Pyrolysis products catalytic upgrading

Catalytic pyrolysis is the conversion of biomass via pyrolysis in the presence of a catalyst [27]. In this process, the catalyst can react in a secondary reactor directly with the vapors produced by pyrolysis, or the catalyst can be mixed with the biomass in a fluidized bed pyrolysis reactor [28], In either system, catalysts with high selectivity to diesel and gasoline range hydrocarbons are often preferred [29-31], Because the pyrolysis products are upgraded by additional deoxygenation reactions on the catalyst, the resulting catalyticaUy produced bio-oil is generally more stable than noncatalytic pyrolysis bio-oil. 

Catalytic upgrading of bio-oil was carried out over Ga modified ZSM-5 for the pyrolysis of sawdust in a bubbling fluidized bed reactor. Effect of gas velocity (Uo/U ,f) on the yield of pyrolysis products was investigated. The maximum yield of oil products was found to be about 60% at the Uo/Umf of 4.0. The yield of gas was increased as catalyst added. HZSM-5 shows the larger gas yield than Ga/HZSM-5. When bio-oil was upgraded with HZSM-5 or Ga/HZSM-5, the amount of aromatics in product increased. Product yields over Ga/HZSM-5 shows higher amount of aromatic components such as benzene, toluene, xylene (BTX) than HZSM-5. 

In diis chapter, the main technical aspects of different thermochemical processes for biomass conversion are discussed. In addition, various hydro-thermal treatments applied to lignocellulosic biomass for the production of fermentable sugars, hydrogen or other value-added products are presented. This chapter also describes about pyrolysis along with its various parameters that influence conversion product yields. Bio-oil, which is a complex mixture or both aqueous and organic biomass components, is discussed in details along with its catalytic upgrading for use as transportation fuel. 

Adjaye JD, Bakhshi NN. Production of hydrocarbons by catalytic upgrading a fast pyrolysis bio-oil. 1. Conversion over various catalysts. Enel Process Technol 1995 45 161-83. 

In the process of the catalytic conversion of biomass to biooil, the incorporation of different types of metals such as Bi, Ce, Co, Cu, Fe, Ga, Na, and Ni into the catalysts can play a very important role. Among the different metals Ni has been shown to display the best activities in combination with a ZSM-5 catalyst for the conversion of oxygenated compounds to hydrocarbon species (French and Czemik, 2010). Studies on the catalytic upgradation of pyrolysis vapor obtained from biomass have shown that the product composition may depend on the nature of the catalyst. 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

Samolada, M.C., Baldauf, W., Vasalos, I.A., Production of bio-gasoline by upgrading biomass flash pyrolysis liquids via hydrogen processing and catalytic cracking, Fuel, 1998, 77, 1667. 

Other stocks which may be upgraded by hydrotreating are thennally and catalytic cracked naphthas, straight-run naphthas abnormally high in contaminants, and coker gasolines. The latter are produced by the high-temperature pyrolysis of reduced fuel to coke and distiUate fractions. Naphthas to be used as specialty solvents also are treated to obtain premium products with respect to color, odor, and stability. 

Conversion of biomass at a temperature of 300 350 °C and a pressure of 120-180 bar within the so-called HydroThermal Upgrading (HTU) process yields a mixture of hydrocarbons, carbon dioxide, water and dissolved organics, which can be further processed in a catalytic HydroDeOxygenation (HDO) step to yield diesel with characteristics similar to fossil diesel. A major advantage is that wet biomass feedstocks can be employed without drying in contrast, water at hydrothermal conditions acts as a solvent and reactant at the same time, leading to a product with less oxygen compared to biocrude prepared by pyrolysis. 

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