Higher alcohols are important compounds with widespread applications in the chemical, pharmaceutical and energy sectors. Currently, they are mainly produced by sugar fermentation (ethanol and isobutanol) or hydration of petroleum-derived alkenes (heavier alcohols), but their direct synthesis from syngas (CO + H2) would comprise a more environmentally-friendly, versatile and economical alternative. Research efforts in this reaction, initiated in the 1930s, have fluctuated along with the oil price and have considerably increased in the last decade due to the interest to exploit shale gas and renewable resources to obtain the gaseous feedstock. Nevertheless, no catalytic system reported to date has performed sufficiently well to justify an industrial implementation. Since the design of an efficient catalyst would strongly benefit from the establishment of synthesis–structure–function relationships and a deeper understanding of the reaction mechanism, this review comprehensively overviews syngas-based higher alcohols synthesis in three main sections, highlighting the advances recently made and the challenges that remain open and stimulate upcoming research activities. The first part critically summarises the formulations and methods applied in the preparation of the four main classes of materials, i.e., Rh-based, Mo-based, modified Fischer–Tropsch and modified methanol synthesis catalysts. The second overviews the molecular-level insights derived from microkinetic and theoretical studies, drawing links to the mechanisms of Fischer–Tropsch and methanol syntheses. Finally, concepts proposed to improve the efficiency of reactors and separation units as well as to utilise CO2 and recycle side-products in the process are described in the third section.

Status and prospects in higher alcohols synthesis from syngas

An integrated thermochemical biomass to ethanol process was demonstrated at the pilot scale at the National Renewable Energy Laboratory (NREL). A total of 233 h of pilot scale mixed alcohol production was achieved, comprising 81 h of continuous operation in methanol-derived syngas followed by 152 h of continuous operation in biomass-derived syngas. During this period the system generated 20 L of mixed alcohol product. The fully integrated biomass to mixed alcohol process was comprised of a solids feeder, fluidized bed indirect steam gasifier, thermal cracker, char collector, fluidized bed steam reformer, packed bed polishing steam reformer, scrubber, pressure-swing CO2 adsorber, and gas-phase continuously stirred tank gas-to-liquid reactor (CSTR). Additional pumps, compressors, and blowers were used to convey gases, solids, and liquids. Tars and methane were reformed using sequential steps: first in a fluidized bed using an NREL-developed Ni-based catalyst followed by a fixed bed reactor loaded with pelle...

Pilot Scale Production of Mixed Alcohols from Wood

Cobalt molybdenum sulfide-type mixed alcohol catalysts were synthesized via calcination of precipitated bulk sulfides and studied with temperature programmed decomposition analysis. Precursors containing aqueous potassium were also considered. Precipitates thermally decomposed in unique events which released ammonia, carbon dioxide, and sulfur. Higher temperature treatments led to more crystalline and less active catalysts in general with ethanol productivity falling from 203 to 97 g (kg cat) −1  h −1 when the calcination temperature was increased from 375 to 500 °C. The addition of potassium to the precursor led to materials with crystalline potassium sulfides and good catalytic performance. In general, less potassium was required to promote alcohol selectivity when added before calcination. At calcination temperatures above 350 °C, segregated cobalt sulfides were observed, suggesting that thermally decomposed sulfide precursors may contain a mixture of molybdenum and cobalt sulfides instead of a dispersed Co Mo S type of material. When dimethyl disulfide was fed to the precursor during calcination, crystalline cobalt sulfides were not detected, suggesting an important role of free sulfur during decomposition.

Thermal Decomposition of Bulk K-CoMoSx Mixed Alcohol Catalyst Precursors and Effects on Catalyst Morphology and Performance

A surfactant‐free synthesis of the silica nanosphere‐supported ultrafine silver nanoparticles and their antibacterial effects

Characteristic studies, by means of XRD, XPS, LRS, IR and TPD methods, of MoS x -K 4 /SiO 2 catalysts for mixed alcohols synthesis provide experimental evidence for formation of Mo-S-K surface phase and presence of disulfide species, (S-S) 2− , at the surface of the catalysts. One of the origins of the promoter action in shifting the selectivity from hydrocarbons to alcohols is likely that addition of the alkali salt led to a decrease in concentration of (S-S) 2− at the surface, which in turn would reduce the generation of the reactive hydrogen.

张鸿斌

Papers

Characterization of mosx-k+/sio2 catalysts for synthesis of mixed alcohols from syngas