Method for preparing a carbamate, a catalyst applied in the method, a method for preparing the catalyst and use thereof
The present invention pertains to a novel method for preparing a carbamate, in which the method comprises reacting an aliphatic substituted urea and/or its derivatives, with a hydroxyl group containing compound to obtain a carbamate. In addition, the present invention provides a novel catalyst which is suitable for catalyzing the reaction to form a carbamate, and a method for preparing the novel catalyst. The method of the present invention for preparing a carbamate does not involve the application of carbon monoxide which is toxic, and the reaction conditions are relatively mild with high catalytic activity, high reaction selectivity of the catalyst, and a relatively short reaction time. Furthermore, the catalyst is separated from the reaction system and reused easily, which will facilitates scale up and industrial application.
1. A method for preparing a carbamate, comprising (1) reacting
(a) an aliphatic substituted urea and/or a derivative thereof having the general formula (I):
R 1 R 2 N—CO—NR 3 R 4 (I)
wherein:
R 1 , R 2 , R 3 and R 4 are each independently selected from the group consisting of a hydrogen atom, an aliphatic group or a derivative thereof, a cycloaliphatic group or a derivative thereof, and an araliphatic group or a derivative thereof;
with
(b) a hydroxyl group containing compound having the general formula (II):
R 5 (OH) n (II)
wherein:
R 5 is independently selected from the group consisiting of an aliphatic group or a derivative thereof, a cycloaliphatic group or a derivative thereof, an araliphatic group or a derivative thereof, and an aromatic group or a derivative thereof, and
n represents 1, 2, 3 or 4;
in the presence of
(c) a catalyst comprising a catalytically active component and a catalyst support with said catalytically acid component being carried by said catalyst support, wherein said catalytically active component comprises a transition metal oxide and/or a composite of a transition metal oxide, wherein:
(i) said transition metal oxide corresponds to the general formula:
AO x ,
wherein:
A is a transition metal element, and
x represents a number within the range of 0.5 to 40;
(ii) said cormposite of a transition metal oxide corresponds to one of the general formulas:
AO x —BO y
or
AO x —BO y —CO z ,
wherein in each formula:
A, B and C each independently represent a transition metal element, and
x, y and z each independently represent a number within the range of 0.5-4;
wherein said transition metal element is selected from the group consisting of vanadium, chromium, molybdenum, tungsten, manganese, iron, nickel palladium, patinum, copper, cadmium, mercury, titanium, lanthanum, cerium, neodynium, ytterbium, praseodymium, promethium, samarium, gadolinium, terbium, holmium, erbium, thulium and lutetium;
and wherein said catalyst support:
(i) comprises a material which is selected from the group consisting of silica gel, Al 2 O 3 , SnO 2 , TiO 2 , MgO, ZnO, ZrO 2 and SiO 2 ,
(ii) the average diameter of said catalyst support ranges from 0.01-10 mm,
(iii) the pore volume of said catalyst support ranges from 0.01-2 ml/g, and
(iv) the specific surface area of said catalyst support ranges from 1 to 2000 m 2 /g;
thereby forming a carbamate having the general formula (III):
(R 1 R 2 N—CO—O) n R 5 (III)
wherein:
R 1 and R 2 are each independently selected from the group consisting of a hydrogen atom, an aliphatic group or a derivative thereof, a cycloaliphatic group or a derivative thereof, and an araliphatic group or a derivative thereof,
R 5 is independently selected from the group consisiting of aliphatic group or its derivatives, cycloaliphatic group or its derivatives, araliphatic group or its derivatives, and aromatic group or its derivatives, and
n represents 1, 2, 3 or 4.
2. The method of claim 1 , wherein (a) said aliphatic substituted urea comprises dicyclohexyl urea.
3. The method of claim 1 , wherein the molar ratio of the hydroxyl groups present in (b) said hydroxyl group containing compound to (a) said aliphatic substituted urea and/or derivatives thereof ranges from 1:1 to 200:1.
4. The method of claim 3 , wherein, the molar ratio of the hydroxyl group present in (b) said hydroxyl group containing compound to (a) said aliphatic substituted urea and/or derivatives thereof ranges from 1:1 to 4:1.
5. The method of claim 1 , wherein the reaction temperature ranges from 100 to 300° C.
6. The method of claim 5 , wherein the reaction temperature ranges from 160 to 240° C.
7. The method of claim 1 , wherein said transition metal element is selected from the group consisting of titanium, lanthanum and cerium.
8. The method of claim 1 , wherein, the weight ratio between said catalyst and said aliphatic substituted urea is equal to or less than 1:1.
9. The method of claim 8 wherein, the weight ratio between said catalyst and said aliphatic substituted urea ranges from 0.01:1 to 0.3:1.