Autothermal partial oxidation of butanol isomers (original) (raw)
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Status and prospects in higher alcohols synthesis from syngas
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.
Journal of Catalysis, 1986
A new mechanism for the synthesis of alcohols from synthesis gas is proposed based on recent observations from surface spectroscopy, catalysis, and synthetic organometallic chemistry. Stepwise transfer of hydrogens to coordinated CO and chain growth by CO insertion provide the primary pathway for the construction of higher alcohols over metal oxide catalysts. The insertion of a carbon monoxide into a surface-bound aldehyde is proposed as the primary carbon-carbon bond forming step in the chain growth. A competing carbon-carbon bond-forming step is the reaction of a surface &enolate with a surface alkoxide. This condensation reaction is critical for providing product distributions deviating from those predicted by simple polymerization schemes. A novel rationale is proposed to explain the selectivity to branched products. The relative stabilities of the enolate precursors to the various alcohols and the relative rates of the 1,2-shift reactions of methyl and hydrogen are the rate-controlling mechanistic features which regulate selective formation of branched higher alcohol products. The mechanism is related to the dehydration of secondary alcohols to I-olefins catalyzed by basic metal oxides. o 1986 Academic PEW Inc.
New insight into the role of gas phase reactions in the partial oxidation of butane
Catalysis Today, 2003
The partial oxidation of n-butane at high alkane to oxygen ratio was studied in the presence of a Pt-Rh gauze and in an empty tubular reactor under identical conditions. Temperature-programmed reaction (TPR) experiments with the metal gauze showed dramatic changes in the product distribution in the range 25-500 • C. Total oxidation of butane at low temperature is followed by selective conversion to olefins and oxygenates around 400 • C; a further increase in the oven temperature enhances selectively olefins formation. In situ infrared and visible imaging of the reacting gauze revealed remarkable ignition/extinction phenomena of the surface reactions. Fast ignition on the metal catalyst was observed around 200 • C; upon further raising the oven temperature, suppression of these reactions occurred at a temperature level corresponding to the transition to high selectivity conditions. These results indicate a shift from heterogeneous to homogeneous reaction mechanism, the latter being responsible for high selectivity to partial oxidation products (84% olefins + oxygenates). With the empty reactor, conversion and selectivity were similar to those obtained in the presence of the catalyst. The study shows that the gauze plays no significant role in butane partial oxidation, as reactions take place in the void upstream of the catalyst, presumably via an alkylperoxy intermediate.
Energy & Fuels, 2008
Alternatives to petroleum-derived fuels and chemicals are being sought in an effort to improve air quality and increase energy security through development of novel technologies for the production of synthetic fuels and chemicals using renewable energy sources such as biomass. In this context, ethanol is being considered as a potential alternative synthetic fuel to be used in automobiles or as a potential source of hydrogen for fuel cells as it can be produced from biomass. Renewable ethanol can also serve as a feedstock for the synthesis of a variety of industrial chemicals and polymers. Currently, ethanol is produced primarily by fermentation of biomass-derived sugars, especially those containing six carbons, whereas 5-carbon sugars and lignin, which are also present in the biomass, remain unusable. Gasification of biomass to syngas (CO + H 2), followed by catalytic conversion of syngas, could produce ethanol in large quantities. However, the catalytic conversion of syngas to ethanol remains challenging, and no commercial process exists as of today although the research on this topic has been ongoing for the past 90 years. Both homogeneous and heterogeneous catalytic processes have been reported. The homogeneous catalytic processes are relatively more selective for ethanol. However, the need for expensive catalyst, high operating pressure, and the tedious workup procedures involved for catalyst separation and recycling make these processes unattractive for commercial applications. The heterogeneous catalytic processes for converting syngas to ethanol suffer from low yield and poor selectivity due to slow kinetics of the initial CC bond formation and fast chain growth of the C 2 intermediate. Recently, there is a growing worldwide interest in the conversion of syngas to ethanol. Significant improvements in catalyst design and process development need to be achieved to make this conversion commercially attractive. This paper reviews and critically assesses various catalytic routes reported in the recent past for the conversion of syngas to higher alcohols, with an emphasis on ethanol. The chemistry and thermodynamics of the processes, the type of catalysts developed, reactors used, and the current status of the technology are reviewed and discussed.
Applied Catalysis A: General, 2012
The focus of the present study was to investigate the effect of the operation conditions, space velocity and temperature, on product distribution for a K-Ni-MoS 2 catalyst for mixed alcohol synthesis from syngas. All experiments were performed at 91 bar pressure and constant H 2 /CO = 1 syngas feed ratio. For comparison, results from a non-promoted MoS 2 catalyst are presented. It was found that the CO conversion level for the K-Ni-MoS 2 catalyst very much decides the alcohol and hydrocarbon selectivities. Increased CO conversion by means of increased temperature (tested between 330 and 370 • C) or decreased space velocity (tested between 2400 and 18,000 ml/(g cat h)), both have the same effect on the product distribution with decreased alcohol selectivity and increased hydrocarbon selectivity. Increased CO conversion also leads to a greater long-to-short alcohol chain ratio. This indicates that shorter alcohols are building blocks for longer alcohols and that those alcohols can be converted to hydrocarbons by secondary reactions. At high temperature (370 • C) and low space velocity (2400 ml/(g cat h)) the selectivity to isobutanol is much greater than previously reported (9%C). The promoted catalyst (K-Ni-MoS 2) is also compared to a non-promoted (MoS 2) catalyst; the promoted catalyst has quite high alcohol selectivity, while almost only hydrocarbons are produced with the non-promoted catalyst. Another essential difference between the two catalysts is that the paraffin to olefin ratio within the hydrocarbon group is significantly different. For the non-promoted catalyst virtually no olefins are produced, only paraffins, while the promoted catalyst produces approximately equal amounts of C 2-C 6 olefins and paraffins. Indications of olefins being produced by dehydration of alcohols were found. The selectivity to other non-alcohol oxygenates (mostly short esters and aldehydes) is between 5 and 10%C and varies little with space velocity but decreases slightly with increased temperature. Very strong correlation patterns (identical chain growth probability) and identical deviations under certain reaction conditions between aldehyde and alcohol selectivities (for the same carbon chain length) indicate that they derive from the same intermediate. Also olefin selectivity is correlated to alcohol selectivity, but the correlation is not as strong as between aldehydes and alcohols. The selectivity to an ester is correlated to the selectivity to the two corresponding alcohols, in the same way as an ester can be thought of as built from two alcohol chains put together (with some H 2 removed). This means that, e.g. methyl acetate selectivity (C 3) is correlated to the combination of methanol (C 1) and ethanol (C 2) selectivities.
Mini-Review: Syngas Production Via Partial Oxidation of Methane Reaction and Its Potential Catalyst
Akta Kimia Indonesia, 2021
Methane as a light gas was generally found in natural gas, which was burned freely to gain a high quality of petroleum. This action truly impacted the worst condition in nature, namely the greenhouse effect. This brief review described a fundamental theory of the crucial process in methane conversion from natural gas into value-added chemicals such as syngas (CO+H2). The methane conversion reaction was commonly divided into direct and indirect reactions. The indirect reaction such as partial oxidation of methane was mostly chosen due to the intermediate product (syngas) can easily generate many raw materials of petrochemicals. This paper also described a potential catalyst to be applied in heterogeneous types, such as perovskite oxide, metal oxide, and zeolite.
A detailed surface reaction model for syngas production from butane over Rhodium catalyst
International Journal of Hydrogen Energy, 2011
Micro solid oxide fuel cell a b s t r a c t This paper presents numerical and experimental investigations of syngas production from butane. A surface reaction mechanism is used to model the reaction pathways. The butane reforming simulations and experiments are conducted in two reformers (tubular and radial). Starting from the reaction mechanism for methane conversion over a Rh catalyst, a reaction mechanism for butane conversion over the same catalyst is developed. The surface reaction equations are coupled with the flow equations. Porous resistance, catalyst concentration and reaction rate constants of the introduced reaction pathways are estimated by comparing the results of the model with the experimental data. The model is able to capture the main features of the species profiles along the reactors as well as the selectivity trends for different equivalence ratios. Moreover, the model predicts the fractional coverage of the surface species and therefore provides an insight into the reaction mechanisms on the catalyst surface. (D. Poulikakos).