THE CONVERSION OF N – METHYLANILINE AND N –, 2 – DIMETHYLANILINE BY USING DIFFERENT CATALYSTS

The catalytic conversion of N – methylaniline and N –, 2 – dimethylaniline in the presence of Pd – HSHM, CuFe 2 O 4 ·γ·Al 2 O 3 and vanadium – chromium – aluminium (VChA) oxide systems has been investigated. The comparative analysis of the results of the conversion of three different feedstocks with VChA catalyst shows that the xylidines, especially 2,6 – dimethylaniline is formed as a result of the methylation of aromatic amine because of the carbon in nucleus. result of conversion of N –,2 – dimethylaniline. They are 2 – methylaniline, N –, N –,2 – trimethylaniline, 2,6 -, 2,4 -, 2,3- and 2,5- dimethylanilines and trimethylanilines. The products reaction As it is the mixture of xylidines are formed as a result of the conversion of N –,2 – dimethylaniline, however N –, N –,2 – trimethylaniline is formed due to the same intermolecular conversion and trimethylanilines are formed due to the substitution in nucleus because of different intramolecular interactions during the catalytic cycle. The rate of the reaction increases due to the increase in temperature. As a of the analysis of chemical content of the products, that the conversion of N –,2 – dimethylaniline is 100% at 410°C by increasing temperature. In this case, the concentrations of 2 – methylaniline and N –, N –,2 – trimethylaniline increase, whereas the concentration of 2,6 – isomer in xylidine decreases a lot. This change is accompanied by the increase of the concentrations of the other isomers, as well as 2,4-, 2,3-, and 2,5-xylidines.


INTRODUCTION
The researches of the previous years prove that alkylates which is formed as a result of the reaction of aniline and 2methylaniline with methanol contain alkylation products due to carbon and nitrogen. Their presence, concentrations and yields vary depending on the composition of catalyst and reaction medium. A group of researchers (1,2) claim that the alkylation products due to nitrogen, as well as Nmethyl amines act as intermediates in the synthesis of toluidine and xylidine. According to the opinion of the other researchers (3,4), the alkylation of aniline and toluidine with methanol due to carbon dominates during the production of toluidines and xylidines..

EXPERIMENTALS
First, the catalytic properties of three catalysts in the alkylation reaction of aniline and 2methylaniline with methanol have been studied. These catalysts are Pd -HSHM, CuFe2O4·γ·Al2O3 and vanadiumchromiumaluminium (VChA) oxide systems.
The researches have been conducted in the continuous reactor and the volume of the immovable layer catalyst was 10cm 3 . The products were analyzed with chromatographic and spectral methods (5)(6)(7). The results of the conversions of Nmethylaniline and N -, 2-dimethylaniline in the presence of these catalysts are given in table 1 and 2. Their evaluations show that all of these catalysts are able to convert Nmethylaniline and N -, 2-dimethylaniline deeply. Pd -HSHM catalyst, which converts them 98-100%, produces complex mixture of toluidine and xylidine. More m-and pisomers are formed as a result of the conversion of both Nmethyl amine. 3-and 4-methylanilines are formed when Nmethylaniline is used and 2,4-, 2,5-and 2,3-dimethylanilines are formed when N -, 2dimethylaniline is used. The total selectivity of these isomers of produced isomers is 44%, however the total selectivity of the mentioned isomer mixture of xylidines is 48%.

RESULTS AND DISCUSSIONS
Copper/iron catalyst shows high selectivity in o-isomer production. 2methyl aniline is formed with 52.5% selectivity from conversion of Nmethylaniline whereas 2,6dimethylaniline is formed with 53.0% selectivity from conversion of N -, 2dimethylaniline. The rest of them is the other isomers of toluidine and xylidines, respectively. It should be mentioned that the conversion of Nmethylamines is low (87.0 -88.5%) in the presence of CuFe2O4·γ·Al2O3.
Among the used catalysts, VChA oxide system has unique catalytic property. The mole ratio of orto isomers (2methylaniline and 2, 6dimethylaniline) which is formed as a result of the isomerization of Nmethylaniline and N -, 2dimethylaniline in the presence of this catalyst, to the other isomers of toluidine and xylidine is 1:1.
The next stage of the research has been conducted in the presence of VChA catalyst. Following researches have been conducted in order to determine the main and by conversions in the alkylation reaction of 2methylaniline with methanol in the presence of VChA catalyst. Firstly, the role of N -,2dimethylaniline in the alkylation reaction of 2methylaniline with methanol should be determined. That is why, the interaction of N -,2dimethylaniline with VChA catalyst in alkylation reaction has been studied. The results of the conversion of N -,2dimethylaniline with the influence of temperature are shown in Table 3.

c o m
As it is obvious from the results, a number of products are formed as a result of the catalytic conversion of N -,2dimethylaniline. They are 2methylaniline, N -, N -,2trimethylaniline, 2,6 -, 2,4 -, 2,3-and 2,5-dimethylanilines and trimethylanilines. The formation of the mentioned products has been shown by the given reaction scheme.
As it is shown, the mixture of xylidines are formed as a result of the conversion of N -,2dimethylaniline, however N -, N -,2trimethylaniline is formed due to the same intermolecular conversion and trimethylanilines are formed due to the substitution in nucleus because of different intramolecular interactions during the catalytic cycle.
The rate of the reaction increases due to the increase in temperature. As a result of the analysis of the chemical content of the products, it is clear that the conversion of N -,2dimethylaniline is 100% at 410°C by increasing temperature. In this case, the concentrations of 2methylaniline and N -, N -,2trimethylaniline increase, whereas the concentration of 2,6isomer in xylidine mixture decreases a lot. This change is accompanied by the increase of the concentrations of the other isomers, as well as 2,4-, 2,3-, and 2,5-xylidines. Total 100 100 100 100 *the reaction is conducted by using the feedstock which has 2methylaniline:N -,2dimethylaniline:methanol=1:1:2:mol/mol/mol ratio.
As a result of the comparison of the alkylate content which is formed as a result of the alkylation of 2methylaniline with methanol at 380°C and the product which is formed from the catalytic conversion of N -,2dimethylaniline, a significant difference is observed. Firstly, a huge difference in the content of the produced xylidine mixture draws the attention.
The mass proportion of 2,6isomer in the dimethylamine mixture which is produced as a result of the reaction between 2methylaniline and methanol is 0.87, however the same pointer for 2,6dimethylaniline in the xylidine mixture which is formed from the conversion of N-,2-dimethylaniline is 0.50. On the other hand, unlike the alkylation reaction, trimethylaniline mixture is formed as a result of the conversion of N-,2-dimethylaniline and its concentration increases by increasing the temperature. Figure 1 shows the comparative yields of the products which are formed as a result of thermocatalytic conversion of three different feedstocks by using VChA catalyst.
2methylanilinemethanol, N -,2dimethylaniline 2methylaniline -N,2dimethylaniline methanol mixture have been taken as a feedstock and selectivity and yields of products according to 2,6and other xylidines has been analysed as comparative criterion.
As it is obvious from the results, the yields of converted and calculated according to primary aromatic amine 2,6dimethylaniline which is formed on the basis of 2methylaniline and methanol are 81,4% and 77.3%, respectively. These pointers are 12.6 and 10.2% according to the other xylidine mixture respectively.  The comparison of these data with 2,6and the other isomers of xylidine that are formed by the conversion of N -, 2dimethyaniline show a significant difference. The selectivity of 2,6isomer which is formed by the catalytic conversion of N -, 2dimethyaniline is 37.4% less, in another word, it is 43.0%, however the selectivity according to other xylidine mixture is 30.2% higher, in another word, it is 42.8%.