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改性ZSM-5催化醋酸甲酯-甲醛合成丙烯酸甲酯过程研究
左村村
Subtype博士
Thesis Advisor李春山
2018-07
Degree Grantor中国科学院研究生院
Degree Name博士
Degree Discipline化学工程
Keyword丙烯酸及其酯,改性zsm-5催化剂,酸碱催化剂,醋酸甲酯,分离过程
Abstract

丙烯酸及其酯是一种重要的有机化学中间体和高分子聚合单体,目前主要的合成工艺为丙烯氧化酯化法,但是随着石油价格逐渐攀升,亟需要拓展新的合成路线。醋酸、甲醇和甲醛都是廉价的煤基化工原料,通过一步羟醛缩合生产丙烯酸甲酯是一种十分经济的煤基合成路线。本研究提出了利用丰富的醋酸、甲醛为原料通过羟醛缩合反应合成丙烯酸/酯的新过程并围绕着过程中收率低、积碳及分离问题进行了系统研究,分别从催化剂制备、催化剂物性及构效关系等方面考察对催化过程的影响规律,同时对复杂的产品体系开展了相平衡和分离过程研究,主要创新性成果如下:(1)设计合成了γ-Al2O3、SiO2、TiO2、ZrO2及ZSM-5为载体的系列酸碱改性催化剂。选用V、P、Sn作为酸性活性助剂,选用碱金属族或碱土金属元素作为碱性活性助剂,系统研究了改性前后比表面积、孔结构、酸碱性等物性参数在酸碱催化过程中扩散、吸附、界面反应以及积碳行为。重点研究了ZSM-5催化剂酸碱性及硅铝比等性质对催化活性的影响规律,发现了偏磷酸铝-Al(PO3)3晶相是通过改变催化剂表面酸性进而影响催化剂活性。(2)进一步阐明了酸碱催化剂的制备方法与催化机理及酸碱调变规律。明确了P改性ZSM-5系列催化剂中B酸和L酸中心在羟醛缩合反应中的不同作用,其中B酸中心主要和甲醛发生质子化作用,L酸可以促进含有α-H的羰基化合物进行烯醇化转化。详细阐述了活性组分改性量、不同磷源、焙烧温度、反应温度等因素对催化剂性质的影响,通过吡啶红外及TPD对催化剂中的酸碱性进行定性定量,获得了不同酸碱改性剂对催化剂中L酸和B酸的调变规律。通过晶相和活性关联,得出了Al(PO3)3晶相通过改变骨架中铝的配位数来调变骨架中B酸和L酸。通过催化醋酸甲酯和甲醛的反应活性研究,发现了骨架中L酸会促进羟醛缩合反应过程,而B酸会导致催化剂积碳的影响规律。(3)研究了以甲醛水溶液、三聚甲醛和多聚甲醛三种工业形式的甲醛为原料对P/ZSM-5催化剂的影响规律。通过活性和寿命评价,获得了三种原料产品收率高低顺序为三聚甲醛(45.5%)>甲醛水溶液(43.2%)>多聚甲醛(40.3%),及三种原料的催化剂寿命排序为甲醛水溶液<多聚甲醛≈三聚甲醛。详细研究了以甲醛水溶液为原料对催化剂活性、寿命及表面酸性的影响,证明了水会减少催化剂表面的L酸且增加B酸,这是造成催化剂寿命缩短的关键因素,进一步证实了(2)中L酸和B酸的影响规律。(4)系统研究了丙烯酸产品体系的热力学和分离过程。针对复杂的共沸四元(MA-MeOAc-Me-H2O)混合体系,实验获得了二元相平衡数据,进一步计算并推导了三元体系和四元体系的VLE和LLE相图,对热力学性质进行校正,获得了适用的热力学模型参数。在此基础上,设计了分离流程,并基于模拟软件进行了全流程的优化和集成,最后对整个分离过程进行多塔串联的放大分离验证,成功实现了丙烯酸体系的分离。 ;Acrylic acid and its esters are important organic chemical intermediates and polymers. At present, the main synthetic process is propylene oxide esterification. This work developed a new process of methyl acrylate production through one-step synthesis by aldol condensation with acetic acid, methanol and formaldehyde. The method of efficient catalyst development was investigated and the effects of the pore structure and acid-base characteristics on the catalyst activity were found. The phase equilibrium of product mixture was determined and suitable separation method was obtained. The main findings of this paper are as follows:(1) A series of acid-base modified catalysts were designed and synthesized respectively using γ-Al2O3, SiO2, TiO2, ZrO2 and ZSM-5 as support. The influences of various physical parameters such as specific surface area, pore structure and acid-base properties on acid-base catalysis process including the diffusion, adsorption, interface reaction and carbon deposition were systemically demonstrated. The results were shown that modified ZSM-5 exhibits better catalytic activity and selectivity. In particular, the important influences of acid-base properties and Si/Al ratio on the catalytic activity were studied.(2) The preparation methods of acid-base catalysts and the mechanism of selective catalysis and the regularities of acid-base adjustment catalyst were further clarified. B acid and L acid center in the P-modified ZSM-5 series catalyst were found playing different roles in the catalyzed process. The L acid center can promote the enolization of carbonyl compounds containing α-H and the B acid center mainly protonates with formaldehyde, but B acid was the reason of rapid carbon deposition. The effects of loading of active components, different phosphorus sources, calcination temperature and reaction temperature on the properties of the catalysts are clearly elucidated and the adjustment regularity of L acid and B acid with a variety of acid-base modifier was obtained after qualitatively and quantitatively being determined by pyridine and infrared spectroscopy and CO2-TPD. The formation of aluminum metaphosphate will change the coordination number of aluminum in the framework, accompanied by the reducing in the B acid and increase in the L acid in the skeleton. According to the investigation on the catalytic activity for the reaction of methyl acetate and formaldehyde, it was found that the L acid promoted the aldol reaction, and the B acid was the main reason of rapid carbon deposition.(3) The effects of different formaldehyde sources containing formaldehyde solution, trioxymethylene, and paraformaldehyde on the catalytic performance of P / ZSM-5 catalyst were studied. The yield of acrylic acid and its ester in descending order was trioxymethylene (45.5%) > formaldehyde solution (43.2%) > paraformaldehyde (40.3%). The catalyst life in descending order was formaldehyde aqueous solution > paraformaldehyde ≈ paraformaldehyde. When the formaldehyde aqueous solution was used as the material, the catalyst life will be shortened after recycling due to changes in the aqueous environment. The Pyridine infrared was performed to detect acid distribution on the catalyst surface. The results were found that the content of total B acid on the catalyst deactivated increased, and the L acid reduced in the presence of water. The influence regularity of L acid and B acid mentioned in (2) was further confirmed.(4) Thermodynamics and separation process of acrylic product system were systematically studied. The research object was aimed to the complex azeotropic system (MA-MeOAc-Me-H2O). The missing binary phase equilibrium data was obtained by the experiment and the VLE and LLE phase diagram of the ternary system and the phase diagram of the quaternary system were constructed. The thermodynamic properties were corrected step by step to obtain the more accurate thermodynamic model parameters. On this basis, the separation process was designed and the whole process was optimized and integrated based on the simulation software. In the end, the separation of the acrylic system was verified by the amplification experiment and the whole separation process was successfully realized. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/26880
Collection中国科学院过程工程研究所
研究所(批量导入)
Recommended Citation
GB/T 7714
左村村. 改性ZSM-5催化醋酸甲酯-甲醛合成丙烯酸甲酯过程研究[D]. 中国科学院研究生院,2018.
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