Production of calcium carbide from fine biochars.

Carbon is the most abundant source of energy and chemicals on the earth. Biomass produced from photon-activated conversion of atmospheric CO2, and biomass fossils such as coal and petroleum are all carbon-rich sources. In around only one century of heavy industrial use of petroleum, this hydrocarbon source has already depleted to a point of a widespread concern over its scarcity in the decades to follow. Biocarbon, also known as biochar, can be readily produced from a vast sustainable supply of lignocellulosic biomass through pyrolysis. It is often in fine form and characterized by low mechanical strength and high activity in comparison to coal-derived chars. The ability to use biochar for the production of chemicals with high energy efficiency will largely alleviate our dependence on shrinking petroleum feedstock. Herein, we show reaction of fine biochars with fine CaO for the production of CaC2, an important starting material for production of many commodity chemicals. The process offers the potential to redirect the carbon conversion pathway. CaC2 is produced by the reaction 3C + CaO + E ! CaC2 + CO, where E 1 is the energy required for the process, about 445.6 kJmol 1 at above 2000 8C. CaC2 can be readily converted into acetylene by treatment with water: CaC2 + 2H2O!C2H2 + Ca(OH)2. Acetylene is an oxygen-free platform chemical for production of chemicals, for example, polyvinylchloride (PVC), vinyl acetate, and 1,4-butanediol. In this carbon conversion process, the main products CaC2 and then C2H2 are readily separated from other components. The current CaC2 production technology dates back to 1892 and has not changed much since then. 5] It uses an electric arc furnace, which is limited only to small-scale operations, typically less than 40 kt CaC2 per year. This process requires granular char and CaO of 5–30 mm in size and with sufficient mechanical strength, such as coal char, to allow unrestricted release of byproduct CO. Because of the low reaction rate resulting from the low surface area and poor contact between the large feed particles, high temperatures (about 2200 8C) and long reaction times (1–2 h) are usually required. These constraints inevitably result in high energy consumption (4000 kWh tCaC2 ), high production cost, and high CO2 emissions in electricity generation. [7] Autothermal heating by combustion of chars has been studied as an alternative process for CaC2 preparation. [8–10]