Light olefins dimerization to high quality gasoline components

New attractive technologies can be designed in the field of light olefins dimerization (C₃–C₅) in order to obtain products useful as gasoline blending components; the technologies are characterized both by low investment costs and by high product quality. Isobutene dimerization is a powerful alternative to MTBE production whenever the use of the latter will be forbidden in gasoline. Also the dimerization of iso-amylenes and propylene, when properly designed, can give products (both the olefins and the corresponding hydrogenated derivatives) characterized by very high octane numbers. More in general all these technologies can help to debottleneck the FCC downstream when enhanced olefins production is achieved by means of new FCC catalysts and processes.     

Supported Rh catalysts for the indirect partial oxidation of isooctane

The production of hydrogen from isooctane over three rhodium-based catalysts has been examined. The reaction entailed total oxidation of a proportion of the fuel followed by reforming of isooctane to produce hydrogen. Rhodium (1% wt) was impregnated on three different supports: alumina, ceria-alumina, and ceria-zirconia. No differences in catalytic activity were observed, but reaction yield changed with the support. Ceria-zirconia was found to be the preferred support since methanation did not occur over the catalyst.     

Homogeneous charge compression ignition of binary fuel blends

The present experimental investigation aims to understand the homogeneous combustion chemistry associated with binary blends of three surrogate components for practical fuels, including toluene, isooctane, and diisobutylene-1 (DIB-1). Specifically, high-pressure autoignition characteristics of the three neat fuel components as well as the fuel blends of toluene + isooctane and toluene + DIB-1 are studied herein. Experiments are conducted in a rapid compression machine at compressed pressures varying from 15 to 45 bar and under low to intermediate temperatures. To obtain insights into interactions among fuels, the relative proportion of the two neat fuels in the reactive mixtures is systematically varied, while the total fuel mole fraction and equivalence ratio are kept constant. Experimental results demonstrate that ignition delays for neat toluene are more than an order of magnitude longer than those for neat isooctane. Whereas DIB-1 has ignition delays shorter than those for isooctane at higher temperatures, at temperatures lower than 820 K DIB-1 shows a longer ignition delay. Although the ignition delays of binary blends lie in between the two extremes of neat components, the variation of ignition delay with the relative fuel proportion is seen to be highly nonlinear. Especially, a small addition of isooctane or DIB-1 to toluene can result in greatly enhanced reactivity. In addition, the effect of DIB-1 addition to toluene is more significant than the effect of isooctane addition. Furthermore, in the compressed temperature range from 820 to 880 K, ignition delay of the toluene + isooctane blend shows greater sensitivity to temperature than that of isooctane.     

Rh- and Rh–Ni–MgO-based structured catalysts for on-board syngas production via gasoline processing

Rh/Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl and Rh/Ni–MgO/Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl FeCrAlloy wire mesh supported catalysts were prepared via multistep procedure. They were characterized by XRD, SEM and TEM techniques. A comparative study of autothermal reforming (ATR) of isooctane and simulated gasoline (blends of isooctane, ortho-xylene and naphthalene) over Rh/Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl and Rh/Ni–MgO/Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl was performed. Both catalysts showed excellent performance in ATR of isooctane at molar ratios of O₂:C = 0.51 and H₂O:C = 2.59, T = 750°С and GHSV = 10000 h⁻¹. In the ATR of isooctane – o-xylene blend in presence of Rh–Ni-containing catalyst carbon formation was observed. Rh-containing catalyst demonstrated rather good activity and stability even in the case of isooctane – o-xylene – naphthalene blend.     

Excess molar enthalpies for the binary and ternary mixtures of ether compounds (di-isopropyl ether, di-butyl ether, propyl vinyl ether) with ethanol and isooctane at 298.15 K

Excess molar enthalpy (H ^E ) data at 298.15 K are reported for the binary systems di-isopropyl ether (1)+ethanol (2), di-isopropyl ether (1)+isooctane (2), ethanol (1)+isooctane (2), di-butyl ether (1)+ethanol (2), di-butyl ether (1)+isooctane (2), propyl vinyl ether (1)+ethanol (2) and propyl vinyl ether (1)+isooctane (2). These data were obtained by using an isothermal flow calorimeter. The experimental binary H ^E data were well correlated with the Redlich-Kister model, and infinitely dilute partial excess molar enthalpies for each binary were calculated with the fitted Redlich-Kister parameters. Additionally, the isoclines of H ^E for ternary systems di-isopropyl ether (1)+ethanol (2)+isooctane (3), di-butyl ether (1)+ethanol (2)+isooctane (3) and propyl vinyl ether (1)+ethanol (2)+isooctane (3) at 298.15 K were calculated by using the Radojkovič equation. H ^E for all the measured systems in this work shows that mixing is endothermic.     

Study of the performance of Mo2C for iso-octane steam reforming

In the present work, the performance of commercial molybdenum carbide (Mo₂C) for isooctane steam reforming has been investigated in order to determine the effects of major operating parameters (temperature, space velocity, and steam to carbon ratio) on the catalytic activity. While the results obtained indicate an onset reforming temperature of 850 °C, high concentrations of H₂ in the reforming environment were found to reduce the onset temperature to 750 °C. The catalytic activity at 850 °C was sufficient to produce hydrogen yields greater than 90% and carbon conversions close to 100%, with a low selectivity to CH₄ and CO₂. In addition, and consistent with thermodynamic predictions, a steam to carbon ratio of 1 appeared to optimize the reforming rates. Finally, based on experimental observations, a reaction mechanism was formulated and used to interpret the results obtained during catalytic activity measurements. This mechanism involves continuous oxidation and reduction of Mo metal, which can provide activity and stability to the catalyst when occurring at similar rates.     

Thermoneutral Design Aspects of Gasoline Chemical Looping Reformer

Chemical looping reforming (CLR) is a new technology for syngas generation. The theoretical process design aspects of syngas generation using CLR of isooctane (gasoline) are studied in this paper to assess its ability for fuel processor development for solid oxide fuel cells. The fuel processor operating conditions for maximum syngas generation at thermoneutral conditions are determined in this study using nickel oxide as oxygen carrier for different inputs of oxygen carrier within the temperature range of 600–1,000 °C at 1 bar pressure. The thermoneutral temperatures for the dual reactor fuel processor were calculated using the hot product gas stream and exothermic CLR process enthalpy to completely balance the endothermic process requirements. The thermoneutral point of 879.5 °C (NiO input of 7 moles) delivered maximum syngas (13.92 moles) using lowest amount of air (26.13 moles) in the process was found to be the most suitable thermoneutral temperature for the fuel processor operation. The novel fuel processor design can also be used for other fuels and oxygen carriers.     

NiMo-calcium-doped ceria catalysts for inert-substrate-supported tubular solid oxide fuel cells running on isooctane

A calcium-doped ceria (Ce_1-xCa_xO_2−δ, 0 ≤ x ≤ 0.3) has been applied as a ceramic support in NiMo-based catalysts for an internal reforming tubular solid oxide fuel cell running on isooctane. Introducing calcium into the CeO₂-based ceramic was found to improve conductivity of Ce_1-xCa_xO_2−δ. The Ce_0.9Ca_0.1O_2−δ (x = 0.10) sample exhibited an optimum conductivity of 0.045 S cm⁻¹ at 750 °C. The transport of oxygen ions in Ce_1-xCa_xO_2−δ promoted the catalytic partial oxidation of isooctane in the NiMo–Ce_1-xCa_xO_2−δ catalyst, which increased the fuel conversion as well as H₂ and CO yields. As a result, the NiMo–Ce_0.9Ca_0.1O_2−δ (x = 0.10) catalyst exhibited a high isooctane conversion of 98%, and the H₂ and CO yields achieved 74% and 83%, respectively, for reforming of isooctane and air at the O/C ratio of 1.0 at 750 °C. Furthermore, the NiMo–Ce_0.9Ca_0.1O_2−δ catalyst has been applied as an internal reforming layer for an inert-substrate-supported tubular solid oxide fuel cell running on isooctane/air. Due to its high reforming activity, the single cell presented an initial maximum power density of 355 mW cm⁻² in isooctane/air at 750 °C and displayed stable electrochemical performance during ~30 h operation. These results demonstrated the application feasibility of the NiMo–Ce_0.9Ca_0.1O_2−δ catalyst for direct internal reforming solid oxide fuel cells running on isooctane/air.     

Formation of oxygenated compounds from isooctane flames

The formation of three families of oxygenated compounds is studied in the case of isooctane combustion. Stoichiometric, lean and rich conditions are studied at different distances from a flat burner. Nine carbonyl compounds, five alcohols and three organic acids are found in detectable concentrations in the combustion products. These oxygenated compounds are formed very quickly, their concentrations increase or remain constant for about 2-3 mm and then they fall to zero. Generally, in accordance with the results of a spark ignition engine, the oxygenated compounds have a maximum concentration at stoichiometry or under lean conditions. Some combustion products are well correlated, indicating that they are formed in parallel, or one is the precursor of the other.     

Effect of crevice mass transfer in a rapid compression machine

Rapid Compression Machines (RCMs) often employ creviced pistons to suppress the formation of the roll-up vortex. However, the use of a creviced piston promotes mass transfer into the crevice when heat release takes place in the main combustion chamber. This multi-dimensional effect is not accounted for in the prevalent volumetric expansion approach for modeling RCMs. The method of crevice containment avoids post-compression mass transfer into the crevice. In order to assess the effect of the crevice mass transfer on ignition in a RCM, experiments are conducted for autoignition of isooctane in a RCM with creviced piston in the temperature range of 680–940 K and at compressed pressures of ∼15.5 and 20.5 bar in two ways. In one situation, post-compression mass transfer to the crevice is avoided by crevice containment and in other it is allowed. Experiments show that the crevice mass transfer can lead to significantly longer ignition delays. Experimental data from both scenarios is modeled using adiabatic volumetric expansion approach and an available kinetic mechanism. The simulated results show less pronounced effect of crevice mass transfer on ignition delay and highlight the deficiency of the volumetric expansion method owing to its inability to describe coupled physico-chemical processes in the presence of heat release. Results indicate that it is important to include crevice mass transfer in the physical model for improved modeling of experimental data from RCMs without crevice containment for consistent interpretation of chemical kinetics. The use of crevice containment, however, avoids the issue of mass transfer altogether and offers an alternative and sound approach.