Removal of Arsine from Synthesis Gas Using a Copper on Carbon Adsorbent

Abstract

A variety of supported metal and metal oxide adsorbents were evaluated for removal of arsine (AsH 3 ) from synthesis gas (syngas), a mixture primarily of carbon monoxide and hydrogen. A copper(II) oxide (CuO)/ carbon adsorbent was judged to be most promising and examined more thoroughly. Exposure of the CuO/ carbon adsorbent to syngas at 750 psig resulted in only a modest increase in bed temperature. No evidence that the adsorbent acted as a methanol synthesis catalyst or promoted other syngas chemistry was observed. It was found, however, that even at modest temperatures (30-40 °C) some reduction to metallic copper (Cu) occurred. The exothermic reduction of CuO presented a significant operational concern, and use of the adsorbent required a controlled reduction to Cu/carbon prior to exposure to syngas. The arsine affinity of CuO/carbon was very high with a minimum capacity of 3.0 wt % arsenic for a syngas feed containing 420 ppbv. The reduced adsorbent, Cu/carbon, was less effective for AsH 3 removal, and at 30 °C its capacity was 1.74 wt %. Operation at 140 °C resulted in more effective AsH 3 removal with a minimum arsenic capacity of 4.31 wt % for a feed gas containing 737 ppbv AsH 3 . The kinetic limitation for AsH 3 adsorption at near ambient temperature is likely the result of slow migration of arsenic from the copper surface. At 140 °C arsenic migration is fast enough to provide a clean copper surface for adsorption. The Cu/carbon adsorbent was slightly less effective for phosphine removal than for AsH 3 . The sulfur-containing contaminants thiophene, carbonyl sulfide, and carbon disulfide were only partially removed from a syngas feed, and the adsorbent had almost no affinity for methyl chloride.

Synthesis Gas Purification

“…As discussed, some impurities are well identified such as sulfur and nitrogen compounds. However other volatile chemical species might be encountered in synthesis gases, such as for instance arsenic or selenium compounds [112,113], or metal carbonyls. Synthesis gas expected contents are for instance not well documented, as well as the impact of some impurities on a B-XTL chain, and further experiments on demonstration plant should provide relevant data.…”

Arsenic in Human History and Modern Societies

“…Synthetic gas resulting from coal gasification may be combusted as a fuel or used in the manufacturing of commercial products, such as methanol (Quinn et al, 2006). The gasification of coal mostly results in the production of carbon monoxide (CO), H 2 , N 2 , carbon dioxide (CO 2 ), water, and hydrogen sulfide (H 2 S).…”

“…Arsenic impurities may be removed from synthetic gas with various sorbents, such as: zinc ferrite (ZnFe 2 O 4 ) or, under carefully controlled temperatures, mixtures of copper(II) oxide and carbon (Quinn et al, 2006;Diaz-Somoano, López-Antón and Martínez-Tarazona, 2004). Specifically, zinc ferrite may capture As 4 vapors through the following reaction (Diaz-Somoano, López-Antón and Martínez-Tarazona, 2004): 4ZnFe 2 O 4 + As 4 + 8H 2 S + 8H 2 → 4FeAs + 4ZnS + 4FeS + 16H 2 O (5.2)…”

Kinetics and thermodynamics of the phosphine adsorption on the modified activated carbon

“…The heat value of tail gas is about 10000 kJ$m -3 [1,2], so it is meaningful to reuse the tail gases. However, the tail gases consist of 90% carbon monoxide (CO) and other hazardous gases including PH 3 , H 2 S and HF, which prevent CO being efficiently utilized [3][4][5][6]. Thus the tail gases can be used only as low value-added products, which have resulted in a great waste of energy resources.…”