Light Aromatics Research Articles

Selective CO2 Hydrogenation to Light Aromatics over the Cu-Modified Fe-Based/ZSM-5 Catalyst System

Selective CO₂ Hydrogenation to Light Aromatics over the Cu-Modified Fe-Based/ZSM-5 Catalyst System

Study on acid-base coupled catalytic pyrolysis of heavy crude oil to light olefins and aromatics by Py-GC/MS and fixed bed reactor

Direct catalytic cracking of heavy crude oil has gained attention as an alternative and cheapest method of producing raw materials for the petrochemical industry. The Py-GC/MS technique was used to study the effects of calcium aluminate base catalysts and ZSM-5 acid zeolites on heavy crude oil conversion. The results showed that ZSM-5 with a Si/Al ratio of 40 (40Z) outperformed zeolites with Si/Al ratios of 80 and 200, with a maximum selectivity of 65% for light olefins and BTX (benzene, toluene and xylene). Among all base catalysts studied, calcium aluminate (CaAl-3) had the highest selectivity of 23% of C2-C4 olefins and BTX. The “Mix” model outperformed the “Base + Acid” or “Acid + Base” models in terms of minimizing hydrogen transfer reactions and maximizing the yield and selectivity of light olefins. The 30 C catalyst (30%CaAl-3 +70%40Z) exhibited significant co-effect of basic and acidic catalysis, with maximum light olefin selectivity and total olefinicity of 72% and 81%, respectively. The results of the present work showed that acid-base coupled catalytic pyrolysis was a viable approach for improving the yield of light olefins and aromatics.

Influence of Mg and Co addition on Fe based catalyst for in-situ biomass pyrolysis

In this work, the effect of Mg and Co on Fe based catalyst for biomass in-situ pyrolysis was investigated in a fixed-bed reactor. The yields of hydrogen and light aromatics could be improved with Fe-Mg/Co catalyst. The maximum H2 yield of 113.48 mL/g was obtained with the 15Fe0.8Mg catalyst at 700 ℃. Fe-Mg/Co not only promoted cracking and restructuring of bio-oil but also enhanced the thermal decomposition of the heavier bio-oil at the higher temperature, which resulted in the improvement of BTX (benzene, toluene, xylene), PCN (phenol, cresol, naphthalene) yields. The best conditions for the formation of BTX, PC and naphthalene are 15Fe0.8Mg0.7Co at 700 ℃. The surface characteristics of Fe-Mg/Co catalyst were analyzed with TEM, XRD and H2-TPR, SEM, Raman, FT-IR, XPS. TEM result showed that the size of particle changed from 16.23 to 6.73 and 6.43 nm by adding the Mg and Mg-Co, respectively. Meanwhile, XRD and XPS results indicated that Fe2O3 was transformed into Fe. Comparing the spherical particles in the SEM, change in particle size can be clearly observed, 15Fe> 15Fe0.8Mg> 15Fe0.8Mg0.7Co. Mg and Co promoted Fe catalyst activity to form highly active sites and then further promoted the steam reforming reaction.

Production of light aromatics from biomass components co-pyrolyzed with polyethylene via non-thermal plasma synergistic upgrading

Catalytic co-pyrolysis of cellulose, xylan and lignin with polyethylene (PE) was conducted using a tandem vacuum pyrolysis and non-thermal plasma (NTP) synergistic upgrading system. HZSM-5, Ti and Ni modified HZSM-5 were employed. Cellulose-derived furfural was difficult to be converted, and increased PE ratio generated more olefins and promoted furfural deoxygenation. Ti-modification raised MAHs from 12.23% to 42.55% while Ni-modification further increased MAHs to 44.36%. However, Ti-modification raised the catalytic coke from 0.12% to 3.20% while Ni-modification mainly increased thermal coke from 1.69% to 4.63%. Xylan co-pyrolyzed with more PE promoted the production of olefins due to reverse Diels-Alder reaction. Ti-modification slightly improved MAHs from 17.09% to 22.58%, while Ni-modification remarkably increased MAHs to 40.90%. Correspondingly, Ti-modification slightly increased light and thermal cokes, while Ni-modification raised all types and total coke content increased from 5.50% to 10.97%. Lignin obtained the lowest oil yield of 15.02% with the maximum MAHs of 84.34%, and co-pyrolysis with PE improved the deoxygenation. Ti-modification increased petroleum-like alkanes with the reduction of MAHs and olefins while Ni-modification increased MAHs from 59.22% to 71.93%. However, the lower oxygen content and more aliphatic branches contributed to the higher ratio of aliphatic hydrogen, and catalysts were coked seriously.

Crude oil conversion to chemicals over green synthesized ZSM-5 zeolite

The study reports the conversion of crude oil to basic chemicals over a template-free green synthesis of ZSM-5(40) zeolite using halloysite (HAL) and bolus alpha (BA) as silica and alumina precursors. The Z(40)HAL and Z(40)BA exhibited hierarchical pores with high surface area of 248 m2/g and 257 m2/g, respectively. The addition of soft template during the synthesis of Z(40)BA forms a Z(40)BAT zeolite with lower surface area. The synthesized zeolites were impregnated with 2wt%Mn and tested for the steam catalytic cracking of crude oil to light olefins and aromatics catalysts at 675 °C in a fixed-bed reactor. Maximum light olefins (C2=-C4=) yield (47 wt%) and total aromatics (14.7 wt%) were attained over 2Mn/Z(40)HAL catalyst. The conversion of crude oil (68.4%) is attributed to hierarchical pores and the presence of large weak and strong acid sites in the 2Mn/Z(40)HAL zeolite. Moreover, due to the high reaction temperature, some effects of thermal cracking such as protolytic cracking reactions with high ethylene yield (22%) were introduced. The addition of 1% phosphorus and 1%Mn to Z(40)HAL resulted in lower catalytic cracking activity. Similarly, the 2Mn/Z(40)BAT performed slightly lower than the template-free 2Mn/Z(40)BA additive. The experimental results demonstrate the technical feasibility of template-free green synthesis of ZSM-5 zeolite in the conversion of crude oil to basic chemicals.

Enhancement of the production of bio-aromatics from bamboo pyrolysis: Wet torrefaction pretreatment coupled with catalytic fast pyrolysis

Light aromatics are important organic building blocks in the chemical industry which can be produced by catalytic fast pyrolysis (CFP) of biomass. In this work, wet torrefaction pretreatment (WTP) was employed to improve the quality of bamboo by synergistic effect of deoxygenation and demineralization. Then, CFP was employed to produce bio-aromatics by using zeolite (e.g. HZSM-5, HY, Al-MCM-41, and USY) as catalyst. Results showed that WTP temperature (180–260 °C) had more significant influence on the mass yields of torrefied products compared to WTP duration (30–150 min). The maximum deoxygenation rate was 49.36% at WTP conditions of 260 °C and 150 min, and the maximum demineralization rate followed the order of 96.29% (K) > 94.54% (Na) > 90.33% (Mg) > 89.22% (Ca). Among the five types of zeolite catalyst tested, HZSM-5 (25) was the best catalyst to obtain bio-aromatics due to its unique pore size and reasonable acidity. The maximum yield of aromatics (25.46 ×107 a.u./mg) was obtained at the WTP temperature of 220 °C, biomass-to-catalyst ratio of 3:1, and CFP temperature of 850 °C. Toluene was the more favored monocyclic aromatic hydrocarbon formed during CFP compared to xylene and benzene.

Comparison of hydrocracking and cracking of pyrolytic lignin over different Ni-based catalysts for light aromatics production

This work compared hydrocracking and cracking of pyrolytic lignin (PL) for light (single-ring and double-ring) aromatics production over Ni-based catalysts. Due to the supports' original acidities and the interactions between metal and supports, these Ni-based catalysts had different amounts of available Ni and acid sites, which affected depolymerization and deoxygenation in both cracking and hydrocracking. During cracking, the PL depolymerization could be promoted by increasing Ni and acid sites but this promotion was limited by the hydrogen inside PL, whereas both Ni and acid sites exhibited poor performance in deoxygenation. The cooperation of Ni and acid sites achieved efficient hydrodepolymerization and hydrodeoxygenation in hydrocracking. Acid sites benefitted the cracking of linkages in PL and the resulting intermediates could be converted into monophenols through Ni-catalyzed hydrogenation. In the selective hydrodeoxygenation mechanism of monophenols to monoaromatic hydrocarbons, acid sites facilitated the initial tautomerization and the final dehydration reactions, while the middle hydrogenation step was catalyzed by Ni. Additionally the micropore structure of catalyst also favored the generation of light aromatics. Therefore, hydrocracking over Ni/HZSM-5 with sufficient available Ni and acid sites and the micropore structure, realized the most effective conversion of PL to light aromatics, especially aromatic hydrocarbons.

Catalytic pyrolysis behavior of heavy crude oil over acid-base composite catalysts

Direct pyrolysis of crude oil to petrochemical feedstocks (light olefins and aromatics) is a trend for the transformation of refineries. In order to combine the advantages of solid base and acid catalysts to boost the yields of light olefins and BTX (benzene, toluene and xylene), catalytic pyrolysis behavior of heavy crude oil over acid, base and composite catalysts were studied using Py-GC/MS. The results showed that maximum content of alkenes was obtained over the calcium aluminate (CaAl) catalyst due to the inhibited hydrogen transfer reactions, but its catalytic activity was lower than ZSM-5 with Si/Al ratio of 40 (Z-40). For different composite catalyst ratios, maximum light olefins and BTX content of 65 % was obtained with 40Z catalyst (60 %CaAl + 40 %Z-40), which was higher than that obtained with pure Z-40 and CaAl catalysts. Compared to commercial ZSM-5 based and USY based catalysts, the 40Z catalyst demonstrated superior catalytic cracking performance, with the highest content of light olefins and BTX, while significantly higher content of C9+ aromatics were obtained over FCC catalyst. This revealed that catalyst type and appropriate composite catalyst blend ratio all play important role in enhancing the generation of light olefins and aromatics.

Enhancing high selectivity production of light aromatics from in-situ catalytic upgrading of cellulose pyrolysis vapors by regulating hierarchical core-shell ZSM-5@MCM-41

The catalytic upgrading of cellulose pyrolysis vapors is one of the effective methods to realize its high value utilization. Tuning the pore structure and acid sites of ZSM-5 (Z5) is a necessary strategy to develop effective catalysts for the production of light aromatics and the inhibition of carbon formation. In this study, a core-shell structure ZSM-5 @MCM-41 was developed and used for the first time in catalytic fast pyrolysis (CFP) of cellulose to prepare light aromatic hydrocarbons. The successful synthesis of the hierarchical core-shell ZSM-5 @MCM-41 was confirmed by nitrogen physisorption, X-ray diffraction (XRD), and transmission electron microscope (TEM) analysis. In aromatic hydrocarbon production, 1.0SH-Z5 @ M41 (1.0 mol/L, ZSM-5 @MCM-41) has the highest relative content of 98.76%. The relative content of BTEX (benzene, toluene, ethylbenzene, and xylene) is up to 89.83%, which is 2.39 times that of traditional microporous Z5. The quadratic polynomials were developed to correlate the Brønsted-to-Lewis acid site strength ratio (BLR) and mesopore-to-micropore volume ratio (MMR) with the relative content of BTEX. The mechanism of in-situ catalytic upgrading of cellulose pyrolysis vapor over ZSM-5 @MCM-41 was revealed. Due to high selectivities and low coke formation, ZSM-5 @MCM-41 offers an improved option for making monocyclic aromatics from cellulosic biomass.

Production of light olefins and aromatics via catalytic co-pyrolysis of biomass and plastic

Co-pyrolysis of pine and LDPE over basic catalysts (calcium oxide, calcium aluminate, and calcium ferrite), acidic catalysts (ZSM-5 with Si/Al ratios of 40, 80 and 200, commercial FCC and ZSM-5 based catalysts), and acid-base tandem catalysts were investigated by TG-FTIR and Py-GC/MS to improve light olefins and aromatics production. Research found that co-pyrolysis of pine and LDPE showed a positive synergistic effect and the addition of catalyst could reduce the average apparent activation energy of co-pyrolysis significantly. The optimal base and acid catalysts are calcium aluminate (CaAl) and ZSM-5 with Si/Al ratios of 40 (Z40), respectively. The highest content of light olefins and BTX (69.45 %) can be obtained over base-acid (CaAl-Z40) tandem catalyst at 600 °C, with CaAl to Z40 ratio of 1:1. This work will serve as a relevant reference for production of light olefins and BTX from the catalytic co-pyrolysis of biomass and plastics over base-acid tandem catalysts.

ZSM-12 nanocrystals with tunable acidity directed by rigid diquats: Synthesis and catalytic applications

ZSM-12 is an important zeolite used as a catalyst in several industrial hydrocarbon conversion reactions. Facile synthesis of nanocrystalline ZSM-12 in a wide Si/Al compositional range remains a challenge. Here we report the successful synthesis of nanosized ZSM-12 from flexible aluminosilicate initial gels (Si/Al = 20, 50 and 100) using rigid diquaternary ammonium compounds (p-xylene-bridged bis-methylpyrrolidinium, -methylpiperidinium and −1,2-dimethylimidazolium -) as the organic structure-directing agents (OSDAs). The effective structure-directing ability of these OSDAs for nanocrystalline ZSM-12 synthesis is due to the strong interaction between the OSDA and the growing zeolite framework. The resulting nanocrystalline ZSM-12 zeolites with proper acidity exhibit substantially improved catalytic performance in hydroconversion of n-hexadecane (n-C16) and methanol-to-hydrocarbons reactions. TGA analysis of used catalysts and in situ IR spectroscopy of intra-zeolite organic species during the MTH reaction revealed that the smaller crystals result in lighter aromatics and less coke deposition due to the higher rate of desorption attributed to the larger external surface area.

Waste tyres valorisation through gasification in a bubbling fluidised bed: An exhaustive gas composition analysis

Waste tyres gasification in a bubbling fluidised bed reactor is evaluated by means of a complete characterisation of the product gas. The experiments are carried out at two temperatures, 700 and 850 °C, and various equivalence ratios (ER) while using air as a gasifying. Additionally, the effect of steam is also studied at 850 °C. High temperature and low ER increase the production of H2, CH4, and C2H4. Steam addition mainly affects H2 and CO production. Low carbon conversion (CC) into gas and cold gas efficiency (CGE) are obtained, increasing with temperature and ER. The lower heating value (LHV) of the gas decreases with the ER because of the higher partial combustion rates. LHV values range between 12 MJ/Nm3 with steam addition at ER = 0.13 and 850 °C to 5.3 MJ/Nm3 at ER = 0.33 and 700 °C using air only. Along with a major permanent gas (CO2, CO, H2, CH4, and C2Hn), up to 25 short-chain hydrocarbons (non-aromatic hydrocarbons ranging from C3 to C6+) and two light aromatics are present in the product gas. Among short-chain hydrocarbons, C3 and C4 compounds are present in the highest yields. All these minor hydrocarbon species (i.e., C3 to C6+), not usually reported in biomass or waste gasification studies, yield up to 13 %vol. on a N2-free basis. Their contribution to the gasification performance is important because they account for half of the energy content in the product gas. Therefore, it is important to consider them in the gasification process, not only for energy purposes but also for the chemical industry.

A review of catalytic hydrogenation of carbon dioxide: From waste to hydrocarbons.

With the rapid development of industrial society and humankind’s prosperity, the growing demands of global energy, mainly based on the combustion of hydrocarbon fossil fuels, has become one of the most severe challenges all over the world. It is estimated that fossil fuel consumption continues to grow with an annual increase rate of 1.3%, which has seriously affected the natural environment through the emission of greenhouse gases, most notably carbon dioxide (CO2). Given these recognized environmental concerns, it is imperative to develop clean technologies for converting captured CO2 to high-valued chemicals, one of which is value-added hydrocarbons. In this article, environmental effects due to CO2 emission are discussed and various routes for CO2 hydrogenation to hydrocarbons including light olefins, fuel oils (gasoline and jet fuel), and aromatics are comprehensively elaborated. Our emphasis is on catalyst development. In addition, we present an outlook that summarizes the research challenges and opportunities associated with the hydrogenation of CO2 to hydrocarbon products.

Direct discerning reaction pathways in methanol-to-hydrocarbons by transient operation – FASPA

Monitoring complex catalytic pathways under industrially-relevant conditions is one of the key challenges in catalysis chemistry and technology. Herewith we describe a direct technique called ‘fast scanning-pulse analysis’ (FASPA) that allows the direct characterization and detailed kinetic analysis of intimately interweaved catalytic pathways. The power and potential of the FASPA approach are demonstrated with an industrially relevant methanol-to-hydrocarbons (MTH) process over H-ZSM-5 zeolite. This reaction proceeds via a hydrocarbon pool (HCP) mechanism producing olefins and aromatics. The HCP is built-up upon exposure to methanol during the induction period, followed by a transition regime to a quasi steady-state MTH operation. This FASPA technique allows (sub-)second resolution of the full temporal products response upon a methanol pulse providing direct and quantitative insights into the MTH reactions. Globally, two consecutive pathways can be discerned: a very fast primary product formation in the presence of methanol in a narrow active MTH reaction zone, followed by a slower formation of light aromatics, which is closely related to the decomposition and release of HCP species and secondary reactions in absence of methanol in the downstream part of the catalyst bed. The time delay between the appearance of inert tracer and primary products represents the time needed to build-up the HCP in the induction period, where methane is observed prior to other products. The primary products (alkanes, olefins, and light aromatics) are nearly instantaneously formed from the pulsed methanol. These results demonstrate the highly dynamic character of the HCP in the MTH process over H-ZSM-5.

Mechanism of catalytic conversion of kerosene co-refining heavy oil to BTEXN by Py-GC/MS based on “point-line-surface-body” step by step research strategy

Kerosene co-refining heavy oil (KCR-H), KCR-H six group components (KCR-HS), six typical model compounds representing the KCR-HS and its mixed model compound were selected as raw materials. The effects of the physicochemical properties of single and bi-metallic modified HZSM-5 (Me/Z-5) on the selectivity and yield of benzene (B), toluene (T), ethylbenzene (E), xylene (X), naphthalene (N) in cracking products were investigated by pyrolysis–gas chromatograph/mass spectrometer (Py-GC/MS). The results show that Ni-Mo/Z-5 exhibits superior selectivity for light aromatic in the catalytic conversion of tetradecane, benzofuran, and KCR-H, compared with Z-5. Additionally, oxygenated and aliphatic compounds are more easily converted to light aromatics than PAHs and nitrogen-containing compounds. Using Ni-Mo/Z-5 catalytic conversion benzofuran, the selectivity of BTEXN in the cracking product is 65.01 %, which is 23.44 times higher than pyrene (2.66 %). Due to the preferential cracking of benzofuran, small molecular fragments prepared by tetradecane and methyl naphthalene promote the catalytic conversion of methyl phenol, quinoline, and pyrene. Compared with the theoretical BTEXN yield (1338.39 mg/kg), the experimental BTEXN yield obtained from mixed model compounds (MCs) increasing by 37.95 %, which is 1846.40 mg/kg. In addition, the BTEXN selectivity of saturates (Satur) over Ni-Mo/Z-5 is 62.97 %, increases by 12.97 % compared with tetradecane, which represents the components of this group, indicating that the synergistic effect between oxygenated compounds and aliphatic compounds is conducive to produce light aromatics. Furthermore, based on the structural characteristics and catalytic properties of metalmodified Z-5 and the conformational relationships between points, lines, surfaces, and bodies, possible catalytic conversion mechanisms and pathways for KCR-H and KCR-HS were proposed.

Direct conversion of carbon dioxide to liquid hydrocarbons over K-modified CoFeOx/zeolite multifunctional catalysts

Direct conversion of carbon dioxide (CO2) to high added-value chemicals is available for reducing reliance on fossil fuels and mitigating CO2 emissions, but both the chemical inertness of CO2 and the difficulty of carbon chain growth make it difficult to enhance the activity of the catalyst. In this work, we developed a multifunctional catalyst composed of K-promoted spinel structured CoFeOx and HZSM-5 that efficiently converted CO2 to light-weight hydrocarbons via CO2 modified Fischer-Tropsch synthesis path (CO2-FTS), and the best catalyst exhibited a remarkably efficient CO2 conversion of 51.2% and liquid hydrocarbons space-time yield (STY) of 3.4 μmolC5+·gcat−1·s−1 along with an extremely low selectivity of 5.5% toward undesired CO. By analysis of structural characterizations and reaction results, the noticeable performance of the multifunctional catalyst critically lies in the beneficial interaction between Co and Fe, the promoting effect of potassium, and the concertedly synergistic effect between K-CoFeOx and HZSM-5. In situ XRD, XPS, and TPD characterizations further indicate that the introduction of cobalt promotes the reduction of iron by forming a Fe0-rich FeCo alloy, which is beneficial for the adsorption of intermediate CO and facilitates the in situ generation of active iron carbide. K as an electronic promoter is added to increase the surface basicity, enhance the adsorption of CO2 and weaken the adsorption of H2, which favor CO2 conversion and carbon chain growth. Additionally, through passivation of the strong acidic site of HZSM-5 by Si treatment and varying the mixing mode of HZSM-5 and nK-CoFeOx, the synergistic effect of the two components promotes CO2 conversion and noteworthily increases the distribution of light-weight hydrocarbons, especially benzene, toluene, and xylene on composite catalyst by aromatization over active sites with appropriate acidity and proximity. This study provides valuable guidelines for designing selective and efficient iron-based composite catalysts to obtain value-added FTS products and light aromatics.

Selective Production of Light Aromatics from Hydrocracking of Pyrolytic Lignin over Ni/HZSM-5

Pyrolytic lignin (PL), namely the water-insoluble fraction of bio-oil, is mainly composed of phenolic oligomers, and therefore, it has the potential to be converted into light hydrocarbons and phenols. This work studied the hydrocracking of PL for the generation of light aromatics (including monoaromatic hydrocarbons, double-ring aromatic hydrocarbons, and monophenols). By comparing different PL conversions, the reaction mechanism of PL hydrocracking over Ni/HZSM-5 was proposed, and particularly, the synergistic catalytic effects of Ni and acid sites on hydrodepolymerizatrion and hydrodeoxygenation were explained. Then, the effects of Ni loading on Ni/HZSM-5, reaction temperature, and reaction pressure were investigated and discussed based on the proposed reaction mechanism. It was found that a good balance of Ni and acid sites under the Ni loading of 10% could achieve the best synergistic effect for hydrodepolymerization and hydrodeoxygenation. A suitable reaction temperature of 500 °C achieved the efficient hydrodepolymerization and hydrodeoxygenation, while the removal of alkyl side groups attached to the benzene ring was not intense. Continuously increasing the reaction pressure to 4 MPa also facilitated the hydrodepolymerization of PL as well as the hydrodeoxygenation of the monophenols. Under the optimum reaction parameters, the yields of monoaromatic hydrocarbons, double-ring aromatic hydrocarbons, and monophenols reached 16.61%, 7.81%, and 9.36%, respectively. The spent catalyst was deactivated because of the carbonaceous deposits on it, and it could be well regenerated by burning these carbonaceous deposits.

Study of waste rubber catalytic pyrolysis in a rotary kiln reactor with spent fluid-catalytic-cracking catalysts

The low utilization rate of waste rubber has caused serious environmental pollution problems. Catalytic pyrolysis is an effective method for ensuring the resource utilization of waste rubber. However, the high cost and nonrecyclability of the used catalysts complicate the utilization of this method in industrial applications. In this paper, the spent fluid-catalytic-cracking (FCC) catalysts were applied into pyrolysis of waste rubber, aiming to reduce the cost of catalytic pyrolysis of waste rubber. At the same time, the pyrolysis mechanisms of the spent FCC catalysts used in waste rubber were studied. Pyrolysis/catalytic pyrolysis experiments on single-rubber-type unvulcanized rubber, single-rubber-type vulcanized rubber, and tread compounds were performed in a self-developed industrial pilot plant. The experimental results showed that the pyrolysis oil yield of the spent FCC catalysts catalyzed pyrolysis of the waste rubber increased and the content of light aromatics in increased by more than 90 %, indicating that the spent FCC catalysts applied in waste rubber can improve the quality of pyrolysis products, increase production efficiency, and realize the collaborative high-value reuse of waste rubberand spent FCC catalysts.

Valorisation of cotton stalk toward bio-aromatics: Effect of wet torrefaction deoxygenation and deminerization pretreatment on catalytic fast pyrolysis using Ga modified hierarchical zeolite

Wet torrefaction pretreatment (WTP) can upgrade the property of biomass by synergistic effect of deoxygenation and deminerization (e.g. K, Ca, Na, Mg). In this work, valorisation of cotton stalk (CS) was performed by using combined approaches of WTP and catalytic fast pyrolysis (CFP) to produce bio-aromatics. First, the maximum deoxygenation and deminerization rates were 53.84 % and over 90 %, respectively, at the WTP temperature of 260 °C. Second, the bifunctional catalyst of Ga modified hierarchical HZSM-5 with micro-mesopore structure allowed more oxygenates diffusing into the channel of catalyst and increased the reaction rates of deoxygenation and aromatization reactions which highly improved the yield of bio-aromatics. Third, higher CFP temperature was favored for the formation of aromatics. The yield of aromatics increased first with the raise of catalyst-to-biomass (C/B) ratio from 1:1 to 1:3, then decreased slightly at the highest C/B of 1:5. At last, the operation parameter of WTP and SS-CFP was optimized which the maximum yield of light aromatics was 1.08 × 108 a.u./mg at WTP temperature of 220 °C, biomass-to-catalyst ratio of 3:1, and CFP temperature of 850 °C.

Dynamic confinement of SAPO-17 cages on the selectivity control of syngas conversion.

The OXZEO (oxide−zeolite) bifunctional catalyst concept has enabled selective syngas conversion to a series of value-added chemicals and fuels such as light olefins, aromatics and gasoline. Herein we report for the first time a dynamic confinement of SAPO-17 cages on the selectivity control of syngas conversion observed during an induction period. Structured illumination microscopy, intelligent gravimetric analysis, UV-Raman, X-ray diffraction, thermogravimetry and gas chromatography-mass spectrometer analysis indicate that this is attributed to the evolution of carbonaceous species as the reaction proceeds, which gradually reduces the effective space inside the cage. Consequently, the diffusion of molecules is hindered and the hindering is much more prominent for larger molecules such as C4+. As a result, the selectivity of ethylene is enhanced whereas that of C4+ is suppressed. Beyond the induction period, the product selectivity levels off. For instance, ethylene selectivity levels off at 44% and propylene selectivity at 31%, as well as CO conversion at 27%. The findings here bring a new fundamental understanding that will guide further development of selective catalysts for olefin synthesis based on the OXZEO concept.