Andreas Jess

Deep desulfurization of oil refinery streams by extraction with ionic liquids

Extraction of S- and N-compounds from gasoline and diesel oil by ionic liquids (ILs) indicates that such a process could be an alternative to common hydrodesulfurization (HDS) for deep desulfurization down to values of 10 ppm S or even lower. The results show the selective extraction properties of ILs, especially with regard to those S-compounds which are hard to remove by HDS, e.g. dibenzothiophene derivatives present in middle distillates like diesel oil. The application of mild process conditions (ambient pressure and temperature) and the fact that no hydrogen is needed, are additional advantages compared to HDS. Very promising ILs are [BMIM][OcSO4] and [EMIM][EtSO4], as they are halogen-free and available from relatively cheap starting materials. Extraction with ILs is not limited to diesel oil, but probably even more attractive for FCC-gasoline. Although HDS of S-species present in this gasoline constituent – mainly thiophenes – is relatively straightforward, a major drawback is the loss in octane number by olefin saturation, which favours extraction with ILs.

Mechanisms and kinetics of thermal reactions of aromatic hydrocarbons from pyrolysis of solid fuels

Abstract The kinetics of the thermal conversion of aromatic hydrocarbons in the presence of hydrogen and steam were studied, using anphthalene, toluene and benzene as model compounds. The experiments were performed in a tubular flow reactor at a total pressure of 160 KPa, temperatures of 700–1400°C, residence times of 0.3–2 s and different gas-phase concentrations of hydrogen, steam and the aromatics. The mechanisms of primary and consecutive reactions are presented as reaction schemes that are supported by kinetic calculations. The following order of reactivity is obtained: toluene ⪢ naphthalene > benzene. Besides gaseous organic cracking products such as methane and ethene, condensed products and a carbonaceous residue (soot) is formed, principally from naphthalene. Soot formation is strongly inhibited by hydrogen. Steam has only a little influence on the conversion of the aromatics. Under the given reaction conditions, neither the soot primarily formed nor the organic cracking products such as methane are completely converted by steam to carbon monoxide and hydrogen, even at the highest temperature investigated (1400°C).

Deep desulfurization of diesel fuel by extraction with ionic liquids

A new approach for the deep desulfurization of diesel fuels by extraction with ionic liquids is described.

Analysis of evaporation and thermal decomposition of ionic liquids by thermogravimetrical analysis at ambient pressure and high vacuum

Ionic liquids (ILs) are widely discussed as alternative green solvents not only because of their unique chemical properties, but also because of their extremely low vapour pressure and – at least in some cases – relatively high thermal stability. Two complementary methods are analyzed and compared to determine both the rate constant of decomposition and the vapour pressure of four ILs: (1) thermogravimetrical analysis at ambient pressure (TGap) with an overflow of inert gases, and (2) high vacuum (HV) experiments with a magnetic suspension balance (MSB). At ambient pressure, [EMIM][MeSO3] and [EMIM][CF3SO3] decompose without a significant contribution of evaporation, which leads to the rate constant of thermal degradation. For both ILs, the vapour pressure can only be determined at HV by the MSB, because the evaporation rate is then higher than the decomposition rate. For the relatively volatile ILs [EMIM][NTf2] and [BMIM][NTf2] the vapour pressure can be derived both by the MSB at HV as well as by TGap. General strategies to determine the volatility and stability of ILs and criteria for the maximum operation temperature with regard to decomposition and evaporation are presented.

De Novo Design of Nanostructured Iron–Cobalt Fischer–Tropsch Catalysts

Audio cassettes hold the key to enhancing Fischer–Tropsch catalysis. Catalysts based on ultra‐thin cobalt shells surrounding cheap iron oxide cores (see picture) are developed, an approach previously optimized for preparing magnetic tape for audio cassettes. These particles are easily made on a large scale, and are excellent Fischer–Tropsch catalysts, giving good diesel fractions.

Desulfurization of diesel oil by selective oxidation and extraction of sulfur compounds by ionic liquids—a contribution to a competitive process design

Extraction of S-compounds like dibenzothiophenes from diesel oil by ionic liquids (ILs) indicate that such a process could be an attractive alternative to common (deep) desulfurization by hydrotreating. The efficiency of the extraction increases if the S-species are previously oxidized to the corresponding sulfoxides and sulfones as these species have a much higher distribution coefficient compared to the non-oxidized derivatives. The present work combines the extraction of oxidized S-compounds from diesel oil by ILs and the subsequent IL regeneration, i.e. the removal of the oxidized S-species from the S-loaded IL by means of water addition which leads to a displacement of the S-compounds from the IL. Thus, water separation by evaporation is needed before the IL can be re-used for extraction. Model oils containing single sulfones as well as real pre-oxidized diesel oils were investigated. Based on the experimental results the energy consumption of the extractive desulfurization process was estimated. The evaporation of water from the IL is the crucial step with regards to the energy consumption of the process. The energy demand is comparable to classical hydrotreating, if a multi-stage evaporation is used.

Catalytic upgrading of tarry fuel gases : A kinetic study with model components

Abstract As a contribution to the development of a process for catalytic upgrading of tarry fuel gases, e.g. coke-oven gas, the conversion of naphthalene, benzene and methane on a nickel catalyst in the presence of H 2 and H 2 O was studied. The experiments were performed in a tubular flow reactor (total pressure: 1.6 bar; residence time with respect to the empty reactor: 0.3 s; temperature: 400–950°C; and particle diameter of catalyst: 1.5 mm). The kinetic data were obtained by systematic variation of the reaction conditions. At temperatures of more than 800°C, each hydrocarbon is cracked and converted with H 2 O to CO and H 2 . Soot formation does not occur at any temperature. In case of simultaneous conversion of all three hydrocarbons, competitive reactions have to be considered. The rate of chemical reaction on the catalyst is substantially decreased in the presence of H 2 S. Nevertheless, in a reactor of industrial scale, H 2 S has only slight influence. The catalyst would be applied with a particle diameter of 19 mm (experiments: 1.5 mm), and the overall reaction rate of hydrocarbon conversion is significantly affected by gas film diffusion.

Ionic liquids in refinery desulfurization: comparison between biphasic and supported ionic liquid phase suspension processes.

The desulfurization of fuel compounds in the presence of ionic liquids is reported. For this purpose, the desulfurization efficiency of a variety of imidazolium phosphate ionic liquids has been tested. Dibenzothiophene/dodecane and butylmercaptan/decane mixtures were used as model systems. Single-stage extractions reduced the sulfur content from 500 ppm to 200 ppm. In multistage extractions the sulfur content could be lowered to less than 10 ppm within seven stages. Regeneration of the ionic liquid was achieved by distillation or re-extraction procedures. Supported ionic liquid phase (SILP) materials, obtained by dispersing the ionic liquid as a thin film on highly porous silica, exhibited a significantly higher extraction performance owing to their larger surface areas, reducing the sulfur content to less than 100 ppm in one stage. Multistage extraction with these SILP materials reduced the sulfur level to 50 ppm in the second stage. The SILP technology offers very efficient utilization of ionic liquids and circumvents mass transport limitations because of the small film thickness and large surface area, and allows application of the simple packed-bed column extraction technique.

Deactivation and regeneration of a naphtha reforming catalyst

Abstract A series of naphtha reforming catalysts from different stages of the deactivation (coking) and the regeneration (decoking) processes were investigated by NMR and chemical engineering methods. The dependence of the tortuosity on the coke content was determined for both processes by NMR measurements of the intraparticle self-diffusion coefficients of adsorbed liquid n -heptane. The shrinkage of the accessible pore volume as a function of increasing coke content due to the deactivation process is compared to nitrogen adsorption (BET) measurements which show an equivalent behavior. A crude model was adapted to predict qualitatively the relationship between the tortuosity and the average pore diameter. Longitudinal ( T 1 ) and transverse ( T 2 ) NMR relaxation times measured for protons of adsorbed liquid n -heptane, provide information on the pore morphology changes which can be corroborated by the tortuosity measurements. The chemical composition of the coke layer, which was investigated by 1 H magic angle spinning (MAS) and 13 C cross polarization (CP)/MAS NMR spectroscopy, is shown to change during both deactivation and decoking processes. Moreover, the micro-structure of the fresh catalyst and the fully regenerated catalyst was investigated by scanning electron microscopy (SEM). The experimental results indicate that a full recovery of the activity of the clean catalyst is not achieved by the regeneration process, and that the quality of regeneration depends on the coke content reached during the deactivation/regeneration cycle.

Alkylation of isobutane with 2-butene using ionic liquids as catalyst

Alkylation of isobutane with 2-butene was performed in a batch reactor using the ionic liquid 1-n-octyl-3-methylimidazolium bromide aluminium chloride ([OMIM]Br-AlCl3) pure, and in a mixture with compounds containing SO3H-groups. The acidity of the ionic liquid (IL) was modified by the addition of acid cation exchange resins (dry or with a small amount of water), or by the addition of a second IL ([(HO3SBu)MIM]HSO4). A high content of the desired trimethylpentanes (up to 64%) and thus a high research octane number (RON up to 96) of the alkylate was obtained. The reusability of the IL systems was studied and compared with a catalyst commercially used at present (H2SO4).