Decision Making at the bench
As chemical reaction processes which were developed at the research chemist’s lab are put into industrial use, many decisions need to be made and many factors considered. Some of the decisions relate directly to the chemistry involved while others reflect economic, environmental, politic, or other concerns. All of these factors need to be considered when making an informed decision about an industrial manufacturing process. As you read through this page, you will be asked to make a choice between the two methods of aspirin production which were presented earlier.
As industrial chemical syntheses were being developed for aspirin, both the reaction utilizing acetyl chloride and acetic anhydride were investigated to determine which would be better to use. It is important to compare these two reactions in order to understand why one was chosen over the other. Both yield the same amount of aspirin but after reading this page, you will see why one of the two reactions is better.
EXAMINING THE BENCH SCALESYNTHESIS
The first concern is that the reactions used yields the desired product. For our case, both reactions were designed to yield the same amount of raw aspirin.
If you were to choose at this point, the information given does not seem to favor one reaction or the other. Now, you will be asked to make a choice based on information provided to you. You are told that the acetyl chloride reaction proceeds at a faster rate than the acetic anhydride reaction.
Knowing this information, which reaction would you choose?
MOVING TO THE INDUSTRIAL SCALE
In order to manufacture aspirin industrially, it is vital to increase the scale of the manufacturing operation. The synthesis would not be viable if it needed to be carried out on the level of the laboratory chemists’ bench. Though some compounds can only be derived a few grams at a time, the aspirin manufacturing process can be carried out using thousands of kilograms of reactants in large mixing tanks and reaction vessels. This, of course, leads to other decisions which need to be made. In the next few sections you will be asked to make decisions based on pieces of information related to an industrial scale aspirin synthesis. By the end of this exercise, it will become apparent why one of the reactions discussed was chosen over the other.
Though there are many areas which need to be investigated in order to make an informed decision about the industrial process, we will begin with a discussion of two: the cost of the industrial synthesis and the physical properties of the materials involved in that synthesis. By following the link listed below, you will be shown data that is used by industrial experts. This information helps them better understand the situation and assist them with the decision-making process.
Before moving inot the decision process, it is important to relaize that the industrail process will be different form the bench process in many ways. First of all, the industrial process uses a solvent to dissolve the reactants and carry along the products throughout the process. In this case, both reactions will be using toluene. Next, is is necessary to know the quantity of each of the reactants. Assume that you are dealing with reactions using 400 kilograms of salicylic acid. Based on that number, you will need to use 200 liters of acetyl chloride or 400 liters of acetic anhydride to produce the desired amount of aspirin. Let us move into the two examples listed below.
Now that you have had an opportunity see how all of these different factors affect the decision making process, one last aspect needs to be considered. So far, the decision-making process has been based on only one aspect of the problem. Whether you were asked to look at coast, product purity, physical properties or any other aspect, it is important to realize all of these need to be considered when an informed overall decision is made. The link below looks at an integrated decision-making process which considers many more aspects of the aspirin manufacturing process than has been discussed so far.
MORE TO THINK ABOUT.
In the final analysis, engineers work to find a process which allows for the least waste and impact to the environment while reaching the highest efficiency and product yield. The industrial process differs from that used in the lab in both scale and procedure. It is important to remember that as the reaction is performed on a larger scale, other considerations become important. No longer are there flasks, heating baths, or stirring rods. Instead, large and costly equipment must be used. Also, as reactant and products need to be moved between and among processes to increase purity, other decisions need to be made. In the end, just the fact that a reaction works does not mean it is a viable means of producing a desired product on the industrial scale.
Only after everything has been evaluated and judged, can the best decision be made. The remainder of the case study will look at how environmental concerns affect the decision-making process. In addition, some of the methods and tool used by the experts in industry who are making these types of decisions will be discuss and presented.
Goto anywhere in the case study