I am interested in doing some research regarding the best catalyst used in the pyrolysis process, to cut down the time of reaction and to get a high product of diesel oil.
The pyrolytic oils from used tires consist a large amount of aromatics and polyaromatics (only 10-15wt% corresponding to aliphatics) then diesel cut from this type of fuel (using catalysts) can not has a good quality. This type of oils can be cracking (via acid catalysis) to produce more aromatics, for exemple.
Fry a power plant with the tires, and produce diesel from crude oil.
Other way: gasification and F-T synthesis.
The severity of catalytic pyrolyse depends on the market requirement for your diesel output. Diesel is a kind of general name, but there are different quality of diesel. Market for diesel can be automotive, truck, train, shipment (bunkker oil), power generation. Each market has his own demands and specification on boiling point range, aromatic content, sulfur content, stability, (cold) flow properties, etc. Severe cracking will results in high yield of diesel, but a very high amounts of aromatics. Aromatics will give a poor quality of diesel in respect to cetane number. For most catalytic pyrolyse oil a very severe hydrotreating activity will be required. (high temperature, high pressure and large amount of hydrogen consumption. In other words the market demands for diesel will determine the severity of catalytic pyrolysis process couples the severity of hydrotreating. There will be always a hydrotreating step required upon catalytic pyrolysis.
The pyrolysis of tires (with and without catalysts) produces a very poor quality, complex mixture with high levels of aromatics, oxygenated hydrocarbons, olefins, sulfur, and many other un-desirable chemical species. This complex mixture is chemically unstable and becomes more viscous with time due to the formation of polymeric and oxygenated materials. In order for this mixture to qualify as a viable diesel fuel, it needs to meet ASTM diesel fuel specifications - it is not even close to meeting such specifications. Oil companys will not accept this crude mixture as input into their refineries and It is not feasible to economically convert this mixture into acceptable fuels. In addition, the gasification of tires produce a poor quality syngas (lots of contaminants) which has been tested by several organizations including ours.
Used tires are not fitable to be pyrolysis directly to diesel oil due to the sulfur, silicon contained in them. One simple method is to gasify the tires into syngas, then to convert the syngas into diesel oil by Fischer-Tropsch synthesis.
In my opinion catalytic pyrolysis can not be successfully run in one step because the catalyst is very rapidly covered by char from tire. A possible way to pyrolyze tire is reported in some our paper:
“Upgraded Fuel from Microwave Assisted Pyrolysis of Waste Tire”, A. Undri, L. Rosi, M. Frediani, P. Frediani, Fuel, 115, 600-608 (2014). DOI: 10.1016/j.fuel.2013.07.058
“Microwave Pyrolysis of Polymeric Materials: Waste Tires Treatment and Characterization of the Value-Added Products” A. Undri, S. Meini, L. Rosi, M. Frediani, P. Frediani, J. Anal. Appl. Pyrolysis, 103, 149-158 (2013). IF 2.487
“Production of hydrocarbons from copyrolysis of plastic and tire material with microwave heating”, P. Frediani, L. Rosi, M. Frediani, A. Undri, S. Occhialini, WO2012110990 (2012)
“Production of hydrocarbons from pyrolysis of tires”, P. Frediani, L. Rosi, M. Frediani, S. Meini, A. Undri, S. Occhialini, WO2012110991 (2012)
The pyrolysis should be a multi-step process and for this reason, Bimetallic catalyst with very high surface area and coke deposition resistant is a possibility.
The choice of the best condition is depended on feedstocks, process configuration, and the properties of the products. There are also different proposed catalysts with regards to production of diesel-like fuel. Soybean was used as feedstocks for catalytic pyrolysis (Calcium oxide catalyst) at reaction temperature (400-550°C). Other oxides such as chromite concentrates and Fe-Cr were mentioned as catalysts for catalytic pyrolysis of hydrocarbons to diesel like fuels.
Used tires is not suitable for pyrolysis directly to diesel oil due to the presence of sulfur, silicon contained in them. One simple method is to gasify the tires into syngas, then convert the syngas into diesel oil by Fischer-Tropsch synthesis.
The system of Maraqah is very complex, that one of Toth is not so easy because tire are a bad heat transfer material
i found from many papers that its not good to use the catalyst in the pyrolysis process
bcs it will affect the product from the point of the mixture of aromatics with the aliphatics . i found that using the catalyst like zeolite will increase the aromatics which give high smell to the product. So the best is to use the pyrolysis without any catalyst ,then the gas oil later will pass to a catalyst to help separation the products .
I have found the left over carbon more valuable than the oil and syngas in my experiments
Mr. Sadasivan, that is interesting observation. Could you please explain why the carbon is more valuable?
As you know, tires (whether they are made from natural rubber or from styrene-butadiene coplymerization) have carbon filler (in good amount) as the main additive. I think that pyrolysis will not give the targeted product. It is worth it to try (steam reforming of used tires using Ni as catalyst or another cat. ). If the product is synthesis gas, then CO & H2 could be used with specific molar ratios in a catalyzed Fischer-Tropsch process to give diesel with a good Cetane number.
Sorry that I am not a daily participant in researchgate.This is for Shiju.If you get hold of the compounding ratios of materials that go into the tyres you would realise the quantity and quality of Carbon used.I am wary of sulphur in the compounding.The carbon I got had a high value of surface area in sq.m/gm-which means it can be a very good adsorbant..
The produced pyrolysis oil from tire is a complex mixture of substances containing saturated, unsaturated, aromatic and oxygenated hydrocarbons, water, sulfur based compounds, carbon, and other inorganic compounds. The pyrolysis oil could be very acidic and unstable. Therefore, the pyrolysis oil is not suitable to use directly as diesel fuel.
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