HZSM-5在线提质生物油及催化剂失活机理分析

对不同使用时间的HZSM-5分子筛在线催化提质制取的生物油进行理化特性和成分分析,从生物油品质角度对HZSM-5的催化性能进行评价;并采用TG、BET、XRD、SEM和TEM等方法对失活的HZSM-5催化剂进行表征分析,探讨了HZSM-5催化提质生物油的失活机理,并进行再生研究。研究表明,HZSM-5分子筛可转化生物油中的酸类、醛类和酮类等"非期望"有机物,生成较多"期望"有机物,如酚类和芳烃类物质,降低生物油的氧含量及酸性,提高生物油的热值;HZSM-5使用80 min后,生物油品质明显变差,催化剂活性明显降低;失活催化剂上沉积的焦炭主要呈纤维状,同时,还存在少量石墨状焦炭,焦炭总量达14.12%,且使用过程中催化剂的比表面积和孔容均下降,晶粒的团聚现象加剧,结晶度下降;在催化提质过程中,在孔道内生成的石墨状焦炭及在表面形成的纤维状焦炭大量覆盖活性位点,使得催化剂失活。经550℃再生后,催化剂可恢复催化性能。     

PtZn-Sn/SBA-15合成、表征及对丙烷催化脱氢性能

以SBA-15为载体,利用浸渍法制备了单、双和三金属Pt催化剂,并对催化剂进行了N2物理吸附(BET)、程序升温还原(H2-TPR)、H2-化学吸附、透射电子显微镜(TEM)和O2-脉冲等技术表征,研究了它们对丙烷催化脱氢(CDH)制丙烯反应的催化性能。研究结果表明,Pt在三金属催化剂中的分散性能最好,并且部分负载组分可以进入SBA-15的孔道,Pt的分散度达到29%,Pt粒子尺寸为3 nm左右。三金属催化剂表现出优越的脱氢性能,这主要归结于载体的弱酸性、活性组分和助剂、载体之间的相互作用及Zn对Pt的电子调控作用。这些因素使催化剂的积炭量较低,因而具有较高的脱氢稳定性和极高的选择性。     

大孔FCC催化剂的制备及裂化性能研究

利用聚苯乙烯(PS)颗粒和脱油残渣(VR)乳液为模板剂制备了大孔重油催化裂化催化剂,与未加模板的参比催化剂相比,比表面积分别增加了38.0%和46.2%,孔体积分别增加了20.6%和35.8%,平均孔径分别增加了54.5%和27.3%。微反评价结果表明,大孔催化剂活性较高,对重油的转化率分别提高了9.8%和12.2%,总液收分别提高了10.2%和7.3%。与参比催化剂相比,积炭后PS颗粒和VR乳液模板大孔催化剂的活性有一定程度的降低,但是当积炭量相同时,大孔催化剂的重油转化率和总液体产物收率都比参比催化剂要高,且两类大孔催化剂的数据比较接近。催化剂的基质经模板扩孔后,由于具有微孔-介孔-大孔的梯度孔分布,孔径分布更加合理,重油分子在催化剂孔道内的扩散速率更快,容炭能力更强,所以大孔催化剂具有较好的裂化性能。     

Preparation of tantalum-pillared magadiite and its catalytic performance in Beckmann rearrangement

Vapor phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam has been carried out using tantalum-pillared magadiites (Ta-magadiites) with different surface areas as catalysts. The Ta-magadiite catalysts of relatively large surface areas showed high catalytic activities, due to a large number of active sites. For the Ta-magadiite catalyst of the largest surface area, the oxime conversion reached 99.1%, with 97.5% of lactam selectivity. FT-IR and NH₃-TPD results demonstrated that the new hydroxyl groups and a large amount of acidic sites generated by Ta pillaring into the magadiite interlayer were responsible for the high catalytic performance of Ta-magadiite catalyst.     

不同晶粒尺寸H-ZSM-5催化剂上甲醇芳构化反应性能

芳烃是一类重要的有机化工基础原料,通常采用传统的石油路线生产芳烃,包括催化裂化和催化重整等工艺.由于石油资源的紧缺,以可再生资源为原料生产芳烃工艺的发展具有十分重要的意义.甲醇作为一种重要的基础原料,可来源于煤、天然气和生物质等,因此,甲醇制芳烃工艺(MTA)的研究受到日益关注.ZSM-5分子筛具有较大的比表面积、可调节的酸性、优良的择形选择性和很高的水热稳定性,因而在甲醇芳构化中展现出良好的催化性能.研究发现,甲醇转化率和产物分布与ZSM-5分子筛的酸性和多孔性等密切相关.本文通过调控模板剂与水的比例和晶化时间,采用水热法制备了一系列不同晶粒度H-ZSM-5分子筛催化剂,通过X射线衍射(XRD)、扫描电镜(SEM)、N2物理吸附脱附(BET)和X射线荧光光谱等技术对所得分子筛的理化性质、骨架结构和形貌进行了表征;采用吡啶红外光谱和NH3程序升温脱附技术对其酸性进行了分析,使用热重(TG)技术对反应后催化剂的积碳含量进行了分析,并将所制备的H-ZSM-5分子筛催化剂分别应用于MTA反应,系统性地探究分子筛晶粒度对其理化性质和MTA催化性能的影响.XRD结果表明,所合成的五种样品均具有典型的ZSM-5分子筛特征衍射峰且无杂晶,且具有不同的晶粒度,分别为4.0±0.3,1.2±0.2 μm,614.1±31.9、391.9±32.4和99.1±7.0 nm.N2物理吸附脱附曲线可以发现,晶粒度为99.1±7.0 nm的ZSM-5分子筛展现出典型的Ⅰ型和Ⅳ型物理吸附曲线且在较高的相对压力(P/Po=0.8-1.0)处有一个明显的H4型迟滞环,表明此分子筛具有介孔和大孔结构;BJH吸附孔径分布图表明,这些介孔主要分布在2-7和20-50 nm范围内;同时各样品的比表面积和孔体积随着其晶粒度的减小而增大.结果还表明五种不同晶粒度的ZSM-5分子筛具有相似的SiO2/Al2O3摩尔比和酸性质.MTA反应结果表明,随着催化剂晶粒度的降低,甲醇的平均转化率,芳烃选择性和BTX选择性有所提高,在300 min时晶粒度较大的三个催化剂上,甲醇转化率迅速降至90％,而晶粒度较小的两个催化剂上,甲醇转化率始终维持在95％以上,其中晶粒度为99.1±7.0 nm的样品上芳烃选择性最高(平均42％以上),BTX选择性达37％.对失活催化剂积碳含量分析,随着催化剂晶粒度的降低,积碳量降低.晶粒度较低的纳米分子筛催化剂具有更短的孔道,更高效的扩散性能,更高的比表面积和独特的梯级孔结构,因而在甲醇芳构化反应中展现出更长的寿命,更高的活性和更低的积碳量,在甲醇制芳烃工业化生产中具有巨大潜力.     

Temperature-programmed oxidation of equilibrium fluid catalytic cracking catalysts

Characterization of coke on equilibrium, fluid catalytic cracking (FCC) catalysts contaminated with metals was investigated using temperature-programmed oxidation (TPO). TPO spectra of spent equilibrium catalysts from cracking of sour imported heavy gas oil (SIHGO) were deconvoluted into four peaks (Peak K, L, M and N). The four peaks were assigned to different types of coke on the catalyst. Peak L in the TPO spectrum was assigned to the 'contaminant' coke in the vicinity of metals. The amount of contaminant coke (Peak L) correlates with metal-contaminant concentration. The size of Peak L which is related to amount of contaminant coke decreased significantly for the spent highly contaminated catalyst pretreated with hydrogen and methane prior to cracking reactions as compared to the non-pretreated catalysts. Since both hydrogen and methane pretreatment can reduce oxidation state of the vanadium that present at high concentrations on the equilibrium catalysts the decrease in the amount of contaminant-coke represented by Peak L was explained by the reduction of the oxidation state of vanadium. Less contaminant coke was produced after the equilibrium catalysts were pretreated using hydrogen and methane gases since reduced vanadium has lower dehydrogenation activity compared to oxidized vanadium. This revised version was published online in August 2006 with corrections to the Cover Date.     

Catalytic cracking of polyethylene over nanocrystalline HZSM-5: Catalyst deactivation and regeneration study

In this work, catalytic cracking of low density polyethylene (LDPE) over nanocrystalline HZSM-5 zeolite in a batch reactor at 340 °C was carried out with the aim of study both the catalyst resistance to deactivation and the catalyst regeneration process. For looking into the catalyst deactivation, consecutive polyethylene cracking experiments were carried out. Subsequently, the same reactions has been also performed but by regenerating the zeolite after each experiment by promoting coke combustion at 550 °C under air flow. Zeolites used were two samples of nanocrystalline HZSM-5 with very different textural properties (sample A, with most of its surface corresponding to zeolitic micropores and sample B with a considerable amount of external surface, mesopores and super-micropores) in order to study the effect of their textural properties in the deactivation and regeneration experiments. Although conversion and activity values reached over both samples are quite high taking into account the mild conditions used, sample B shows a very much higher initial activity than A due to its improved textural properties. In both samples two different deactivation mechanisms occur: a reversible deactivation by coke deposition removable by the regeneration procedure, and an irreversible or permanent deactivation by other factors. Deactivation of sample B occurs faster due to the higher amount of coke deposited on this material. However, the improved textural properties of this catalyst supposes an advantage for the regeneration process, since coke deposited either on the external surface or on the super-micropores and mesopores, makes easier the regeneration procedure.     

Co/Al2O3催化剂上积炭的研究

甲烷的二氧化碳重整制合成气是近年来甲烷催化转化的一个重要方面,而所用催化剂的积炭问题仍是影响催化剂活性和寿命的主要因素之一．近年来,对催化剂表面的积炭形式有一些报道［１］,但对积炭的种类及其与催化剂活性的关系很少有报道．本文从经低温焙烧的Ｃｏ／Ａｌ２...     

改性beta分子筛催化苯和甲醇制甲苯反应的研究

我们主要对beta型分子筛进行碱处理、酸处理、离子交换改性以及碱土金属的负载,来比较不同催化剂催化苯和甲醇烷基化制甲苯的催化性能,使用鼓泡式进料,在低能耗条件下,系统地考察了不同反应条件对该反应的影响.采用N_2-吸脱附、X-射线衍射分析、扫描电镜、热重分析等表征手段对催化剂晶相及表面酸性等进行表征.研究表明:beta分子筛先经弱酸于70℃下处理1 h,然后再经铵离子交换多次,最终负载碱土金属La,所制得的催化剂积炭量有效降低,且催化性能良好.收率大小顺序为:La-H-betaH-betabetaOH-beta.     

完全液相法中Cu源对Cu-Zn-Al催化剂结构及性能的影响

采用完全液相法,分别以柠檬酸铜、硝酸铜、乙酸铜为Cu源制备了三种Cu-Zn-Al浆状催化剂,考察了不同铜源对催化剂催化合成气制二甲醚性能的影响,利用XRD、H2-TPR、NH3-TPD、BET、XPS和TEM等技术对催化剂进行了表征。结果表明,铜源对催化剂织构形貌及性能影响显著,用柠檬酸铜为铜源制备的催化剂铜物种分散性最好,铜物种与其他组分间相互作用强,可还原物质的量多,同时催化剂表面弱酸量与强酸量的比较高,催化剂的甲醇脱水能力提升,三种催化剂中柠檬酸铜催化剂性能最好,CO转化率为63.4%,二甲醚选择性为66.0%。     

Effects of CO2 content on the activity and stability of nickel catalyst supported on mesoporous nanocrystalline zirconia

The effects of carbon dioxide content on the catalytic performance and coke formation of nickel catalyst supported on mesoporous nanocrystalline zirconia with high surface area and pure tetragonal crystalline phase were investigated in methane reforming with carbon dioxide. The samples were characterized by XRD, BET, TPR, TPO, TPH, TEM, and SEM techniques. The catalyst prepared showed high surface area and a mesoporous structure with a narrow pore size distribution. The obtained results revealed that the increase in CO2 content increased the methane conversion and stability of the catalyst and significantly reduced the coke deposition. The TPH analysis showed that several species of carbon with different reactivities toward hydrogenation were deposited on the spent catalysts employed under different CO2 contents.     

在杂多酸催化剂上苯和1-十二烯烷基化合成十二烷基苯

对不同ＳｉＯ２负载磷钨酸（ＰＷ）催化剂的表面性质、热稳定性、酸性、以及对苯与丙烯和１－十二烯的烷基化反应的催化活性进行了对比研究,结果表明,ＰＷ在ＳｉＯ２上的分散状况与ＳｉＯ２的比表面积和孔径大小有关,ＰＷ与载体表面作用的强弱会直接影响负载型催化剂的热性和酸性,采用不同的ＳｉＯ２可以制得比表面积、孔结构和酸强度不同的负载型ＰＷ催化剂,以满足不同催化反应的要求。     

Doping effects of manganese on the catalytic performance and structure of NiMgO catalysts for controllabe synthesis of multi-walled carbon nanotubes

Doping effects of manganese （Mn） on catalytic performance and structure evolution of NiMgO catalysts for synthesis of multi-walled carbon nanotubes （MWCNTs） from methane were investigated for the first time. Addition of Mn in NiMgO catalyst can greatly improve the MWCNTs yield. Mno.2NiMgO catalyst among the tested ones gives the highest MWCNTs yield as 2244%, which is two times higher than that of the catalyst without Mn. The structure evolution, reduction behaviors and surface chemical properties of MnNiMgO catalysts with various Mn contents were studied in detail. It was found that the stable solid solution of NiMgO2 formed in NiMgO catalyst was disturbed by the addition of Mn. Instead, another solid solution of MnMg608 is formed. More amount of Ni can be reduced and dispersed on the catalyst surface to be acted as active sites. Importantly, the changes of Ni content on the surface are correlated with the Ni particle size and the outer diameter of MWCNTs, suggesting the controllable synthesis of MWCNTs over MnNiMgO catalysts.     

碱金属钾对Ni基催化剂纤维素水蒸气气化活性的影响

采用两段式催化气化方式研究了生物质热解气化过程中碱金属的挥发对Ni基催化剂活性的影响。实验结果表明,负载K盐的纤维素水蒸气催化气化过程中,K挥发后会在催化剂表面沉积,而少量K的存在和表面沉积不但能够提高镍基催化剂的抗积炭能力,而且有助于提高其催化活性,产生更多的氢气。然而纤维素中K的浓度过大,将会抑制Ni基催化剂的效果;K在催化剂上的沉积随催化剂循环次数的增加而增加,K的含量愈高,对催化剂的抑制效果愈明显,从而缩短了催化剂的使用寿命。     

高硅ZSM-5原粉的外表面改性及其在甲醇制丙烯反应中的应用

使用来源广泛的甲醇为原料制取丙烯, 是对石油路线生产丙烯的重要补充. 尽管以ZSM-5分子筛为催化剂的固定床甲醇制丙烯(MTP)技术已经实现了工业应用, 但进一步提高催化剂的寿命和丙烯的选择性一直是学术界和工业界的研究热点. MTP过程作为典型的酸催化反应, 积碳是催化剂失活的主要原因, 由于ZSM-5分子筛十元环孔道的空间限制作用, 积碳主要分布在外表面. 因此, 消除外表面的酸性位点对延长催化剂的寿命至关重要, 但修饰外表面酸性位点的同时往往会改变样品的其他性质, 如孔径、整体酸量等. 本文分别使用Na2H2EDTA和H3PO4处理高硅ZSM-5分子筛原粉(微孔内含有机模板剂)来选择性地减小或消除外表面的酸密度, 而不影响分子筛内部的性质, 并考察了处理后样品的MTP性能. 使用N2物理吸附、SEM和27Al MAS NMR表征样品的织构性质、形貌和Al原子的化学环境, XPS和三异丙苯裂解实验表征外表面的硅铝比和酸密度. 表征结果表明, Na2H2EDTA处理虽然可以选择性的脱除表面Al原子, 但会在外表面产生新的酸点(可能是硅巢). H3PO4处理虽然不能脱除表面的Al原子, 但外表面残留的P物种能够有效的减小酸密度. MTP评价结果表明, H3PO4处理能够有效的延长催化剂的寿命和维持丙烯的选择性, 这是因为H3PO4处理既提高了外表面的容碳能力, 也抑制了积碳沉积的速率. Na2H2EDTA处理仅能增加外表面的容碳能力, 所以其只能延长催化寿命. 通过进一步优化H3PO4后处理的条件, 处理后的ZSM-5样品的催化寿命可以延长至前体的1.5倍, 同时, 丙烯的选择性也略有提高, 并且在失活前维持增加的趋势.     

制备条件对用于甘油蒸汽重整反应Ni基催化剂性能的影响

研究了制备参数对用于甘油蒸汽重整反应的Ni基催化剂性能的影响。采用过量浸渍法、等体积浸渍法和改进的平衡沉积过滤(EDF)法制备了一系列Al2O3负载的8 wt%Ni催化剂,运用X射线衍射(XRD)、电感耦合等离子体光谱仪、N2吸附-脱附、扫描电镜(SEM)、透射电镜和H2程序升温还原(TPR)表征了催化剂的表面和体相性质;采用CHN分析仪和SEM表征了使用后催化剂以测定其表面沉积的碳及其形貌。结果表明,制备方法对所制催化剂的织构、结构和表面性质影响很大,导致氧化铝表面Ni物种的分散和种类的不同。即使XRD和TPR结果证实形成了铝酸镍晶相,但Ni/Al-edf催化剂中β峰的贡献大于其它两个催化剂的,表明在这种情况下铝酸镍更容易还原。在550 oC以上CO2选择性增加和CO选择性不变,表明Ni/Al-wet和Ni/Al-edf催化剂可成功催化水汽变换反应。另外,650oC时Ni/Al-edf催化剂上甘油生成气相产物的转化率、氢气产率以及烯丙醇、乙醛和乙酸选择性最高,且它在所有催化剂中的积炭量也最低。将催化剂结构性质、分散度和还原性与其催化性能相关联,发现EDF法制得的催化剂比表面积和活性相分散度更高,更易被还原,因而其活性和生成H2的选择性更高,也更抗积碳。     

压力对USY催化甲苯裂解结焦及其前驱体的影响

研究了压力对USY催化剂催化甲苯裂解结焦及其前驱体的影响。采用热重、红外、13C固体核磁、元素分析、色质联用、程序升温氧化法等手段对催化剂上的焦炭和液相产物中的焦炭前驱体进行了考察。结果表明，沉积在催化剂上的焦炭主要为缩合度较高的多环芳烃，随着压力的升高，总的结焦量减少，液相产物中多环芳烃的环数和质量分数呈增加趋势，证明了超临界流体对焦炭前驱体有萃取效果。并探讨了超临界条件下甲苯催化裂解结焦的机理。     

制备方法对MnOx-CeO2催化剂理化性质及低温NH3-SCR脱硝性能的影响

随着人们环保意识的增强,氮氧化物(NOx)的危害引起广泛关注.NOx作为首要的大气污染物之一,主要来源于以燃煤电厂为代表的固定源和以机动车为代表的移动源.它不仅能够导致酸雨和光化学烟雾,而且还是PM2.5的重要前驱体,严重危害人类健康和植物生长.因此,NOx的治理迫在眉睫.研究表明,氨选择性催化还原(NH3-SCR)技术是控制固定源NOx排放最经济有效的方法.商业化V2O5-WO3/TiO2和V2O5-MoO3/TiO2脱硝催化剂的最佳工作温度窗口为300?400℃.因此,NH3-SCR脱硝设施通常安装在除尘器和脱硫装置之前以满足最佳工作温度需要.然而,在这种情况下,脱硝催化剂容易因烟气中的飞灰和含硫化合物堵塞、中毒而失活.此外,对于老电厂增加脱硝设施的改造工程,在除尘器和脱硫装置之前没有足够的空间用于安装脱硝设施.因此,开发环境友好型低温NH3-SCR脱硝催化剂显得尤为重要,因为它可以直接安装在除尘器和脱硫装置之后,从而有效减缓脱硝催化剂失活,有利于改造工程的施工.研究表明,锰基催化剂由于其优异的氧化还原性能和氧迁移能力有利于氧化NO为NO2,促进反应沿着"快速NH3-SCR"途径进行,从而表现出优异的低温脱硝性能.然而,其N2选择性、抗水性能和工作温度窗口还有待改善.因此,开发既具有高催化活性又具有宽工作温度窗口、优异抗水性能以及理想N2选择性的低温脱硝催化剂仍是一个富有挑战性的课题.二氧化铈(CeO2)由于具有优异的氧化还原性能、良好的储/释氧能力、丰富的氧空位以及Ce4+/Ce3+的轻易切换而被广泛用于NH3-SCR反应.因此,将锰氧化物(MnOx)与CeO2相结合而制备的MnOx-CeO2催化剂可能会表现出优异的低温脱硝性能.而催化剂的理化性质和催化性能还强烈地依赖于其制备方法.因此,本文采用不同方法(机械混合法、浸渍法、水热法、共沉淀法以及溶胶-凝胶法)制备了一系列MnOx-CeO2催化剂用于低温NH3-SCR反应,并运用X射线衍射(XRD)、拉曼光谱(Raman)、氮气物理吸附、氢气程序升温还原(H2-TPR)、氨气程序升温脱附(NH3-TPD)、X射线光电子能谱(XPS)以及原位漫反射红外光谱(in situ DRIFTS)等表征技术对催化剂进行了系统分析.重点考察了制备方法对MnOx-CeO2催化剂理化性质和催化性能的影响.结果表明,低温脱硝性能有如下顺序:水热法>溶胶-凝胶法>共沉淀法>浸渍法>机械混合法.这与催化剂表面Ce3+和Mn4+含量、氧空位和表面吸附氧物种浓度以及酸量和酸强度顺序一致.这些性质都与MnOx和CeO2之间的电子相互作用(即Mn3++Ce4+?Mn4++Ce3+)密切相关.特别是水热法制备的MnOx-CeO2催化剂(MnCe-HTM)由于Mnn+掺入到CeO2晶格形成铈基固溶体(含Mn-O-Ce结构)以及水热过程中的高温高压环境加强了MnOx和CeO2之间的电子相互作用,从而表现出优异的理化性质、最佳的低温脱硝性能以及理想的抗水性能.     

Catalytic performances of Ni/mesoporous SiO_2 catalysts for dry reforming of methane to hydrogen

Several mesoporous silicas with different morphologies were controllably prepared by sol-gel method with adjustable ratio of dual template,and they were further impregnated with aqueous solution of nickel nitrate,followed by calcination in air.The synthesized silica supports and supported nickel samples were characterized using N_2-adsorption/desorption,X-ray diffraction(XRD),H_2 temperature-programmed reduction(H_2-TPR),Scanning electron microscope(SEM),Transmission electron microscope(TEM) and thermo-gravimetric analysis(TGA-DTG) techniques.The Ni nanoparticles supported on shell-like silica are highly dispersed and yielded much narrower nickel particle-size than those on other mesoporous silica.The methane reforming with dioxide carbon reaction results showed that Ni nanoparticles supported on shell-like silica carrier exhibited the better catalytic performance and catalytic stability than those of nickel catalyst supported on other silica carrier.The thermo-gravimetric analysis on used nickel catalysts uncovered that catalyst deactivation depends on the type and nature of the coke deposited.The heterogeneous nature of the deposited coke was observed on nickel nanoparticles supported on spherical and peanut-like silica.Much narrower and lower TGA derivative peak was founded on Ni catalyst supported on the shell-like silica.     

Co-Mo/HZSM-5甲烷无氧芳构化催化剂上的积炭

 考察了Co－Mo／HZSM－5催化剂对甲烷芳构化反应的催化性能及催化剂上的积炭．采用碳数平衡计算法和TG法得出的平均积炭速率比较接近,在不同空速下,360min内,催化剂上的积炭量都接近5％．对烧炭TG曲线的分析结果表明,积炭量约为5％时,积炭能分散于分子筛表面．在高空速下,积炭容易沉积在分子筛的外表面;在低空速下,积炭容易沉积在分子筛的内表面．在空速3000ml／（g·h）下积炭时,其烧炭动力学过程符合一级反应过程,烧炭活化能为140．8kJ／mol．