【作者】 张军；

【导师】 王飞；

【作者基本信息】 南京林业大学 ， 林产化学加工工程， 2022， 博士

【摘要】 全球能源需求的日益增长,化石资源储量的逐渐枯竭,国际低碳排放的环保要求以及化石燃料应用导致的环境污染等因素,使得开发环境友好可再生的生物质燃料迫在眉睫。木本油脂和废弃油脂等非食用油脂由甘油三酯组成,具有良好的流动性、较高的能量密度以及与化石燃料相似的化学结构,是制备生物质燃料的优良选择。因其粘度较高,而不适合直接用作内燃机燃料。热解与酯交换技术可以有效降低其粘度,并将油脂转化为生物油和生物柴油。但这些生物质燃料中含氧组分的存在,使其与现有石化燃油的兼容性较差。通过催化裂解技术可有效地将油脂类原料及其衍生物直接转化为无氧的生物质烃类燃料,即富烃燃油,实现与石化燃油完全兼容。本论文以常压固定床连续反应装置催化脂肪酸甲酯裂解芳构化制备芳烃,或直接催化裂解甘油三酯制备富烃燃油为目标,制备并表征了一系列固体酸催化剂,对其催化活性及脱氧、裂解和芳构化机理进行了研究,主要研究结果如下:（1）锌改性分子筛催化剂制备及其催化性能探讨。通过湿法浸渍引入Zn物种,制备了改良型Zn/HZSM-5（25）催化剂。研究结果显示,Zn物种的引入未改变分子筛的MFI基本结构与孔隙结构,但对催化剂酸性影响较大。锌与HZSM-5沸石分子筛上Br（?）nsted酸性位点相互作用,形成新的Zn-Lewis酸性位点,使得B/L比例减小。Zn负载量对Zn物种的形成与转化有重要影响,Zn负载量较低时,Zn/HZSM-5催化剂上Zn物种主要以Zn-Lewis酸性位点的形式呈现,结构为[ZnOH]⁺与[O^-–Zn²⁺–O^-];Zn负载量较高时,则易生成ZnO物种,包括纳米ZnO团簇和大分子ZnO颗粒。以油酸甲酯（OAME）作为脂肪酸甲酯的模型物,考察催化剂裂解芳构化性能并探究反应机理。研究表明,Zn负载量较低时,总芳烃收率、单环芳烃的选择性以及催化剂的稳定性均得到提升。Zn-Lewis酸性位点的Zn物种对芳构化的促进作用体现在两方面:在烷烃活化过程中,促进烷烃脱氢活化以生成更多烯烃;在烯烃芳构化过程中,将脱氢历程由氢转移反应转变为脱氢反应,从而促进芳烃的形成。（2）锌改性催化剂0.5%Zn/HZSM-5（25）催化脂肪酸甲酯裂解芳构化性能探讨。在床层温度为515℃,载气流速为3.0 L/h,重时空速为2.5 h^-1,催化剂装填量为2.0 g的条件下,0.5%Zn/HZSM-5（25）催化剂呈现良好的原料适应性,可有效地将油脂热解酯化得到的脂肪酸甲酯（PBD）和商品化生物柴油（CBD）转化为绿色芳烃。芳烃组成分布主要为苯,甲苯和二甲苯（BTX）。积碳是催化剂失活主要原因,失活催化剂可经O₂焙烧活化再生。商品化生物柴油（CBD）的不饱和度较高,更适合催化裂解制备芳烃,催化剂有效芳构化寿命较长,再生性能更好。总芳烃收率可达42.1 wt.%,与当前脂肪酸甲酯制备芳烃的收率较高（42.6 wt.%）的工艺水平相当。（3）负载型固体酸催化剂制备及其催化裂解非食用油脂性能。通过共沉淀法制备了TiO₂-ZrO₂二元金属氧化物载体,使用硫酸浸渍制备了SO₄^2-/TiO₂-ZrO₂固体酸催化剂,并对其进行结构、酸性与各元素存在状态进行表征。结果显示,复合氧化物形成正交晶相Ti ZrO₄,酸性位点以L酸位点为主,几乎没有B酸位点。硫酸改性对载体晶型和孔隙结构几无影响,但对催化剂酸性影响较大。新的B酸位点生成,L酸位点浓度减少,有效调节了B/L比例。选用5种非食用油脂为原料,考察了固体酸催化剂的催化裂解性能。五种非食用油脂桐油（TO）、橡胶籽油（RSO）、麻风树油（JCO）、地沟油（WCO）和酸化油（WAO）,在密度、皂化值和氧含量（12–13%）等方面差异较小,但在酸值、不饱和度和脂肪酸组成上存在较大差异。无催化剂条件下直接热解,有机相液体产物（OLP）产率虽高（85 wt.%）,但主要成分为长链脂肪酸。SO₄^2-/TiO₂-ZrO₂固体酸催化剂呈现良好的油脂原料适应性。原料酸值对催化裂解过程没有影响,但原料不饱和度对催化裂解产物中含氧组分和轻质烃类含量以及芳烃占比有重要影响。催化裂解产物酸值低（<6.4 mg KOH/g）且含氧量低（<1.5%）。OLP馏分分布主要为柴油馏分（49.0–57.6%）和汽油馏分（32.0–42.5%）。OLP烃类在C6–C24范围内,主要为烯烃（44–58%）、单环芳烃（17–24%）和烷烃（14–17%）。（4）酸化油催化裂解与加氢提质。以高游离脂肪酸含量的酸化油为原料,考察反应参数对SO₄^2-/TiO₂-ZrO₂催化裂解过程的影响,并对所得富烃燃油进行Mo/TiO₂-ZrO₂催化加氢提质。在床层温度为450℃,重时空速1.0 h^-1,载气流速2.5 L/h,催化剂装填量为5.0 g的条件下,OLP收率为66 wt.%,且其酸值低（3.8 mg KOH/g）、含氧量低（1.5 wt.%）和粘度低（5.3m Pa·s）。其中,反应温度是影响催化裂解产物的主要因素。SO₄^2-/TiO₂-ZrO₂催化剂在高于400℃能实现有效脱氧同时伴随着裂解和聚合反应;500℃以上则脱氢作用明显提升,芳烃化性能增加。酸化油催化裂解所得富烃燃油经Mo/TiO₂-ZrO₂催化加氢,馏分组成与芳烃含量基本不变,但烯烃含量急剧减少。在化学组成上与石化烃类燃油更为接近,类比石油炼制,可将组分宽泛的富烃燃油按需求通过分馏制得生物质汽油,生物质航空煤油和绿色柴油等。更多还原

【Abstract】 Energy sustainability and environmental concerns are the essential driving forces in developing renewable biofuels as alternatives for traditional fossil fuels.Enormous attention has been focused on triglycerides,such as non-edible vegetable oils and waste oils as abundant biomass resources for the generation of biofuels.The key advantages of triglyceride feedstocks involve ready fluidity,high energy density and similar molecular structure with fossil fuels.However,straight vegetable oil was treated as an undesirable fuel for automotive applications as it has the high kinematic viscosity.Pyrolysis and transesterification are two fundamental strategies for decreasing the viscosity of triglycerides.The typical resulting products are known as bio-oil and biodiesel,respectively.However,these biofuels with oxygenated compounds suffered from their poor compatibility with fossil fuels.Catalytic cracking is considered as the most promising approach to convert triglycerides and their derivatives into oxygen-free biofuels,namely,hydrocarbon-rich biofuels,which are fully miscible with the traditional fossil fuels.In the present dissertation,we investigated catalytic aromatization of fatty acid methyl esters for the production of renewable aromatics and catalytic cracking of triglycerides for the production of hydrocarbon-rich biofuels over a series of solid acid catalysts including their preparation,characterizations,performance test and corresponding reaction mechanisms.Some conclusions drawn from this work are provided as follows:（1）Preparation and catalytic performance of Zn-modified HZSM-5 zeolite catalysts.The Zn/HZSM-5（25）catalysts were prepared using a wet impregnation method.The introduction of Zn species shows less effect on the MFI framework and pore structure of zeolite support.However,many Br（?）nsted acid sites are preferentially consumed while a new kind of Zn-Lewis acid site is generated,thereby reducing the B/L ratio.The existing state of Zn species on HZSM-5 zeolites is heavy depended on the amount of Zn loading.At a lower Zn loading,the Zn species are present as[ZnOH]⁺and Zn²⁺species,which are Zn-Lewis acid sites;At a higher Zn loading,the ZnO species would be formed including ZnO nanoclusters and large ZnO particles.Oleic acid methyl ester（OAME）is selected as a model of fatty acid methyl ester（FAME）and used to study the mechanism of the aromatization.It was found that the catalysts with lower Zn loading give high yield of aromatics and high selectivity of monocyclic aromatics,and the stability of catalysts is improved.The Zn-Lewis acid sites show great promotion on the generation of aromatics.They not only enhanced the dehydrogenation activation of alkanes to form more alkenes but also shifted the further dehydrogenation process from hydrogen transfer reactions to dehydrogenation reactions during aromatization of alkenes,therefore improving the production of aromatics.（2）Catalytic performance of 0.5%Zn/HZSM-5（25）catalyst on aromatization of FAMEs.During catalytic cracking of FAMEs at 515℃,3.0 L/h of carry gas flow rate,2.5 h^-1 of weight hourly space velocity（WHSV）,and 2.0 g of catalyst loading,the 0.5%Zn/HZSM-5（25）catalyst exhibits good adaptability to different biodiesel samples and shows a good ability to convert biodiesel produced from pyrolysis（PBD）and commercial biodiesel（CBD）into green aromatics.The distribution of aromatic hydrocarbons was mostly benzene,toluene and xylene（BTX）.The deactivation of the 0.5%Zn/HZSM-5（25）catalyst can impute to coking and the spent catalyst can be regenerated by calcining in the presence of oxygen.CBD with higher degree of unsaturation shows an excellent performance for the production of green aromatics,which represents a longer service lifetime and better regeneration property.The yield of total aromatic hydrocarbons（TAH）is 42.1 wt.%,which is comparable with the high yield of aromatics（42.6 wt.%）obtained from current process of FAME aromatization.（3）Preparation of SO₄^2-/TiO₂-ZrO₂ catalyst and its catalytic performance on catalytic cracking of non-edible oils.The binary oxide TiO₂-ZrO₂ was prepared using a coprecipitation method,which results in the formation of orthorhombic Ti ZrO₄ structure.The acid sites on the binary oxide are mainly Lewis acid sites.The modification of sulfuric acid has less effect on crystal shape and pore structure.However,the concentration of acid sites changes significantly.New Br（?）nsted acid sites appear while the Lewis acid sites reduce,which leads to a decrease in B/L ratio.Five non-edible oils,tung oil（TO）,rubber seed oil（RSO）,Jatropha curcas oil（JCO）,waste cooking oil（WCO）and waste acidified oil（WAO）were selected as triglyceride feedstocks.They show little differences in density,saponification value,and oxygen content（12–13%）,while they vary significantly in terms of acid number,the degree of unsaturation,and composition of fatty acids.Direct pyrolysis of triglycerides without a catalyst gives a high yield ofOLP（85 wt.%）,which contains a large sum of free fatty acids.In case of catalytic cracking of triglycerides,SO₄^2-/TiO₂-ZrO₂ catalyst exhibits good feedstock adaptability.The acid number shows less effect on the catalytic cracking process,while the unsaturated double bonds tend to favor the formation of lighter alkenes and more aromatics.The hydrocarbon-rich biofuels have low acid number（<6.4 mg KOH/g）and low oxygen content（<1.5%）,which are mostly consist of diesel fraction（49.0–57.6%）and gasoline fraction（32.0–42.5%）.The hydrocarbons are in the range of C6–C24,including alkenes（44–58%）,monocyclic aromatics（17–24%）and alkanes（14–17%）.（4）Catalytic cracking of waste acidified oil and upgrading of biofuels by catalytic hydrogenation.Waste acidified oil is selected for investigating the effects of reaction parameters on catalytic cracking process,and subsequently the biofuels produced is further upgraded by catalytic hydrogenation using a Mo/TiO₂-ZrO₂ catalyst.The optimized catalytic cracking process is carried out at 450℃,2.5 L/h of N₂ flow rate,1.0 h^-1 of WHSV,and 5.0 g of catalyst loading,which results in a high yield ofOLP（66 wt.%）with a low acid value（3.8 mg KOH/g）,low oxygen content（1.5 wt.%）and low kinematic viscosity（5.3 m Pa·s）.The reaction temperature plays an important role in catalytic cracking process.The efficient deoxygenation occurs at temperatures above 400℃and is accompanied by cracking and oligomerization.The high temperature（≥500℃）generally initiates secondary cracking and subsequently tends to favor dehydrogenation and aromatization.Catalytic hydrogenation of biofuel over the Mo/TiO₂-ZrO₂catalyst has little change on the fraction distribution and aromatics content,but the content of olefins was sharply reduced by 34%.The upgraded hydrocarbon-rich biofuel was more chemically near-identical to petroleum-based fuels and can be fractionated and used in different formulations depending on the type of desired fuels,such as bio-gasoline,bio-jet fuel and green diesel.更多还原