JPH0679011B2 - Method and apparatus for continuously measuring PH of non-aqueous sample - Google Patents

Description

Detailed Description of the Invention

 Purpose of the invention

[Industrial applications]

The present invention relates to a method for continuously measuring the pH of non-aqueous samples, especially oils, during the operation of the process, and also includes the equipment used to carry out the method.

[Prior art]

The pH of reaction products and recovered unreacted substances is measured as one of means for performing rapid and appropriate control of the production process. For example, when an alcohol is produced by hydration of an olefinic hydrocarbon, the alcohol separated from the reaction mixture and the unreacted olefin contain the water used in the synthesis and the organic acid used as a reaction medium as impurities. There is. The organic acid is an impurity for product alcohol, and therefore the permissible limit is set by the standard. However, as another problem, it causes corrosion of the storage container and the reaction device, and therefore it should be removed as much as possible. In order to know the content of organic acids and control the process, it is important to know the pH quickly and accurately. This pH measurement is not a problem when the sample is an aqueous solution, but is troublesome when a non-aqueous sample is used. As used herein, the term “non-aqueous sample” includes a solid sample as well as a solution of a non-aqueous solvent. The pH is originally defined as a hydrogen ion concentration index in an aqueous solution, but the hydrogen ion concentration can be considered even in a non-aqueous medium. This could be understood, for example, as the potential hydrogen ion concentration level that can occur when the sample is transferred into an aqueous medium. For the sake of convenience, the hydrogen ion concentration in such a meaning is used here by being included in the meaning of the conventional pH.
The pH in this sense often serves as an indicator of the properties of the reaction products and unreacted raw materials, and therefore its measurement is often necessary and meaningful. However, the practical measurement technique has not been established so far. The method that has been carried out so far is, for example, when an oily sample is used, the oily sample is placed in a separating funnel, and an equal volume of pure water is added to the oily funnel to shake the oily sample so that it is contained in the oil. The substance that contributes to the electrical characteristics of the aqueous solution is extracted, and the pH of the aqueous layer obtained by filtering the suspended and dispersed oil droplets is measured by, for example, a glass electrode type pH meter,
And so on. However, in such a method, (1) it is not possible to continuously measure the pH, and the state of the process that changes from moment to moment cannot be grasped quickly and accurately, and (2) it is easily affected by the atmosphere, that is, There is a problem that pH measurement value varies due to the pollution of acidic and alkaline substances such as CO ₂ , NO _X , SO _X , NH ₃ and HCl in the air, and (3) requires a considerable amount of manual labor. It was

[Problems to be Solved by the Invention]

The object of the present invention is to solve these problems and to bring the pH of non-aqueous samples in-line, i.e. during the operation of the process,
It is an object of the present invention to provide a method capable of continuous measurement without fear of variations due to air pollution or requiring human labor, thereby enabling rapid and accurate control of the manufacturing process. The invention also includes for that purpose the provision of an apparatus for use in carrying out such a method. Structure of the invention

[Means for solving problems]

The method for continuously measuring the pH of a non-aqueous sample of the present invention comprises a step of extracting pure water and a necessary diluent into a non-aqueous sample extracted from a process line to extract a substance contributing to pH in the non-aqueous sample, It comprises a step of guiding the mixed solution to a separation section that gives an appropriate residence time to separate it into an aqueous layer and a non-aqueous layer, and a step of continuously measuring the pH of the separated aqueous layer. The apparatus for continuously measuring the pH of a non-aqueous sample of the present invention used for carrying out the above method comprises a non-aqueous sample withdrawal line having a flow meter connected to a part of the process line,
And a mixing and extracting unit for extracting a substance contributing to pH in a non-aqueous sample, which is connected to the outlet side of this extraction line, and comprises a pure water supply line having a flow meter and a supply line of a necessary diluent, respectively. Connected to this mixing and extracting section, a separation section for allowing the mixed solution to stay for an appropriate time to separate it into an aqueous layer and a non-aqueous layer, and an instrument connected to this separating section for measuring the pH of the separated aqueous layer It is composed of a measuring unit which is provided so that the pH of the aqueous layer can be continuously measured.

[Action]

The measurement of the pH of non-aqueous samples is carried out in the extraction line connected to the process line and thus in a closed system. For this reason, when the sample is taken out of the system, the pressure decreases and the components that contribute to pH are volatilized, and CO _{2 in} the atmosphere is removed.
And NO _X, SO _X, without or contaminated with such NH _3, stable measurement value is obtained. Moreover, since these measurements are performed continuously within the system by only requiring the time required for separation of the water layer and the non-aqueous layer, rapid and accurate process control is possible, and labor saving is achieved. You can

Embodiment

A typical example will be described with reference to the drawings.
Is a process line in which a non-aqueous liquid flows from various processing devices such as a reactor, a distillation column, and a washing device, and a withdrawal line 3 having an area flow meter 2A for withdrawing a sample is connected to the line 1. ing. On the outlet side of this extraction line 3, a pure water supply line 4
And diluent supply line 5 are connected, and area type flowmeters 2B and 2C are similarly provided in lines 4 and 5. Reference numeral 6 is a mixed extract for mixing a non-aqueous medium as a sample with pure water and a necessary diluent to extract a pH contributing substance in the non-aqueous sample with pure water. This mixed extract 6 makes the flow of the mixed liquid turbulent. Mixing in piping
If the flow there is turbulent, a sufficient extraction effect can be expected. However, too strong turbulence may disproportionately lengthen the time required for separation in the oil-water separation unit 7 after that, so that the Reynolds number is about 4,000 to 6,000, and the flow rate of the sample and pure water and the pipe diameter are set. Select. In other words, it does not usually require a special mixing device, but depending on the properties of the sample, for example, when the sample is a highly viscous liquid or when the pressure loss in the pipe becomes excessive, it may be necessary. , Use a line mixer, or install a baffle inside the tube. The residence time in the case of in-line mixing is usually 2 to 4 seconds. As an example of mixing, when benzene is the sample to be measured and pure water and benzene are mixed at a ratio of 50 / hr, it is sufficient to set the mixing extraction section to an inner diameter of 6 mm and a length of 3 m. is there. It is preferable that the mixing / extracting section has a tube wound in a coil shape because the mixing effect is further enhanced and the installation space is reduced. Returning to the figure, reference numeral 7 denotes a water extraction / separation unit, which has a capacity such that the mixed liquid in the mixing / extracting unit 6 stays for a predetermined time and can separate the oil layer and the water layer. Reference numeral 8 denotes a pH measuring unit for measuring the pH of the aqueous layer separated by the oil / water separating unit 7, which comprises an industrial pH meter 9. It is preferable that the pH measuring unit 8 is provided with means for keeping the supply amount of the water layer constant so that the oil layer does not flow even if the interface level in the oil / water separating unit 7 changes. When the density of the non-aqueous medium, which is the sample to be measured, is considerably different from that of pure water, the oil layer and the water are favorably separated by allowing the non-aqueous medium to stay in the oil / water separation unit 7 for a predetermined time. However, when the density difference between the two is as small as 0.05 g / cm ³ or less, or when the sample to be measured has some hydrophilicity, a coalescer may be used. When mixing and extracting the sample to be measured, it is also effective to continuously add a diluent such as a hydrocarbon that does not affect the measured pH value and does not substantially change the properties of the sample from the supply line 5. is there. The specific method for measuring pH according to the properties of the non-aqueous sample is as follows. (1) In the case of BTX (benzene, toluene, xylene): In this case, the oil-water separation is performed quickly by standing, so no diluent is required, and the oil-water separation part is simple, such as a cylinder. Any device will do. The separated water is extracted from the bottom of the oil / water separation section and led to the pH measurement section. (2) Hydrophilic oils and their densities close to 1: a) It is difficult to separate oil / water from these samples, so a) BTXs that do not contain pH-contributing substances, paraffin hydrocarbons, etc. are used as diluents. And (b) avoiding vigorous mixing in the mixing / extracting section, and (c) using the coalescer as the oil / water separating section. (3) In the case of a highly viscous sample: As in the case of (2) above, a means such as using a diluent is also used. (4) For samples that are completely miscible with water: To mix samples that are completely miscible with water, such as lower alcohols, glycols, and ketones, omit the oil-water separation step and introduce the entire mixture into the pH measurement unit. Good. EFFECTS OF THE INVENTION The method and apparatus of the present invention allow the pH of a non-aqueous sample, particularly oils, to be continuously measured in-line and without being contaminated by atmospheric constituents. Precise control is possible. Further, since the oil layer separated as a measurement sample and separated by oil-water separation can be returned to the whole process, there is no loss and no separate treatment is required.

[Brief description of drawings]

The drawing is a flow chart showing a typical example of the apparatus of the present invention. 1 ... Process line 2A, 2B, 2C ... Area type flow meter 3 ... Extraction line 4 ... Pure water supply line 5 ... Diluent supply line 6 ... Mixing extraction part 7 ... Oil-water separation part 8 ... … PH measuring part 9 …… Industrial pH meter

Claims (2)

[Claims] 1. The pH in a non-aqueous sample obtained by mixing pure water and a necessary diluent with a non-aqueous sample extracted from a process line.
A step of extracting a substance that contributes to, a step of guiding the mixed solution to a separation section that gives an appropriate residence time, and separating into a water layer and a non-aqueous layer, and a step of continuously measuring the pH of the separated water layer. A method for continuously measuring the pH of a non-aqueous sample consisting of. 2. A non-aqueous sample withdrawal line having a flow meter, which is connected to a part of the process line, and a pure water supply line, each having a flow meter, which is connected to the outlet side of the withdrawal line, and the necessary Mixing and extracting section for extracting substances that contribute to pH in a non-aqueous sample consisting of a diluent supply line, connected to this mixing and extracting section, and a mixed solution is retained for an appropriate time to form an aqueous layer and a non-aqueous layer. Of the separated water layer that is connected to this separation part and the separation part
Comprised of a measuring unit with a measuring instrument for measuring pH,
An apparatus for continuously measuring the pH of a non-aqueous sample, which is characterized in that the pH can be continuously measured.