ABSTRACT
Daniel J. Ostgard,1 Felix Roessler,2 Reinhard Karge2 and Thomas Tacke1
1Degussa AG, Exclusive Synthesis & Catalysts, Rodenbacher Chaussee 4
D-63457 Hanau, Germany
2DSM Nutritional Products Ltd, Postfach 3255, CH-4002 Basel, Switzerland
dan.ostgard@degussa.com Abstract Vitamin B1 can, among various other synthetic routes, be prepared via the key intermediate 5-cyano-pyrimidine (698-29-3) followed by the selective hydrogenation of its nitrile function with a base metal catalyst to the corresponding primary amine “Grewe diamine”. The selectivity of this hydrogenation is typically controlled by the addition of ammonia and this usually increases the Grewe diamine selectivity up to 96.4%. However the current commercial conditions demand that one improves this selectivity to over 99%. It was found that one could improve the selectivity of the activated nickel catalyst by treating it with formaldehyde, carbon monoxide, acetone or acetaldehyde prior to its use. The most productive treatment was with formaldehyde leading to a Grewe diamine selectivity of 99.7% and carbon monoxide was the next best modifier giving a selectivity of 98.8% for this primary amine. The other modifiers were clearly less effective. The comparison of the various modifiers and their performances for nitriles other than pynitrile, have indicated that the efficacy of the modifier is dependent on its ability to restructure and decompose on the catalytic surface leading to the formation of more selective active sites. Introduction Vitamin B1 (a.k.a., thiamin and aneurin) serves a number of essential metabolic functions such as the conversion of fats and carbohydrates to energy as well as for the maintenance of healthy nerves and muscles (1,2). Vitamin B1 occurs naturally in small amounts in many foods, however it is not stable under conditions of heat and in the presence of alkali, oxygen and radiation (e.g., sunlight). Hence, a considerable amount of the naturally occurring vitamin B1 is destroyed during food preparation (2,3,4). Since the body has a high vitamin B1 turnover and is not able to store it very well, the use of vitamin B1 supplements (especially for diets high in carbohydrates and physically active people) is advisable for the avoidance of disorders such as Beriberi and the Wernicke-Korsakoff syndrome. Vitamin B1 is produced on an industrial scale in multiple step syntheses (1) meaning that even the smallest improvement in the yield of one of the steps can have a large impact on the overall economics of this product. This is particularly true for the mid-to-later steps
such as the hydrogenation of pynitrile to the Grewe diamine that is processed further to vitamin B1 (5). The yield of this hydrogenation could be improved from 96.4% to 99.7% by the use of newly developed modified activated Ni catalysts (6). This work explores the reasons for this improvement and use of this new catalyst for the hydrogenation of other nitriles. Results and Discussion Table 1 shows the reaction conditions of the tests performed here and Table 2 describes the modifications of these catalysts with different modifying agents. The mechanism of pynitrile hydrogenation and the formation of the secondary amine is depicted in Figure 1 and Figure 2 displays the reaction data for the hydrogenation of pynitrile over activated Ni (B 113 W), activated Co (B 2112 Z) and Ni/SiO2 catalysts with and without the formaldehyde treatment. The reaction results seem to be very similar for all of the catalysts before formaldehyde treatment and even though all of the catalysts are considerably better after this treatment, the activated Ni catalyst observed the greatest improvement and overall result.
