Effect of Steam Deactivation Severity of ZSM-5 Additives on LPG Olefins Production in the FCC Process

ZSM-5-containing catalytic additives are widely used in oil refineries to boost light olefin production and improve gasoline octanes in the Fluid Catalytic Cracking (FCC) process. Under the hydrothermal conditions present in the FCC regenerator (typically >700 °C and >8% steam), FCC catalysts and additives are subject to deactivation. Zeolites (e.g., Rare Earth USY in the base catalyst and ZSM-5 in Olefins boosting additives) are prone to dealumination and partial structural collapse, thereby losing activity, micropore surface area, and undergoing changes in selectivity. Fresh catalyst and additives are added at appropriate respective levels to the FCC unit on a daily basis to maintain overall targeted steady-state (equilibrated) activity and selectivity. To mimic this process under accelerated laboratory conditions, a commercial P/ZSM-5 additive was hydrothermally equilibrated via a steaming process at two temperatures: 788 °C and 815 °C to simulate moderate and more severe equilibration industrial conditions, respectively. n-Dodecane was used as probe molecule and feed for micro-activity cracking testing at 560 °C to determine the activity and product selectivity of fresh and equilibrated P-doped ZSM-5 additives. The fresh/calcined P/ZSM-5 additive was very active in C12 cracking while steaming limited its activity, i.e., at catalyst-to-feed (C/F) ratio of 1, about 70% and 30% conversion was obtained with the fresh and steamed additives, respectively. A greater activity drop was observed upon increasing the hydrothermal deactivation severity due to gradual decrease of total acidity and microporosity of the additives. However, this change in severity did not result in any selectivity changes for the LPG (liquefied petroleum gas) olefins as the nature (Brønsted-to-Lewis ratio) of the acid/active sites was not significantly altered upon steaming. Steam deactivation of ZSM-5 had also no significant effect on aromatics formation which was enhanced at higher conversion levels. Coke remained low with both fresh and steam-deactivated P/ZSM-5 additives

Erratum: Effect of alkali (Cs) doping on the surface chemistry and CO2hydrogenation performance of CuO/CeO2catalysts [Journal of CO2 Utilization (2021) 44 (101408) DOI: 10.1016/j.jcou.2020.101408)

The publisher regrets that the printed version of the above article contained a number of typo errors inserted during proofing process. The publisher would like to apologise for any inconvenience caused. In particular: • The units throughout the text must be in the form A/B instead of A/ B-1, i.e., cm3/min, °C/min, μmol/g, gcat/m3, mol/m3, m2/s instead of cm3/min-1, °C/min-1, μmol/g-1, gcat/m-3, mol/m-3, m2/s-1, respectively. • In the definition of turnover frequency (Eq. (6)) the term B must be defined as the total CO2uptake in μmol/g, i.e. "⋯derived by the total CO2uptake in μmol/g (B) calculated by CO2-TPD measurements" instead of "⋯derived by the total CO2uptake in 40 μmol/g (B) calculated by CO2-TPD measurements". • The y-axis in Figure 7 must be dimensionless, i.e., ln(TOF) instead of ln(TOF) (s-1).publishersversionpublishe

Effect of alkali (Cs) doping on the surface chemistry and CO2 hydrogenation performance of CuO/CeO2 catalysts

Summarization: The reaction of captured carbon dioxide with renewable hydrogen towards the eventual indirect production of liquid hydrocarbons via CO2 reduction to CO (reverse water-gas shift reaction, rWGS) is a promising pathway in the general scheme of worldwide CO2 valorization. Copper-ceria oxides have been largely employed as rWGS catalysts owing to their unique properties linked to copper-ceria interactions. Here, we report on the fine-tuning of CuO/CeO2 composites by means of alkali promotion. In particular, this work aims at exploring the effect of cesium doping (0–4 atoms Cs per nm2) on co-precipitated CuO/CeO2 catalysts under CO2 hydrogenation conditions. The as-prepared samples were characterized by N2 physisorption, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), CO2-temperature programmed desorption (CO2-TPD), Fourier-transform infrared spectroscopy (FTIR) of pyridine adsorption and CO-diffuse reflectance Fourier-transform infrared spectroscopy (CO-DRIFTS). The results demonstrated that a low amount of Cs exerted a beneficial effect on CO selectivity, inhibiting, however, CO2 conversion. Specifically, a doping of 2 atoms Cs per nm2 offers > 96 % CO selectivity and equilibrium CO2 conversion at temperatures as low as 430 °C, whereas further increase in cesium loading had no additional impact. The present findings can be mainly interpreted on a basis of the alkali effect on the textural and acid/base properties; Cs doping results in a significant reduction of the surface area and thus to a lower population of active sites for CO2 conversion, whereas it enhances the formation of basic sites and the stabilization of partially reduced Cu+ species, favoring CO selectivity.Presented on: Journal of Co2 Utilizatio

Erratum to “Effect of alkali (Cs) doping on the surface chemistry and CO2 hydrogenation performance of CuO/CeO2 catalysts” [J. CO2 Util. 44 (2021) 101408]

Summarization: Correction to "Effect of alkali (Cs) doping on the surface chemistry and CO2 hydrogenation performance of CuO/CeO2 catalysts" article, published at Journal of CO2 Utilization, vol 44, February 2021.Presented on