Oxidative coupling of methane (OCM) has been studied over a mixed catalyst constituted by Na2WO4-Mn/SiO2 (W) and BaCl2-TiO2-SnO2 (B). The effects of reaction temperature, gas hourly space velocity (GHSV) and CH4/O-2 ratio on catalytic performance were systematic investigated. Compared with the single component counterpart, the results indicated that ethylene yield was significantly enhanced over the mixed catalysts. When the BaCl2-TiO2-SnO2/Na2WO4-Mn/SiO2 (B/W) ratio was controlled at 1/5 (v/v), the ethylene yield reached 22.2 %, which was 7.1 %, 2.1 % higher than the single Na2WO4-Mn-SiO2, BaCl2-TiO2-SnO2 catalyst, respectively. Besides, the ethylene yield was higher than 20 % over the mixed catalyst in wide reaction condition range.

The performance of MCl2-TiO2-SnO2(M=Mg,Ca,Sr,Ba) catalysts in oxidative coupling of methane reaction has been investigated.The catalysts were prepared by grinding method,and characterized by BET,XRD,XPS and CO2-TPD,respectively.The distribution of surface basicity strength is varied with the changing of M2+ in the catalysts.The more weak basic sites on catalyst surface are crucial for the activation of methane;while the strong basic sites bring the loss of active sites on catalyst surface.In addition,although the basic site can prompt the conversion of methane,it can also bring the deep oxidative of ethylene.The lattice oxygen is selective to ethy-lene product generation,and the selectivity to ethylene increase with increasing relative concentration of surface lattice oxygen.

A novel BaCl2–TiO2–SnO2 catalyst was prepared and studied for the oxidative dehydrogenation of ethane (ODE). Slight changes in textual properties and crystal structures of the catalyst were observed after ODE reaction. Nonetheless, both Ba2+ and Cl− ions were found to segregate on catalyst surface during the reaction. The vital and positive effects of Cl− ions in the catalyst have been demonstrated by control experiments with catalyst free of Cl− ions. The BaCl2–TiO2–SnO2 catalyst show good activity and selectivity in ODE reaction, making it an alternative for ethylene synthesis using a low-cost feedstock such as ethane.

The performance of BaCl2-TiO2-SnO2 composite catalysts in oxidative coupling of methane reaction has been investigated. A series of BaCl2-TiO2, BaCl2-SnO2, TiO2-SnO2, and BaCl2-TiO2-SnO2 catalysts were prepared, and characterized by BET, XRD, XPS, CO2-TPD and H2-TPR, respectively. The synergistic effect among BaCl2, SnO2 and TiO2 compositions enhances the catalytic performance. The best C2 selectivity and ethylene yield are obtained on the catalyst with the equal molar amount of the three compositions (BaCl2: TiO2: SnO2 molar ratio of 1:1:1). The optimal reaction conditions are as follows: 800°C, 44 mL-min−1 for methane, 22 mL-min−1 for oxygen and a space velocity of 5000 mL-h−1-g−1, and the C2H4 yield over the catalyst is 20.1% with the CH4 conversion of 43.8% and C2 selectivity of 53.3%.

The study of scale up for the oxidative coupling of methane (OCM) has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na2WO4-1.9wt% Mn/SiO2 (W-Mn/SiO2) catalyst. The effects of reaction conditions were investigated in detail. The results showed that, with increasing reaction temperature, the gas-phase reaction was enhanced and a significant amount of methane was converted into COx; with the CH4/O2 molar ratio of 5, the highest C2 (ethylene and ethane) yield of 25% was achieved; the presence of steam (as diluent) had a positive effect on the C2 selectivity and yield. Under lower methane gaseous hourly space velocity (GHSV), higher selectivity and yield of C2 were obtained as the result of the decrease of released heat energy. In 100 h reaction time, the C2 selectivity of 66%–61% and C2 yield of 24.2%–25.4% were achieved by a single pass without any significant loss in catalytic performance.

Effects of ethane, CO and CO2 contents in feed gas on activity of Na2WO4 - Mn/SiO2 catalyst in oxidative coupling of methane (OCM) were investigated. OCM was carried out in a two -stage fixed bed micro - reactor. Increase of ethane content in feed gas inhibits methane conversion and promotes formation of CO to a certain extent. Increase of CO content in feed gas leads to production of CO2, but inhibits production of CO. Change of CO2 content in feed gas has little effect on activity of catalyst. The two - stage reactor is an effective measure to increase yield of ethylene. Conversion of methane, selectivity to C2 components and yield of ethylene can reach 60. 5%, 62. 8% and 33. 1%, respectively.

A 5wt%Na2WO4–2wt%Mn/SiC monolithic foam catalyst was applied in the oxidative coupling of methane. This catalyst showed the same high activity as the conventional 5wt%Na2WO4–2wt%Mn/SiO2 catalyst with no dilution gas and a temperature of 850°C (>24% methane conversion, 51% C2 (ethylene and ethane) selectivity), but also an excellent heat transfer feature as the significant hot spots did not occur in the catalyst bed. The SiC- and SiO2-supported catalysts were characterized by BET, SEM, XRD and XPS, respectively.

Na2WO4-Mn/SiO2 is known as an excellent catalyst for oxidative coupling of methane. Its catalytic performance in thermal cracking dehydrogenation and oxidative dehydrogenation of ethane were investigated. The catalyst can accelerate thermal cracking dehydrogenation of ethane when temperature is higher than 800°C, and ethane can be oxidized simultaneously into ethylene in presence of CO2. In existence of oxygen at 660°C, ethane conversion and ethylene selectivity can reach 63.3% and 68.2%, respectively. High volume ratio of ethane to oxygen is strongly favorable to ethylene selectivity. Increase of gas hourly space velocity can inhibit generation of CO2. Introducing of diluent (steam) can partially inhibit generation of CO2, and its effect on selectivity of CO and conversion of ethane are unobvious.

Under microwave irradiation, the effects of reaction bed temperature, O2/ toluene ratio, total space velocity (SV) of feed gas and V2O5 loading were investigated in order to optimize the reaction conditions over V2O5/TiO2 for the selective oxidation of toluene. It was suggested that when the reaction bed temperature was 250°C, O2/toluene molar ratio was 6, the total SV was 10 000 h-1, and the V2O5 loading was 8%, the catalytic activity of V2O5/TiO2 was the highest with 20% yield of benzoic acid. Specially, in the microwave catalytic process the modification of V2O5/TiO2 with MoO3 or Ag2O, which had no or negative influence on the titled reaction in the conventional case, greatly promoted the selective oxidation of toluene leading to further improvement in the catalyst performance in terms of benzoic acid yield (41%). Compared with the conventional catalytic process, the effects of microwave electromagnetic field on the catalysts were also discussed tentatively.

Aluminas pretreated with pure water (pseudo-hydrothermal treatment) and very dilute basic aqueous solutions were used as catalysts for CO hydrogenation. Pseudo-hydrothermal treatment results in an apparent enhancement of ethylene selectivity at elevated temperature (> 673 K). The active sites seem to be coordinatively unsaturated metal and oxygen counterions (Lewis acid and base pair), which are very probably located on the most external surface of the alumina and can be coordinatively saturated by calcination in air. The precursors of the active sites probably originate from a very thin layer of boehmite beyond XRD detecting ability. They can be generated by both pseudo-hydrothermal treatment and dilute basic aqueous solution treatment of alumina.

CO hydrogenation was studied over various alumina catalysts, untreated, pre-treated with sodium acetate (NaOAC) and calcined at 773 K after treatment. The catalysts were characterized by means of XRD and IR spectroscopy after pyridine adsorption. An apparent increase of ethylene selectivity over NaOAC pre-treated catalyst was observed. Both CO conversion and ethylene selectivity depended on the temperature of CO hydrogenation and a new γ-Al2O3 layer formed by surface boehmite transformation at elevated temperature on the original alumina surface. Several probe molecules, including HC1, NH3 and pyridine, were used to detect the active sites for CO hydrogenation. There are two kinds of active sites (e.g. Lewis acidic and basic sites) which seem to be involved in the heterolytic dissociation of hydrogen to form a hydroxyl. Thus, the hydroxyl possibly plays a very important role in the formation of formyl, which may be the intermediate of the methoxide, and the methoxide seems to be the intermediate for hydrocarbons.

> The study of Fischer-Tropsch synthesis has been processed for about 70 years. In recent years, lots of reports appear, which are focused on hydrogenation of carbon monoxide to olefins （C 2 = -C 4 = ）, especially over Fe-Mn catalysts. Although all of the work aims at producing ethylene, the selectivity to ethylene among the produced hydrocarbons is not high

由合成气制烃类的研究可追溯到70多年前,近年来用铁-锰系催化剂一氧化碳加氢合成低碳烯烃的工作较多,也取得了长足的进展。这些工作虽然以合成乙烯为主要目的,但在一氧化碳转化率较高时,对乙烯的选择性尚嫌不够,所以实际所得的为低碳混合烯烃（C 2 = ～C 4 = ）及符合Schulz-Flory分布规律的烃类产物分布。一般情况混合烯烃中