Citat:
Ursprungligen postat av Fieldleaf
Hej igen. Jag eftersöker något ämne som inte är skadligt men kan bryta ner cellulosa till enklare stärkelseformer. Har suttit och lekt med tanken ganska mycket om att kunna göra etanol från träd (inte i syfte att dricka utan som ett litet experiment i miljösyfte. Så efter att man brutit ner cellulosa måste jäsvampar kunna agera. Alltså ska det inte vara någon allt för skadlig kemikalie. Fast om den går att neutralisera eller filtrera så skulle det gå.
Oftast så är det enzymer som gör detta men det har jag inte tillgång att få fram......
Låt svara forsa fram nu
Mvh: Fieldleaf
Jag har gjort ett projekt inom detta område som tog upp lite av vad du funderar över. Det är dock avsett för industriell skala. Hur som helst: Här är den del som kan intressera dig.
Citat:
Acid catalyzed hydrolysis
The aim of hydrolyzing the cellulose is to produce sugars that are suitable for fermentation
processes. There are mainly two ways of carrying out acid catalyzed hydrolysis of cellulose,
high temperature and low acid concentration or low temperature and high acid
concentration
[3]
. The conversion of cellulose is strongly dependent on temperature.
Experimental data shows that at a certain point, the temperature dependencies seem to change.
The kinetics becomes more sensitive to temperature changes which could mean that the
activation energy for the reaction has changed. This change occurs somewhere around 470 K
and is believed to be a result of a disruption of the partly crystalline structure of cellulose. The
crystallinity makes the cellulose less susceptible to reaction
[4]
. The low- and high temperature
processes require different reaction times and result in different conversions of the cellulose.
A high concentration (14 M) typically results in high conversion at room temperature. On the
other hand, a low concentration (3 M) requires a temperature as high as 520 K in order to give
an acceptable conversion.
Processes usually consist of two-stage hydrolysis. In the first step, hemi cellulose is converted
to pentoses and hexoses at a temperature around 370 K using dilute sulphuric acid as a
catalyst. Due to the low acid concentration and the relatively moderate temperature, the
conversion of cellulose to glucose is negligible in this step. The mixture then enters the
second reactor, which operates at approximately the same temperature but with a higher acid
concentration. In this reactor, the cellulose is converted to glucose and the reaction time is
about 3-6 hours. The material that is not converted in the two reactors is removed and
combusted in order to provide the energy needed to heat the reaction mixture. The energy
consumption for this process is about 5500 kJ/l
produced ethanol
[5]
Referenserna är:
[3] Wayne H Smith , Biomass and energy development, p 551-561, Plenum Press, 1986
[4] Qian Xiang, Y.Y. Lee, Pär O. Pettersson, Robert W. Torget, Heterogenous aspects of acid hydrolysis of α-cellulose. 2003
[5] Wayne H Smith , Biomass and energy development, p 587-600, Plenum Press, 1986
