Total Light Olefins Research Articles

Preparation of H-[B]- ZSM -5 zeolites by hydrothermal method as a highly stable and selective catalyst for methanol to propylene (MTP) conversion

A series of high-silica boron-containing H-ZSM-5 zeolites were prepared employing the hydrothermal method. Subsequently, the physico-chemical characteristics of prepared catalysts were comprehensively studied through diverse analytical methods, followed by evaluation of catalytic performance in the methanol-to-propylene (MTP) reaction. The results demonstrated that incorporation of boron into the H-ZSM-5 zeolite induced the reduction in the total surface area and pore volume, accompanied by a raise in the density of weak acid sites. Also, the optimal point for boron content has been recognized at molar coefficient of B2O3/SiO2 = 0.025 for obtaining the highest H-[B]-ZSM-5 performance in MTP process. In comparison to unmodified H-ZSM-5, the optimized H-[B]-ZSM-5 yielded the higher selectivity towards propylene (42.9 % versus 40.1 %) and total light olefins (72.1 % versus 69.5 %), as well as propylene to ethylene ratio (8.1 versus 7.8) with a considerable reduction in selectivity toward C1–C4 alkanes (3.9 % versus 4.2 %) and heavy hydrocarbons (24.1 % versus 26.4 %). Also, the optimized H-[B]-ZSM-5 catalyst exhibited an extended lifetime of 988 h in the MTP process, surpassing the lifetime of unmodified H-ZSM-5 (936 h). These results suggest the optimal point for boron content at B2O3/SiO2 = 0.025 to attain the superior catalytic performance, specifically in terms of propylene yield and catalyst lifetime during MTP process.

Acid Treatment to Improve Total Light Olefins Selectivity of HZSM-5 Catalyst in Methanol to Olefins (MTO) Reaction

Acid Treatment to Improve Total Light Olefins Selectivity of HZSM-5 Catalyst in Methanol to Olefins (MTO) Reaction

Modeling and simulation analysis of methanol conversion to olefins (MTO): A critical comparison of a honeycomb monolith and a fixed-bed of cylindrical extruded HZSM-5 catalyst

The performance of a honeycomb monolith and a fixed-bed of cylindrical extruded HZSM-5 catalyst for the methanol to olefins process (MTO) are evaluated and compared using two-scale two-dimensional heterogeneous models in adiabatic and diabatic operations considering two approaches of “restricted comparison” and “free comparison”. The 53-step elementary reaction mechanism of Mihail and coworkers is used to model the MTO reactions. The effects of space-time (0.1–5 s), feed water content (up to 60 mol%), and monolith cell density (200–600 cpsi) on the catalyst temperature, feed conversion, and selectivity and yield of olefins are investigated. “Restricted comparison” indicates that the feed conversion and selectivity and yield of the total olefins in the monolithic reactor are greater than the fixed-bed with a maximum discrepancy of 5%. There is an optimum space-time of ~ 0.3 s at which the yield of total light olefins in the monolith and fixed-bed reactors achieves the maximum values of 0.45 and 0.43, respectively. The results of “free comparison” reveal that a 600 cpsi monolith can produce ~ 43% more light olefins using ~ 75% less catalyst mass at the optimal space-time of 0.3 s compare with a fixed-bed reactor at an identical specific surface area.

Preparation of hierarchical H-[B]-ZSM-5 zeolites by a desilication method as a highly selective catalyst for conversion of methanol to propylene

A hydrothermal route was exploited to prepare high-silica H-ZSM-5 as well as H-[B]-ZSM-5 zeolites, and the boron-modified type was then desilicated with alkaline treatment. The properties of catalysts were investigated by different techniques, and the catalytic performance was evaluated in the methanol to propylene reaction. The effects of three critical desilication parameters, including the alkali concentration, temperature, and treatment time were evaluated on propylene selectivity and mesopore volume. The results of characterizations evinced that the incorporation of B in the H-ZSM-5 zeolite reduced the total surface area as well as the pore volume of the H-[B]-ZSM-5 sample and increased the external surface area. Furthermore, a significant increase in the weak acid site density for the boron-containing specimen was observed. Also, the external surface area and mesopore volume of the desilicated specimens underwent an increment, while the micropore volume was almost constant. As opposed to the H-[B]-ZSM-5 catalyst, the optimum desilicated catalyst exhibited higher selectivity to propylene (48.8 vs. 40.7%) and total light olefins (76.9 vs. 71.2%), and a higher ratio of propylene to ethylene (5.66 vs. 4.15). The optimum catalyst had a higher lifetime in the MTP reaction (867 h) as opposed to the microporous H-[B]-ZSM-5 catalyst (498 h).

Oxidative dehydrogenation of propane using layered borosilicate zeolite as the active and selective catalyst

Oxidative dehydrogenation (ODH) of propane to propylene offers a promising large-scale alternative to direct dehydrogenation. The reported metal oxides catalysts generally cause over-oxidation of propylene to COx, thus hindering the commercialization of ODH processes. In this study, a layered borosilicate zeolite was demonstrated as highly active and selective catalyst for the oxidative dehydrogenation of propane, showing a propylene selectivity of 83.6% and the total light olefins (propylene and ethylene) selectivity of 91.2% at a propane conversion of 3.9%. Further, at a propane conversion of 15.6%, the catalyst exhibited a propylene selectivity of 80.4% and the total light olefins selectivity of 91.6% at 530 °C. Structural characterization revealed that the abundance of defective trigonal boron species (B[3]a and B[3]b) was responsible for the activity of propane ODH.

Dimethyl Ether Conversion to Light Olefins on Zeolite Catalysts: Effect of MFI-Type Zeolite Nature and SiO2/Al2O3 Molar Ratio on Catalyst Efficiency

The physicochemical and catalytic properties of magnesium-containing zeolite catalysts based on MFI-type zeolites (ZSM-5 and CBV) were compared. The presence of larger mesopores volume in MgCBV was found to decrease selectivity towards light olefins. In order to improve the catalytic properties of MgCBV, the effect of SiO2/Al2O3 molar ratio of CBV (SiO2/Al2O3 = 30, 55, 80 and 300) on its physicochemical and catalytic properties in the reaction of the dimethyl ether (DME) into light olefins was studied. Increasing SiO2/Al2O3 molar ratio from 30 to 80, was shown not change practically the DME conversion and olefin selectivity, but under a SiO2/Al2O3 molar ratio of 300, DME conversion significantly reduces, olefin selectivity increases, while the ethylene/propylene ratio decreases twice. By changing residence time, DME conversion increases under high total light olefins selectivity, while the ethylene/propylene ratio raises with increasing residence time.

Modification of H-[B]-ZSM-5 zeolite for methanol to propylene (MTP) conversion: Investigation of extrusion and steaming treatments on physicochemical characteristics and catalytic performance

Abstract High-silica H-[B]-ZSM-5 zeolite was synthesized by a hydrothermal method and was then extruded by a conventional process. The influence of mesoporosity formation and acidity modification was investigated using extrusion and combined extrusion-steam treatment over the synthesized zeolite. The catalysts were characterized by BET, FE-SEM, TGA, PXRD and NH3-TPD techniques. The catalytic performance of the powder H-[B]-ZSM-5 (BZP), extruded (BZE) and steam-treated extruded (BZEH) samples was evaluated in the methanol to propylene (MTP) conversion reaction. The reactions were performed in a fixed-bed reactor at 480 °C using a feed containing a mixture of 50 wt% methanol in water with a methanol weight hourly space velocity (WHSV) of 0.9 h−1. The results showed that extrusion of H-[B]-ZSM-5 with alumina sol as a binder followed by steam-treatment led to the formation of narrow and uniform mesoporosity without severely destructing the crystal structure. The life time of the BZEH catalyst (750 h) was higher than that of BZE (520 h) and BZP (580 h) samples. This considerable enhancement of the lifetime could be attributed to the synergetic effect of extruding and steaming of H-[B]-ZSM-5 zeolite, leading to weakening of the acid sites strength and reduction of strong/weak acid sites ratio as well as formation of mesoporous structure, which are helpful for attenuating coke deposition in the micropore channels even at a high coking level. Besides, BZEH exhibited higher selectivity to propylene, butylenes and total light olefins, while its selectivity to C1–C4 alkanes and ethylene was relatively lower. The insights attained in this work would help to design a promising catalyst for methanol to propylene process.

Novel hierarchical HZSM-5 zeolites prepared by combining desilication and steaming modification for converting methanol to propylene process

The effect of mesoporosity formation and acidity modification have been investigated by desilication and combined desilication–dealumination treatments over highly siliceous zeolite HZSM-5 (Si/Al = 200) and its catalytic performance has been studied in the conversion of methanol to propylene (MTP) reaction. Desilication of a conventional microporous HZSM-5 catalyst was performed using NaOH, mixtures of NaOH and tetrapropylammonium hydroxide (TPAOH), and mixtures of NaOH and tetrabutylammonium hydroxide (TBAOH) with different ratios. Subsequent mild steaming treatment has been used to modify acidity of the selected samples. The physicochemical properties of all samples were characterized by XRD, FE-SEM, BET and NH3-TPD methods. Textural and acidity properties confirmed that TBAOH is more effective than TPAOH in the mesoporosity formation, micropore volume preservation, and acidity modification. Steaming treatment after desilication over the sample with TPAOH/(NaOH + TPAOH) ratio of 0.4, led to increase in selectivities to propylene from 38.4 to 41.3%, and total light olefins from 69.4 to 76.6%, while it led to decrease in C5+ components selectivity from 14.8 to 10.1%. The combined alkaline-steam treatment over the sample with TBAOH/(NaOH + TBAOH) ratio of 0.2 compared to the parent one led to considerable higher selectivities to propylene (44.8 vs. 30.7%), total light olefins (84.1 vs. 57.9%), as well as lower selectivities to C5+ components (7.4% vs. 27.1%). Moreover, this sample showed double lifetime (830 h) in MTP reaction compared to the conventional micropore ZSM-5 catalyst (425 h). The results showed that desilication led to a remarkable mesoporosity development, while steaming treatment generally influenced on the HZSM-5 acidity. Therefore, the combined alkaline-steam treatment leads to HZSM-5 zeolite formation with tailored pore architecture and surface acidic properties.

Catalytic transformation of ethylene to propylene and butene over an acidic Ca-incorporated composite nanocatalyst

The direct conversion of ethylene to propylene (ETP reaction) has become critically important due to the growing demands for propylene as one of the key building blocks in the petrochemical industries and the depletion of appropriate resources for propylene production. In the present study, an acidic metal-incorporated composite nanocatalyst has been prepared and characterized using XRD, FTIR, FESEM, EDX, NH3-TPD, and N2 physisorption analyses and applied to the ETP reaction. The maximum conversion of 77.8% was achieved over the catalyst at 723 K. The highest propylene yield (34.6 wt%) was obtained at 773 K, however. An increasing trend with temperature (573–823 K) was evident for the total light olefins selectivity, which amounted to 78.7 wt% at 823 K. The reaction rate increased constantly to 258 mol/(kg s) with the increase in the ethylene partial pressure. The remarkable performance of the composite catalyst in terms of propylene and butenes yields and its distinguished stability during the ETP reaction compared to the closely relevant HZSM-5 and HSAPO-34 counterparts, was attributed to both an appropriate porosity and a good compromise between the strength and amount of the acidic sites to an interestingly one-mode moderate acidity.

Seed-fused ZSM-5 nanosheet as a superior MTP catalyst: Synergy of micro/mesopore and inter/external acidity

Abstract ZSM-5 nanosheet (NS) has an optimal diffusivity due to b-axis oriented two-dimensional structure, but the extra large external acidity results in the deactivation of the catalyst in methanol to propylene (MTP) reaction. The seed-fused ZSM-5 nanosheets (CNS-x) were synthesized by a seed induced method, the performance of samples was compared with one without seed. Further, the B-incorporation sample (B-CNS-5) was prepared with 5 wt% seed and boron acid. Revealing the importance of fusion effect of ZSM-5 seed on the nanosheet, especially the change in microstructure properties and its structure-effect relationship, which is not explicitly documented in previous work. With the seed amount increasing from 5 to 30 wt % in the gel, the crystallization time is largely shortened, along with the change in the resulting nanosheet, such as reduction of particle size and acid strength/external surface acidity, an increase of over 50% micropore volume. The CNS-x samples perform longer catalytic lifetime (168–226 h) compared to NS (103 h). CNS-5 displays an extremely high selectivity to propylene (C = 3) ∼54% and total light olefins (C = 2-C = 4) of∼84%. A super sample B-CNS-5 exhibits longest lifetime (302 h), achieving highest C = 3 yield due to change in the acid sites distribution and increase of extra weak acid sites. For the converted methanol (g/gcatalyst), the result is B-CNS-5 (966) > CNS-5 (525)> NS (324). In converse, the average coke selectivity (Sav, C) is B-CNS-5 (0.18‰)

The conversion of biomass to light olefins on Fe-modified ZSM-5 catalyst: Effect of pyrolysis parameters

Light olefins are the key building blocks for the petrochemical industry. In this study, the effects of in-situ and ex-situ process, temperature, Fe loading, catalyst to feed ratio and gas flow rate on the olefins carbon yield and selectivity were explored. The results showed that Fe-modified ZSM-5 catalyst increased the olefins yield significantly, and the ex-situ process was much better than in-situ. With the increasing of temperature, Fe-loading amount, catalyst to feed ratio, and gas flow rate, the carbon yields of light olefins were firstly increased and further decreased. The maximum carbon yield of light olefins (6.98% C-mol) was obtained at the pyrolysis temperature of 600°C, catalyst to feed ratio of 2, gas flow rate of 100ml/min, and 3wt% Fe/ZSM-5 for cellulose. The selectivity of C2H4 was more than 60% for all feedstock, and the total light olefins followed the decreasing order of cellulose, corn stalk, hemicelluloses and lignin.

High efficient mesoporous HZSM-5 nanocatalyst development through desilication with mixed alkaline solution for methanol to olefin reaction

Methanol to olefin (MTO) process is a non-oil route for the light olefins production. We report the mesoporous and high siliceous HZSM-5 nanocatalyst development through the new desilication process including the mixed alkaline solution. The properties of nanocatalysts were characterized using TGA/DTA, XRD, ICP, FE-SEM, BET, FT-IR, and NH3-TPD techniques. FE-SEM images represent the spherical morphology of parent nanocatalyst including smooth surface. The XRD analysis confirms that applied desilication does not change the typical MFI-type structure of ZSM-5 nanocatalysts. The BET and NH3-TPD results show that mixed alkaline solution including 40 wt% TPAOH results in the best adjustment of textural (299.7 m2/g) and acidity (strong/weak ratio of 0.21) properties, respectively. The PHZ-NaTP0.4 nanocatalyst represents the highest methanol conversion (99.2%), propylene selectivity (48.3%), C3 =/C2 = molar ratio (7.4) as well as lowest selectivity to C1–C4 alkanes (4.6%) for long time on stream (170 h). The low selectivity of light alkanes (C1–C4) and high total light olefins (ca. 75%) confirm the stable performance of nanocatalyst. Consequently, the developed PHZ-NaTP0.4 nanocatalyst is a high efficient MTO catalyst and can be candidate for commercial scale up.

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.

The effects of SiO2/Al2O3 and H2O/Al2O3 molar ratios on SAPO-34 catalysts in methanol to olefins (MTO) process using experimental design

To investigate the effects of silicon and water content on SAPO-34 catalyst, a number of experiments by using response surface methodology of molar ratios of SiO2/Al2O3=0.1–0.6 and H2O/Al2O3=50–120 were performed. The catalytic performances of prepared SAPO-34 samples at 410°C and 30wt.% methanol in water for MTO process were investigated. Due to relatively high crystallinity and small crystal size (1.3μm); SiO2/Al2O3=0.17 and H2O/Al2O3=109.75 catalyst showed high total light olefins selectivity (71.45%). ANOVA results indicated that the light olefins selectivity was influenced more by changing of SiO2/Al2O3 molar ratio rather of H2O/Al2O3 molar ratio.

Synthesis and catalytic cracking performance of Fe/Ti-ZSM-5 zeolite from attapulgite mineral

Fe/Ti-ZSM-5 zeolite was synthesized successfully from treated attapulgite (ATP). This mineral consists of amorphous silica containing Fe and Ti species. X-ray diffraction patterns, scanning electron microscopy images, and nitrogen sorption isotherms indicate that the sample has a typical MFI structure, high crystallinity, and large specific surface area. Temperature-programmed desorption of ammonia and H2 temperature-programmed reduction indicates that the Fe/Ti-ZSM-5 zeolite is strongly acidic and has superior redox properties. More importantly, compared with conventional ZSM-5 zeolite, Fe/Ti-ZSM-5 performs well, resulting in an increase in yield of 0.21% propylene and 0.33% total light olefins in the catalytic cracking of Canadian LGO (light gas oil). These results suggest that the presence of Fe and Ti species in ZSM-5 zeolite is favorable for enhancing light olefin yields, which is potentially important for oil refining in the future.

Influence of combined alkaline treatment and Fe–Ti-loading modification on ZSM-5 zeolite and its catalytic performance in light olefin production

Alkali-treatment and Fe–Ti-loading were used to modify ZSM-5 zeolite. It was found that alkali-treatment created mesopore and Fe–Ti-loading improved the redox property of ZSM-5 catalyst, although both modifications led to a reduction of the total acid sites amount. The catalytic performance test indicated that the coexistence of meso–microporosity and Fe–Ti-loading on ZSM-5 catalyst is benefit to improve the yield of light olefins in catalytic cracking. The catalyst containing the combined modified ZSM-5 increased the propylene yield by 0.55wt% and total light olefins yield by 0.69wt% in catalytic cracking of Canadian LGO (light gas oil), compared with the reference HZSM-5.

Kinetics of Catalytic Pyrolysis of Heavy Gas Oil Derived from Canadian Synthetic Crude Oil

The catalytic pyrolysis of heavy gas oil derived from Canadian synthetic crude oil on zeolite catalyst was conducted in a confined fluidized bed reactor. The optimal reaction temperature, weight hourly space velocity, steam-to-oil weight ratio, and catalyst-to-oil weight ratio were 660 °C, 9.5 h–1, 0.6, and 20, respectively. The yield of total light olefins was 36.4 wt % under these optimal conditions. The overall reactants and products were classified into seven species, and a seven-lump kinetic model with 15 rate constants and a catalyst deactivation constant was proposed. Kinetic constants at 620, 640, 660, and 680 °C were estimated by a nonlinear least-squares regression method. Preexponential factors and apparent activation energies were then calculated according to the Arrhenius equation. The feed lump had larger rate constants and smaller apparent activation energies than did the intermediate product lumps. The seven-lump kinetic model showed high calculation precision and the predicted yields agre...

Cracking Performance of Gasoline and Diesel Fractions from Catalytic Pyrolysis of Heavy Gas Oil Derived from Canadian Synthetic Crude Oil

The secondary cracking performance of gasoline and diesel fractions from the catalytic pyrolysis of heavy gas oil derived from Canadian synthetic crude oil was investigated. Both diesel and gasoline fractions showed poor cracking performance. The feed conversion of the diesel fraction was below 51 wt %, and the yield of total light olefins was below 11 wt %. Meanwhile, the feed conversion of the gasoline fraction was below 30 wt % and the yield of total light olefins was below 7 wt %. The selectivity of total light olefins at 660 °C was only 22% for both fractions, and the selectivity of dry gas at 660 °C reached 25% for the diesel fraction and 34% for the gasoline fraction. The selectivity of coke at 660 °C reached 26% for the diesel fraction and 16% for the gasoline fraction. The diesel and gasoline fractions could partly crack to lighter components and could partly condense to heavier components. The condensation reaction played an important role in catalytic pyrolysis, and the selectivity of condensation products at 660 °C reached 42% for the cracking of the diesel fraction and 55% for the cracking of the gasoline fraction. The monomolecular cracking is the predominant cracking type, and both the free radical and the carbonium ion mechanisms play an important role under the experimental conditions.

Cracking Performance and Feed Characterization Study of Catalytic Pyrolysis for Light Olefin Production

The catalytic pyrolysis of heavy oils, gas oils, cracked diesel and gasoline fractions was investigated in a confined fluidized-bed reactor. The feed with a high H/C atomic ratio and low aromaticity showed good cracking performance, high feed conversion, and high yield and selectivity of total light olefins (i.e., ethene, propene, and butene). The cracked diesel and gasoline fractions with a low H/C atomic ratio and high aromaticity showed poor secondary cracking performance. A characterization parameter (KCP) was proposed to characterize the cracking performance of various feedstocks. The yield of total light olefins increased with an increase in KCP, despite the catalytic or thermal pyrolysis. KCP could be used as a criterion to evaluate the cracking performance of a feed for the production of light olefins. The cracking performance of a feed was considered desirable for KCP above 3.6 and undesirable for KCP below 2.8. Besides KCP, the United States Bureau of Mineral Correlation Index (BMCI) was also su...

Pyrolysis Performances of Catalytic Cracking Naphtha and Coker Naphtha on Inert Carriers and an Active Catalyst

The pyrolysis performance of catalytic cracking naphtha and coker naphtha on different carriers and an active catalyst was investigated in a confined fluidized bed reactor. For the pyrolysis of catalytic cracking naphtha on quartz grain, the yield of total light olefins increased with the enhancement of temperature, while it varied slightly with increasing weight hourly space velocity (WHSV) and steam/oil weight ratio. The optimal reaction temperature, WHSV, and steam/oil weight ratio were 700 °C, 5.7 h−1, and 0.5, respectively. The selectivity of total light olefins of coker naphtha was better than that of catalytic cracking naphtha under the optimal reaction conditions. The surface area and pore size of the inert carrier showed little effect on the pyrolysis performance. The introduction of the active catalyst could improve the conversion and the yield of total light olefins.