Recently, the utilization of carbon dioxide has gained in consideration as it may contribute to improve the economics of CO2 capture process by producing added value goods and is now considered a valid alternative to geological CO2 storage. Nowadays, the scientific community considers the integrated carbon capture, utilization and storage an important mitigation technology that involves the carbon dioxide sequestration from fuel combustion or industrial processes, its transport (via ship or pipeline) and conversion into valuable products or its permanent storage deep underground in geological formations. Noteworthy, CCS is functional to a linear economy, whereas utilization of carbon dioxide is at the hearth of a circular economy and its strategic role will grow in the future. In this mini review, the current state of the art in the field of capture, disposal, and reuse of CO2 as technologies for its overall reduction in the atmosphere will be discussed.

Atmospheric CO2 mitigation technologies: carbon capture utilization and storage

In the context of a carbon neutral economy, catalytic CO2 hydrogenation to methanol is one crucial technology for CO2 mitigation providing solutions for manufacturing future fuels, chemicals, and materials. However, most of the presently known catalyst systems are used at temperatures over 220 °C, which limits the theoretical yield of methanol production due to the exothermic nature of this transformation. In this review, we summarize state-of-the-art catalysts, focusing on the rationales behind, for CO2 hydrogenation to methanol at temperatures lower than 170 °C. Both hydrogenation with homogeneous and heterogeneous catalysts is covered. Typically, additives (alcohols, amines or aminoalcohols) are used to transform CO2 into intermediates, which can further be reduced into methanol. In the first part, molecular catalysts are discussed, organized into: (1) monofunctional, (2) M/NH bifunctional, and (3) aromatization-dearomatization bifunctional molecular catalysts. In the second part, heterogeneous catalysts are elaborated, organized into: (1) metal/metal or metal/support, (2) active-site/N or active-site/OH bifunctional heterogeneous catalysts, and (3) cooperation of catalysts and additives in a tandem process via crucial intermediates. Although many insights have been gained in this transformation, in particular for molecular catalysts, the mechanisms in the presence of heterogeneous catalysts remain descriptive and insights unclear.

Homogeneous and heterogeneous catalysts for hydrogenation of CO2 to methanol under mild conditions.

https://pubs.rsc.org/en/content/articlepdf/2021/GC/D0GC03349A

Direct dimethyl carbonate synthesis from CO2 and methanol catalyzed by CeO2 and assisted by 2-cyanopyridine: a cradle-to-gate greenhouse gas emission study

https://onlinelibrary.wiley.com/doi/pdf/10.1002/sus2.2

Carbon dioxide copolymers: Emerging sustainable materials for versatile applications

The chemical recycling of end-of-life plastic waste streams can contribute to a resource-conserving and sustainable society. This matter of recycling is composed of a sequence of depolymerization and subsequent polymerization reactions. In this regard, we have studied the chemical recycling of end-of-life poly(bisphenol A carbonate) applying phenol as depolymerization reagent. In the presence of catalytic amounts of alkali metal halides as products bisphenol A and diphenyl carbonate were obtained in excellent turnover frequencies of up to 1392 h-1 and short reaction times. These depolymerization products offer the straightforward possibility to close the cycle by producing new poly(bisphenol A carbonate) and as second product phenol, which can be reused for further depolymerizations.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/open.201900149

Toshiaki Sawa

Papers

Industrialization and Expansion of Green Sustainable Chemical Process: A Review of Non-phosgene Polycarbonate from CO2