Effective factors on performance of zeolite based metal catalysts in light hydrocarbon aromatization

Aromatic hydrocarbons are essential compounds, that the presence of which in fuels can improve the octane number. The conversion of the light alkanes to high value aromatics is vital from theoretical and industrial standpoints. Zeolites such as ZSM-5 play an essential role in the aromatization of light alkanes. This paper highlights the mechanism of aromatization of light alkanes such as methane, ethane, propane, butane, and its isomers. Furthermore, effective factors on the aromatization of light alkanes including metal type, crystallinity, acidity, space velocity, pretreatment of zeolites, co-feeding of light hydrocarbon, and operating factors such as temperature have been investigated to determine how a system of zeolite with metals can be useful to reach aromatization with high conversion.

Analysis of the NOx storage behaviour during cold start of modern SCR flow-through substrates and SCR on-filter substrates

Selective catalytic reduction (SCR) systems are the state-of-the-art technology to reduce nitrogen oxide emissions (NOx) of modern diesel engines. The system behaviour is well understood in the common temperature working area. However, the system properties below light-off temperature are less well known and offer a wide scope for further investigations. Vehicle measurements show that under specific conditions during cold start, NOx can be partially stored and converted on on-filter and flow-through SCR catalysts. The purpose of this work was in a first step to analyse the main influence parameters on the NOx storage behaviour. Therefore, synthetic gas test bench measurements have been carried out, varying the gas concentrations, temperature, and gas hourly space velocity (GHSV). These investigations showed that the NOx storage effect strongly depends on the NH3 level stored in the catalyst, GHSV, the adsorbed water (H2O) on the catalyst, and the temperature of the catalyst. Further influence parameters such as the gas composition with focus on carbon monoxide (CO), short-chain hydrocarbons and long-chain hydrocarbons have been analysed on a synthetic gas test bench. Depending on operating conditions, a significant amount of NOx can be stored on a dry catalyst during the cold start phase. The water vapor from the combustion condenses on the cold exhaust pipe during the first seconds, or up to a few minutes after a cold start. As the water vapor reaches the surface of the catalyst, it condenses and adsorbs onto it, leading to a sudden temperature rise. This exothermal reaction causes the stored NOx to be desorbed, and furthermore it is partially reduced by the NH3 stored in the catalyst.

Cleaner Fuel Production via Co-Processing of Vacuum Gas Oil with Rapeseed Oil Using a Novel NiW/Acid-Modified Phonolite Catalyst

Clean biofuels are a helpful tool to comply with strict emission standards. The co-processing approach seems to be a compromise solution, allowing the processing of partially bio-based feedstock by utilizing existing units, overcoming the need for high investment in new infrastructures. We performed a model co-processing experiment using vacuum gas oil (VGO) mixed with different contents (0%, 30%, 50%, 70%, 90%, and 100%) of rapeseed oil (RSO), utilizing a nickel–tungsten sulfide catalyst supported on acid-modified phonolite. The experiments were performed using a fixed-bed flow reactor at 420 °C, a hydrogen pressure of 18 MPa, and a weight hourly space velocity (WHSV) of 3 h−1. Surprisingly, the catalyst stayed active despite rising oxygen levels in the feedstock. In the liquid products, the raw diesel (180–360 °C) and jet fuel (120–290 °C) fraction concentrations increased together with increasing RSO share in the feedstock. The sulfur content was lower than 200 ppm for all the products collected using feedstocks with an RSO share of up to 50%. However, for all the products gained from the feedstock with an RSO share of ≥50%, the sulfur level was above the threshold of 200 ppm. The catalyst shifted its functionality from hydrodesulfurization to (hydro)decarboxylation when there was a higher ratio of RSO than VGO content in the feedstock, which seems to be confirmed by gas analysis where increased CO2 content was found after the change to feedstocks containing 50% or more RSO. According to the results, NiW/acid-modified phonolite is a suitable catalyst for the processing of feedstocks with high triglyceride content.

Recent Progress in the Steam Reforming of Bio-Oil for Hydrogen Production: A Review of Operating Parameters, Catalytic Systems and Technological Innovations

The present review focuses on the production of renewable hydrogen through the catalytic steam reforming of bio-oil, the liquid product of the fast pyrolysis of biomass. Although in theory the process is capable of producing high yields of hydrogen, in practice, certain technological issues require radical improvements before its commercialization. Herein, we illustrate the fundamental knowledge behind the technology of the steam reforming of bio-oil and critically discuss the major factors influencing the reforming process such as the feedstock composition, the reactor design, the reaction temperature and pressure, the steam to carbon ratio and the hour space velocity. We also emphasize the latest research for the best suited reforming catalysts among the specific groups of noble metal, transition metal, bimetallic and perovskite type catalysts. The effect of the catalyst preparation method and the technological obstacle of catalytic deactivation due to coke deposition, metal sintering, metal oxidation and sulfur poisoning are addressed. Finally, various novel modified steam reforming techniques which are under development are discussed, such as the in-line two-stage pyrolysis and steam reforming, the sorption enhanced steam reforming (SESR) and the chemical looping steam reforming (CLSR). Moreover, we argue that while the majority of research studies examine hydrogen generation using different model compounds, much work must be done to optimally treat the raw or aqueous bio-oil mixtures for efficient practical use. Moreover, further research is also required on the reaction mechanisms and kinetics of the process, as these have not yet been fully understood.

Optimization of Operating Conditions for CO2 Methanation Process Using Design of Experiments

In this study, the Taguchi experimental design method using an L16 orthogonal array was attempted in order to investigate the optimal operating conditions for the CO2 methanation process in Ni-based catalysts. The relative influence of the main factors affecting CO2 conversion and CH4 yield was ranked as follows: reactor pressure > space velocity > reaction temperature. The optimal combination of operating conditions was a reactor temperature of 315 °C, a pressure of 19 bar, and a space velocity of 6000 h−1. The effect of the H2/CO2 ratio on CO2 conversion and CH4 yield was further considered under these optimal operating conditions. Moreover, the catalyst was characterized in order to investigate the production of coke through Brunauer–Emmett–Teller analysis, thermogravimetric analysis, and scanning electron microscopy. The amount of coke produced after the reaction for approximately 24 h was ~2 wt.%. Therefore, the desired CH4 yield and long-term operational stability were successfully obtained using the Taguchi design method and catalyst characterization.

Core-Shell-Like Structured Co3O4@SiO2 Catalyst for Highly Efficient Catalytic Elimination of Ozone

Co3O4 is an environmental catalyst that can effectively decompose ozone, but is strongly affected by water vapor. In this study, Co3O4@SiO2 catalysts with a core-shell-like structure were synthesized following the hydrothermal method. At 60% relative humidity and a space velocity of 720,000 h−1, the prepared Co3O4@SiO2 obtained 95% ozone decomposition for 40 ppm ozone after 6 h, which far outperformed that of the 25wt% Co3O4/SiO2 catalysts. The superiority of Co3O4@SiO2 is ascribed to its core@shell structure, in which Co3O4 is wrapped inside the SiO2 shell structure to avoid air exposure. This research provides important guidance for the high humidity resistance of catalysts for ozone decomposition.

Thermocracking of a heavy fraction of the oil residue in a mixture with shale

The process of tar thermal cracking in a mixture with crushed oil shale to obtain components of motor fuels and raw materials for the process of thermal cracking is investigated in this paper. The optimization results of technological parameters (shale concentration, temperature, and duration) are presented and the material balance (mass.%) of the process is made. It was found that during single-stage processing under relatively mild conditions (5 MPa, 425C, feed space velocity of 1.0 h-1), a deep destruction of tar is achieved (the yield of the gasoline fraction from boiling point to 200C is ~12 wt.%; medium distillates with boil. point 200370C-43-44 mass.%; raw materials for thermal cracking with boil. point above 370C ~15-16 wt.% on per the original tar). The generating coke-like products and the V and Ni contained in the raw materials are deposited on the mineral part of the shale and removed from the reaction zone with the liquid products of the process.

Investigation of the Zinc-Copper Catalyst NIAP-06-06 for Steam Conversion of Carbon Monoxide in the Synthesis of Methanol

The possibility to use the zinc-copper catalyst NIAP-06-06 for steam conversion of CO in the synthesis of methanol was explored. The catalyst was characterized by means of TPR H2, XRD and SEM methods and tested in the methanol synthesis in flow and circulation modes at a pressure of 5.0 MPa and gas hourly space velocity of 3000 h–1 over a temperature range of 220–260 °С. The catalyst was shown to be highly active and selective toward the methanol synthesis from a gas with the H2 /СО ratio 3.9, which is obtained by steam conversion of methane. The use of tubular catalytic reactors connected in series in the flow-circulation mode makes it possible to convert more than 70 % of CO and obtain crude methanol with the concentration of 95 %. In the circulation mode, a methanol output of 427.7 kg/(m3 cat·h) was achieved on the catalyst.

Efficient electrocatalytic acetylene semihydrogenation by electron–rich metal sites in N–heterocyclic carbene metal complexes

Electrocatalytic acetylene semihydrogenation is a promising alternative to thermocatalytic acetylene hydrogenation due to its environmental benignity and economic efficiency, but its performance is far below that of the thermocatalytic reaction because of strong competition from side reactions, including hydrogen evolution, overhydrogenation and carbon–carbon coupling reactions. We develop N–heterocyclic carbene–metal complexes, with electron–rich metal centers owing to the strongly σ–donating N–heterocyclic carbene ligands, as electrocatalysts for selective acetylene semihydrogenation. Experimental and theoretical investigations reveal that the copper sites in N–heterocyclic carbene–copper facilitate the absorption of electrophilic acetylene and the desorption of nucleophilic ethylene, ultimately suppressing the side reactions during electrocatalytic acetylene semihydrogenation, and exhibit superior semihydrogenation performance, with faradaic efficiencies of ≥98 % under pure acetylene flow. Even in a crude ethylene feed containing 1 % acetylene (1 × 104 ppm), N–heterocyclic carbene–copper affords a specific selectivity of >99 % during a 100–h stability test, continuous ethylene production with only ~30 ppm acetylene, a large space velocity of up to 9.6 × 105 mL·gcat−1·h−1, and a turnover frequency of 2.1 × 10−2 s−1, dramatically outperforming currently reported thermocatalysts.