Diesel-like hydrocarbon fuels by catalytic cracking of fat, oils, and grease (FOG) from grease traps

This work aims to investigate systematically the catalytic cracking of residual fat, oils, and grease (FOG) from grease traps to produce heavy diesel-like hydrocarbon fuels. The experiments were carried out in batch mode at 450 °C and 1.0 atm, with 5, 10, and 15% (wt.) Na2CO3 using a laboratory scale borosilicate-glass reactor of 143 ml, and with 10% (wt.) Na2CO3 in a pilot scale stirred tank slurry reactor of 143 l. The organic liquid products (OLP) were physical chemistry analyzed for acid and saponification values, density, kinematic viscosity, refractive index, flash point, and copper strip corrosion. FT-IR provided the qualitative chemical composition of OLP and heavy diesel-like fraction. The chemical compositions of OLP and heavy diesel-like hydrocarbon fuel determined by RMN and GC-MS. The laboratory experimental data showed an OLP yield ranging from 60.50 to 65.40% (wt.), a coke yield ranging between 7.50 and 9.80% (wt.), and a gas yield ranging from 16.30 to 22.06% (wt.), while pilot scale data showed an OLP yield of 66.57% (wt.), a coke yield of 9.73% (wt.), and a gas yield of 18.24% (wt.). In addition, the yield of OLP obtained in laboratory scale shows a slight increase with Na2CO3 content, while the density, kinematic viscosity, acid value, and saponification value decreases in an exponential fashion with Na2CO3 content. The OLP acid values varied from 19.08 to 71.50 mg KOH/g, the density between 0.827 and 0.867 g/cm3, and the kinematic viscosity from 3.90 to 6.35 mm2 s−1 for laboratory data, while in pilot scale, the OLP acid value was 14.97 mg KOH/g, density of 0.820 g/cm3, and the kinematic viscosity of 3.485 mm2 s−1. The yield of heavy diesel-like hydrocarbon fraction average 19.35% (wt.) with an acid value of 7.27 mg KOH/g, density of 0.812 g/cm3, and kinematic viscosity of 3.51 mm2 s−1. FT-IR, RMN, and GC-MS analysis of OLP and heavy diesel-like hydrocarbon fraction confirms the presence of functional groups characteristic of hydrocarbons (alkenes, alkanes, ring-containing alkenes, and ring-containing alkanes, cycloalkenes, cycloalkanes, and aromatics) and oxygenates (carboxylic acids, ketones, fatty alcohols, and dienes). The GC-MS analysis of OLP and heavy diesel-like hydrocarbon fraction obtained in pilot scale with 10% (wt.) Na2CO3 identified in OLP 76.97% hydrocarbons (39.44% alkenes, 31.91% alkanes, 4.12% ring-containing alkenes, and 1.50% ring-containing alkenes) and 23.03% oxygenates (12.14% carboxylic acids, 6.98% ketones, 1.90% fatty alcohols, and 2.01% dienes). The heavy diesel-like hydrocarbon fuel is composed by 69.27% (area) hydrocarbons (32.04% alkenes, 25.62% alkanes, 3.93% ring-containing alkenes, 0.98% ring-containing alkanes, 1.35% cycloalkanes, 4.88% cycloalkanes, and 0.47% aromatics) and 31.75% (area) oxygenates (4.80% carboxylic acids, 4.85% ketones, and 21.08% fatty alcohols). The physical-chemistry properties and chemical composition of heavy diesel-like hydrocarbon fuel obtained by catalytic cracking of residual fat, oils, and grease (FOG) from grease traps with 10% (wt.) Na2CO3 shows the process is technically feasible.