催化纤维素制备乙二醇及新型膜分离研究

发布时间：2018-06-09 16:38

本文选题：纤维素 + 催化剂　；参考：《华南理工大学》2016年博士论文

【摘要】：持续减少的石化资源及不断增长的能源消耗最终将导致能源的短缺以及严重的环境问题。利用可再生的生物质资源制备能源及化学品将有效地解决上述问题,作为具有替代石化资源潜力的纤维素,是以葡萄糖单体为单元的天然高分子化合物,具有分布广泛、储量丰富、可再生、非食用等特点,在过去的十几年里,采用纤维素类生物质为原料制备高附加值化学品及能源逐渐引起人们的关注。在化学转化纤维素类生物质的研究中,水热条件下催化转化纤维素制备乙二醇被认为是极具潜力的过程,该化学转化过程具有原子经济性极高、产物附加值高及市场需求大等特点。然而,由于纤维素分子间以及分子内极强的氢键作用,温和条件下有效地降解纤维素具有一定的挑战。其次,纤维素降解产物高效转化制备目标产物的控制相当复杂。第三,用于制备乙二醇的生物质原料有待丰富。此外,乙二醇/水混合体系环保、低耗的分离纯化技术手段急需开发。针对以上问题,本论文的主要内容如下:1.采用超低浓度磷钨酸(Phosphotungstic acid—PTA)水解纤维素制备葡萄糖的同时,选择性催化断裂葡萄糖C-C键,耦合钌碳(Ruthenium on carbon—Ru/AC)催化降解产物,当PTA浓度为0.03wt%,反应50min,实现纤维素100%转化,乙二醇得率达53.1%。其次,探究PTA-Ru/AC复合催化剂稳定性及回用性能,随催化剂回用次数的增加催化剂催化性能逐渐降低,借助SEM、TEM、XPS、AAS、IR、TG等检测手段表征反应前后催化剂,回用Ru/AC催化剂表面吸附有机物或发生结焦,导致催化剂颗粒絮聚,活性位点被遮盖,乙二醇得率下降。此外,选择纤维素二糖作为原料,用于乙二醇制备反应,采用HPLC-MS分析反应产物,研究乙二醇生成路径,结果表明:催化转化纤维素二糖制备乙二醇反应至少有三条路径同时发生,且这三条路径很可能存在于催化转化纤维素制备乙二醇反应中。2.采用乙二醇水热还原法制备以石墨烯(Graphene)为载体的双金属催化剂Ru-WO_3/Graphene,借助XRD、SEM、EDX、TEM等检测手段,表征催化剂性质,催化剂具有特殊形貌特征,即纳米棒状WO_3和Ru金属纳米颗粒均匀分布在石墨烯载体表面。其次,采用Ru-WO_3/Graphene催化转化纤维素制备乙二醇反应,研究反应温度、反应时间、催化剂组成及用量等参数对产物种类及得率的影响。在最优反应条件下,催化剂表现出较高的活性和选择性,乙二醇最高得率达57.5%,纤维素100%转化。此外,研究催化剂回用对反应产物得率的影响,借助XRD、SEM、TEM、TG、IR等检测手段表征回收前后的催化剂,探究催化剂催化效果变化的原因。3.为丰富制备乙二醇的生物质原料种类,实验以工业废弃物——木薯渣为原料,采用多种复合催化剂催化木薯渣制备乙二醇研究。首先,表征木薯渣成分,木薯渣中碳水化合物含量约占90wt%,有利于乙二醇的制备。其次,筛选不同复合催化剂催化转化木薯渣制备乙二醇,Ru/AC-H_2WO_4表现出较好的活性及选择性,245℃水热条件下,反应60min,乙二醇得率达53.1%。此外,最优反应条件下,研究Ru/AC-H_2WO_4复合催化剂稳定性和可回用性能。催化剂回用四次后,乙二醇得率降至50%以下,借助XRD检测表明:木薯渣成分中Ca和Fe等矿物元素与复合催化剂中H_2WO_4反应,生成不溶物CaWO_4和FeWO_4,消耗催化剂用量,乙二醇得率下降。4.采用溶剂热法成功合成共价有机框架材料——COF-1,借助XRD、FT-IR、TG、TEM、SEM、BET等手段表征材料性质,COF-1为层状结构,呈片状,氮气环境中450℃保持稳定,具有较高的热稳定性,平均孔径约0.7nm,比表面积710m~2/g。超声剥离COF-1材料制备纳米片作为COF-1膜构成单元,在多种载体表面形成连续膜层,拓展了材料的应用范围。借助气体分离装置,检测单种气体COF-1膜通透性能,材料具有较高的氢气透过性能,且高温下保持良好的稳定性。5.采用溶剂热法成功合成亚胺键连接的共价有机框架材料——ACOF-1,借助XRD、FT-IR、TG、TEM、SEM、BET等检测手段表征材料性质,ACOF-1呈片状,含有C=N-N共价键组成的环状结构,在氮气环境中,热稳定性可达320℃,材料比表面积为819m~2/g,平均孔径约1.22nm。超声剥离ACOF-1材料形成纳米片作为ACOF-1膜组成单元,负载在陶瓷管表面,形成连续、完整的膜。借助渗透蒸发技术,考察ACOF-1膜分离乙二醇/水混合体系性能,ACOF-1膜对乙二醇/水混合体系一直保持良好的分离性能,稳定性较好,当乙二醇浓度为90%,50℃条件下,ACOF-1膜渗透通量为0.139kg/(m~2h),分离因子为552。
[Abstract]:The continuous reduction of petrochemical resources and increasing energy consumption will eventually lead to a shortage of energy and serious environmental problems. The use of renewable biomass resources to produce energy and chemicals will effectively solve the above problems as a cellulose that has the potential to replace the petrochemical resources and is a natural high grade with the glucose monomer as the unit. Subcompounds are widely distributed, rich in reserves, renewable and non edible. In the past decade, the use of cellulosic biomass as raw material to prepare high value-added chemicals and energy has gradually aroused people's attention. In the study of chemical conversion of cellulose biomass, the catalytic conversion of cellulose to ethylene glycol under hydrothermal conditions It is considered to be a highly potential process with high atomic economy, high added value and large market demand. However, the effective degradation of cellulose under mild conditions has a definite challenge due to the intermolecular and intramolecular strong hydrogen bonds. Secondly, the efficient transformation of cellulose degradation products. Third, the biomass for preparation of glycol remains to be rich. In addition, the ethylene glycol / water mixture system is environmentally friendly and the low consumption separation and purification techniques are urgently needed. The main contents of this paper are as follows: 1. hydrolysis of ultra low concentration phosphotungstic acid (Phosphotungstic acid - PTA) When the glucose is prepared by cellulose, the glucose C-C bond is selectively catalyzed and the ruthenium carbon (Ruthenium on carbon - Ru/AC) is coupled to catalyze the degradation products. When the concentration of PTA is 0.03wt%, the reaction 50min, the cellulose 100% is converted, the ethylene glycol yield is up to 53.1%. next, and the stability and reuse performance of the PTA-Ru/ AC composite catalyst is explored and the catalyst is reused with the catalyst. The catalytic performance of the catalyst decreased gradually. With the help of SEM, TEM, XPS, AAS, IR, TG and other detection methods, the catalyst was characterized before and after the reaction, and the organic matter was adsorbed on the surface of the Ru/AC catalyst or coking, which resulted in the flocculation of the catalyst particles, the active site was covered and the yield of ethylene glycol decreased. In addition, the cellulose two sugar was selected as the raw material and used in B two as the material. The reaction products were prepared by HPLC-MS, and the production path of ethylene glycol was studied. The results showed that at least three routes were produced by catalytic conversion of cellulose two sugar to ethylene glycol, and the three paths were likely to be prepared by the hydrothermal reduction of ethylene glycol in the catalytic conversion of cellulose to ethylene glycol in the catalytic conversion of cellulose to.2.. Graphene as a bimetallic catalyst Ru-WO_3/Graphene, with the help of XRD, SEM, EDX, TEM and other detection methods to characterize the catalyst, the catalyst has special features, that is, the nano rod like WO_3 and Ru metal nanoparticles are evenly distributed on the surface of the graphene carrier. Secondly, a Ru-WO_3/Graphene catalyzed conversion of cellulose to the preparation of B two is made. The effects of reaction temperature, reaction time, catalyst composition and dosage on the product type and yield were studied. Under the optimal reaction conditions, the catalyst showed high activity and selectivity, the highest yield of ethylene glycol was 57.5%, cellulose 100% was converted. In addition, the effect of the catalyst reuse on the yield of the reaction products was studied with the aid of XRD, SEM, TEM, TG, IR and other detection methods were used to characterize the catalyst before and after recovery, and to explore the cause of the change in the catalytic effect of the catalyst.3. was a kind of biomass for the preparation of ethylene glycol. The experiment was made of cassava residue from cassava residue, which was used as the material of industrial waste - cassava residue as raw material. The carbohydrate content in sweet potato residue is about 90wt%, which is beneficial to the preparation of ethylene glycol. Secondly, different composite catalysts are screened to catalyze the conversion of tapioca residue to ethylene glycol, and Ru/AC-H_2WO_4 shows good activity and selectivity. Under the condition of water and heat at 245 C, the reaction of 60min and ethylene glycol yield to 53.1%., and the study of Ru/AC-H_2WO_4 under the optimal reaction conditions When the catalyst was used for four times, the yield of ethylene glycol was reduced to less than 50%. The XRD test showed that the mineral elements such as Ca and Fe were reacted with H_2WO_4 in the composition of the cassava residue, and the insoluble CaWO_4 and FeWO_4 were generated, the amount of catalyst was consumed and the yield of ethylene glycol decreased by the solvent heat method. The synthetic covalent organic frame material, COF-1, characterizing the material properties by means of XRD, FT-IR, TG, TEM, SEM, BET, and so on. COF-1 is a layered structure, and it is stable at 450 C in the nitrogen environment, with high thermal stability and an average pore size of about 0.7nm. The nanoscale film is prepared as a membrane component with the specific surface area 710m~ 2/g. ultrasonic stripped COF-1 material. A continuous film is formed on the surface of a variety of carriers to expand the application range of the material. With the aid of gas separation device, the permeability of the single gas COF-1 film is detected. The material has high hydrogen permeability and good stability at high temperature..5. is successfully synthesized by the solvent heat method, the covalent organic frame material of the imide bond, ACOF-1 By means of XRD, FT-IR, TG, TEM, SEM, BET and other detection methods, the properties of the materials are characterized. ACOF-1 is flaky and contains a circular structure consisting of C=N-N covalent bonds. In the nitrogen environment, the thermal stability is up to 320, the specific surface area of the material is 819m~2/g, and the average pore size about 1.22nm. ultrasonic stripping ACOF-1 material is formed as a member of the ACOF-1 membrane, and the load is in pottery. On the surface of the porcelain tube, a continuous and complete membrane was formed. By pervaporation, the performance of ACOF-1 membrane was separated from the mixture of ethylene glycol / water. The ACOF-1 membrane had good separation performance and good stability for the ethylene glycol / water mixture system. When the ethylene glycol concentration was 90%, 50 C, the permeation flux of ACOF-1 membrane was 0.139kg/ (m~2h) and the separation factor was 5 Fifty-two
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ223.162;TQ028.8

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