Acetaldehyde, synthesis using metal catalysts

Acetaldehyde, synthesis using metal catalysts, 118-119 Acetoacetate esters, replacement for isocyanates, 13... 

Oxidative dehydrogenation of alcohols is a new approach in the development of industrial processes for the synthesis of aldehydes and ketones [103-105], In this regard, the technologically most suitable is the method of acetaldehyde synthesis in the presence of melted vanadium oxide, alkaline metals with promoting additives, alkaline metal sulfates or chlorides as catalysts [105], The target product yield equals 65.9% per used alcohol at 69.2% conversion. The disadvantage of the method is the relatively low yield of the target product... 

Synthesis of pyridines from acetaldehyde, formaldehyde and ammonia in the gas phase was studied with regard to metal catalyst and Si/Al ratio of the support (94CL59>. Best conditions were Si/Al = 30 to 120 and use of Tl Pb Co or Zn catalyst. The total yield of pyridines based on aldehydes was 61%. 

An example of how a reaction can be made more environmentally benign through the use of carefully selected metal catalysts is the synthesis of acetaldehyde, shown in Figure 1 (3). TTie desirable features of this reaction are the use of an aqueous medium, high reaction efficiency, and easy isolation of acetaldehyde as a... 

Miscellaneous Reactions. Sodium bisulfite adds to acetaldehyde to form a white crystalline addition compound, insoluble in ethyl alcohol and ether. This bisulfite addition compound is frequendy used to isolate and purify acetaldehyde, which may be regenerated with dilute acid. Hydrocyanic acid adds to acetaldehyde in the presence of an alkaU catalyst to form cyanohydrin the cyanohydrin may also be prepared from sodium cyanide and the bisulfite addition compound. Acrylonittile [107-13-1] (qv) can be made from acetaldehyde and hydrocyanic acid by heating the cyanohydrin that is formed to 600—700°C (77). Alanine [302-72-7] can be prepared by the reaction of an ammonium salt and an alkaU metal cyanide with acetaldehyde this is a general method for the preparation of a-amino acids called the Strecker amino acids synthesis. Grignard reagents add readily to acetaldehyde, the final product being a secondary alcohol. Thioacetaldehyde [2765-04-0] is formed by reaction of acetaldehyde with hydrogen sulfide thioacetaldehyde polymerizes readily to the trimer. 

Cyclopentadiene itself has been used as a feedstock for carbon fiber manufacture (76). Cyclopentadiene is also a component of supported metallocene—alumoxane polymerization catalysts in the preparation of syndiotactic polyolefins (77), as a nickel or iron complex in the production of methanol and ethanol from synthesis gas (78), and as Group VIII metal complexes for the production of acetaldehyde from methanol and synthesis gas (79). 

The direct production of acetic acid from synthesis gas [80] instead of methanol as feedstock has demonstrated selectivities up to 80% using rhodium fixed-bed catalysts with Group IIIA-VIIIA promoters and alkaline metals. Other C2 compounds were also formed (acetaldehyde, ethanol, and ethyl acetate) [129],... 

The reaction is catalyzed by Co carbonyls using reaction conditions in the range 200-250 bar and 175-210°C, and, when first reported, was characterized by both low yields (maximum 42%) and a spectrum of by-products including acetaldehyde, methyl formate, methyl acetate, propanol, butanol, and methane (17). Subsequently, catalytic activity toward hydrocarbonylation has been demonstrated with other metals, although Rh, usually appreciably more active than Co in other synthesis gas reactions, produces acids and esters, and ethanol only comprises a significant product at high H2 partial pressures. Methanol hydrocarbonylation may also be carried out with Fe or Ru catalysts promoted by tertiary amines, but the rates are even lower than with Co, which remains the preferred choice. The reaction rate is accelerated by the presence of promoters such as I , in which case acetaldehyde (which may also be obtained from the Co/I -catalyzed reaction of synthesis gas with methyl ketals or methyl esters (18)), comprises the major product. 

Catalyst studies have promoted attention with description of the use of iron salts to prevent ether formation during ester exchange polymerization. Model compounds have been employed to elucidate the meehanisms of metal ion catalysis in both transesterification and polycondensation reactions. A differential microcalorimeter has been used to assess the relative reactivities of catalyst systems for the poly-transesterification of bis-(2-hydroxyethyl tere-phthalate) and the relationship between the viscosity of the polymerizate and the temperature of the maximum rate of heat production has been investigated. Studies on antimony(v) compounds have indicated that their activity increases during the course of 2GT synthesis. This observation has been ascribed to the reduction of the antimony(v) compounds by acetaldehyde produced by 2GT decomposition. 

The first hydration of an alkyne was discovered in 1881 by Mikhail Kucherov, a Russian chemist from the Imperial Forestry Institute in St. Petersburg, using mercury(II) bromide as the catalyst [97] producing acetaldehyde. This reaction has been extensively applied in synthesis, although due to the toxicity of mercury compounds and the relatively low turnover numbers (<500), much effort has been done to find new catalysts. Thus, transition-metal-complexes containing Pd (II) [98], Pt(II) [99], Ru(ll) [100], Rh [101], and other metal centers [91] have been used, although in most cases the catalytic efficiency was only moderate. 

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