Towards Sustainable Carbon Return from Waste to Industry via C2-Type Molecular Unit

Abstract

A general possibility of a sustainable cycle for carbon return to high-value-added products is discussed by turning wastes into acetylene. Pyrolyzed solid municipal wastes, pyrolyzed used cationic exchangers, and other waste carbon sources were studied in view of the design of a sustainable cycle for producing calcium carbide and acetylene. The yields of calcium carbide from carbon wastes were as high as those from industrial fossil raw materials (coke, charcoal, etc.). Conversion of carbon-containing wastes to calcium carbide provides an excellent opportunity to make acetylene, which is directly compatible with modern industry. Overall, the process returns carbon-containing wastes back to sustainable cycles to produce high-value-added products involving only C2-type molecules (calcium carbide and acetylene). Calcium carbide may be stored and transported, and on-demand acetylene generation is easy to realize. Upon incorporation into the waste processing route, calcium carbide may be an efficient carbon reservoir for quick industrial uptake.

CO2‐Free Calcium Carbide Manufacturing: Demanded Strategy in the Carbon‐Neutral Chemical Industry

“…A series of carbonaceous materials (including 13 C carbon) was previously tested in the synthesis of calcium carbide. [ 25 ] Even an excess of calcium metal (10 mol%) was not enough for complete conversion of a carbon source. [ 25 ] Thus, detailed optimization studies were necessary.…”

“…[ 25 ] Even an excess of calcium metal (10 mol%) was not enough for complete conversion of a carbon source. [ 25 ] Thus, detailed optimization studies were necessary. In vacuum, the best yields up to 69.4% were achieved using the stoichiometric ratio of calcium and carbon (Table 1, entry 5).…”

“…Concerning the presence of some minor impurities, the synthesis of CaC 2 is rather tolerant to the successful production achieved from components of different compositions. [ 25 ]…”

Calcium carbide residue – a promising hidden source of hydrogen

“…41 At the end of their life, acetylene-based products may be pyrolyzed to produce calcium carbide again, looping the carbon neutral cycle. 42 Compared to other sustainable approaches, CCR utilization for hydrogen production has crucial advantages. In fact, CCR is a waste, compared to pure water and valuable biomass.…”

Reengineering of the carbon-to-acetylene process featuring negative carbon emission

“…14 Since 1892, C 2 H 2 has been industrially produced by the calcium carbide method using coal as a carbon source. 15 In fact, inexpensive and available sources of carbon materials, including coke, 16,17 anthracite, 18,19 biochar, 20,21 pyrolysis char, 22 etc., can react with lime (CaO) to produce calcium carbide (3C + CaO = CaC 2 + CO), which is a key intermediate that reacts with water to produce acetylene (CaC 2 + H 2 O = Ca (OH) 2 + C 2 H 2 ). In the coal chemical industry, the coal-to-acetylene process is shorter and lower equipment investment is required, compared with the coal-to-olefin process led by coal gasification.…”