Vacuum-pyrolysis oils fractionation

Solvent-Refined Coal Process. In the 1920s the anthracene oil fraction recovered from pyrolysis, or coking, of coal was utilized to extract 35—40% of bituminous coals at low pressures for the purpose of manufacturing low cost newspaper inks (113). Tetralin was found to have higher solvent power for coals, and the I. G. Farben Pott-Broche process (114) was developed, wherein a mixture of cresol and tetralin was used to dissolve ca 75% of brown coals at 13.8 MPa (2000 psi) and 427°C. The extract was filtered, and the filtrate vacuum distilled. The overhead was distilled a second time at atmospheric pressure to separate solvent, which was recycled to extraction, and a heavier liquid, which was sent to hydrogenation. The bottoms product from vacuum distillation, or solvent-extracted coal, was carbonized to produce electrode carbon. Filter cake from the filters was coked in rotary kilns for tar and oil recovery. A variety of liquid products were obtained from the solvent extraction-hydrogenation system (113). A similar process was employed in Japan during Wodd War II to produce electrode coke, asphalt (qv), and carbonized fuel briquettes (115). 

Fractionation of Pyrolysis Oils. Pyrolysis oil obtained from the vortex reactor was fractionated according to the scheme shown in Figure 3. Whole oil (1 kg) was dissolved in ethyl acetate (EA) on a 1 1 (w/w) basis. The oil was then vacuum filtered through filter paper to remove fine char. Upon standing, the EA/pyrolysis oil separated into two phases-an organic rich, EA-soluble phase and an EA-insoluble phase. Most of the water formed during pyrolysis is contained in the EA-insoluble phase. The EA-soluble portion of the oil was washed with water (2 x 75 mL) to remove the remaining water-soluble derived products. 

Fluid catalytic cracking (FCC) has been used since the 1950s to turn heavy distillates (vacuum gas oil) into a series of light and dense fractions. The FCC catalysts can also be used as pyrolysis catalysts. 

In order to simulate the condensing system of an industrial vacuum pyrolysis plant which consists of two condensing packed towers continuously operating, the liquids collected in each trap were mixed and then evaporated at 45 "C during half an hour in a rota-vapour (Biichi, RE 111). The heavy fraction which remained in the flask corresponds to the oil from the first condensing tower and is called bio-oil , while the evaporated fraction which consists of water and light organic compounds corresponds to the aqueous phase of the second tower and is called "aqueous phase . 

Figure 3. Pyrolysis of shale oil vacuum distillate saturate fraction at 450 °Cfor 30 min. Key , n-alkanes and , l-alkenes.

Figure 4. Pyrolysis ofshale oil vacuum distillate saturate fraction at 450 °C. The yield is the sum of n-alkane plus l-alkene for the indicated chain length.

The sequential elution chromatographic technique has been found particularly helpful in separating whole oil produced by vacuum pyrolysis of wood into chemically distinguishable fractions. More than 30 of the P.C.U. oil that eluted first (FI to Fll) could bo analysed by GC and GC-M.S with less unambiguity. 

The oil fractions collected on the six hearthes of a wood vacuum pyrolysis process demonstration unit have been upgraded to hydrocarbons in the C5-C10 range on a ZSM-5 catalyst. The use of a precoker at reaction temperature has been demonstrated and C5-Ci 0 hydrocarbons yields of the order of 30 wt% of oil fed, have been reached. GC/FTIR analyses of the heavier liquids collected after the precoker indicate that the acids in the oils play a dominant role in the gas phase reactions occurring in the precoker. 

In the present paper we report a stud.y of the conversion over H-ZSM-5 catalysts, of the fractionated oil produced by vacuum pyrolysis of Populus Deltoides wood in a Process Demonstration Unit (PDU) ( ). 

Pyrolysis of Shale Oil Crude and Vacuum Distillate Fractions... 

A 35° API gravity Devonian oil from the WCSB in Alberta, Canada was topped at 35°C for 2.5 h under vacuum and the C9+ fraction was used as the starting material for the pyrolysis experiments The topped oil stable carbon isotope ratio is — 29.47%o relative to PDB. The composition of the topped oil is 64% saturates, 23% aromatics, 6.5% resins and 6.5% asphaltenes. The oil falls into the Cynthia shale oil family of Exploration Staff, Chevron Standard Limited (1979) and Allan and Creaney (1991). Oil pyrolysis was performed isothermally in sealed gold tubes at temperatures ranging from 350°C to 400°C, time ranging from 3 to 33 days and pressure of 650 bars. Details of the experimental procedure were discussed previously (Hill et al, 1994, 1996, 2003). 

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