Udo Armbruster

Hydrodeoxygenation of Phenol as a Model Compound for Bio‐oil on Non‐noble Bimetallic Nickel‐based Catalysts

Ni/HZSM‐5 catalysts for the hydrodeoxygenation of bio‐oil were modified with Cu and Co. A first test series with phenol as a model revealed that the presence of Ni is essential for high activity. However, modification with Cu deteriorated the catalytic performance significantly whereas an admixture of Co increased the activity and selectivity toward the target hydrocarbons benzene and cyclohexane. Characterization studies performed by using TEM, X‐ray photoelectron spectroscopy, and XRD techniques elucidated detrimental effects of the second metals: both Cu and Co form alloys with Ni; however, Cu caused a loss of active sites as well as tended to segregate at the surface whereas Co made the particles smaller and strongly stabilized the active Ni sites, that is, Ni dispersion increased. A NiCo/HZSM‐5 catalyst (10 wt % of each metal content) showed 99 % hydrocarbon selectivity at complete phenol conversion. Additional studies using intermediate products such as benzene, cyclohexene, and C6 oxygenates as feeds highlight the effect of the catalyst composition on key reaction steps.

Partial oxidation of propane in sub- and supercritical water

Abstract The potential of sub- and supercritical water as reaction medium for the partial oxidation of propane to oxygen-functionalised hydrocarbons (oxygenates) was studied at temperatures from 633 to 693 K and pressures from 16.7 to 28 MPa in batch and continuous runs with synthetic air as oxidant. Additional experiments with heterogeneous catalysts (Carulite 300®, MnO2, Co2O3, MnO2–Co2O3, MoO3, all supported on γ-alumina) provided information about behaviour of oxidic materials at hydrothermal conditions. The properties of fresh and spent catalysts were characterised by several standard methods (BET, ICP, XRD, SEM, XPS). The influence of reaction parameters like temperature, pressure, density, residence time, and feed composition on conversion and selectivities was examined. Transition of reaction mixture from sub- to supercritical region shows significant influence on propane and oxygen conversion rates, due to homogenisation of reaction mixture and improved mass transfer. Influence of catalyst materials is comparatively small. Total sum of oxygenates selectivities reached 15% at 90% propane conversion and methanol was the mainly formed oxygenate.

Structural transformation of an alumina-supported MnO2–CuO oxidation catalyst by hydrothermal impact of sub- and supercritical water

The structural transformation of a MnO2–CuO-containing catalyst supported on X-ray amorphous Al2O3 used in oxidative conversion of ethyl acetate in water under sub-critical (p = 200 bar, T = 633 K) and supercritical reaction conditions (p = 240 bar, T = 673 K) has been studied by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). TEM investigations revealed very small primary crystallites of the parent sample (ca. 5–20 nm), in contrast to a catalyst specimen exposed to supercritical water for ca. 100–200 hours which exhibited large micron-sized crystallites. This crystallisation process is accompanied by a drastic decline in the catalyst BET surface area. XRD studies support this observation: the basic material is nearly X-ray amorphous whereas the used catalyst shows several crystalline phases (e.g. Mn2O3, Al2O3, AlO(OH)). The patterns of spent catalysts taken from the reactor after different running times also gave evidence for the existence of mixed manganese copper oxides. Furthermore, XRD analysis of the used catalysts revealed a reduction of the basic MnO2 to Mn3O4 and Mn2O3; this was also clearly proven by XPS analysis. Hydrolysis runs at supercritical water oxidation conditions showed that ethyl acetate is only hydrolysed into ethanol and acetic acid but, in contrast to these non-catalysed runs, the further oxidation of the hydrolysis products to carbon dioxide and water occurs in the presence of the oxidation catalyst. It may be stated that during time-on-stream up to ca. 200 h neither activity nor selectivity was found to significantly change, apart from the found structural alterations.

High-Temperature Synthesis of Ordered Mesoporous Aluminosilicates from ZSM-5 Nanoseeds with Improved Acidic Properties

Ordered mesoporous SBA-15 analogs with different Si/Al ratios were successfully prepared in a two-step process from self-assembly of ZSM-5 nanoseeds at high temperature in mildly acidic media (473 K, pH 3.5). The obtained products were characterized as SAXS, XRD, N2 sorption, FTIR, TEM, NH3-TPD, AAS and ICP. The results show that the initial Si/Al molar ratio of ZSM-5 precursors strongly affects the final materials’ properties. A highly condensed, well-ordered mesoporous SBA-15 analog with improved hydrothermal stability and acidic properties can be prepared from low aluminum containing ZSM-5 precursors (Si/Al ≥ 20). Reducing the initial Si/Al molar ratio to 10, however, leads to the formation of a disordered mesoporous SBA-15 type material accompanied by degraded textural and acidic properties. The gas phase cracking of cumene, carried out as probe reaction to evaluate Brønsted acidity, reveals that an increased density of Brønsted acid sites has been achieved over the SBA-15 analogs compared to conventional Al-SBA-15 due to the preservation of zeolite building units in the mesopore walls of the SBA-15 analogs.

Upgrading of bio-oil and subsequent co-processing under FCC conditions for fuel production

Hydrodeoxygenation of fast pyrolysis oil was first investigated on bimetallic catalysts (homogeneous Ni–Co alloy) supported on various carriers (HZSM-5, HBeta, HY and ZrO2). The bimetallic catalyst 10Ni10Co/HZSM-5 outperformed the corresponding monometallic catalysts and Ni–Co supported on other support materials (HBeta, HY and ZrO2) with 39% deoxygenation degree and 37 wt% (wet basis) oil yield. 13C-NMR spectroscopy, GC, GC-MS, and elemental analysis revealed that the chemical composition of the product changed significantly and the higher heating value increased substantially from 23.6 to 33.3 MJ kg−1. The upgraded bio-oil was subsequently co-fed with a conventional feed (atmospheric distillation residue) using a commercial micro activity test setup under FCC conditions with an equilibrated commercial refinery catalyst to demonstrate a possible route for production of fuel from biomass. These tests showed similar conversion for both the conventional and co-processed feeds, whereas the latter case revealed a reduction of heavy cycle oil and a slight increase of gasoline, gas and light cycle oil yields.