Catalysts for Production of Lower Olefins from Synthesis Gas: A Review

Abstract

C 2 to C 4 olefins are traditionally produced from steam cracking of naphtha. The necessity for alternative production routes for these major commodity chemicals via non-oil-based processes has driven research in past times during the oil crises. Currently, there is a renewed interest in producing lower olefins from alternative feedstocks such as coal, natural gas, or biomass, in view of high oil prices, environmental regulations, and strategies to gain independence from oil imports. This review describes the major routes for the production of lower olefins from synthesis gas with an emphasis on a direct or single step process, the so-called FTO or Fischer−Tropsch to olefins process. The different catalysts for FTO are outlined and compared, and the key issues and requirements for future developments are highlighted. Iron-based catalysts are prevailing for FTO, and reproducible lower olefin selectivities of 50 wt % of hydrocarbons produced have been realized at CO conversions higher than 70% for 60 to 1000 h on stream. Remarkably the high selectivity to lower olefins has been achieved over a broad range of process conditions (P, T, H 2 /CO ratio, GHSV). A major challenge for further development and application of FTO catalysts is the suppression of carbon lay-down to enhance catalyst lifetime and to preserve their physical integrity under demanding reaction conditions.

Metal organic framework-mediated synthesis of highly active and stable Fischer-Tropsch catalysts

“…The Fe@C catalysts were tested in the FTS reaction at 613 K, 20 bar, H 2 /CO ¼ 1 and gas hourly space velocity (GHSV) of 30,000 h À 1 (space velocity based on catalyst bed volume). Owing to the outstanding effect of potassium promotion on iron-based catalyst for FTS, namely improving activity and olefins to paraffins ratio [33][34][35] , a series of alkali-promoted samples were are also synthesized.…”

“…Mössbauer spectroscopy shows that catalysts prepared by the MOFMS approach offer an intimate contact between Fe and C, favouring the formation of w À Fe 5 C 2 , which is well known to be the most active phase in the FTS process. Such a poor stability, which is generally observed for systems with larger Fe particles, is often associated with the continuous structural and chemical transformations of the iron phases, as well as to the nucleation of carbon deposits on the catalyst surface 34 . The striking stability of the Fe@C catalysts is attributed to the fact that most Fe nanoparticles are smaller than 9 nm and to the spatial restriction created by the encapsulated carbon.…”

Olefins from Biomass Intermediates: A Review

“…Almost 60% of the global feedstocks are used in FCC units, and approximately 40% in steam cracking processes. (Figure 1) Produced olefins can be used in a wide spectrum of high-end applications such as packaging, construction, solvents, coatings, and synthetic fibers [4]. Olefin production methods using hydrocarbon feedstocks.…”

“…Its eminent industrial uses cause the world demand for C2H4 to incessantly increase, as it can be used for significant applications, such as the production of intermediate chemicals, mainly in the industry of plastics. i.e., polymers (e.g., poly-ethylene), propionaldehyde-via hydroformylation, vinyl chloride-via halogenation and de-hydrohalogenation, alpha-olefins-via oligomerization, and C2H4 oxide and acetaldehyde-via oxidation [4,6,7]. In recent years, bio-ethanol has been extensively studied as an alternate feedstock for C2H4 production [8].…”

Influence of Preparation Methods on Catalytic Performance of Fe/NCNTs Fischer-Tropsch Catalysts

“…费托合成产物的分布一般 受 Anderson-Schulz-Flory (ASF)分布规律的限制 [2～4] . 铁 基催化剂是常用的合成气制低碳烯催化剂 [2,5] . 催化剂 的性能依赖于催化活性组分、载体和催化助剂, 其中载 体的性质(如比表面积、孔道结构、表面酸碱性、与活 性组分的相互作用)很大程度上影响着活性组分的分 散、反应物/产物的吸附/脱附、催化剂的还原和碳化, 从 而影响催化剂的性能 [6～10] .…”