Methanol homogeneous catalytic

Acetic Acid and Anhydride. Synthesis of acetic acid by carbonylation of methanol is another important homogeneous catalytic reaction. The Monsanto acetic acid process developed in the late 1960s is the best known variant of the process. 

Acetic Acid. Manufacture of acetic acid [64-19-7] by homogeneous catalytic methanol carbonylation has become the leading commercial route to acetic acid (eq. 8) (34,35). 

With the recent development of zeolite catalysts that can efficiently transform methanol into synfuels, homogeneous catalysis of reaction (2) has suddenly grown in importance. Unfortunately, aside from the reports of Bradley (6), Bathke and Feder (]), and the work of Pruett (8) at Union Carbide (largely unpublished), very little is known about the homogeneous catalytic hydrogenation of CO to methanol. Two possible mechanisms for methanol formation are suggested by literature discussions of Fischer-Tropsch catalysis (9-10). These are shown in Schemes 1 and 2. 

We are interested in homogeneous catalytic methanol synthesis because of our previous work on the Reppe reactions (11,12,13)2... 

In homogeneous catalytic systems we witnessed a new process for the production of acetic acid from methanol and carbon monoxide using a transition metal complex, thus displacing the earlier process employing ethylene as the starting material. The use of immobilized enzymes makes possible the commercial conversion of glucose into fructose. 

Oligomerization and polymerization of terminal alkynes may provide materials with interesting conductivity and (nonlinear) optical properties. Phenylacetylene and 4-ethynyltoluene were polymerized in water/methanol homogeneous solutions and in water/chloroform biphasic systems using [RhCl(CO)(TPPTS)2] and [IrCl(CO)(TPPTS)2] as catalysts [37], The complexes themselves were rather inefficient, however, the catalytic activity could be substantially increased by addition of MesNO in order to remove the carbonyl ligand from the coordination sphere of the metals. The polymers obtained had an average molecular mass of = 3150-16300. The rhodium catalyst worked at room temperature providing polymers with cis-transoid structure, while [IrCl(CO)(TPPTS)2] required 80 °C and led to the formation of frani -polymers. 

Figure 1.2 A few illustrative examples of chemicals and classes of chemicals that are manufactured by homogeneous catalytic processes. In 1.6 low-pressure methanol synthesis by a heterogeneous catalyst is one of the steps. In 1.9 it is ethylene that is converted to acetaldehyde. In 1.7 all the available building blocks may be used.

Ans. In the homogeneous catalytic process for PO the by-product is f-butanol, which has an attractive market. The atom utilization by the old route for PO is 31%. The atom utilizations by the new route are 44 and 56% for PO and f-butanol. For methylmethacrylate the atom utilization by the new route (methyl acetylene plus carbon monoxide and methanol) is 100%, and by the old route is 46% (see R. A. Sheldon, Chemtech, 1994, March, 38-47). 

All the forward reactions are important steps in commercial homogeneous catalytic processes. Reaction 2.2 is a step in methanol carbonylation (see Chapter 4), while reaction 2.3 is a step in the hydrogenation of an alkene with an acetamido functional group. This reaction, as we will see in Chapter 9, is... 

An important requirement for all homogeneous catalytic processes is that the dissolved catalyst must be separated from the liquid product and recycled to the reactor without significant catalyst loss the need is acute when the metal is as expensive as rhodium. One approach to aid this separation process is to immobilize (anchor) the soluble catalyst on a solid support in order to confine the catalyst to the reactor and overcome the need for a catalyst recycle step. A number of types of solid support have been employed to anchor rhodium catalysts for use in methanol carbon-ylation with liquid- or gas-phase reactants. These were reviewed by Howard et al. in 1993 [8] and include activated carbon, inorganic oxides, zeolites, and a range of polymeric materials. 

Several important homogeneous catalytic reactions (e.g. hydroformylations) have been accomplished in water by use of water-soluble catalysts in some instances water can act as a solvent and as a reactant for hydroformylation. In addition, formation of aluminoxanes by partial hydrolysis of alkylaluminum halides results in very high activity bimetallic Al/Ti or Al/Zr metallocene catalysts for ethene polymerization which would be otherwise inactive. Polymerization of aryl diiodides and acetylene gas has recently been achieved in water with palladium catalysts. Finally, nickel-containing enzymes, such as carbon monoxide dehydrogenase (CODH) and acetyl-CoA synthase, operate in water with reaction mechanisms comparable with those of the WGSR or of the Monsanto methanol-to-acetic-acid process. ... 

D. Forster, T. C. Singleton, Homogeneous catalytic reactions of methanol with carbon mm-oxide, J. Mol. Catal. 17 (1982) 299-314. 

Ciszewski, A. and G. Milczarek (1997). Glassy carbon electrode modified by conductive, polymeric nickel(ll) porphyrin complex as a 3D homogeneous catalytic system for methanol oxidation in basic media. J. Electroanal. Chem. 426, 125-130. 

Recent work by several research groups has shown that supercritical fluids can be superior to other solvents for several chemical processes. For example, DeSimone has demonstrated the ability of supercritical CO2 to replace Freons in the free radical polymerization of fluorinatkl acrylate monomers. 34) Noyori has shown that significant rate enhancements can be achieved in supercritical carbon dioxide relative to other solvents for the homogeneous catalytic hydrogenation of carbon dioxide to either formic acid or its derivatives in the presence of triethylamine or triethylamine/methanol respectively, (equation 1). (55-57) As discussed below, we have recently demonstrated that improved enantioselectivities can be achieved in supercritical carbon dioxide for the catalytic asymmetric hydrogenation of several enamides. 5 8)... 

Although the homogeneous catalytic activity of metal clusters has been recently the subject of a series of investigations [100], direct evidence that a real metal cluster cage is maintained as such under catalytic conditions is lacking in most cases. However, the recent work done with clusters as Ni4(CNR)7 [149], Rht(CO)ie [150,151], or Ru3(CO)i2 [152] has shown that small clusters can display, under particular conditions, catalytic activity in reactions such as cyclisation of acetylene and butadiene [149], polymerization of allene [149], oxidation of ketones [150], oxidation with O2 of CO to CO2 [150], conversion of hydrogen and carbon monoxide to methanol... 

Various both heterogeneous and homogeneous catalytic systems have been developed for methane oxidation to methanol in gas or liquid phases. Achievements in this field before 2008 are discussed in several previous reviews [10,34,60]. Inspired by the high performance of MMO, Fe- and Cu-containing zeolites were prepared to mimic catalytically active metal-oxide sites and applied for gas-phase oxidation of methane to methanol using N2O [61,62] or O2 [63,64] as oxidizing agents. However, the achieved methanol yields are rather low. 

The filled arrows in Figure 1.2 are processes either based on homogeneous catalysts or having great relevance in homogeneous catalysis. Conversion of synthesis gas into methanol is achieved by a heterogeneous catalyst, while the manufacture of acetic acid is based on the homogeneous catalytic carbonylation of methanol. Similar carbonyla-tion of methyl acetate, the ester of methanol and acetic acid, yields acetic anhydride. These reactions are discussed in Chapter 4. 

Industry uses a multitude of homogenous catalysts in all kinds of reactions to produce chemicals. The catalytic carbonylation of methanol to acetic acid... 

---