Ni基催化剂上的乙烷部分氧化制合成气

第20卷第2期催化学报1999年3月Vol. 20 No. 2Chinese Journal of CatalysisMarch 1999PARTIAL OXIDATION OF ETHANE TO SYNGASOVER NICKEL-BASED CATALYSTSLiu Shenglin, Xiong Guoxing, Sheng Shishan, Yang Weishen, Xu longyaState Key Laboratory of Catalysis, Dalian Institute of Chemical PhysicsThe Chinese Academy of Sciences, Dalian 116023)Key words ethane, partial oxidation, syngas, nickel-based catalystClassification No 0643There is abundant supply of light alkanes and relatively few routes of convertingthem to more valuable products. Although CHa predominates in natural gas, it alsocontains C2H6, C3Ha and C4H,o( from 5% to 30%), and with C2H as the mostabundant secondary component1. Partial oxidation of methane to syngas(CH+0.502-*CO+ 2H2) over nickel-based catalysts has received intensive attention( 2Jand much research has been devoted to conversion of ethane to ethylene(33. Ethylenehas been shown to be formed from ethane by thermal dehydrogenation(C2H,C2H4+H2)and oxidative dehydrogenation(C2H+0.502-C2H4+H2O).Theseprocesses are operated under severely fuel-rich conditions. The carbon-deposition aneconsequent deactivation of the catalysts are major problems, which leads to poor conversion of the above mentioned reactions. As an alternative strategy for the elaboration of ethane, little work on the partial oxidation of ethane(poe)to syngas overnickel-based catalysts has been reported. Provided it could be produced from C2H6with high selectivity and high conversion over nickel-based catalysts, syngas could bedirectly obtained from natural gas including CH4 and C2h with high selectivity andconversion. This may lead to better utilization of the light fractions from natural gasand refineries. In the present paper, poe to syngas over nickel-based catalysts wasinvestigatedCatalysts were prepared by impregnation method, and tested in a fixed-bedmicroreactor under atmospheric pressure. The reaction products were analyzed by gcwith a tCd detector. TG test was performed on a P-E TGs-2 instrument. The performance of NiO/y-AL2O3, NiO/MgO and NiO/Sio, for poe to syngas reaction wasmeasured. The results were listed in Table 1. Ethane and oxygen were almost converted completely(no shown), H2 and CO selecti中国煤化 T eaction conctions were as follows: NiO/y-Al2O3> NiO/MgOCNMHGC2H4 was produced over NiO/SiO, catalyst. The results indicated that NiU/y-AL2U3 catalyst is theReceived: 1998-12-14. First author: Liu Shenglin, male, born in 1969, PhD studentCorresponding author: Xiong Guoxing. Tel: (0411)4671991-731催化学报20卷best one among the three for poe to syngasIn order to study the effects of alkali and rare-earth metals on the performance ofNiO/y-AL2 O3 catalyst for POE reaction, a series of ANiBO/y-AL2O3(A=Li, Na, KB= La, Sm, Ce, y) catalysts with the same nickel content have been developed(Table 2). The NiO/y-Al2O3 modified by alkali metals and rare-earth metals, andunpromoted NiO/y-AL2O3 all had excellent performance for the reaction. Under theconditions of T= 1 123 K, V(O,): V(C2H): V(He)=1 061: 4 and Qv(c2h)=10ml/min, ethane and oxygen were almost converted completely, Co and H2 selectivitykept about 94 %and 98%, respectively The results demonstrated that the promotersof alkali and rare-earth metals did not influence the reactivity and selectivity of Poereaction over NiO/y-Al2O3Table 1 Performance of different catalystsTable 2 Performance of different catalystsfor poe reactionfor POE reactionCatalyst S(CO)/% S(H2)/% S(CH4)/% S(C2H4)/S(0o)/%S(H2)/%S(cH4)/NiO/y-AL, O3 89.096.80.2Al2O394.298.30.6NiO/MgO 87.393.12.0LiniLao/y-A2O394.198.60.557.4v(2):V(C2H6):v(He)=1.l5:1:4,qy(C2H)=40KNiLaO/y-Al,O3 94.0 98ml/min, m( Cat)=50 mg, T=1 123 KLiNiCeO/y-AL, 94.897.60.7LiNiYO/y-AhO94.797.9The introduction of alkali metal and LiNiSmO/y-Al,0, 95.1rare-earth metal improved the ability of v(o,): v(CH): V(He)=1.06: 1: 4, 9v(CaHs)=10carbon-deposition resistance, although it ml/min, m( Cat )=50 mg. T=1123Kdid not influence the performance of Nio/y-Al2O3 for POE reaction. It is well knownthat the acidity of catalyst surface favors carbon-deposition and the basicity of catalystsurface prevents carbon-deposition. So, the adoption of alkali and rare-earth metalsshould be beneficial to the prevention of carbon-deposition on catalyst surface. After a5 h stream under the conditions of T=1 123 K, V(ch):V(O2):V(He)=1. 15:14 and qv(C2H6)=10 ml/min, the catalysts were then investigated by TG techniqueThe results indicated that the amounts of carbon-deposition on LilaNiO/y-Al2O3 andLaNiO/y-AL2O3 were only 0. 39% and 0.92% in mass fraction, respectively, butthat on NiO/y-AL,O is about 2. 48% in mass fraction It is shown that the introduction of alkali and rare-earth metals can obviously suppress the carbon-deposition onnickel-based catalyst surfaceReferencesKolts J H, Guillory J P. EP 0 205 765. 19862 Ashcroft A T, Cheetham A K, Foord JS et al. Nature(1中国煤化工3193 Huff M, Schmidt L D. J Phys Chem, 1993, 97(45): 1181HCNMHG(Ed WGZh)