Valorizing lignocellulose to Ethylene Glycol: catalysis, catalyst deactivation and conceptual process design

Title : Valorizing lignocellulose to Ethylene Glycol: catalysis, catalyst deactivation and conceptual process design

Abstract:

To mitigate climate change and decrease society’s reliance on fossil resources, the industry must develop new processes to produce fuels and chemicals from renewable resources. A promising route to renewable chemicals is the hydrogenolysis of carbohydrates to ethylene glycol using a bifunctional catalyst system based on homogeneous WOx and heterogeneous Raney-Ni. This catalyst system shows good selectivity with clean glucose and cellulose, but it readily deactivates with real lignocellulosic feedstock. The lecture will discuss the catalyst poisoning and present integrated process concepts to mitigate these undesired effects.

Catalyst poisoning – The lignin contained in lignocellulose fouls the hydrogenation catalyst, as expected. But more severe poisoning comes from other contaminants. The N- and S-components present in extractives are much more harmful for the Raney-Ni catalyst, while the basic components of ash, particularly Ca²⁺, kills the WOx catalyst.  These learnings allowed us to define quality criteria for the hydrogenolysis feed.

Process concepts – We then developed two process concepts to mitigate catalyst poisoning.
A first concept removes all catalyst poisons (lignin, extractives and ashes) by pre-treatment with an acidic mixture of water and organic solvent. Process-own by-products such as acetic acid and light alcohols are selected as acid and organic solvent to ease the closure of recycle streams.

A second and more ambitious process concept removes the extractives and ashes by a simple acid wash and runs the hydrogenolysis in a water-organic medium. The water-organic medium appears to depress the fouling by lignin but, regrettably, also decelerates the cellulose hydrolysis. 

Both process concepts are delivering a complex and diluted product stream for workup to high-purity products. The simple concept of distillation resistance unravels some of the challenges of the product workup.

Audience Take Away Notes:

• The importance of considering real feedstock and its contaminants
• The value of operating under suboptimal conditions, e.g. low catalyst loading, to magnify eventual catalyst poisoning
• The need to look beyond catalysis to integrated process, incl. product recovery, to detect new issues that could be created by solving identified problems.

Biography:

Jean-Paul Lange is Professor in Chemical Biorefining at the University of Twente, the Netherlands, where he is exploring thermo-chemical and catalytic processes to convert biomass and plastic waste to fuels and chemicals. He recently closed 35 years of career as senior Principal Science Expert at Shell Research & Technology. His research embraces heterogeneous catalysis, chemical engineering, conceptual process design, manufacturing economics and technology strategy. Jean-Paul Lange is co-author of >120 patent series, 85 scientific publications, 10 book chapters and co-editor of one scientific book.