Production of valuable chemicals from glycerol using carbon fiber catalysts derived from ethylene

Ethylene was thermocatalytically transformed into carbon products via a CCVD process. The filamentous carbon obtained was further modified with concentrated sulfuric acid or 4‐benzenediazonium sulfonate (BDS) to produce acid-type catalysts. The as-prepared samples were characterized by SEM and TEM techniques to confirm their morphological features. TG, XRD, elemental, and porosity analyses were also performed to assess the quality of these materials. The fabricated carbons were tested in eco-friendly green synthesis of value-added fuel bio-additives, namely in glycerol esterification. The reaction of glycerol transformation was performed with acetic acid at 80 °C using different glycerol to acetic acid (Gly/AA) molar ratios. The samples functionalized with diazonium salt showed better performance in the above process than those modified with H2SO4, and this was found to be directly related to the degree of surface functionalization with acidic sites. BDS-modified carbon fibers allowed obtaining acceptable results within 6 h when the reaction was performed with a Gly/AA molar ratio of 1:6, however, the dominant products in this case were mono- and diacetins. Extended reaction time altered the distribution of products. Finally, the combined selectivity to the targeted acetins (i.e., DA and TA) was about 75.5%. A direct correlation between the content of –SO3H groups of CNFs and the yield of higher acetins was found.

Nanostructured NiMoS2/Carbon Catalysts for Syngas Conversion to Higher Alcohols

Syngas conversion to higher alcohols remains a very attractive alternative due to the abundance of syngas feedstock, such as renewable carbon and waste-carbon resources. Catalysts suitable for syngas conversion still show low selectivity to alcohols. In this article, we present nanostructured NiMoS2 and CoMoS2 catalysts supported on activated carbon pellets and design strategies to improve its selectivity towards higher alcohols. Activated carbon pellets were treated with concentrated HNO3 to enlarge porous channels and enable better dispersion of NiMoS2 and CoMoS2. These treatment steps lead to a formation of nanostructured NiMoS2 and CoMoS2 catalysts and promoted higher selectivity to ethanol, propanol and butanol. BET surface area of 532 m2 g−1 was obtained for NiMoS2/Carbon catalysts from the nitrogen physisorption analysis. In catalytic tests, the highest CO conversion (39.1%) was achieved by the NiMoS2/Carbon, whereas the CoMoS2/Carbon showed the highest alcohol selectivity (74.4%). CoMoS2 catalysts supported on activated carbon pellets proved to be highly active towards undesired by-product “filamentous carbon.”

Syngas production by bi-reforming methane on an Ni–K-promoted catalyst using hydrotalcites and filamentous carbon as a support material

A Ni phase dispersed in CO2 is used with a K promoter in the BRM. The LDH support structure collapses at high temperatures, inducing large Ni crystal sizes, and disfavoring activity. The catalyst is compensated by the K promoter, and the formation of an Mg–Al-spinel.

Correction: Syngas production by bi-reforming methane on an Ni–K-promoted catalyst using hydrotalcites and filamentous carbon as a support material

Correction for ‘Syngas production by bi-reforming methane on an Ni–K-promoted catalyst using hydrotalcites and filamentous carbon as a support material’ by Adelino F. Cunha et al., RSC Adv., 2020, 10, 21158–21173, DOI: 10.1039/D0RA03264F.

Ni Catalysts Based on Attapulgite for Hydrogen Production through the Glycerol Steam Reforming Reaction

Attapulgite (ATP, a natural clay) was used as carrier to produce a nickel-based catalyst (Ni/ATP) for the work that is presented herein. Its catalytic performance was comparatively assessed with a standard Ni/Al2O3 sample for the glycerol steam reforming (GSR) reaction. It was shown that the ATP support led to lower mean Ni crystallite size, i.e., it increased the dispersion of the active phase, to the easier reduction of NiO and also increased the basicity of the catalytic material. It was also shown that it had a significant effect on the distribution of the gaseous products. Specifically, for the Ni/ATP catalyst, the production of liquid effluents was minimal and subsequently, conversion of glycerol into gaseous products was higher. Importantly, the Ni/ATP favored the conversion into H2 and CO2 to the detriment of CO and CH4. The stability experiments, which were undertaken at a low WGFR, showed that the activity of both catalysts was affected with time as a result of carbon deposition and/or metal particle sintering. An examination of the spent catalysts revealed that the coke deposits consisted of filamentous carbon, a type that is known to encapsulate the active phase with fatal consequences.

Synthesis and Functionalization of Filamentous Carbon Material via Decomposition of 1,2-Dichlorethane over Self-Organizing Ni-Mo Catalyst

Segmented carbon filaments produced by catalytic decomposition of 1,2-dichloroethane over Ni-Mo (8 wt.% Mo) self-organizing catalyst were subjected to functionalization in two different regimes. The structure, textural properties and chemical composition of surface were studied using SEM, Raman spectroscopy, adsorption (BET) and XPS. It was shown that oxidation of carbon nanomaterial in concentrated HNO3 results in enhancement of O-containing groups concentration (from 2.2 to 6.8 wt.%), increase in specific surface area (from 224 to 280 m2/g) and slight structural disorder of graphitic material (increase of ID/IG ratio from 2.15 to 1.84).

Ni-based catalysts for steam reforming of tar model derived from biomass gasification

Tar formation during biomass gasification is a major barrier to utilise the produced syngas, which clogs processing equipment. In the present study, steam reforming of gasification-derived tar (phenol, toluene, naphthalene, and pyrene) was catalysed by Ni/dolomite, Ni/dolomite/Al2O3, Ni/dolomite/La2O3, Ni/dolomite/CeO2, and Ni/dolomite/ZrO2 for hydrogen production. The steam reforming experiment was conducted in a fixed bed reactor at 700 °C and the steam-to-carbon molar ratio of 1 under atmospheric pressure. After the catalytic test, the spent catalysts were characterised by thermogravimetric analysis and variable-pressure scanning electron microscope. The aim of this study is to investigate the catalytic activity of Ni-based catalysts in terms of tar conversion and their deactivation characteristic. The current results revealed that all the catalysts showed almost full conversion of tar (98.8%-99.9%) and considerably low amount of coke deposited in the form of amorphous and filamentous carbon (15.9-178.5 mg gcat-1). Among the catalysts studied, Ni/dolomite/La2O3 gave the highest catalytic activity for steam reforming of gasified biomass tar and lowest coke formation.

Synthesis of Filamentous Carbon Material via Decomposition of CF2Cl2 over Self-Organizing Ni-Cr Catalyst

The way to produce the nanostructured carbon filaments via H2-assisted catalytic decomposition of CF2Cl2 over self-organizing Ni-based catalyst has been reported. The self-organizing 6%Ni/CNM catalyst, where CNM is a carbon nanomaterial, resulted from carbon erosion of bulk Ni-Cr alloy (nichrome) in C2H4Cl2 vapors was also shown to be effective for catalytic chemical vapor deposition of CF2Cl2 with formation of bimodal carbon structures. It was demonstrated that interaction of nichrome with CF2Cl2/H2 reaction mixture at 600 °C leads to its rapid disintegration caused by carbon erosion to form disperse active Ni-particles catalyzing the growth of carbon filaments. The resulted filamentous carbon material is characterized with high textural parameters.