Enhanced Hydroformylation of Propylene in Propane-Expanded Liquids with Rh-based Complexes
Dupeng Liu, 1, 2 Zhuanzhuan Xie, 2 Raghunath V Chaudhari1, 2 and Bala Subramaniam1, 2
1Department of Chemical & Petroleum Engineering, 2Center for Environmentally Beneficial Catalysis, University of Kansas
Lawrence, KS 66047
Increased shale gas production in the U. S. has increased the availability of C2-C5 alkanes (the so-called natural gas liquids or NGLs) and opportunities for their utilization in novel ways. For example, in a typical propane dehydrogenation process, the per pass conversion is only about 50%.1 The separation of propane and propylene mixtures is highly energy and capital intensive. In this talk, we propose a process that combines propane dehydrogenation and propylene hydroformylation. The unreacted propane from the dehydrogenation section, an inert component during hydroformylation, is used to form a propane-expanded liquid phase to promote regioselective hydroformylation of propylene. In this manner, enrichment of the propane stream is achieved without energy intensive separation. Previously, we had reported on the beneficial effects of carbon dioxide expanded liquids for hydroformylation with Rhodium-based catalyst.2-3 Here we exploit propane-expanded reaction medium for performing propylene hydroformylation with Rhodium-based catalyst. At typical reaction temperatures (70°C for example), it is found that both propane and propylene can volumetrically expand reaction mixtures significantly (by up to two-fold with 15 bar propane or 17 bar propylene). These experimental observations match well with simulation results. It is also shown that H2/CO ratio in the propane-expanded liquid phase (containing propylene and dissolved catalyst complex), a key determinant of the turnover frequency and regioselectivity, can be easily tuned to maximize these performance metrics. For example, the regioselectivity is enhanced by more than threefold in propane-expanded toluene relative to neat toluene as solvent. Systematic investigations of the effects of reaction parameters such as syngas partial pressure, catalyst concentration, ligand mass fraction and propylene pressure on activity and selectivity will be presented, along with preliminary economic analysis.
2. Xie Z, Fang J, Subramaniam B, Maiti SK, Snavely W, Tunge JA. Enhanced hydroformylation by carbon dioxide-expanded media with soluble Rh complexes in nanofiltration membrane reactors. AIChE Journal. 2013;59(11):4287-4296.
3. Fang J, Jana R, Tunge JA, Subramaniam B. Continuous homogeneous hydroformylation with bulky rhodium catalyst complexes retained by nano-filtration membranes. Applied Catalysis A: General. 2011;393(1–2):294-301.
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