【作者】 常世界；

【导师】 晁自胜；

【作者基本信息】 湖南大学 ， 工业催化， 2008， 硕士

【摘要】 低碳烷烃广泛存在于天然气、煤层气、石油液化气及炼厂气中,目前主要用作燃料,价格相对低廉。由低碳烷烃制备醇、醛、酸等高附加值产品日益引起人们的重视。VPO催化剂用于丁烷催化氧化制备马来酸酐工业化生产的成功更是激发起科学界研发人员对低碳烷烃转化的极大兴趣,其中化学性质相对于甲烷和乙烷比较活泼的丙烷的催化氧化尤为引人注目。丙烯酸分子中由于含有极其活泼的α,β-不饱和双键而成为理想的聚合反应单体,因而应用广泛。传统的丙烯酸生产方法(主要丙烯的两步氧化法)由于原油价格迅速上涨而受到成本上涨的严峻考验。由丙烷选择氧化制备丙烯酸由于原料成本低廉因而广泛受到人们的关注。本文主要采用固相法、溶液法和水热合成的方法,制备了Mo-V-Sb-O多元金属氧化物催化剂,采用XRD、TG-DTA、SEM、EDS、FT-IR和BET等多种技术对所制备的催化剂的结构、形貌和组成等进行了表征,并基于所制备的催化剂开展了丙烷选择性氧化制丙烯酸反应研究。主要研究结果如下:(1)固相法所制备的催化剂几乎没有活性,溶液法制备的催化剂活性很低,水热合成法所制备的催化剂活性最高。(2)水热法制备的催化剂前驱体具有正交晶相的结构,但是因其表面吸附有一定量的铵根离子和水分子,从而影响了催化剂的活性,需要进一步的焙烧处理以脱去表面所吸附的铵根离子和吸附水。(3)催化剂的焙烧条件如焙烧温度、焙烧气氛、焙烧时间均对催化剂结构及表面性质具有重要的影响,进而影响催化剂的催化效果。通过实验对焙烧条件进行了详细的考察,并得出了最佳的催化剂焙烧条件为:焙烧温度600℃、氩气保护气氛及焙烧时间2h。(4)考察了合成母液中的金属原子配比对催化效果的影响。按金属原子摩尔比为Mo:V:Sb=6:2:0.5合成的催化剂Mo6V2Sb0.5Ox具有最好的催化性能,在原料气组成为C3H8/O2/CO2/H2O=6:12:24:75(vol)、空速为2760ml/(g·h)、反应温度为390℃条件下,丙烯酸的收率可达到11.7%。(5)考察了反应的工艺条件,包括平衡气、反应温度、原料气中水蒸气的含量和空速等对水热方法制备的催化剂Mo6V2Sb0.5Ox催化效果的影响,发现平衡气的引入可以抑制丙烷的过氧化,对于提高丙烯酸的选择性有一定好处。作为过氧化产物的之一的二氧化碳作为平衡气效果相对比较好;反应温度、水蒸气的含量和空速大小对丙烷的转化率和丙烯酸的收率有显著影响。在反应温度为390℃、原料气组成为C3H8/O2/CO2/H2O=6:12:24:50(vol)时,空速为3680ml/(g·h)的反应条件下,丙烯酸的收率达到了最高值(13.8%)。更多还原

【Abstract】 Light alkanes now mainly used for fuel are cheap chemicals existed in natural gas, coal bed gas, liquid petroleum gas and petroleum refinery processes. Since light alkanes are very cheap chemicals, the conversion of light alkanes to high valued oxygenates and olefins such as corresponding alcohols, aldehydes, acids and propene has attracted much attentions in the past decades. The economic importance of this possibility and the successful manufacture of maleic anhydride by selective oxidation of n-butane over VPO catalysts have stimulated various researches, one of which is the selective oxidation of propane to acrylic acid because propane could be activated more easily than methane and ethane.Acrylic acid is an ideal monomer widely used in chemical industry due to itsα,β-unsaturated double bond. Up to now acrylic acid is commercially produced in a two-step process using propene as the raw material, which now limited by the climbing price of petroleum. Selective oxidation of propane to acrylic acid is one of promising methods to replace the commercial two-step method for producing acrylic acid.Various methods have been employed to prepare multiply metal oxides catalysts for selective oxidation of propane to acrylic acid, including solid state reaction method, solution method and hydrothermal synthesis method. some catalyst precursors and most of catalysts used in the present work were characterised by XRD, SEM, EDS,BET and FT-IR et al. Activity testing experiments were also carried out over as-prepared catalysts. Results can be listed as follows:(1) Mo-V-Sb-O catalysts prepared by hydrothermal method possess higher activity compared to those specimens prepared by other two methods.(2) Uncalcined precursors of Mo-V-Sb-O catalyst prepared by hydrothermal synthesis method show poor activity though possess orthorhombic structure for the adsorption of ammonium cation and water over their surface, so calcination is needed to drive off adsorbed specimens and to obtain catalytic activity.(3) Calcination conditions including calcination temperature, calcination atmosphere and calcination time have effective impacts over catalytic performance. An Effective Mo-V-Sb-O catalyst were obtained after as-synthesized orthorhombic-structured precousor were calcined for 2 hours in a 40ml/min flowing Argon atmosphere under 600℃. (4) Effects of molar ratio of different metal atoms in mother suspension over catalyst performance was investigated, preferred molar ratio of metal atoms is Mo:V:Sb=6:2:0.5. 28.7% of C3H8 conversion and 11.7% of acrylic acid yield was obtained when activity testing experiment was performed over as-prepared Mo6V2Sb0.5Ox catalyst under the following conditions: reaction temperature of 390℃, the space velocity of 2760ml/(g·h) and the feedstock composition(C3H8/O2/CO2/H2O volume ratio) of 6/12/24/75.(5) Effects of reaction conditions such as balance gas, reaction temperature, steam content and space velocity were investigated and discussed. Results showed that yield of acrylic acid was slightly promoted when nitrogen and carbon dioxide was introduced as balance gas respectively, which indicated that over oxidation was prevented to some extent. Acrylic acid selectivity and yield were strongly effected by reaction temperature, steam content and space velocity. The temperature of 390℃, the space velocity of 3680ml/(g·h) and the feedstock compositon (C3H8/O2/CO2/H2O volume ratio) of 6/12/24/50 were suitable for acrylic acid production. The acrylic acid yield could reach 13.8% when the optimal reaction experiment was tested.更多还原