7
6
1.1e+08
CCR = 0.42% API = 41.2 Aliphatic ~83% Aromatic <2% Oxy-aliphatic <15%
1e+07 2e+07 3e+07 4e+07 5e+07 6e+07 7e+07 8e+07 8e+07 1e+08
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9
C – C
+
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2
15.00
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35.00
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45.00
50.00
55.00
60.00
65.00
8 7
1
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9
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3
Figure 4 Composition of thermal pyrolysis oil derived from mechanically recycled LDPE, including the major species identified by GC-MS
Polyolefins (PP, LDPE, HDPE) will be the easiest waste plastics for circular manufacturing due to their high effective hydrogen index (EHI) and low Conradson carbon residue (CCR) contents. Valmet provided a py-oil sample originating from mechanically recycled LDPE for further characterisation and testing by BASF. A more detailed analysis of this thermal py-oil using GC combined with mass spectroscopy revealed evidence of olefins and dienes as major substances, resulting in about 83% aliphatic compounds, less than 2% aromatic compounds, and less than 15% oxy-aliphatic compounds (see Figure 4 ). This waxy fraction from thermal py- oil is mainly composed of heavier waxes (>C28), making a suitable feedstock for FCC with or without diluting it with gasoil. Catalytic measurements were made using an Advanced Catalytic Evaluation (ACE) fluid bed reactor ( Kayser, 1997 ). ACE was introduced in 1997 as a fixed-fluid bed laboratory cracking system, which has rapidly taken over as the industry standard for bench-scale FCC testing compared to fixed-bed MAT units ( Clough, et al., 2017 ). ACE was operated using a steam- deactivated catalyst at a temperature of 550°C, 60-second injection time, 1.125-inch injector height, and constant time on stream protocol to vary catalyst-to-oil ratios between four
and eight. Pyrolysis oil was tested at 100%, although typical commercial application loadings are around 10%. Naphtha product was defined as C5 to 232°C, LCO as 232°C-360°C, and HCO as 360°C and higher. This waxy LDPE py-oil, containing 10% naphtha, 33% LCO, and 57% HCO, was successfully and fully upgraded to transportation fuels or chemicals, without any dilution with gasoil, through ACE by assessing two commercial BASF catalysts, including: FCC1 oriented towards naphtha maximisation. v FCC2 oriented towards LPG olefins maximisation. Table 1 shows results obtained for both catalysts, FCC1 and FCC2, in terms of product yields at a 7.0 catalyst-to-oil ratio after the upgrading of this waxy LDPE py-oil. Due to the properties of this waxy LDPE py-oil (EHI ~1.9 and CCR ~0.4 wt%), which contains mainly aliphatic compounds, the waxy fraction of the LDPE py-oil was fully converted into valuable products, such as naphtha and LPG hydrocarbons. For FCC2, which is specifically designed for maximising LPG olefins, yields of 45.4 wt% propylene and C4 olefins can be achieved compared to 25.8 wt% for FCC1, which is specifically designed for naphtha production (Table 1). The olefinicity, which is the ratio of cracking (olefin producing) and hydrogen-
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