动植物油脂加氢制备生物燃油催化剂研究进展

在全球石油资源日益紧缺,环保要求日益严苛的情况下,以动植物油脂为原料通过催化加氢来制备生物燃油的研究方向备受关注。然而,能否经济、高效地将动植物油脂转化为生物燃油,催化剂是关键。因此,开发具有高活性、高选择性的催化剂成为该研究方向的重点。通过对动植物油脂加氢制备生物燃油的各类催化剂进行综述,总结了不同类型催化剂所具有的特点,并认为贵金属催化剂可使动植物油脂转化按照加氢、脱羧、裂化、异构化的反应途径进行的多功能催化剂,但基于其加氢脱氧转化率不高,裂化异构化性能不足等问题,认为可以通过载体改性、贵金属负载方式改进以及进行孔道修饰等来提高催化剂的加氢脱氧活性以及对轻质烷烃和异构化烷烃的选择性。     

酯交换反应在制备生物柴油上的应用

生物柴油因其环境友好且可再生作为矿物柴油的替代燃料而备受关注,生物柴油主要通过均相酸碱催化、脂肪酶催化、超临界法和固体酸碱催化的酯交换反应制备得到,但各种制备方法各有优劣,均相酸碱催化法反应迅速,转化率高但存在后续处理复杂,污染严重等问题;脂肪酶催化法反应条件温和,对原料中的水和游离脂肪酸不敏感,不需要过量的甲醇参与反应,后续处理工序简单,但酶的成本过高,这是制约其商业化发展的最大阻碍;超临界法是制备生物柴油的新技术,反应迅速,不需要催化剂,油脂转化率非常高,但其反应需要高温高压且能耗很大;固体酸碱催化剂腐蚀性小可以重复使用,后续分离工序简单,对环境的冲击较弱。其中负载型固体碱催化剂催化油脂酯交换反应将成为制备生物柴油的一个主要发展方向。     

稻壳基活性炭负载镍催化剂的制备及在香草醛加氢脱氧反应中的催化性能

以稻壳活性炭作为碳源,硝酸镍为金属前驱体,采用浸渍法结合碳热还原和催化石墨化的方法制备了具有良好香草醛加氢脱氧催化性能的稻壳基活性炭负载镍催化剂。在催化剂的制备过程中,稻壳活性炭作为金属前驱体的还原剂,金属镍作为稻壳活性炭催化石墨化的催化剂。以生物油模型化合物香草醛加氢脱氧制备4-甲基愈创木酚为探针反应,考察制得催化剂的加氢脱氧反应性能。采用X射线衍射、高分辨透射电镜、拉曼光谱仪、氮气吸附仪等手段对催化剂中Ni的价态、粒径和分散情况,石墨化程度、比表面积、孔径等进行表征。结果表明,催化剂的结构和其催化性能存在密切联系。随着碳热还原温度的升高,催化剂的催化活性出现了先降低而后提高的趋势。这是由于较高的碳热还原温度引起镍纳米粒子的聚集和长大,不利于其催化性能;同时较高的碳热还原温度促使催化剂石墨化程度的提高,对其催化性能起到促进作用。     

固体酸催化剂在制备生物柴油中的进展

生物柴油是环境友好的替代燃油,由天然油脂与低级醇通过酯交换反应制备。采用固体酸催化剂制备生物柴油较为简单,同样适用于低等级、高度酸性以及含有水的油的酯化和酯交换反应,且不形成皂化物,还可以有效避免传统均相酸碱催化酯交换工艺中存在的产品分离困难和废催化剂的二次污染问题。研究非均相固体酸催化剂在生物柴油生产中的应用,对于正在兴起的中国生物柴油产业具有重要的意义。详细介绍了各种固体酸,包括硫酸化的金属氧化物、磺酸离子交换树脂、磺酸改性的介孔二氧化硅材料、磺化碳基催化剂、杂多酸和酸性离子液体作为酯化和酯交换反应中的非均相催化剂的研究进展。     

碳基固体酸催化大豆油酯交换制备生物柴油

通过一步碳化-磺化法制备了碳基固体酸催化剂,采用IR、XRD以及TG对催化剂进行了表征;并将催化剂用于催化大豆油与甲醇的酯交换反应制备生物柴油中,考察了相关因素对反应的影响,用气相色谱分析生物柴油的产率。实验结果表明,碳基固体酸催化大豆油与甲醇的酯交换反应效果显著,最佳反应条件为:醇油摩尔比36∶1、反应温度130℃、反应时间4h、催化剂用量为大豆油质量的10%时,生物柴油的收率可达95.5%。催化剂重复利用6次,活性下降较小。     

Lewis酸性离子液体催化文冠果种仁油制备生物柴油

以盐酸三乙胺和不同金属氯化物FeCl3,CuCl2,SnCl2,ZnCl2为原料,合成了一系列Lewis酸性离子液体[Et3NH]Cl/MClX,将其用于催化文冠果种仁油和甲醇酯交换制备生物柴油。考察了离子液体的种类,反应温度,醇油摩尔比,催化剂用量和反应时间对生物柴油产率的影响。结果表明:在反应温度为70℃,醇油摩尔比为12,催化剂用量为原料油质量的5%,反应时间7h时,离子液体[Et3NH]Cl-2FeCl3催化酯交换制备生物柴油的产率可达95.4%。[Et3NH]Cl-2FeCl3具有较好的循环使用能力,循环使用6次后,催化性能没有明显降低。制备的生物柴油各项指标符合生物柴油国家标准GB/T20828-2007。     

生物柴油生产现状及技术进展

生物柴油是以含油植物、动物油脂以及废食用油为原料制成的可再生清洁能源。生物柴油合成采用比较简单的酯基转移反应(反酯化),只需油、醇和催化剂,醇类现多选用甲醇,可使植物油与醇类生成酯类并联产丙三醇(甘油)。反酯化工艺基于碱催化或酸催化,碱催化反酯化优于酸催化,过程转化率高(大于98%),在常压(0.14MPa)和低温(约66℃)下进行,可直接转化无中间步骤。世界各国生产生物柴油所用的原料不尽相同,美国使用大豆籽和动物脂肪,欧洲使用油菜籽和动物脂肪,日本使用动物脂肪,马来西亚使用椰子油籽,印度使用非食用植物油。欧洲和北美利用过剩的…     

玉米粉炭基固体酸催化剂的制备及表征

通过炭化-磺化的方法,以玉米粉为原料,制备了玉米粉炭基固体酸催化剂,并催化油酸与甲醇酯化反应制备生物柴油。通过XRD、FE-SEM、FT-IR对催化剂表征,实验结果证明,经过不完全炭化和磺化过程生成的为磺酸基负载的芳香族炭结构的化合物。通过单因素和正交试验得出该催化剂的最优制备条件为450℃,炭化恒温时间2h,磺化温度140℃,磺化时间3h,此催化剂催化的酯化反应转化率高达72.04%。     

木质素热解中CO和CO2形成机理的理论研究

采用密度泛函理论方法(B3LYP)对含苯基的各种木质素模型化合物的脱羰基反应和脱羧基反应进行了理论研究。设计了8种模型化合物 R1-R8的8条脱羰基反应路径(1)-(8)和8种模型化合物 R9-R16的8条脱羧基反应路径(9)-(16)。计算了不同温度下各热解反应途径的标准热力学和动力学参数。计算结果表明,反应路径(1)-(4)的脱羰基反应能垒明显高于反应路径(5)-(8),CO 更可能通过苯基(对羟苯基、愈创木基和紫丁香基)乙醛的脱羰基反应而形成;反应路径(9)-(12)的脱羧基反应能垒低于反应路径(13)-(16),CO2的形成更可能通过苯基(对羟苯基、愈创木基和紫丁香基)甲酸的脱羧基反应而完成。     

介孔材料在生物柴油合成中的应用

生物柴油是一种绿色可再生能源,一般是通过酸或碱催化酯化或酯交换反应来制备。综述了介孔金属氧化物、介孔分子筛及介孔磷酸盐等不同类型介孔材料催化剂用于制备生物柴油的研究进展,并对制备生物柴油的介孔催化剂研究方向进行展望。     

酸处理对FeN/ZIF-8催化剂氧还原反应催化性能的影响

研发高性能、低成本的非贵金属阴极氧还原反应催化剂是目前质子交换膜燃料电池的主要研究方向之一。以1, 10-菲啰啉为氮源, FeSO₄·7H₂O为铁源, 考察以ZIF-8为载体制备的FeN/ZIF-8催化剂的氧还原反应催化性能, 并探究酸处理对FeN/ZIF-8催化剂结构及性能的影响。通过X射线衍射、比表面积和孔径分布测试、透射电子显微镜等物理表征手段对催化材料进行结构表征, 使用旋转圆盘电极对催化剂氧还原反应催化活性和稳定性进行测试。结果表明: 以ZIF-8为载体制备的催化剂含有Fe₃C, 以及具有较大的比表面积, 这可能是催化剂具有较高氧还原反应初始催化活性的原因。酸处理可去除催化剂中部分不稳定的含铁碳化物和无序碳结构, 使催化剂具有更大的比表面积、更丰富的介孔结构和更高的孔体积; 同时, 酸处理可提高碳基体的耐腐蚀性, 在老化测试中维持催化剂所具有的较高比表面积和丰富的介孔结构, 从而使FeN/ZIF-8-A催化剂表现出更好的氧还原反应活性和稳定性。     

负载型MoO3／β分子筛催化剂的丙烷氧化脱氢性能

以β分子筛为载体,采用浸渍法负载钼制备了MoO3／β筛催化剂,通过XRD、FTIR、BET、NH3-TPD进行表征,结果表明,样品中有活性组分氧化钼存在,也有不同酸性质的活性位存在,负载量对催化剂的表面积和孔径有影响;考察了催化剂对丙烷氧化脱氢制丙烯的催化性能,结果表明,单纯β分子筛载体有催化活性,不同钼负载量对催化性能有影响,考察负载量区间内反应转化率出现极值。     

甲烷干气重整镍基复合结构催化剂的研究进展

甲烷干气重整反应能够实现温室气体CO₂和CH₄的转化利用, 其反应产物合成气可以通过费托反应进一步生产液态燃料, 该反应在能源与环境领域具有重要意义。寻找合适的催化剂是推动甲烷干气重整工业化的关键。镍基复合结构催化剂因其与贵金属催化剂相媲美的催化活性和低廉的工业成本而受到广泛关注, 但镍基催化剂存在高温下长时间反应后碳沉积和金属组分烧结所导致的失活问题, 严重影响了其工业应用和干气重整化工的发展。本文从镍基复合结构催化剂的成分、结构、制备方法及模拟计算设计等方面出发, 介绍了改进镍基催化剂活性、抗积碳和抗烧结性能的研究进展, 并结合最新的原子催化以及原位表征等研究进展对干气重整研究的发展趋势进行 展望。     

Defect-rich MoS<Subscript>2</Subscript> nanowall catalyst for efficient hydrogen evolution reaction

Designing efficient electrocatalysts for the hydrogen evolution reaction (HER) has attracted substantial attention owing to the urgent demand for clean energy to face the energy crisis and subsequent environmental issues in the near future.Among the large variety of HER catalysts,molybdenum disulfide (MoS2) has been regarded as the most famous catalyst owing to its abundance,low price,high efficiency,and definite catalytic mechanism.In this study,defect-engineered MoS2 nanowall (NW) catalysts with controllable thickness were fabricated and exhibited a significantly enhanced HER performance.Benefiting from the highly exposed active edge sites and the rough surface accompanied by the robust NW structure,the defect-rich MoS2 NW catalyst with an optimized thickness showed an ultralow onset overpotential of 85 mV,a high current density of 310.6 mA·cm-2 at η =300 mV,and a low potential of 95 mV to drive a 10 mA.cm-2 cathodic current.Additionally,excellent electrochemical stability was realized,making this freestanding NW catalyst a promising candidate for practical water splitting and hydrogen production.     

非贵金属/碳氮复合材料电催化析氧反应的研究进展

析氧反应(OER)是一种复杂的四电子转移反应,其动力学缓慢、所需能量高,制约了电解水制氢等新型能源技术的发展.近年来,非贵金属复合材料因其优异的催化活性以及相比于贵金属基催化剂的成本优势而受到广泛关注.本文概述了这一研究领域的最新进展,首先简要介绍析氧反应的机理以及材料催化性能的评价方法,重点关注非贵金属/碳氮复合材料...     

Synthesis and characterization of catalysts produced from paper mill sludge. I. Determination Of NOx removal capability

Characteristics and catalytic properties of a series of carbon-based catalysts (CBCs) produced from paper mill sludge were evaluated. The major processes involved in the production of the catalysts were chemical activation, impregnation, pyrolysis, and post pyrolysis rinsing. The porous structure, catalytic activity and thermostability of the catalysts were tailored during the production stage by introducing hetero-atoms (zinc chloride, and ferric nitrate) in the carbon structure. Characterization of the produced CBCs included determination of the surface area, pore size, and pore size distribution (PSD) from standard N₂-adsorption isotherm data. The extent of graphitization and the presence of metal crystals were identified from X-ray diffraction (XRD). The limit of the catalyst gasification was estimated from thermogravimetric analysis (TGA) conducted in an oxidized environment. The NO_x reduction capability of the produced catalysts was evaluated in the presence of carbon monoxide using a fixed bed reactor. The reaction temperature ranged from 300 to 500°C. It was shown that paper mill sludge is an excellent precursor for the production of CBCs with NO_x removal capability of 66–94%. The catalytic capability of the produced CBCs varied according to the method of production, catalyst surface properties (surface area, pore structure, PSD), metal composition and reaction temperature. The highest NO_x removal capacity was observed for the catalytic reactions carried out at 400°C. The mesoporous catalyst produced with a Zn:Fe molar ratio of 1:0.5 exhibited the maximum NO_x removal catalytic activity of 94%.     

Nitrate reduction in water: influence of the addition of a second metal on the performances of the Pd/CeO(2) catalyst

An attempt is made to improve the catalytic nitrate reduction on Pd/CeO(2) catalysts by the addition of a second metal. The influence of the second metal such as Sn, In and Ag on the Pd/CeO(2) for nitrate reduction is explored. The second metal is introduced over monometallic Pd/CeO(2) by a redox reaction. Pd/CeO(2) is more active than the bimetallic catalysts under pure hydrogen flow. Whereas in presence of CO(2) the monometallic Pd/CeO(2) is inactive for nitrate reduction, bimetallic catalysts are found to be more active than under pure hydrogen flow and also than the monometallic catalyst with a low selectivity towards ammonium ions, undesired product of the reaction. The Pd-Sn/CeO(2) catalyst is comparatively the most suited for nitrate reduction.     

Weyl Semimetals as Hydrogen Evolution Catalysts

The search for highly efficient and low‐cost catalysts is one of the main driving forces in catalytic chemistry. Current strategies for the catalyst design focus on increasing the number and activity of local catalytic sites, such as the edge sites of molybdenum disulfides in the hydrogen evolution reaction (HER). Here, the study proposes and demonstrates a different principle that goes beyond local site optimization by utilizing topological electronic states to spur catalytic activity. For HER, excellent catalysts have been found among the transition‐metal monopnictides—NbP, TaP, NbAs, and TaAs—which are recently discovered to be topological Weyl semimetals. Here the study shows that the combination of robust topological surface states and large room temperature carrier mobility, both of which originate from bulk Dirac bands of the Weyl semimetal, is a recipe for high activity HER catalysts. This approach has the potential to go beyond graphene based composite photocatalysts where graphene simply provides a high mobility medium without any active catalytic sites that have been found in these topological materials. Thus, the work provides a guiding principle for the discovery of novel catalysts from the emerging field of topological materials.     

Nitrogen-doped graphite encapsulated Fe/Fe_3C nanoparticles and carbon black for enhanced performance towards oxygen reduction

Non-noble metal(NNM) catalysts have recently attracted intensive interest for their high catalytic performance towards oxygen reduction reaction(ORR) at low cost.Herein,a novel NNM catalyst was synthesized by the simple pyrolysis of carbon black,urea and a Fe-containing precursor,which exhibits excellent ORR catalytic activity,superior durability and methanol tolerance versus the Pt/C catalyst in both alkaline and acidic solutions.Scanning electron microscopy(SEM),transmission electron microscopy(TEM) and X-ray diffraction(XRD) characterizations demonstrate that the product is a nitrogen-doped hybrid of graphite encapsulated Fe/Fe_3C nanoparticles and carbon black.X-ray photoelectron spectrum(XPS) and electrochemical analyses indicate that the catalytic performance and chemical stability correlate closely with a nitrogen-rich layer on the Fe/Fe_3C nanoparticle after pyrolysis with presence of urea,leading to the same four-electron pathway towards ORR as the Pt/C catalyst.The hybrid is prospective to be an efficient ORR electrocatalyst for direct methanol fuel cells with high catalytic performance at low cost.