| Hydrogen sulfide is a colorless, highly toxic, corrosive gas, its chemical properties is unstable and harmful to animals plants and buildings, destroying the ecological environment and human health, which is second only to cyanide and be death easily. It mainly comes from industrial production, including the processing and using of natural gas, petroleum refining, coal gasification, sewage treatment, biogas fermentation, chemical production process and so on. At present, domestic and foreign methods for treating hydrogen sulfide are absorption, adsorption, biological method mostly, however there are some shortcomings and insufficiency, such as desulfurization of low accuracy; low activity; the sulfur capacity of small; difficult regeneration; high energy consumption; short cycle, etc, therefore, the development and utilization of new materials and new technology has become the top priority.Hydrotalcite-like compounds are a kind of layered double compounds with large of application, mainly including the hydrotalcite and hydrotalcite-like compounds. Hydrotalcite-like compounds with special structure and physical and chemical properties, such as the anion exchange properties, adsorption properties, catalytic properties, has been widely applied in many fields of catalyst, catalyst carrier, sewage treatment agent, medicine carrier, which is now also widely used to control environment pollution in the exhaust gas. Hydrotalcite-like compounds have not only excellent voids and the characteristics of the specific surface, but also has the anion exchange ability, has potential ability for acidic gas hydrogen sulfide selectivity adsorption, which can be used as adsorbent and catalyst carrier for dealing with hydrogen sulfide waste gas.This paper cheifly studies the Mg-Al hydrotalcite on hydrogen sulfide adsorption performance and mechanism.The supersaturation coprecipitation for preparing adsorbent Mg-Al hydrotalcite, dynamic adsorption experiments using fixed bed reactor under ordinary pressure, using iodometry method for determining the concentration of import and export of hydrogen sulfide, to calculate the adsorption capacity by the breakthrough curve, so then the adsorption performance and mechanism of hydrogen sulfide for in-depth research. Mainly studied the following two aspects of content:(1)Investigating the adsorption isotherm and adsorption thermodynamic at Mg-Al hydrotalcite on hydrogen sulfide under20℃,40℃,60℃and80℃temperature conditions.(2)Adsorbent is studied through experiment of the preparation conditions(pH, crystallization temperature), reaction temperature, and H2O on the influence of the hydrogen sulfide adsorption performance, selecting the best adsorbent.The research results show that:(1) The adsorption capacity increases along with the increase of hydrogen sulfide concentration at the equal temperature, in the same concentration, the adsorption capacity increases with the increase of temperature. The adsorption capacity increases as the temperature increased at the same concentration;(2) The unmodified hydrotalcite under the condition of no water has high adsorption efficiency; The optimum reaction temperature was80℃; synthesis of pH is12, the crystallization temperature of80℃is the optimal conditions for preparation.(3) Experiments of adsorption equilibrium data is coincident with the Freundlich equation fitting results under20℃,40℃,60℃and80℃temperature conditions. The isosteric heat of adsorption of hydrogen sulfide on Mg-Al Hydrotalcite has decrease with increasing adsorption amount. The isosteric heat of adsorption is22.9292-34.1747kJ/mol, and at the low temperature (20℃-40℃), the hydrogen sulfide adsorption process is physical adsorption, the isosteric heat of adsorption is160.0137-210.9827kJ/mol, and at the high temperature (60℃-80℃), the hydrogen sulfide adsorption process is dominated by chemical adsorption, high temperature is beneficial to the adsorption Mg-Al hydrotalcite on hydrogen sulfide.(4) By XRD characterization of adsorption mechanism is analyzed, further confirmed that the low temperature is mainly physical adsorption, adsorbent appearance doesn’t change, however, H2S in the surface of hydrogen sulfide adsorption process is chemical adsorption, a part of H2S was oxidized to S or Ss or a mixture of the both; and the others are absorbed into the hydrotalcite internal oxidation of SO42-, this is mainly due to the interlayer anion exchange characteristic of hydrotalcite. |
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