Fixed-bed Flow Reactor Research Articles

Dehydrogenation of dodecahydro-N-ethylcarbazole over spinel supporting catalyst in a continuous flow fixed bed reactor

Dodecahydro-N-ethylcarbazole (12H-NECZ) is considered as one of the most promising liquid organic hydrogen carriers (LOHCs) in terms of hydrogen storage and delivery. Developing dehydrogenation catalysts with high efficiency is of significance for its application on a large scale. Herein, we reported a work on the dehydrogenation of 12H-NECZ over supported spinel catalysts in a continuous flow fixed bed reactor. The influence of active metal of Pt, Pd and Ru was firstly investigated. Then four kinds of spinel (MgAl2O4, NiAl2O4, CoAl2O4 and ZnAl2O4) supporting Pd catalysts were well studied. Pd/MgAl2O4 showed the best performance with a conversion of 98.3% at 180 °C. The characterizations of catalysts evidenced that the good performance was attributed to the strong interaction between Pd and MgAl2O4, which resulted in the smaller Pd particles and more positively charged Pd species. These Pd species were believed to be beneficial for dehydrogenation via weakening the adsorbed strength between Pd and dehydrogenated products. This work provides theoretical guidance for the design of efficient dehydrogenation catalysts.

Sorption-enhanced steam methane reforming over Ni/Al2O3/KNaTiO3 bifunctional material

The performance of a new lab-made bifunctional material Ni/Al2O3/KNaTiO3 for producing high purity H2 via sorption-enhanced steam methane reforming (SESMR) was investigated. A series of bifunctional materials with 10 wt% Ni loading but different wt% ratios of KNaTiO3 and Al2O3 was prepared by wetness impregnation method. All the materials were calcined at 700 °C for 3 hours and screened for their catalytic activity in a continuous flow fixed-bed reactor. The material containing 50 wt% each of KNaTiO3 and Al2O3 (designated as HM) was found to be the best choice. The optimum process parameters for the production of high purity H2 were determined: temperature = 700 °C, steam to carbon (S/C) molar ratio = 6 and gas-hourly space velocity (GHSV) = 2000 cm3 g-1 h-1. The values of CH4 conversion, H2 yield and H2 purity were 87, 87 and 90%, respectively, at the optimum reaction conditions. The adsorption capacity of HM was found to be 14.7 wt%. With a breakthrough time of 10 min, the material was stable for 8 adsorption-desorption cycles. The regeneration of HM was achieved with N2 gas at the same reaction temperature. Overall, the activity of this material for SESMR was very promising.

Role of Cr on Cu-Cr catalyst via direct ethanol dehydrogenation to ethyl acetate

This study aims to convert ethanol to ethyl acetate and acetaldehyde using the catalytic ethanol dehydrogenation. The Cu-Cr catalysts were prepared via co-precipitation method using chromium (III) nitrate and copper nitrate precursors having different CuO weights between 50 and 80 wt% balancing with Cr2O3. The fresh catalyst was reduced by mixed gas of H2:N2 (10:90%) at 250ºC for 1 and 2 h (the non-reduced sample was also tested for comparative results). The structural properties of Cu-Cr catalysts were investigated by N2 physisorption, XRD, SEM-EDX, H2-TPR, XPS, NH3-TPD, and CO2-TPD. The ethanol dehydrogenation was carried out in a borosilicate glass fixed-bed continuous flow reactor at the specific condition [300 °C, atmospheric pressure, and WHSV = 3 (gethanol gcatalyst−1) h−1]. Based on the results, the ethyl acetate selectivity on 50 Cu-Cr catalyst (Low atomic Cu/Cr ratio) apparently increased by 1.6 times with increasing reduction time to 2 h having the highest ethyl acetate selectivity. Interestingly, the results from ethanol dehydrogenation indicated that the chromium promoter combining with CuxO in the 50 Cu-Cr catalyst increased the dispersion of copper species, facilitated the reduction, and increased the amount of Lewis acid sites. Moreover, the suitable reduction times can alter the distribution of CuCr2O4, Cu+, and Cu0, which resulted in increased ethyl acetate selectivity. The 50 Cu-Cr catalyst also exhibited good stability.

Integration of zeolite@metal–organic framework: a composite catalyst for isopropyl alcohol conversion to aromatics

In this study, a Zn-based metal-organic framework (MOF)-zeolite composite ZSM-5@IRMOF-1 was synthesized for the alternative production of BTX from isopropyl alcohol (IPA). Incorporation ensured the capacity to tune the Lewis acidity at a framework level and design accessible pore structures, making composites highly attractive to be used as catalysts. The combination of monodispersed HZSM-5 zeolites on and within acidic IRMOF-1 provided the highly selective production of lower aromatics from IPA. The interaction of IPA with catalysts was investigated at different temperatures in a fixed-bed continuous flow reactor. The obtained product was analyzed using a standard test method ASTM D6730 through gas chromatography-detail hydrocarbon analyser. The results indicated that the reaction between IPA and MOF-supported zeolite occurred without substantial participation of MOFs. The maximum aromatic (BTEX) selectivity of 38.2% was achieved among all hydrocarbons at 92.3% carbon conversion. In addition, the gas yield was <20% for this catalyst system. The appropriate density of Brønsted and Lewis acidic sites and hierarchical pore structures provided the composite catalyst with outstanding aromatic selectivity yield and high stability.

Synthesis and Characterization of Ag/Al2O3 Catalysts for the Hydrogenation of 1-Octyne and the Preferential Hydrogenation of 1-Octyne vs 1-Octene.

Catalysts featuring 2, 5, and 10 wt % silver supported on alumina were prepared by the deposition precipitation method and activated under hydrogen. All catalysts were characterized by Brunauer–Emmett–Teller (BET) measurements, inductively coupled plasma-optical emission spectrometry (ICP-OES), backscattered electron scanning electron microscopy (BSE-SEM), high-resolution transmission electron microscopy (HR-TEM), hydrogen-temperature-programmed reduction (H2-TPR), H2-chemisorption, thermogravimetric analysis (TGA), infrared (IR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and isopropylamine (IPA) TPD and evaluated in a continuous plug flow fixed-bed reactor. Metal nanoparticles with average sizes of 4.5, 11.5, and 21.1 nm were identified by HR-TEM for the 2, 5, and 10 wt % Ag/Al2O3 catalysts, respectively. A conversion of 99% was observed for 1-octyne over particles between 10 and 15 nm in size, with stable operation up to 24 h (decreasing thereafter) at a temperature of 140 °C and a pressure of 30 bar in the competitive hydrogenation reaction. No conversion of 1-octene was noted in competitive reactions (mixed 1-octyne and 1-octene feed) but rather a gain of 1-octene throughout the 72 h time-on-stream. The performance of all catalysts was influenced by both the metal and support, where the latter impacted the overall acidity of the catalysts, thus affecting their long-term stability.

Immobilization-Stabilization of β-Glucosidase for Implementation of Intensified Hydrolysis of Cellobiose in Continuous Flow Reactors

Cellulose saccharification to glucose is an operation of paramount importance in the bioenergy sector and the chemical and food industries, while glucose is a critical platform chemical in the integrated biorefinery. Among the cellulose degrading enzymes, β-glucosidases are responsible for cellobiose hydrolysis, the final step in cellulose saccharification, which is usually the critical bottleneck for the whole cellulose saccharification process. The design of very active and stable β-glucosidase-based biocatalysts is a key strategy to implement an efficient saccharification process. Enzyme immobilization and reaction engineering are two fundamental tools for its understanding and implementation. Here, we have designed an immobilized-stabilized solid-supported β-glucosidase based on the glyoxyl immobilization chemistry applied in porous solid particles. The biocatalyst was stable at operational temperature and highly active, which allowed us to implement 25 °C as working temperature with a catalyst productivity of 109 mmol/min/gsupport. Cellobiose degradation was implemented in discontinuous stirred tank reactors, following which a simplified kinetic model was applied to assess the process limitations due to substrate and product inhibition. Finally, the reactive process was driven in a continuous flow fixed-bed reactor, achieving reaction intensification under mild operation conditions, reaching full cellobiose conversion of 34 g/L in a reaction time span of 20 min.

The Partial Oxidation of Methane to Hydrogen over M(1)-Ni(5)/AlCeO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;(M=Ce, La, Y) Catalysts

The catalytic yields of partial oxidation of methane (POM) to hydrogen over M(1)-Ni(5)/Al₂O₃(M=, Ce, La, Y) catalysts were investigated using a fixed bed flow reactor under atmospheric pressure to solve the global warming problem and clean energy demand. Catalyst activity is evaluated by performing the reaction of POM to hydrogen, and active sites of the catalyst are verified by instrumental analysis. The catalysts were characterized by XPS, XRD, FESEM, EDS, FETEM. The crystal phase behavior of reduced La(1)-Ni(5)/AlCeO₃ catalysts before and after the reaction were studied by XRD analysis. The crystalline phase of Ni and La on La(1)-Ni(5)/AlCeO₃ reduced before reaction was not obserbed due to uniform distribution of nanoparticles. FESEM and EDS analyses show that nanoparticles of Ni, La and Ce are uniformly distributed on the catalyst surface. In addition, TEM images and EDS mapping of La, Ni, Ce, O, and Al for a reduced La(1)-Ni(5)/AlCeO₃ catalyst before reaction show that the elements are well distributed. When 1 wt% of La was added to Ni(5)/AlCeO₃ catalyst, XPS results showed that O^-, O_vacancy, and O₂^- species, Ni₂p_3/2, and Ce3d_5/2increased 1.4, 52.7, 6.3% on the La(1)- Ni(5)/ AlCeO₃ catalyst, respectively. The yield of hydrogen on the La(1)- Ni(5)/ AlCeO₃ catalyst was 89.1%, which was much better than that of M(1)-Ni(5)/Al₂O₃(M=Ce, Y) catalysts. As Ce⁴⁺/Ce³⁺ ions in CeO₂ produced by the reaction of AlCeO₃ with oxygen were substitute to La³⁺, Ni²⁺, it made oxygen vacancies in the lattice and further improved the hydrogen yield by increasing the dispersion of Ni atoms with strong metal- support interaction (SMSI) effect.

Dehydrogenation of Dodecahydro-N-Ethylcarbazole Over Spinel Supporting Catalyst in a Continuous Flow Fixed Bed Reactor

Dehydrogenation of Dodecahydro-N-Ethylcarbazole Over Spinel Supporting Catalyst in a Continuous Flow Fixed Bed Reactor

Catalytic deoxygenation of fatty acids via ketonization and α-carbon scissions over layered alkali titanate catalysts under N2.

The ketonization of fatty acid with subsequent McLafferty rearrangement of the fatty ketone allows the deoxygenation to hydrocarbons. Here, we report the cascade reaction of palmitic acid (C16) to hydrocarbons (≤C14) over lepidocrocite-type alkali titanate K0.8Zn0.4Ti1.6O4, K0.8Mg0.4Ti1.6O4, and K0.8Li0.27Ti1.73O4 and the reassembled TiO2 catalysts at ≤400 °C under atmospheric N2 in a continuous fixed-bed flow reactor. The C16 acid is coupled to C31 ketone prior to the scissions mostly to a C17 methyl ketone and C14 hydrocarbons (i.e., the McLafferty rearrangement). The hydrocarbons yield increases with temperature and is proportional to partial charge at the O atom, suggesting that basic sites are responsible for C31 ketone scissions. The layered alkali titanate catalysts with two-dimensional (2D) space inhibit diffusion of the ketone primarily formed and promote its scissions to hydrocarbons within the confined space. Otherwise, low hydrocarbons yield (but high ketone yield) is obtained over TiO2 and the Mg/Al mixed oxide catalysts possessing no interlayer space. Meanwhile, the semi-batch experiment with pre-intercalated palmitic acid favors a direct deoxygenation, demonstrating the essential role of reaction mode toward ketone scission reaction pathway. Over K0.8Li0.27Ti1.73O4, the complete palmitic acid conversion leads to ∼47% hydrocarbons yield, equivalent to ∼80% reduction of the oxygen content in the feed under N2.

Cleaner Fuel Production via Co-Processing of Vacuum Gas Oil with Rapeseed Oil Using a Novel NiW/Acid-Modified Phonolite Catalyst

Clean biofuels are a helpful tool to comply with strict emission standards. The co-processing approach seems to be a compromise solution, allowing the processing of partially bio-based feedstock by utilizing existing units, overcoming the need for high investment in new infrastructures. We performed a model co-processing experiment using vacuum gas oil (VGO) mixed with different contents (0%, 30%, 50%, 70%, 90%, and 100%) of rapeseed oil (RSO), utilizing a nickel–tungsten sulfide catalyst supported on acid-modified phonolite. The experiments were performed using a fixed-bed flow reactor at 420 °C, a hydrogen pressure of 18 MPa, and a weight hourly space velocity (WHSV) of 3 h−1. Surprisingly, the catalyst stayed active despite rising oxygen levels in the feedstock. In the liquid products, the raw diesel (180–360 °C) and jet fuel (120–290 °C) fraction concentrations increased together with increasing RSO share in the feedstock. The sulfur content was lower than 200 ppm for all the products collected using feedstocks with an RSO share of up to 50%. However, for all the products gained from the feedstock with an RSO share of ≥50%, the sulfur level was above the threshold of 200 ppm. The catalyst shifted its functionality from hydrodesulfurization to (hydro)decarboxylation when there was a higher ratio of RSO than VGO content in the feedstock, which seems to be confirmed by gas analysis where increased CO2 content was found after the change to feedstocks containing 50% or more RSO. According to the results, NiW/acid-modified phonolite is a suitable catalyst for the processing of feedstocks with high triglyceride content.

Single-step synthesis of 2-pentanone from furfural over Cu–Ni @SBA-15

A single-step new route has been developed to synthesize 2-pentanone from biomass-derived furfural via simultaneous hydrodeoxygenation (HDO), ring-opening (RO) and hydrogenation reactions over a bi-metallic Cu–Ni/SBA-15 catalyst in a fixed-bed continuous flow reactor. Cu–Ni/SBA-15 catalysts were synthesized by the incipient wetness impregnation method. Synthesized catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (H2-TPR), TEM mapping, SEM, ICP-AES. Ammonia temperature-programmed desorption (NH3-TPD) analysis of catalysts revealed that moderate acidity of 10Cu–5Ni/SBA-15 catalyst favoured a high yield of 2-pentanone. DFT calculation, indicate the adsorption energy and the reaction mechanism of the molecules on the surface of 10Cu–5Ni/SBA-15 play a vital role for the desired product. The catalyst system was found highly active and selective, yielding (78%) of 2-pentanone under mild reaction conditions. The effect of reaction temperature was studied in detail, and time on stream analysis confirmed the catalyst is long-lasting stable up to 20 h of reaction duration.

Ethanol Dehydrogenation to Acetaldehyde over Co@N-Doped Carbon

Cobalt and nitrogen co-doped carbon materials (Co@CN) have recently attracted significant attention as highly efficient noble-metal-free catalysts exhibiting a large application range. In a similar research interest, and taking into account the ever-increasing importance of bioethanol as a renewable raw material, here, we report the results on ethanol dehydrogenation to acetaldehyde over Co@NC catalysts. The catalyst samples were synthesized by a variety of affordable techniques, ensuring generation of various types of Co species incorporated in carbon, such as subnanosized cobalt sites and nano-sized particles of metallic cobalt and cobalt oxides. The catalytic activity was tested under both oxidative and non-oxidative gas-phase conditions at 200–450 °C using a fixed-bed flow reactor. The non-oxidative conditions proved to be much more preferable for the target reaction, competing, however, with ethanol dehydration to ethylene. Under specified reaction conditions, ethanol conversion achieved a level of 66% with 84% selectivity to acetaldehyde at 400 °C. The presence of molecular oxygen in the feed led mainly to deep oxidation of ethanol to COx, giving acetaldehyde in a comparatively low yield. The potential contribution of carbon itself and supported cobalt forms to the observed reaction pathways is discussed.

Hydrotreating of Waste Tire Pyrolysis Oil over Highly Dispersed Ni2P Catalyst Supported on SBA-15

A highly dispersed nickel phosphide catalyst supported on SBA-15 was prepared and tested for the hydrotreating of tire pyrolysis oil (TPO). Physicochemical properties of the prepared catalyst were analyzed by CO uptake chemisorption, BET, TEM, and X-ray diffraction (XRD). An advanced technique with gas chromatography equipped with mass spectrometry and atomic emission detector was applied to investigate carbon-, sulfur-, and nitrogen-containing compounds in TPO. Hydrotreating tests were carried out in a fixed-bed continuous flow reactor at 350 °C, 3.0 MPa, and LHSV of 0.5 h−1. The Ni2P/SBA-15 exhibited an HDS conversion of 89.3% and an HDN conversion of 60.7%, which was comparable to the performance of a commercial NiMoS catalyst under the same conditions.

Mutual inhibition effect of sulfur compounds in the hydrodesulfurization of thiophene, 2-ethylthiophene and benzothiophene ternary mixture

The hydrodesulphurization of a model component and equimolar ternary mixture of thiophene, 2-ethylthiophene and benzothiophene over sulphided CoMo/γ-Al2O3 and CoMo/γ-Al2O3-Nb2O5 catalysts were investigated in a fixed bed flow reactor. The catalysts were prepared by incipient wetness impregnation method and characterized by textural characteristics, total acidity and chemical species present on the catalysts surface. The characterization results showed that both CoMo/γ-Al2O3-Nb2O5 and sulphided CoMo/γ-Al2O3 catalysts exhibit a mesoporous structure with cylindrical pores open at both ends, evidenced by the IV type adsorption–desorption isotherm with a H1 hysteresis loop and have an average pore diameter between 3 and 4 nm. The chemical species present on the catalysts surface evaluated by XPS indicated that Co2+ and Mo4+ species are present in the sulfide form on both catalysts surfaces. In addition, there are also found oxidic species arising from incomplete reduction and sulphidation. The presence of niobium oxide in the catalytic support had a positive effect in leading to higher specific surface area (170 m2/g) and total acidity (0.421 meq/g) compared with CoMo/γ-Al2O3 catalyst (140 m2/g and 0.283 meq/g) respectively. The evaluation results from the hydrodesulfurization showed that CoMo/γ-Al2O3-Nb2O5 catalyst had a higher activity in hydrodesulphurization process of thiophene, 2-ethylthiophene and benzothiophene. The CoMo/γ-Al2O3-Nb2O5 catalyst eliminated sulfur from the single component feed (corresponding to 2380 ppm S) and reduced below 10 ppm, for the feed consisting in the equimolar ternary mixture of thiophene, 2-ethylthiophene and benzothiophene (2380 ppm S). The reactivity of thiophen compounds was reduced due to competitive adsorption. It was observed that benzothiophene inhibits the transformation of thiophene and 2-ethylthiophene. A mutual inhibition effect between sulfur compounds was also observed when thiophene, 2-ethylthiophene and benzothiophene were combined and tested over the CoMo/γ-Al2O3 catalyst. The inhibition effect had a lower intensity by introducing Nb2O5 in the catalyst support.

Catalytic Pyrolysis of Methane to Hydrogen over Carbon (from cellulose biochar) Encapsulated Iron Nanoparticles

The catalytic performance of carbon encapsulated iron nanoparticles (CEINPs) for methane decomposition was investigated over a range of temperatures between 700 and 800 °C with varying iron concentrations (20, 30, and 40 wt %) in a semicontinuous flow fixed bed reactor. CEINPs were prepared by impregnating a cellulose biochar support (carbon source) with iron nitrate solution. This mixture was dried at 110 °C for 72 h in air followed by pyrolysis at 1000 °C in a N2 atmosphere. Unlike conventional iron-based catalysts, in CEINPs, the iron nanoparticles were encapsulated in a graphitic shell that prevented atmospheric oxidation and sintering at high temperature, improving the thermal stability of the catalysts. The fresh CEINPs did not contain any metal oxides and had only the following phases: elemental iron, iron carbides, activated carbon, and graphitic carbon, which allowed for the catalyst reduction step (in H2) to be eliminated. The decomposition of methane being an endothermic reaction showed better catalytic activity with an increase in temperature with the highest conversion of 95.7% observed at 800 °C. There are four different active sites in the catalyst, namely, graphite, graphite encapsulated iron nanoparticles, uncovered iron nanoparticles, and activated carbon. In the case of 20 wt % CEINP, the presence of higher amounts of activated carbon and graphite with a lower amount of Fe negatively impacted methane decomposition, confirming the importance of Fe as an active site. At 800 °C, the maximum catalytic performance was exhibited by 30 wt % CEINP where the initial methane conversion was 95.7% and dropped to 36.8% after 180 min of reaction. The higher conversion was due to the combined optimum amounts of Fe, graphite, and activated carbon active sites. In the case of 40 wt % CEINP, the higher amount of Fe resulted in the agglomeration of Fe nanoparticles and reduction in surface area, leading to lower methane conversions. The surface area of the spent catalysts reduced appreciably in all cases due to carbon deposition from CH4 in the form of coke and graphite (on non-encapsulated Fe nanoparticles), resulting in catalyst deactivation.

Long-chain bio-olefins production via oxidative dehydrogenation of oleic acid over vanadium oxides/KIT-6 catalysts

Long-chain α-olefins (≥ C10) are normally applied in detergents, lubricants, and oil field chemicals. Due to the abundance of palm oil, the derivatives derived from palm oil, such as oleic acid (OA), can be converted to long-chain olefins via oxidative dehydrogenation (ODH) over a series of vanadium oxides (VxOy) incorporated with KIT-6 (nV-KIT-6 catalysts) synthesized by a direct hydrothermal method. Various ammonium metavanadate/tetraethyl orthosilicate molar ratios (V/Si) were evaluated over the range of 0.01–0.09. The results obtained from X-ray diffractometry, hydrogen-temperature programmed reduction, and X-ray photoelectron spectroscopy analyses revealed that the VxOy were mainly in a tetrahedral form when the V/Si molar ratios were lower than 0.05. Above this point, the formation of V2O5 crystallites was observed. The ODH of OA was performed in a continuous flow fixed-bed reactor under atmospheric pressure in the absence of solvent to avoid the interference of by-products generated from solvent oxidation. The results showed that the OA conversion and selectivity towards the desired products strongly depended on the V/Si molar ratio and the reaction temperature. The highest selectivity of olefins (alkenes + dienes) with carbon atoms in the range of C7–17 was 44%. Moreover, the selectivity to aromatics at 24% was observed at a 76% OA conversion level when the ODH was activated using the 0.05 V-KIT-6 catalyst under a 1/1 (v/v) oxygen/nitrogen gas mixture at a flow rate of 100 mL min−1 at 450 °C. Although the high selectivity towards alkenes was promoted by a higher dispersion of VxOy species on the catalyst, overdose of V/Si molar ratios produced more oxygenate compounds. The reaction mechanism for the ODH of OA was likely to be decarboxylation and decarbonylation followed by dehydration. The 0.05 V-KIT-6 catalyst also exhibited reusability over two cycles.

Hybrid Cu-Fe/ZSM-5 Catalyst Prepared by Liquid Ion-Exchange for NOx Removal by NH3-SCR Process

A series of Cu/ZSM-5, Fe/ZSM-5, and Cu-Fe/ZSM-5 catalysts (Si/Al in ZSM-5 = 25) were prepared by different metal loadings using the liquid ion-exchange method. Several characterization methods were conducted to explore the effects of metals on the physical and chemical properties of catalysts. Meanwhile, the electron paramagnetic resonance method is also used to assess the copper and/or iron elements’ coordination and valence state at intersections or in channels of ZSM-5. The metal-loading effects of all catalysts on the catalytic activities were studied for the removal of NOx in a fixed-bed flow reactor using selective catalytic reduction with ammonia (NH3-SCR). The results showed that the iron’s addition could markedly broaden the operation temperature range of the Cu/ZSM-5 catalyst for NH3-SCR between 200 and 550°C due to the presence of more isolated Cu2+ ions as well as additional oligomeric Fe3+ active sites and FexOy oligomeric species. This paper gives a facile and straightforward way to synthesize the practical-promising catalyst applied in NH3-SCR technology to control NOx emissions.

First row transition metals on the ethanol Guerbet reaction: Products distribution and structural behavior of mixed metal oxides as catalysts

Described is the transformation of ethanol into 1-butanol, acetaldehyde and other products by the Guerbet reaction (GR) over mixed metal oxides (MMOs) as catalysts. The MMOs, in which Mg2+ was partially (20 mol%) substituted by Fe2+, Co2+, Ni2+, Cu2+, and Zn2+, were obtained from hydrotalcite precursors and the reactions conducted in a fixed bed flow reactor. EPR was used to observe oxygen vacancies after the catalytic reactions, which may be related to the ethanol reactivity due to the basicity enhancement of the catalyst. Carbon deposition, mostly filamentous, was observed in all catalysts and a trend between the metal-carbon bond energy and the percentage of deposited carbon was established. This correlation and the catalyst product distribution can be useful to tailor new catalysts. Using four parameters, ethanol conversion, 1-butanol and side-product selectivities and percentage of carbon deposition, Zn20MMO proved to be the best choice for GR.

N-Butene Synthesis in the Dimethyl Ether-to-Olefin Reaction over Zeolites

Zeolite catalysts that could allow the efficient synthesis of n-butene, such as 1-butene, trans-2-butene, and cis-2-butene, in the dimethyl ether (DME)-to-olefin (DTO) reaction were investigated using a fixed-bed flow reactor. The zeolites were characterized by N2 adsorption and desorption, X-ray diffraction (XRD), thermogravimetry (TG), and NH3 temperature-programmed desorption (NH3-TPD). A screening of ten available zeolites indicated that the ferrierite zeolite with NH4+ as the cation showed the highest n-butene yield. The effect of the temperature of calcination as a pretreatment method on the catalytic performance was studied using three zeolites with suitable topologies. The calcination temperature significantly affected DME conversion and n-butene yield. The ferrierite zeolite showed the highest n-butene yield at a calcination temperature of 773 K. Multiple regression analysis was performed to determine the correlation between the six values obtained using N2 adsorption/desorption and NH3-TPD analyses, and the n-butene yield. The contribution rate of the strong acid site alone as an explanatory variable was 69.9%; however, the addition of micropore volume was statistically appropriate, leading to an increase in the contribution rate to 76.1%. Insights into the mechanism of n-butene synthesis in the DTO reaction were obtained using these parameters.

Catalytic hydrocracking, hydrogenation, and isomerization reactions of model biomass tar over (W/Ni)-zeolites

Producing bio-based aromatic substrates is becoming increasingly of (industrial) interest. In this mechanistic work, the gas phase conversion of the biomass tar chemical model compounds (5 wt% naphthalene/95 wt% 1-methylnaphthalene) over the different pristine/metal-modified zeolites in a continuous flow fixed bed reactor was investigated. Bifunctional redox acid process catalysts were synthesized by wet impregnation method. The effect of the W (/Ni) metal formulation additives to the pristine H-beta, H-USY, H-Y, and H-ZSM-5 in the hydrocracking, hydrogenation, and isomerization transformation reactions of the mixture under applied ambient pressure was firstly studied. Structure, texture, morphology, acidity, composition and properties were determined by various analytical techniques. Results showed that the highest catalytic activity with a comparison to others was established over the 20 wt% W-beta with 96.0 mol% of the selectivity to 2-methylnaphthalene, the 93.3 mol% reacted total reactant after the 24 h time on stream, where ethylene/propane were predominating (80.5 wt%), and facile manufacturing scalability. Detailed characterization methodologies have revealed that after the loading of W onto H-beta_support, a uniform functional distribution of particles, the dealumination of framework and strong interaction phenomena were observed, which led to an increase in the amount of Brønsted/Lewis/reduction surface sites, and hence, increase stability of the catalyst. In addition, equilibrium coke formation was detected, decreasing all estimated rates, undergoing also consequent external deactivation, blocking pores, and its burning-off regeneration being needed. While both spent W-modified (20 wt%)/unmodified H-beta/ZSM-5 exhibited the lowest carbon quantity, the same fresh materials possessed the uppermost hierarchy factors.