催化学报 ›› 2018, Vol. 39 ›› Issue (11): 1762-1769.DOI: 10.1016/S1872-2067(18)63145-6

• 论文 • 上一篇    下一篇

HZSM-35分子筛酸性质对甲缩醛和乙酸甲酯羟醛缩合反应的影响

马占玲a,b,c, 马现刚a, 倪友明a, 刘红超a, 朱文良a, 郭新闻b, 刘中民a   

  1. a 中国科学院大连化学物理研究所甲醇制烯烃国家工程实验室, 辽宁大连 116023;
    b 大连理工大学化工与环境生命学部化工学院精细化工国家重点实验室, 辽宁大连 116024;
    c 中国科学院大学, 北京 100049
  • 收稿日期:2018-06-21 修回日期:2018-07-16 出版日期:2018-11-18 发布日期:2018-09-01
  • 通讯作者: 朱文良, 刘中民

HZSM-35 zeolite catalyzed aldol condensation reaction to prepare acrylic acid and its ester:Effect of its acidic property

Zhanling Maa,b,c, Xiangang Maa, Youming Nia, Hongchao Liua, Wenliang Zhua, Xinwen Guob, Zhongmin Liua   

  1. a National Engineering Laboratory for Methanol to Olefins, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China;
    b State Key Laboratory of Fine Chemicals, PSU-DUT Joint center for Energy Research, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China;
    c University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2018-06-21 Revised:2018-07-16 Online:2018-11-18 Published:2018-09-01
  • Contact: 10.1016/S1872-2067(18)63145-6

摘要:

丙烯酸及其酯是重要的化工原料,广泛应用于涂料、粘结剂、纤维等领域,目前工业上常采用丙烯两段氧化法进行制备,但该法以石油基原料丙烯为源头,采用V/Mo/Bi等金属催化剂,不符合可持续发展理念,且存在环境污染及氧气下产物易过度氧化等问题.如何高效、安全、大规模工业化制备丙烯酸及其酯是研究者追求的目标.以乙酸甲酯(Mac)和甲醛为原料,通过羟醛缩合一步制备丙烯酸及其酯是一条完全不同于丙烯氧化法的合成路径,原料均可由煤基甲醇得到,符合我国“富煤、贫油、少气”基本能源结构,且该方法碳原子利用率为100%,副产物仅为水,属于绿色环保合成路径.
本文以甲缩醛(DMM)为甲醛源,创新性地采用固体硅铝分子筛为酸性催化剂,催化DMM和MAc发生羟醛缩合反应来制备丙烯酸.硅铝分子筛具有较高的活性,可高效地催化羟醛缩合反应,且具有很好的再生性能,即使催化剂寿命较短,也可采用流化床或移动床等反应器进行工业化,因此具有良好的工业化前景.硅铝分子筛中常含有Brönsted酸和Lewis酸,为试图说明羟醛缩合反应的真正活性位点,我们以羟醛缩合反应性能最佳的HZSM-35分子筛为研究目标.
首先,利用红外研究HZSM-35分子筛的酸性质.发现分子筛中桥羟基提供Brönsted酸,外骨架铝物种提供Lewis酸.通过对桥羟基红外峰一阶求导,发现其对称性较差,表明Brönsted酸在HZSM-35分子筛孔道中分布不均匀.利用红外分峰手段,得知约51%的Brönsted酸分布于八元环和六元环交叉所形成的笼(cage)中,约23%分布于十元环孔道,26%分布于八元环孔道中.同时,利用吡啶在分子筛HZSM-35不同温度下的吸附情况验证了这一分峰结果.其次,利用钠离子交换方法制备不同Brönsted酸浓度的ZSM-35分子筛,经吡啶红外表征得知,Brönsted酸浓度随钠离子交换程度增加而逐渐降低,而Lewis酸浓度并未改变;在羟醛缩合反应性能中,丙烯酸及丙烯酸甲酯选择性和收率均随Brönsted酸浓度增加而逐渐升高,考虑到Lewis酸浓度并未变化,可知Brönsted酸是羟醛缩合反应性能的活性位点,其浓度增加有利于羟醛缩合反应性能的提高.同时,对比不同ZSM-35分子筛失活现象,高Brönsted酸浓度时分子筛重积炭量最高,这可能是由于Brönsted催化不饱和产物关环生成芳烃物种或(和)发生氢转移过程所导致.

关键词: 羟醛缩合反应, 乙酸甲酯, HZSM-35分子筛, Brönsted位, 丙烯酸

Abstract:

Acrylic acid (AA) and its ester, methyl acrylate (MA), were produced by a green one-step aldol condensation reaction of dimethoxymethane and methyl acetate. The reaction was conducted over ZSM-35 zeolites with different concentrations of Brönsted acid, which were prepared by the sodium ion-exchange process with H-form zeolite. The acidic property of HZSM-35 was studied in detail through infrared experiments. About 51% of all bridging OH groups were distributed in cages, while 23% and 26%, respectively, were distributed in 10-and 8-ring channels. The catalytic performance was enhanced by a high concentration of Brönsted acid, indicating that Brönsted acid is an active site for the aldol condensation reaction. The ZSM-35 zeolite possessing a concentration of Brönsted acid as high as 0.049 mmol/g demonstrated excellent performance with a MA+AA selectivity of up to 73%.

Key words: Aldol condensation, Methyl acetate, ZSM-35 zeolite, Brönsted acid, Acrylic acid