An exploration towards a more sustainable process for dimethyl naphthalene-2,6-dicarboxylate over acidic zeolites

Abstract

This thesis describes the challenge to apply a breakthrough in the synthesis of acidic zeolitic catalysts in the development of a sustainable process for dimethyl naphthalene-2,6-dicarboxylate. BiModal POrous Materials (BIPOMs) are zeolitic materials, which provide highway access to confined catalytic sites, thus allowing selective reactions with high rates. Much attention was paid to the selection of a suitable model system. It should be representative for a real existing industrial problem with sustainability, while at the same showing the potential of the new catalytic approach. Diisopropylation of naphthalene was chosen as a model system. There are numerous claims in literature for shape-selective diisopropylation of naphthalene with H-mordenite, but the reaction rate is too low to allow industrial application. Furthermore Kureha operates an industrial process for the production of a mixture of diisopropylnaphthalenes, and finally SRI has published a process cost study on Amoco technology leading to 2,6-dimethylnaphthalene carboxylate. Contrary to the claims in literature, the reaction was not shape selective with H-mordenite, but controlled by the relative stability of the isomeric diisopropylnaphthalenes. However the applicability of the BIPOM concept turned out to be very successful. The BIPOM catalyst not only showed a >200 times increase in yield compared to its parent normal zeolite, but also showed a significant yield increase compared to the best available zeolitic catalyst (H-USY). Explorative crystallisation experiments indicate that the production of pure 2,6-diisopropylnaphthalene seems possible. Thus a new process for the industrial production of dimethyl naphthalene-2,6-dicarboxylate was designed and evaluated. The base case scenario, though slightly better than the Amoco-technology, is still not economically attractive. However in close analogy to the existing Kureha process, the higher yield scenario seems realistic, leading to an ROI of ~ 12%, close to the limit of an economically attractive process. The final conclusion of this work is that violation of the atomic efficiency, by inherently loosing 4 carbons out of 6, cannot be compensated by an otherwise excellent catalytic concept.