Crude oil, a complex mixture of hydrocarbons, is pumped from the ground by thousands of "pump jacks" located all over Alberta.

Crude oil is of various types. Read pages 386-387 in the textbook to learn more about the types of crude oil, the property that determines its grade, and the refining process.

The refining of crude oil involves both physical processes and chemical processes.

1. Physical Refining Processes

   
   Fractional distillation and solvent extraction are two of the physical processes used to refine crude oil.

   1. Fractional Distillation
      
      This physical process separates molecules using their boiling points.
      
      In a furnace, crude oil is heated to 500°C. At this temperature, most components of the crude oil will vaporize. The vapours then rise up the fractionation tower, which is very hot at the bottom and cooler at the top. As the vapours rise, they cool and condense into liquids. Because different molecules have different boiling points, they condense at different temperatures. In other words, the various substances condense at various levels in the tower. As each substance condenses, the liquid is collected by a tray. Each liquid separated in this manner is known as a fraction. 
      Recall from Chemistry 20 that smaller molecules have fewer electrons and thus weaker London Forces.  This results in a lower boiling point. Therefore, these smaller molecules rise higher in the tower and are collected at the top where the temperature is cooler. Larger molecules, which have a greater number of electrons (and thus stronger London forces), have higher boiling points and, therefore, condense closer to the bottom of the fractionation tower where the temperature is higher.
      
      Use the flash presentation "Fractional Distillation" to enhance your understanding of the principles and processes involved in oil refining. As you move your mouse over the alternatives in each question, a pop-up window will appear to allow you to self-score and see where you chose incorrectly.
      Complete only steps 1 to 10 at this time. You will complete the other steps later in this lesson.
      

      ---

      Animation - Fractional Distillation
      
      
      
   2. Solvent Extraction
      
      Solvent extraction is a physical process in which a solvent is added to a mixture to selectively dissolve and remove an impurity or to separate some useful product. In other words, it is a procedure used to separate compounds based on differences in their solubility. For instance, a given mixture may contain both polar and non-polar compounds. If you want to separate the polar compounds, you could add a polar solvent. This is because like dissolves like. The polar solvent dissolves the polar compounds but not the non-polar compounds.

Check Your Understanding

Go to your textbook and complete Practice questions 2, 4 and 6 on page 388.

Check your answers by clicking on the link beneath.

1.  
2. Chemical Refining Processes
   
   
   1. Cracking
      
      Cracking is a process in which heat or a catalyst is used to break larger molecules into smaller molecules.
      
      
      
      Fig. 2
      
      
   2. Hydrocracking
      
      Hydrocracking is similar to cracking, but it involves the addition of hydrogen. During this process, no coke is produced. This is an improvement over cracking because coke is an undesirable side product.
      For example:
      
                   
      
      Fig. 3
      
      
   3. Alkylation
      
      Alkylation converts a straight chain alkane into a branched alkane. This process is used to increase the octane rating of gasoline.
      
      
      Fig. 4
      
      
   4. Catalytic Reforming
      
      This chemical process involves converting alkanes into aromatic molecules. The reason for this conversion is that aromatic gasoline molecules combust better in car motors.
      
      
      Fig. 5
      
      
      
      

Check Your Understanding

Go to your textbook and complete "Practice" questions 8, 9, 10, 11, and 12 on page 391.

Check your work by clicking on the link below.