Javier Ereña

Thermal recycling of polystyrene and polystyrene-butadiene dissolved in a light cycle oil

A study has been made of the cracking on a mesoporous silica of polystyrene (PS) and polystyrene-butadiene (PS-BD) dissolved in a light cycle oil (LCO) from a product stream of a commercial fluid catalytic cracking (FCC) unit. This study has been carried out in a reactor of short contact time (3 s) in the 723–823 K range. This strategy for simultaneous valorization of plastics and solvent avoids the technological problems inherent to the treatment of solid postconsumer-plastics and the limitation to heat transfer in the process of pyrolysis. The cracking of plastics has a synergistic effect on the conversion of LCO, as it contributes to increasing the yield of gasoline (C5–C12). The cracking of the PS/LCO blend produces high yields of styrene, whereas the cracking of the PS-BD/LCO blend produces a stream of products with petrochemical interest.

Direct Synthesis of Dimethyl Ether From (H2+CO) and (H2+CO2) Feeds. Effect of Feed Composition

The effects of feed composition on the conversion of CO and CO2, selectivity to DME, yield of DME and product distribution are studied in the synthesis of DME from syngas and from (H2+CO2) in a single reaction step using the bifunctional catalysts CuO-ZnO-Al2O3/gamma-Al2O3 and CuO-ZnO-Al2O3/NaHZSM-5. For feeds made up of H2 and CO, the maximum conversion levels of CO, yield of DME and selectivity to DME obtained with both catalysts are very similar, close to 95 %, 75 % and 80 %, respectively, although the catalyst CuO-ZnO-Al2O3/gamma-Al2O3 requires a higher H2/CO ratio. For the feeds made up of H2 and CO2, the catalyst based on NaHZSM-5 zeolite (moderately acid function) performs better due to the fact that higher water content in the reaction medium leads to its adsorption on the Lewis acid sites of gamma-Al2O3 and limits the transformation capacity of methanol to DME.

Conversion of syngas to liquid hydrocarbons over a two-component (Cr2O3-ZnO and ZSM-5 zeolite) catalyst : Kinetic modelling and catalyst deactivation

Abstract The present study describes the kinetics of syngas transformation into liquid hydrocarbons (boiling point in the gasoline range) using as catalyst a mixture of a metallic component, Cr 2 O 3 –ZnO, and of an acidic component, ZSM-5 zeolite. Experimental results were obtained in an isothermal fixed-bed integral reactor. The validity of several kinetic models, available for methanol synthesis, is analysed and modifications are proposed. These changes involve a rate equation with a CO 2 concentration-dependent term. Catalyst deactivation is also evaluated and the effect of the operating conditions on coke deposition is established. Moreover, the rate of CO conversion and the change of catalytic activity with time-on-stream were described using a kinetic model showing a weak influence of temperature.

Effect of the operating conditions on the conversion of syngas into liquid hydrocarbons over a Cr2O3–ZnO/ZSM5 bifunctional catalyst

The effect of the operating conditions (pressure, temperature, space time, CO/H2 ratio in the feed and time on stream) on the conversion of syngas into liquid hydrocarbons over a Cr2O3–ZnO/ZSM5 bifunctional catalyst has been studied by means of experimentation in an integral fixed bed reactor. On the basis of the results, the global stoichiometry of the process is established and the relative importance of the operating variables in order to reach a good compromise between catalyst activity and gasoline quality is analysed.

Valorization by thermal cracking over silica of polyolefins dissolved in LCO

A study has been made of the cracking of polyethylene (PE) and polypropylene (PP) (which are the main components of post-consumer plastic wastes) dissolved in the Light Cycle Oil (LCO) product stream of a commercial Fluid Catalytic Cracking (FCC) unit. The cracking has been carried out on a mesoporous silica (pore size between 3 and 30 nm) in the 723–823 K range. This strategy for upgrading plastics and solvents together avoids heat transfer limitations and other problems inherent to the cracking of solid plastics. The polyolefins are transformed mainly into the components that make up the pool of gasoline (C5–C12). Furthermore, the incorporation of polyolefins has a synergistic effect on the cracking of LCO and causes a major decrease in the content of aromatics of the pool of gasoline and an increase in the content of olefins, paraffins and i-paraffins.

Study of the regeneration stage of the MTG process in a pseudoadiabatic fixed bed reactor

Abstract The regeneration stage of a catalyst (prepared based on an HZSM-5 zeolite) has been studied in the process of transformation of methanol into hydrocarbons in a fixed bed reactor. The simulation of the operation requires knowledge of the longitudinal profile of coke content in the reactor at the end of the reaction stage. Longitudinal profiles of temperature, coke content and activity during the regeneration are calculated by solving the energy conservation equation in the reactor together with the kinetic equation for coke combustion and with the kinetic equation for reactivation (activity–coke content relationship). The results of the simulation have been experimentally verified in a laboratory unit provided with a pseudoadiabatic fixed bed reactor.

Valorization of Polyolefin/LCO Blend over HZSM-5 Zeolites

The cracking of low density polyethylene (PE) and of polypropylene (PP) dissolved in LCO (light cycle oil, product of a commercial FCC unit) is studied in the 450-550 ºC range, by using a reactor simulating a FCC riser. The reaction was carried out on catalysts prepared based on HZSM-5 zeolites with different Si/Al ratio The results are explained by the shape selectivity of the HZSM-5 zeolite and by the total acidity, which decreases as the Si/Al ratio of the zeolite is increased. A feed with polyolefin content higher than 5 wt% limits the conversion of LCO. The cracking on HZSM-5 zeolite catalysts of PE/LCO and PP/LCO blends produces a yield of C5-C12 fraction, which is highly aromatic and with a high content of styrene, and a low yield of C1 and C2 gases and of coke. A feed made up of polyolefins and LCO contributes to increasing the yield of light olefins, of which the concentration of ethylene increases with temperature. When compared to the coke selectivity of LCO cracking, a feed with PP contributes to increasing it, whereas PE decreases it.

Composition and quality of the gasoline obtained from syngas on Cr2O3-ZnO/ZSM5 catalysts

Abstract The kinetic equations for the formation of the lumps of the gasoline produced (C5 + fraction), paraffins (C5-C8), xylenes (o-xylene, m-xylene and p-xylene) and aromatics (benzene, toluene, C9-C11) in the transformation of syngas on Cr2O3-ZnO/ZSM5 bifunctional catalyst have been established as a function of the concentration of both reactants (CO and H2) and CO2 byproduct. The effect of the operating conditions on the RON and on the molecular weight of the gasoline has been studied by experimentation in an integral fixed bed reactor in the range between 10 and 50atm and between 300 and 425°C. The octane index increases with Cr/Zn atomic ratio of the Cr2O3-ZnO metallic function, with Si/Al ratio of the HZSM5 zeolite, with space time and with the CO/H2 molar ratio in the feed, in that order, whereas it passes through a maximum with pressure (at 20 atm) and with temperature (at 375°C). On the other hand, the molecular weight of the gasoline increases with the Cr/Zn atomic ratio, pressure, CO/H2 molar...