We review synthetic, mechanistic and process aspects of the direct syngas conversion into higher ... more We review synthetic, mechanistic and process aspects of the direct syngas conversion into higher alcohols to foster the identification of industrially-viable catalysts.
Atomic intermixing, high dispersion and primarily reduced state are prerequisites of supported Co... more Atomic intermixing, high dispersion and primarily reduced state are prerequisites of supported Co and Mo for an effective higher alcohol synthesis.
Higher alcohols are important compounds with widespread applications in the chemical, pharmaceuti... more 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.
ABSTRACT Among the renewable energy sources, biomass offers some benefits due to its low cost and... more ABSTRACT Among the renewable energy sources, biomass offers some benefits due to its low cost and presumed zero-carbon emission when compared with fossil fuels. However, the moisture content of biomass is often high that lowers its heating value, reduces the combustion temperature and causes operational problems. Because of these, when burning biomass for power generation, biomass is often dried prior to the combustion. To lower the drying cost or to maximize the power output of a biomass power plant, proper heat integration in between the steam power plant and the drying process has to be considered. In this work, heat integration studies are performed to a biomass power plant that burns empty fruit bunches (EFB) as fuel. Composite curves of all studied cases are plotted to visualize the intensity and to identify opportunities of heat integration among the drying and power generation systems. A multi-stage drying process is proposed that employs steam and waste-heat from the power plant and the drying process respectively. Results of this study show that with proper drying and heat integration, the overall efficiency of a biomass power plant can be significantly improved.
It is well established that hydrogen has the potential to make a significant contribution to the ... more It is well established that hydrogen has the potential to make a significant contribution to the world energy production. In U.S., majority of hydrogen production plants implement steam methane reforming (SMR) for centralized hydrogen production. However, there is a wide lack of agreement on the nascent stage of using hydrogen as fuel in vehicles industry because of the difficulty in delivery and storage. By performing technological and economic analysis, this work aims to establish the most feasible hydrogen production pathway for automotives in near future. From the evaluation, processes such as thermal cracking of ammonia and centralized hydrogen production followed by bulk delivery are eliminated while on-site steam reforming of methanol and natural gas are the most technologically feasible options. These two processes are further evaluated by comprehensive economic analysis. The results showed that the steam reforming (SR) of natural gas has a shorter payback time and a higher return on investment (ROI) and internal rate of return (IRR). Sensitivity analysis has also been constructed to evaluate the impact of variables like NG feedstock price, capital of investment and operating capacity factor on the overall production cost of hydrogen. Based on this study, natural gas is prompted to be the most economically and technologically available raw material for short-term hydrogen production before the transition to renewable energy source such as solar energy, biomass and wind power.
We review synthetic, mechanistic and process aspects of the direct syngas conversion into higher ... more We review synthetic, mechanistic and process aspects of the direct syngas conversion into higher alcohols to foster the identification of industrially-viable catalysts.
Atomic intermixing, high dispersion and primarily reduced state are prerequisites of supported Co... more Atomic intermixing, high dispersion and primarily reduced state are prerequisites of supported Co and Mo for an effective higher alcohol synthesis.
Higher alcohols are important compounds with widespread applications in the chemical, pharmaceuti... more 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.
ABSTRACT Among the renewable energy sources, biomass offers some benefits due to its low cost and... more ABSTRACT Among the renewable energy sources, biomass offers some benefits due to its low cost and presumed zero-carbon emission when compared with fossil fuels. However, the moisture content of biomass is often high that lowers its heating value, reduces the combustion temperature and causes operational problems. Because of these, when burning biomass for power generation, biomass is often dried prior to the combustion. To lower the drying cost or to maximize the power output of a biomass power plant, proper heat integration in between the steam power plant and the drying process has to be considered. In this work, heat integration studies are performed to a biomass power plant that burns empty fruit bunches (EFB) as fuel. Composite curves of all studied cases are plotted to visualize the intensity and to identify opportunities of heat integration among the drying and power generation systems. A multi-stage drying process is proposed that employs steam and waste-heat from the power plant and the drying process respectively. Results of this study show that with proper drying and heat integration, the overall efficiency of a biomass power plant can be significantly improved.
It is well established that hydrogen has the potential to make a significant contribution to the ... more It is well established that hydrogen has the potential to make a significant contribution to the world energy production. In U.S., majority of hydrogen production plants implement steam methane reforming (SMR) for centralized hydrogen production. However, there is a wide lack of agreement on the nascent stage of using hydrogen as fuel in vehicles industry because of the difficulty in delivery and storage. By performing technological and economic analysis, this work aims to establish the most feasible hydrogen production pathway for automotives in near future. From the evaluation, processes such as thermal cracking of ammonia and centralized hydrogen production followed by bulk delivery are eliminated while on-site steam reforming of methanol and natural gas are the most technologically feasible options. These two processes are further evaluated by comprehensive economic analysis. The results showed that the steam reforming (SR) of natural gas has a shorter payback time and a higher return on investment (ROI) and internal rate of return (IRR). Sensitivity analysis has also been constructed to evaluate the impact of variables like NG feedstock price, capital of investment and operating capacity factor on the overall production cost of hydrogen. Based on this study, natural gas is prompted to be the most economically and technologically available raw material for short-term hydrogen production before the transition to renewable energy source such as solar energy, biomass and wind power.
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Papers by Ho Luk