小晶粒ZSM-22的可控合成及其催化长链正构生物烷烃制航空煤油性能

由生物脱氧油制生物航空煤油具有较大应用潜力和发展前景,为了提高生物航煤的收率,开发性能更好的加氢裂化/异构化催化剂是关键。本文采用水热合成法,在低温陈化、加入晶种、提高合成凝胶的碱度或加入有机碱条件下,合成了平均c轴尺寸在100~330nm的小晶粒ZSM-22分子筛,进行了XRD、SEM、N₂物理吸附、NH₃-TPD和吡啶红外表征,并以生物质油加氢脱氧得到的长链正构生物烷烃为原料,考察了不同晶粒尺寸 ZSM-22催化剂催化裂化和异构化制生物航空煤油的性能。结果表明,通过提高碱度合成的小晶粒H-ZSM-22 具有较强的酸中心,较多可及的强B酸中心数量,其长链正构烷烃转化率可达80%以上。在此基础上,制备的Pt/ZSM-22催化剂具有较高的Pt分散度,表现出很好的加氢裂化/异构化性能,其长链正构烷烃的转化率高达97.79%,生物航煤收率达50.25%,航煤产物异正比为7.55。     

正构烷烃在Pt/SAPO-11催化剂上加氢异构反应性能

采用SAPO-11分子筛制备Pt/SAPO-11双功能加氢异构催化剂,以n-C₈、n-C₁₂和n-C₁₆为模型化合物考察正构烷烃的加氢异构反应性能。结果表明,所制备的催化剂具有较好的异构化活性和选择性,其中单甲基支链异构产物收率和总异构产物收率分别可达60%和75%以上,是低凝柴油和高档润滑油基础油的理想组分。不同链长正构烷烃的异构化产物分布基本一致,但链长较长的正构烷烃更容易发生异构化反应和裂解反应,在保证相同转化率条件下长链烷烃裂解产物收率偏高且异构选择性降低。     

正构烷烃在Pt/SAPO-11催化剂上加氢异构反应性能

采用SAPO-11分子筛制备Pt/SAPO-11双功能加氢异构催化剂,以n-C_8、n-C_(12)和n-C_(16)为模型化合物考察正构烷烃的加氢异构反应性能。结果表明,所制备的催化剂具有较好的异构化活性和选择性,其中单甲基支链异构产物收率和总异构产物收率分别可达60%和75%以上,是低凝柴油和高档润滑油基础油的理想组分。不同链长正构烷烃的异构化产物分布基本一致,但链长较长的正构烷烃更容易发生异构化反应和裂解反应,在保证相同转化率条件下长链烷烃裂解产物收率偏高且异构选择性降低。     

Pt/ZSM-22催化剂酸性原位调控及加氢异构性能

采用水热法合成ZSM-22分子筛并制备催化剂载体,通过负载贵金属Pt,制备出高分散Pt/H-ZSM-22加氢异构催化剂。以n-C₁₂为原料,考察催化剂的加氢异构性能,在正构烷烃加氢异构反应过程中,通过在原料油中引入一定量含氮物种二正丁胺,使其在催化剂酸性位上发生化学吸附,对催化剂酸性进行原位调控,考察催化剂性能变化。结果表明,随着反应温度提高,酸性调控后的Pt/N-ZSM-22液体收率下降缓慢,且转化率达到85%以上时,Pt/N-ZSM-22的异构选择性比Pt/H-ZSM-22高出约3个百分点。酸性调控后的Pt/N-ZSM-22可通过提高反应温度进行含氮物种脱附,恢复催化剂酸位点的可接近性。采用酸性调控后的催化剂用于以加氢裂化尾油为原料的加氢异构反应,基础油收率均较调控前催化剂有明显提高。     

正构生物烷烃在Pt/ZSM-5催化剂上选择性加氢裂化制备液体生物燃料

开发了一种通过正构生物烷烃在Pt/ZSM-5催化剂上的选择性加氢裂化来制备高品质液体生物燃料的新方法.生产得到的液体生物燃料包含了煤油、汽油和柴油,分离后可直接作为航空燃料或车用燃料使用.以商业ZSM-5分子筛为载体,制备和表征了不同组成的Pt/ZSM-5催化剂.采用转化率、煤汽比和异构率为指标,考察了温度、压力和空速等条件对反应的影响,比较了不同组成时催化剂的催化性能.结果表明:对于同一催化剂,裂化产物异构率随转化率增加而增加;除转化率外,异构率还与酸性位的烯烃被覆度相关;当采用0.7%Pt/ZSM-5(硅铝比50)为催化剂时,在4MPa、320℃、1h^-1、氢油体积比1500:1的反应条件下,原料转化率即可达到82%,产物中煤油含量为43.6%,异构率为1.29,汽油含量为38.0%.     

Ni-W/SSY催化裂化生物正构烷烃制备航空燃料

以超稳SSY分子筛负载Ni-W制得加氢裂化催化剂,用于加氢裂化生物正构烷烃(C16、C18),得到以煤油和汽油为主的液体生物燃料,可以提高中油组分收率。通过氮气物理吸附,扫描电镜(SEM),X射线光电子能谱(XPS)等分析手段对催化剂进行了表征。在微型固定床连续加氢裂化反应器上,考察了反应条件对单程转化率和煤油/汽油质量比的影响规律。结果表明:255℃、1.0 MPa、质量空速为0.33 h-1、氢油比为4 000:1的反应条件下,单程转化率达到60%以上,煤油与汽油质量比超过2.0。Ni-W/SSY催化剂活性高,可以用于长链烷烃加氢裂化制备煤油组分为主的液体燃料。     

HZSM-22的粒径调控及Pt/HZSM-22的正十二烷加氢异构催化性能

通过调控合成液中的水含量,采用过饱和溶液法,在静态水热条件下合成了三种不同c轴长度的ZSM-22分子筛,对其进行了X射线衍射、扫描电子显微镜、N₂物理吸附、NH₃-程序升温脱附和吡啶吸附傅里叶变换红外光谱(Py-FTIR)表征。并以所制备的ZSM-22分子筛为酸性载体,在其上负载0.5%(质量分数)的金属Pt作为加(脱)氢活性位点,制备成Pt/ZSM-22双功能催化剂。以正十二烷为探针分子,进行正构烷烃加氢异构化反应,考察了分子筛合成液中水含量对Pt/ZSM-22催化剂加氢异构化性能的影响。结果表明,随着合成液中水含量减少,ZSM-22分子筛粒径减小。但是当水含量低到一定值时,会有方英石和ZSM-5杂晶生成。当分子筛合成液摩尔组成为SiO₂∶Al₂O₃∶K₂O∶DEA∶H₂O=1∶0.01∶0.08∶0.29∶28时,获得的HZSM-22在所合成的三种分子筛中拥有最多的中、强Br?nsted酸量以及较短的c轴长度,对应的双功能催化剂P...     

正十二烷和加裂尾油在Pt/SAPO-11和Pt/ZSM-22上加氢异构化反应性能

分别以SAPO-11和ZSM-22为酸性载体制备加氢异构降凝催化剂,并借助物理吸附,NH3-TPD表征催化剂的结构及酸性;分别以正十二烷和加氢裂化尾油为原料,对Pt/SAPO-11和Pt/ZSM-22催化剂异构化性能及脱蜡降凝效果进行考察。结果表明,以正十二烷为模型分子时,Pt/SAPO-11上异构烷烃选择性更高,而以加氢裂化尾油为原料时,Pt/ZSM-22因存在的少量强酸,会发生部分非对称裂解,使得尾油脱蜡降凝效果更好。     

Pt/TiO2/ZSM-5催化剂的制备及其催化转化正丁烷

采用溶胶-凝胶法和等体积浸渍法,分别对ZSM-5分子筛进行TiO₂改性和Pt负载,获得了具有脱氢-裂解双功能的Pt/TiO₂/ZSM-5催化剂,采用XRD、N₂吸附-脱附、TEM、XPS和NH₃-TPD对样品的晶体结构,孔结构、形貌、活性金属价态和酸性质等进行了表征,并研究了正丁烷在此催化剂上催化转化制备低碳烯烃的反应规律。研究结果表明,TiO₂的引入,一方面使得改性后的ZSM-5分子筛获得了额外的酸性中心,特别是强酸性位含量的增加,有助于促进正丁烷的活化;另一方面Pt与TiO₂之间存在“金属-载体”强相互作用（SMSI）,在H₂还原气氛下,Pt能够促进TiO₂的还原,生成Ti³⁺物种,而Ti³⁺的存在增加了Pt周围的电荷密度,降低了Pt对低碳烯烃（C₂⁼～C₃⁼）的吸附能力,抑制了深度脱氢和生焦反应,从而提高双功能催化剂对烯烃的选择性。当H₂还原温度为450℃时,Pt/10TiO₂/ZSM-5催化剂在625℃下的正丁烷转化率为76.1%,低碳烯烃（C₂⁼～C₃⁼）收率为50.9%,分别比Pt/ZSM-5催化剂提高了16.7%和12.6%。     

Pt/USY催化剂上四氢萘选择性开环反应

通过USY分子筛载体上负载Pt制备Pt/USY催化剂，考察Pt/USY催化剂对四氢萘选择性开环反应的影响。结果表明，USY分子筛载体负载Pt后，四氢萘转化率提高，且明显改善开环的选择性。通过工艺条件的研究，得知在空速为2 h^-1、氢油体积比为750∶1、反应压力为4 MPa和反应温度为280℃时，Pt_0.4/USY催化剂性能最好，四氢萘转化率大于99%,C₁₀产物收率大于94%,开环选择性高于38%。     

Hydroisomerization and hydrocracking of long chain n-alkanes on Pt/amorphous SiO2–Al2O3 catalyst

The hydroisomerization and hydrocracking of n-hexadecane, n-octacosane and n-hexatriacontane on a 0.3% platinum/amorphous silica–alumina (MSA/E) catalyst was investigated in a stirred microautoclave at 345, 360 and 380°C and between 2 and 13.1 MPa hydrogen pressure. For each n-paraffin, the reaction pathway and the kinetic parameters were determined. The results were used to elucidate the effect of chain length and operating conditions on isomerization and cracking selectivity. The conversion of the n-paraffins lead to the formation of a mixture of the respective isomers, as the main product, together with cracking products. At every temperature, the iso-alkane/n-alkane ratio of cracking products increased considerably with increasing conversion degree. At the same conversion level, higher reaction temperatures lead to cracking products characterized by a lower iso-alkane/n-alkane ratio. The conversion rate constants showed a considerable increase between n-C₁₆ and n-C₂₈, whereas a slight decrease between n-C₂₈ and n-C₃₆ was observed. The hydroisomerization selectivities showed a decrease as a function of chain length and with increasing conversion levels. The increase in reaction temperature leads to a small decrease in the isomerization selectivities only at low-medium conversion degrees and at the highest temperature investigated, while the effect of this parameter on the maximum yields achievable in iso-C16, iso-C28 and iso-C36 was negligible. The results indicate that the conversion of the n-paraffins follows a first-order kinetic in hydrocarbon while the order in hydrogen pressure was −1.1 ± 0.21 for n-C₁₆ and −0.66 ± 0.15 for n-C₂₈. Furthermore, an increase in hydroisomerization selectivity at higher hydrogen pressure for n-C₂₈ conversion was observed.     

The synergic effects of highly selective bimetallic Pt-Pd/SAPO-41 catalysts for the n-hexadecane hydroisomerization

The hydroisomerization of n-hexadecane over Pt-Pd bimetallic catalysts is an effective way to produce clean fuel oil. This work reports a useful preparation method of bimetallic bifunctional catalysts by a co-impregnation or sequential impregnation process. Furthermore, monometallic catalysts with loading either Pt or Pd are also prepared for comparison. The effects of the metal species and impregnation order on the characteristics and catalytic performance of the catalysts are investigated. The catalytic test results indicate that the maximum iso-hexadecane yield over different catalysts increases as follows: Pt/silicoaluminophosphate SAPO-41iso-hexadecane yield of 89.4% when the n-hexadecane conversion is 96.3%. Additionally, the Pt-Pd/SAPO-41 catalyst also presents the highest catalytic activity and best stability even after 150 h long-term tests.     

Simultaneous isomerization of n-heptane and saturation of benzene over Pt/Beta catalysts: The influence of zeolite crystal size on product selectivity and sulfur resistance

In this work we show that decreasing the zeolite crystal size has a clear benefit on product selectivity and sulfur resistance of Pt/Beta catalysts during the simultaneous hydroisomerization of n-heptane and hydrogenation of benzene. The higher isomerization selectivity of the catalyst prepared from a nanocrystalline Beta zeolite can be ascribed to a faster diffusion of the iso-C₇ products through the small crystallites preventing cracking reactions to occur, while the improved sulfur resistance can be related to a better dispersion of Pt owing to its higher surface area and mesoporosity.     

Ethylbenzene transformation on bifunctional Pt/Al2O3-NaHMOR catalysts Influence of Na exchange on their activity and selectivity in ethylbenzene isomerization

Ethylbenzene transformation was carried out on bifunctional catalysts constituted by Pt/Al₂O₃ (PtA) associated with NaHMOR (Si/Al=10) zeolite samples. The operating conditions were the following: fixed bed reactor, temperature 683 K, pressure of hydrogen and of ethylbenzene equal to 8 and 2 bar, respectively, weight hourly space velocity (WHSV) between 5 and 150 h⁻¹. Twelve different bifunctional catalysts were used differing by the Na exchange rate of the mordenite component or by the relative proportions of the NaHMOR and Pt/Al₂O₃ components or by the Pt content of the Pt/Al₂O₃ (0.5 or 2.3 wt.%). As expected from a bifunctional mechanism, the activity in isomerization per protonic site (turnover frequency, TOF) increases first with the ratio between the concentrations of accessible platinum sites (n_Pt) and of the protonic sites (n_H⁺), then remains constant above a certain value of this ratio. It is shown that the exchange of the mordenite causes a significant increase in the selectivity to isomers of the bifunctional catalysts. This increase can be related to a decrease in the rates of the main secondary reaction (disproportionation), but also of the other ones: dealkylation, hydrocracking, transalkylation.     

Evidences for pore mouth and key–lock catalysis in hydroisomerization of long n-alkanes over 10-ring tubular pore bifunctional zeolites

The evidence for the pore mouth catalysis model for n-alkane methylbranching on Pt/H-ZSM-22 hydroisomerization catalyst is reviewed. It is based on adsorption equilibria at catalytic temperatures determined using tracer and perturbation chromatography, reaction product distributions obtained with nC₈–nC₂₄ n-alkanes and rival model screening for catalytic conversions. In the Henry regime, methylbranched isomers have lower adsorption entropy and enthalpy compared to n-alkanes explained by the enhanced rotational and translational freedom of methyl and methylene groups positioned outside the pore interacting with the external surface. Adsorption isotherms for isoalkanes are in agreement with dual site adsorption in pore mouths and on external surfaces, respectively. The hydroisomerization can be modeled with a bifunctional reaction scheme and adsorption on the external crystal surfaces and pore mouths. The selectivity for 2-methylbranching reflects the optimum van der Waals interaction of the n-alkane with the zeolite pore and methylbranching in that part of the chain that is located outside the first 10-ring of the zeolite pore to facilitate desorption. Very long n-alkanes (C₁₂⁺) exhibit key–lock adsorptions and penetrate simultaneously with their two ends into two different pores. Key–lock physisorption leads to branching at more central C atom positions.     

Efficient separation of C4 olefins using tantalum pentafluor oxide anion-pillared hybrid microporous material

With the increasing demand for synthetic rubber, the purification of 1,3-butadiene (C₄H₆) is of great industrial significance. Herein, the successful removal of n-butene (n-C₄H₈) and iso-butene (iso-C₄H₈) from 1,3-butadiene (C₄H₆) was realized by synthesizing a novel TaOF₅^2- anion-pillared ultramicroporous material TaOFFIVE-3-Ni (also referred to as ZU-96, TaOFFIVE=TaOF₅^2-, 3=pyrazine). Single-component adsorption isotherms show that TaOFFIVE-3-Ni can achieve the exclusion of n-C₄H₈ and iso-C₄H₈ in the low pressure region (0-30 kPa), and uptake C₄H₆ with a high capacity of 92.78 cm³·cm^-3 (298 K and 100 kPa). The uptake ratio of C₄H₆/iso-C₄H₈ on TaOFFIVE-3-Ni was 20.83 (298 K and 100 kPa), which was the highest among the state-of-the-art adsorbents reported so far. With the rotation of anion and pyrazine ring, the pore size changes continuously, which makes smaller-size C₄H₆ enter the channel while larger-size n-C₄H₈ and iso-C₄H₈ are completely blocked. The excellent breakthrough performance of TaOFFIVE-3-Ni shows great potential in industrial separation of C₄ olefins. The specific adsorption binding sites within ZU-96 was further revealed through the modeling calculation.     

The hydrocracking of n-decane over bifunctional Ni-H3PW12O40/SiO2 catalysts

A series of bifunctional Ni-H₃PW₁₂O₄₀/SiO₂ catalysts for the hydrocracking of n-decane were designed and prepared. The evaluation results of the catalysts show that Ni-H₃PW₁₂O₄₀/SiO₂ catalysts possess a high activity for hydrocracking of n-decane and an excellent tolerance to the sulfur and nitrogen compounds in the feedstock. Under the reaction conditions: reaction temperature 300 °C; H₂/n-decane volume ratio of 1500; total pressure of 2 Mpa and the LHSV 2 h⁻¹, the conversion of n-decane over reduced 5%Ni-50%H₃PW₁₂O₄₀/SiO₂ catalysts is as high as 90%, the C₅⁺ selectivity equal to 70%. In order to reveal the structure and nature of the catalysts, a number of characterizations including XRD, Raman, H₂-TPD, NH₃-TPD, XPS and FT-IR of pyridine adsorption were carried out. The characteristic results show that the high activity of the catalysts and high C₅⁺ selectivity can be related to the unique structure of the H₃PW₁₂O₄₀ and its suitable acidity.     

酸处理对Pt/ZSM-22物化及其催化性能的影响

采用HCl溶液对ZSM-22分子筛载体进行酸处理,在改性后的载体上负载金属Pt制备Pt/ZSM-22催化剂。采用XRD、N2吸附-脱附和NH3-TPD等研究酸处理对载体孔结构及酸性质造成的影响,考察改性催化剂在F-T轻组分蜡制备润滑油基础油反应中的加氢异构性能。结果表明,酸处理没有破坏ZSM-22分子筛结构,可提高孔容,产生大孔径介孔,改变载体酸量。酸处理后的催化剂表现出优异的加氢异构性能,所得润滑油基础油收率、异构化率、低温性能和黏度指数明显提高。