School of Chemical SciencesCollege of Liberal Arts & SciencesCollege of Engineering
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What is chemical engineering?

Is there a simple definition of chemical engineering?

Chemical engineering is the study and practice of transforming substances at large scales for the tangible improvement of the human condition. Such transformations are executed to produce other useful substances or energy, and lie at the heart of vast segments of the chemical, petroleum, pharmaceutical and electronic industries.

Chemical engineering differs from chemistry mainly in the focus on large scales. The definition of "large" is a bit arbitrary, of course, but is set mainly by the scale of useful commercial production. Typically, this scale ranges from barrels to tank cars, whereas the chemist tends to be concerned about sizes ranging from vials to beakers.

Is chemical engineering an old discipline?

Chemical engineering has been practiced in rudimentary form since at least the great Roman road-building projects that began about 300 B.C. The cement used for pavement was based on the contemporary Hellenistic formula employing lime, a calcined (heated) form of calcium carbonate. However, academic programs in the U.S. formally called "chemical engineering" — or something similar — originated only near the start of the 20th Century.

What do practicing chemical engineers typically do?

For many years, most chemical engineers took jobs in the oil or petrochemical industry. Job functions typically involved the development or operation of processes to convert oil-based feedstocks into energy or other useful chemical products ranging from fibers for clothing to lubricants to fertilizers. In recent decades, however, job descriptions have become far more diverse. Chemical engineers often develop or operate processes to create products ranging from integrated circuits to disease-fighting drugs to fuel cells. Some recent graduates use a chemical engineering bachelor's degree as a launching pad for careers as physicians or patent attorneys.

Jobs well done

Equipment used to make thin films of semiconducting materials for microelectronics applications. The methodology is called 'chemical vapor deposition,' and heating is accomplished by banks of lamps. Chemical engineers help to design and operate such equipment. Photo courtesy of Applied Materials Inc.
Equipment used to make thin films of semiconducting materials for microelectronics applications. The methodology is called 'chemical vapor deposition,' and heating is accomplished by banks of lamps. Chemical engineers help to design and operate such equipment. Photo courtesy of Applied Materials Inc.

Have you ever washed a load of your laundry with Tide detergent? Or enjoyed a slice of DiGiorno pizza? If so, you have experienced the University of Illinois' Chemical and Biomolecular Engineering program firsthand. These products and those listed below were developed by our graduates.

What will you create?

  • The world's smallest fuel cell
  • Foaming insulation
  • Tide®
  • DiGiorno® pizza
  • Wrigley® 5 gum
  • Pantene® shampoo
  • Cottonelle® tissue
  • Kleenex®
  • Cascade®
  • Lays Stax®
  • Smirnoff Ice®
  • Budweiser®
  • Liquid Clorox 2®
  • Cheerios®
  • Chocolate Altoids®

How do chemical engineers think?

The unique focus perspective of this discipline can be represented by an extension ladder, shown in the figure. The two uprights of this very useful tool represent the two primary physical foundations upon which all of chemical engineering rests: chemistry and transport. Here, "chemistry" refers to the rates and extents of transformation among substances;"transport" refers to the movement of mass, energy or momentum.

The rungs of the ladder represent the mathematical balance equations that connect chemistry and transport. The balance equations can be time-dependent or steady-state. Whatever their nature, however, these balance equations are rarely written in their own right; they are almost always written to optimize or control some variable within them. The rungs, therefore, also represent the use of balance equations for the optimization and control of useful commercial processes.

Chemical engineering embraces an enormous range of size scales in a fully integrated way — ranging from atoms to oil tankers. The figure represents this notion by three extension segments, representing length scales corresponding to the microscopic, the bench scale (or "unit operation" in the lingo of the discipline) and the factory. At the molecular level, the balance equations might incorporate variables like temperature or pressure. At the unit operation level, the key variables might be flow rate or controller gain. At the factory level, the variables might be operating cost or overall production rate.

An extension ladder can represent important aspects of how chemical engineers think.
An extension ladder can represent important aspects of how chemical engineers think.

The ladder idea provides more than a simple picture of the conceptual structure of chemical engineering, however. The idea also illustrates an important point about the use of this structure. Consider how a house painter uses a ladder. The skilled painter moves continually up and down the rungs as circumstances dictate. When carrying materials and brushes to the third floor, the painter may climb rapidly, covering a great deal of territory. When scraping the stubborn shavings from an old window, however, the painter may need to stay on one particular rung for a long time. Good painting requires a constellation of climbing skills integrated judiciously: knowing when to climb, when to descend, when to overlap ladder segments, how to lean, how to reach. Although these skills can be described and listed, they cannot be used algorithmically. Judicious ladder use requires judgment and experience (i.e., "ladder wisdom").

In a similar way, when we want to transform chemical substances, the "ladder" of chemistry/transport, balances, and optimization offers a versatile tool. The skilled chemical engineer moves continually over the span of length scales from atomic to factory-level as circumstances dictate. When designing or optimizing an overall process flow, the chemical engineer may move rapidly up and down the span of length scales. When troubleshooting a particular unit operation, however, the chemical engineer may need to stay at that level for a long time with just a few balance equations. Good chemical engineering requires a constellation of intellectual skills integrated judiciously: knowing what kind of balance equation to write, what control volume to use, what terms to neglect, when to overlap tools from different length scales, what mathematics to use. Although these skills can be described and listed, they cannot be employed algorithmically. Judicious chemical engineering requires judgment and experience (i.e., "chemical engineering wisdom"). Thus, chemical engineering has been aptly called the "liberal arts of engineering."

The ability to think quantitatively and integratively about chemistry and transport over many length scales, with wise judgment born of experience, underpins the true value-added contribution of chemical engineering. This ability probably forms part of the reason chemical engineers continue to enjoy high entry-level salaries.

What is biomolecular engineering?

The face of chemical engineering is changing, and we seek to mold that change for the common good. The department is building new efforts in areas of crucial societal need such as energy and sustainability, bioprocessing and nanotechnology.

One particularly fast-growing and important area is biotechnology. Biomolecular engineering can be considered to be a subset of chemical engineering. Biomolecular engineering narrows the focus primarily to the bottom (molecular) length scale of the ladder, and to applications drawn specifically from biological and health-oriented fields. By contrast, bioengineering — a distinct discipline — currently focuses primarily on the non-molecular aspects of the nexus between biology and engineering. Example applications include human and animal imaging, the development of medical devices, and the mechanical — as opposed to chemical — aspects of human tissue engineering.