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Abstract There are millions of tonnes of petroleum coke stockpiled worldwide, but to take advantage of this potential resource, a better understanding of how to activate this feedstock with less waste is required. The impact of steam addition during chemical activation of petroleum coke with a high sulfur content (~6.5 wt%) was evaluated with two chemical agents (KOH and NaOH), chemical molar ratios (from 0.12 to 1.02 or mass ratios from 0.5 to 3) and activation times (0 to 120 min) at 1073 K. Based on the yield and total pore volume developed, co-activation of KOH and steam was an effective way to reduce the amount of chemical agent required, while widening the pores from ~ 1 nm to up to 4 nm. In contrast, the addition of steam to the activation with NaOH resulted in less pore development and essentially no change in the pore size. At the activation conditions, there is likely a molten phase around the particles that slows steam gasification and has a composition that changes with the introduction of steam. Graphical abstract Unlabelled Image Highlights • KOH use can be reduced by introducing steam after pores are developed. • 50% yield and 1.1 cm3/g for activation with 2:1 KOH:petcoke mass ratio and steam • Steam exposure widens the pores created by KOH from <2 nm to up to 4 nm • Chemical layer around particles reduces gasification rate. • After NaOH activation steam addition reduced the pore volume. [ABSTRACT FROM AUTHOR]

Porous carbon materials are produced in large amounts but are generally microporous and, thus, may have diffusion limitations for reactions with larger molecules. In this study, iron, lanthanum, cerium, nickel and cobalt oxides were studied as catalysts to enlarge or create mesopores in carbonaceous materials through metal-catalyzed steam activation. The carbonaceous materials were impregnated with 25 wt% metal nitrate salts and exposed to humidified N 2 (steam, 50 cm 3 /min N 2 plus 5 cm 3 /h liquid water) at 1073 K. The metal precursors were converted to metal oxides, and produced carbon samples with pore sizes between 2 and 60 nm and mesopore volumes up to 0.65 cm 3 /g. The size of the pores created was determined by the metal oxide size. Cobalt oxide produced the largest pores followed by nickel, cerium, lanthanum and iron oxide. For materials with mainly micropores, activation proceeded by gasification and collapse of pore walls, while for materials with larger pores, pore widening occurred. Catalyst recycling was achieved by acid leaching after activation, and no differences in the produced materials were found using fresh or recovered cerium nitrate. [ABSTRACT FROM AUTHOR]

Bitumen upgrading involves the hydroconversion of larger molecules that require catalyst supports with meso- and/or macropores for access to the active sites. In this study, various activation processes were studied to activate delayed petroleum coke, which is a by-product of oil sands bitumen upgrading and an inexpensive source of carbon. The petroleum coke was subjected to steam, chemical (KOH, NaOH) and combined activation methods at 973 K and 1073 K. The produced materials were characterized with nitrogen physisorption at 77 K and scanning electron microscopy. Combined with the yields, the results suggested that the combination of steam with sodium or potassium increased the mesoporosity of the carbon samples possibly by a catalytic gasification mechanism. A mesopore volume of 0.39 cm 3 /g with a yield of 27% was achieved by simultaneously activating with sodium and steam. Washing the material after activation with sodium and before introducing steam produced the same mesoporosity but doubled the yield, confirming that steam alone is not effective at creating porosity. The accessibility of the larger pores was confirmed with the adsorption of asphaltenes from Athabasca extra-heavy crude oil. The capacity for asphaltene adsorption increased with increasing mesopore volume. [ABSTRACT FROM AUTHOR]

Petroleum coke (petcoke) containing sulphur has limited direct applications, but stockpiling the material creates an environmental issue. Although chemical activation can be used to valorise the petcoke to activated carbon, sulphur is released creating alternative environmental problems. In this study, a new activation method for high sulphur content (∼6.5 wt%) petcoke was developed to retain sulphur and prepare transition metal sulphide catalysts simultaneously. Petcoke was mixed with tungsten and nickel precursors and then activated by KOH at 600 °C in the presence of steam. After washing, the activated petcoke had a sulphur content of 5.1 wt%, which was much higher than that in the absence of steam during activation (0.4 wt%). Sulphur was also retained (>4 wt% of sulphur) when other transition metals including molybdenum and cobalt were used. Characterization by XRD, XPS, and SEM-EDS suggested that sulphur was retained on the activated petcoke in the form of metal sulphides. Further thermodynamic analysis of the system revealed that in the presence of steam an H 2 S/H 2 mixture was generated, and this mixture promoted the formation of the metal sulphide species when metal precursors were introduced. The prepared metal sulphide catalysts were active for several reactions including the photoreduction of CO 2. Overall, this study provided an effective method to prepare metal sulphide catalysts from sulphur containing carbonaceous waste. [Display omitted] • Sulphur remained in petcoke after KOH and steam activation. • Metal sulphide catalysts were obtained in-situ during activation. • H 2 O has crucial role in sulphur retention and catalysts formation. • Prepared catalysts were active for photoreduction of CO 2. [ABSTRACT FROM AUTHOR]

Different CuO nanoparticles were synthesized and tested in CuO:TiO 2 physical mixtures for hydrogen production through glycerol photoreforming. CuO alone was inactive whereas its presence in CuO:TiO 2 mixtures significantly improved the photoactivity of TiO 2 , with smaller CuO nanoparticles leading to higher hydrogen productions. Results obtained through combination of EPR and CV studies suggested the existence of a Cu(II)-Cu0 catalytic cycle. Thus, electrons promoted to the conduction band of titania could be used for CuO reduction to Cu which in turn would enable hydrogen production regenerating Cu2+ for a new catalytic cycle. All in all, a hydrogen production of 88 mmol·g−1 was obtained after 5 h on a CuO:TiO 2 (10% w/w) physical mixture which is comparable to that achieved in a previous study under identical reaction conditions on 1.5%Pt/TiO 2. [Display omitted] • H 2 production via glycerol photoreforming enhanced on CuO:TiO 2 physical mixtures. • H 2 production values in the same order as those found for supported noble metals. • EPR studies evidenced the formation of Cu(I) or Cu0 species on UV irradiation. • CV studies suggested the existence of a CuO to Cu(0) photocatalytic cycle. • Electrons for H 2 generation are first transferred from titania to copper species. [ABSTRACT FROM AUTHOR]