SEPARATIONS Activated-Carbon-Supported NaOH for Removal of HCl from Reformer Process Streams Maw-Tien Lee, † Zhen-Qin Wang, ‡ and Jen-Ray Chang* ,‡ Department of Chemical Engineering, National Chung Cheng University, Chia-Yi, Taiwan, Republic of China, and Department of Applied Chemistry, National Chiayi University, Chia-Yi, Taiwan, Republic of China An environmentally friendly method was developed to remove HCl from industrial waste gases, specifically the gas produced from a catalytic reforming process. The method uses activated- carbon-supported NaOH (NaOH/C) to treat the HCl-containing gas. A continuous-upflow fixed- bed reactor was used to test the performance of the prepared NaOH/C. Because chlorides contained in the off-gas stream of a reformer are normally less than 100 ppm, the cycle length of the NaOH/C will be expected to reach 1 year, and an accelerated aging test with a HCl concentration of 223 000 ppm was developed to shorten the test time. The accelerated aging test was confirmed to be reliable because the HCl treatment capacity of the NaOH/C for the accelerated aging test is almost the same as (within 15% deviation) that for standard tests with a gas stream containing 1000 ppm HCl. Effects of the water content on the performance of the NaOH/C were investigated by the accelerated aging test, and the results indicated that the HCl treatment capacity of the NaOH/C increases with increasing water content of the NaOH/C up to 27% and then slightly decreases. NaCl formed by the neutralization of HCl in the gas with NaOH on NaOH/C was removed by flowing low-pressure steam, and the activity of NaOH/C was rejuvenated by resoaking the activated carbon with a NaOH solution. Thus, the activated carbon of NaOH/C can be reused repeatedly. In addition, the HCl treatment capacity of the NaOH/C is about 6 times that of commercial alumina, normally used in the reformer. The developed method lends itself to industrial application. Introduction The reforming process, one of the most important processes in the petroleum industry, is used to convert paraffins and naphthenes into a high-octane-number blending component for gasoline. 1-3 Monometallic Pt on alumina catalysts and bimetallic Pt-Re or Pt-Ir on alumina catalysts are normally used in this process. The bimetallic catalyst is more stable than the Pt catalyst, allowing operation at lower pressure, which thermody- namically favors high-octane-number products; the bimetallic catalysts are preferred in commercial naph- tha reforming today. 2,3 Platinum is thought to serve as a catalytic site for hydrogenation and dehydrogenation reactions. The alumina support has to be chlorinated to provide acid sites for isomerization, cyclization, and hydrocracking reactions. Some refiners add chlorine compounds such as hydrogen chloride or dichloroethane continuously to the process to maintain the chlorine level on the catalyst, thereby maintaining the acidity of the γ-Al 2 O 3 support. 2,3 The presence of chlorine is beneficial for the reforming process, whereas chlorine in the reforming process also causes many problems. Salt such as NH 4 - Cl formed from chloride plugs up the downstream unit, resulting in an increase of the pressure drop. 4,5 Wet scrubbing has been widely used to remove acid sulfur and halide compounds from vapors. Wet scrub- bing is effective and inexpensive, but utilization of the process has to suffer from scaling inside the tower, equipment plugging, and corrosion. 6 Moreover, the wet scrubbing process removes HCl in the recycle gas of the reformer concomitantly with the addition of water to the gas stream that reduces the catalyst activity of the reforming process and causes corrosion in downstream units. A fixed bed of γ-Al 2 O 3 is generally used in the refinery to remove HCl from the gas stream. The main disad- vantages of the process are the side reactions involved during HCl removal and the problem of solid waste disposal. During the removal of HCl, aluminum chlo- ride, which is formed by the reaction of γ-Al 2 O 3 with HCl, catalytically converts olefins into a much higher molecular weight hydrocarbon. Because of this, costly steam stripping of the deposited hydrocarbon on the γ-Al 2 O 3 adsorbent is necessary before dumping the used adsorbent into a landfill. Recently, some inventions related to the removal of HCl patented by Yan disclosed that HCl can be removed from a dry gas stream by contact with nonporous solid caustic particles. 7 The caustic particles can be filled in the reactor as a fixed bed, moving bed, or fluidized bed. Among them, the fixed bed is the most preferred one. Nonporous caustic is relatively higher in mechanical strength than porous material; hence, it is less likely † National Chiayi University. ‡ National Chung Cheng University. 6166 Ind. Eng. Chem. Res. 2003, 42, 6166-6170 10.1021/ie0207055 CCC: $25.00 © 2003 American Chemical Society Published on Web 10/29/2003