Method for producing dialkoxy alkanes by partial oxidation of lower alcohols in the presence of a catalyst based on molybdenum and iron

Abstract

The invention relates to a method for producing alkoxy alkanes by direct partial oxidation of a lower alcohol with a catalyst based upon mixed oxide containing molybdenum and at least one other metal selected from the metals that can assume a trivalent oxidation state such as Fe, Bi, Al, Cr, In, La, Sb, and/or a metal selected from Ni, Co, Cu, V, W, Ti, Ta, Nb, Mn, Sn, P.

1 . Method for producing a partial oxidation product of a light alcohol, in the form of a dialkoxyalkane, comprising oxidizing a light alcohol having from 1 to 4 carbon atoms by contact, in the gas phase, with oxygen or a gas containing molecular oxygen in the presence of a catalyst corresponding to the composition:
   Mo 12 Fe a X 1   b X 2   c X 3   d X 4   e X 5   f O x      in which X 1 =at least one element selected from the group consisting of chromium, nickel, cobalt, manganese, tin and copper; X 2 =at least one element selected from the group consisting of bismuth, antimony, tellurium, indium, aluminium and silicon, X 3 =at least one element selected from the group consisting of phosphorus, tungsten, titanium, vanadium, tantalum and niobium; X 4 =at least one element selected from the group consisting of alkaline-earth metals, lanthanum and cerium; X 5  is at least one element selected from the group consisting of alkali metals; and a, b, c, d and e are indices whose values are 1.5≦a≦8; 0≦b≦4; 0≦c≦5; 0≦d≦2; 0≦e≦2; 0≦f≦2 and x is a numerical value determined by the degree of oxidation of the other elements, and characterized in that, the partial pressure of alcohol is between 15 and 80% and the partial pressure of oxygen is between 2 and 20%, the ratio of the O 2 /alcohol partial pressures being less than or equal to 1, the remainder of the gas phase comprising a gas that is inert towards the reaction.   
     
     
         2 . Method according to  claim 1 , characterized in that the light alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, n-butanol and 2-butanol. 
     
     
         3 . Method according to  claim 1 , characterized in that the molar ratio of oxygen, calculated as O 2 , to the light alcohol is between 0.5/6 and 1/l. 
     
     
         4 . Method according to  claim 1 , characterized in that the reaction is carried out at a temperature between 10 and 400° C. and under a pressure between 50 and 1000 kPa and with a space velocity for introducing the reaction mixture between, 2000 and 100 000 h −1 . 
     
     
         5 . Method according to  claim 1 , characterized in that the light alcohol is methanol or ethanol and the partial oxidation product is methylal or acetal and the oxidation is carried out by contact in the vapour phase at a temperature of 10 to 400° C., and at a pressure of 50 to 1000 kPa. 
     
     
         6 . Method according to  claim 5 , characterized in that the concentration of the light alcohol in the gas stream is between 25 and 40%, and that of the oxygen is such that the O 2 /alcohol ratio is greater than 1. 
     
     
         7 . Method according to  claim 1 , characterized in that X 2  is bismuth. 
     
     
         8 . Method according to  claim 1 , characterized in that a catalyst is selected from the group consisting of mixed oxides of formulae: Mo 12 BiFe 3.7 Co 4.7 Ni 2.6 K 0.09 Sb 1 Si 7.9 O x , Mo 12 BiFe 3.7 Co 4.7 Ni 2.6 K 0.09 Ti 0.5 S 119 O x  and MoO 3 —Fe 2 (MoO 4 ) 3 . 
     
     
         9 . Method according to  claim 5 , characterized in that the space velocity for introducing the gaseous mixture is from 2000-100 000h −1 . 
     
     
         10 . Method according to  claim 1 , characterized in that the oxidation of the light alcohol is carried out in a fixed-bed oxidation reactor containing the catalyst. 
     
     
         11 . Method according to  claim 10 , further characterized in that an effluent is obtained at an outlet of the reactor, and subjecting said effluent to a separation step, to produce a top effluent of light gases comprising the diluent gas or gases, CO, CO 2 , nitrogen when air has been used as the gas containing molecular oxygen, residual O 2 , and a bottom effluent of dialkoxyalkane and water and further characterized in subjecting said dialkoxyalkane and water to a distillation to separate the dialkoxyalkane and the water. 
     
     
         12 . The method according to  claim 1  characterized in that the partial pressure of alcohol is between 20 and 50%. 
     
     
         13 . The method according to  claim 1  characterized in that the ratio of the O 2 /alcohol partial pressures is between 0.5/6 and 1. 
     
     
         14 . The method according to  claim 3  characterized in that the molar ratio of oxygen, calculated as O 2 , to the light alcohol is between 1.2/6 and 0.9/1. 
     
     
         15 . The method according to  claim 5  characterized in that the oxidation is carried out by contact in the vapour phase at a temperature of from 100 to 350° C. 
     
     
         16 . The method according to  claim 5  characterized in that the oxidation is carried out by contact in the vapour phase at a temperature of from 200 to 300° C. 
     
     
         17 . The method according to  claim 5  characterized in that the oxidation is carried out by contact in the vapour phase at a pressure of from 100 to 500 kPa. 
     
     
         18 . The method according to  claim 6  characterized in that the O 2 /alcohol ratio is between 1.2/6 and 0.9/1. 
     
     
         19 . The method according to  claim 9  characterized in that the space velocity for introducing the gaseous mixture is from 11 000-44 000 h −1 .