Chemistry of hydrocarbon compounds – Aromatic compound synthesis – By ring formation from nonring moiety – e.g. – aromatization,...
Patent
1998-09-15
2000-10-03
Griffin, Walter D.
Chemistry of hydrocarbon compounds
Aromatic compound synthesis
By ring formation from nonring moiety, e.g., aromatization,...
585410, C07C 1500, C07C 500, C07C 600
Patent
active
061275891
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE TECHNOLOGY
The invention concerns a process for the preparation of 2,6-dimethylnaphthalene in which 1-p-tolyl)-2-methylbutane and/or 1-(p-tolyl)-2-methylbutene are dehydro-cyclisized using a catalyst. 2,6-dimethylnaphthalene can be used as a starting material when making polyethylenenaphthalate.
BACKGROUND OF THE TECHNOLOGY
Polyethylenenaphthalate has very good stress- and heat-resistance. Its known preparation processes, however, have not been industrially profitable.
Polyethylenenaphthalate can be made from 2,6-naphthalenedicarboxylic acid which in turn can be made from 2,6 dimethylnaphthalene. Nowadays 2,6 dimethyl-naplthalene is separated from tar. However, in this way only small amounts can be obtained. Furthermore, the separation and purification are troublesome.
It has also been suggested that 2,6-dimethylnaphthalene is made from 1-(p-tolyl)-2-methylbutane and/or 1-(p-tolyl)-2-methylbutene by cyclization using different catalysts. The problem has especially been that in the reaction one obtains big amounts of different isomers, which are difficult to separate. Furthermore, the starting material easily polymerizes and degrades.
For instance, in the publication GB 1448136 there has been described the preparation of 1-tolyl)-2-methylbutane and/or 1(p-tolyl)-2-methylbutene using a Cr.sub.2 O.sub.3/ Al.sub.2 O.sub.3 -catalyst which has been poisoned by potassium. In the publication EP 430714 a catalyst composed of lead- and/or indium-oxide together with aluminium-oxide has been proposed.
A General Description of the Invention
Now a process according to claim 1 has been invented. Some advantageous applications of the invention are presented in the other claims.
According to the invention, 2,6-dimethylnaphthalene is made from 1-(p-tolyl)-2-methylbutane and/or 1-(p-tolyl)-2-methylbutene using a reduced vanadium catalyst. For instance, the conversion of the process is good compared to chromium catalysts, and especially the selectivity of 2,6-dimethylnaphthalene can be improved by reduction of the catalyst. Also the environmental risks for the vanadium catalyst can be considered smaller than for the chromium- and lead-catalysts.
A Detailed Description of the Invention
The vanadium catalyst used in the invention can be made using any suitable method for applying vanadium on a support. One can, for instance, use the methods of wet-or dry-impregnation or adsorption or precipitation. Among the dry-impregnation methods especially the co- and multi-impregnations provide good results both regarding the reaction and the phase transitions of the support material. After the impregnation, adsorption or precipitation the catalyst is dried at 120.degree. C. and calcinated. The calcination is carried out in an oxidizing atmosphere, especially in air, in a temperature range of 300-800.degree. C.
The preferred vanadium content is 1-15 wt-%, preferably 2-5 wt-%, calculated as vanadium per total weight of the catalyst. In the preparation the preferred vanadium source can be a water soluble vanadium compound like ammonium vanadate. The solubility of ammonium vanadate can be improved by adding oxalic acid to the impregnation solution.
The catalyst can also contain one or several modifying components. Suitable modifying components are especially the earth alkali metals, most favourably calcium and strontium, as well as the metals of the elementary group IV A, for instance zirconium. Also the sources of the modifying components can be water soluble compounds like nitrates. The molar ratio of vanadium and the modifying component should be below 4 in the case of earth alkali metals and below 2 in the case of group IV A metals.
Any suitable material can be used as a support. For this purpose especially .gamma.-, .theta.- or .delta.-aluminum oxides with a specific surface area of 50-400 m.sup.2 /g are suitable. Before vanadium is impregnated on the support one can thermally stabilize the support. The modifying agent can be impregnated on the support before or after the stabilization.
The catalyst can be reduced
REFERENCES:
patent: 3962139 (1976-06-01), Van De Moessdijk et al.
patent: 5157182 (1992-10-01), McMahon et al.
patent: 5382733 (1995-01-01), Otake et al.
Jakkula Juha
Niemi Vesa
Sahala Kari-Matti
Vahteristo Kari
Dang Thaun D.
Griffin Walter D.
Optatech Oy
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