Yield Of Light Olefins Research Articles

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.

Efficient Conversion of Light Cycle Oil into High-Octane-Number Gasoline and Light Olefins over a Mesoporous ZSM-5 Catalyst

Producing high-octane-number (ON) gasoline and light olefins is a promising route to valorize light cycle oil (LCO). In this work, the LCO was mildly hydrogenated and then catalytically cracked to produce high-ON gasoline and light olefins. Mesoporous ZSM-5 zeolite (meso-ZSM-5) was prepared and, for the first time, was applied in this process to crack the hydrogenated LCO (hydro-LCO). The catalytic performance of meso-ZSM-5 was evaluated in detail under different reaction temperatures and weight hourly space velocities (WHSVs). The results showed that, in comparison to less than 64 wt % hydro-LCO conversion over the conventional ZSM-5 catalyst, the novel catalyst exhibited excellent performance in cracking hydro-LCO with quite a high conversion of 84.8 wt %, affording a gasoline yield of 56.4 wt % and light olefin yield of 19.3 wt % at 560 °C and 10 h–1. In addition, the conversion behaviors of hydro-LCO components were analyzed over both the conventional ZSM-5 and meso-ZSM-5 catalysts. Finally, on the ba...

Propane catalytic cracking on pretreated La-ZSM-5 zeolite during calcination for light olefins production

The purpose of this study was to increase light olefins yield and selectivity in catalytic cracking of propane. Pretreatment of ZSM-5 zeolite was performed during calcination. First, lanthanum was loaded on the catalyst by wet impregnation method and then the effect of parameters, such as temperature (400–800 °C), time (120–480 min) and type of stream, on La-ZSM-5 zeolite was examined during calcination using central composite design (CCD) method. Based on the proposed models, the optimized condition for maximizing selectivity of light olefins for air stream was 680 °C and 310 min and for the nitrogen stream was 735 °C and 173 min that under these conditions, selectivity amount increased 24% for nitrogen stream and 19% for air stream as compared with H-ZSM-5 catalyst. The synthesized catalysts were characterized by X-ray diffraction (XRD) and temperature-programmed desorption (TPD) techniques. According to the results of NH3-TPD, as the temperature increased, the number of strong acid sites (specially Bronsted acid sites) reduced and resulted in increased production of light olefins as well as catalyst stability. Accordingly, stability of the samples calcined with nitrogen stream was higher than the samples calcined with the air stream.

Mathematical modelling of catalytic cracking riser reactor

The quality and the yield of gasoline and light olefins from the catalytic cracking unit depend on a broad range of operation indicators including the feedstock composition, the process conditions, the type and activity of the catalyst. The aim of research is to develop the mathematical model of catalytic cracking reactor on the basis of the formalized mechanism of hydrocarbon conversion taking into account the catalyst deactivation by coke. The experimental research of the feedstock and the product of catalytic cracking using a liquid-adsorption chromatography, gas chromatography–mass spectrometry, gas-liquid chromatography and the structural-group composition methods allowed determining the list of the catalytic cracking reactions. According to the discovered reactions, the thermodynamic analysis was performed using the methods of quantum chemistry. Thermo-gravimetric analysis of the coked catalyst allowed estimating the coke structure formed on the catalyst surface. The developed mathematical model allows to predict the product yields including the content of propane-propylene (PPF) and butane-butylene (BBF) fractions, the group composition and octane number of the gasoline depending on the feedstock composition, the process conditions of reactor-regenerator unit and the catalyst activity. As a result, the high theoretical yield of the gasoline (60.4 wt.%, RON 93.5) according to requirements for the content of olefins and benzene can be achieved at the process temperature of 533°C. This temperature is possible at the keeping the catalyst circulation ratio of 6.9 toncat/tonfeed at the catalyst flow temperature after regeneration (685.8°C) with the catalyst activity of 0.79 unit and the feedstock temperature (328.0°C). The yields of rich gas and coke are 24.0wt% and 4.5 wt%, the concentrations of PPF and BBF are 31.5 and 34.8 wt%.

Catalytic cracking of vacuum gasoil over -SVR, ITH, and MFI zeolites as FCC catalyst additives

The cracking behaviour of three medium-pore zeolites -SVR, ITH, and MFI, with varying Si/Al molar ratio, was evaluated using an equilibrium FCC catalyst (E-Cat) and a hydrotreated vacuum gasoil (VGO) in a microactivity test unit (MAT). The increase in the yield of light olefins (21–29wt% over E-Cat/additive vs. 16wt% over E-Cat) was accompanied by a drop in the yield of gasoline (26–39wt% over E-Cat/additive vs. 43wt% over E-Cat) due to the cracking of reactive species in gasoline fraction (mainly olefins and isoparaffins). With increasing Si/Al ratio in zeolites MFI-280 and –SVR-120, propylene yield passed through maxima reaching 13.5wt% and 12.8wt%, respectively, compared with 7.0wt% over E-Cat. Maximum propylene yield occurred partially due to gasoline over-cracking to light olefins (inverse relation with Si/Al ratio). The effect of MFI crystal size showed that large size crystals enhanced the yield of light olefins as compared to small size crystals due to secondary cracking of gasoline molecules. Results of kinetic study based on 4-lump model showed proportional relation between MFI Si/Al ratio and activation energy for the conversion of gasoline to gases. Activation energy increased from 14.2kcal/mol to 16.3kcal/mol as Si/Al ratio increased from 30 to 2000.

Preparation, scale-up and application of meso-ZSM-5 zeolite by sequential desilication–dealumination

Meso-ZSM-5 zeolites with unique catalytic cracking properties have been prepared from commercial ZSM-5 using sequential desilication–dealumination strategy. Desilication and dealumination conditions, including concentration, temperature, dissolution time and liquid–solid ratio were systematically studied and optimized. Characterization results revealed that mesoporosity can be effectively introduced into commercial ZSM-5 crystals by desilication. The introduction of mesopores enables the well interconnectivity of micropores. Concomitant dealumination by removing Al-rich debris from desilicated samples shows superiority in micro- and mesopore network, remedying the limitation of desilication. The removal of the debris preserves intrinsic microporosity and improves the acid site accessibility in zeolites. Based on optimized parameters of porosity tuning tests at 0.25 L scale, the preparation route was scaled up to a pilot scale (50 L). In the heavy oil catalytic cracking test, compared with P-ZSM-5-contained catalyst, A-ZSM-5-contained and ACP-ZSM-5-contained FCC catalyst display increased heavy oil conversion (from 67.68 to 68.25 and 68.33 wt%, respectively), improved light olefin yield including propylene (from 5.67 to 5.87 and 6.11 wt%, respectively) and promoted yields of both gasoline and diesel.

Catalytic cracking of crude oil to light olefins and naphtha: Experimental and kinetic modeling

The direct catalytic cracking of three light crude oils have been evaluated over an equilibrated FCC catalyst (E-Cat) blended with MFI zeolite in a microactivity test unit at 550°C and catalyst/oil ratio between 1 to 4. At 60% conversion, the Super Light (ASL) crude oil yielded about 10wt.% C2–C4 olefins and 60wt.% naphtha over E-Cat, Extra Light (AXL) crude oil yielded 13wt.% light olefins and 52wt.% naphtha, while for Arab Light (AL) crude oil, light olefins and naphtha produced were 12 and 51wt.%, respectively. The addition of MFI with varying Si/Al molar ratio (Z30, Z280 and Z1500) to E-Cat increased the yield of light olefins with a maximum at 21.3wt.% for AXL over E-Cat/Z280. PIONA analysis of co-produced naphtha showed an increase in aromatics content over all additives with a maximum obtained from the cracking of AL over Z30 (91wt.%). Steam treatment of Z280 led to a slight change in the yield of light olefins and reduction of naphtha aromatics for the three types of crude oils. A four-lump kinetic model accurately predicted experimental yields of AL cracking over E-Cat and E-Cat/Z280 between 500°C and 550°C. From the kinetic model, the apparent activation energy for the conversion of naphtha to gases decreased from 21.2kcal/mol over E-Cat to 16.2kcal/mol over E-Cat/Z280 which indicates that Z280 facilitated the increased cracking of naphtha-range species to light olefins

Modeling and analysis of the Lurgi‐type methanol to propylene process: Optimization of olefin recycle

This work proposed a strategy to improve the yield of light olefins of industrial methanol to propylene process by reducing the olefins recycled back into the main reactor and appending an olefin cracking reactor. The heterogeneous fixed‐bed model was employed to simulate the reactors with a robust mathematical procedure developed to determine the reactor configuration and the recycle flow rates of the olefins. Two methods were proposed for the modulation: the recycle ratio and species of the olefins, respectively. Results show that the yield of C2–C3 olefins can be improved up to 70% from the basement of about 60% when the ratio is reduced from 100% to less than 23% or when only butene apart from pentene and hexene is recycled back into the main reactor, and the latter method is more effective as its catalyst requirement is seven times less than the former's in the appended cracking reactor. © 2016 American Institute of Chemical Engineers AIChE J, 63: 306–313, 2017

Production of olefinic diesel, lubricants, and propylene

HEU-1 zeolites with different SiO2/Al2O3 ratios (60–530) were in-situ synthesized and systematically evaluated in n-hexane catalytic cracking reaction. The influencing factors including SiO2/Al2O3 ratio, weight hourly space velocity and reaction temperature were investigated to optimize the light olefin yield, especially propylene. Compared to HZSM-48 and HZSM-5 zeolites with similar SiO2/Al2O3 ratios, HEU-1-300 (SiO2/Al2O3 = ca. 300), for example, displays much higher yield of ethylene plus propylene than HZSM-48 and comparable with HZSM-5. Furthermore, the propylene yield (35.6%) on it is higher than HZSM-5 by 9.0 percentage points, thus leading to higher propylene/ethylene ratio of 2.1. This excellent cracking performance of HEU-1-300 is ascribed to the combination of its moderate Brönsted acidity, due to the optimal SiO2/Al2O3 ratio, and unique framework topology. Moreover, both HEU-1 and HZSM-48 zeolites present much lower aromatics selectivity in the gas effluent than HZSM-5. For HEU-1 zeolite, it displays significant product shape selectivity due to its confined channel system, even though the large void space favors the formation of large intermediate species or aromatics precursors, while there is transition state shape selectivity for HZSM-48 structure which possesses no enough void space available to accommodate the large and complex hydrocarbons. HEU-1 topological structure also has pronounced effect on the formation and oxidation of coke deposition.

Synthesis of hierarchical SAPO-34 nanocrystals with improved catalytic performance for methanol to olefins

SAPO-34 molecular sieve was hydrothermally synthesized by using organosilane phenylaminopropyl-trimethoxysilane (PHAPTMS) as a part of silicon source and tetraethylammonium hydroxide as microporous template at 160°C. The XRD, SEM and N2 adsorption/desorption characterizations revealed the hierarchical SAPO-34 is a nanocrystal assembly of 50nm particles prepared in the system. The catalyst showed improved stability and unusual selectivity of propylene and butylene in methanol to olefins reaction by introducing the mesoporous structure and changing the surface acid sites distribution. The yield of light olefins in hydrocarbons was up to 86%, the selectivity of C3= and C4= reached more than 40% and 10%.

Light Products and H2-Rich Syngas over the Bifunctional Base Catalyst Derived from Petroleum Residue Cracking Gasification

Vacuum residue is utilized by a process involving the residue cracking and coke gasification regeneration. In this process, vacuum residue is first converted into the products of light olefins and light oils by catalytic cracking, and then the cracking-generated coke is gasified into H2-rich syngas by using a bifunctional base catalyst. Their cracking gasification effects of vacuum residue are studied in a dual fluidized bed reactor. The results show that the solid base catalysts could enhance light olefin yield (have high olefinicity) and inhibit the formation of coke in comparison with silica sand and a hydrothermal treatment zeolite catalyst (FCC catalyst). Furthermore, the catalyst prepared at a CaO/Al2O3 molar ratio of 12:7 displayed a better cracking effect than the one produced at the molar ratio of 1:1. The effects of the reaction temperature and the catalyst-to-oil ratio on the distribution of cracking liquid from vacuum residue solid base cracking are discussed. The results showed that the heavy...

Catalytic cracking of n-hexane over HEU-1 zeolite for selective propylene production: Optimizing the SiO2/Al2O3 ratio by in-situ synthesis

HEU-1 zeolites with different SiO2/Al2O3 ratios (60–530) were in-situ synthesized and systematically evaluated in n-hexane catalytic cracking reaction. The influencing factors including SiO2/Al2O3 ratio, weight hourly space velocity and reaction temperature were investigated to optimize the light olefin yield, especially propylene. Compared to HZSM-48 and HZSM-5 zeolites with similar SiO2/Al2O3 ratios, HEU-1-300 (SiO2/Al2O3=ca. 300), for example, displays much higher yield of ethylene plus propylene than HZSM-48 and comparable with HZSM-5. Furthermore, the propylene yield (35.6%) on it is higher than HZSM-5 by 9.0 percentage points, thus leading to higher propylene/ethylene ratio of 2.1. This excellent cracking performance of HEU-1-300 is ascribed to the combination of its moderate Brönsted acidity, due to the optimal SiO2/Al2O3 ratio, and unique framework topology. Moreover, both HEU-1 and HZSM-48 zeolites present much lower aromatics selectivity in the gas effluent than HZSM-5. For HEU-1 zeolite, it displays significant product shape selectivity due to its confined channel system, even though the large void space favors the formation of large intermediate species or aromatics precursors, while there is transition state shape selectivity for HZSM-48 structure which possesses no enough void space available to accommodate the large and complex hydrocarbons. HEU-1 topological structure also has pronounced effect on the formation and oxidation of coke deposition.

The influence of modification methods on the catalytic cracking of LPG over lanthanum and phosphorus modified HZSM-5 catalysts

In the present study, the effect of various modification methods on the activity of ZSM-5 modified catalysts has been studied in catalytic cracking (CC) of LPG. Lanthanum (La) has been loaded in HZSM-5 catalyst using ion exchange, and wet impregnation, and phosphorus (P) has been introduced by wet impregnation and dry impregnation methods. Physico-chemical properties of modified samples were evaluated by using XRF, ICP-OES, XRD, FT-IR, physical N2 adsorption and NH3-TPD characterization methods. Studying the catalytic performance of the samples revealed that wet impregnation could result in better efficiency than dry impregnation and ion-exchange methods. Afterwards, the dual site catalysts containing both La and P have been prepared using wet impregnation and physical mixture processes. It was found that HZSM-5 catalyst modified by successive wet impregnation of La and P could led to the higher conversion and yield of light olefins (ethylene + propylene) compared to the other samples. At the reaction temperature of 650 °C and GHSV of 433 ml min−1/gcat over the mentioned catalyst (in the presence of N2) yield of total light olefins and selectivity was acquired to be 51% and 62%, respectively.

Synthesis of SAPO-18 with low acidic strength and its application in conversion of dimethylether to olefins

SAPO-18 molecular sieve was synthesized by a dry gel conversion (DGC) and hydrothermal (HT) synthesis methods using methyltriethoxysilane as the only Si source (DGC-Me-SAPO-18 and HT-Me-SAPO-18). Their physicochemical and catalytic properties on dimethylether-to-olefin (DTO) reaction were compared with those of conventional SAPO-18 molecular sieves synthesized by a hydrothermal synthesis method (HT-SAPO-18). An NH3-TPD measurement revealed that the desorption peak position of Brønsted acid of the Me-SAPO-18 samples moved to lower temperature, indicating that Brønsted acidic strength of the Me-SAPO-18 samples was lower than that of the HT-SAPO-18 samples. The DME conversions and yields of light olefins over DGC-Me-SAPO-18 decreased at a slower rate than those of HT-SAPO-18. The decreased acidic strength and flake-like morphology of DGC-Me-SAPO-18 could retard the coke formation, leading to the prolonged catalytic lifetime.

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.

The Fabrication of Ga2O3/ZSM-5 Hollow Fibers for Efficient Catalytic Conversion of n-Butane into Light Olefins and Aromatics

In this study, the dehydrogenation component of Ga2O3 was introduced into ZSM-5 nanocrystals to prepare Ga2O3/ZSM-5 hollow fiber-based bifunctional catalysts. The physicochemical features of as-prepared catalysts were characterized by means of XRD, BET, SEM, STEM, NH3-TPD, etc., and their performances for the catalytic conversion of n-butane to produce light olefins and aromatics were investigated. The results indicated that a very small amount of gallium can cause a marked enhancement in the catalytic activity of ZSM-5 because of the synergistic effect of the dehydrogenation and aromatization properties of Ga2O3 and the cracking function of ZSM-5. Compared with Ga2O3/ZSM-5 nanoparticles, the unique hierarchical macro-meso-microporosity of the as-prepared hollow fibers can effectively enlarge the bifunctionality by enhancing the accessibility of active sites and the diffusion. Consequently, Ga2O3/ZSM-5 hollow fibers show excellent catalytic conversion of n-butane, with the highest yield of light olefins plus aromatics at 600 °C by 87.6%, which is 56.3%, 24.6%, and 13.3% higher than that of ZSM-5, ZSM-5 zeolite fibers, and Ga2O3/ZSM-5, respectively.

Thorough study of the effect of metal-incorporated SAPO-34 molecular sieves on catalytic performances in MTO process

SAPO-34 and MeAPSO-34s (Me=Fe, Co, Ni, La and Ce) molecular sieves were synthesized and used as catalysts for conversion of methanol to light olefins. X-ray diffraction, scanning electron microscopy, nitrogen adsorption–desorption inductively coupled plasma mass spectrometry, Fourier transform infrared spectroscopy and temperature programmed desorption techniques were used to characterize the synthesized catalysts. Thermogravimetric analysis was used to investigate the amount of coke deposited on the spent catalysts during the reaction. The synthesized MeAPSO-34s had the same chabazite topology structure, while metal incorporation gave rise to the different micropore area and acidity. All the SAPO-34 and MeAPSO-34 molecular sieves were very active and selective catalyst for light olefins production. Metal incorporation improved the catalyst lifetime and favored the ethylene and propylene product. Concerning the yield of light olefins at 425°C and 1bar, NiAPSO-34 favored ethylene production and CeAPSO-34 and LaAPSO-34 were helpful for propylene production. Light olefins yield decreased with time on stream for all the samples; although, this decrease rate is lower for MeAPSO-34 than for the parent SAPO-34. The catalyst lifetime increased in an order as follows: Ce->La->Co->Ni->Fe->SAPO-34. The rare earth modified catalysts exhibited lower methanation than parent SAPO-34 and transition metal modified catalysts.

Effect of phosphorus on methane production in LPG catalytic cracking over modified-structure ZSM-5

Phosphorus was loaded by wet impregnation method on zeolite ZSM-5 created by template-free technique. Mesopores were produced using 30 wt.% of carbon nanotube template. The synthesized catalysts were characterized by means of XRD, XRF, FE-SEM, BET and NH3-TPD techniques. LPG catalytic cracking was conducted in fixed-bed reactor by using P-impregnated ZSM-5 zeolite. Since methane production was related to P amount, the amount of this element on the synthesized zeolite was optimized. Minimum methane production occurred with 0.5 wt.% of phosphorus. The resulting mesopores not only increase the availability of materials to catalyst active sites, but also increase the coke yield and deactivation of catalyst at reaction initiation, as well. Hence, to decrease coke formation, the steaming process dealuminated the mesopores while leaving micropores untouched, and so, mesopores were deactivated for coke formation. Modification of zeolite by phosphorus and steaming process increased light olefins yield and selectivity to 50% and 60%, respectively. In addition, coke formation declined from 14% on ZSM-5 to 7% on ZSM-5 CNT(30) P(0.5) steam (1 h) zeolite.

Catalytic Performance of SAPO-34 Catalysts of Different Crystal Sizes in Methanol-to-Olefins Reactions: Effects of Synthetic Parameters

The catalytic performance of SAPO-34 catalysts which were synthesised hydrothermally under different conditions was investigated in methanol-to-olefins reactions. The significance of template, silicon sources and crystallisation time on catalytic performance, and deactivation of SAPO-34 catalysts, were studied. High methanol conversion and yield of light olefins were obtained over the nano-sized catalyst synthesised with tetraethylammonium hydroxide as template source and tetraethyl orthosilicate as silica source with a crystallisation time of 24 h, owing to its higher crystallinity and smaller crystal size. The SAPO-34 catalysts with larger sizes of crystals deactivate rapidly, while smaller crystals retain their activity for a longer time.

Methanol conversion over SAPO-34 catalysts; Systematic study of temperature, space–time, and initial gel composition on product distribution and stability

The effect of temperature, space–time and the molar ratio of morphine to alumina over the SAPO-34 catalyst in methanol to olefin (MTO) process and catalytic stability were studied. Response surface methodology coupled with central composite design (CCD) was used to investigate the exact effect of main factor and their interactions. From the CCD studies, the effects of temperature and space–time were concluded to be the key factors influencing initial light olefins yield, while the molar ratio of morpholine to alumina had the most important role in catalytic stability compared with the other two variables. It was found that an optimum for initial propylene yield resulted from increasing temperature and space–time. However, increasing temperature and space time resulted in increasing initial ethylene yield. Furthermore, optimum points were found for the reduced ethylene and reduced propylene (catalytic stability). The best conditions for simultaneous maximization of initial ethylene and initial propylene yields are at T=466°C, space–time=12.08 gcathrmolMeOH and the molar ratio of morphine to alumina=0.94. The optimal set, T=411°C, space–time=12.24 gcathrmolMeOH and the molar ratio of morphine to alumina=0. 92, with the goal of minimizing both the reduction of ethylene and propylene after processing 8g of methanol per unit weight of catalyst (M=8) was achieved.