Projektierungskurs

Faculty of engineering

Projektierungskurs
WS 2015/16

29. March C 15. April 2016

 

Recycling routes for Triphenylphosphine (TPP)

 

Partner:
Koninklijke DSM N.V.

Coordination:
Dr. Marco Haumann


2016

Groups

 

Gruppe 1 (CRT1): Phosgenherstellung und Phosgenierung

Gruppe 1: Jose Manuel Ramos, Hoonhee Cho, Kyun Ho Han, Patrick Schhle, Birgit Schotterer, Supervisor: Corinna Busse M.Sc.

 

To recycle Triphenylphosphanoxide (TPPO), the intermediate Dichloro(tripheyl)phosphorene (DCP) is produced in a first step by reacting with phosgene in a catalyst free, exothermal reaction (H=-67 KJ/mol).

 

 

 

 

 

 

 

 


To achieve a high rate of phase transition between the gaseous phosgene and the melted TPPO, the reaction is operated in a trickle bed reactor at a temperature 215C and a pressure of 5 bar. The reactor is filled with so called „Pall-rings to increase the contact-surface and the reactants pass the reactor in a counter current flow. The yield of the reaction is 97 %, what leads to a high depletion of phosgene in the exhaust gas.

Phosgene is a highly toxic compound which should be produced and consumed continuously to avoid storage. Therefore, a production process for phosgene out of chlorine and carbon monoxide is installed upstream to the phosgenation. The conversion is catalysed by activated carbon.

 

 

 

 

 

 


In a serial connection of two multitubular reactors a full conversion of chlorine is achieved by adding carbon monoxide in extend (5 mol-%). The first reactor is operated at 300C and 5 bar, enabling a high reaction rate. The second reactor (100C, 5 bar) allows to shift the equilibrium to the product side of the exothermal reaction (H=-107 KJ/mol).

 

Gruppe 2 (CRT2): Hydrierung Flssigphase

Su Zhang, Simon Herlitze, Anja Goblirsch, Johannes Willnauer, Fabian Popp, Supervisor: Rachid Benker M.Sc.

 

Task of Group 2 is the development of a suitable process for recovering Triphenylphosphine (TPP) by hydrogenation of Dichlorotriphenylphosphorane (DCP). The reaction takes place in a trickle-bed reactor at a temperature of 180 C. Molten DCP flows from the top of the reactor to the bottom while Hydrogen (H2) is added at a partial pressure of 100 bar in countercurrent. At the bottom of the reactor the TPP-rich product phase is removed and purified in further steps whereby the formed exhaust-gas consisting of H2 and Hydrogenchloride (HCl) is released at the top. As the reaction is exothermic, the reactor has to be cooled by means of H2.

 

Gruppe 3 (CRT3): Festbettreaktor

Meeson Lee, Nadine Salzmann, Christoph Nboldt, Jessica Wnsch, Timo Rde, Supervisor: Dipl.-Ing. Alexander Seidel

 

Group 3 at the chair of Chemical Reaction Engineering is responsible for designing a concept for the direct catalytic reduction of triphenylphosphine oxide (TPPO) to triphenylphosphane (TPP). This is carried out in two multi-tubular reactors with a fixed catalyst in time-displace cycles. While the reduction is taking place in one reactor the other one is regenerating the catalyst. For the direct reduction of TPPO to TPP the catalyst Bi2O3 is required and the solvent Toluene. For the regeneration a stoichiometric amount of hydrogen is oxidized to water as sole waste gas.

 

Based on a patent, material data and simple assumption we designed the reactor and the process. The reaction is endothermic, the reactants (TPPO + Toluene) must be heated in the gas phase to 500 C in presence of the catalyst and the conversion rate at 2 s residence time of TPPO is 72%. Calculations were made and data like mass flows, enthalpy changes and the pressure drop at the porous catalyst bed were determined. Literature research and reasoning lead to a detailed reactor design and the specific apparatuses needed for this process. To integrate the process into a whole concept we worked closely together with group 6 (separation) and group 7 (heat integration). Our work was also synchronized with group 4 (direct reduction in a fluidized bed reactor) to generate comparable results.

 

Gruppe 4 (LFG): Riser-Regenator Reaktor

Eunyul Choi, Franziska Enzmann, Kilian Dirnberger, Lea Strunz, Supervisor: Sebastian Sß M.Sc.

 

Aim of group 4 is the design of a riser-regenerator-reactor. Desired is a one-step catalytic reduction from TPPO to TPP. The reactor is separated in three parts, riser, downer and regenerator. The riser represents the main reaction area. It is fed with a catalyst-composition (TiO2 and Bi2O3) as well as a vaporized educt-mixture, which consists of 6% TPPO and 94% toluene. To separate the formed product a cyclone is used. The main goal is achieving a continuous operation. This leads to the fact that the catalyst is oxidized as well as regenerated by a reduction during the process.

 

Gruppe 5 (TVT1): Aufreinigung Phosgenroute

Zhenguo Zhang, Heike Pickel, Peter Noll, Andreas Zimmermann, Supervisor: Dr.-Ing. Martin Drescher and Detlef Freitag M.Sc.

 

TPP is formed by reaction of TPPO with phosgene and subsequent hydrogenation. The aim of this group is to achieve the highest purity of TPP after hydrogenation. In addition we have to choose suitable separation processes and calculate the dimensions of the equipment.

After the steps phosgenation and hydrogenation the gaseous parts are removed. By the use of a rotary sprayer the gas phase (CO2, COCl2/ HCl, H2) is separated from the melt and removed by an installed vacuum pump. The sprayer has to be heated to counter the solidification of the melt. The liquid phase contains the product TPP as well as the byproducts DCP, TPPO, which are separated by rectification and recovered to hydrogenation. So the product of the bottom is recycled. To counter the accumulation of TPPO in the reactor a purge stream has to be removed from the recycle stream. For the product (TPP) a purity and content of 99.0 % is required.

It is important to share information with other groups to achieve a successful configuration of the overall process.

 

Gruppe 6 (TVT2): Aufreinigung Reduktionsroute

Changwoo Kim, Bernd Schopf, Fabio Hopf, Arne Stumpf, Supervisor: Dr.-Ing. Martin Drescher and Detlef Freitag M.Sc.

 

Triphenylphosphin (TPP) is formed by catalytic reduction of Triphenylphosphinoxide (TPPO) with hydrogen. Task of the group 6 from the Lehrstuhl fr Thermische Verfahrenstechnik (TVT) is to purify the TPP according to the specifications. The product has to be concentrated to an exact purity. Therefor suitable separation processes and the dimensions of the apparatus are calculated. For the selected separation processes it is necessary to consider the material and energy efficiency.

 

For the catalytic reduction two reactors are used, a fixed bed reactor and a riser regenerator reactor. Both reactors provide a 500 C hot gas mixture. After cooling the mixture down to 200 C, TPP and TPPO are mainly in liquid phase. A flash separates the liquid from the gas phase. The remaining gas mainly consists of toluene and a residual amount of TPP/TPPO.

 

The high amount of solvent has to be purified and is led back to the reactor inlet afterwards.

 

The liquid TPP and TPPO mixture is separated by rectification. For economic reasons, TPPO should be recycled. In order to reach the desired purity, there are several separation steps.

 

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