Preparation Of Mn-Cu-based Sorbents Loaded On γ-Al₂O₃ By Impregnation Ultrasound-assisted And Their Desulfurization Performance

Coal poly-generation technology, in which the synthesis gas is produced by the gasified coal gas and pyrolyzed coal gas, can not only realize the reasonable step utilization of raw material and energy, but also improve greatly the comprehensive utilization efficiency of the system. This is the inevitable trend for the efficiency and clean utilization of coal resources. The desulfurization from coal gas under medium temperature is a key process in this technology. To solve the problems of low desulfurization efficiency, bad thermal stability, hard regeneration, and so on, the research for a new method used to prepare a recyclable sorbent with high sulfur capacity, high thermal stability has important theoretical significance and practical value.Ultrasonic wave can generate hole and small bubbles inside liquid through the cavitation effect. The high temperature, high pressure, strong shock wave and micro jet are produces during the processes of vibration, expansion, compression and collapse of the bubbles, which is a kind special energy and hard to realize under the general conditions. The introduction of ultrasound for the preparation of sorbents will change the physical and chemical properties of sorbents, thereby improving their desulfurization ability. Selectingγ-Al2O3 as the carrier, the properties and desulfurization abilities of the copper and manganese-based sorbents prepared by ultrasonic-assisstant impregnation method and conventional impregnation method were studied in this topic. Compares the differences of sorbents prepared by these two methods, the results obtained are shown as follows:The sorbent prepared by ultrasonic-assisstant impregnation method has the higher precision of desulfurization and bigger sulfur capacity, and its desulfurization properties are obviously improved comparing to the sorbents prepared by conventional impregnation method, in which the utilization efficiency of the active component increases 33.50%. Ultrasonic-assisted impregnation can increase the load capacity of active component (increasing 12%), enlarge the specific surface area (increasing 7.42%) and pore volume (increasing 76.67%), make the particles of sorbents scattered evenly. But it has no effect on the crystal form of the active component. The active component of the manganese-based sorbents is MnO2, and mainly exists in the form of MnS2 and MnS after sulfidation reaction at 400℃in fixed-bed reactor.The active component, power and time of ultrasonic, roasting temperature, and other operating conditions during sorbents preparation would affect desulfurization ability of sorbents. The results show that the acetic acid salt is more appropriate as the raw material of active components precursor. With the increasing of ultrasonic power and time, the amount of the active component loaded on the sorbents increases, but there will be a slight agglomeration if the ultrasonic time is too long. However, ultrasonic power and time have little effect on the crystal form of the active component. Specific surface area and pore volume increase along with the increasing of ultrasonic power. Selecting acetic acid salt as the raw material of active components, the optimal condition of sorbent prepared with the best desulfurization ability are the ultrasonic power of 150 w, ultrasonic time of 1 h, calcinations temperature at 400℃During the sulfidation process of the metal oxides, H2 may change the crystal form of the active component for its strong reduction ability. The active component in Mn-based sorbents changes from MnO2 to MnO, and the active components in Mn-Cu-based sorbents change as follows:MnO?→MnO, CuO→Cu2O→Cu. The active components in Mn-Cu-based sorbents exist as the mixed crystal of MnO2, MnO, Cu2O and CuO, but Mn and Cu has no significant interaction.The desulfurization precision and desulfurization efficiency of Mn-based and Cu-based sorbents under H2 atmosphere are significantly lower to that no H2 atmosphere. This phenomenon may be caused by that the metal oxides in the composite catalyst are more easily reduced to MnO and Cu, in which Cu has the lower desulfurization ability and MnO do reverse can make the surface of sorbent partly block and sufficiently use the active components in internal surface.