||Production of alcohol from carbonaceous feedstock
||Daniel, Berian John; Gracey, Benjamin Patrick
||BP P.L.C., UK
The invention relates to the process for conversion of ethanoic acid into ethanol characterized by the following steps, (a) introducing ethanoic acid and H2 into a primary hydrogenation unit in the presence of a precious metal-based catalyst to produce ethanol and Et ethanoate, (b) introducing Et ethanoate, from step (a), together with H2, into a secondary hydrogenation unit in the presence of a copper-based catalyst to produce ethanol, and (c) recovering ethanol from step (b). Thus, in the primary reactor H2 and ethanoic acid with a molar ratio of 10/1 was passed over the palladium-silver-rhenium-iron catalyst at 230° and 2.0 MPa with a GHSV of 4343 h-1 to give a product showing conversion of ethanoic acid to Et groups recoverable as ethanol was 41.9 %, of which 19.7 % was as Et ethanoate, 21.6 % ethanol, 0.4 % ethanal and 0.2 % di-Et ether and the total conversion of ethanoic acid to products was 44.7 %, the selectivity of ethanoic acid to Et groups recoverable as ethanol was 93.8 %; in the secondary reactor H2 and Et ethanoate with a molar ratio of 10/1 was passed over the copper-based catalyst at 200° and 5.0 MPa with a GHSV of 4491 h-1, the conversion of Et ethanoate to Etgroups recoverable as ethanol was 69.5 %, the selectivity of Et ethanoate to Et groups recoverable as ethanol was 99.9%.
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As bioethanol continues to be an important component of gasoline, a high–carbon efficiency, nonfermentative route becomes increasingly important. One idea under exploration is gasifying cellulosic feedstocks to biosynthesis gas (syngas) and then converting the gas to mixed alcohols. The second step, however, is problematic because the initial formation of methanol is equilibrium-limited, and very high pressures are required to obtain even modest yields of C2+ alcohols.
Inventors B. J. Daniel and B. P. Gracey disclose a technique for making ethanol from syngas with high carbon efficiency. Methanol is first made from syngas by using conventional process technology. (Whether the syngas is biobased, natural gas–based, or coal-based is irrelevant.) The methanol is then carbonylated to acetic acid, again with conventional technology.
The patent’s invention is the hydrogenation of acetic acid (HOAc) to a mixture of ethanol (EtOH) and ethyl acetate (EtOAc). The EtOAc is separated and hydrogenated in another reactor to give additional EtOH.
In the patent’s one example, hydrogen and HOAc in a 10:1 mol ratio are passed over a Pd–Ag–Rh–Fe catalyst in the primary reactor at 230 ºC, 2.0 MPa pressure, and a gaseous hourly space velocity (GHSV) of 4343 h–1. The HOAc conversion is 41.9%, of which 19.7% is EtOAc, 21.6% EtOH, 0.4% MeCHO, and 0.2% Me2O. The overall selectivity to ethyl groups that can be recovered as EtOH is 93.8%.
In the secondary reactor, hydrogen and the EtOAc from the primary reactor in a 10:1 mol ratio are passed over a copper-based catalyst at 200 ºC, 5.0 MPa, and a GHSV of 4491h-1. The conversion of EtOAc is 69.5%, and the selectivity to ethyl groups that can be recovered as EtOH is 99.9%. Overall, the selectivity to EtOH is a high 95.7% (BP PLC [London]. US Patent 8,502,001, Aug 6, 2013; Jeffrey S. Plotkin)