CHEMICALS FROM COAL BY OXIDATIVE HYDROTHERMAL DISSOLUTION (OHD)

Oxidative Hydrothermal Dissolution (OHD) is a new coal conversion technology developed at Southern Illinois University Carbondale (SIUC) with funding support from the Illinois Clean Coal Institute. This process is an entirely novel approach to convert coal directly into chemicals using only water and oxygen. The process does not go through the usual gasification (syngas) route or use expensive or proprietary solvents or catalysts. It is somewhat analogous to accelerated weathering. OHD works by reaction of the coal with small amounts of oxygen in high temperature, high pressure, liquid water. This breaks up the coal’s structure, resulting in the generation of low molecular weight, water soluble products. Petrographic analysis reveals etched particle surfaces and pitted edges. Complete conversion of the coal is readily achievable with 70-90% recovery of the original carbon as water soluble products. Most silicate minerals present in the coal pass through the process essentially unaltered. Raw OHD product is an aqueous solution (not a colloid or suspension) consisting of a mixture of low molecular weight aromatic and aliphatic acids and related derivatives that could potentially supplement or replace some petroleum–derived products as chemical feed stocks. Raw OHD product can be pumped and refined using conventional liquid processing technology. Since the process uses only water and oxygen, it is inherently environmentally friendly. It produces little CO₂, and no NOx or SOx or other toxic emissions. Harmful elements like mercury, arsenic etc., are not released to the environment but either remain associated with their parent minerals or are retained in the product solution and can be processed and captured by conventional waste water treatment strategies.