Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Inorganic carbon containing
Patent
1988-08-11
1990-04-10
Shine, W. J.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Inorganic carbon containing
585467, B01J 2304, B01J 27232
Patent
active
049161008
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a catalyst system and procedure for selective alkylation of toluene with propylene.
There are two main methods to industrially produce alkylbenzene. One is Friedel-Crafts-catalyzed alkylation of the ring in aromatic compounds, which has the drawback that it tends to lead to polysubstitution (ring substitution) and, thereby, to a wide product range. The other method is to use base catalysts, such as Li, Na or K metals, in the reaction between aromatic hydrocarbons and olefines. Alkali metals may be used as such, or dispersed on the surface of an inorganic carrier substance. An efficient side chain alkylating catalyst is obtained when metallic sodium is dispersed on the surface of dry potassium carbonate. When a basic alkali metal catalyst is used, alkylation takes place selectively in the side chain of the alkylaromatic and no ring substitution occurs, as is the case with acid Friedel-Crafts catalysts. The drawback is comparatively low selectivity of the alkali metal catalyst to aromatics and its tendency to produce various isomers of alkylbenzene, which have to be separated subsequently. Aliphatic dimers are also produced, although these are easily separated from the alkylbenzenes by distillation.
The selectivity of an alkyl metal catalyst is lowered at the preparation stage by oxygen and water residues in the K.sub.2 CO.sub.3 carrier, whereby oxides and hydroxides are formed from part of the active metal. It is for this reason necessary to dry the carrier well at 120.degree.-150.degree. C. in vacuum for 10-20 hours and to prepare the catalyst in an inert atmosphere or in vacuum.
Martens et al. (Scientific bases for the preparation of heterogeneous catalysts, 4th Internat. Symp., Belgium, 1986, F3.1-3.11, and Preparation and catalytic properties of ionic sodium clusters in zeolites, Nature, 315, (1985), p. 568-470) have suggested that sodium azide (NaN.sub.3) is decomposed at 350.degree.-400.degree. C. to three different modifications: metallic sodium (Na.sub.x.sup.o) crystalline metal clusters (Na.sub.y.sup.o) and ionic clusters (Na.sub.4.sup.3+). When NaN.sub.3 was in this way thermally dispersed on the surface of a zeolite, a basic catalyst was thus obtained which was appropriate for use in isomerizing cis-2-butylene. Of azide and carrier substance either a mechanical mixture was prepared or a methanol suspension, from which the azide was decomposed in a tubular reactor to become sodium on the surface of the carrier.
SUMMARY OF THE INVENTION
The object of the invention is to utilize a decomposition reaction as described for preparing a catalyst for use in the toluene alkylating reaction.
The catalyst system of the invention is thus characterized in that it contains metallic sodium which has been thermally decomposed from a compound containing sodium, on the surface of solid K.sub.2 CO.sub.3.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graphical illustration of decomposition of sodium azide as compared with the NaN.sub.3 /K.sub.2 CO.sub.3 combination in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The decomposition of sodium azide and of the NaN.sub.3 /K.sub.2 CO.sub.3 mixture was gravimetrically studied, to begin with. (The results of thermoanalysis are shown in FIG. 1.) The graphs reveal that sodium azide decomposes when pure at 400.degree. C. explosively. Mixing with K.sub.2 CO.sub.3 makes the decomposition more leisurely and causes it to take place at a somewhat higher temperature. The decomposition to nitrogen and metallic sodium proceeds according to equation 1: catalyst transfers are avoided and the risk of deactivation of the alkali metal catalyst, sensitive to air and moisture, will be less. It is also an advantage that no readily inflammable alkali metals, oxidizing in air, need be handled.
In the way above described, an alkali metal catalyst was prepared in which NaN.sub.3 was thermally decomposed to lodge on the surface of solid potassium carbonate (K.sub.2 CO.sub.3). Furthermore, an alkali metal
Ali-Hokka Aila
Knuuttila Pekka
Neste Oy
Shine W. J.
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