(81b) Pyrolysis of Concentrated Pulping Liquors to Generate Highly Deoxygenated Organics for Bio-Based Fuels and Chemicals Production

PYROLYSIS OF CONCENTRATED PULPING LIQUORS TO GENERATE HIGHLY DEOXYGENATED ORGANICS FOR BIO-BASED FUELS AND CHEMICALS PRODUCTION

Jamie St. Pierre, Paul Rudnicki, Sedat Beis, and Adriaan van Heiningen

University of Maine Department of Chemical and Biological Engineering, Jenness Hall, Orono, ME 04469

jstpierre@umche.maine.edu

Abstract

The development of robust processes and the improvement of existing processes that produce liquid transportation fuels and chemicals using sustainable feedstocks is a rapidly growing field due to concerns surrounding global warming and the desire to reduce usage of non-renewable resources.  In the northeastern United States particularly, liquid fuels and chemicals produced from lignocellulosic materials such as woody biomass are attractive due to the abundance and renewable nature of the feedstock, its ability to fix carbon dioxide during its growth period, and decades of experience utilizing sustainable harvesting practices.  Black liquor, the main by-product of pulping processes, is rich in organic material, such as degraded lignin and hemicelluloses, as a result of delignification and alkaline peeling reactions respectively, that occur during cooking of the lignocellulosic biomass.  Due to its significant organic content and large-scale annual production of approximately 200 million dry tonnes globally, it has been of interest as a source of renewable carbon for the production of liquid fuels and chemicals for almost a century.

The current work focuses on pyrolysis of concentrated soda-anthraquinone (AQ) black liquor (40 wt% dry solids), in particular the dissolved lignin, to produce a significantly deoxygenated organic fraction while retaining a high fraction of the organic carbon.  Sodium formate is added to black liquor at various charges to investigate the effect on organic product distribution, quality and yield.  Formate is utilized in this work as an in situ source of reactive hydrogen as it has been shown in previous studies to aid in hydrodeoxygenation as well as in reducing the amount of organic carbon lost as char during pyrolysis.  The results demonstrate that as the formate loading is increased the organic yield increases while the carbon sequestered in the char decreases.  The product distribution and quality of the organic fraction, however, remain fairly constant irrespective of the formate loading.  The main products in the pyrolysis oil are phenolic in nature with varying degrees of alkylation on the aromatic ring.  Other products include ketones and carboxylic acids.  Organic yields of up to 38 wt% on black liquor organics and a reduction of the carbon lost as char (from 49 wt% to 24 wt% of black liquor carbon) can be realized with this process at 50 wt% sodium formate loading on black liquor dry solids.  The organic fraction is significantly deoxygenated with an O:C ratio of 0.1 based on black liquor organics (initial O:C of black liquor organics of 0.4) and an increased higher heating value (HHV) of 30 MJ/kg from 12 MJ/kg for the black liquor dry solids.  Product yields and distributions after pyrolysis of concentrated black liquor for the various sodium formate loadings will be presented.