Polymer waste recycling over “used” catalysts

Catalytic degradation of high-density polyethylene (HDPE) was carried out under nitrogen using a laboratory fluidised bed reactor operating at 360 °C with catalyst to polymer feed ratio of 2:1 and at 450 °C with catalyst to polymer feed ratio of 6:1 under atmospheric pressure. The catalysts used in this study were ZSM-5, US-Y, ASA, fresh FCC (fluid catalytic cracking) commercial catalyst (Cat-A) and equilibrium FCC catalysts with different levels of metal poisoning were studied. The initial results for polymer degradation at 360 °C (catalyst to polymer ratio of 2:1) in a fluidised bed reactor in terms of the yield of volatile hydrocarbon products were: model catalysts>commercial FCC catalyst>E-Cats. However, when the process conditions more closely resembled to FCC conditions, the fresh commercial FCC catalyst was more favourable in terms of the yield of volatile hydrocarbon products. The degradation of HDPE over E-Cats although reduced was similar to ASA in product selectivity and yield, and the level of metal contamination did not affect the product stream generated. A simple economic evaluation of polymer recycling process is reported showing that a catalytic system based on E-Cats appears comparable in costs to a commercial thermal cracking plant.     

Recycling polystyrene into fuels by means of FCC: performance of various acidic catalysts

In accordance with the option of recycling plastics into fuels by dissolving them in standard feedstocks for the process of catalytic cracking of hydrocarbons, FCC, various acidic catalysts (zeolites ZSM-5, mordenite, Y, and a sulfur-promoted zirconia) were tested in the conversion of polystyrene dissolved into inert benzene at 550°C in a fluidized-bed batch reactor. Experiments were performed with very short contact times of up to 12 s. Main products were in the gasoline range, including benzene, toluene, ethylbenzene, styrene, and minor amounts of C_9–12 aromatics and light C₅₋ compounds. Coke was always produced in very significant amounts. All the products can be justified with basis on the properties of each catalyst and the various possible catalytic reaction pathways: cracking after protolytic attack on the polymer fragments, styrene oligomerization and subsequent cracking, or hydrogen transfer to styrene. Styrene would be mainly produced in this system from thermal cracking of the polymer as the initial step. If present, shape selectivity effects due to catalyst structure can influence significantly the prevalence of the various reactions, because they would interfere with those undergoing bulky transition states, like styrene oligomerization or hydrogen transfer. Even though sulfur-promoted zirconia is highly acidic, the low proportion of Brønsted-type acid sites does not allow the occurrence of secondary styrene reactions. It was shown that most favorable product distributions (higher yields of desirable products) are obtained on equilibrium commercial FCC catalysts.     

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.     

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.     

Conversion of waste plastics into fuels: Recycling polyethylene in FCC

Low density polyethylene was dissolved into toluene and converted at 500 °C over three different commercial FCC catalysts in a laboratory Riser Simulator reactor. Short reaction-times up to 12 s were used. All the catalysts had qualitatively similar behaviors. The specific contribution of the polymer to the product slate of FCC was centered in hydrocarbons in the range of gasoline, with high aromatic content and highly olefinic C₃–C₄ gases. Saturated C₄–C₅ products were mainly isoparaffins. The additional coke formed by the polymer would make coke yields to increase moderately in relation to the standard operation. These facts confirmed that this recycling option, which is based on a proven technology, represents an interesting alternative to solve a major environmental problem.     

Production of gasoline range hydrocarbons from catalytic reaction of methane in the presence of ethylene over W/HZSM-5

The catalytic conversion of a methane and ethylene mixture to gasoline range hydrocarbons has been studied over W/HZSM-5 catalyst. The effect of process variables, such as temperature, percentage of volume of ethylene in the methane stream and catalyst loading on the distribution of hydrocarbons was studied. The reaction was conducted in a fixed-bed quartz-micro reactor in the temperature range of 300–500 °C using percentage of volume of ethylene in methane stream between 25 and 75% and catalyst loading of 0.2–0.4 g. The catalyst showed good catalytic performance yielding hydrocarbons consisting of gaseous products along with gasoline range liquid products. The mixed feed stream can be converted to higher hydrocarbons containing a high-liquid gasoline product selectivity (>42%). Non-aromatics C₅–C₁₀ hydrocarbons selectivity in the range of 12–53% was observed at the operating conditions studied. Design of experiment was employed to determine the optimum conditions for maximum liquid hydrocarbon products. The distribution of the gasoline range hydrocarbons (C₅–C₁₀ non-aromatics and aromatics hydrocarbons) was also determined for the optimum conditions.     

CuZnTiO2/SAPO-34双功能催化剂的设计、制备及其用于CO2加氢制烯烃性能

CO₂加氢经甲醇（含氧中间体）制低碳烯烃工艺路线,可实现成醇、脱水两步反应串联协同进行,打破费托合成产物Anderson-Schulz-Flory（ASF）分布限制,高选择性地制取低碳烯烃。传统甲醇合成Cu基催化剂加氢能力较强,在两步反应中产物以CH₄、低碳烷烃为主。实验设计、制备了CuZnTiO₂/(Zn-)SAPO-34复合催化剂,实现了CO₂加氢在Cu基复合催化剂上高选择性合成C₂～C₄烯烃（约60%）。研究表明,两步反应过程中甲醇体积分数较低（＜6%）,且高温下逆水煤气变换反应严重,导致催化剂酸性变化对产物分布的影响较大。调变两类活性位点比例发现,CH₄的产生与串联反应存在竞争关系,SAPO-34酸量的增加抑制了CH₄的生成,促进串联反应正向进行;合适的酸性有助于生成C₂～C₄烯烃。控制成醇、脱水两类活性位点接触距离可调变烯烃的二次反应,降低加氢能力,改善产物分布。     

Catalytic degradation of waste polyolefinic polymers using spent FCC catalyst with various experimental variables

Liquid-phase catalytic degradation of waste polyolefinic polymers (HDPE, LDPE, PP) over spent fluid catalytic cracking (FCC) catalyst was carried out at atmospheric pressure with a stirred semi-batch operation. The effect of experimental variables, such as catalyst amount, reaction temperature, plastic types and weight ratio of mixed plastic on the yield and accumulative amount distribution of liquid product for catalytic degradation was investigated. The initial rate of catalytic degradation of waste HDPE was linearly increased with catalyst amount (4-12 wt%), while that was exponentially increased with reaction temperature (350-430 ‡C). Spent FCC catalyst in the liquid-phase catalytic degradation of polymer was not deactivated fast. The product distribution from catalytic degradation using spent FCC catalyst strongly depended on the plastic type. The catalytic degradation of mixed plastic (HDPE: LDPE: PP: PS=3: 2: 3: 1) showed lower degradation temperature by about 20 ‡C than that of pure HDPE.     

催化、动力学与反应器Pt/Y催化剂催化FCC柴油加氢制备BTX

利用Pt/Y催化剂,在固定床反应器中,温度380℃、压力3 MPa、氢油体积比1000及质量空速1.0 h^-1条件下,分别采用加氢处理的全馏分和轻馏分催柴为原料制备苯、甲苯和二甲苯（BTX）,获得（C₆+C₇+C₈）芳烃的总选择性分别为9.4%和33.9%。对原料和液体产物进行的气相色谱和质谱分析表明,BTX主要经过重芳烃的加氢饱和、裂解等反应生成,中间物质为烷基苯、四氢萘、茚满及茚类等单环芳烃。通过对反应原料以及对反应前后催化剂的N₂吸脱附、NH₃-TPD、XRD衍射图谱、TG等物化性质的表征,分析催化剂失活的主要原因。即全馏分催柴原料中高含量的S、N化合物快速吸附造成了催化剂中毒,而轻馏分原料中S、N化合物在催化剂表面的缓慢积累覆盖活性位,造成催化剂逐渐失活。     

不同类型催化剂对异丁烯齐聚反应过程的影响

采用固定床反应器分别探究了三类催化剂（固体磷酸催化剂、酸性阳离子交换树脂催化剂以及分子筛催化剂）对异丁烯齐聚过程的影响。实验结果表明：固体磷酸催化剂适用于C₈烯烃的生产,酸性阳离子树脂催化剂及改性的分子筛催化剂（Hβ）适合生产C₁₂烯烃。异丁烯齐聚产物C₈～C₁₆（清洁燃料油）因无芳烃、无硫,在石化工业中具有非常广泛的应用潜力;由三种类催化剂的评价结果来看,C₈～C₁₆的选择性最高时均能接近100%,但是固体磷酸催化剂和酸性阳离子树脂催化剂的异丁烯原料转化率比Hβ分子筛催化剂低,Hβ催化作用下异丁烯转化率可以达到88%。     

Production of clean transportation fuels and lower olefins from Fischer-Tropsch Synthesis waxes under fluid catalytic cracking conditions: The potential of highly paraffinic feedstocks for FCC

The potential of Fischer-Tropsch Synthesis (FTS) waxes as a feedstock for fluid catalytic cracking (FCC) has been evaluated with a once-through microriser reactor operating under realistic conditions. The highly paraffinic feedstock has a high reactivity and can be converted under industrial conditions to a high extent (>90 wt%). The product distribution can be optimised by the process parameters and catalyst formulation. A high gasoline fraction (70 wt%) with a very low aromatics concentration can be obtained. As a result of the formation of i-paraffins, n-olefins and i-olefins the gasoline is expected to possess an acceptable octane number. The reaction scheme derived predicts that the degree of branching in the paraffinic diesel-range product is lower than that of the gasoline-range product and that a relatively good diesel is expected. Due to the absence of sulfur and nitrogen in the feed extremely clean transportation fuels are obtained. The addition of ZSM-5 to an equilibrium catalyst allows the production of significant amounts of light olefins, in particular propene (16 wt%) and butenes (15 wt%).     

Hydrocarbon fuels produced by catalytic pyrolysis of hospital plastic wastes in a fluidizing cracking process

A mixture of post-consumer polyethylene/polypropylene/polystyrene (PE/PP/PS) with polyvinyl chloride (PVC) waste was pyrolyzed over cracking catalysts using a fluidizing reaction system operating isothermally at ambient pressure. The influences of catalyst types and reaction conditions including reaction temperatures, ratios of catalyst to plastic feed, flow rates of fluidizing gas and catalyst particle sizes were examined. Experiments carried out with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A model based on kinetic and mechanistic considerations associated with chemical reactions and catalyst deactivation in the acid-catalyzed degradation of plastics has been developed. The model gives a good representation of experimental results from the degradation of commingled plastic waste. The results of this study are useful for determining the effects of catalyst types and reaction conditions on both the product distribution and selectivity from hospital plastic waste, and especially for the utilization of post-use commercial FCC catalysts for producing valuable hydrocarbons in a fluidizing cracking process.     

Catalytic conversion of postconsumer PE/PP waste into hydrocarbons using the FCC process with an equilibrium FCC commercial catalyst

A mixture of postconsumer polyolefin waste (PE/PP) was pyrolyzed over cracking catalysts using a fluidizing reaction system similar to the fluid catalytic cracking (FCC) process operating isothermally at ambient pressure. Experiments carried out with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. Greater product selectivity was observed with a commercial FCC equilibrium catalyst (Ecat‐F1) with more than 50 wt % olefins products in the C₃‐C₆ range. A kinetic model based on a lumping reaction scheme for the observed products and catalyst coking deactivations has been investigated. The model gave a good representation of experiment results. Moreover, this model provides the benefits of lumping product selectivity, in each reaction step, in relation to the performance of the FCC equilibrium catalyst used, the effect of reaction temperature, and the particle size selected. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Light olefins dimerization to high quality gasoline components

New attractive technologies can be designed in the field of light olefins dimerization (C₃–C₅) in order to obtain products useful as gasoline blending components; the technologies are characterized both by low investment costs and by high product quality. Isobutene dimerization is a powerful alternative to MTBE production whenever the use of the latter will be forbidden in gasoline. Also the dimerization of iso-amylenes and propylene, when properly designed, can give products (both the olefins and the corresponding hydrogenated derivatives) characterized by very high octane numbers. More in general all these technologies can help to debottleneck the FCC downstream when enhanced olefins production is achieved by means of new FCC catalysts and processes.     

载体对Li-Mn氧化物催化甲烷氧化偶联反应作用

采用浸渍法制备不同金属氧化物载体负载的Li-Mn/MO_x(M=Mg,La,Ti,Si,Zr,Ta)催化剂,对其甲烷氧化偶联反应活性进行评价。结果表明,以TiO_2为载体制备的Li-Mn/TiO_2催化剂具有较高的CH_4转化率和C2烃选择性,C_2烃产率显著提高,金属氧化物TiO_2是Li-Mn复合氧化物的优良催化剂载体。n(Li)∶n(Mn)=1.0∶2.0形成的Li-Mn/TiO_2催化剂具有最高的CH_4转化率和C_2烃选择性,n(C_2H_4)∶n(C_2H_6)的增加有助于提高反应产物中C_2H_4的相对浓度,W元素的添加未能进一步提高Li-Mn/TiO_2催化剂的催化活性。Li-Mn/TiO_2催化剂在n(Li)∶n(Mn)=1.0∶2.0、反应温度775℃、反应压力0.1 MPa、V(CH_4)∶V(O_2)=2.5、空速7 200 m L·(h·g)~(-1)和催化剂用量0.5 g条件下,CH_4转化率达31.9%,C_2选择性达52.7%,表现出最佳催化效果。     

等离子体与Cu-Pd/S-1催化剂协同催化甲烷转化制低碳烯烃

采用等体积浸渍法制备了Pd、Cu-Pd改性的S-1催化剂,利用介质阻挡放电（DBD）等离子体反应器研究了甲烷无氧转化制低碳烯烃（C₂~C₄⁼）的性能,重点关注了乙烯的产量。探讨了Ar的添加和特定输入能量（SIE）对甲烷转化率以及产物分布的影响。实验结果表明,等离子体与催化剂协同催化与仅使用等离子体相比性能更优异,使乙烯选择性提高了3.1倍,C₂~C₄⁼的选择性提高了2.7倍;与S-1相比,Pd/S-1具有更高的乙烯选择性,这是因为在S-1上负载金属Pd有助于乙炔原位加氢生成乙烯;适宜的Pd负载量有利于提高烯烃选择性,而过高的Pd负载量倾向于不饱和烃的连续加氢,导致了烷烃的生成;与单金属Pd改性相比,Cu-Pd双金属改性抑制了乙烯的进一步加氢,提高了乙烯的选择性。通过扫描电子显微镜（SEM）、透射电子显微镜（TEM）、高倍透射电子显微镜（HRTEM）、X射线粉末衍射（XRD）、X射线光电子能谱（XPS）对催化剂进行了表征分析。结果表明,Cu的加入使自身电子向Pd转移,增加了Pd电子密度;另外,Cu的存在提高了Pd的分散性。以2Cu-0.1Pd/S-1为催化剂时可以得到更优异的反应性能。     

A comparative study of liquid product on non-catalytic and catalytic degradation of waste plastics using spent FCC catalyst

Non-catalytic and catalytic degradation of waste plastics (high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS)) using spent fluid catalytic cracking (FCC) catalyst into liquid product were comparatively studied with a stirred semi-batch reactor at 400 ‡C, under nitrogen stream. Liquid product characteristics were described by cumulative distribution as a function of lapse time of reaction, paraffin, olefin, naphthene and aromatic (PONA) composition, and also carbon number distribution on plastic type of reactant. For degradation of waste PE with relatively high degradation temperature, the effect of adding spent FCC catalyst greatly appeared on cumulative distribution of liquid product with a reaction lapse time, whereas those for waste PP and PS with low degradation temperature showed a similar trend in both non-catalytic and catalytic degradation at 400 ‡C. In PONA and carbon number distribution of liquid product, the characteristics of waste PS that was mainly degraded by end chain scission mechanism were not much altered in presence of spent FCC catalyst. However, waste polyolefinic polymer that was degraded by a random chain scission mechanism significantly differed on PONA and carbon number distribution of liquid product with or without spent FCC catalyst. The addition of spent FCC catalyst in degradation of polyolefinic polymer, which economically has a benefit in utilization of waste catalyst, significantly improved the light olefin product by its high cracking ability and also the aromatic product by cyclization of olefin as shape selectivity in micropore of catalyst.     

Deactivated iron catalyst in the fischer-tropsch synthesis

The selectivity for higher hydrocarbons (C₁₁–C₁₇) has been studied in the Fischer-Tropsch synthesis using fresh and used fused iron catalysts under different reaction conditions. On increasing the temperature higher hydrocarbon products were formed in the C₁₁–C₁₇ range. The deactivated fused iron catalyst is less active but selective to heavier hydrocarbon chain molecules. The product distribution is shifted towards heavier hydrocarbons due to the effects of the pore volume, presence of potassium and site densities at the surface.     

Reactivity of olefins in the hydrodesulfurization of FCC gasoline over CoMo sulfide catalyst

To achieve selective hydrodesulfurization (HDS) of fluid catalytic-cracked (FCC) gasoline for producing sulfur-free gasoline (S < 10 ppm), the reactivity of various olefins contained in FCC gasoline on CoMoP/Al₂O₃ sulfide catalysts was investigated. Isomerization of the CC double bond from the terminal position to an internal position was observed. The steric hindrance around the CC double bond suppresses the reactivity of olefin hydrogenation. The sulfidation temperature of the catalyst has a major influence on olefin hydrogenation active sites. Addition of the appropriate amount of cobalt (Co/Mo ratio approximately 0.6) contributes to the suppression of olefin hydrogenation at high reaction temperature (260 °C). From the comparison of catalytic performance and characterization of our CoMoP/Al₂O₃ catalyst with an analogous commercial catalyst, it is suggested that the hydrogenation of olefins depends not only on the state of the Mo CUS but also on the steric effects of both olefin structure and MoS₂ crystalline structure.     

Palladium–sulfated zirconium pillared montmorillonite: Catalytic evaluation in light naphtha hydroisomerization reaction

The present work is an evaluation of 1 wt.% Pd/sulfated zirconium pillared montmorillonite catalyst in the hydroisomerization reaction of two fractions of light naphtha composed mainly of C₅ and C₆ paraffins (feeds 1 and 2). Catalyst activity test was carried out in a fixed-bed flow reactor at reaction temperature of 300 °C, under atmospheric hydrogen pressure and weight hourly space velocity of 0.825 h⁻¹.

The reaction products showed high isomer and cyclane selectivity. Monobranched and multibranched isomers were formed as well as C5 and C6 cyclane products. After the catalytic reaction, the total amount of benzene and cyclohexane decreased by 30% for the “feed 1” and by 40% for the “feed 2” leading to methylcyclopentane formation in the products. A long-term performance test catalyst for the two light naphtha fractions was also performed and we observed an improving of the research octane number (RON) by 15–17 for, respectively, feeds 1 and 2.