End-of-pipe recycling vs. cleaner process technology

Recent announcements by two major European producers of methacrylic acid addressing the environmental aspects of their approaches illustrate nicely the benefits of eliminating waste at source by implementing a clean production process versus the end-of-pipe recovery and recycle of environmentally damaging key raw materials. 

Methacrylic acid (24) and methyl methacrylate are major raw materials for the production of a variety of polymers including acrylic glass (e.g. Perspex), polymer dispersions for use as film formers in paints, and in 

Methacrylamide sulphate is then hydrolysed to methacrylic acid. The upper organic layer is distilled to yield high purity methacrylic acid. The lower waste acid layer is steam stripped to recover any dissolved methacrylic acid and the waste sulphuric acid is then disposed of or recovered. Two moles of sulphuric acid react with one mole of acetone cyanohydrin before elimination in the process. The major characteristic of the ACN process, therefore is the very large waste-acid stream. 

The construction of the sulphuric acid recovery unit was forced on ICI once the decision to continue with the acetone cyanohydrin route was made. Huge resources in financial and personnel terms were directed to 

BASF in Germany on the other hand have developed a route which they claim to be an environmentally friendly process which does not use hydrocyanic acid and does not generate waste acid in the form of ammonium sulphate [16]. Their multistage synthesis is based on two base chemicals ethylene and synthesis gas. The only byproduct is water. 

---