Pyrolysis yields for pretreatments

Table VII. Yields of organic compounds in pyrolysis syrups for pretreatments of comstover ...

Success in this type of modeling depends on the soundness of the interpolation methods used and the extensiveness of the data base. In addition, the data base must include substantial commercial data to confirm scale-up procedures, if needed. One example is a pyrolysis yield model for virgin gas oil and pretreated feedstocks (23). Feedstocks are classified by source and appropriate characterization parameters. 

Pretreatment stabilizes the stracture of the precursors, acts to maintain the molecular stracture of the carbon chains, and/or enhance the uniformity of pore formation during the pyrolysis process. Current pretreatment includes oxidation, chemical treatment, physical method such as stretching. Oxidation or thermostabilization is the most popular and commonly used method to pretreat the polymeric precursors. This preteatment stabilizes the stracture of the precursors so that they can withstand the high temperatures in several pyrolysis steps. Thermostabilization can maximize the carbon yields of resultant membranes by preventing excessive volatilization of elemental carbon during pyrolysis. Oxidation has been carried out by Kusuki et al. [74], who thermally treated the precursors in atmospheric air at 400°C for 30 min before pyrolysis. Tanihara and Kusuki [75], Okamoto and co-woikers [76], and David and Ismail [31] have also applied thermostabilization. 

One way is the complete or partial destruction of natural biomass by pyrolysis or gasification to yield so-called bio-oil or syngas, respectively. While the downstream processes for syngas (Methanol, Fischer-Tropsch) are state of the art, smaller molecules generated by pyrolysis need a further pretreatment to be developed before they can be used in existing chemical process streams [16]. This is obviously a rather... 

While all pyrolysis oil production reactor systems produce similar materials, each reactor produces a unique compound slate. The first decision, especially for a potential chemical or fuel producer, rather than a reactor developer, is to determine what products to make and which reactor system to use. The operating parameters of any reactor system designed to produce pyrolysis oil, especially temperature, can be altered to change the pyrolysis oil product composition and yield. Different feedstocks will produce different pyrolysis oil compositions and by-products, e.g. amorphous silica from rice hulls or rice straw, fatty acids from pine. Finally, feedstock pretreatment and/or catalysis, or reactor-bed catalysis can be used to improve specific product yields (7). Reactor system developers need to examine what they can produce and make this information available to chemical manufacturers and suppliers/owners of biomass feedstocks. This assumes that analysis of die entire liquid product from thermal conversion can be made, including quantitative analysis for any compounds that are being considered for recoveiy. Physical characterization - pH, viscosity, solids content, etc.is also needed. However, what can be produced is of no value, if it cannot be recovered or used economically. This involves examining the trade-offs between yield and current commercial value, recovery costs, and potential commercial value,... 

Most previous work on production of high sugar pyrolysates has used wood as feedstock, which differs in many respects from the herbaceous material of interest to most agricultural operations. For example, herbaceous materials contain more potassium than woody materials (II). Since the catalytic activity of potassium under conditions of pyrolysis are considerably greater than for calcium (12), it may be more difficult to thermally depolyermerize herbaceous plant materials. However, potassium is also more water soluble than calcium and thus easier to remove. TTiis study investigates various pretreatment options for their ability to increase pyrolytic yields of levoglucosan from herbaceous feedstocks. 

The use of various pretreatments of the plastic wastes such as chemical soaking, heat treatments, microwave, and plasma treatments, etc. in conjunction with the pressurized method might be attractive areas for future research. Co-pyrolysis with other wastes such as food wastes is also plausible. Much work has been carried out on other pressurized carbonization methods such as biomass hydrothermal carbonization [111, 112]. If an industrial process is to emerge from the research, the combined use of various carbon sources would be attractive for economy-of-scale purposes. Producing porous carbons for further applications from plastic wastes would not only yield useful products from cheap precursors, but it would also help reduce the problems associated with the ever-growing plastic waste stream. 

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