MPTL Continuous Stirred Tank Reactor (CSTR) SOP

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Standard Operating Procedure

1. Introduction

There are several CSTRs in different laboratories. Figure 1 shows one in a fume hood in the Meldrum Process Technology Laboratory (MPTL). There is another CSTR in the Unit Operations Laboratory (URL). Figure 2 is a zoomed-in view of one of the MPTL CSTRs, outside of the fume hood.

Do not proceed with testing without following all safety procedures. A basic list of safety considerations is provided in Section II of this SOP.

Figure 1. A CSTR in a fume hood. The pumps are located to the left, outside of the hood. See also Figure 2. Notice the digital display for conductivity measurement.

Figure 2. A CSTR with ancillary pumping equipment and a computer for data acquisition and control.

 

2. Safety

  1. All students must wear safety glasses when working in the lab.
  2. Never leave this equipment operating unattended.
  3. Mix all chemicals in a fume hood.
  4. All chemicals, solutions, and standards must be stored in a sealed container. The container must be labeled with chemical(s) name and concentration, operator/user’s name, hazards, and date of storage. Confirm storage location with the lab manager.
  5. All chemical containers must be sealed when not in use.
  6. All unwanted material must be placed in an appropriate container. The container must be labeled “Unwanted Material”. The label must include the chemical(s) name and concentration, the operator/user name, contact information, and hazards. If you have questions regarding labeling unwanted materials, see the sign posted above the unwanted materials table in the Senior Lab.
  7. Only pure water can go down the drains.

 

3. Equipment Description

The CSTR experiment consists of the following components.

  1. Masterflex peristaltic pumps: These pumps have a switch on the rear panel. Each pump must be set to external for the computer system to control the pumps (Figure 3).
  2. Acrylic reactor vessel, with a maximum volume of about 1 L: The reactor temperature is controlled by the heating/stir plate under the reactor vessel (refer to Figures 1 and 2).
  3. Opto22 Control System:
    1. Data are sampled every second and stored in an Excel-compatible file in a folder labeled “data” (or similar) on the Desktop of the computer used with the apparatus. See the section on viewing your data for more information. Save your data to a flash drive. The computer is not on the network.
    2. Sensorex conductivity measurement system (Refer to Figure 1 – readout devices may vary):
    3. The conductivity range is 0 to 19.9 millisiemens with a resolution of 0.01 millisiemens. Optional equipment includes pH and UV-Vis meters that you may sometimes use to assess the reaction. See the lab manager for more information.

Figure 3. Two peristaltic pumps for the CSTR system. The pump head is the fixture at the front of the pump (with a blue component for this model). Notice the tubing is fed in and out of the pump head.

4. CSTR Procedures

  1. Determine what chemicals, calibration standards, and measurements you will need to make.
  2. Determine the flow rates for your reactants.
  3. Depending on the pump specifications determine what tubing is appropriate for your flow rates. Be sure to use only Masterflex tubing. If you are unsure about which tubing to use, check with the lab manager. The smaller the inner diameter of the tubing the lower the flow rate.
  4. Pumps may be calibrated using a rotameter or a graduated cylinder/calibrated bucket and a stopwatch.
  5. Install the tubing through the peristaltic pumps. By using the same size tubing in both heads of one of the dual–head pumps you can achieve two identical flow rates.
  6. Place the reactant feed tubing into the reactor. Ensure that the other end is connected to the fitting on the top of the CSTR reactor.
  7. Ensure that the outlet of the reactor is connected to the conductivity sensor and/or feeds into a proper waste container.
  8. You will measure conductivity and use that to determine the concentration. First, confirm that the meter is correctly calibrated by running a standard. Then, measure the conductivity of known concentrations of your product (see Item 11).

Figure 4. Sensorex conductivity display.

9. Power up all equipment (the computer should be on):

      1. Switch on the power to the pumps by using the grey toggle switch located on the front panel for older pumps or the power switch in the back for newer pumps.
      2. Switch on the stir plate by pushing the knob controlling the stirring.
      3. Switch on the heating element of the plate by pushing the knob on the front.
      4. The Sensorex conductivity module does not have a switch, it is always on.
      5. Do not touch the Opto22 control hardware located behind the reactor.

10. Using the conductivity measurement system:

      1. The conductivity probe is enclosed in a tee fitting which is mounted to the 80/20 (the modular aluminum frame) next to the reactor vessel. This probe connects to the conductivity transmitter (Sensorex Model CX 100) mounted on the CSTR frame.
      2. Do not adjust the position of the probe within the tee. It is set at the correct depth and angle. Adjusting the probe will disrupt data collection.

11. Calibrating the conductivity system:

      1. Calibration only needs to be done once unless the tubing size or pump is changed.
      2. Determine the range of conductivity you want to measure.
      3. Generate the required conductivity standards. There are two parts to this:

1. You will circulate a known standard through the apparatus (following the protocols below) and confirm that the conductivity sensor is measuring correctly.

2. You will prepare individual concentrations of your reactants and circulate those through the system individually so that you can build a calibration curve of concentration versus conductivity. Follow the procedures generically outlined below.

      1. Set up a pump to pump just enough conductivity standard to fill the tubing and the tee. This volume is typically about 200 ml.
      2. Disconnect the tubing that goes from the CSTR to the conductivity sensor.
      3. Place the conductivity standard in a beaker. Place a small section of tubing into the beaker and then place the tubing in a pump head (refer to Figure 3). Connect the other end of the tubing to the bottom inlet of the tee. This will allow pumping the conductivity standard into the tee/probe assembly, filling it from the bottom.
      4. Now connect another section of tubing to the outlet at the top of the tee. Place the other end of this tubing into the beaker containing the conductivity standard. This completes the pump circuit allowing you to continuously pump conductivity standard solution through the tee/probe assembly.
      5. Once the reading of the CX 100 conductivity meter – as well as the corresponding conductivity reading on the computer display – are reading a reliable value of the conductivity standard you can stop the pump and disassemble the calibration setup. The reading should be within ~1% of the standard value.
      6. Do not attempt to adjust the calibration setting on the CX100 conductivity meter. Consult the lab manager if you feel that the meter requires calibration.
      7. Once you have confirmed the calibration of the conductivity probe, connect the bottom of the tee to the outlet of the CSTR reactor.

12. See the lab manager for assistance with other measuring devices such as pH and UV-Vis.

13. Determine the amount of feedstock you will require.

14. Mix all chemicals/feedstock dilutions in a fume hood.

15. Place your feedstock in 8-liter Nalgene containers available in the “A” lab on the shelf above the chemical storage cabinets (Senior Lab).

16. Feed the outlet stream of the system into another Nalgene container.

17. Verify that the feed and drain pumps are connected properly.

18. Weigh your solutions.

 

5. How to View and Save Data in Excel

  1. Do not try to view your data while the system is running. This will cause it to stop data collection.
  2. Save data to a flash drive after each trial.
  3. If you have any questions, ask for assistance.

If you are running one trial:

  1. Once all your required data have been collected, exit the Opto system.
  2. Open Excel, click “Open” and navigate to the correct data folder on the desktop (labeled “Data” or something similar).
  3. At the bottom of the Excel window, click on the drop-down window and select “All Files”. This will display the data files collected, organized by date.
  4. Double-click on the file you wish to open. The Text Import Wizard will open.
  5. Select Delimited. Then click Next. Then select Comma Delimited and click Next. Select the General Data format option and click Finish. The data should now be displayed in Excel
  6. Save your data to a flash drive by clicking “Save As” and selecting your flash drive as the destination. Ensure that you label your data properly and thoroughly to avoid confusion.
  7. Eject the flash drive.
  8. Follow the rest of the shutdown procedure specified in the equipment SOP (see the section labeled Shutdown, below).

 

If you are running several trials in one day:

  1. Leave the Opto system running.
  2. Open File Explorer and navigate to the correct data folder, on the desktop (labeled “Data” or something similar).
  3. Organize/sort by date if you have not already done so. Your data should appear at the top of the list.
  4. Right-click on your data file and “cut” the file (or press Ctrl X after clicking once on the file).
    • Note: this will effectively cut the data that were collected up to that point into a file and begin a new data collection (a new file will be created with the same name as the file you cut) as soon as it is cut.
  5. Paste the cut file to a flash drive and rename it with a proper label. Ensure that you are labeling your data thoroughly to avoid confusion.
  6. Eject the flash drive and save it to your personal device.

 

To open in Excel on your personal device:

  1. Open Excel. Next, click File/Open and navigate to the saved data on your flash drive or device.
  2. At the bottom of the Excel window, click on the drop-down window and select All Files. This will display the data files collected, organized by date.
  3. Double-click on the file you wish to open. The Text Import Wizard will open.
  4. Select Delimited. Click Next, select Comma Delimited, and then click Next. Select the General Data format option and click Finish.

 

6. Shutdown:

  1. Pump DI water through the system until the conductivity meter reads <100 microsiemens. Store any solution you wish to save in a properly labeled Nalgene container. Consult the lab manager regarding chemical storage.
  2. To empty the CSTR reactor, insert a piece of tubing connected to a pump into one of the holes on the top of the reactor, pump the solution/water out, and dispose properly.
  3. Label all containers, following appropriate labeling protocols.
  4. Properly dispose of any unwanted material. Consult the lab manager for guidance.
  5. Switch off the heat/stir plate.
  6. Switch off the power to the pumps. Either place the toggle switch in the center for older pumps or flip the power switch on the back of the pump for newer pumps.
  7. Do not attempt to switch off the Sensorex conductivity module.
  8. Exit the Opto control software. Do Not Shutdown the Computer.
  9. Save your data to a flash drive. The computer is not on the network