Alkylation of 2-methoxynaphthalene with propylene oxide using titanium and zirconium containing molecular sieves Original Research Article

Titanium and zirconium containing molecular sieves are active catalysts for the alkylation of 2-methoxynaphthalene (2-MN) with propylene oxide (PO). Temperatures above 423 K are necessary in order to promote the alkylation reaction. A major competing reaction that deactivates the catalyst is the oligomerization of PO that provides for deposition of these oligomers on the catalyst surface. A high 2-MN to PO ratio as well as the addition of PO in a semi-batch mode of operation help minimize the oligomerization reaction. The main reaction products are an O-alkylated product (I) and four C-alkylated products: 1-(2-methoxy-1-naphthyl)-2-propanol (II), 2-(2-methoxy-1-naphthyl)propanol (III), 1-(6-methoxy-2-naphthyl)-2-propanol (IV) and 2-(6-methoxy-2-naphthyl)propanol (V). The conversion of the limiting compound (PO) can be as high as 50% with selectivities towards the desired product V ranging from 12 to 20%. The ratio of 2,6- to 1,2-product is 1.6 for Ti-BEA, while Zr-BEA shows a value of 3.0. The shape-selective effect of the molecular sieve catalysts can be enhanced by passivation or poisoning of the outer surface of the catalyst by treatment with tetraethylorthosilicate (TEOS), tris[2-(diphenylphosphino)ethyl]-phosphine (TETRAPHOS-II), ethylenediaminetetraacetic acid (EDTA) or hydrogen peroxide (H2O2). For these cases, the 2,6- to 1,2-products ratios can reach values of up to 4. No leaching of Ti or Zr from the molecular sieve materials is observed.