Exergy Analysis of Alternative Configurations of Biomass-Based Light Olefin Production System with a Combined-Cycle Scheme via Methanol Intermediate

Thermodynamic performance of three conceptual systems for biomass-derived olefin production with electricity cogeneration was studied and compared via exergy analysis at the levels of system, subsystem and operation unit. The base case was composed of the subsystems of gasification, raw fuel gas adjustment, methanol/light olefin synthesis and steam & power generation, etc. The power case and fuel case were designed as the combustion of a fraction of gasification gas to increase power generation and the recycle of a fraction of synthesis tail gas to increase olefin production, respectively. It was found that the subsystems of gasification and steam & power generation contribute ca. 80% of overall exergy destruction for each case, of which gasifier and combustor are the main exergy destruction sources, due to the corresponding chemical exergy degrading of biomass and fuel gas. The low efficiency of 33.1% for the power case could be attributed to the significant irreversibility of the combustor, economizer, and condenser in the combined-cycle subsystem. The effect of the tail gas recycle ratio, moisture content of feedstock, and biomass type was also investigated to enhance system exergy performance, which could be achieved by high recycle ratio, using dry biomass and the feedstock with high carbon content. High system efficiency of 38.9% was obtained when oil palm shell was used, which was 31.7% for rice husk due to its low carbon content.

Facile and Rapid Synthesis of Durable SSZ-13 Catalyst using Choline Chloride Template for Methanol-to-Olefins Reaction

In the current study, a facile and rapid synthesis approach for a SSZ-13 catalyst using choline chloride (CC) as a template was proposed, and the catalytic performance for the methanol-to-olefins (MTO) reaction was examined. With a proper amount of CC addition (i.e., m(CC)/m(SiO2)=0.14), uniform and homogeneously distributed cubic SSZ-13 crystals were obtained within 4 h with lower aggregation. The synthesized catalyst demonstrated excellent porous features with a total specific surface area and mesopore volume of 641.71 m2·g−1 and 0.04 cm3·g−1, respectively. The optimized strong and weak acid sites on SSZ-13 were obtained by regulating the m(CC)/m(SiO2) ratio. The less strong acid sites and a larger amount of weak acid sites in the synthesized catalyst were conducive to the catalytic performance of the MTO reaction under a lower reaction temperature (450 °C). The appropriate acidity and well-developed pore structure of synthesized SSZ-13 could also slow down the carbon deposition rate and, thus, significantly improve the catalytic lifetime of the catalyst. The methanol conversion rate and initial selectivity of light olefin using the synthesized catalyst could maintain over 95% and 50%, respectively, and a lifetime of 172 min was achieved. Although the low olefin selectivity of the synthesized SSZ-13 catalyst was slightly lower than that of the purchased one, its desirable features were thought to have good potential for industrial application.

Facile and Rapid Synthesis of Durable SSZ-13 Catalyst Using Choline Chloride Template for Methanol-to-Olefins

In this study, a facile and rapid synthesis approach for SSZ-13 catalyst was proposed using choline chloride (CC) as template. The optimal synthesis condition was explored, and the catalytic performance for methanol-to-olefins (MTO) was examined. Results revealed that the appropriate ratio of soft template could meet the condition for rapid and ordered growth of catalyst crystals. Using environmentally friend and cheaper CC as template could greatly accelerate the formation of bi-hexagonal ring structure in SSZ-13 framework, and it could shorten the synthesis cycle to within 4 h. With a proper amount of CC addition (i.e., m(CC)/m(SiO2) = 0.14), uniform and homogeneously distributed cubic SSZ-13 crystals were obtained with relatively lower aggregation. The catalyst synthesized with m(CC)/m(SiO2)=0.14 demonstrated excellent porous features with a total specific surface area and mesopore volume of 641.706 m2.g-1 and 0.0377 cm3.g-1, respectively. The optimized strong and weak acid sites on the SSZ-13 were obtained by regulating the m(CC)/m(SiO2). As a typical acid catalytic reaction, the SSZ-13 catalyst with strong and weak acid sites exhibited bi-functional role. The lower amount of strong acid sites and larger amount of weak acid sites in the synthesized catalyst were conducive to the catalytic performance for MTO under relatively lower reaction temperature (450 oC). Consequently, the synthesized SSZ-13 showed a better conversion rate and lifetime than that of purchased one. The methanol conversion rate using synthesized catalyst was maintained over 95% within 120 min, and its lifetime was achieved to 172 min. The appropriate acidity and well-developed pore structure of synthesized SSZ-13 could slow down the carbon deposition rate and significantly increase the lifetime of the catalyst. Moreover, the initial selectivity of light olefin could maintain above 50% within 160 min. Eventually, the desirable features of synthesized SSZ-13 catalyst were thought be with good potential for industrial application.

Fischer–Tropsch Synthesis for Light Olefins from Syngas: A Review of Catalyst Development

Light olefins as one the most important building blocks in chemical industry can be produced via Fischer–Tropsch synthesis (FTS) from syngas. FT synthesis conducted at high temperature would lead to light paraffins, carbon dioxide, methane, and C5+ longer chain hydrocarbons. The present work focuses on providing a critical review on the light olefin production using Fischer–Tropsch synthesis. The effects of metals, promoters and supports as the most influential parameters on the catalytic performance of catalysts are discussed meticulously. Fe and Co as the main active metals in FT catalysts are investigated in terms of pore size, crystal size, and crystal phase for obtaining desirable light olefin selectivity. Larger pore size of Fe-based catalysts is suggested to increase olefin selectivity via suppressing 1-olefin readsorption and secondary reactions. Iron carbide as the most probable phase of Fe-based catalysts is proposed for light olefin generation via FTS. Smaller crystal size of Co active metal leads to higher olefin selectivity. Hexagonal close-packed (HCP) structure of Co has higher FTS activity than face-centered cubic (FCC) structure. Transition from Co to Co3C is mainly proposed for formation of light olefins over Co-based catalysts. Moreover, various catalysts’ deactivation routes are reviewed. Additionally, techno-economic assessment of FTS plants in terms of different costs including capital expenditure and minimum fuel selling price are presented based on the most recent literature. Finally, the potential for global environmental impacts associated with FTS plants including atmospheric and toxicological impacts is considered via lifecycle assessment (LCA).