Direct Synthesis Of Isoparaffin Research Articles

Core–Shell Metal Zeolite Composite Catalysts for In Situ Processing of Fischer–Tropsch Hydrocarbons to Gasoline Type Fuels

Fischer–Tropsch synthesis has two main challenges related to direct production of gasoline fuels. First, the chain length distribution of the products follows a broad and unselective Anderson–Schulz–Flory distribution. Second, mostly linear hydrocarbons are formed in the Fischer–Tropsch reaction, thus requiring isomerization while manufacturing gasoline fuels. The present paper addresses a synthetic strategy for the preparation of hierarchical metal and zeolite nanocomposite catalysts for direct synthesis of iso-paraffins from syngas. The nanocomposites are synthesized in three steps. In the first step, the parent (core) zeolite is etched with an ammonium fluoride solution. The etching creates small mesopores inside the zeolite crystals. In the second step, the Ru nanoparticles prepared using water-in-oil microemulsion are deposited in the mesopores of the zeolite. In the third step, a zeolite shell of MFI-type zeolites (silicalite-1 or ZSM-5) is grown on the parent zeolite crystals coating both the etched surface and metallic nanoparticles. Thus, the metal nanoparticles become entirely encapsulated inside the zeolite matrix. Most important parameters such as ruthenium content, zeolite mesoporosity, and more particularly, the acidity of the catalyst shell, which affect the catalytic performance of the synthesized nanocomposite materials in low-temperature Fischer–Tropsch synthesis were identified in this work. The higher relative amount of iso-paraffins was observed on the catalysts containing a shell of ZSM-5. The proximity between metal and acid sites in the zeolite shell of the nanocomposite catalysts is a crucial parameter for the design of efficient metal zeolite bifunctional catalysts for selective synthesis of gasoline-type fuels via Fischer–Tropsch synthesis, while the acidity of the catalyst core has only a limited impact on the catalytic performance.

Direct synthesis of iso-paraffin fuel from palm oil on mixed heterogeneous acid and base catalysts

This study focused on the synthesis of hydrocarbon fuel containing a high iso-paraffin and very low oxygen content from palm oil using a mixed acid–base catalyst. The catalysts were characterized by nitrogen adsorption–desorption, X-ray diffraction, hydrogen-temperature programmed reduction, carbon dioxide- and ammonia-temperature programmed desorption as well as thermogravimetric analysis. Solid base (MgO, CaO, SiO2, and Na2SiO3) and solid acid (HY, H-beta, HZSM5, and Al2O3) catalysts were individually evaluated for their catalytic activity in a semi-batch reactor in terms of the deoxygenation level of palm oil product. The best acid and alkali catalyst were then selected for mixing at different weight ratios and re-tested for their tandem catalytic performance in terms of the deoxygenation activity. Finally, the reaction temperature (400–460 °C), pressure in a nitrogen or hydrogen gas atmosphere and residence time were optimized. The main components in the liquid product obtained were normal paraffins, iso-paraffins, olefins and aromatics. For the single base catalysts, a liquid yield of higher than 65 wt% was obtained at a 460 °C using MgO catalyst, which also realized an excellent oxygen removal through decarboxylation and decarbonylation. For the single acid catalysts, the zeolite beta catalysts reached a liquid yield of around 55 wt% with high iso-paraffin content. The optimal MgO:beta zeolite weight ratio for the acid–base hybrid catalyst was 3:1, which resulted in a low oxygen content in the products with a high iso-paraffin (35%) content.

Design of a Hierarchical Meso/Macroporous Zeolite‐Supported Cobalt Catalyst for the Enhanced Direct Synthesis of Isoparaffins from Syngas

AbstractA hierarchical meso/macroporous zeolite‐supported Co catalyst (Co/ASB) was designed and employed for the direct synthesis of isoparaffins. The hierarchical porous zeolite (ASB) was developed by a steam‐assisted crystallization method using alumina‐modified meso/macroporous silica as the precursor. Structural characterization indicated that the as‐synthesized ASB exhibited nanosized β‐zeolite crystallites and a hierarchical meso/macroporous structure. The activity of the Co/ASB catalyst was much higher than that of conventional Co catalysts supported on SiO2 (Co/SiO2) and H‐β‐zeolite (Co/B). A high isoparaffins selectivity of 30.5 % was obtained from Co/ASB because of the hydrocracking/isomerization of long‐chain hydrocarbons at the strong acidic sites of the β‐zeolite. Furthermore, as a result of the fast diffusion of syngas in the unique hierarchical pores, the methane selectivity of Co/ASB was lower than that of Co/B.

Preparation and performance of Co based capsule catalyst with the zeolite shell sputtered by Pd for direct isoparaffin synthesis from syngas

The mm-sized capsule catalyst Co/SiO2-Z with the H-type zeolite (HZSM-5) as the shell, and the Co/SiO2-Z-Sp-Pd capsule catalyst with Pd loaded by sputtering method, as well as the Co/SiO2-Z-IW-Pd capsule catalyst, loading the Pd by incipient wetness impregnation, were prepared and used for isoparaffin direct synthesis by Fischer–Tropsch synthesis reaction from syngas with H2/CO ratio of 2/1 at 1.0MPa and 533K. The analysis results of XRD, SEM, EDS and NH3-TPD showed that a compact HZSM-5 shell was formed on the Co/SiO2 pellet, and the metallic Pd was well sputtered on the surface of the HZSM-5 shell for the Co/SiO2-Z-Sp-Pd catalyst. The isoparaffin and olefin selectivity increased in the FTS reactions on the HZSM-5 capsule catalyst than on the Co/SiO2 catalyst. The selectivity of isoparaffins increased, and the selectivity of olefins decreased when using the Co/SiO2-Z-Sp-Pd catalyst, compared with the Co/SiO2-Z catalyst or the Co/SiO2-Z-IW-Pd catalyst, because metallic Pd introduced by sputtering on the zeolite shell could hydrogenate olefins efficiently. It was suitable to use the sputtering method for the preparation of the zeolite capsule catalyst loaded with metallic Pd, as conventional impregnation method could not reduce Pd cation due to the strong interaction from zeolite surface. The CO conversion, CH4 and CO2 selectivity on the catalyst of Co/SiO2-Z-Sp-Pd increased with temperature increasing from 513K to 553K. At elevated temperature, the isoparaffin selectivity also increased while the olefin selectivity was suppressed.

H-type zeolite coated iron-based multiple-functional catalyst for direct synthesis of middle isoparaffins from syngas

A compact, integral zeolite shell of H-ZSM-5 was directly crystallized on the surface of fused-iron catalyst pellet by a hydrothermal synthesis method. The synthesized catalyst has a core–shell structure without pinholes and cracks. For the reaction of direct synthesis of isoparaffin from syngas, the formation of C 10+ hydrocarbons is suppressed completely on this core–shell catalyst, and the middle isoparaffins become the main products. Especially, desirable low methane selectivity is achieved. The core–shell structure of the catalyst provides a tailor-made confined reaction environment with spatially confined effect and shape selectivity, where isoparaffins escaping from outer surface of one core–shell catalyst hardly enter another core–shell catalyst via surface zeolite shell, due to its large steric obstacle, ensuring the elevated isoparaffin selectivity. Furthermore, this type of core–shell catalyst has very high membrane area per unit reactor volume and easy to be prepared, in contrast to the conventional membrane reactor.

One-step synthesis of H–β zeolite-enwrapped Co/Al 2O 3 Fischer–Tropsch catalyst with high spatial selectivity

A tailor-made encapsulated catalyst with a H–β zeolite shell has been directly synthesized over Co/Al 2O 3 pellets to form a core–shell structure without pinholes and cracks by a hydrothermal synthesis method. Pretreatment of the Co/Al 2O 3 pellets with reflux of hot TEAOH solution can clean and corrode the pellet surface due to its strong basicity, and can enlarge the mean pore size of the pellets. Impregnation of the Co/Al 2O 3 pellets in EtOH is important to avoid the corrosion of the internal pores, to prevent the introduction of Co species into the zeolite coating, and to realize a pure and uniformed β-zeolite coating. For the catalytic reaction of direct isoparaffin synthesis from syngas, the molar ratio of C isoparaffin/C normal-paraffin of the products obtained from the encapsulated catalyst increased about 64% than that of the products obtained from physical-mixed components. This concept of encapsulated catalyst can be useful to carry out various consecutive or multiple-step catalytic processes, where multiple reactions occur on different active centers.

Direct synthesis of isoparaffin from synthesis gas under supercritical conditions

To produce isoparaffins from synthesis gas directly, modified Fischer–Tropsch (FT) synthesis was carried out under supercritical conditions using n-butane as a medium. One-step FT synthesis using a hybrid catalyst consisting of Co/SiO 2, HZSM-5 and Pd/SiO 2 was carried out. Introduction of supercritical-phase n-butane increased light isoparaffins significantly and suppressed the formation of the by-product, methane. Under supercritical-phase butane, hydrogenolysis and isomerization reactions were promoted. Due to the fact that the optimum temperatures for FT and HZSM-5 catalysts are different, 513 K and over 573 K, respectively, two-step FT synthesis was also carried out to optimize the reaction temperatures. The first-step reaction used Co/SiO 2 catalyst containing small amount of HZSM-5 for FT synthesis at 513 K, and the second-step reaction used a hybrid catalyst containing Pd/SiO 2 and zeolite for hydrogenolysis and isomerization of hydrocarbons at 573 K. Introduction of supercritical n-butane increased the isoparaffin selectivity, and decreased the methane selectivity significantly. The production of heavy hydrocarbons C 9+ was inhibited in both gas and supercritical phase. The isoparaffin selectivity in the gas phase decreased with time-on-stream, but very stable for the supercritical-phase reaction. Because water and heavy hydrocarbons were removed from active sites on zeolite and the zeolite acidity was promoted in the supercritical medium, the selectivity of isoparaffin was considered stable. Among zeolites added to the hybrid catalyst in the second-step reactor, HZSM-5 and H-beta zeolite were suitable for producing light isoparaffins. These results indicated that two-step FT synthesis under supercritical n-butane was superior for producing light isoparaffins from synthesis gas directly.

Novel Three-component Zeolite Capsule Catalyst for Direct Synthesis of Isoparaffin

One zeolite capsule catalyst with core(Co/Al2O3)/shell(H-beta membrane) structure was prepared and used for isoparaffin direct synthesis via FTS reaction. Based on this core/shell zeolite capsule catalyst, a novel palladium painted zeolite capsule catalyst with three-component core (Co/Al2O3)/shell (H-beta membrane)/paint (Pd) structure was designed. In the isoparaffin synthesis on this three-component zeolite capsule catalyst, the olefins effused from the zeolite capsule catalyst were in-situ hydrogenated effectively, mostly converted to isoparaffin.

Design of a zeolite capsule catalyst by controlling the support size for the direct synthesis of isoparaffin

Three kinds of H-ZSM-5 zeolite capsule catalysts were prepared on Co/SiO2 catalyst pellets of different sizes. Characterization of the catalysts indicated that a defect-free H-ZSM-5 membrane had been constructed successfully on the Co/SiO2 surface. The smaller Co/SiO2 pellets were favorable for zeolite capsule growth under the same synthesis conditions. Zeolite capsule catalysts, especially the catalysts with smaller pellet sizes, had a higher isoparaffin selectivity compared with conventional FTS Co/SiO2 catalyst and mixed catalyst of Co/SiO2 with H-ZSM-5 zeolite.

Preparation, characterization and reaction performance of H-ZSM-5/cobalt/silica capsule catalysts with different sizes for direct synthesis of isoparaffins

Abstract Three kinds of H-ZSM-5 zeolite capsule catalysts were prepared by a direct hydrothermal synthesis method, where directly synthesized H-ZSM-5 membrane was coated perfectly onto Co/SiO 2 catalyst pellets of different sizes. SEM, EDS and XRD were used to characterize the catalyst morphology and to identify the H-ZSM-5 structure of zeolite capsules. Surface acidity and pore property of these catalysts were tested by NH 3 -TPD and gas adsorption. The results showed that smaller Co/SiO 2 pellets with large external surfaces were favorable for zeolite capsule growth under the same synthesis conditions. The Fischer–Tropsch synthesis (FTS) reactions using the conventional FTS catalyst Co/SiO 2 or the physically mixed catalyst of Co/SiO 2 with H-ZSM-5, or the zeolite capsule catalysts were each conducted. The isoparaffins were selectively obtained on the capsule catalysts and the mixed catalyst. The capsule catalysts exhibited higher selectivity of isoparaffins than the mixed catalyst due to the space-confined effect and the shape-selective effect. Especially, capsule catalysts with smaller sizes showed higher CO conversion and higher isoparaffin selectivity. Changing the substrate pellet size could control the capsule catalysts’ structure and their activity as well as their selectivity.

Direct synthesis of iso-paraffins from syngas with slurry phase reaction

The direct synthesis of gasoline-range iso-paraffins from synthesis gas (CO + H 2, syngas) via modified Fischer–Tropsch (FT) reaction was investigated in the slurry phase reaction system, the contact state of hybrid catalyst components and the composition of hybrid catalyst were optimized in this reaction system. The results show that the FT reaction and the in situ hydroconversion of its products occurred over hybrid catalysts containing Co/SiO 2, very high selectivity of gasoline-range iso-paraffins could be achieved.

06/02530 Direct synthesis of isoparaffin by modified Fischer-Tropsch synthesis using hybrid catalyst of iron catalyst and zeoliteYonevama. Y. et al. Catalysis Today, 2005, 104, (1), 37–40

06/02530 Direct synthesis of isoparaffin by modified Fischer-Tropsch synthesis using hybrid catalyst of iron catalyst and zeoliteYonevama. Y. et al. Catalysis Today, 2005, 104, (1), 37–40

Formation of Isoparaffins through Pd/β Zeolite Application in Fischer−Tropsch Synthesis

The direct synthesis of isoparaffins from synthesis gas (H2/CO = 2) was carried out in a consecutive dual reactor system under the conditions of P = 1.0 MPa and W/F = 4.97 g·h·mol-1. In the upper reactor, Co/SiO2 was used for Fischer−Tropsch (FT) reaction. To primarily decompose the heavy FT hydrocarbons, zeolite β (4:1 weight ratio) was physically mixed with Co/SiO2. The Pd/β catalyst with a Pd loading of 0.5 wt % and different Si/Al ratios in zeolites β was loaded in the lower reactor for hydroconverting the products from the upper reactor. Irrespective of the Si/Al ratio of zeolite β, the results indicate that the final products showed a sharp carbon number distribution in the range of C4−C6 and very high selectivity to branched isomers of C4−C6 alkanes. An apparent change of selectivity to isoparaffins was observed with the variation of the Si/Al ratio in Pd/β catalyst. Moreover, the stability of the catalyst was also influenced by the Si/Al ratios. The effect of the Si/Al ratio on the selectivity of isomers at different times on stream was correlated with the acidity and crystallization of the β zeolite, which were characterized by ammonia TPD and XRD methods.

Direct synthesis of isoparaffin by modified Fischer–Tropsch synthesis using hybrid catalyst of iron catalyst and zeolite

New hybrid catalysts for Fischer–Tropsch synthesis (FTS) to selectively produce isoparaffins at one step were developed by using Fe FTS catalysts mixed with H-ZSM-5 zeolite. The FTS catalysts produced normal paraffins, and then the normal paraffins isomerized and hydrocracked to produce isoparaffins on the zeolite in situ. For preparing highly active hybrid catalysts to lower methane formation, FTS catalysts based on Fe were developed. Carbon monoxide was the most effective reducing gas for the Fe FTS catalysts and the hybrid catalysts. Before adding the zeolite, the FTS products contained normal paraffins from C1–C16. After adding the zeolite, heavy hydrocarbons disappeared, and light hydrocarbons contained isoparaffins from C1 to C10 were produced alternatively. These results indicated that the hybrid catalyst composed of the mixture of Fe FTS catalysts and ZSM-5 zeolite had high performance for producing isoparaffins via one-step reaction.

Iso-paraffins synthesis from modified Fischer–Tropsch reaction—Insights into Pd/beta and Pt/beta catalysts

The direct iso-paraffin synthesis from synthesis gas (CO + H 2, syngas) via Fischer–Tropsch (FT) route was investigated in a consecutive dual reactor system, in which FT reaction was carried out over Co/SiO 2 catalyst in the upper reactor and hydroconversion of the FT hydrocarbons occurred over Pt/beta or Pd/beta catalyst in the lower reactor. The products with very high iso-paraffin selectivity were composed mainly of hydrocarbons with carbon number less than 10, indicating that both hydrocracking and hydroisomerization reactions significantly occurred. Under the present operating conditions, time-on-steam results indicate that Pt/beta catalyst containing 0.5 wt.% Pt deactivated quickly while 0.5 wt.% Pd/beta catalyst showed stable performance in the case of iso-paraffin selectivity. Either the increase in Pt loading to 1 wt.% Pt or the increase of hydrogen partial pressure in the lower reactor can alleviate the deactivation of the catalyst for the titled reaction. This was mainly ascribed to the different effect of the adsorbed CO molecule on the metallic function of Pt and Pd.

Selective Synthesis of Middle Isoparaffins via a Two-Stage Fischer−Tropsch Reaction: Activity Investigation for a Hybrid Catalyst

The activity of hybrid catalysts for the direct isoparaffin synthesis, especially C4−C6 with a very high octane number, from Fischer−Tropsch synthesis (FTS) in a two-stage reactor was investigated. The hybrid of Co/SiO2 and H-ZSM-5 was used as the first-stage reaction catalyst, and different types of H zeolites alone or their hybrid with Pd/SiO2 were used as the second-stage reaction catalysts. The obtained results demonstrated that the carbon number of products could terminate at 6 and isoparaffin hydrocarbons could be synthesized in very high selectivity from synthesis gas compared with that in a single-stage reaction using a physically mixed Co/SiO2 and H-ZSM-5 catalyst. The first-stage Co/SiO2 + H-ZSM-5 catalyst made the products mainly distribute in the C1−C11 range and considerably increase in the corresponding isoparaffins because of successive cracking, as well as isomerization, of the primary FTS products on H-ZSM-5. The selectivities of isoparaffins with much lower carbon number were further rai...

Effects of type of contact between Co/SiO2and Pd/b on the direct synthesis of isoparaffins from synthesis gas

The effect of addition of Pd/b on the Co/SiO2 catalyst was studied for F-T reaction. Pd/b could enhance the formation of C4-C9 isoparaffins while the Co/SiO2 catalyst alone gave the products with wide carbon numbers distribution. The reason is the olefins and long-chain normal paraffins from F-T reaction on Co/SiO2 catalyst form light hydrocarbons containing isoparaffins through the hydrocracking and hydroisomerization on Pd/b. For Co/SiO2+Pd/b catalyst, the selectivity to isoparaffins depends on the contact conditions. The granular hybrid catalyst is much more selective for isomerization than the powder hybrid catalyst, while the selectivity to CH4, n-paraffins and olefins is lower than that on the powder hybrid catalyst.

Three-component hybrid catalyst for direct synthesis of isoparaffin via modified Fischer–Tropsch synthesis

Direct isoparaffin synthesis method from syngas was developed by using a hybrid catalyst composed of Fischer–Tropsch synthesis catalyst, ZSM-5 zeolite, and Pd/SiO 2, where normal paraffin from Fischer–Tropsch synthesis was hydrocracked in situ on ZSM-5 and Pd/SiO 2 stabilized zeolite activity effectively even at pressurized steam atmosphere mainly via spillover effect.

Hybrid Catalyst for Direct Synthesis of Isoparaffin through Modified Fischer-Tropsch Synthesis.

Direct isoparaffin synthesis method from syngas was developed by using a hybrid catalyst composed of Fischer-Tropsch synthesis catalyst and ZSM-5 zeolite. Normal paraffin were synthesized on Fischer-Tropsch synthesis catalyst and consecutively hydrocracked on the coexisting zeolite, to form lighter branched hydrocarbon in the same reactor A third component, Pd/SiO2, was added to the hybrid catalyst and it stabilized the catalyst system effectively. It seems that Pd/SiO2 initiated spillover effect to stabilize zeolite activity even if water existed.