Modified dolomite-based catalyst for biofuel production via catalytic pyrolysis of waste cooking oil

The limited availability of conventional energy resource, critical issues in food security and significant environmental problems have driven to seek renewable and sustainable resource of liquid fuel. In this respect, catalytic pyrolysis of waste cooking oil (WCO) represents a promising option for the future to produce value added biofuel. In this study, Malaysian Dolomite was successfully used as a base solid catalyst in converting WCO to green biofuel using lab-scale fractionated catalytic pyrolysis system. The biofuel produced was in the range of gasoline, kerosene and diesel fraction with low acid value and low amount of aromatic hydrocarbon content as compared to biofuel produced by several commercial catalysts. Calcined Malaysian dolomite (CMD900) under flow of N2 at 900°C produced catalyst with very high activity due to decomposition of CaMg(CO3)2 phase and formation of MgO-CaO phase. In addition, Malaysian dolomite showed high reactivity with 76.5% in total liquid hydrocarbon with 23.5% amount of oxygenated compound content in pyrolysis oil production. In order to get a higher conversion of WCO and yield in pyrolysis oil production, Malaysian dolomite was modified with dispersion of various transition metals via different techniques of catalyst preparation. The modified Malaysian dolomite increased the surface area (12.02 m2/g to 18.22 m2/g) and lesser average pores diameters reduced (63.07 nm to 48.20 nm). In addition, modified Malaysian dolomite catalysts with dispersion of 5% Nickel via precipitation technique showed a high basicity properties with capability to desorb more CO2. The conversion of WCO were totally improved from 36.0 wt% to 68.0 wt%, while the yield of pyrolysis oil increased from 13.4 wt % to 36.4 wt%. The pyrolysis oil produced using this catalyst showed high reactivity with 80.2% in total liquid hydrocarbon with only 19.8% oxygenated compound content. The influence of the reaction variables such as the operating temperature, operating time, ratio catalyst to WCO and flow of nitrogen gas in biofuel production were optimized using RSM for maximum conversion of WCO as maximum yield of pyrolysis oil and yield of desired product (C8-C24). The results showed that optimum conditions for catalytic pyrolysis were at 410°C, 5.50 wt% catalyst loading, 60 min at 175 cm3/min nitrogen gas flow producing 92.0 wt% of conversion with 62.9 wt% yield of pyrolysis oil and 68.9% of desired product (C8-C24). The biofuel generated from catalytic cracking of WCO meets requirements of diesel and hydrocarbon biofuel standards for fuel application. Waste-to-wealth can be achieved using this cheaper technology due to waste cooking oil as feedstock, local carbonate mineral as catalyst and pyrolysis oil for potential biofuel is generated.

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