title: A methanol only route to acetic acid and methyl acetate
Creators: name: Ormsby, Graham
Publisher: name: University of Glasgow
Year: 2008
Subjects: subject: Acetic acid, methanol, chemistry.

description: Methanol carbonylation to produce acetic acid is a reaction of industrial interest and is currently performed via homogeneous catalytic routes in the Cativa and Monsanto processes using iridium and rhodium complexes respectively. Whilst these processes produce acetic acid with high selectivity, the use of halide promoters is required. Due to this corrosive nature, the development of a catalyst system without the need for promoters is of significant commercial interest. Studies demonstrate that copper mordenite is a potential candidate. The present project concerns the production of acetic acid and methyl acetate in the absence of a halide promoter via a methanol only route. The methanol is firstly partially decomposed to form CO and H[2] over a methanol decomposition catalyst and in a subsequent step the unconverted methanol is carbonylated using the copper mordenite catalyst to form acetic acid and methyl acetate. Both catalysts are contained within one reactor. The experimental work undertaken has focussed on three main objectives: (i) study of methanol decomposition over a range of materials under directly comparable conditions, (ii) methanol carbonylation using copper mordenite under various feed conditions containing H2 and (iii) combination of methanol decomposition catalysts with the copper mordenite in a single reactor. The behaviour of copper methanol synthesis catalysts and palladium based catalysts in methanol decompoition is consistent with the literature with palladium being the more selective for CO formation. The rate of CO formation over copper is lower due to the formation of methyl formate by-product. Raney nickel decomposed methanol with CH[4] being a side-product. The most active catalyst for CO production was a NiB alloy, formed from the reduction of nickel acetate with sodium borohydride. A series of molybdenum carbide and nitride catalysts were also investigated due to the literature reports that these materials often behave like noble metals. All carbide and nitride phases were active in methanol decomposition. CH[4] and CO[2] were observed by-products and in general it was found that they behaved like Ni based catalysts. Methanol carbonylation studies over copper mordenite demonstrate that acetic acid is a minor product with methanol to olefin and methanol to gasoline chemistry occurring. In addition, DME is formed from the dehydration of methanol. The presence of H2 in the feedstream influences the rate of acetyl formation. A CO/H[2] feed ratio of 4 is optimal whilst a further increase in H[2] partial pressure lowers the acetyl formation rate. Acetic acid and methyl formate are produced when the copper mordenite catalyst is combined with methanol decomposition catalysts but the selectivity is low. The choice of methanol decomposition catalyst combined with copper mordenite influences the formation of acetyls. In addition it was observed that physically mixed catalyst beds produce lower yields of acetyls whilst the acetyl yield is increased by separating the two catalyst components.