Pyrolysis oils

E. J. Soltes and T. A. Milne, eds.. Pyrolysis Oils from Biomass Producing Analy ng and Upgrading, ACS Symposium Series 376, American Chemical Society, Washington, D.C., 1988. 

GC-MS and GC-AED techniques were used for the direct analysis of used tyre vacuum pyrolysis oil [255]. Antioxidants and antiwear additives (0.25-5 wt% DODPA, a-NPA, TCPs, TPP, IPPs) in lubricating synthetic oils, essentially esters of branched-chain alcohols such as pentaerythritol, neopentylglycol and trimethylolpropane, were determined by means of GC-SIM-MS using diphenylamine (DPA) as an internal standard [256] similarly, TCPs, TPP, IPPs, DPs and I2P were quantitatively analysed by GC-FPD using triethylphosphate (TEP) as an internal standard. RSD values of 3-6% were reported for GC-SIM-MS, and 7-9 % for GC-FPD. 

SEC in combination with multidimensional liquid chromatography (LC-LC) may be used to carry out polymer/additive analysis. In this approach, the sample is dissolved before injection into the SEC system for prefractionation of the polymer fractions. High-MW components are separated from the additives. The additive fraction is collected, concentrated by evaporation, and injected to a multidimensional RPLC system consisting of two columns of different selectivity. The first column is used for sample prefractionation and cleanup, after which the additive fraction is transferred to the analytical column for the final separation. The total method (SEC, LC-LC) has been used for the analysis of the main phenolic compounds in complex pyrolysis oils with minimal sample preparation [974]. The identification is reliable because three analytical steps (SEC, RPLC and RPLC) with different selectivities are employed. The complexity of pyrolysis oils makes their analysis a demanding task, and careful sample preparation is typically required. 

The objective of this work is to synthesize and characterize zeolite-bentonite hybrid catalysts and perform test reactions in the pyrolysis of woody biomass in a dual-fluidized bed reactor. The aim is to produce catalytic materials which have good mechanical strength and are still able to de-oxygenate the pyrolysis oil. 

Syngas polygeneration based on a combination of decentralized pyrolysis of biomass and central gasification of pyrolysis oil/char slurry. (Reproduced from Henrich, E., Raffelt, K., Stahl, R., and Weirich, F., Science in Thermal and Chemical Biomass Conversion, CPL Press, Victoria, 2004. With permission.)... 

Fig. 5.2 The main crop-to-energy chains. BtL Biomass-to-Liquid, GtL Gas-to-Liquid, ETBE Ethyl tert-butyl ether, MTBE Methyl tert-butyl ether, MeOH Methanol, DME Dimethyl ether. Pyrolysis oil, HTU-Diesel (Hydro Thermal Upgrading), ethanol and hydrogen from ligno-cellulosic species are not considered here because of their minor practical relevance in the near future...

The aqueous-phase pyrolysis can also be assisted by catalysts and reactive gases. For instance, the PERC process [3, 33] produces a pyrolysis oil upon dissolving wood chips in a recycle pyrolysis oil, mixing the slurry with a water-Na2C03 solution and treating the resulting mixture at 370 °C and 275 bar under synthesis gas atmosphere. 

These various alternatives provide a pyrolysis oil of much better quality than do flash pyrolysis processes such as the BTG one. However, they also require much higher investments that result from the use of high pressure and a corrosive reaction medium. 

The present chapter discusses aspects, known by the authors, of (a) biomass as feedstock, (b) the concept of bio-refinery, (c) thermochemical routes from lignocellulosic biomass to fuels, and (d) the contribution of catalytic technology. The main focus will be on the catalytic conversion of fast pyrolysis oil into fuels with regard to problems encountered currently and the challenges for future research and development. 

Heavy fuel oil Primary bioliquids (pyrolysis oil, hydrothermal liquefaction oil)... 

CO = 25 vol.%, C02 = 12 vol.%) not containing any hydrocarbons and a low tar (200 mg Nm 3) content at 800 °C and S/C (steam over carbon ratio) = 1.5. Problems associated with pyrolysis oil gasification are similar to those of biomass gasification. Gasification of the tar fraction and conversion of methane formed are important challenges. Both require highly active and stable steam/autothermal reforming catalysts. 

Fast pyrolysis oil is an acidic viscous dark brown liquid (Fig. 6.6) containing oxygenated hydrocarbons, water and small carbonaceous particles including some minerals. 

Fast pyrolysis oil has almost the same elemental composition as the biomass itself hence it can be seen as a kind of liquid wood. It can be transported, can be pressurized and processed more easily than solid biomass. One of the major difficulties in the catalytic conversion of solid biomass is achieving effident con-tad between the heterogeneous catalyst (which is most of the times a solid) and the biomass itself. In this context, bio-oil provides more options for easier catalytic conversion. However, pyrolysis is a very complex and the oil is a difficult to handle chemical mixture. Complete vaporization, for instance, is not possible because part of the components start to decompose and polymerize upon heating... 

Several researchers have shown that alkali present in the feedstock influences the yields and compositions of the pyrolysis products [56, 59]. An interesting result was reported by Brown and coworkers [60] who found that addition of (NH4)2S04 as catalyst to the pyrolysis of dematerialized (alkali free) corn stover resulted in a pyrolysis oil that contained 23 wt.% levoglucosan (normally 1-3 wt.% levoglucosan is present in pyrolysis oil). Levoglucosan is a component from which various fuel blends and chemicals can be produced. 

Deoxygenation reactions are catalyzed by acids and the most studied are solid acids such as zeolites and days. Atutxa et al. [61] used a conical spouted bed reactor containing HZSM-5 and Lapas et al. [62] used ZSM-5 and USY zeolites in a circulating fluid bed to study catalytic pyrolysis (400-500 °C). They both observed excessive coke formation on the catalyst, and, compared with non-catalytic pyrolysis, a substantial increase in gaseous products (mainly C02 and CO) and water and a corresponding decrease in the organic liquid and char yield. The obtained liquid product was less corrosive and more stable than pyrolysis oil. 

Van Swaaij, W.P.M., Catalytic and non-catalytic gasification of pyrolysis oil, submitted to Ind. Eng. Chem. Res., available online DOI 10.1021/ie061337y. 

Czemik, S., Bridgwater, A.V., Overview of application of biomass fast pyrolysis oil, Energy Fuels, 2004, 18, 590. 

Effects on the quality of fast pyrolysis oils, Energy Fuels, 1996, 10, 293. 

Baldauf, W., Balfanz, U., Rupp, M., Upgrading of flash pyrolysis oils and utilization in refineries, Biomass Bioenergy, 1994, 7, 237. 

Gayubo, A.G., Aguayo, A.T., Atutxa, A., Aguado, R., Bilbao, J., Transformation of oxygenate components of biomass pyrolysis oil on a HZSM-5 zeolite. 

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