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Zhang X.,CAS Research Center for Eco Environmental Sciences | Wang Z.,CAS Research Center for Eco Environmental Sciences | Wang Z.,Tsinghua University | Tang Y.,CAS Research Center for Eco Environmental Sciences | And 5 more authors.
Catalysis Science and Technology | Year: 2015

A series of Mg2AlxFe1-x LDH compounds was synthesized by a one-step method. The structural and chemical properties were studied by various methods and the derived oxides were tested for H2S selective oxidation. It was observed that the iron species existed mainly in the form of isolated Fe3+ species, α-Fe2O3, γ-Fe2O3 and Fe3O4. Moreover, the nature of the iron oxides was varied with the rise in the iron content. Significantly, the catalysts exhibited high catalytic activity and reasonable durability at a relatively lower temperature and higher GHSV. The catalysts obeyed the step-wise mechanism for H2S selective catalytic oxidation. And the chemically adsorbed oxygen on the oxygen vacancies participated in the H2S selective oxidation reaction and played a key role in the H2S selective oxidation into elemental sulfur. The catalyst deactivation was due mainly to the deposit of elemental sulfur. Additionally, the small amount of the formed less active Fe2(SO4)3 species also led to catalyst deactivation. © The Royal Society of Chemistry. Source


Zhang J.,Xian Shiyou University | Meng X.-J.,Xian Shiyou University | Meng X.-J.,Shandong Sunway Petrochemical Engineering Share Co. | Chen G.,Xian Shiyou University | Hu Q.,Yang Zhou Runda Oilfield Chemicals Co.
Huaxue Gongcheng/Chemical Engineering (China) | Year: 2013

The gas-liquid cyclone separator simulator was designed and applied in the drilling fluid circular flow simulator. The separator is a cone and cylinder integrated apparatus with a downward inclined inlet. The gas-liquid separation in the separator is dependent on rotational flow. The separation efficiency and process of the gas-liquid cyclone separator were studied by this simulation experiment under laboratory conditions. The influences of the fluid flow rate, gas flow rate, external pressure and fluid viscosity on the separation efficiency were researched. The relation between different gas-liquid separation condition and the gas-liquid separation efficiency was obtained and the variation of separation efficiency was also analyzed. The results show that the separation efficiency can reach 90% in the simulation condition. Source


Zhang X.,CAS Research Center for Eco Environmental Sciences | Tang Y.,CAS Research Center for Eco Environmental Sciences | Qu S.,Shandong Sunway Petrochemical Engineering Share Co. | Da J.,Sinopec | Hao Z.,CAS Research Center for Eco Environmental Sciences
ACS Catalysis | Year: 2015

The most widely used catalysts and processes for H2S-selective catalytic oxidation are overviewed in this review. Two kinds of catalysts have been investigated intensively: carbon-based catalysts (active carbon catalyst, carbon nanotube catalyst, and carbon nanofiber catalyst), metal oxide-based catalysts (metal oxide catalyst, oxide-supported catalyst, and clay-supported catalyst). Among them, carbon-based catalysts are utilized mainly in discontinuous processes at relatively low temperatures, whereas metal oxide catalysts are the most widely used in practice. However, the reaction temperature is relatively high. Fortunately, a MgAlVO catalyst derived from LDH materials and intercalated clay-supported catalysts exhibit excellent catalytic activities at relatively lower temperatures. According to various studies, the catalytic behaviors mainly obey the Mars-van Krevelen mechanism; however, the catalyst deactivation mechanism differs, depending on the catalyst. In practice, the mobil direct oxidation process (MODOP), super-Claus and Euro-Claus processes were developed for H2S-selective catalytic oxidation. Nevertheless, MODOP has to proceed under water-free conditions. The super-Claus process can operate in up to 30% water content. The Euro-Claus process is a modified version of the super-Claus process, which was developed to eliminate recovery losses of escaped SO2. © 2014 American Chemical Society. Source


Zhang X.,CAS Research Center for Eco Environmental Sciences | Tang Y.,CAS Research Center for Eco Environmental Sciences | Qiao N.,CAS Research Center for Eco Environmental Sciences | Li Y.,CAS Research Center for Eco Environmental Sciences | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2015

A series of Mg2Al-V10O28-LDH (named V-LDH) were synthesized using ion-exchange method, and the derived oxides were investigated for H2S selective oxidation. The physicochemical properties of the catalysts were assessed by various methods. It was observed that vanadium species existed mainly in the form of isolated V5+ in distorted [VO4], Mg3V2O8, and Mg2V2O7. Moreover, there was a large amount of V4+ species (>25%), mainly formed with vanadyl bonds. Significantly, the catalysts exhibited excellent catalytic performances at relatively low reaction temperatures (100-200°C). Furthermore, the catalyst containing 10.6wt% vanadium (8V-LDO) was highly durable at a relatively low temperature (160°C) and a high gas hourly space velocity (GHSV, 24,000h-1), which can proceed consecutively for 100h without notable deactivation. In the reaction process, the gradually produced sulfate species reacted with V4+ species to form less active VOSO4 species, which improved the redox property of V5+. The catalysts obeyed a step-wise mechanism for H2S selective catalytic oxidation. The excellent durability can be ascribed to the fact that the content of moderate basic sites was kept and the redox property of V5+ was improved. © 2015 Elsevier B.V. Source


Zhang X.,CAS Research Center for Eco Environmental Sciences | Wang Z.,CAS Research Center for Eco Environmental Sciences | Qiao N.,CAS Research Center for Eco Environmental Sciences | Qu S.,Shandong Sunway Petrochemical Engineering Share Co. | Hao Z.,CAS Research Center for Eco Environmental Sciences
ACS Catalysis | Year: 2014

A series of Mg2AlxV1-x-LDH (LDH = layered double hydroxide) was synthesized by using a facile method, and well-mixed derived oxides were obtained after calcinations. These catalysts were further tested for H2S selective oxidation. Meanwhile, the physicochemical properties of the catalysts were investigated by various methods. It was observed that vanadium species existed mainly in the form of isolated V 5+ in distorted [VO4],Mg3V2O 8 and VO2+. Significantly, these catalysts exhibited high catalytic activities in a relatively lower range of reaction temperatures (100-200 °C) as a result of the well-dispersed vanadium species and excellent moderate basicity property. A catalytic reaction mechanism was proposed as follows: H2S was first adsorbed on the Mg-O-Mg band of MgO (moderate basic sites), forming S2- and H2O, then the S2- was oxidized to Sn by V5+, simultaneously, forming oxygen vacancies and V4+. Finally, V4+ was oxidized to V5+ by O2, and O2- was incorporated into oxygen vacancies. In addition, the catalyst deactivation was mainly due to the decrease in moderate basic sites. Moreover, the formed less-active VOSO4 also contributed to the catalyst deactivation. © 2014 American Chemical Society. Source

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