(579b) Biomass Conversion to Acrylonitrile Monomer-Precursor for Production of Carbon Fibers

The industrial sector anticipates an 11-18% annual increase in the market for carbon fiber, specifically driven by motivation to reduce weight for vehicles [1]. Currently, micron-sized carbon fibers which meet mechanical specifications (250 ksi tensile strength and 25 Msi Young’s modulus) for automotive applications are made from poly-acrylonitrile (PAN), obtained from acrylonitrile (ACN) synthesized using propylene and ammonia. World ACN production in 2010 was 5.7 million tons, and is highly dependent on volatility of propylene prices. Additionally, production of propylene (a byproduct of naphtha cracking for ethylene) is undergoing reduction due to growth of the natural gas-derived ethane-based process for production of ethylene.

Previous attempts to directly make carbon fiber from biomass-derived lignin have largely met with failure due to the fiber’s inability to meet the required specifications.  Furthermore, attempts to make carbon fiber via the ACN route from bio-derived sources have been limited to the conversion of glycerol obtained as a byproduct from biodiesel production from oils.  However, the glycerol to ACN pathway has been found to be economically unattractive compared to the conventional petroleum based ACN pathway. In light of these facts, the goal of this work is to develop cost-effective process with low environmental impact, for production of ACN utilizing biomass derived sugars with comparable mechanical properties that can directly replace conventional ACN.

Southern Research is developing a biomass to ACN (B2ACN) process under a cooperative agreement with the Department of Energy [2].  B2ACN is a multi-step catalytic fixed bed process for conversion of sugars from non-food biomass to ACN at mild conditions. The process utilizes known pretreatment methods for recovery of sugars from any type of biomass. In the first reaction step, sugars are converted to oxygenates using a novel multi-functional catalyst, oxygenates are then converted to a gas phase intermediate followed by conversion of the intermediate to acrylonitrile. The results and initial estimates show a significant reduction in greenhouse gas (GHG) emissions of up to ~37% and cost reduction of up to ~22% compared to conventional ACN. The GHG benefits and cost reduction are achieved by using mild conditions, minimizing catalyst use, minimizing separation costs, increasing net carbon yield and use of industrially acceptable fixed bed reactors. 

Process development of the individual reaction steps is being carried out in laboratory scale reactors under Phase 1 of the project. Following successful Phase 1 development/testing, a scaled up integrated bench-scale reactor system will be designed and demonstrated.  The Phase 1 lab-scale reactor systems have been constructed and several multifunctional catalyst candidates have been prepared for testing.  This paper will describe the initial results of the B2ACN process for conversion of biomass-derived sugar to acrylonitrile.

[1] Global market opportunities for carbon fiber: Carbon fiber world conference, Washington DC 2011

[2] http://energy.gov/eere/articles/energy-department-announces-11-million-a...