CN103983537A - Method for rapidly determining vapor pressure of solid chemicals - Google Patents

Abstract

The invention discloses a method for rapidly determining vapor pressure of solid chemicals. The method is characterized by comprising the steps: (1) preparing a test sample: grinding the test sample into powder, and drying the test sample in a drying device before the test; (2) determining the test sample: placing the test sample in an aluminum sampling disc with the diameter of 5mm-10mm, uniformly distributing the test sample, and facilitating the smoothness of the surface; selecting nitrogen as the protection gas and carrier gas, selecting the flow rate of 20mL/min to 100mL/min, and setting a determination program to determine; (3) reference determination: selecting substances with the known temperature being associated to the vapor pressure such as benzoic acid and phthalic anhydride as a reference substance, and determining the vapor pressure according to the same process with the test sample determination; and (4) processing the data. The method has the advantages of convenience in operation, high measuring speed, less consumption of test samples and the like.

Description

A kind of method of Fast Measurement Solid-state Chemistry product vapor pressure

Technical field

The invention belongs to technical field of chemistry, relate to a kind of method of Fast Measurement Solid-state Chemistry product vapor pressure.

Background technology

Material vapor pressure has formed a lot of assay methods, as ebulliometry, constant-pressure meter method, transpiration method, the gloomy effusion method of anger etc., can be summarized as generally dynamic method and the large class of static method two.In general, static method is used for measuring middle high-pressure vapor pressure pressure measurement lower limit and is about 1kPa, and constant-pressure meter method is typical static method; Ebulliometry is typical dynamic method, can be used for relatively some more low vapor pressure and measures, but be preferably not less than 0.5kPa, is limited to 0.05Pa (paying China etc., 2010) under the pressure measurement of transpiration method.The study on determination method of utmost point low-vapor pressure is more in recent years, and wherein, quality effusion method is to measure the most accurate and effective method of organism utmost point low-vapor pressure always.In measured matter is placed on foraminate box, box is outward vacuum, vapour molecule will be constantly from aperture to external diffusion, if being diffused into the gas molecule at aperture place can all overflow by aperture, theoretical according to gas molecule motion, by the amount that experiment records the temperature of system, in the area of aperture and unit interval inner box, material reduces, just can calculate the saturated vapour pressure of this material.In recent years, the moment of torsion of robotization and the appearance of vacuum microbalance, realize the continuous coverage under sky, compares the research less (Li Yanhong etc., 2006) that domestic relevant low-vapor pressure is measured with foreign study situation

C.G. DE KRUIF and J.G. BLOK has measured benzoic acid vapor pressure (C.G. DE KRUIF in 311-391K temperature range, 1982) show that thus benzoic vapor pressure and temperature relation are 1np=-10803/T+34.038, R2=1, M.COLOMINA etc. have measured the vapor pressure (M.COLOMINA of benzoic 6 kinds of mesitylenic acid derivants with Knudsen effusion method, 1984) and 3 kinds of benzoic vapor pressure (M.COLOMINA of tetramethyl, 1988), Xian-Wei Li etc. have measured vapor pressure (the Xian-Wei Li of 4 kinds of chemical substances such as dibenzofurans with Knudsen effusion method, 2002), SAYED MOHAMMAD ALIHOSSEINI etc. has measured nitro benzyl chloride and benzoic vapor pressure (SAYED MOHAMMAD ALIHOSSEINI with Knudsen effusion method, 2006), Federica Barontini etc. has measured 1-METHYLPYRROLIDONE with thermogravimetry, 1, ammediol, benzyl oxide, 2 hydroxy naphthalene and salicylic vapor pressure (Federica Barontini, 2007), G V Kunte etc. measure metal organic compound chemical vapor deposition and benzoic vapor pressure (G V Kunte with thermogravimetry, 2008).The vapor pressure of Knudsen effusion method P-hydroxybenzoic acid, paracyanobenzoic acid, 4-methylamino acid, 4-methylamino acid, paraacetaminobenzoic acid, 4-ABA for Manuel J.S.Monte etc.

Visible, all mainly concentrate on both at home and abroad and reduce the research of measuring lower limit, thermogravimetry is useful on liquid substance saturated vapour pressure mensuration aspect research report at home and abroad, have no for measuring solid matter vapor pressure report, external corresponding research is also less, 2 pieces of close bibliographical informations only, external solid research is mainly measured solid matter vapor pressure with Knudsen effusion method.

Static method is applicable to normal pressure and high pressure occasion more, and device is simple, easy to operate, therefore use more, but sample dosage is large, measures time-consuming.Dynamic method is used for the measurement of vapor pressure under normal pressure, is also to use more method.Intend static method when the vapor pressure measurement of multicomponent system (as petroleum fraction, coal liquid fraction), there is unique advantage, can save the degassed operation of liquid nitrogen, measure rapidly.Reid method and reference fado detect oil quality for factory, and how experimental study does not adopt.The mensuration of atomic vapor pressure had very large realistic meaning in recent years, studied also morely, need to adopt special experiment research as knudsen effusion method, and the instrument and equipment of knudsen effusion method is complicated, expensive, domesticly seldom used.Thermal analysis system and chromatography are modern measuring methods, and amount of samples is few, measure rapidly, accuracy is high, carried out in recent years the research of this respect abroad, domestic research is less, should explore the suitable operating conditions of these Modern Analytical Instrument to specific sample.

Summary of the invention

In order to overcome the defect existing in prior art, the present invention proposes a kind of method of Fast Measurement Solid-state Chemistry product vapor pressure, the vapor pressure of material is the saturation vapour pressure of solid or liquid substance top, when thermodynamic equilibrium, the vapor pressure of pure material is the function of temperature, and vapor pressure variation with temperature rule and corresponding relation can utilize respectively Clapeyron equation and Antonie formula to solve.Vapor pressure is the basic characteristic of persistence organic pollutant, for determining that distribution and the final result of persistence organic pollutant in environment has vital role, increase along with molecular weight of material, its boiling point is more and more higher, vapor pressure is also more and more difficult to measure, the steaming pressure data of Solid-state Chemistry product is not still assessed one of its volatile significant data, still it is carried out to ecological toxicology test (as fast degraded biologically simultaneously, acute toxicity test for aquatic organism etc.) foundation that method is selected, at present, higher boiling low volatility novel solid chemical vapor presses to measure becomes a difficult problem urgently to be resolved hurrily.The present invention sets up a kind of method of Fast Measurement Solid-state Chemistry product vapour pressure, and the method is compared the advantages such as to have automaticity high, easy to operate, and measuring speed is fast, and sample dosage is few with other method.

Steaming pressure data is usually used in Phase Equilibrium Calculation, by steaming pressure data, can also obtain the important thermodynamic functions such as evaporation enthalpy, enthalpy of sublimation, meanwhile, vapor pressure is still evaluated the important indicator of material stability, as the vapor pressure of advanced space flight and aviation fuel just needs strict control.The vapor pressure of liquid substance is measured more convenient, and method is also very ripe, and the vapor pressure of solid is lower, and during room temperature, vapor pressure, below 0.1Pa, adopts conventional dynamic method and static method all cannot achieve the goal.Thereby research solid matter vapor pressure assay method is meaningful and practical use, particularly in testing, the risk assessment of novel chemical substance and the MSDS basic data of material have important using value.The steaming pressure data of novel chemical substance is still its risk assessment and one of its volatile significant data of assessment not, is also that it is carried out to the foundation that ecological toxicology test (as fast degraded biologically, acute toxicity test for aquatic organism etc.) method is selected simultaneously.

By to existing vapor pressure Study on Test Method and comparison, for current higher boiling low volatility novel solid chemical vapor, press the deficiency of assay method, according to existing vapor pressure balancing method thought, set up thermogravimetry and measure higher boiling low volatility novel solid chemical vapor pressure assay method.

The saturated vapour pressure of solid matter, refers to the saturation vapour pressure on solid under specified temp.In certain temperature range, the logarithm of pure material vapor pressure is linear dependence with the inverse of temperature under Dynamic Thermal equilibrium condition.As shown in gram general imperial equation of labor Hughes-carat of following simplification:

$\mathrm{lgp}=\frac{\mathrm{\ΔHv}}{2.3\mathrm{RT}}+C.$

In formula:

P---vapor pressure (kPa);

△ Hv---heat of evaporation (J/mol);

T---test temperature (K);

R---universal gas constant 8.314 (J/molK);

C-constant.

Its technical scheme is as follows:

A method for Fast Measurement Solid-state Chemistry product vapor pressure, comprises the following steps:

(1) sample preparation

Sample is prepared into Powdered, dry in exsiccator before test;

(2) Specimen Determination

Use the aluminum sample disc of a diameter 5-10mm to install sample, sample is uniformly distributed, surfacing; Select nitrogen as protection gas and carry gas, select flow velocity 20mL/min-100mL/min, (heating rate with 5-20 ℃/min is at the uniform velocity warming up to desired temperature point to set mensuration program, as 50 ℃, constant temperature 10-20min, be more at the uniform velocity warming up to next desired temperature point with the heating rate of 5-20 ℃/min, as 70 ℃, constant temperature 10-20min, so program repeats 5-7 time) measure;

(3) reference is measured

The material of selection known temperature and vapor pressure relation is done reference material as benzoic acid, phthalic anhydride and is measured according to the same program of Specimen Determination;

(4) data processing

1), by the loss in weight of constant temperature zone, calculate the evaporation rate of this temperature; Rate of volatilization calculates according to the following formula;

$v_T=\frac{1}{a}\×\frac{\mathrm{dm}}{\mathrm{dt}}\×\frac{T}{M}$

In formula:

VT-evaporation rate (kg/sm ²);

Surface area (the m of a-volatilization ²);

Mass loss ((kg/s) in the dm/dt-unit interval;

T-absolute temperature (K);

The tested thing molal weight of M-(kg);

2) in EXCEL by the different temperatures evaporation rate of reference substance and corresponding vapor pressure values list, by vapor pressure, evaporation rate is mapped, obtain a straight line, its slope is k;

3) according to following formula, calculate the vapor pressure of measured matter corresponding temperature;

P _T＝k×v _T

4) in EXCEL by the inverse of temperature and the list of corresponding vapor pressure logarithm value, by vapor pressure logarithm value, inverse temperature is mapped, draw both sides relation formula;

5) by the relational expression drawing, calculate target temperature 1nP, the logarithm of negating draws the vapor pressure values of target temperature.

Further preferably, the target temperature step 5) is 20 ℃ or 25 ℃.

Beneficial effect of the present invention: technical solution of the present invention is compared the advantages such as to have automaticity high, easy to operate, and measuring speed is fast, and sample dosage is few with other method.

Accompanying drawing explanation

Fig. 1 is benzoic acid vapor pressure and rate of volatilization graph of a relation;

Fig. 2 is benzoic acid TG curve;

Fig. 3 is phthalic anhydride TG figure;

Fig. 4 is that phthalic anhydride 1nP is to temperature 1/T relation curve.

Embodiment

Below in conjunction with embodiment, technical scheme of the present invention is described in more detail.

Embodiment phthalic anhydride vapor pressure is measured.

Get appropriate sample A benzoic acid in special-purpose aluminium dish, shake is evenly paved sample gently.

With empty standard aluminum dish, to instrument zero clearing, the aluminium dish that installs sample is put into the platinum dish of thermogravimetric analyzer, handled instrument and hang up properly sample, heating furnace automatic-ascending, for carrying gas, adjusts nitrogen flow rate 60mL/min with nitrogen, setup control program, carries out thermogravimetric analysis to sample.Program after optimization is:

Heating rate with 10 ℃/min is warming up to 40 ℃, constant temperature 10min, heating rate with 10 ℃/min is warming up to 50 ℃, constant temperature 10min, heating rate with 10 ℃/min is warming up to 60 ℃, constant temperature 10min, is warming up to 70 ℃, constant temperature 10min with the heating rate of 10 ℃/min, heating rate with 10 ℃/min is warming up to 80 ℃, constant temperature 10min, is warming up to 90 ℃, constant temperature 10min with the heating rate of 10 ℃/min, heating rate with 10 ℃/mmin is warming up to 100 ℃, constant temperature 10min, is warming up to 110 ℃, constant temperature 10min with the heating rate of 10 ℃/min.Obtain benzoic data and list in table 1:

Table 1 benzoic acid evaporation rate and steaming pressure data

The pass of benzoic acid vapor pressure and evaporation rate is y=560.03x-0.0068, R ²=1, slope k=560.03.

Phthalic anhydride is measured, and relatively its measured value and literature value, verify method.

Get appropriate sample B phthalic anhydride in special-purpose aluminium dish, shake is evenly paved sample gently, chooses the rear identical test condition of benzoic acid of measuring of optimization and measures, and result as shown in Figure 3.

Table 2 phthalic anhydride evaporation rate and steaming pressure data

Note: phthalic anhydride molal weight is 148g/mol, k=560.03, aluminium dish cart area is 3.32 * 10 ^-5m ².

Table 3 phthalic anhydride at the uniform velocity heats up and adds 1nP and the 1/T data of constant temperature

With 1nP, 1/T is mapped, obtain its relation function curve, as shown in Figure 4.

The 1nP of phthalic anhydride and 1/T relational expression are: 1nP=--9722.4/T+30.529, the vapor pressure that can calculate 20 ℃, 25 ℃ is 0.07Pa, 0.12Pa.1nP and 1/T relational expression that By consulting literatures data matching obtain phthalic anhydride are: 1nP=--9465/T+29.559.R ²＝0.9993。The vapor pressure of 20 ℃, 25 ℃ is 0.07Pa, 0.11Pa, and the standard deviation of measured value and literature value is respectively 0% and 9%.Measured value and literature value are comparatively approaching, and method is feasible, reliable results.

The above; it is only preferably embodiment of the present invention; protection scope of the present invention is not limited to this; anyly be familiar with those skilled in the art in the technical scope that the present invention discloses, the simple change of the technical scheme that can obtain apparently or equivalence are replaced and are all fallen within the scope of protection of the present invention.

Claims (2)

1. a method for Fast Measurement Solid-state Chemistry product vapor pressure, is characterized in that, comprises the following steps:

(1) sample preparation

Sample is prepared into Powdered, dry in exsiccator before test;

(2) Specimen Determination

Use the aluminum sample disc of a diameter 5-10mm to install sample, sample is uniformly distributed, surfacing; Select nitrogen as protection gas and carry gas, selecting flow velocity 20mL/min-100mL/min, setting mensuration program and measure;

(3) reference is measured

The material of selection known temperature and vapor pressure relation is done reference material as benzoic acid, phthalic anhydride and is measured according to the same program of Specimen Determination;

(4) data processing

1), by the loss in weight of constant temperature zone, calculate the evaporation rate of this temperature; Rate of volatilization calculates according to the following formula;

$v_T=\frac{1}{a}\×\frac{\mathrm{dm}}{\mathrm{dt}}\×\frac{T}{M}$

In formula:

VT-evaporation rate (kg/sm ²);

Surface area (the m of a-volatilization ²);

Mass loss ((kg/s) in the dm/dt-unit interval;

T-absolute temperature (K);

The tested thing molal weight of M-(kg);

2) in EXCEL by the different temperatures evaporation rate of reference substance and corresponding vapor pressure values list, by vapor pressure, evaporation rate is mapped, obtain a straight line, its slope is k;

3) according to following formula, calculate the vapor pressure of measured matter corresponding temperature;

P _T＝k×v _T

4) in EXCEL by the inverse of temperature and the list of corresponding vapor pressure logarithm value, by vapor pressure logarithm value, inverse temperature is mapped, draw both sides relation formula;

5) by the relational expression drawing, calculate target temperature 1nP, the logarithm of negating draws the vapor pressure values of target temperature.

2. the method for Fast Measurement Solid-state Chemistry product vapor pressure according to claim 1, is characterized in that step 5) described in target temperature be 20 ℃ or 25 ℃.