由乙二醇直接法制备乙二醇单（双）乙醚关键技术研究

发布时间：2018-08-12 20:32

【摘要】：乙二醇单(双)醚是一种应用广泛的有机中间体和优良溶剂,传统的合成方法是环氧乙烷法。本论文以乙二醇(EG)和乙醇(EtOH)为主要原料合成乙二醇单(双)乙醚(EGEE),通过热力学计算了反应条件的影响,对催化剂进行了设计和制备,对合成条件进行了优化。主要工作如下:1、通过Aspen Plus计算了温度、压力和投料比对反应体系平衡组成及EG转化率和EGEE收率的影响。结果表明,随着温度升高,热力学平衡体系中乙二醇单乙醚(EGMEE)的量有最大值,乙二醇双乙醚(EGDEE)的量逐渐降低,最佳反应温度为220℃;n(EtOH):n(EG)升高,有利于EGMEE、EGDEE和乙醚生成,并且会抑制二甘醇(DEG)和1,4-二氧六环(Diox)的生成。压力升高有利于平衡向生成蒸气压低的高沸点物质方向移动,对生成EGMEE和EGDEE有利,超过3 MPa后压力对反应转化率和选择性影响变小。通过化工热力学方法计算了理想气体状态下,EG和EtOH反应体系在不同温度下的平衡常数。结果表明,所计算的各反应焓变(△rH)值均为负值,低温有利于生成EGDEE。2、考察了不同类型的L酸、B酸、L碱及同时兼具酸碱性的金属盐对EG和EtOH合成EGEE的催化效果。结果表明,催化剂酸性越强,催化活性越高,表面同时具有酸性位点和碱性位点的催化剂对乙二醇醚的选择性较高。L酸中BF3活性最强,但选择性较差,无水AlCl3催化性能较好,在n(EtOH):n(EG)=4:1,反应时间4 h,反应温度260℃,反应压力7 MPa,催化剂用量为反应物总量的4%(wt)时,EGEE总收率最高,EG转化率为38.8%,EGMEE选择性为59.9%。AlCl3和Na2HPO4复配时可使催化剂同时具有酸性和碱性位点,能提高乙二醇醚的选择性,以n(AlCl3):n(Na2HPO4)=1:3为催化剂时,综合性能最佳,EG转化率和EGEE选择性分别为25.1%和72.3%。3、研究了分子筛催化剂制备方法对催化性能的影响。结果表明,以0.5mol·L-1硫酸铵水溶液通过过量浸渍法对硅铝比为25的HZSM-5进行改性,得到的催化剂较其他改性分子筛催化剂活性高,能将反应温度降低至180℃。通过扫描电镜(SEM)、电子能谱(EDS)、X射线衍射(XRD)、低温氮吸附(BET)、化学吸附仪(NH3-TPD)、热重(TG-DTG)等对HZSM-5分子筛的形貌、结构和性能进行了表征。结果表明,改性后HZSM-5分子筛表面引入了S元素,并新增了超强酸位点,比表面积和平均孔径较改性前小。通过正交实验和单因素法获得的最佳工艺条件为:反应温度180℃,反应时间4h,反应压力7 MPa,n(EtOH):n(EG)=4:1,催化剂用量为原料总质量的2%,此时EG转化率为68.8%,EGEE的选择性为92.4%,EGEE产率达到63.6%,与反应温度为200℃时的产率相近,且副产物明显减少。EG和EtOH在该催化剂上生成EGEE的反应为一级反应,表观活化能Ea=77.42 kJ·mol-1,指前因子k0=1.844×107 s。4、通过XRD、NH3-TPD、FTIR、SEM、EDS、BET、TG-DTG等方法对改性HZSM-5催化剂使用及失活前后的形貌、结构、表面元素、表面酸性和孔结构的变化进行表征,结果表明,催化剂在使用过程中失活的主要原因是由于积碳导致催化剂孔道堵塞、表面强酸位点减少造成的,在温度超过450℃,有氧条件下煅烧可有效除去积碳,使催化剂活性再生。5、考察了磷钨酸、磷钼酸、硅钨酸及其盐对EG合成EGEE的催化活性,结果表明,Cs_(0.66)Ag_(0.33)H_2PW_(12)O_(40)经300℃煅烧4 h得到的催化剂催化性能最好。采用XRD、Zeta电位及粒度仪、EDS等仪器对该催化剂进行了表征,结果表明,磷钨酸银和磷钨酸银铯具有典型的Keggin结构,通过中和沉淀法制备的Cs_(0.66)Ag_(0.33)H_2PW_(12)O_(40)平均粒径为68 nm,再分散性好,560℃时杂多阴离子Keggin结构才会被破坏,热稳定性好。该催化剂在n(EtOH):n(EG)=4:1,反应温度200℃,反应压力7 MPa,反应时间4 h,催化剂用量0.8%的反应条件下,能使EG的转化率(GC)达到96.2%,EGMEE和EGDEE的选择性(GC)分别达到49.3%和48.6%,EGEE的总产率(GC)为94.1%,接近热力学计算平衡值。以气相SiO_2为粘结剂对Cs_(0.66)Ag_(0.33)H_2PW_(12)O_(40)纳米颗粒通过压片,破碎,过筛等工艺进行成型,得到60~80目的催化剂颗粒耐水和EtOH稳定性好。最佳成型工艺为压片压力25 MPa,压片时间30 min,在此条件下成型的催化剂在固定床中连续反应100 h,催化活性未明显下降。
[Abstract]:Ethylene glycol monoether (EGEE) is a widely used organic intermediate and excellent solvent. The traditional synthesis method is ethylene oxide method. In this paper, EGEE was synthesized from ethylene glycol (EG) and ethanol (EtOH). The main work is as follows: 1. The effects of temperature, pressure and feed ratio on the equilibrium composition, EG conversion and EGEE yield of the reaction system are calculated by Aspen Plus. The results show that the amount of EGMEE in the thermodynamic equilibrium system reaches its maximum and the amount of EGDEE decreases gradually with the increase of temperature. The optimum reaction temperature is 220; n (EtOH): n (EG) increases, which is beneficial to the formation of EGMEE, EGDEE and ether, and inhibits the formation of diethylene glycol (DEG) and 1,4-dioxane (Diox). The equilibrium constants of EG and EtOH reaction systems at different temperatures in ideal gas were calculated by chemical thermodynamic method. The results showed that the calculated enthalpy changes (delta rH) were all negative and the low temperature was favorable to the formation of EGDEE.2. Different types of acid, B acid, L base and gold with both acid and base were investigated. The results showed that the stronger the acidity of the catalyst, the higher the catalytic activity, and the higher the selectivity of the catalyst with both acidic and basic sites on the surface to ethylene glycol ether. The total yield of EGEE was the highest when the reaction temperature was 260 C, the pressure was 7 MPa, and the amount of catalyst was 4%(wt) of the total amount of reactants. The conversion of EG was 38.8%, and the selectivity of EGMEE was 59.9%. When AlCl3 and Na2HPO4 were mixed, the catalyst had both acidic and basic sites, which could improve the selectivity of ethylene glycol ether. The catalytic activity of HZSM-5 with Si/Al ratio of 25.5 mol The morphology, structure and properties of HZSM-5 zeolite were characterized by scanning electron microscopy (SEM), electron energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), nitrogen adsorption at low temperature (BET), chemical adsorption apparatus (NH3-TPD), thermogravimetry (TG-DTG). The results showed that S element was introduced into the surface of HZSM-5 zeolite and Superacid was added. The optimum technological conditions obtained by orthogonal experiment and single factor method are as follows: reaction temperature 180 C, reaction time 4 h, reaction pressure 7 MPa, n (EtOH): n (EG) = 4:1, catalyst dosage 2% of the total mass of raw material, the conversion of EG is 68.8%, the selectivity of EGEE is 92.4%, and the yield of EGEE is 63.6%, respectively. The yield of EG and EtOH on the catalyst was similar and the by-products were obviously reduced at 200 C. The apparent activation energy Ea = 77.42 kJ mol-1 and the pre-exponential factor K0 = 1.844 107 S.4 were obtained by XRD, NH3-TPD, FTIR, SEM, EDS, BET, TG-DTG and other methods. Characterization of structure, surface elements, surface acidity and pore structure showed that the deactivation of the catalyst was mainly due to the pore blockage caused by carbon deposition and the decrease of strong acid sites on the catalyst surface. Calcination under aerobic conditions could effectively remove carbon deposition and regenerate the catalyst. 5 The catalytic activity of phosphotungstic acid, phosphomolybdic acid, silicotungstic acid and their salts for EGEE synthesis was studied. The results showed that the catalysts prepared by calcination of Cs_ (0.66) Ag_ (0.33) H_2PW_ (12) O_ (40) at 300 C for 4 h had the best catalytic performance. The catalysts were characterized by XRD, Zeta potential, particle size analyzer and EDS. The typical Keggin structure was prepared by neutralization precipitation method. The average particle size of CS_ (0.66) Ag_ (0.33) H_2PW_ (12) O_ (40) was 68 nm. The Keggin structure of heteropolyanion was destroyed and its thermal stability was good at 560 C. The catalyst had good thermal stability when n (EtOH): n (EG) = 4:1, reaction temperature 200 reaction pressure 7 MPa, reaction time 4 h, catalyst dosage 0.8%. Under the reaction conditions, the conversion of EG (GC) can reach 96.2%, the selectivity of EGMEE and EGDEE (GC) can reach 49.3% and 48.6%, respectively. The total yield of EGEE (GC) is 94.1%, which is close to the thermodynamic equilibrium value. The optimum forming process was 25 MPa pressure and 30 min time. Under this condition, the catalyst was continuously reacted in a fixed bed for 100 h, and the catalytic activity did not decrease significantly.
【学位授予单位】：郑州大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ223.2

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