(142c) Low Pressure Hydrodeoxygenation of Liquid Phase Pyrolysis Oil and Refinery Intermediates

Various concepts have been developed to cover the increasing energy demand in transportation. Conventional combustion engines are not expected to be replaced by alternatives in the near future. This makes the production of fuels and substitute fuels out of biogenic feedstock indispensable. A suitable pathway for biofuel production is direct biomass liquefaction via pyrolysis.

In liquid phase pyrolysis¹, biomass is processed by a liquid heat carrier. In the bioCRACK process^2,3, crude oil refinery intermediates such as vacuum gas oil are used as heat carrier. The bioCRACK process combines the pyrolysis of biomass with the cracking of the heat carrier. Non-polar biomass fragments are directly transferred into the non-polar heat carrier oil. The biogenic carbon load of the heat carrier oil is processed in the refinery without further treatment. Polar biomass fragments are transferred into the liquid phase pyrolysis oil (LPP oil). Due to the high water content, high corrosivity and other negative properties, LPP oil needs an intensive upgrade prior to usage as fuel for combustion engines.⁴ To achieve these standards, hydrodeoxygenation (HDO) is proposed.

LPP oil was further upgraded in a lab scale hydrodeoxygenation (HDO) reactor. To reduce investment costs for industrial application, a crude oil refinery compatible process is required. Therefore, low pressure co-hydrodeoxygenation of liquid phase pyrolysis oil and heavy gas oil was investigated.

HDO was carried out in a plug flow reactor from Parr Instrument Company with inline-sulfided metal-oxide catalyst in two steps. Direct Co-Processing of LPP oil with refinery intermediates led to plugging. To avoid plugging, low temperature HDO prior to Co-processing for dewatering and hydrophobising was suggested. Both steps were performed at 80 bar and at liquid hourly space velocity (LHSV) of 1 h^-1. In the first step (HDO 1), LPP oil was hydrodeoxygenated at 300°C, in the second step (HDO 2), the product of HDO 1 was mixed with heavy gas oil (10 wt.% HDO1/ 90 wt.% heavy gas oil) and hydrodeoxygenated at 400°C. After the first step, dewatering and hydrophobation of LPP oil was achieved, making the product of HDO 1 miscible with heavy gas oil. In the second step, LPP oil was finally upgraded to a product with fuel quality (Table 1).

Table 1. Elemental composition and water content of educts and products compared to diesel

HDO	Water content [wt.%]	C [wt.%]	H [wt.%]	Rest = O [wt.%]	N [wt.%]
LPP oil	58.9	20.8	9.4	69.5	<1
Heavy gas oil	0.0	85.4	14.6	0.0	<1
HDO 1	1.95	76.3	11.6	11.7	<1
HDO 2	0.01	85.3	14.7	0.0	<1
Diesel	<0.02	86.3	13.7	0.0	<1

1 N. Schwaiger, D. C. Elliott, J. Ritzberger, H. Wang, P. Pucher and M. Siebenhofer, Green Chem., 2015, 17, 2487–2494.

2 K. Treusch, J. Ritzberger, N. Schwaiger, P. Pucher and M. Siebenhofer, R.Soc.open sci., 2017, 4.

3 J. Ritzberger, P. Pucher and N. Schwaiger, 2014, 39, 1189–1194.

4 Q. Zhang, J. Chang, T. Wang and Y. Xu, Energy Convers. Manag., 2007, 48, 87–92.