Oxidative ammonolysis of technical lignins and lignites

Thesis (MSc)--Stellenbosch University, 2003.

ENGLISH ABSTRACT: Today there is renewed interest in using soil improvers with fertilising capability as the use of inorganic fertilisers results in ground water pollution through leaching and formation of nitrates in plant materials. Lignin is an important precursor of humic material in soils and with modification, can be used as a raw material for producing slow release nitrogenous fertilisers. This project focussed on the use of industrial residues such as technical lignins which are produced by the South African pulping industry as well as low grade coals such as lignite occurring in South Africa, for the production of high-grade humic substances like Novihum TM, using the special technology developed by the Institute of Plant and Wood Chemistry of the Technical University of Dresden in Germany. Technicallignins derived from kraft lignin, sugar cane baggase, autohydrolysis lignin with a trade name Sucrolin, a calcium lignosulphonate and South African lignites mined in the Kraaifontein and BraekenfeIl areas as well as German brown coal were subjected to oxidative ammonolysis with the aim to produce slow release nitrogenous fertilizers. Curie Point Pyrolysis GCIMS was used to determine the structural composition of the raw materials and products. Oxidative ammonolysis reactions were carried out on a laboratory and a pilot plant scale. Highest nitrogen contents were obtained with Sucrolin lignin followed by the lignite from Germany. The amount of nitrogen that could be fixed with oxidative ammonolysis varied between 1.44 - 10% for the various raw materials. The CIN ratios obtained were in the range between 5 - 34. Marginal differences were observed between the materials modified on lab and pilot plant scales. There were improvements in the total incorporated nitrogen when the raw materials were pre-activated with oxidising agents such as hydrogen perxide and a fungal species, Phanaerochateae chrysosporium prior to oxidative ammonolysis. Variable amounts of differently bonded nitrogen forms were obtained for the materials tested due to their structural differences.

AFRIKAANSE OPSOMMING: Daar is deesdae hernude belangstelling in die gebruik van grondverbeteringsmiddels wat ook 'n bemestingsfunksie het, aangesien die gebruik van anorganiese kunsmis besoedeling van grondwater deur uitlogingen insypeling veroorsaak, wat weer tot die vorming van nitrate in plantmateriaallei. Lignien is 'n belangrike voorloper van humiese materiale in grondstowwe en kan dmv modifisering gebruik word as 'n grondstof vir die produksie van stadigstikstof vrystellende nitro gene kunsmisstowwe. Die huidige projek het gefokus op die gebruik van industriële residue en tegniese ligniene wat deur die Suid- Afrikaanse pulpnywerheid geproduseer word, sowel as lae-graad steenkool soos ligniet wat in Suid-Afrika aangetrefword, vir die produksie van hoë-graad humiese stowwe soos Novihum TM. Hierdie produk is mbv spesiale tegnologie deur die Instituut van Plant- en Houtchemie van die Tegniese Universiteit van Dresden in Duitsland ontwikkel. In hierdie ondersoek is verskeie Suid-Afrikaanse tegniese ligniene soos Kraft lignien, suikerriet bagasse, 'n outohidrolise lignien met die naam van Sucrolin en 'n kalsiumlignosulfonaat sowel as SA ligniete, afkomstig van Brackenfell en Kraaifontein, gebied en Duitse bruinkool, aan oksidatiewe ammonolise onderwerp om sodoende verskillende, stadigvrstellende, stikstofryke kunsmisstowwe te vervaardig. Curie Punt Pirolise GC/MS is gebruik om die chemiese struktuur van die grondstowwe en produkte vas te stel. Oksidatiewe ammonolise reaksies is op 'n laboratorium en loodsaanlegskaal. uitgevoer. Die hoogste stikstofinhoud is met Sucrolin lignien verkry, gevolg deur die ligniet van Duitsland. Die hoeveelheid stikstof wat dmv oksidatiewe ammonlise bereik kon word, het tussen 1.44 en 10% gewissel. Die CIN verhoudings wat verkry was, het varieer tussen 5 en 34. Marginale verskille is tussen laboratorium - en loodsaanlegsskaal gemodifiseerde grondstowwe waargeneem. Daar was verhogings in stikstofinhoud wanneer die grondstowwe vooraf met oksiderende middels soos waterstofperoksied of swamkultur soos Phanaerochatae chrysosporium, aktiveer is. Stikstof is op verskillende maniere en in verskillende hoeveelhede gebind.

Masters