生物质合成气一步法制备二甲醚双功能催化剂的研究
发布时间：2018-08-22 17:34
【摘要】：生物质能源具有资源丰富、可再生且不增加地表CO_2循环总量的特点,是化石能源的理想替代品。通过生物质合成气制备二甲醚是生物质能源利用的一条重要途径。本文制备了双功能催化剂用于生物质合成气一步法制二甲醚。考察了甲醇合成催化剂CuO-ZnO-MO_x (M=Zr, Al,Cr,Ti)中第三组元MO_x的影响、甲醇合成和甲醇脱水催化剂复合方式的影响、金属镁掺杂对催化剂稳定性的影响。主要结果如下:一、CuO-ZnO-MO_x (M=Zr,Al,Cr, Ti)/HZSM-5 双功能催化剂中 MO_x 对生物质合成气制DME的影响采用共沉淀法制备了一系列甲醇合成催化剂CuO-ZnO-MO_x (M=Zr, Al,Cr,Ti)。结果表明CuO-ZnO-Zr02催化剂有最大的SBET和铜比表面。经还原和反应后的CuO-ZnO-MO_x催化剂,表面铜元素均以Cu0形式存在。将CuO-ZnO-MO_x与HZSM-5按颗粒混合方式组成双功能催化剂用于生物质合成气一步法制DME。结果显示CuO-ZnO-ZrO_2/HZSM-5催化剂具有最高的CO转化率和DME收率。CO转化率随着铜比表面积的增加而升高,但两者并不是线性关系。水气反应产生的原位H2能促进CO加氢,提高DME的收率,这对具有“贫氢”特性的生物质合成气制DME过程尤为重要。二、催化剂复合方式对生物质合成气制DME的影响考察了四种不同复合方式(分层、颗粒混合、粉末混合和核壳结构)制备的双功能催化剂CuO-ZnO-Al_2O_3/HZSM-5对生物质合成气制DME的影响。复合方式影响反应活性位的性质;复合方式影响双功能催化剂的宏观结构,进而影响两组分之间的协同作用。颗粒混合方式所得催化剂具有最高的CO转化率和DME收率,而分层方式的CO转化率和DME收率最低。复合方式对催化性能的影响进一步验证了水气反应产生的原位H2可以促进甲醇的生成,从而获得更高的DME收率。甲醇合成催化剂中Cu晶粒的增大是双功能催化剂失活的主要原因,而反应中H2O的生成则是导致Cu晶粒增大的主要因素。此外,还考察了反应温度、压力和空速对催化性能的影响。三、MgO的添加对催化剂稳定性的影响通过等体积浸渍法制备了 MgO改性的CuO-ZnO-Al_2O_3催化剂,将其与HZSM-5按颗粒混合方式得到双功能催化剂。实验结果表明双功能催化剂中铜基催化剂的失活导致双功能催化剂活性下降,而Cu晶粒长大是铜基催化剂失活的主要原因。HZSM-5表面有少量的积炭,但不是催化剂失活的主要因素。MgO的添加增加了 CuO的还原难度,但抑制催化剂中Cu粒径的长大,降低催化剂失活的速率。
[Abstract]:Biomass energy is an ideal substitute for fossil energy because it is rich in resources, renewable and does not increase the total amount of surface CO_2 cycle. The synthesis of dimethyl ether from biomass syngas is an important way to utilize biomass energy. In this paper, bifunctional catalysts were prepared for one-step synthesis of dimethyl ether from biomass syngas. The effects of the third component (MO_x) in methanol synthesis catalyst CuO-ZnO-MO_x (Mn-Zr-Al-Cr-Ti), the combination of methanol synthesis and methanol dehydration catalyst, and the influence of magnesium doping on the stability of the catalyst were investigated. The main results are as follows: (1) the effect of MO_x on the synthesis of DME from biomass syngas in CuO-ZnO-MOx (MZZrO- AltCr, Ti) / HZSM-5 bifunctional catalysts was studied. A series of methanol synthesis catalysts, CuO-ZnO-MO_x (Mzororcalori, AlniCr-Ti), were prepared by coprecipitation method. The results show that the CuO-ZnO-Zr02 catalyst has the largest SBET and copper specific surface. After reduction and reaction, copper on the surface of CuO-ZnO-MO_x catalyst exists in the form of Cu0. The bifunctional catalyst composed of CuO-ZnO-MO_x and HZSM-5 was used in the one-step synthesis of biomass syngas. The results showed that CuO-ZnO-ZrO_2/HZSM-5 catalyst had the highest CO conversion and DME yield. Co conversion increased with the increase of copper specific surface area, but the relationship between them was not linear. In situ H2 produced by water gas reaction can promote CO hydrogenation and improve the yield of DME, which is particularly important for the production of DME from biomass syngas with "hydrogen deficiency" characteristics. Secondly, the effect of catalyst recombination on the production of DME from biomass syngas was studied. The effects of four different ways (stratification, particle mixing, powder mixing and core-shell structure) on the production of DME from biomass syngas were investigated. The compound mode affects the properties of the reactive sites and the macrostructure of the bifunctional catalysts and the synergism between the two components. The catalyst obtained by particle mixing has the highest CO conversion and DME yield, but the lowest CO conversion and DME yield is obtained by stratified method. The effect of the composition method on the catalytic performance further verified that in situ H2 produced by the water gas reaction could promote the formation of methanol, thus obtaining a higher yield of DME. The increase of Cu grain in methanol synthesis catalyst is the main reason for the deactivation of the bifunctional catalyst, while the formation of H2O in the reaction is the main factor leading to the increase of Cu grain. In addition, the effects of reaction temperature, pressure and space velocity on the catalytic performance were investigated. The influence of the addition of MgO on the stability of the catalyst the MgO modified CuO-ZnO-Al_2O_3 catalyst was prepared by the equal volume impregnation method. The bifunctional catalyst was prepared by mixing it with HZSM-5 in a granular manner. The experimental results show that the deactivation of Cu-based catalyst in bifunctional catalyst leads to the decrease of activity of the bifunctional catalyst, and Cu grain growth is the main reason for the deactivation of Cu-based catalyst. There is a small amount of coking on the surface of HZSM-5. But it is not the main factor of catalyst deactivation. The addition of MgO increases the reduction difficulty of CuO, but inhibits the growth of Cu particle size in the catalyst and reduces the deactivation rate of the catalyst.
【学位授予单位】：上海应用技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ223.24
本文编号：2197823
[Abstract]:Biomass energy is an ideal substitute for fossil energy because it is rich in resources, renewable and does not increase the total amount of surface CO_2 cycle. The synthesis of dimethyl ether from biomass syngas is an important way to utilize biomass energy. In this paper, bifunctional catalysts were prepared for one-step synthesis of dimethyl ether from biomass syngas. The effects of the third component (MO_x) in methanol synthesis catalyst CuO-ZnO-MO_x (Mn-Zr-Al-Cr-Ti), the combination of methanol synthesis and methanol dehydration catalyst, and the influence of magnesium doping on the stability of the catalyst were investigated. The main results are as follows: (1) the effect of MO_x on the synthesis of DME from biomass syngas in CuO-ZnO-MOx (MZZrO- AltCr, Ti) / HZSM-5 bifunctional catalysts was studied. A series of methanol synthesis catalysts, CuO-ZnO-MO_x (Mzororcalori, AlniCr-Ti), were prepared by coprecipitation method. The results show that the CuO-ZnO-Zr02 catalyst has the largest SBET and copper specific surface. After reduction and reaction, copper on the surface of CuO-ZnO-MO_x catalyst exists in the form of Cu0. The bifunctional catalyst composed of CuO-ZnO-MO_x and HZSM-5 was used in the one-step synthesis of biomass syngas. The results showed that CuO-ZnO-ZrO_2/HZSM-5 catalyst had the highest CO conversion and DME yield. Co conversion increased with the increase of copper specific surface area, but the relationship between them was not linear. In situ H2 produced by water gas reaction can promote CO hydrogenation and improve the yield of DME, which is particularly important for the production of DME from biomass syngas with "hydrogen deficiency" characteristics. Secondly, the effect of catalyst recombination on the production of DME from biomass syngas was studied. The effects of four different ways (stratification, particle mixing, powder mixing and core-shell structure) on the production of DME from biomass syngas were investigated. The compound mode affects the properties of the reactive sites and the macrostructure of the bifunctional catalysts and the synergism between the two components. The catalyst obtained by particle mixing has the highest CO conversion and DME yield, but the lowest CO conversion and DME yield is obtained by stratified method. The effect of the composition method on the catalytic performance further verified that in situ H2 produced by the water gas reaction could promote the formation of methanol, thus obtaining a higher yield of DME. The increase of Cu grain in methanol synthesis catalyst is the main reason for the deactivation of the bifunctional catalyst, while the formation of H2O in the reaction is the main factor leading to the increase of Cu grain. In addition, the effects of reaction temperature, pressure and space velocity on the catalytic performance were investigated. The influence of the addition of MgO on the stability of the catalyst the MgO modified CuO-ZnO-Al_2O_3 catalyst was prepared by the equal volume impregnation method. The bifunctional catalyst was prepared by mixing it with HZSM-5 in a granular manner. The experimental results show that the deactivation of Cu-based catalyst in bifunctional catalyst leads to the decrease of activity of the bifunctional catalyst, and Cu grain growth is the main reason for the deactivation of Cu-based catalyst. There is a small amount of coking on the surface of HZSM-5. But it is not the main factor of catalyst deactivation. The addition of MgO increases the reduction difficulty of CuO, but inhibits the growth of Cu particle size in the catalyst and reduces the deactivation rate of the catalyst.
【学位授予单位】：上海应用技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ223.24
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