Bayer-type catalyst

The catalyst plays a crucial role in technology. Previously, catalysts were based on palladium of 1 to 5 wt% impregnated on silica with alkali metal acetates as activators. Modern catalysts employ as enhancers noble metals, mostly gold. A typical Bayer-type catalyst consists of 0.15-1.5 wt% Pd, 0.2-1.5 wt% Au, 4-10 wt% KOAc on spherical silica particles of 5 mm diameter [14], The reaction is very fast and takes place mainly inside a thin layer on the particle surface (egg-shell catalyst). 

This type of alkoxylation chemistry cannot be performed with conventional alkali metal hydroxide catalysts because the hydroxide will saponify the triglyceride ester groups under typical alkoxylation reaction conditions. Similar competitive hydrolysis occurs with alternative catalysts such as triflic acid or other Brpnsted acid/base catalysis. Efficient alkoxylation in the absence of significant side reactions requires a coordination catalyst such as the DMC catalyst zinc hexacyano-cobaltate. DMC catalysts have been under development for years [147-150], but have recently begun to gain more commercial implementation. The use of the DMC catalyst in combination with castor oil as an initiator has led to at least two lines of commercial products for the flexible foam market. Lupranol Balance 50 (BASF) and Multranol R-3524 and R-3525 (Bayer) are used for flexible slabstock foams and are produced by the direct alkoxylation of castor oil. 

Researchers at Bayer AG addressed these critical issues and developed successful solutions enabling commercial application of Julia-Colonna-type epoxidation [35-40]. Starting with optimization of catalyst preparation, a straightforward synthesis based on inexpensive reagents and requiring a shorter reaction time was developed for the poly-Leu-catalyst [35], In particular, the reaction time for the new polymerization process was only 3 h when the process was conducted at 80 °C in toluene, compared with 5 days under classic reaction conditions (THF, room temperature). Furthermore, the catalyst prepared by the Bayer route is much more active and does not require preactivation [35-40],... 

Hasegawa A, Naganawa Y, Fushimi M, Ishihara K, Yamamoto H (2006) Design of Brpnsted acid-assisted chiral Brpnsted acid catalyst bearing a bis(triflyl)-methyl group for a Mannich-type reaction. Org Lett 8 3175-3178 Hassan NA, Bayer E, Jochims JC (1998) J Chem Soc Perkin 1 3747... 

In the history of PU, some continuous processes for polyether polyol synthesis by anionic polymerisation were developed, but only at small scale (i.e., pilot plant). Tubular reactors with static mixing systems or a column with plate reactor types were used, but these technologies were not extended to industrial scale levels. The first continuous process for high MW polyether synthesis was developed by Bayer (IMPACT Technology) and is based on the very rapid coordinative polymerisation of alkylene oxides, especially PO, with dimetallic catalysts (DMC catalysts - see Chapter 5). A principle technological scheme of a polyether polyol fabrication plant is presented in Figure 4.30. 

PUs were discovered as far back as 1947 by Otto Bayer [1]. A great variety of PUs can be synthesized based on the different substiments. The reactions are also straightforward, and they can be synthesized in large scales for industrial purposes. Chemically PUs are carbamates having an —NHCOO— backbone. PUs are synthesized by reaction between diisocyanates (Dls) and polyols in the presence of a suitable catalyst (Figure 8.1(a)). The physical property of PUs may be controlled by choosing the type of polyols or isocyanates. 

Mannheim between 1921 and 1927. The first commercial plant was built at Leuna in 1927. Twelve plants of this type provided much of the aviation fuel used by Germany in World War II. After the war, the process was further developed by the U.S. Bureau of Mines. The process is essentially one of hydrogenation at high pressures and temperatures, catalyzed by an iron oxide catalyst. In Germany, the catalyst was the red mud waste from the Bayer aluminum process. See also Bergius-Pier. 

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