摘要
以不同粒径的Y分子筛为载体,过量浸渍Cu(NO_3)_2溶液制备CuY催化剂,并采用XRD、H_2-TPR、NH_3-TPD和TEM等技术对催化剂表面微观结构进行表征,考察了其在甲醇气相氧化羰基化反应中的催化性能。结果表明,Y分子筛的粒径减小利于阳离子位点暴露,促进Cu^(2+)与载体间的离子交换,进而实现Cu物种的高度分散,且交换的Cu^(2+)更多的落位在载体表层笼结构中,经高温活化形成更多催化活性中心Cu^+;同时,随载体粒径减小,孔道更短,与外界相通的孔口数更多,利于反应分子与催化剂活性中心接触,使甲醇的转化率随着载体粒径的减小而显著提高。当Y分子筛粒径由3.0μm减小为0.3μm时,CuY催化剂的甲醇转化率由1.32%增加到5.60%。然而,Y分子筛粒径减小时,催化剂表面上可接触的酸性位点增加,导致甲醇氧化羰基化目标产物DMC的选择性明显降低,粒径为3.0μm的Y分子筛负载的铜催化剂DMC选择性最高,可达87.96%。总体来说,当Y分子筛粒径从3.0μm降为0.3μm时,DMC时空收率从65.83mg/(g·h)增加到165.38mg/(g·h)。
CuY catalysts were prepared from Cu （NO32 solution and Y molecular sieves with different crystal sizes by excessive impregnation method, and characterized by XRD, H2-TPR, NH3-TPD and TEM. The effect of Y molecular sieve crystal size on CuY catalyst in the oxidative carbonylation of methanol was investigated. Results showed that the reduction of Y molecular sieve crystal size could increase the cationic sites exposed on the surface of support, which could promote the exchange of ions between Cu2＋ and the cations, resuhng in the high dispersion of Cu species and more Cu2＋ exchanged being located in the surface cages of support, which were translated to Cu＋ as catalytic active sites by calcination. The support possessed short and regular pore structure and more pore windows interlinked to outsides due to its small crystal size, which facilitated reactant molecules diffusing and reaching the active sites, resulting in the conversion of methanol increasing remarkably with decreasing the crystal size of support. When the crystal size decreased from 3.0μm to 0.3μm, the conversion of methanol increased from 1.32% to 5.6%, but the catalyst acid sites, which are easy to contact the reactant, increased with the decrease of crystal size, which resulted in the change of product distribution, lowing DMC selectivity. Although, the highest DMC selectivity of 87.96% were obtained over the catalyst prepared from the support with the crystal size of 3.0μm, the space-time yield of DMC increased from 65.83mg/（g·h to 165.38mg/（g·h when the crystal size of support deccresed from 3.0μm to 0.3μm.
出处
《天然气化工—C1化学与化工》
CAS
CSCD
北大核心
2017年第1期36-42,共7页
Natural Gas Chemical Industry
基金
国家自然科学基金(No.21276169,U1510203)
关键词
氧化羰基化
CuY催化剂
粒径
Y分子筛
扩散
oxidative carbonylation
CuY catalyst
Y molecular sieve
crystal size
diffusion
