Improved Catalysts for Reacting Two Greenhouse Gases With Each Other to Make Cleaner Fuels.

[NNadir]

The paper to which I'll refer in this post is this one: Highly Efficient Conversion of Greenhouse Gases Using a Quadruple Mixed Oxide-Supported Nickel Catalyst in Reforming Process Orrakanya Phichairatanaphong, Nevzat Yigit, Günther Rupprechter, Metta Chareonpanich, and Waleeporn Donphai Industrial & Engineering Chemistry Research 2023 62 (40), 16254-16267

The paper is open to the public to read for free, but nonetheless I'll excerpt it.

The process is known as "dry reforming, in which carbon dioxide reacts (in this case) with methane to yield a product called "syn gas," a mixture of hydrogen and carbon monoxide which can be used catalytically to make dirty fuels like gasoline, diesel and jet fuel, or (in the best case) a clean fuel with very little climate impact, DME, dimethyl ether. The fact that DME is the best option for portable fuels and is superior to all other fuels has little bearing on whether it will take over our infrastructure. (We have a lot of hydrogen fuel morons here and elsewhere.)

A Giant Climate Lie: When they're selling hydrogen, what they're really selling is fossil fuels.

Note that this technology involves the use of the dangerous fossil fuel so called "natural gas" which was declared in the "Wedgies" paper of 2004 by "we're not antinukes" antinukes at Princeton University, Pacala and Sokolow, to be a "clean fuel" that was all we needed to address climate change.

Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies

Twenty years later we have not addressed not climate change; we're not even close. Things are getting worse faster than ever.

The Pacala and Socolow paper was published in August of 2004. By August of 2023 the concentration of the dangerous fossil fuel waste carbon dioxide in the planetary atmosphere had risen by 43 ppm.

The problem with dry reforming, which has been practiced on an industrial scale, is the lifetime of the catalysts.

The paper, which again is open to the public and can be read by anyone interested, cited at the beginning of this post seeks to address this problem, by proposing a long lived robust catalyst that carries out the reaction efficiently.

From the introduction:

Global warming and the greenhouse effect are concerns for all countries worldwide, and it is essential to be aware of their impacts. The increasing emissions of the greenhouse gases directly contribute to rising global temperatures and extreme weather events. The main sources of the greenhouse gas emissions are electricity generation, transportation, industrial processes, and agricultural activities, with carbon dioxide (CO₂) and methane (CH4) being the most significant contributors. Owing to the increasing demand for the utilization of the greenhouse gases, along with the growing interest in renewable and cleaner sources of energy, the process of reforming reaction, which involves combining CO₂ and CH4, to produce the synthesis gas, a mixture of hydrogen (H2) and carbon monoxide (CO), has gained significant attention. (1–3) The H2 obtained from this process can be utilized as a clean and sustainable energy source, while its reaction with CO via the Fischer–Tropsch process can generate high value-added hydrocarbons (olefin/paraffin) to serve as raw materials in petrochemical industries. (1–3) The dry reforming reaction is a process that is endothermic in nature and necessitates high temperatures to be carried out successfully. To decrease the energy required for the reaction, active catalysts are necessary. Among the various catalysts investigated, nickel-based catalysts exhibit remarkable performance at moderate temperatures (500–600 °C) and low toxicity. (4–6) However, the utilization of nickel catalysts is limited by their proneness to degradation caused by coking and the high-temperature sintering effect.

By improving the dispersion of the nickel metal, enhancing the surface basicity properties, and inhibiting coke deposition on the surface, the incorporation of a support significantly enhances both the activity and stability of the catalyst. A variety of metal oxides, including cerium oxide (CeO₂), (7) magnesium oxide (MgO), (8) alumina (Al₂O₃), (9) zinc oxide (ZnO), magnesium aluminate (MgAl₂O₄), and zinc aluminate (ZnAl₂O₄), (10) have been employed as supports in the dry reforming reaction. Furthermore, mixed metal oxides, for instance, CeO₂–MgAl₂O₄, CeO₂–ZnAl₂O₄, Al₂O₃–CeO₂, Ce1–xZrxO₂, and MgO–CeO₂, have also been utilized as supports in the dry reforming reaction due to their unique surface characteristics. The CeO₂ surface comprised Ce⁴⁺ and Ce³⁺ species on its lattice site bounded by oxygen ions, leading to the presence of oxygen vacancies, which adsorbed the oxygen formed by the CO₂ dissociation and helped reduce coke accumulation on the catalyst surface. (11–13) Alkaline metal oxides, such as MgO, increase the basic surface properties, resulting in improved CO₂ adsorption and coke resistance. (13) ZnO promotes CO₂ adsorption and dissociation, as well as nickel dispersion, leading to an increase in the activity and stability while simultaneously decreasing carbon formation through the reverse Boudouard reaction. (14,15) Additionally, at high calcination temperatures, MgO and ZnO can form MgAl₂O₄ and ZnAl₂O₄ spinel structures, respectively. These spinel structures can inhibit the deposition of coke on the surface by means of their strong interaction with the nickel support. (10,16) Although mixed metal oxide-supported nickel catalysts are extensively employed in dry reforming, additional investigation is required to improve the catalyst’s activity and stability.

Herein, the metal oxide quad-blend─Ce, Mg, Zn, and Al─is a new alternative beneficial for boosting the performance and lifetime of the nickel-based catalyst because of their synergistic effect. The mixed metal oxide support with different Ce, Mg, Zn, and Al ratios was synthesized using a soft template-assisted coprecipitation procedure. Essential insights into the catalyst activities were uncovered through the investigation of the characteristic details,─conversions, product formation, and stability in the dry reforming reaction of a metal oxide quad-blend-supported nickel catalyst─particularly via in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The outstanding high-performance CH4 and CO₂ conversions, as well as H2/CO ratio, were demonstrated by the Ce–Mg-0.5Zn–Al-supported nickel catalyst combination according to the results. Furthermore, its activity was stable during the reaction time. The impact of the molar ratio of tetra-metal oxide on the catalyst’s activity enhancement and the prolongation of its anticoking properties is due to its influence on the oxygen defects, the capacity for CO₂ adsorption and dissociation on the surface, and the active nickel stability.

My interest in dry reforming is not connected with any enthusiasm for dangerous natural gas, or for that matter as a means to provide the oft hyped but in reality chimeric "hydrogen economy" that has been the subject of mindless blather for half a century.

I see it as a means to capture carbon dioxide from the air, by dry reforming pyrolyzed biomass (which is a technology of limited utility, but limits high enough to make it a possible contributor to restoring the planetary atmosphere to health, something in which there is no current practical interest.

Carbon monoxide can, by the way disproportionate to give elemental carbon useful for various products and technology.

An interesting little paper, I think.

I trust you'll have a pleasant weekend.

[quaint]

1. Thank you for making science understandable for me.

Mostly. Partly. You have an excellent weekend as well.