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The oxidative cleavage of nonedible monounsaturated lipids such as restaurant olive oil or oil extracted from high oleic sunflowers (HOSO) is a method to produce useful C9 mono- and dicarboxylic ac...

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.

The need to decrease the concentration of CO2 in the atmosphere has led to the search for strategies to reuse such molecule as a building block for chemicals and materials or a source of carbon for fuels. The enzymatic cascade of reactions that produce the reduction of CO2 to methanol seems to be a very attractive way of reusing CO2; however, it is still far away from a potential industrial application. In this review, a summary was made of all the advances that have been made in research on such a process, particularly on two salient points: enzyme immobilization and cofactor regeneration. A brief overview of the process is initially given, with a focus on the enzymes and the cofactor, followed by a discussion of all the advances that have been made in research, on the two salient points reported above. In particular, the enzymatic regeneration of NADH is compared to the chemical, electrochemical, and photochemical conversion of NAD+ into NADH. The enzymatic regeneration, while being the most used, has several drawbacks in the cost and life of enzymes that suggest attempting alternative solutions. The reduction in the amount of NADH used (by converting CO2 electrochemically into formate) or even the substitution of NADH with less expensive mimetic molecules is discussed in the text. Such an approach is part of the attempt made to take stock of the situation and identify the points on which work still needs to be conducted to reach an exploitation level of the entire process.

Replacing fossil-C based plastics with those derived from renewable-C is one of the goals of the modern polymer industry. 2,5-Furan dicarboxylic acid (2,5-FDCA) is a candidate to substitute terephthalic acid as comonomer for polyesters. 2,5-FDCA is usually produced from C6 sugars. Carboxylation of 2-furancarboxylic acid (2-FCA) to 2,5-FDCA is an alternative synthetic approach to such monomer for polyethene furoate (PEF) preparation. In this work, several inorganic carbonates have been tested in the 2-FCA carboxylation in presence and absence of CO2. A key copper intermediate has been synthesized and fully characterized that is able to increase the acidity and, thus, the reactivity of 5-H towards a carbonate species. Carboxylation occurs at 93% yield in absence of CO2. The role of metal salts and CO2 were investigated. The conversion yield of 2-FCA into the dicarboxylic acid is related to the charge density on the metal cation, increasing with lower charge-density.

5-Hydroxymethylfurfural (5-HMF) can be considered a prominent building block: because of the presence of the alcohol and aldehyde moieties, it can be used to generate useful molecules as chemicals of industrial interest with high added value, monomers for polymers, and even fuels. This article shows how building up mixed oxides of different complexities and properties may drive the selectivity toward one of the possible products generated from 5-HMF. In particular, mixed oxides based on cerium and other metals abundant on the earth-crust perform the selective oxidation of 5-HMF to 2,5-diformylfuran (94%), using oxygen as oxidant and water as solvent. The roles of the reaction conditions (temperature, reaction time, oxygen pressure, concentration of the substrate), the chemical composition, the acidic/basic properties, and redox properties of the catalysts are discussed.

The efficiency technologies in both the production of energy (electric–thermal–mechanic, others) from fossil-C and the use of the various forms of derived energies can play a strategic role in the reduction of the production and emission of CO2. Additionally, the use of biomass as source of fuels is shortly presented and the putative “zero-emission” property discussed.

The utilization of solar energy for driving reactions in which CO2 is converted into energy-rich products is discussed in this chapter. Three approaches are considered: i. electrolysis of water by photovoltaic energy to generate hydrogen used, in turn, for the hydrogenation of CO2 to gaseous or liquid fuels; ii. use of concentrated solar power for splitting CO2 and H2O and making Syngas; iii. the direct co-processing of water and CO2 to energy-rich products under solar irradiation. The former option can be applied in the short term as both the electrolysis and CO2 conversion are well-known processes; the second needs some further improvement of both the technology for concentrating solar energy and catalysts for H2O and CO2 splitting and may be applied in the medium term; the latter will most likely be exploited in the medium–long term as new, effective and stable photocatalysts must be discovered and advanced reactors-concentrators of solar light need to be developed.

In this chapter, carbon-free perennial primary energy sources are described and the potential of relevant technologies to produce electric or thermal energy is highlighted. Solar, wind, hydro, and geothermal power are analyzed for their contribution to substitute fossil-C in coming decades.

The basic aspects of the reactivity of carbon dioxide are featured, related to the electronic structure of the molecule. The phase diagram of CO2 is also discussed for understanding how CO2 exists in different conditions of temperature and pressure.

In this chapter, the use of fossil-C as source of energy (compared to other sources) and as raw material for the chemical industry is discussed. Some fundamental processes are illustrated for the production of liquid fuels from either coal or natural gas. Emissions of CO2 are quoted for several sectors. The syngas and Fischer–Tropsch processes are discussed more in detail in the Deep Insight (DI).

The substitution of fossil-C is an urgent task for both the scarcity of resources and stopping the emission of green-house gases, (GHGs) that impact the climate of our planet. The transfer to the atmosphere of heat, due to the inefficiency of conversion of chemical energy into other forms of energy, and CO2 is also causing the increase of atmospheric water vapor, a stronger and more abundant greenhouse gas than CO2: all actors (heat, CO2 and H2Ov) concur to increase the temperature of the planet. Partial substitution of fossil-C can be achieved by using biomass, but that alone cannot produce all the energy and goods necessary for our society. Carbon will still be present in our future, but the solution to our problems is integrating solar chemistry and biotechnologies for using atmospheric CO2. This chapter, after an introduction to Carbon Circular Economy-CCE and CO2 utilization in Chemical Industry, considers the various options available of using solar energy for CO2 conversion into energy vectors that may allow to continue to use the existing infrastructures in transport and every-day life. Two options are considered: (i) solar-based water splitting and use of H2 for chemo-catalytic CO2 conversion using known processes, or (ii) photo-co-processing of water and CO2 to afford energy products and chemicals without H2 generation, a most innovative technology. The state of the art is provided and barriers to overcome for a large-scale exploitation of the two options are highlighted. The contribution to fossil-C substitution that may come from integration of solar chemistry with material science and biotechnology concludes this chapter.

The potential of carbon recycling through CO2 utilization is “sized” here by merging all options discussed in previous chapters. It is interesting to note that in the medium-long term some 7–9 GtCO2/y can be avoided, and this is a very interesting news: coupled to the use of biomass and utilization of perennial energies (SWHG) will make possible the reduction of the extraction of fossil fuels to, most likely, one-third–one-fourth with respect to today. This will be a great achievement.

This Chapter describes the “non-chemical” uses of CO2, which means all those applications in which CO2 is not converted into other chemicals, but remains the same species. Some of the applications are quite familiar to the public (food packaging, low temperature cooling agent, fluid as fire extinguisher, cleaning fluid, smoke effects, and water treatment), others are typical of industry and less known to the public. In water treatment, indeed, CO2 is converted into its hydrated forms; this is the only case in which CO2 loses its original nature, as it happens anytime CO2 is dissolved in water.

In this chapter, the relevance of Carbon Dioxide Utilization (CCU) to Innovation and Sustainability of the Chemical Industry and to the strategy of the Circular Economy is discussed. A number of examples are presented of processes which may convert CO2 into added-value chemicals, polymeric materials, and fuels which have each a market higher than 1 Mt/y, causing a significant reduction of CO2 emission. Only thermal processes are considered here, while solar-driven processes are discussed in Chap. 10 and the integration of Chemical Catalysis and Biotechnology is presented in Chap. 11.

Fossil-C, in the form of coal, natural gas, and oil, covers 81+% of the energy necessary to satisfy the needs of our society. The continued use of fossil-C causes the accumulation of carbon dioxide in the atmosphere. The reduction of the emission of CO2 is becoming urgent.

The Capture and Storage of Carbon Dioxide (CCS) is illustrated in this chapter. CO2 can be captured from point sources (power plants and industries) or directly from the atmosphere (Direct Air Capture (DAC)) or even from mobile sources. Technologies for the capture are illustrated here and some examples of disposal in natural fields are described, together with fixation into long-lasting materials, such as inorganic carbonates.

In this chapter, the structure of the atmosphere is presented with the natural cycles of several species. The natural green house effect is discussed and the way in which CO2 and other GHGs contribute to its enhancement is analyzed.

The utilization of carbon dioxide as building block for chemicals or source of carbon for energy products has been explored for over 40 years now, with varying allure. In correspondence with oil-crises, the use of CO2 has come into the spotlight, soon set aside when the crisis was over due to the low price of fossil carbon and the convenience of using established technologies. Nowadays, there is a continuous shift from fossil-C-based to perennial (solar, wind, geothermal, hydro-power) energy-driven processes that will also have a great potential to convert large amounts of carbon dioxide. The integration of biotechnology and catalysis will be a key player towards the utilization of CO2 in several different applications, reducing both the extraction of fossil carbon and the carbon transfer to the atmosphere.

The present study describes an unprecedented approach to valorize potentially hazardous poly-(bisphenol A carbonate) (PC) wastes. In THF, under non-severe conditions (120 °C), the reaction of PC with long-chain diamines H2NRNH2 (2 equivalents) provided a tool to regenerate the monomer bisphenol A (BPA; 83–95%, isolated) and repurpose waste PC into [-NHRNHCO-]n polyureas (PUs; 78–99%, isolated) through a non-isocyanate route. Basic diamines (1,6-diaminohexane, 4,7,10-trioxa-1,13-tridecanediamine, meta-xylylenediamine, para-xylylenediamine) reacted with PC without any auxiliary catalyst; less reactive aromatic diamines (4,4’-diaminodiphenylmethane, 2,4-diaminotoluene) required the assistance of a base catalyst (1,8-diazabicyclo[5.4.0]undec-7-ene, NaOH). The formation of [-NHRNHCO-]n goes through a carbamation step affording BPA and carbamate intermediates H[-OArOC(O)NHRNHC(O)-]nOArOH (Ar=4,4’-C6H4C(Me)2C6H4-) that, in a subsequent step, convert into [-NHRNHCO-]n and more BPA. All the PUs were characterized in the solid state by CP/MAS 13C NMR (δ(C O) = 152–161 ppm) and IR spectroscopy. The positions of ν(N-H) and ν(C O) absorptions are typical of “hydrogen-bonded ordered” bands suggesting the presence of H-bonded groups in network structures characterized by some degree of order or regularity. DSC and TGA analyses showed that the PUs are thermally stable (Td,5%: 212–270 °C) and suitable for being processed since their degradation begins at temperatures about 100 °C higher than their Tg or Tm.

Mixed oxides based on MgO⋅CeO2 were used as efficient catalysts in the aerobic oxidation of 5-hydroxymethylfurfural (5-HMF) to afford, with very high selectivity, either 2,5-diformylfuran (DFF, 99 %) or 2-formyl-5-furancarboxylic acid (FFCA, 90 %), depending on the reaction conditions. 5-Hydroxymethyl-2-furancarboxylic acid (HMFCA, 57-90 %) was formed only at low concentration of 5-HMF ( 99 %) and reusable. The use of mixed oxides allows tuning of the basicity of the catalysts, avoiding the need for external bases for efficient and selective conversion of 5-HMF and waste formation, resulting in an environmentally friendly, sustainable process.