Caffeine Extraction, Lecture notes of Engineering

Download Caffeine Extraction and more Lecture notes Engineering in PDF only on Docsity! Chemical Engineering Laboratory CHEG 4139 Caffeine Extraction Objective: The primary purpose of this experiment is to explore the different conditions that affect caffeine extraction and identify which variables have the greatest impact on caffeine extraction. Several variables may affect the amount of and rate caffeine is extracted from coffee grinds or beans, including (but not limited to) grind size, temperature, exposure to extract solvent, packaging, and residence time. A second objective for this lab is to allow students to practice experimental design. As such, this lab includes fewer detailed instructions than other labs. Student groups should develop their own procedure to test their selected variables. Theory: Caffeine can be isolated from coffee beans through a series of solid-liquid extraction and liquid- liquid extraction techniques. Many are familiar with the solid-liquid extraction through means of making coffee. The chemical most often associated with coffee, caffeine, can by further isolated/purified from coffee through liquid-liquid extractions. As the liquid passes through the bed of coffee grinds, the caffeine moves from the solid phase to the liquid phase. Through the use of several assumptions, these results can allow the calculation of an effective mass transfer coefficient. There are several approaches to calculate this and developing the approach is the responsibility of each team. Caffeine is more soluble in dichloromethane than in water. Consequently, the addition of dichloromethane to a coffee solution containing caffeine will result in the transfer of caffeine to the dichloromethane solvent. The solvent containing caffeine can be separated from the coffee solution with a separatory funnel. The concentration of caffeine can roughly be determined using a calibration curve and a reusable quartz cuvette. The amount of caffeine extracted, however, may be dependent on the chosen methods. Safety Precautions: 1. Dichloromethane is a hazardous chemical. Review the SDS. 2. Dichloromethane should only be opened in the hood. Wear all PPE when handling dichloromethane. Silver Shield gloves will be provided to students who will work with dichloromethane extractions. These may be reused by the same students until the experiment has concluded. 3. If dichloromethane comes in contact with skin, ri nse with soap and water for 15 minutes. 4. If dichloromethane comes in contact with eyes, rinse for at least 15 minutes. 5. All waste containing dichloromethane should be disposed of in the appropriate hazardous waste container. Available Variables: Examples of variables include: size of the coffee grinds, temperature, flow rates, mass of coffee, separatory funnel inversions, size of column, coffee brand, column packing method, and additional variables selected by the group. Available Materials: Additional materials may be available. Confirm with your teaching assistant. Dark Roast Coffee Beans Medium Roast Coffee Beans Espresso Coffee Beans Column (CG-1186-06)* Column (CG-11856-10)* Burr Grinder Electric Grinder Cotton Balls Sand Spectrophotomer Reusable Quartz Cuvette Methylene Chloride Silver Shield Gloves 125 mL Separatory Funnel Face Shield Stir/Hot Plate Digital Thermometer Ring Stands Clamps Flowmeter Gear Pump Drive Tubing Balance Calipers *Glassware from ChemGlass. Product details available through their online catalog. Figure 1. Solid-Liquid Extraction Set Up. Hot water bath and flowmeter connected by a gear pump drive. Pro Tips: 1. To expedite sample collection, mark 15 mL on the Erlenmeyer flasks prior to starting sample collection. 2. It takes a good amount of time for the feed tank contents to heat to the desired temperature. Fill the tank and start heating as soon as possible.