生物质热解油临氢催化酯化改质的研究

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	生物质热解油临氢催化酯化改质的研究
其他题名	Upgrading the Liquid products of Biomass Pyrolysis by Hydrotreating and Esterification
	徐莹
导师	马隆龙研究员
	2009-04-26
学位授予单位	中国科学院广州能源研究所
学位授予地点	广州能源研究所
学位名称	博士
关键词	生物油改质提升催化酯化固体碱临氢催化酯化
摘要	随着世界经济与全球化的发展，人类对化石燃料和能源需求越来越强烈。但是能源的过度开发与利用将导致的环境污染，引起了人们广泛的重视。生物质能的开发与利用相对于其他不可再生能源，环境友好。而且作为能源消耗时，产生的CO¬2会被植物等量的吸收，实现CO2的零排放；与化石燃料相比，生物质含硫、氮较少，是一种较清洁的能源。我国生物质资源丰富，生物质能的开发和利用对于我国的能源安全有重要的意义。利用生物质的热解液化技术得到产率较高的液体产物生物油，可使生物质成为最有可能部分替代化石能源的可再生能源。然而液体产物生物油粘稠、稳定性差、腐蚀性强、化学组成复杂等缺点给生物油的开发和利用带来了极大的阻碍，成为生物油工业化利用的瓶颈。对生物油进行改质，提高生物油品质势在必行。现阶段生物质热解的方法主要集中在快速热解方法。生物油的精制主要有以下几种方法：生物油加氢脱氧得到烃类物质，该方法成本较高，设备较复杂，操作过程中经常遇到反应器堵塞和催化剂失活等现象；生物油催化裂解得到轻质组分，该方法成本较低，但是催化剂结焦率高，得到的精制油质量较差；生物油水蒸气重整制氢，该方法的工艺比较复杂，对设备要求较高，需要开发成熟、稳定、与反应器相适合的催化剂；生物油的乳化，该方法虽然无需过多的化学过程，但是其乳化成本和乳化需要的能量投入较高，而且乳化油对汽车发动机的抗腐蚀要求很高；生物油的固体酸催化酯化，虽然可以降低生物油的粘度、增强稳定性，但是固体酸的强酸化作用使生物油的酸性增强。针对生物油pH值较低、酸性较强、羧酸含量较高等特点，利用固体碱与负载型加氢催化剂催化改质生物油，将催化加氢与酯化反应相耦合，探索生物油改质的新方法。首先本文对生物油的制备进行了新方法的探索。以松木粉为原料，利用真空热解和快速热解两种方法制备生物油，并研究真空热解条件（热解温度与热解原料粒径）对生物质热解各相产物产率的影响。实验结果表明，真空热解生物质以500℃的热解温度、40-60目的原料粒径时，制得的液体产率最高为52.60％。通过不同方法和不同原料制备的生物油品质及气相产物组成的对比，得出不同来源生物油的异同点。不同方法相同原料制备得到的生物油性质相差较大主要是由于热解过程不同所造成。但是所得的生物油却有着共同的特点，其pH值较低、酸性较强、成分十分复杂。针对生物油的共性，本文开发了固体碱催化剂，旨在通过固体碱的催化酯化作用，提高生物油的pH值，降低酸性。并选取生物油中羧酸含量较高的乙酸为模型化合物，并以乙酸与乙醇的酯化反应活性来评价固体碱催化剂催化酯化的反应活性。将筛选出的活性最高的固体碱催化剂应用于生物油的改质提升。分别以不同载体，不同前驱体制备固体碱催化剂，经筛选得出以γ-Al2O3为载体，负载15％的K2CO3固体碱催化剂催化酯化活性相对最好，并将该催化剂应用于生物油催化酯化的反应中。催化酯化改质后生物油的pH值由2.60升到5.35，运动黏度降低了86.2%，热值提高了45.78%，酯含量明显增加，酸性物质含量减少。继固体碱催化酯化改质后，主要是探索和开发临氢催化酯化改质提升生物油的新方法。分别以钌系与镍系催化剂为主要活性中心，采用乙酸为模型化合物以评价两类负载型催化剂临氢催化酯化的反应活性。对两类催化剂的负载量进行了讨论，并结合催化剂的表征以说明不同负载量导致其活性差异的原因。对于钌系催化剂，考察不同助剂的添加对催化剂临氢催化酯化活性的影响。筛选出0.5％Ru负载量、Co为助剂的催化剂催化乙酸临氢催化酯化转化率为最高（30.98％），并将其应用在自制的快速热解生物油的临氢催化改质的反应中。对于镍系催化剂，讨论了不同镍负载量对催化剂活性的影响，并讨论了助剂Mo的添加量、催化剂的还原温度对催化剂活性的影响。对催化剂进行了XRD和TPR表征，并结合催化剂的活性筛选出最优的镍系催化剂为10％的镍负载量、0.06g/g钼添加量、600℃的还原温度的催化剂。并将其分别应用在自制的真空热解生物油与快速热解生物油的临氢催化改质中。临氢催化酯化改质的主要思路是将生物油中含有的羧酸类、酮类、醛类等不饱和含氧类化合物加氢变为醇类化合物，生成的醇与未反应的羧酸类化合物发生酯化反应，生成酯的一个临氢催化酯化的反应过程。通过临氢催化酯化改质后的生物油，其物化性能均有所提升，通过对其组成进行表征，可以看出在生物油的临氢催化酯化改质前后，确有改质的主要思路下的临氢酯化反应发生，更有加氢、酯化等反应伴随。生物油的性能有所改进。
其他摘要	With the development of the world economy and the globalization, the demand of fossil fuel reserves and the energy are increasing. Concerns about the pollution caused by continuously increasing in the energy demands of the world make biomass an attractive alternative energy source. In the case that biomass is utilized to as an energy resource, the emission of carbon dioxide caused by its use is absorbed by newly grown biomass and this is called as carbon-neutral. Moreover, for the negligible sulfur, nitrogen and metal contents comparing with fossil fuels, biomass is a clean energy source. In China, there is abundance of biomass. Therefore the development and utilization of biomass energy is significative to the energy security of China. Biomass pyrolysis is an efficient process of biomass conversion with high yield of liquid fuel, which makes biomass the most promising renewable energy to substitute the convertional fossil fuel. But the negative properties of bio-oil, such as the high viscosity, instability, severe corrosiveness and complicated composition put a lot of obstacles for its replacing process consequently, and have become a bottle-mech in its full applications. An urgen necessity to upgraded bio-oil is demanding. At present, the common method for bio-oil is the fast pyrolysis of biomass. Among the bio-oil upgrading techniques, hydrodeoxygenation process needs complicated equipments, superior techniques and excessive cost and usually is halted by catalyst deactivation and reactor clogging. Although catalytic cracking is regarded as a cheaper route by converting oxygenated feedstocks to lighter fractions, the results seem to promising due to high coking and poor quality of the fuels obtained. Emulsification does not demand redundant chemical transformations, but the high cost and energy consumption input cannot be neglected. The accompanying corrosiveness to the engine and the subassemblies is inevitably serious. The upgrading bio-oil by esterification over solid acid can make the bio-oil less visicosit and more stability but increase the acidity for the catalyst present. Based on the characteristic of high acidity, low pH value and high total amount and multi-organic existence, solid base catalysts, solid base and hydrotreating catalysts were used for the upgrading bio-oil by esterification. The novel method was investigated for upgrading bio-oil by esterification under the atmosphere of hydrogen. First, the novel method for bio-oil was investigated. In the article, the bio-oil was prepared from pine sawdust by fast pyrolysisi and vacuum pyrolysis. The conditions of vacuum pyrolysis, just like temperature and the feedstock size were investigated. When the pyrolysis temperature was 500℃ and the size of the particle was in the mesh of 40-60 mesh, the most yield of liquid product was obtained (52.60%). By the comparison of the properties and the gas product of the two kinds of bio-oils, the difference and common ground were found. Bio-oil prepared from the same material in different pyrolysis ways had different properties is mainly because of the difference pyrolysis process. However, the bio-oils shared the common characteristics, such as low pH value, strong acid and complicated compositions. Based on the characters of bio-oils, in this article, the solid base catalyst was developed, aiming at the adoption of solid base catalyst for esterification, which could improve the pH value of bio-oil and reduce the acidity. Acetic acid was chosen as the model compound and the esterification with ethanol for evaluating the activity of solid base catalysts. The solid base catalyst with the highest activity was screened out for the application of upgrading bio-oil. In this chapter, the solid base catalysts were prepared by different carriers and different precursor. The activity of the solid base catalyst with γ-Al2O3 carrier, loading 15% of K2CO3 was the relative best, which was applied for the uptrading of bio-oil. After upgrading, the pH value increased from 2.60 to 5.35, the viscosity decreased by 86.2% and the calorific value increased by 45.78%. The ester content had a marked increase, and the acid content decrease. In this article, the novel method is explored and developed. The ruthenium and nickel-based catalysts were chosen as the main active site, using acetic acid as a model compound to evaluate the two types of catalysts for the activity of esterification under the atmosphere of hydrogen. For ruthenium-based catalysts, the catalytic activity of esterification under the atmosphere of hydrogen was studied by the addition of different metals as a promoter. The catalyst with 0.5% Ru loading, Co promoter had the highest activity for acetic acid conversion (30.98%), which was applied on the upgrading of self-made fast pyrolysis bio-oil. For nickel-based catalyst, the nickel loading on the catalyst activity was discussed. The Mo promoter and catalyst reduction temperature were also investigated on catalyst activity. XRD and TPR showed that the addition of Mo promoter benefited to the uniformity of nickel species on the catalysts and inhibited the formation of NiAl2O4 spinel. The catalyst with 10% Ni loading, 0.06g/g addition of molybdenum, 600 ℃ of the catalyst reduction temperature had the highest activity for acetic acid conversion, which was applied on the upgrading of self-made fast pyrolysis and vacuum pyrolysis bio-oil. After the upgrading of bio-oils under the atmosphere of hydrogen, both the physical and chemical properties were enhanced. The results of GC-MS spectrometry analysis showed that the content of esters increased and the content of acids decreased. Both hydrotreatment and esterification happened during the upgrading of the raw bio-oils. Results indicate that it is possible to improve the properties of bio-oils by hydrotreating and esterificationg carboxyl group compounds in the bio-oils.
页数	116
语种	中文
文献类型	学位论文
条目标识符	http://ir.giec.ac.cn/handle/344007/5832
专题	中国科学院广州能源研究所
推荐引用方式 GB/T 7714	徐莹. 生物质热解油临氢催化酯化改质的研究[D]. 广州能源研究所. 中国科学院广州能源研究所,2009.

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