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U okviru ove doktorske disertacije istraživana je metanoliza otpadne svinjske masti u prisistvu KOH, CaO ili negašenog kreča na umerenim temperaturama (ispod tačke ključanja metanola) i molskom odnosu metanol:masna sirovina, 6:1. Radi poređenja i doprinosa boljem razumevanju samog procesa, pored otpadne svinjske masti, kao izvori TAG korišćene su još i komercijalna „čista“ svinjska mast i „čista“ svinjska mast koja je termički tretirana pod uslovima procesa pečenja svinjskog mesa. Metanoliza je izvođena u šaržnom reaktoru sa mešanjem u prisustvu homogenog (KOH) i čvrstog katalizatora u obliku praška (komercijalni CaO i negašeni kreč) i protočnom reaktoru sa nepokretnim slojem čestica negašenog kreča. Dobijeni proizvodi sinteze su prečišćavani poznatim postupcima: „pranje“ vodom i tretman sa natrijum–karbonatom i metanolom. Finalnom proizvodu su određena svojstva od značaja za njegovu primenu kao dizel goriva. Realizovanim istraživanjima ostvareni su svi postavljeni cilјevi doktorske disertacije u pogledu mehanizma i kinetike sinteze MEMK u prisustvu različitih katalizatora, karakterizacije finalnih proizvoda i razvoja tehnološkog postupka za dobijanje biodizela iz otpadne svinjske masti. Kinetika reakcije metanolize zavisi od vrste masne sirovine, vrste katalizatora i temperature. Reakcija metanolize u prisustvu KOH je kontrolisana samo hemijskom reakcijom, dok je u prisustvu čvrstog katalizatora limitirana prenosom mase TAG u njenom početku, a zatim hemijskom reakcijom. Kinetika metanolize otpadne svinjske masti u prisustvu KOH najbolje se opisuje jedno–parametarskim modelom nepovratne reakcije pseudo–prvog reda, dok se kinetika heterogeno katalizovane reakcije dobro opisuje tro–parametarskim modelom koji uključuje promenljivi red reakcije u odnosu na TAG i prvi red u odnosu na MEMK. Konstanta brzine nepovratne reakcije pseudo–prvog reda u prisustvu KOH se povećava sa povećanjem stepena nezasićenosti masnih sirovina sledećim redom: termički tretirana svinjska mast, čista svinjska mast i otpadna svinjska mast. Brzina metanolize masnih sirovina je ista u prisustvu „čistog“ CaO i CaO u obliku negašenog kreča, nezavisno od reakcione temperature. Vrednosti konstante brzine reakcije metanolize u prisustvu CaO ili negašenog kreča povećavaju se u sledećem redu: čista svinjska mast < termički tretirana svinjska mast < otpadna svinjska mast, koji se razlikuje od uočenog za metanolizu istih sirovina u prisustvu KOH... In this doctoral dissertation the methanolysis of waste lard from piglet roasting in the presence of KOH, CaO or quicklime at moderate temperatures (below the boiling point of methanol) and the molar ratio of methanol:fatty feedstockof 6:1. For comparison and contribution to a better understanding of the process, in addition to the waste lard, TGA used as sources are also commercial "clean" pork lard and "clean" pork lard that is thermally treated under the piglet roasting. The methanolysis was carried out in a batch stirred reactor in the presence of homogeneous (KOH) and solid powdered catalysts (commercial CaO and quicklime) and a flow packed–bed tubular reactor filled with bits (2.0–3.15 mm). The products were purified by the known methods: washing with water and the treatment with sodium carbonate and methanol. Certain properties of the final products, important for their use as an alternative fuel, were determined. All goals of the doctoral dissertation regarding the mechanism and kinetics of the synthesis of fatty acid methyl esters (FAMEs) in the presence of various catalysts, characterization of final products and the development of the technological process for obtaining biodiesel from waste lard were achieved. The kinetics of waste lard methanolysis depends on the type of fatty feedstock, the type of catalyst and temperature. The methanolysis reaction in the presence of KOH is controlled only by the chemical reaction while it in the presence of the solid catalyst is limited by the mass transfer of triacylglycerols (TAGs) at its beginning, and then by the chemical reaction. The kinetics of waste lard methanolysis in the presence of KOH is describes by the one–parameter model of an irreversible pseudo–first order reaction, while the kinetics of heterogeneously catalyzed reaction is well described by a three–parameter model that includes the variable reaction order with respect to TAG, and the first order with respect to to FAMEs. The rate constant of irreversible pseudo–first–order reaction in the presence of KOH increases with the degree of unsaturation of fatty feedstocks in the following order: thermally treated pork lard, pork lard and waste lard. The rate of methanolysis is the same in the presence of neat CaO and quicklime, regardless of the reaction temperature... |
