Development of Electrocatalysts for Efficient Nitrogen Reduction Reaction under Ambient Condition

Assessment and optimization of an integrated wind power system for hydrogen and methane production

N2 Fixation by Plasma-Activated Processes

Thermochemical technologies for converting biomass into energy or chemicals mainly consist of combustion, pyrolysis, and gasification. This review summarizes the recent advances in biomass pyrolysis and gasification by using CO2 as a reaction medium. The CO2-looping pyrolysis or gasification of biomass is compared with conventional processes. In the integrated valorization of biomass by pyrolysis or gasification, CO2 can play a vital role in each stage, mainly including biomass pyrolysis, biomass/biochar gasification, biochar activation, and tar cracking/reforming. CO2 as a reaction medium can significantly improve the thermal efficiency of biomass pyrolysis. Pyrolysis in CO2 results in deep decomposition of biomass compared to pyrolysis in N2. Also, CO2 has an affinity to react with hydrogenated and oxygenated groups, leading to biochar with a higher specific surface area (SBET). Thus, exploiting CO2 as a reaction medium in biomass pyrolysis provides an attractive option for enhanced generation of syngas and tuned adsorption capability of biochar. In addition, the CO2 pyrolysis of biomass can enhance the thermal cracking of harmful organic compounds, thus suppressing of the formation of benzene derivatives (e.g., volatile organic compounds) and polycyclic aromatic hydrocarbons. In general, CO2 gasification of biomass serves a dual purpose of reducing pollution and generating syngas. In addition, introducing CO2 with steam as a gasifying agent can enhance CO production. The internal mineral species (e.g., K, Ca) in biomass can also improve the reactivity of char gasification and tar reforming in the entire gasification processes.

CO2-looping in biomass pyrolysis or gasification

Biochar, produced by the thermal decomposition of various biomass sources, is applied in different fields of research due to its distinctive properties. With the recent explosion of methods of a large-scale synthesis of biochar, the number of literatures relevant to biochar and biochar based materials has increased exponentially. This review exclusively focuses on the current development of biochar based functional catalysts, and provides critical emphasis on the different applications in various reactions, including (trans)esterification, catalytic reforming/cracking, gasification/pyrolysis, hydrolysis, electrochemical reactions, photocatalytic and persulfate/peroxymonosulfate oxidation, etc. Thus, in this review, we firstly present a brief description of the design and synthesis of the biochar based catalyst, and then summary the applications of these biochar based catalysts based upon different reactions. Finally, the current advances and the future perspectives of the biochar catalysts will be presented. Hopefully, this review will offer a perspective and guidelines for the future research and development of biochar based catalysts.

A review of recent developments in catalytic applications of biochar-based materials

https://pubs.rsc.org/en/content/articlepdf/2020/gc/d0gc02058c

Plasma-driven catalysis: green ammonia synthesis with intermittent electricity

The gasification of pinewood pyrolysis oil with potassium hydroxide dissolved was investigated, using a potassium salt loaded char as catalyst, to screen if this would result in a lower tar yield in the product stream. Experiments were performed at 700 °C, after which the product stream was thoroughly condensed and the gas stream was analyzed. The results show a significant tar reduction for a fixed potassium-loaded char bed at a gas hourly space velocity (GC1HSV) of 237 h–1. If the GC1HSV is reduced, the reduction in tar increases. A reduction of a factor of 10 was observed when the feed was also loaded with 5 wt % KOH. Based on the principle that the potassium ion catalyzes the cracking of tars into char or gas, it is proposed that this formed char is easily and fully gasifiable, leading to a feasible, continuous low-tar pyrolysis oil gasification process. The results show promise of deep tar removal under more severe conditions, resulting in a much smaller tar removal step afterward. This process would...

Potassium-Salt-Catalyzed Tar Reduction during Pyrolysis Oil Gasification

A method to fabricate catalytic membrane contactor reactors with a Pd-egg-shell distribution has been developed on α-alumina tubes, allowing excellent control over the distribution of the active phase through the wall of the alumina tube. The performance of these catalytic membrane reactors has been assessed for nitrite hydrogenation. We have shown that manipulation of the thickness of the zone containing active phase induces different diffusion lengths for nitrite and hydrogen, strongly influencing activity and selectivity. Thick active layers have proved to be more selective to nitrogen, the desired product for purification of drinking water. Surprisingly, a thick layer with active phase also induced a negative apparent order in hydrogen, which is tentatively assigned to the fact that the ratio of concentrations of reactants, hydrogen and nitrite, varies extremely in the active zone.

/pdf/egg-shell-membrane-reactors-for-nitrite-hydrogenation-s70zypng0s.pdf

Egg-shell membrane reactors for nitrite hydrogenation: manipulating kinetics and selectivity

Nitrite hydrogenation is studied in steady-state as well as transient operation using a Pd catalyst in a tubular membrane contactor reactor. A negative reaction order in hydrogen in steady state operation proofs that hydrogen and nitrite adsorb competitively. In transient operation, feeding nitrite to the Pd surface fully covered with hydrogen results initially in very low conversion of nitrite, speeding up once hydrogen is removed from part of the Pd surface. Additional proof for competitive adsorption between hydrogen and nitrite is provided by the observation that exposure of a nitrite-covered catalyst to hydrogen induces desorption of nitrite. Formation of ammonia in these experiments proceeds via two pathways, first via a fast reaction followed by extremely slow hydrogenation of adsorbed N atoms, which is kinetically not relevant. This information is relevant for designing effective and selective catalysts when operating at very low nitrite concentration.

/pdf/competitive-adsorption-of-nitrite-and-hydrogen-on-palladium-3edjw4bqo6.pdf

Competitive Adsorption of Nitrite and Hydrogen on Palladium during Nitrite Hydrogenation.

The effect of the axial temperature profile upstream and downstream of catalyst bed on the performance of non‐oxidative‐coupling‐of‐methane (NOCM) over Fe/SiO2 was determined. A three‐zone oven was used with independent temperature control of the catalyst‐zone as well as the zones upstream and downstream. It was found that catalytic initiation followed by residence time at 1000 °C downstream the catalyst bed increases CH4 conversion by a factor of 8, while decreasing carbonaceous deposit selectivity from 40 to 12 C%. Residence time at 1000 °C upstream of the catalyst bed causes deposit formation on the catalyst without significantly influencing methane conversion. A shallow catalyst bed followed by significant residence time at high temperature maximizes methane conversion and minimizes coking. This work shows that axial temperature profile and residence time upstream and downstream of the catalyst bed strongly influence the performance in catalytic NOCM

https://chemistry-europe.onlinelibrary.wiley.com/doi/pdf/10.1002/cctc.202001785

Rolf Sybren Postma

Papers

Plasma-driven catalysis: green ammonia synthesis with intermittent electricity

Potassium-Salt-Catalyzed Tar Reduction during Pyrolysis Oil Gasification

Egg-shell membrane reactors for nitrite hydrogenation: manipulating kinetics and selectivity

Competitive Adsorption of Nitrite and Hydrogen on Palladium during Nitrite Hydrogenation.

Influence of Axial Temperature Profiles on Fe/SiO2 Catalyzed Non-oxidative Coupling of Methane