UvA-DARE (Digital Academic Repository) Converting lignin to aromatics: step by step Strassberger, Z.I. Link to publication Citation for published version (APA): Strassberger, Z. I. (2014). Converting lignin to aromatics: step by step General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (http://dare.uva.nl) Download date: 04 May 2018
Appendix In-house built autoclave and setup for reactions in liquid ammonia
Chapter 6 1.1. Introduction Working with liquid ammonia requires some considerations. First, some basic thermodynamics have to be studied and calculated. Then, a whole set-up including autoclave has to be planned and built. The autoclave should also allow us to study the solubilisation conditions in time. For this purpose, we present here a detailed description of the complete set-up and autoclave. CAUTION! Ammonia vapours have a sharp, irritating, pungent odour that acts as a warning of potentially dangerous exposure. The average odour threshold is 5 ppm, well below any danger or damage. Exposure to high concentrations of gaseous ammonia can result in lung damage and death. The Permissible Exposure Limit (PEL) is 50 ppm. 1.2. Thermodynamic conditions When the reactor is flushed after reaction, ammonia will be released as a gas at 8 bar (autogenous pressure of ammonia in the liquid phase). For this purpose, it is essential to first calculate liquid-to-gas volume expansion as well as the heat exchange over the neutralization step. These calculations are based on the following reaction conditions: 10 ml ammonia, 0.250 g lignin, max. temperature 90 C, max. pressure 90 bar. The conditions are chosen considering the physical properties of ammonia at room temperature: vapour pressure of 8 bars, density of 682 kg/m 3, 0.682 g/ml and molecular weight of 17 g/mol. The number of moles of ammonia used (n = 0.37 mol) was calculated using the formula: ρ = m s /V s n = m s /M w and n = (ρ V s )/Mw where ρ is the density, Mw is the molecular weight, m s is the mass and V s is the volume. The volume of ammonia gas (V = 9 L) was calculated using the ideal gas law PV = nrt 124
Solubilisation of lignin in liquid ammonia The heat energy change in the system was calculated based on eq. 1 and 2: NH 3 (l) + H 2 O(aq) NH 4 OH(aq) (1) NH 4 OH(aq) + HCl(l) NH 4 Cl(s) + H 2 O(aq) (2) with ΔH H2O = -285 KJ/mol ΔH NH4Cl = -314 KJ/mol ΔH HCl = -167 KJ/mol ΔH NH4OH = -81 KJ/mol ΔH r = (ΔH H2O + ΔH NH4Cl ) (ΔH HCl + ΔH NH4OH ) ΔH r = - 351 KJ/mol We need to understand the influence between the volume of the acid bath and the difference in temperature, which will occur during the neutralization process. For this purpose, we calculated the heat energy change defined as follow: Q = n ΔH r and Q = m H2O Cp ΔT where Cp is the heat capacity (at constant pressure), m H2O is the mass of water, Q is the heat energy change and ΔT the difference of temperature. By using this equation, we can plot the influence between the mass of the acid bath used and the difference in temperature as follow: m H2O = (130/4.18) (1/(T 2 -T 1 )) The final temperature of the trapping solution will be between 30-40 C, if working with two times 2 L trap HCl solution of 1M in ice at a temperature of 14 C. 125
Chapter 6 Mass of water! 10! 9! 8! 7! 6! 5! 4! 3! 2! 1! 0! 20! 25! 30! 35! 40! 45! Final temperature ( C)! Fig. 1: Temperature profile of the system. T 1 = 14 C (black) and T 1 = 21 C (gray curve). 1.3. Description of the autoclave and entire set-up A stainless steel autoclave is used for the liquid ammonia experiments. All wetted parts are either made of SS, Teflon or Kalrez. The autoclave is equipped with two windows, situated opposite to each other. The windows are made of boron silicate glass (diameter 30 mm, thickness 15 mm). Due to the glass windows, the system is limited to a maximum pressure of 100 bar. If a higher pressure is needed, sapphire windows can be installed. The heating elements (4x) are mounted in the wall of the lower part of the autoclave. An external temperature controller is connected to the autoclave. The autoclave temperature is controlled by a thermocouple that is attached to the outside of the autoclave. The reaction temperature is measured by a thermocouple mounted in a dip tube that hangs in the liquid of the autoclave. This temperature is also used as a safety shut off. Beside this safety, a Clixon (a temperature switch limited at 250 C) is attached to the outside of the autoclave and to the temperature controller. If this Clixon reaches the max. temperature the autoclave temperature controller is completely switched off. Two valves (Swagelok SS-4PDF4, equipped with a Teflon seat and Kalrez O-rings) are mounted as inlet and outlet valves. A safety relieve valve (Swagelok SS-4R3A, 126
Solubilisation of lignin in liquid ammonia equipped with Kalrez O-rings) is mounted on the lid. Other O-rings (windows and seal) are all of Teflex (from Eriks, The Netherlands). The pressure reading is performed by means of an analog manometer. A magnetic stirrer with a stirring bar coated with glass is used.!! Fig. 2: Photo (Top) and schematic description (bottom) of the reactor set-up for working with liquid ammonia. 127