CO2-Binding of ammonoxidized lignins and their use as soil improvers (COBAL)

• Applicant: Professorin Dr. Heike Knicker
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2008 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 68851105

Lignin and other ligneous biomaterials can be converted into artificial humic substances by oxidative ammonolysis (ammoxidation). This reaction employs oxygen and aqueous ammonia to break aromatic lignin moieties and to introduce nitrogen in the form of ammonia salts, urea, amides, and amines. The resulting “N-lignin” is an organo-mineral fertilizer which can be used for rehabilitation of degraded soils. One special value of N-lignins is the slow-nitrogen releasing effect, which is caused by the different hydrolysis rates of the different nitrogen binding forms generated upon ammoxidation. Secondary amines are able to bind carbon dioxide in the form of 2:1 complexes which can be described both as addition products and as ion pairs (dialkylammonium dialkylcarbamates, dialcabs). This chemical behaviour is applied in the current project to use N-lignins as a means of CO2 fixation. Employing (di)methylamine instead of ammonia in the ammonoxidation, the content of secondary amines and amides as CO2-binding sites in N-lignin can be additionally increased. CO2-Binding of Ammoxidized Lignins - abbreviated “COBAL” as short term - is the key issue of the present project. This comprises studies as to the underlying chemistry and comprehensive analytical characterization of intermediates and products, involving isotopic labelling (15N, 13C) and NMR spectroscopy in liquid and solid state as the main methodic approaches, and the testing of the products in soil rehabilitation, agriculture and horticulture. The advantages of the process are the simultaneous conversion of two bulk “by-products” (CO2 and lignin) into a value-added product of high practical relevance (organo-mineral fertilizer which humic properties) that is returned into the natural cycle, the large-scale applicability based on the bulk availability of lignin and CO2, the high demand for high-grade soil improving materials to combat the progressive global desertification, and the products´ environmental compatibility.

• DFG Programme: Research Grants
• International Connection: Austria
• Participating Person: Professor Dr. Falk Liebner