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Effect of reaction solvent on the hydrogenation of isophthalonitrile for meta-xylylendiamine preparation.


Meta-xylylenediamine (MXDA) is an aliphatic diamine having benzene ring produced from isophthalonitrile (IPN). MXDA is used as an epoxy resin hardener directly and is useful as a chemical intersolvent in the plastic and polymer fields. MXDA has been manufactured by ammoxidation of pure meta-xylene into isophthalonitrile, followed by hydrogenation of the nitrile in the presence of ammonia using a nickel catalyst or other metallic catalyst under high temperature and pressures. In this hydrogenation reaction, optimum reaction conditions are crucial to produce a high grade of MXDA because of the formation of undesirable products resulting from a partial hydrogenation, a polymerization or cleavage of the product (Nakamura et al., 2003). For this reason, IPN was hydrogenated in the presence of ammonia and reaction solvent to minimize the side reactions (Haldar and Mahajani, 2004). In the hydrogenation of aliphatic and aromatic nitriles, aromatic hydrocarbons, aliphatic alcohols, aliphatic hydrocarbons, dimethlyformamide and dioxane were employed as a reaction solvent. Indeed, some processes to produce MXDA were disclosed using m-xylene, pseudocumene, mesitylene, ethylbenzene, methylpyridine, benzonitrile, m-tolunitrile, isopropanol, MXDA and cyanopyridine (Kurek, 1984; Nakamura et al., 2002; Otsuka et al., 2003; Takamizawa et al., 2001). However, ammonia consumption was significant to avoid amine cleavage with the resulting formation of by-products by vaporizing solvents and ammonia.

In our previous work (Chae et al., 2006), we found that the solvent is a crucial factor to determining catalytic performance in this reaction. In this study, various reaction solvents are studied for the hydrogenation of IPN over a Ni-based commercial catalyst. A systematic study including kinetics to understand the effect of reaction conditions on the performance of hydrogenation reaction was conducted, and the results of this study are discussed in this paper. Furthermore, 1-methylimidazole was compared with some conventional solvents under various reaction conditions to investigate its potential as an alternative solvent to commercial process.


Isophthalonitrile (TCI, Japan, 98%) and benzyl ether (Aldrich, 99%) as an internal standard material were used as a reactant. For an organic solvent, mesitylene (Aldrich, 98%), benzyl ether (Aldrich, 98%) and isopropanol (Aldrich, 99%) and 1-methylimidazole (Acros, 99%) were used for IPN hydrogenation. A commercial Ni based catalyst (Metalyst[R], Degussa) containing Cr, Fe, Mo as promoters was used in this reaction. Hydrogenation experiments were performed in a 100 mL stainless steel batch reactor (Parr Instrument Co. Moline, IL) system. Initially, IPN, the catalyst and the organic solvent were added to the reactor. In all reactions, 0.03 mol of IPN was used and other components were varied with reaction conditions. The reactor was then heated to the reaction temperature, with stirring for 30 min to dissolve IPN completely. Ammonia was then added to the reactor. When the reactor reached the set temperature, hydrogen was introduced to the required set pressure. At the end of the reaction time (5 h), the reactor was cooled to room temperature and slowly vented. The products were collected by every 30 min and then analyzed using a gas chromatograph (Hewlett-Packard, 6890). The GC column used for separation was a Supelco Petrocol DH capillary column (50 m ??0.1 mm ??0.1 m). Initial qualitative identifications of the products were accomplished with the help of a gas chromatograph (Hewlett-Packard, 5890 Series II) equipped with a mass spectrometer (Hewlett-Packard, 5972 Series II). Quantification of the products was obtained by an internal standard method using a multipoint calibration curve. The solubility of IPN to the solvent was measured directly to compare the solvents used. The solvent was added to the beaker and then put magnetic stir. After the temperature of the solvent was fixed, each 5 mg of IPN was added stepwise and mixed until precipitate appeared.


Hydrogenation experiments were carried out in the temperature range of 80~140[degrees]C to investigate the effect of reaction temperature on the catalytic activity under various reaction solvents. The conversion of IPN was 100% regardless of reaction temperature in the range, even though duration to react IPN completely was different, higher temperature, faster conversion. The influence of reaction temperature under identical reaction conditions on MXDA yield is shown in Figure 1. In all reaction temperature ranges, the catalytic performance for MXDA yield over 1-methylimidazole outperformed the other reaction solvents. The result is mainly attributed to the high solubility of IPN and a high boiling point. From the IPN solubility measurement as presented in Table 1, it is observed that 1-methylimidazole possesses a much higher dissolving capacity than the others. Moreover, its relatively high boiling point can achieve a high MXDA yield by avoiding ammonia vaporization. Given the solvents with a lower boiling point, mesitylene (163[degrees]C) and 2-propanol (82[degrees]C), the MXDA yield decreased with reaction temperature. This trend is quit different from the other solvents with a higher boiling point, 1-methylimidazole (198[degrees]C) and benzyl ether (298[degrees]C); the MXDA yield increased with the reaction temperature until about 120[degrees]C.


In this reaction, 3-Methylamino benzonitrile (3-MAB) was identified as a main by-product as illustrated in Table 2. This is attributed to the amine cleavage in Isophthalonitrile (IPN) hydrogenation. Moreover, the formation of Benzylamine and 3-Methylamino benzonitrile is due to the hydrogenation of benzonitrile and m-tolunitrile as impurities in the feed, respectively. However, the concentration of those compounds was trivial. With increasing MXDA yield, the amount of 3-MAB decreased proportionally. Interestingly, with further increased temperatures, the MXDA yield over mesitylene and isopropanol was decreased due to not only amine cleavage but also the formation of bulky molecules by polymerization (see Table 2).

The effect of pressure on the MXDA yield with various reaction solvents under reaction temperature showing maximum MXDA yield respectively is shown in Figure 2. For the reaction, the pressure was maintained by hydrogen. Thus, the pressure in the system is directly proportional to the concentration of hydrogen. The availability of hydrogen should affect the extent of catalytic activity of a hydrogenation reaction. Over all reaction solvents except isopropanol, the MXDA yield increased rapidly with increasing pressure from 600 to 1000 psig. However, the effect of pressure diminished on the MXDA yield above 1000 psig. Under lower pressure conditions, a partial hydrogenation appeared to prevent the formation of MXDA. Indeed, a higher amount of 3-MAB was detected in the condition. The effect of pressure over isopropanol was not observed significantly in this range.



As discussed above, the higher concentration of ammonia can prohibit the cleavage of the amine group and, moreover, minimizes the formation of amine polymers. Thus, the high amount of MXDA was obtained in the presence of higher ammonia concentration as shown in Figure 3. The result indicates that the excess of ammonia is necessary to operate efficiently as the perfecting agent. Interestingly, the amount of ammonia spent over 1-methylimidazole was fairly low compared with other processes (Kurek, 1984; Nakamura et al., 2002; Nakamura et al., 2003; Otsuka et al., 2003; Takamizawa et al., 2001). This can be a significant advantage for the commercialization of this process considering ammonia cost.

The effect of temperature on IPN consumption and MXDA yield with time on stream over 1-methylimidzaole was investigated to determine the reaction rate constant as shown in Figure 4. It was found that the rate of reaction is independent of the feed concentration. This means that this reaction is of zero order; conversion is proportional to time and the reaction rate is directly dependent on the reaction temperature. Over 1-methylimidzaole, the reaction rate and MXDA yield increased with increased temperature. However, a different trend was observed over isopropanol as shown in Figure 5. With increasing temperatures, the reaction rate increased, but the MXDA yield decreased. This is because of the higher amount of by-products formed under the conditions as discussed above. It should be noted that the MXDA yield was hardly changed after the reaction was completed (see Figures 4 and 5).



The rate of IPN hydrogenation was determined under various reaction conditions to investigate the reaction kinetics. The reaction rate was significantly affected the reaction temperature. The temperature dependence of the logarithm on the reaction rate versus the inverse of the temperature is shown in Figure 6 and the estimated rate constant values, activation energy and frequency factor are illustrated in Table 3. The activation energy is around 30.0 kJ/mol regardless of reaction solvents. However, the frequency factor is varied with reaction solvents; 1-methylimidazole shows the highest value and benzyl ether shows the lowest value. Under zero order reaction, the frequency factor is directly proportional to the reaction rate. Indeed, with increasing the amount of the catalyst, the reaction time was reduced proportionally. However, the final yield of MXDA was hardly changed regardless of the amount of catalyst (see Figure 7). The result also indicates clearly this reaction is zero order.




The effect of reaction solvents on hydrogenation of IPN to MXDA was studied over Ni based catalyst. In this reaction, 1-methlyimidazole was shown to outperform the other organic solvents in terms of MXDA yield. This better performance is believed to be a result of higher IPN solubility and the boiling point of 1-methlyimidazole. Moreover, the amount of ammonia spent in this study using 1-methlyimidazole was lower than other commercialized processes. Therefore 1-methlyimidazole is an attractive new solvent to improve IPN hydrogenation process for MXDA production.


This research was financially supported by Ministry of Commerce, Industry and Energy of Korea (2M16450).

Manuscript received March 10, 2007; revised manuscript received May 15, 2007; accepted for publication May 16, 2007.


Chae, T. Y., S. W. Row, K. S. Yoo, S. D. Lee and D. W. Lee, "Hydrogenation of Isophthalonitrile with 1-Methlyimidazole as an Effective Solvent for m-Xylenediamine Production," Bull. Korean Chem. Soc. 27, 361-362 (2006).

Haldar, P. and V. V. Mahajani, "Catalytic Transfer Hydrogenation: O-Nitro Anisole to O-Anisidine, some Process Development Aspects," Chem. Eng. J. 104, 27-33 (2004).

Kurek, P. R., "Preparation of Xylylenediamine," U.S. Patent 4,482,741 (1984).

Nakamura, K., S. Otsuka, F. Kosuge, T. Shitara and K. Amakawa, "Method for Producing Xylylenediamine," U.S. Patent 6,476,269 (2002).

Nakamura, K., K. Amakawa and T. Shitara, "Method for Producing High Purity Xylylenediamine," U.S. Patent 6,646,163 (2003).

Otsuka, S., T. Shitara, F. Kosuge and K. Amakawa, "Method of Purifying Isophthalonitrile," U.S. Patent 6,509,490 (2003).

Takamizawa, S., N. Wakasa and T. Fuchikami, "Supported Nickel-Catalyzed Hydrogenation of Aromatic Nitriles under Low Pressure Conditions," Synlett. 10, 1623-1625 (2001).

Sung Wook Row (1), Tae Young Chae (1), Kye Sang Yoo (1) *, Sang Duek Lee (1), Do Weon Lee (2) and Yonggun Shul (3)

(1.) Clean Energy Research Center, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, Korea

(2.) Department of Chemical Engineering, University of Seoul, 90 Jeonnong-dong, Dondaemun-gu, Seoul 130-743, Korea

(3.) Department of Chemical Engineering, Yonsei University, 134 Sinchon-dong, Seodaemun-gu, Seoul 120-749, Korea

* Author to whom correspondence may be addressed.

E-mail address:
Table 1. Solubility of IPN in various solvents

Reaction solvent Solubility (g-IPN/g-Solvent)

 20[degrees]C 40[degrees]C 60[degrees]C

1-Methylimidazole 0.100 0.170 0.310
Mesitylene 0.008 0.040 0.070
Benzyl ether 0.010 0.045 0.075
Isopropanol 0.005 0.010 0.020

Table 2. Product selectivity in various solvents

Solvent Product Selectivity (%)

 80[degrees]C 100[degrees]C

1-Methylimidazole BA (a) 0.5 0.5
 3-M BA (b) 0.3 0.3
 3-MAB (c) 13.0 4.6
 MXDA (d) 86.0 94.4
 Others (e) 0.2 0.2

Mesitylene BA (a) 0.8 0.7
 3-M BA (b) 0.4 0.4
 3-MAB (c) 24.1 23.1
 MXDA (d) 74.3 75.0
 Others (e) 0.3 0.8

Benzyl ether BA (a) 0.8 0.8
 3-M BA (b) 0.6 0.5
 3-MAB (c) 55.1 36.9
 MXDA (d) 42.6 60.6
 Others (e) 0.9 1.2

Isopropanol BA (a) 0.8 0.9
 3-M BA (b) 0.5 0.6
 3-MAB (c) 25.4 34.8
 MXDA (d) 72.5 60.6
 Others (e) 0.8 3.1

Solvent Product Selectivity (%)


1-Methylimidazole BA (a) 0.5
 3-M BA (b) 0.3
 3-MAB (c) 0.4
 MXDA (d) 98.5
 Others (e) 0.3

Mesitylene BA (a) 0.7
 3-M BA (b) 0.5
 3-MAB (c) 39.7
 MXDA (d) 56.6
 Others (e) 2.5

Benzyl ether BA (a) 0.9
 3-M BA (b) 0.6
 3-MAB (c) 15.6
 MXDA (d) 81.6
 Others (e) 1.3

Isopropanol BA (a) 0.8
 3-M BA (b) 0.4
 3-MAB (c) 52.1
 MXDA (d) 38.6
 Others (e) 8.1

(a) Benzylamine, (b) 3-Methyl benzylamin, (c) 3-Methylamino
benzonitrile, (d) Meta-Xylylendiamine, (e) Heavies, 2[degrees],
3[degrees] amines resulting from condensation of 2 or more MXDAs

Table 3. Estimated value of rate constants

Reaction solvent Activation energy Frequency factor
 (l/mol) (mol/min-L)

1-Methylimidazole 30 068.4 192.7
Mesitylene 30 371.4 110.8
Benzylether 29 262.5 32.0
Isopropanol 30 886.0 140.9
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Author:Row, Sung Wook; Chae, Tae Young; Yoo, Kye Sang; Lee, Sang Duek; Lee, Do Weon; Shul, Yonggun
Publication:Canadian Journal of Chemical Engineering
Date:Dec 1, 2007
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