Raw Materials and History

In spite of this, the installation of C4-based MA processes has been slow.t The reasons for this are primarily the lack of highly selective catalysts and purification problems associated with this route. It is of interest to note that the raw material price advantage cannot always be the major reason for its choice. This is clearly reflected in recent events. In 1977, Ashland brought into production a 60 million Ib/year plant based on benzene, whereas Amoco opted for butane as feedstock in the same year.t /i-Butane and n-butenes, however, are gaining favor as the price of benzene climbs steeply ° and 

The choice of raw material can be dictated by other reasons as well. Although there is no evidence of crotonaldehyde being used as a feed commercially, it has been reported that during World War II, I. G. Farbenindustrie made MA by the oxidation of crotonaldehyde 1. This conclusion was probably based on the patent activity by that company before the war, although no evidence to this effect was found.  

It has been observed that acetylene was probably viewed as the raw material of choice for a number of chemicals—including crotonaldehyde 1 by the Germans—because acetylene could be made easily from calcium and carbon. 

A number of other chemicals have been converted to MA. There is no account of any of them being utilized commercially thus far. Among these are furfural, mixed olefins, cyclopentadiene, toluene, ter-penes, etc. So far, these have been of academic interest due to unfavorable economics and/or low selectivity to MA. Raw material supply and demand pictures are known to change rapidly and particularly so in the recent past. For the present, however, given the present economics and state-of-the-art technology, benzene and C4 hydrocarbons (n-butane in the United States) are the choice of feedstocks. In addition, there is by-product MA produced during phthalic anhydride manufacture. 

A section such as this would be incomplete if it did not refer to some interesting synthetic routes to MA. Hurd and Glass reported that pyrolysis of diglycolic anhydride 3 yielded MA. This method is of more than just historic interest since it provides a built-in potential method of introducing a label in the H, C, or O atoms. 

---