Enhancing the Production of Light Olefins by Catalytic Cracking of FCC Naphtha over Mesoporous ZSM-5 Catalyst

The enhanced production of light olefins from the catalytic cracking of FCC naphtha was investigated over a mesoporous ZSM-5 (Meso-Z) catalyst. The effects of acidity and pore structure on conversion, yields and selectivity to light olefins were studied in microactivity test (MAT) unit at 600 °C and different catalyst-to-naphtha (C/N) ratios. The catalytic performance of Meso-Z catalyst was compared with three conventional ZSM-5 catalysts having different SiO₂/Al₂O₃ (Si/Al) ratios of 22 (Z-22), 27 (Z-27) and 150 (Z-150). The yields of propylene (16 wt%) and ethylene (10 wt%) were significantly higher for Meso-Z compared with the conventional ZSM-5 catalysts. Almost 90% of the olefins in the FCC naphtha feed were converted to lighter olefins, mostly propylene. The aromatics fraction in cracked naphtha almost doubled in all catalysts indicating some level of aromatization activity. The enhanced production of light olefins for Meso-Z is attributed to its small crystals that suppressed secondary and hydrogen transfer reactions and to its mesopores that offered easier transport and access to active sites.     

A selective catalyst for methanol conversion into light olefin with a high propylene to ethylene ratio

MSU-S catalyst, assembled from ZSM-5 zeolite seed (MFI), was synthesized with silica to alumina ratio 55 and characterized by XRD, NH3-TPD, BET and FT-IR techniques. It was tested in a vertical fixed bed reactor for selective production of light olefins from methanol (MTO) at temperatures of 400, 450 and 500 °C and WHSV of 1, 5 and 25 h^?1. After thorough investigation, it was found that WHSV=5 h^?1 and temperature of 500 °C are the optimum conditions for maximum light olefin yield, which was 52% with propylene to ethylene ratio of 4.57. Acidity of MSU-S was promoted by incorporation of phosphotungusticacid (HPW) and a direct method to reach high HPW dispersion and thermal stability. Maximum light olefin yield was observed over HPW-MSU-S at the optimum reaction conditions to be nearly 60% with propylene to ethylene ratio of 4.3.     

Fe改性HZSM-5分子筛上甲醇耦合C4烃制低碳烯烃反应性能研究

用等体积浸渍法制备Fe改性HZSM-5分子筛催化剂（Fe/HZSM-5）。考察了Fe/HZSM-5在不同温度下对甲醇耦合C₄烃制低碳烯烃反应性能的影响,并利用紫外-可见漫反射光谱对Fe/HZSM-5进行了表征。结果表明,在低铁含量条件下,Fe改性HZSM-5分子筛上Fe（Ⅲ）主要以高分散隔离的形式存在于HZSM-5分子筛的表面,Fe改性提高了催化剂上的原料转化率以及乙烯和丙烯选择性,从而获得了较高的乙烯和丙烯总收率。在反应温度为550 ℃时,在Fe（Ⅲ）处理的HZSM-5分子筛上,乙烯和丙烯总收率最高可达42.1%,比未改性的HZSM-5提高了7％。     

Fe_2O_3/HZSM-5催化转化乙醇制备低碳烯烃

采用浸渍法制备了Fe2O3/HZSM-5分子筛催化剂,并用于乙醇脱水与低聚制备丙烯为主的低碳烯烃反应体系.在400～500℃范围内考察了HZSM-5的硅/铝比、氧化铁负载量、反应温度、催化剂氢气还原预处理对产物中烯烃收率的影响.结果表明,HZSM-5硅/铝比为140时,丙烯、丁烯收率最高;氧化铁负载能有效提高烯烃收率,当负载量为2.9%时丙烯收率最高,接近25%;反应初期升高温度可促进丙烯生成,但催化剂寿命缩短;氢气还原预处理能进一步促进乙烯、丙烯生成.     

Catalytic Cracking of Heavy Olefins into Propylene, Ethylene and Other Light Olefins

Hybrid catalysts developed for the thermo-catalytic cracking of liquid hydrocarbons were found to be capable of cracking C₄ ⁺ olefins into light olefins with very high combined yields of product ethylene and propylene (more than 60 wt%) and C₂–C₄ olefins (more than 80 wt%) at 610–640 °C, and also with a propylene/ethylene weight ratio being much higher than 2.4. The olefins tested were heavier than butenes such as 1-hexene, C₁₀ ⁺ linear alpha-olefins (LAO) or a mixture of LAO. The hydrogen spillover effect promoted by the Ni bearing co-catalyst, contributed to significantly enhancing the product yield of light olefins and the on-stream stability of the hybrid catalyst.     

Synthesis of free template ZSM-5 catalyst from rice husk ash and co-modified with lanthanum and phosphorous for catalytic cracking of naphtha

ZSM-5 catalysts were synthesized from rice husk ash without using template and their catalytic activity has been investigated in catalytic cracking of light naphtha. Effect of hydrothermal temperature (170, 180 and 190?°C) on physicochemical properties of catalysts was investigated by BET, FE-SEM, FTIR, XRD and TGA-DTG analyses. The XRD analysis showed that hydrothermal temperature had great influence on crystalline structure of ZSM-5. Sample which was synthesized at 180 °C showed high crystllinity without any undesired alumina-silicate phases. The FE-SEM analysis showed that synthesis of ZSM-5 at 180?°C led to showed micro-scale hexagonal-shaped morphology. Furthermore, the textural properties of synthesized samples depend on the synthesis temperature drastically. Results of catalytic activity test showed that the synthesis temperature has great influence on the activity of ZSM-5 and the sample which synthesized with at 180?°C showed the highest catalytic activity. Furthermore, in order to improve the catalyst performance and the stability, both of Lanthanum and Phosphorus were used in catalytic cracking of naphtha. 2.5La–3P/ZSM-5 produced the highest light olefins yield. Catalyst modification of ZSM-5 by La and P, increased the ratio of propylene/ethylene from 1 to 2.     

Thermodynamic analysis of reaction pathways and equilibrium yields for catalytic pyrolysis of naphtha

The chain length and hydrocarbon type significantly affect the production of light olefins during the catalytic pyrolysis of naphtha. Herein, for a better catalyst design and operation parameters optimization, the reaction pathways and equilibrium yields for the catalytic pyrolysis of C_5–8 n/iso/cyclo-paraffins were analyzed thermodynamically. The results revealed that the thermodynamically favorable reaction pathways for n/iso-paraffins and cyclo-paraffins were the protolytic and hydrogen transfer cracking pathways, respectively. However, the formation of light paraffin severely limits the maximum selectivity toward light olefins. The dehydrogenation cracking pathway of n/iso-paraffins and the protolytic cracking pathway of cyclo-paraffins demonstrated significantly improved selectivity for light olefins. The results are thus useful as a direction for future catalyst improvements, facilitating superior reaction pathways to enhance light olefins. In addition, the equilibrium yield of light olefins increased with increasing the chain length, and the introduction of cyclo-paraffin inhibits the formation of light olefins. High temperatures and low pressures favor the formation of ethylene, and moderate temperatures and low pressures favor the formation of propylene. n-Hexane and cyclohexane mixtures gave maximum ethylene and propylene yield of approximately 49.90% and 55.77%, respectively. This work provides theoretical guidance for the development of superior catalysts and the selection of proper operation parameters for the catalytic pyrolysis of C_5–8 n/iso/cyclo-paraffins from a thermodynamic point of view.     

轻烃催化裂解制低碳烯烃反应规律与原料特征化

利用小型固定床实验装置对比研究了轻烃模型化合物的催化裂解性能,从优到劣的顺序依次是正构烯烃、正构烷烃、环烷烃、异构烷烃、芳香烃。正构烷烃、异构烷烃与环烷烃催化裂解的总低碳烯烃收率有较大差别,但是总低碳烯烃选择性却均在56.57%左右。研究了直馏石脑油的催化裂解性能,发现乙丙烯收率和总低碳烯烃收率随反应温度的升高及重时空速的降低而逐渐增大;在反应温度680℃、重时空速4.32 h^-1和水油稀释比0.35的条件下,乙丙烯收率35.87%（质量）,总低碳烯烃收率为41.94%（质量）。针对轻烃催化裂解提出了原料特征化参数KF,它是原料H/C原子比、相对密度与分子量的函数,能较好地表征轻烃原料的催化裂解性能。     

Kinetic study of the methanol to olefin process on a SAPO-34 catalyst

In this paper, a new kinetic model for methanol to olefin process over SAPO-34 catalyst was developed using elementary step level. The kinetic model fits well to the experimental data obtained in a fixed bed reactor. Using this kinetic model, the effect of the most important operating conditions such as temperature, pressure and methanol space-time on the product distribution has been examined. It is shown that the temperature ranges between 400 °C and 450 °C is appropriate for propene production while the medium temperature (450 °C) is favorable for total olefin yield which is equal to 33%. Increasing the reactor pressure decreases the ethylene yield, while medium pressure is favorable for the propylene yield. The result shows that the ethylene and propylene and consequently the yield of total olefins increase to approximately 35% with decreasing the molar ratio of inlet water to methanol.     

Catalytic conversion of palm oil to fuels and chemicals

The conversion of palm oil to hydrocarbons using a shape selective zeolite catalyst is reported in this work. Palm oil was passed over HZSM-5 catalyst in a fixed bed micro-reactor and the reactor was operated at atmospheric pressure, a temperature range of 360 to 420°C and weight hourly space velocity (WHSV) of 2 to 4 h^?1. The main objective was to study the effect of reaction temperature and oil space velocity on the conversion and selectivity of gasoline range hydrocarbons. The results show that 40 to 70wt% of the palm oil can be converted to aromatics and hydrocarbons in the gasoline, diesel and kerosene range, light gases, coke and water. The maximum gasoline range hydrocarbons yield of 40wt% of total product formed was obtained at 400°C and 2 h^?1 space velocity.     

Selective formation of light olefin by n-heptane cracking over HZSM-5 at high temperatures

The catalytic cracking of n-heptane has been performed over HZSM-5 catalysts with various Si/Al ratios at 723-923 K to form light olefins selectively. The HZSM-5 zeolites with various acid site densities exhibited almost the same selectivity at the same conversion. The ethylene + propylene selectivity increased, while the propylene/ethylene ratio decreased with an increase in reaction temperatures. It is found that a high temperature is required to obtain a high ethylene + propylene yield. The highest ethylene + propylene yield obtained in this study was 59.7 C-% with a propylene/ethylene ratio of ca. 0.72 at 99.6% conversion over HZSM-5 (Si/Al = 31) at 923 K. Moreover, it is concluded from the selectivities and activation energies that the monomolecular cracking is predominant at a high temperature as 923 K.     

CrHZSM-5 Zeolites – Highly Efficient Catalysts for Catalytic Cracking of Isobutane to Produce Light Olefins

The CrHZSM-5 catalysts with trace amount of Cr were firstly used for catalytic cracking of isobutane, and the effect of Cr-loading on the catalytic performances of CrHZSM-5 catalysts for the cracking of isobutane was also studied. The results suggested that when the loading of Cr in the CrHZSM-5 catalysts was less than 0.038 mmol/g Cr, especially at Cr loading of 0.004 mmol/g, both the reactivity of isobutane cracking and the selectivity to light olefins of CrHZSM-5 samples were greatly enhanced compared with the unpromoted HZSM-5, and very high yields of olefins(C₂+C₃) and ethylene were obtained. For instance, the yield of olefins(C₂+C₃) and ethylene reached 56.1% and 30.8%, respectively, at 625 °C when 0.004 mmol/g Cr was loaded on HZSM-5 sample.     

Controllably tailoring external surface sites of nanosheet HZSM-5 for maximizing light olefins in catalytic cracking of n-decane

A series of triphenylethoxysilane (TPEOS)-modified nanosheet HZSM-5 catalysts (ZN-x,x =4％,8％ and 16％,mass) were synthesized by chemical liquid deposition to selectively change external acidity distri-butions.TPEOS modification was found to passivate some external Brφnsted and Lewis acid sites by 37.8％,in which Brφnsted acid sites (BAS) were found more easily sacrificed by breaking the surface Al-O bond of bridging hydroxyl groups and forming Si-O-Si bonds.The selectivity of ZN-8 catalyst for light olefins (ethylene,propylene and butene) in n-decane catalytic cracking is up to 26％ (450 ℃,WHSV =10.95 h-1),which is ca.78％ higher than that of parent one.The better performance was attrib-uted to the appropriate external acid density in ZN-8,which inhibits bimolecular hydrogen transfer reac-tion of light olefins on the adjacent acid sites,resulting in more olefins,few coke precursors and thus an excellent catalytic stability.     

Kinetic study of crude oil-to-chemicals via steam-enhanced catalytic cracking in a fixed-bed reactor

This study presents new experimental results on the direct conversion of crude oil to chemicals via steam-enhanced catalytic cracking. We have organized the experimental results with a kinetics model using crude oil and steam co-feed in a fixed-bed flow reactor at reaction temperatures of 625, 650, and 675°C over the Ce-Fe/ZSM-5 catalyst. The model let us find optimum conditions for crude oil conversion, and the order of the steam cracking reaction was 2.0 for heavy oil fractions and 1.0 for light oil fractions. The estimated activation energies for the steam cracking reactions ranged between 20 and 200 kJ/mol. Interestingly, the results from kinetic modelling helped in identifying a maximum yield of light olefins at an optimized residence time in the reactor at each temperature level. An equal propylene and ethylene yield was observed between 650 and 670°C, indicating a transition from dominating catalytic cracking at a lower temperature to a dominating thermal cracking at a higher temperature. The results illustrate that steam-enhanced catalytic cracking can be utilized to effectively convert crude oil into basic chemicals (52.1% C2-C4 light olefins and naphtha) at a moderate severity (650°C) as compared to the conventional high-temperature steam cracking process.     

Selective Production of C4 Hydrocarbons from Syngas Using Fe‐Co/ZrO2 and SO42—/ZrO2 Catalysts

Modified Fischer‐Tropsch (MFT) syntheses were carried out to convert synthesis gas to C₄ hydrocarbons over Fe‐Co/ZrO₂ (FT) and SO₄^2—/ZrO₂ (SZ) catalysts in a dual reactor system, keeping the FT to SZ catalysts ratio at 1:1.5. Five Fe‐Co/ZrO₂ catalysts with different Fe and Co loading, and SZ with 15 wt% SO₄^2— were prepared and extensively characterized using various physico‐chemical methods. The FT synthesis process was initially performed using a Fe‐Co/ZrO₂ catalyst in a single reactor and the effects of Fe and Co mass ratio, reaction temperature, space velocity on the production of C₄ hydrocarbons and C₂‐C₄ olefins were investigated. Results indicated that a 3.71% Fe—8.76% Co/ZrO₂ mixed oxide catalyst alone at 260°C and 5 h^—1 gave high selectivities of C₂‐C₄ olefins (～26.1 wt%) and total C₄ hydrocarbon product (～16.2 wt%). The MFT process 150°C gave higher C₄ (～31.6 wt%), isobutane (～22.9 wt%) and C₂‐C₄ (31.1 wt%) selectivities.     

Conversion of canola oil to various hydrocarbons over Pt/HZSM-5 bifunctional catalyst

Canola oil conversion was studied at atmospheric pressure over Pt/HZSM-5 catalyst (0.5 mass% Pt) in a fixed bed micro-reactor. The operating conditions were: temperature range of 400?500°C, weight hourly space velocity (WHSV) of 1.8 and 3.6 h^?1 and steam/oil ratio of 4. The objective was to optimize the amount of gasoline range hydrocarbons in the organic liquid product (OLP) and the selectivity towards olefins and isohydrocarbons in the gas product. The gas yields varied between 22–65 mass% and were higher in the presence of steam compared to the operation without steam. The olefin/paraffin mass ratio of C₂-C₄ hydrocarbon gases varied between 0.31–0.79. The isohydrocarbons/n-hydrocarbons ratio was higher with Pt/HZSM-5 (1.6–4.8) compared with pure HZSM-5 catalyst (0.2–1.0). The OLP yields with Pt/HZSM-5 (20–55 mass% of canola oil) were slightly lower compared to HZSM-5 (40–63 mass% of canola oil) under similar conditions. The major components of OLP were aliphatic and aromatic hydrocarbons. A scheme postulating the reaction pathways for the conversion of canola oil over Pt/HZSM-5 catalyst is also presented.     

Performance of nanostructure Fe-Ag-ZSM-5 catalysts for the catalytic oxidation of volatile organic compounds: Process optimization using response surface methodology

Gas phase catalytic oxidation of ethyl acetate was studied in low concentration over Fe-Ag-ZSM-5 catalysts under atmospheric pressure. The effect of important parameters such as Ag loading, Fe loading, calcinations temperature and reaction temperature was investigated and the process conditions were optimized using response surface methodology (RSM) based on central composite design (CCD). The optimum condition for Ag loading, Fe loading, calcination temperature and reaction temperature was 5.17 wt%, 2 wt%, 580 °C and 350 °C, respectively. A maximum of 96% of ethyl acetate was removed under the optimum experimental conditions. The proposed model equation using RSM has shown good agreement with the experimental data, with a correlation coefficient (R²) of 0.949.     

Catalytic conversion of canola oil to fuels and chemicals over various cracking catalysts

The catalytic conversion of canola oil to fuels and chemicals was studied over HZSM-5, H-mordenite, H-Y, silicalite, aluminum-pillared clay (AL-PILC) and silica-alumina catalysts in a fixed bed micro-reactor. The reactor was operated at atmospheric pressure, a temperature range of 375?500°C and weight hourly space velocity (WHSV) of 1.8 and 3.6 h^?1. An organic liquid product (OLP), light hydrocarbon gases and water were the major products. The objective was to maximize the amount of OLP and its hydrocarbon content as well as optimize the selectivity for gas phase olefinic hydrocarbons. In addition, the performance of each catalyst in terms of minimizing the coke formation was examined. Among the six catalysts, HZSM-5 gave the highest amount of OLP of 63 mass% at 1.8 WHSV and 400°C. The hydrocarbon content of this OLP product was 83.8 mass%. With the exception of silica-alumina and aluminum-pillared clay catalysts, the other catalysts gave high concentrations of aromatic hydrocarbons which ranged between 23.1–95.6 mass% of OLP. The gas products consisted mostly C₃ and C₄ hydrocarbons. Ethylene, propylene and butanes were some of the valuable hydrocarbon gases. The olefin/paraffin ratio of the gas products was highest for AL-PILC catalysts but it never exceeded unity. The results showed that it was possible to significantly alter the yield and selectivity for the different hydrocarbon products by using different catalysts or changing the catalyst functionality such as acidity, pore size and crystallinity. Reaction pathways based on these results are proposed for the conversion of canola oil     

改性HZSM-5对甲醇制烯烃反应性能的影响研究

分别用非金属、碱金属、碱土金属、过渡金属以及稀土金属对HZSM-5催化剂进行改性,考察了改性催化剂对低碳烯烃的选择性影响,并选取改性效果较好的元素组合制备双金属改性催化剂,以进一步提高低碳烯烃的选择性。结果表明,双金属改性催化剂可明显提高C2=～C4=的总烯烃选择性,副产物得到了有效抑制。其中,钾-钙改性后丙烯的选择性最好,从25%提高到42%;钙-铈改性后,乙烯选择性较高,从25%提高到43%;钾-锌和钙-锌改性后,低碳烯烃选择性下降,二甲醚的选择性呈现不断上升趋势,从5%提高到60%左右。改性催化剂对反应过程的影响从一定程度上验证了本文提出的MTO反应网络。     

Downer Catalytic Pyrolysis (DCP): A Novel Process for Light Olefins Production

Based on the analysis of different existing cracking processes, the DCP (downer catalytic pyrolysis) process is proposed for the production of light olefins from heavy feeds. A hot downer reactor with the height of 4.5 m and the inner diameter of 13 mm was designed and built to examine the details. The experimental results show that high olefins yields can be obtained from the DCP process: at the temperature of 659 °C and residence time of 0.75 seconds, the total yields of ethylene, propylene and butylene are up to 51.54 wt.‐%, while the methane and coke are suppressed. At the same time, the stability of liquid products is desirable because of the high content of aromatics but low concentration of olefins.