ZSM-5分子筛在MTP反应中的催化性能

合成了3种不同晶粒尺寸的ZSM-5分子筛,并制得MTP催化剂,对ZSM-5分子筛催化剂在MTP反应中的性能进行系统研究。采用XRD、SEM、N2物理吸附和TGA等对ZSM-5分子筛催化剂进行表征,发现小晶粒的ZSM-5分子筛具有良好的抗积炭性能,在MTP反应中具有较高的稳定性。采用小晶粒分子筛制成的催化剂,考察反应工艺条件对催化剂催化性能的影响,结果表明,丙烯选择性随反应温度和空速提高而增加,降低反应压力和提高水醇质量比也有利于提高丙烯选择性,为调整MTP工艺的产物分布和优化反应工艺条件提供了技术依据。     

改性介微孔ZSM-5分子筛催化剂制备及催化甲苯甲醇烷基化反应性能

将微孔ZSM-5分子筛通过不同浓度的氢氧化钠溶液处理不同的时间制备不同的介微孔ZSM-5分子筛,然后负载五氧化二磷制备介微孔ZSM-5分子筛催化剂,对介微孔ZSM-5分子筛负载五氧化二磷催化剂进行甲苯甲醇烷基化反应评价。其中氢氧化钠溶液浓度为1.0 mol/L、处理时间为30 min得到的介微孔ZSM-5分子筛负载五氧化二磷催化剂催化甲苯甲醇烷基化反应的活性较高。对介微孔ZSM-5分子筛负载五氧化二磷催化剂进一步采用铂进行改性,将制备的催化剂用于甲苯甲醇烷基化反应,在460 ℃条件下连续反应505 h,甲苯转化率保持在10.9%,二甲苯中对二甲苯的选择性保持在96%以上。研究结果表明,五氧化二磷、铂改性的介微孔ZSM-5分子筛催化剂具有优异的甲苯甲醇烷基化反应性能。     

ZSM-5分子筛在甲醇转化制烯烃领域应用的研究进

综述了ZSM-5分子筛在甲醇制烯烃反应特别是在甲醇制丙烯反应中的应用。介绍在接近工业反应条件下甲醇在ZSM-5分子筛上生成烯烃的反应机理,在较高反应温度下高碳数烯烃裂解是导致轻烯烃形成的主要反应路径;分析ZSM-5分子筛酸性及粒径对产品选择性及催化剂寿命的影响,由于ZSM-5分子筛酸性较强,直接用于甲醇制烯烃反应时低碳烯烃的选择性不高,而粒径小的ZSM-5分子筛扩散性能好,因而丙烯选择性得到提高。重点介绍小晶粒ZSM-5分子筛的研究进展,指出目前ZSM-5分子筛的研究方向一是对其进行酸性改性,二是制备酸度适中、粒径合适和具有介孔的多级结构ZSM-5分子筛。     

ZSM-5分子筛在甲醇转化制烯烃领域应用的研究进展

综述了ZSM-5分子筛在甲醇制烯烃反应特别是在甲醇制丙烯反应中的应用。介绍在接近工业反应条件下甲醇在ZSM-5分子筛上生成烯烃的反应机理,在较高反应温度下高碳数烯烃裂解是导致轻烯烃形成的主要反应路径;分析ZSM-5分子筛酸性及粒径对产品选择性及催化剂寿命的影响,由于ZSM-5分子筛酸性较强,直接用于甲醇制烯烃反应时低碳烯烃的选择性不高,而粒径小的ZSM-5分子筛扩散性能好,因而丙烯选择性得到提高。重点介绍小晶粒ZSM-5分子筛的研究进展,指出目前ZSM-5分子筛的研究方向一是对其进行酸性改性,二是制备酸度适中、粒径合适和具有介孔的多级结构ZSM-5分子筛。     

K/ZSM-5的正己烷催化裂解性能

采用浸渍法制备了一系列不同K载量的K/ZSM-5催化剂,在小型固定床实验装置上考察了催化剂的正己烷催化裂解活性及产物分布的影响规律。结果表明,碱金属K改性可以降低ZSM-5分子筛的酸性,从而大大提高了丙烯的选择性,使得丙烯/乙烯质量比从0.59提高至3.22,同时也降低了甲烷、芳烃等副产物的选择性。另外,还考察了反应条件对1.0 K/ZSM-5催化剂反应性能的影响,当反应温度650℃,空速3 h-1时,双烯收率大于48%,丙烯/乙烯质量比达到1.30。     

K/ZSM-5的正己烷催化裂解性能

采用浸渍法制备了一系列不同K载量的K/ZSM-5催化剂,在小型固定床实验装置上考察了催化剂的正己烷催化裂解活性及产物分布的影响规律。结果表明,碱金属K改性可以降低ZSM-5分子筛的酸性,从而大大提高了丙烯的选择性,使得丙烯/乙烯质量比从0.59提高至3.22,同时也降低了甲烷、芳烃等副产物的选择性。另外,还考察了反应条件对1.0 K/ZSM-5催化剂反应性能的影响,当反应温度650℃,空速3 h-1时,双烯收率大于48%,丙烯/乙烯质量比达到1.30。     

ZSM-5分子筛催化甲醇耦合C5-C6烷烃芳构化反应研究

分别使用硅铝比38、50、120、200、300的ZSM-5分子筛原粉制备5种催化剂为ZSM-5-38、ZSM-5-50、ZSM-5-120、ZSM-5-200、ZSM-5-300,用于催化甲醇耦合C5-C6正构烷烃芳构化反应,并对催化剂进行XRD和NH3-TPD的表征。利用100 m L固定床试验装置,评价其催化甲醇耦合C5、C6反应的影响。试验结果表明:硅铝比在50左右的ZSM-5分子筛催化剂有适宜的酸密度和酸强度,其催化甲醇耦合C6烷烃反应,甲醇的转化率100%,C6烷烃的转化率达到94.3%,液相产物芳烃的选择性高。     

PZSM-5分子筛催化剂用于烯烃催化裂解的研究

以固定流化床研究了不同磷含量改性的ZSM-5分子筛对混合₄烯烃催化裂解性能的影响,并以适当磷含量的催化剂进行了工艺条件试验。试验表明,磷与ZSM-5分子筛骨架中的羟基发生了化学作用,改善了催化剂的催化性能及水热稳定性;高负荷、高水比及适当增加磷的负载量,可以抑制烯烃裂解的氢转移反应,有利于提高丙烯选择性。     

正己烷催化裂解制低碳烯烃：ZSM-5分子筛催化剂酸性的影响

在小型固定床装置上,以ZSM-5分子筛为催化剂,研究不同硅铝物质的量比对合成的ZSM-5分子筛织构性能以及酸性对正己烷催化裂解性能的影响。采用XRD、SEM、N₂吸附-脱附和NH_3-TPD等方法对不同硅铝物质的量比的ZSM-5分子筛进行表征,结果表明,硅铝物质的量比的改变对ZSM-5分子筛的形貌和结构没有影响;随着硅铝物质的量比的增加,分子筛的酸量减少,酸强度减弱,正己烷催化裂解活性逐渐降低。同时,随着酸量减少和酸强度减弱,高硅ZSM-5分子筛上氢转移反应得到明显抑制,丙烯选择性提高。     

用于MTP反应ZSM-5分子筛的磷改性研究

将P改性用于甲醇制丙烯(MTP)反应ZSM-5分子筛的改性研究,以提高丙烯选择性和分子筛活性稳定性。采用XRD、SEM和NH_3-TPD表征催化剂物化性能。对不同硅铝比ZSM-5分子筛P改性研究发现,3种不同硅铝物质的量比(50、150和300)ZSM-5分子筛进行P改性时,在n(P)∶n(Al)=0.5~0.7时,ZSM-5分子筛改性后丙烯选择性和寿命得到提升。研究分子筛晶粒尺寸与P负载量关系时发现,随着分子筛晶粒尺寸的增大,位于分子筛表面的P含量逐渐增加,并且分子筛晶粒越小,最佳的P负载量越小。     

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%。     

碳五烃催化裂解制取丙烯/乙烯反应性能

以ZSM-5分子筛为催化剂,碳五烃混合物为裂解原料,考察空速对碳五烃催化裂解制丙烯/乙烯反应性能的影响。结果表明,在580℃和实验空速范围,随着空速的增加,碳五烷烃及烯烃转化率整体呈下降趋势,但碳五烯烃转化率远高于碳五烷烃。乙烯及丙烯收率在空速3 h-1时达到最大,分别为10.51%和13.02%。碳四烯烃收率随空速的升高而降低,但各丁烯异构体相对于总烯烃的质量分布接近热力学平衡态。     

甲醇制对二甲苯联产低碳烯烃改性ZSM-5催化剂在流化床中的反应性能

在流化床反应器中,对Zn、Si和P改性的ZSM-5催化剂的甲醇制对二甲苯联产低碳烯烃的反应性能进行了研究。采用X射线衍射（XRD）、BET比表面积、扫描电镜（SEM）、NH₃-程序升温脱附（NH₃-TPD）等手段进行表征分析。结果表明,Zn改性使得催化剂酸强度降低,中强酸酸量增加,对二甲苯和低碳烯烃选择性都随之提高;一定量的硅沉积改性在降低催化剂外表面酸量的同时缩小孔口,浸渍适量P能够调变分子筛的酸中心强度和酸量,这都能够提高对二甲苯选择性。在流化床反应器中甲醇制对二甲苯联产低碳烯烃反应结果表明,3Zn-3Si-3P/ZSM-5催化剂在温度425℃、常压、反应时间40min、空速1h^-1的条件下,对二甲苯在二甲苯中的选择性为76.0%,C₂~C₄低碳烯烃选择性为24.4%,特别是芳烃和C₂~C₄低碳烯烃的总选择性高达92.2%。     

Light olefin production by catalytic co-cracking of Fischer–Tropsch distillate with methanol and the reaction kinetics investigation

Catalytic co-cracking of Fischer–Tropsch(FT) light distillate and methanol combines highly endothermic olefin cracking reaction with exothermic methanol conversion over ZSM-5 catalyst to produce light olefins through a nearly thermoneutral process. The kinetic behavior of co-cracking reactions was investigated by different feed conditions: methanol feed only, olefin feed only and co-feed of methanol with olefins or F–T distillate. The results showed that methanol converted to C_2–C_6 olefins in first-order parallel reaction at low space time, methylation and oligomerization–cracking prevailed for the co-feed of methanol and C_2–C_5 olefins, while for C_6–C_8 olefins,monomolecular cracking was the dominant reaction whether fed alone or co-fed with methanol. For FT distillate and methanol co-feed, alkanes were almost un-reactive, C_3–C_5 olefins were obtained as main products, accounting for 71 wt% for all products. A comprehensive co-cracking reaction scheme was proposed and the model parameters were estimated by the nonlinear least square method. It was verified by experimental data that the kinetic model was reliable to predict major product distribution for co-cracking of FT distillate with methanol and could be used for further reactor development and process design.     

ZSM-5分子筛的复合改性及催化裂化性能

针对催化裂化反应中提高汽油辛烷值和增加丙烯收率，对择形分子筛ZSM-5的改性方法进行研究。通过磷、钴和稀土的复合改性，不仅提高改性元素磷的利用率，而且加强分子筛裂化汽油中C₅、C₆烯烃以及异构化和芳构化能力，达到增产丙烯同时生产清洁汽油的目的。小型固定流化床评价结果表明，常规FCC催化剂中添加复合共沉淀法改性分子筛制备的催化剂助剂后，液化气产率提高3.22个百分点，丙烯收率提高1.52个百分点以上，汽油研究法辛烷值提高2个单位以上。     

Feedstock recycling of agriculture plastic film wastes by catalytic cracking

Feedstock recycling by catalytic cracking of a real plastic film waste from Almeria greenhouses (Spain) towards valuable hydrocarbon mixtures has been studied over several acid catalysts. The plastic film waste was mostly made up of ambient degraded low-density polyethylene (LDPE) and ethylene-vinyl acetate (EVA) copolymer, the vinyl acetate content being around 4 wt.%. Nanocrystalline HZSM-5 zeolite (crystal size 60 nm) was the only catalyst capable of degrading completely the refuse at 420 °C despite using a very small amount of catalyst (plastic/catalyst mass ratio of 50). However, mesoporous catalysts (Al-SBA-15 and Al-MCM-41), unlike it occurred with virgin LDPE, showed fairly close conversions to that of thermal cracking. Nanocrystalline HZSM-5 zeolite led to 60 wt.% selectivity towards C₁---C₅ hydrocarbons, mostly valuable C₃---C₅ olefins, what would improve the profitability of a future industrial recycling process. The remarkable performance of nanocrystalline HZSM-5 zeolite was ascribed to its high content of strong external acid sites due to its nanometer dimension, which are very active for the cracking of bulky macromolecules. Hence, nanocrystalline HZSM-5 can be regarded as a promising catalyst for a feasible feedstock recycling process by catalytic cracking.     

Effects of large pore zeolite additions in the catalytic pyrolysis catalyst on the light olefins production

To increase the light olefins selectivity of catalytic pyrolysis catalyst for heavy oil processing, the effects of large pore zeolite additions on the selectivity to light olefins (ethylene and propylene) were studied in a micro-activity test (MAT) unit at 625 °C by using Daqing heavy oil and n-decene/n-decane as feedstocks. Rare earth containing ultra-stable Y, Hβ and four types of alkali-treated Hβ with different pore size distributions were employed as the large pore zeolite components. The yields of C₂–C₃ light olefins showed a volcano trend with the increasing amount of large pore zeolite additions. They reached up to 24.5 and 26.7 wt%, respectively, when an optimum combination of zeolites ZSM-5 and RE-USY or ZSM-5 and alkali-treated Hβ was used. Moreover, increasing the pore size of large pore zeolites also led to the increases in the yields of light olefins, the maximum total yields of ethylene and propylene reached up to 26.7 wt% when the total pore volume of the zeolite Hβ added was 0.452 cm³ g⁻¹.     

Catalytic conversion of commingled polymer waste into chemicals and fuels over spent FCC commercial catalyst in a fluidised-bed reactor

A commingled post-consumer polymer (CPW#1) was pyrolysed over spent fluid catalytic cracking (FCC) commercial catalyst (ECat-1) using a laboratory fluidised-bed reactor operating isothermally at ambient pressure. The influence of reaction conditions including catalyst, temperature, ratios of commingled polymer to catalyst feed and flow rates of fluidising gas was examined. The conversion for spent FCC commercial catalyst (82.7 wt%) gave much higher yield than silicate (only 14.2 wt%) and the highest yield (nearly 87 wt%) was obtained for ZSM-5. Greater product selectivity was observed with ECat-1 as a recycled catalyst with about 56 wt% olefins products in the C₃–C₇ range. The selectivity could be further influenced by changes in reaction conditions. Valuable hydrocarbons of olefins and iso-olefins were produced by low temperatures and short contact times used in this study. It is also demonstrated that the use of spent FCC commercial catalyst and under appropriate reaction conditions can have the ability to control both the product yield and product distribution from polymer degradation, potentially leading to a cheaper process with more valuable products.     

Direct synthesis of middle iso-paraffins from synthesis gas on hybrid catalysts

This paper focuses on the synthesis of iso-paraffin-rich hydrocarbons by Fischer–Tropsch synthesis (FTS) over silica gel supported Co catalyst (Co/SiO₂). The basic concept is to isomerize and/or hydrocrack the primary FTS hydrocarbon products. A physical mixture consisting of a small amount of zeolite or Pd/zeolite mixed with Co/SiO₂ enhanced the formation of C₄–C₁₀ iso-paraffins while suppressing the formation of higher molecular hydrocarbons, probably because of the selective cracking of these hydrocarbons on them. In separate experiments, a two-reactor system was used. The first reactor contained a physical mixture of Co/SiO₂ and zeolite, and the second reactor contained zeolites or Pd-supported zeolites. The two-reactor system gave sharp C-number distribution within C₃–C₆ and iso-paraffins-rich products. The hydrocracking of n-octane and n-decane (model compound simulating products of the FTS reaction) over mixed catalysts composed of various compositions of Pd/SiO₂ and ZSM-5 in the presence of gaseous hydrogen showed high and stable activity, and produced primarily iso-paraffin-rich hydrocarbons. The isomerization was favored for mixtures rich in Pd/SiO₂. The role of Pd was thought to be the inlet of hydrogen spillover to the zeolite surface.