Catalytic Gasification of Coal Using Eutectic Salts: Recovery, Regeneration, and Recycle of Spent Eutectic Catalysts

Abstract

Catalyst recovery studies were conducted for gasified chars produced from steam gasification of Illinois #6 coal catalyzed with two different catalyst systems. A ternary (43.5 mol% Li 2 CO 3 -31.5 mol% Na 2 CO 3 -25 mol% K 2 CO 3 ) and a binary (29 mol% Na 2 CO 3 -71 mol% K 2 CO 3 ) eutectic catalyst system were used for gasifying coal. Various extraction schemes, such as water extraction, H 2 SO 4 extraction, and acetic acid extraction, were evaluated with respect to their extraction efficiencies. Effects of major process variables, such as solvent-to-char ratio, mixing time, temperature, and concentration, on the extraction efficiency were evaluated. A process schematic for the entire catalyst recovery, regeneration, and recycle scheme was developed and the preliminary process economics were determined based on these extraction schemes. H 2 SO 4 extraction was found to be the most desirable. It also turned out to be more attractive than a once-through throwaway system.

Catalysis in Coal and Carbon Gasification

“…In this context, rationalization of the behavior of the practically attractive ''composite'' catalysts [47,48] poses special challenges. Thus, for example, the reduced melting points of eutectic phases are thought to be responsible for the higher catalytic activity of binary and ternary alkali metal halides, carbonates and sulfates [49], because they ''facilitate contact between the catalyst and the carbonaceous substrate''.…”

Mechanism of Ca Additive Acting as a Deterrent to Na2CO3 Deactivation during Catalytic Coal Gasification

“…Gasification, as one of the key technologies for the clean utilization of coal, has been widely applied in the synthesis of ammonia, methanol, and coal-based synthetic natural gas (SNG) and in Fischer–Tropsch synthesis. , Catalytic gasification, which is considered as the next-generation gasification technology, has been paid more and more attention due to its low gasification temperature, high energy efficiency, and high selectivity to some desired gases. − The catalysts used in catalytic gasification are usually alkali metals, alkaline earth metals, and transition metals, although alkali metals show superior catalytic performance. − However, alkali metals are easy to react with Si and Al minerals in coal to form deactivated alkali metals, which have poor catalytic performance. − Meanwhile, the deactivated alkali metals are usually water-undissolved and cause low alkali recovery. − Both the deactivation and the lower alkali recovery increase the cost of catalytic gasification, and thus alkali deactivation has become one of the key technical bottlenecks for the large-scale application of catalytic gasification. Therefore, deactivation behaviors and efforts to alleviate the deactivation of alkali metals have been intensively focused on. − …”

Catalytic Gasification Activity of Na2CO3 and Comparison with K2CO3 for a High-Aluminum Coal Char

“…However, most existing gasification technologies have several disadvantages, such as severe gasification conditions, high oxygen consumption, high capital investment, and unattractive economics, which impede the application of novel coal gasification technologies. With the growing demand for natural gas, much attention has been paid to catalytic coal gasification − because of its extraordinary advantages: (I) catalytic gasification can strikingly lower the reaction temperature, so that the investment cost of gasification would be lowered; (II) it can remarkably enhance the gasification reaction rate, thus elevating the gasification efficiency; (III) moreover, catalytic gasification favors the production of methane, which is regarded as one of the desirable methods to produce synthetic or substitute natural gas (SNG) . As a result, catalytic gasification is a promising coal gasification technology.…”

“…With regard to recovery of the catalyst used in catalytic gasification, a few researchers have used various extraction methods to improve its recovery. Among the different extraction processes reported by Sheth et al, H 2 SO 4 extraction is the best method for recovery of the gasification catalyst. Unlike the solvent extraction methods, Kim et al reclaimed the catalyst from the catalytic gasification residue on the basis of size and ferromagnetism.…”