Fluid catalytic pyrolysis

Fig. 3. Fluid catalytic pyrolysis. From the Research Institute of Petroleum Processing, Beijing, China, 1991.

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. 

Catalytic Pyrolysis. This should not be confused with fluid catalytic cracking, which is used in petroleum refining (see Catalysts, regeneration). Catalytic pyrolysis is aimed at producing primarily ethylene. There are many patents and research articles covering the last 20 years (84—89). Catalytic research until 1988 has been summarized (86). Almost all catalysts produce higher amounts of CO and CO2 than normally obtained with conventional pyrolysis. This indicates that the water gas reaction is also very active with these catalysts, and usually this leads to some deterioration of the olefin yield. Significant amounts of coke have been found in these catalysts, and thus there is a further reduction in olefin yield with on-stream time. Most of these catalysts are based on low surface area alumina catalysts (86). A notable exception is the catalyst developed in the former USSR (89). This catalyst primarily contains vanadium as the active material on pumice (89), and is claimed to produce low levels of carbon oxides. 

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. 

Catalytic cracking is the process of upgrading gas oil or even residual oil (heavy oil) to produce gasoline, distillates, light olefines, etc. Commercialized processes include fluid catalytic cracking (FCC), residual oil catalytic cracking (RFCC), and catalytic pyrolysis, etc. 

D. L. Trimm in Fundamental Aspects of the Formation and Gasification of Coke in L. F. Albright, B. L. Crynes, W. H. Corcoran (eds.), Pyrolysis Theory and Industrial Practice , Academic Press, New York, 1983 L. F. Albright, B. L. Crynes, W. H. Corcoran (eds.), Pyrolysis Theory and Industrial Practice , Academic Press, New York, 1983 T. J. Ford, Ind. Eng. Chem. Fundam., 25, 240, 1986 Coastal Isobutane Cracking Process developed by Foster Wheeler P. B. Venuto and E. T. Habib, Fluid Catalytic Cracking with Zeolite Catalysts , Marcel Dekker, New York, 1979... 

For some widely practiced processes, especially in the petroleum industry, reliable and convenient computerized models are available from a number of vendors or, by license, from proprietary sources. Included are reactor-regenerator of fluid catalytic cracking, hydro-treating, hydrocracking, alkylation with HF or H2SO4, reforming with Pt or Pt-Re catalysts, tubular steam cracking of hydrocarbon fractions, noncatalytic pyrolysis to ethylene, ammonia synthesis, and other processes by suppliers of catalysts. Vendors of some process simulations are listed in the CEP Software Directory (AIChE, 1994). 

A. Marcilla, A. Gomez, J. A. Reyes-Labarta, A. Giner and F. Hernandez, Kinetic study of polypropylene pyrolysis using ZSM-5 and an equilibrium fluid catalytic cracking catalysts. J. Anal. Appl. Pyrolysis, 68-69, 467-480 (2003). 

Fluid catalytic cracking (FCC) has been used since the 1950s to turn heavy distillates (vacuum gas oil) into a series of light and dense fractions. The FCC catalysts can also be used as pyrolysis catalysts. 

Similarly the fluidized-bed pyrolysis of polystyrene in the presence of fluid catalytic cracking (FCC) catalysts was investigated at temperatures between 370 and 515°C [18]. In... 

Apart from the oxidation of organic molecules, the catalytic pyrolysis of waste tires to light olefins using mesoporous material containing metals was also performed. Generally, the production of light olefins has been derived mostly from steam crackers and refinery fluid catalytic cracking units. Moreover, their demand... 

Cracking of plastic wastes to gasoline and fuel oil in fluid catalytic cracker (FCC) should be more attractive than other pyrolysis processes except when the pyrolysis process is highly selective to high valued monomers, [3]. Most likely the presence of fillers in the waste can be compensated for by catalyst additions. Studies have shown that, in an FCC unit, the following significant product yields are obtained ... 

Smooth Exit Promotes high solids circulation rate (external) with a uniform RTD (plug flow) at a low pressure drop. Ideal for certain catalytic reactions involving catalyst deactivation e,g. fluid catalytic cracking. Also suited for flash pyrolysis. 

This situation can be clearly seen when observing the time evolution of the tube metal temperature of the pyrolysis coils there is a fast initial increase and then a reduced asymptotic slope. Note that although the initial slope is initially related to the catalytic rate, it is also due to the relatively low thermal conductivity of the initial fibrous material as a result of the large void fraction. The thickness of this layer is in the order of 20-40 pm. The evolution of the fluid temperature over time either at the TLE outlet or in visbreaking processes and in delayed coking furnaces shows a very similar behaviour. 

A schematic and photograph of the pilot-scale catalytic fluid bed reformer are shown in Figure 4. The 30-cm catalytic steam reforming reactor was successfully operated on peanut pyrolysis vapor at a feed rate of 7 kg/hour of vapors. The results are in agreement with those obtained from the 5-cm bench-scale reactor used for the reforming of the aqueous fraction of pyrolysis oil. Typical gas compositions at the outlet of the reformer are shown in Figure 5. These data show that the yield of hydrogen is approximately 90% of maximum. 

When processing wood pyrolysis liquids, the two pyrolysis product liquid layers were homogenized (EHI of the blend was 0.32) by high speed mixing and fed immediately to the fluid bed catalytic reactor. When co-processed with methanol, the two pyrolysis liquid layers were dissolved in the methanol to provide a mixture having an apparent EHI of 1.2-1.3. 

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