Performance of Ru/La2O3–ZnO Catalyst for the Selective Hydrogenation of Benzene to Cyclohexene

Abstract

Abstract:Cyclohexene is an important intermediate product for a highly efficient and greener formation of major end products like adipic acid, nylon 6, and nylon 6.6. By using a complex tetra-phase system (g/l/l/s) including hydrogen (g), water (l), an organic phase, i.e., benzene (l), and a supported ruthenium catalyst (s) it is possible to get the desired intermediate cyclohexene based on benzene. We prepared an oxide-supported ruthenium catalyst that was applied together with minimal amounts of the additive NaDCA (sodium dicyanamide) in a batch and continuous apparatus for the selective benzene hydrogenation. We compared these two processes and reached by an optimization of the reaction parameters in continuous process selectivities up to 50% at conversions of 36%. This corresponds to cyclohexene yields of 18% over a period of 100 h. Finally, the catalyst was characterized using X-ray diffraction (XRD), transmission electron spectroscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES), and laser scattering to understand the performance of the catalyst and the effect of the small deactivation.

Selective Hydrogenation of Benzene to Cyclohexene over 2Ru/La2O3‐ZnO Catalyst without Additional Modifiers

“…Based on previous work by our group, we tested the influence of different parameters on the yield of cyclohexene on employing Ru/La 2 O 3 ‐ZnO as the catalyst . The optimization was done by a statistical software DoE (Design of Experiments) under the given reaction conditions (see Table ).…”

“…Based on previous work by our group, we tested the influence of different parameters on the yield of cyclohexeneonemploying Ru/La 2 O 3 -ZnO as the catalyst. [3,8] The optimization was Selectiveb enzene (BEN)h ydrogenation to cyclohexene (CHE) has been studied in ac omplexf our-phase system by using 2Ru/La 2 O 3 -ZnO as the catalyst. The catalyst is highly efficient (yield of desired cyclohexene = 28 %) and stable for about five cycles.…”

“…The formation of cyclohexene based on benzene is a key step in the technical development, because the formation of cyclohexene is thermodynamically not preferred (formation of cyclohexene: −23 kJ mol −1 , formation of cyclohexane: −98 kJ mol −1 ). Therefore, formation of cyclohexene in high yields requires a complex four‐phase system (g/l/l/s), consisting of hydrogen (g), an organic (l) and an aqueous phase (l), and a solid Ru catalyst (s) . In 1989, Asahi Chemical Industry Co., Ltd., developed a process for the selective benzene hydrogenation by using a Ru–Zn catalyst .…”

“…Therefore, formation of cyclohexene in high yields requires ac omplexf our-phase system (g/l/l/s), consisting of hydrogen (g),a no rganic (l) and an aqueous phase (l), and as olid Ru catalyst( s). [3] In 1989, Asahi Chemical Industry Co.,L td.,d eveloped ap rocess for the selective benzene hydrogenation by using aR u-Zn catalyst. [4] The disadvantages of this process are the high amount of ruthenium necessary,t he use of ZrO 2 as ad ispersant, and the presence of an aqueous solution of ZnSO 4 .Z nSO 4 acts as am odifier and adsorbs on the catalysts urface, achieving am ore hydrophilic surfaces tructure.…”

Hydration of Cyclohexene into Cyclohexanol using H‐ZSM5 as Catalyst

“…Unter Verwendung geeigneter Katalysatoren (H‐ZSM5‐Zeolithe) können sehr hohe Selektivitäten (> 99 %) zum gewünschten Cyclohexanol erreicht werden. Der erste Prozessschritt (die selektive Benzolhydrierung) konnte bereits durch unsere Arbeitsgruppe unter Verwendung von Ru/La 2 O 3 ‐ZnO im kontinuierlichen Labormaßstab erfolgreich umgesetzt werden .…”