To get rid of these disadvantages, attention has been directed to solid adsorbents, in particular metal organic framework compounds (MOFs). Because of the high adjustability and the diversity of coordination modes of metal ions and organic ligands constituting MOFs, MOFs has infinite composition, structure and property controllability, and can be CO₂Adsorption and separation provide a large number of candidates. Because of this, it is very important to quickly and accurately screen out good quality adsorbents from various MOFs.

Currently, the screening and evaluation of MOFs adsorbents mainly focus on the gas adsorption separation performance, such as the stability, tolerance, cyclability, adsorption selectivity, adsorption capacity and the like of materials. However, for another important evaluation criterion, adsorption regeneration energy consumption, the research and understanding degree is far from enough. There are various ways for regenerating the adsorbent, including temperature swing adsorption regeneration, pressure swing adsorption regeneration, vacuum pressure swing adsorption regeneration, magnetic induction adsorption regeneration, light induction adsorption regeneration and mixing method, among which, temperature swing adsorption regeneration is one of the most economical and promising technologies because it is most easily integrated into the existing factories. As to how to determine the regeneration energy consumption of temperature swing adsorption, although researchers propose methods such as a High-throughput analysis model [ j.p.scale, w.m.verdegal, w.lu, m.wriedt, h.c.zhou, High-throughput analytical model to evaluation Materials for temporal scanning processes, Advanced Materials,25(2013) 3957-; or the method belongs to theoretical fitting and cannot represent actual conditions; therefore, the requirements of quick, efficient, accurate and general evaluation cannot be met. Therefore, the development of a novel method for measuring the temperature swing regeneration energy consumption of the gas adsorbent is urgently needed.

Disclosure of Invention

The invention aims to provide a method for measuring the temperature swing regeneration energy consumption of a gas adsorbent, which has the advantages of quick measurement, accurate result, suitability for most solid adsorbents and the like and can be used as a standard method for measuring the temperature swing regeneration energy consumption of the adsorbent.

The purpose of the invention is realized by the following technical scheme:

the adsorbent temperature-swing regeneration energy consumption E mainly comprises two parts: desorption enthalpy Change Δ H for releasing adsorbed gas_desAnd for heating the adsorbent to the desorption temperature T_desSensible heat Δ H of_senAs shown in equation 1:

E＝ΔH_des+ΔH_sen (1)

wherein the desorption enthalpy change deltaH is due to the fact that the adsorption and desorption are completely reversible processes_desCan be calculated by calculating the change of enthalpy of adsorption Delta H of the adsorption process_adsI.e. at the adsorption temperature T_adsAnd desorption temperature T_desLower adsorption enthalpy H_adsThe difference of (a) is obtained as shown in equations 2 and 3:

ΔH_des＝ΔH_ads＝H_ads(T_ads)-H_ads(T_des) (2)

where Q is the gas adsorption capacity of the adsorbent at the corresponding temperature T and pressure p, Q_st,TIs the heat of equivalent adsorption at the corresponding temperature T; in which sensible heat Δ H_senCan be calculated by equation 4:

in the formula C_p,mIs the isobaric specific heat capacity per mass of adsorbent; wherein the adsorption quantity q is determined by an isothermal adsorption experiment or a thermogravimetric experiment; equivalent heat of adsorption Q_st,TThe temperature is measured by isothermal adsorption experiments at two different temperatures near the temperature T; isobaric specific heat capacity C_p,mDetermined by a comprehensive Physical Properties Measurement System (PPMS); the temperature and pressure of gas adsorption and desorption are determined by actual working conditions.

Further, the adsorption temperature T_adsThe lower adsorption quantity q is preferably determined by an isothermal adsorption experiment; desorption temperature T_desNext, if the adsorption amount q is large, it can be measured by both an isothermal adsorption experiment and a thermogravimetric experiment, and if the adsorption amount q is small, it is preferentially measured by the thermogravimetric experiment.

Further, the adsorption quantity q measured by the isothermal adsorption apparatus is fit to the data of the temperature T and the pressure p to form a function q ═ q_T(p), substituting into corresponding T, p to obtain the adsorption capacity q under the actual working condition.

Further, the thermogravimetric method of the adsorption quantity q is as follows: 1. accurately weighing the completely desorbed and activated adsorbent and transferring the adsorbent into a thermogravimetric instrument; 2. introducing adsorbed gas with a certain fixed pressure into the instrument and maintaining for a period of time to ensure that the adsorbent achieves adsorption balance at room temperature; 3. then the temperature is raised to the temperature T to be measured₁Temperature T of low Delta T₀(T₀＝T₁- Δ T) and thermostatting for a period of time to reach adsorption equilibrium, recording the weight loss per unit Δ m₀(ii) a 4. Then the temperature is increased to delta T to the temperature T to be measured₁Keeping the temperature for a period of time, and recording the corresponding unit weight loss delta m₁，Δm₁And Δ m₀The difference is T₀、T₁Difference q between the adsorption amounts at two temperatures₁(q₁＝Δm₁-Δm₀) (ii) a 5. Then gradually increasing the temperature to a higher temperature T_i(T_i＝T₀+ i.DELTA T) and keeping constant temperature for a period of time, recording corresponding unit weight loss DELTA m_iCalculating the difference q of the adsorption amount_i(q_i＝Δm_i-Δm₀) (ii) a 6. Repeating the step 5 until q_i+1And q is_iTends to zero, i.e. Δ m_i+1≈Δm_iAt this time can recognizeIs fixed at T_iThe adsorbent is completely desorbed, so that the adsorption capacity q at the temperature to be measured is delta m_i-Δm₁＝q_i-q₁。

Further, the heat of adsorption Q is equivalent_st,TDuring measurement, the smaller the temperature difference of the two isothermal adsorption experiments is, the better the temperature difference is (less than or equal to 30K); two temperatures T_a、T_bAdsorption capacity function q of_a＝q_Ta(p_a)、q_b＝q_Tb(p_b) Conversion into a function p of pressure_a＝p_Ta(q_a)、p_b＝p_Tb(q_b) And substituting into Clausius-Clapeyron equation (Clausius-Clapeyron equation, equation 5), a curve of the equivalent adsorption heat varying with the adsorption amount can be obtained:

wherein R is an ideal gas constant (R: 8.3145J. mol)^-1·K^-1)。

Further, the specific heat capacity C measured by PPMS_p,mFitting the data with temperature T to a modified Debye-Einstein equation (Debye-Einstein function, equation 6) and substituting into equation 4 to calculate sensible heat Δ H_sen：

In the formula, D (theta)_DT) and E (theta)_E/T) are Debye and Einstein functions, m, n, theta, respectively_D，Θ_E，A₁And A₂Are all adjustable parameters.

The invention has the following beneficial effects:

(1) the isothermal adsorption instrument, the thermogravimetric instrument and the comprehensive physical property measuring system used in the invention are all existing commercial instruments, and the sample is loaded, the measuring program is set, and the unattended operation is not needed, so that the simple, convenient, easy to operate and uninterrupted test can be realized.

(2) The errors of the measuring means used by the method are small (less than or equal to 2%), so that the obtained numerical value of the regeneration energy consumption has high reliability.

(3) The method has high universality on the test sample, and only needs the sample not to react with a test instrument or a container, so the method can be used as a standard determination method for the temperature swing regeneration energy consumption of the adsorbent.

The method has the advantages of quick measurement, accurate result, suitability for most solid adsorbents and the like.

Drawings

FIG. 1 is a flow chart of the scheme of the invention.

FIG. 2 is a schematic view of an isothermal adsorption curve of an embodiment of the present invention.

FIG. 3 is a schematic diagram of the equivalent heat of adsorption curve of an embodiment of the present invention.

FIG. 4 is a schematic thermogravimetric plot of an embodiment of the present invention.

FIG. 5 is a schematic representation of specific heat capacity curves for examples of the present invention.

Detailed Description

The invention is described in detail below with reference to the figures and examples.

As shown in fig. 1, the adsorbent temperature swing regeneration energy consumption E mainly consists of two parts: desorption enthalpy Change Δ H for releasing adsorbed gas_desAnd for heating the adsorbent to the desorption temperature T_desSensible heat Δ H of_sen(ii) a Wherein the desorption enthalpy change deltaH is due to the fact that the adsorption and desorption are completely reversible processes_desCan be calculated by calculating the change of enthalpy of adsorption Delta H of the adsorption process_adsI.e. at the adsorption temperature T_adsAnd desorption temperature T_desLower adsorption enthalpy H_adsIs obtained while the adsorption enthalpy H is_adsCan be determined by the heat of adsorption Q at the corresponding temperature T_st,TIntegrating the adsorption quantity q to obtain; in which sensible heat Δ H_senConstant pressure specific heat capacity C per unit mass of adsorbent_p,mCarrying out integral calculation on the temperature T to obtain; in the measurement, the adsorption amount q is measured by an isothermal adsorption experiment or a thermogravimetric experiment; equivalent heat of adsorption Q_st,TThe temperature is measured by isothermal adsorption experiments at two different temperatures near the temperature T; isobaric specific heat capacityC_p,mMeasured by an integrated physical property measurement system; the temperature and pressure of gas adsorption and desorption are determined by actual working conditions.

In this example, functionalized UiO-66- (OH) is selected₂The compound is subjected to temperature swing regeneration energy consumption evaluation, and the preset condition is temperature T during adsorption_ads298K, pressure p_ads＝113mmHg(CO₂) Temperature at desorption T_des373K, pressure p_des＝750mmHg(CO₂)。

In the present embodiment, the adsorption temperature T_adsAdsorption capacity q at 298K_a(298K) As determined by the 298K isothermal adsorption experiment, the results are shown in fig. 2, by fitting:

substitution adsorption temperature T_ads298K, adsorption pressure p_adsUnder the condition of 113mmHg, the adsorption quantity q is obtained_a(298K,113mmHg)＝12.8mg/g。

In this example, the sample is taken at T_a298K and T_bEquivalent heat of adsorption Q was calculated from isothermal adsorption experimental data (fig. 2) at two temperatures of 273K_st,TFitting two temperatures to obtain an adsorption quantity function q_a、q_bConversion into a function p of pressure_a、p_b：

Pressure p at any adsorption amount_a、p_bAnd temperature T_a＝298K，T_bSubstituting 273K into the clausius-crarbelong equation (equation 5) to obtain the equivalent heat of adsorption Q_stThe curve according to the adsorption amount is shown in FIG. 3.

In the present embodiment, the desorption temperature T_desThe amount of adsorption q (373K) at 373K was determined using thermogravimetric experiments (figure 4): 1. completely desorbing the activated UiO-66- (OH)₂Accurately weighed (12.69mg) and transferred to a thermogravimetric instrument; 2. then introducing desorption pressure p into the instrument_desCarbon dioxide at 750mmHg and maintained for 3h to allow the adsorbent to reach adsorption equilibrium at room temperature; 3. heating to T₀Keeping the temperature for 2h at 348K to reach adsorption balance, and recording the unit weight loss delta m₀25.8 mg/g; 4. then the temperature is increased to delta T25K to the desorption temperature T₁Keeping the temperature for 2h to reach adsorption balance while 373K, and recording the unit weight loss delta m₁29.4 mg/g; 5. then the temperature is increased to 25K to a higher temperature T₂Keeping the temperature for 2h at 398K, and recording the unit weight loss delta m₂29.3 mg/g; this is the difference in the adsorption amounts q between temperatures 348K and 373K and 348K and 398K, respectively₁＝0.36mg/g,q₂The desorption temperature T is 0.35mg/g, so that the desorption of the sample at 373K is complete, the adsorption quantity cannot be negative, and the desorption temperature T is₁(T_des) The adsorption capacity q (373K) at 373K was 0 mg/g.

In this example, UiO-66- (OH) was measured using PPMS₂The sample heat capacity in the 400K temperature region (FIG. 5) was matched to the modified Debye-Einstein equation:

in this embodiment, UiO-66- (OH) is calculated by substituting the above data into equations 1 to 4₂Desorption enthalpy change Δ H of adsorbent_des9.64J/g, sensible heat Δ H_sen71.87J/g and 81.51J/g of temperature-changing regeneration energy consumption E.

In the present example, the above measurement process was repeated three times to obtain the temperature-changing regeneration energy consumptions E of 78.85J/g,81.51J/g, and 82.64J/g, i.e. the measurement repeatability is obtained>97％；UiO-66-(OH)₂The temperature swing regeneration energy consumption of the adsorbent is obtained to be 79.5J/g through molecular and Monte Carlo simulation calculation, namely the error between the method for measuring the temperature swing regeneration energy consumption of the adsorbent and a theoretical value<2％。

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.