Optimisation of pyrolysis oil through microwave-induced in-situ co-pyrolysis of waste truck tire and empty fruit bunch Creator

Abstract

Thermal decomposition of waste via pyrolysis is capable of producing pyrolysis oil. However, the produced oil tends to be unstable due to its poor physiochemical properties such as high sulphur content, high acidic pH and high moisture content, and hence limiting its potential implementation as a fuel. Therefore, a microwave-induced in-situ catalytic fast co-pyrolysis study was proposed, serving to upgrade the pyrolysis oil to possess fuel-like properties. In the present study, copyrolysis of empty fruit bunch (EFB) with waste truck-tire (TT) were utilised with TT being selected because of its high volatile carbon content level and high heating value. Carbonaceous susceptor was also used to elevate the pyrolysis temperature. Firstly, pyrolysis temperature of microwave-induced fast pyrolysis of TT and EFB was optimised individually for increased pyrolysis oil yield and energy recovery. It was found that temperature of 500°C produced highest TT and EFB pyrolysis oil yields, which were approximately 38.12 and 38.26 wt%, respectively. TT pyrolysis oil was observed to consist of high calorific value (42.39 MJkg-1) and high energy yield (40.55 wt%) but with high sulphur content. EFB was found to produce phenolic-rich pyrolysis oil with lower flash point, consisting of highly oxygenated compounds (90%) and high-water content (30 wt%). To overcome the lack of fuel-like properties, pyrolysis oil yield and energy recovery optimisation of co-pyrolysis between TT and EFB were conducted using responses surface methodology (RSM). Three parameters were examined, namely: 1) EFB to TT ratio, 2) pyrolysis temperature and 3) carbonaceous susceptor loading. It was observed that optimum conditions of 505°C pyrolysis temperature, 65% of EFB to TT ratio and 60g of susceptor loading produces highest pyrolysis oil yield (39.87 wt%) and energy recovery (60%). Such a co-pyrolysis configuration produced olefin correlate rich pyrolysis oil (39%) with high selectivity of D-limonene (28.6%) and 20% higher energy recovery as compared to TT pyrolysis oil. However, the liquid-oil still has a significant number of sulphur (0.05%) and acidic compounds (0.83%), mainly originating from TT and EFB. Thus, a microwaveinduced in-situ catalytic fast co-pyrolysis of TT with EFB, using catalysts, was been carried out. Two parameters were studied: 1) catalyst types, namely activated carbon (AC), clay (CL) and calcium oxide (CaO), and 2) catalyst loading (ranging from 20 to 60%). It was shown that catalytic cracking decreases acidity of pyrolysis oil from 4.70 (un-catalytic) to 5.12 (AC20), 4.98 (CL20) and 5.65 (CaO20). As compared to CL and CaO, catalytic cracking using AC increased desirable hydrocarbon fractions (olefinic and monoaromatic) with highest selectivity of benzene, toluene, ethylbenzene and xylene (BTEX) hydrocarbons, indicating that such a catalytic cracking favours production of pyrolysis oil with fuel-like properties. It is, thus, parametrically determined that at 500°C pyrolysis temperature with 65:35 ratios (EFB/TT), 60g of susceptor, 20% of catalyst loading using AC at reaction time of 30 minutes, pyrolysis oil with highest yield of 38.92 wt% as well as highest energy recovery of 60.77% can be produced. The physiochemical properties of the pyrolysis oil were also determined to be similar to that of petroleum diesel but with a slightly lower flashpoint (<30oC). Thus, this work successfully demonstrated that microwave-induced catalytic copyrolysis of TT/EFB, using AC as catalyst, is a promising technique to recover diesellike fuel from waste feedstocks, carrying great potential for use as supplemental alternative fuel or for value-added petrochemical products recovery.