The Study Of AuCl₃/Modified Zeolite Material Catalyzing Acetylene Hydrochlorination

The plastic product is a common material in human daily life, the polyvinyl chloride（PVC） is one of the most widespread used plastic products, vinyl chloride monomer（VCM） is generally applied to produce PVC. In China, acetylene hydrochlorination is universally used in the manufacture of vinyl chloride monomer, owing to the country’s internal characteristic of energy resource structure,wealthy coal resources and poor petroleum resource, Nowadays, the mercuric chloride supported activated carbon catalyst is mainly applied to operate acetylene hydrochlorination. Nevertheless, the active component of the toxic HgCl₂ complexes, which is the main catalyst in the manufacture of vinyl chloride monomer, arouses severe environmental pollution and damage to the health of mankind and may further contribute to the exacerbated environmental condition. Therefore, replacing the poisonous HgCl₂ with a green catalyst of acetylene hydrochlorination has caused the extensive concern. The environment friendly catalysts for acetylene hydrochlorination should then be designed.After years of exploration research, researchers discovered Au-based catalyst showed more outstanding catalytic performance in metal catalyst for acetylene hydrochlorination. Meanwhile, actived carbon as support was deeply and systematically studied, however, the problem of low mechanical strength and poor regeneration capacity still need be solved. Meanwhile, part research also focused on zeolite as a carrier for acetylene hydrochlorination, and obtained a certain progress. Hence, in the study, AuCl₃ was secleted as active component, modified zeolite was as support to promote the catalytic properties of the AuCl₃/ZSM-5. The main content of this paper is divided into the following sections:（1） The sucrose as carbon source, which can be use to modify zeolite（SBA-15）, and the carbon-modified SBA-15 as carrier, AuCl₃ as active component, the catalysts are prepared for acetylene hydrochlorination. After the catalyst activity evaluation test, catalyst using the sucrose as carbon source to modify SBA-15 shows more outstanding catalytic performance comparing to without modifying SBA-15. At last, the carbon content and the calcination temperature of carrier are optimized, the best catalyst AuCl₃/4C-10SBA-15 was obtained. Under followed conditions, temperature, 180 °C; GHSV, 150 h-1; and HCl/C₂H₂ filling volume ratio, 1.15. The acetylene conversion reach 90%, and the stability of the modified catalysts is improved, he conversion rate of acetylene by 1%AuCl₃/4C-SBA-15 decreased by 18.3% after 10 h of reaction. The catalysts were then characterized using TEM, Brunauer–Emmett–Teller method BET, FT-IR, and Raman. Results demonstrated that carbon was successfully modified onto the surface of SBA-15 catalyst. The presence of carbon layer significantly promoted electron transfer capability of SBA-15, thereby improved catalytic performance in acetylene hydrochlorination. X-ray diffraction（XRD）, BET, and thermogravimetric analysis（TGA） were applied to characterize the catalysts to determine the reason for deactivation. Results indicated that the transform of Au³⁺ to Au⁰, the agglomeration of gold particle primarily caused catalyst deactivation.（2） Based on study of SBA-15 zeolite, we further explored other zeolite. In this work, ZSM-5 type zeolite was as initial support, similarly the sucrose as carbon source was use to modify ZSM-5 zeolite, and the carbon-modified ZSM-5 as carrier, AuCl₃ as active component, 1%AuCl₃/C-ZSM-5 catalyst are prepared, obtaining optimal catalyst 1%AuCl₃/6C-ZSM-5, the catalytic performances of these catalysts for acetylene hydrochlorination were measured under the following reaction conditions: temperature, 180 °C; GHSV, 150 h-1; and HCl/C₂H₂ filling volume ratio, 1.15. The acetylene conversion reach 97.1%, the conversion rate of acetylene by 1%AuCl₃/6C-ZSM-5 was still 91.5% after 22 h of reaction. The AuCl₃/6C-ZSM-5 displayed excellent catalytic performance than that of AuCl₃/ZSM-5. The results demonstrated carbon modifying not only can improve the catalytic performance of SBA-15, but also was effective for ZSM-5 in the same way, and 1%AuCl₃/C-ZSM-5 shown better catalytic performance. The catalysts were then characterized using BET, TEM, FT-IR and Raman. Results proved that a carbon layer was successfully deposited onto the surface of ZSM-5 carrier. XRD, BET, and TGA were used to characterize the catalysts to determine the reason for inactivation. Results indicated that the conversion of Au³⁺ to Au⁰, the aggregation of gold particles, and the coke deposition primarily caused catalyst inactivation.（3） As is well known, the zeolite support shown undesirable catalytic performance for acetylene hydrochlorination, due to poor electrochemical property of zeolite. And yet in above two part works, we can know carbon species which have good electrochemical property can promote catalytic performance of zeolite during acetylene hydrochlorination. Therefore, the Polypyrrole（PPy） as carbon source and nitrogen source was use to modify ZSM-5 zeolite to promote electrochemical property of zeolite. In this work, the PPy-modified ZSM-5 as carrier, AuCl₃ as active component, 1%AuCl₃/PPy-ZSM-5 catalyst are prepared, obtaining optimal catalyst 1%AuCl₃/8PPy-ZSM-1000, under the reaction volume space velocity was 180 h-1, the conversion rate of acetylene can reach 99.1% and be still 92 % after 22 h of reaction. The materials were characterized using BET, TEM, FT-IR to determine PPy was successfully deposited onto the surface of ZSM-5 carrier. TEM, TPD, TPR, TGA were applied to analyze reason of improving catalytic performance of catalysts. The results shown that the existence of PPy significantly enhanced by affecting the adsorption of hydrogen chloride, and then inhibiting the conversion of Au³⁺ to Au⁰, the aggregation of gold particles and the coke deposition during acetylene hydrochlorination, thereby significantly promoted catalytic performance.