Fixed-bed Tubular Reactor Research Articles

Preparation of an Adsorbent Derived from Canola Hull by Slow Pyrolysis for Effective Carbon Dioxide Adsorption

Canola hull was proposed as a valuable precursor for activated carbon production, due to its abundance, low cost, and economic viability. This study aimed to develop a waste-based biosorbent from canola hulls by slow pyrolysis for effective CO2 capture. The biochar was synthesized from the canola hull using a fixed-bed tubular reactor through slow pyrolysis at various temperatures. The optimum biochar was activated using KOH as a chemical activating agent at different impregnation ratios. The biochar and activated carbon were characterized by elemental analysis, thermogravimetric analysis, surface textural analysis and FT-IR analysis. All the activated carbon samples with impregnation ratios of 0, 0.2, and 0.4 were screened at a total inlet mass flow rate of 100 mL/min (15% CO2 + 85% N2). Activated carbon prepared with an impregnation ratio of 0.4 (0.4AC) with a specific surface area of 1112 m2/g exhibited the highest adsorption capacity of CO2 (2.9 mmol/g) at 25°C under ambient pressure when the feed gas was 15% CO2). 0.4AC was chosen for further study at different feed compositions. The breakthrough curves were analyzed for the compositions 5%, 15% and 25% CO2 in feed, and the effects of adsorption parameters were discussed. The maximum CO2 uptake of the canola hull based activated carbon (0.4AC) is 13.0 mmol/g at ambient pressure and 25°C, with 100% CO2 inlet. Adsorption isotherm and kinetic were studied on the 0.4AC adsorbent. The canola hull based adsorbent with desirable physiochemical and surface textural properties can work as an effective adsorbent for CO2 capture.

Efficient one-pot tandem C-C formation reaction catalyzed by a multi-functionalized polyacrylonitrile fiber catalyst

A simple and straightforward method has been proposed in this work to construct a multi-functionalized polyacrylonitrile fiber catalyst containing carboxylic acid, tertiary amine, and quaternary ammonium salt to enable series one-pot C-C bond formation in water. The fiber catalyst was prepared from polyacrylonitrile fiber using a two-step method and characterized using various detection techniques. Furthermore, the activity of multi-functional synergistic catalysts can be controlled by adjusting the ratio of acid and base. It is noteworthy that the polyacrylonitrile fiber catalyst with an acid-base ratio of 3:1 (PANF-ABNCl3/1) exhibited superior catalytic activity and high yield in a variety of C-C generation reactions. Additionally, the PANF-ABNCl3/1 catalyst demonstrated exceptional recyclability (at least 10 times) and performed well in scale-up (7.4g, 96%) and continuous flow experiments (can be used continuously for 7 × 24h) using kettle and tubular fixed bed reactor respectively. These findings suggest that the PANF-ABNCl3/1 catalyst holds promise for industrialization.

Superhydrophobic Surface Modification of a Co-Ru/SiO2 Catalyst for Enhanced Fischer-Tropsch Synthesis

Commercial silica support pellets were impregnated and calcined to contain cobalt oxide and ruthenium oxide for Fischer-Tropsch synthesis (FTS). The precatalyst pellets were split evenly into two groups, the control precatalyst (c-precat) and silylated precatalyst (s-precat), which were treated with 1H,1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOS) in toluene. The samples of powderized s-precat were superhydrophobic, as determined by the water droplet contact angle (>150°) and sliding angle (<1°). Thermal analysis revealed the PFOS groups to be thermally stable up to 400 °C and temperature programmed reduction (TPR) studies showed that H2 reduction of the cobalt oxide to cobalt was enhanced at lower temperatures relative to the untreated c-precat. The two active catalysts were examined for their FTS performance in a tubular fixed-bed reactor after in situ reduction at 400 °C for 16 h in flowing H2 to give the active catalysts c-cat and s-cat. The FTS runs were performed under identical conditions (255 °C, 2.1 MPa, H2/CO = 2.0, gas hourly space velocity (GHSV) 510 h–1) for 5 days. Each catalyst was examined in three runs (n = 3) and the mean values with error data are reported. S-cat showed a higher selectivity for C5+ products (64 vs. 54%) and lower selectivity for CH4 (11 vs. 17%), CO2 (2 % vs. 4 %), and olefins (8% vs. 15%) than c-cat. S-cat also showed higher CO conversion, at 37% compared to 26%, leading to a 64% increase in the C5+ productivity measured as g C5+ products per g catalyst per hour. An analysis of the temperature differential between the catalyst bed and external furnace temperature showed that s-cat was substantially more active (DTinitial = 29 °C) and stable over the 5-day run (DTfinal = 22 °C), whereas the attenuated activity of c-cat (DTinitial = 16 °C) decayed steadily over 3 days until it was barely active (DTfinal < 5 °C). A post-run surface analysis of s-cat revealed no change in the water contact angle or sliding angle, indicating that the FTS operation did not degrade the PFOS surface treatment.

Desulfurization reactions of thiophene and cyclohexane over Zn and Nb modified zeolites in FCC process

In refineries, one of the most important production units is Fluid Catalytic Cracking (FCC). In them, the incorporation of additives to the catalyst is a very interesting option to reduce the sulfur content of gasoline, and thus obtain commercial fuel specifications. In this study, the transformation of thiophene into a cyclohexane (HC) stream for its in-situ desulfurization has been investigated, using catalysts based on niobium or zinc (6 wt%) incorporated into three types of zeolites: HUSY, HBeta and HZSM-5. Catalytic tests were carried out at 773 K in an automatically controlled fixed-bed tubular reactor. The reaction products were analyzed online by gas chromatography, with FID detector for hydrocarbons and SCD for sulfur compounds, and the catalysts were characterized by XRD, FTIR, N2 adsorption isotherms, HRTEM, XRF, 29Si and 27Al solid state NMR, NH3-TPD and FTIR-pyridine techniques. The results indicate that the addition of metals did not significantly alter the textural and structural properties of the zeolites, and that the Nb/HB and Nb/HY catalysts were the most effective in the conversion of thiophene, and selective toward paraffins and H2S mainly. The performance of these materials was attributed to the existence of an optimal balance between the Brønsted and Lewis acid sites, which increased the hydrogen transfer coefficient (HTC) during the cyclohexane transformation, resulting in higher desulfurization activity. The addition of zinc drastically increased the density of the Lewis acid sites and decreased the HTC, favoring the production of aromatics and thiophene condensation reactions, thus transferring sulfur to the gasoline streams. In general, the catalysts investigated are of significant interest as additives for sulfur reduction in FCC gasoline streams, either by producing easily removable H2S or by transferring sulfur to heavier fractions.

Catalytic pyrolysis of apricot kernel shell over metal supported MCM-41 catalysts obtained by synthesizing sonochemical method

In this study, it is targeted to examine the efficiency of metal supported MCM-41 catalysts on the liquid product yield from pyrolysis process of apricot kernel shell selected as a biomass and to characterize the pyrolysis liquids. In the non-catalytic pyrolysis experiments, the maximum liquid yield is obtained as 21.41 % at 500 °C. At the determined optimum condition, catalytic pyrolysis process of the biomass sample is performed with metal supported MCM-41 catalysts synthesized by sonochemical method (metal: aluminium, cobalt, iron) at different ratios to biomass (1 and 2 wt %). The pyrolysis procedures of apricot kernel shell are carried out in a tubular fixed-bed reactor at different pyrolysis temperatures. The use of catalysts improved both the liquid product (tar) yield and tar quality in respect to the calorific value, the distribution of hydrocarbons and the elimination of oxygenated groups. The results revealed that all metal-supported MCM-41 catalysts, especially the Fe-MCM-41 catalyst ratio of 2, showed an excellent catalytic ability for thermal conversion of biomass. In the catalytic pyrolysis experiments carried out at 500 °C, 75.84 % conversion to liquid and gaseous products was obtained using 2 % Fe-MCM-41 catalyst, and the calorific value of the liquid product obtained was determined as 40.96 MJ/kg. The functional group analyses in the structure of the liquid products are characterized using FT-IR spectroscopy, and the distributions of the aliphatic/aromatic fractions of the liquid products are characterized using GC-MS technique. The H/C ratio of the liquid product obtained from catalytic pyrolysis is between light and heavy petroleum products and also has lower oxygen content and higher calorific value, indicating the potential of metal-supported MCM-41 catalyst for renewable hydrocarbon production from apricot kernel shell.

Carbon dioxide conversion to fuel over alumina-supported ruthenium catalysts

In this study, ruthenium-based catalysts were prepared for CO2 hydrogenation. Incipient-wetness-impregnation of the alumina-support with ruthenium (III) nitrosyl nitrate solution to achieve 0.5 wt% Ru loading on supports was used to prepare these catalysts. Potassium (0–3 % wt%) was used to further promote the catalysts. TPR, CO2-TPD, XRD, TEM, XPS, SEM, and EDS analyses were used to characterize catalyst properties. The hydrogenation of CO2 catalytic tests were conducted and the effect of operating conditions (temperature, pressure, and space velocity) were investigated. These studies were conducted in a tubular fixed-bed reactor. The CO2 conversion over these catalysts was found to be low and the dominating product observed was CH4 with a small amount of C2+ forming when K was added to the catalyst. The optimum potassium loading for improved C2+ product yield over Ru/Al2O3 was 1%K for CO2 hydrogenation.

Study of Ni-Co-ZrO2/Al2O3 Catalysts for Carbon Dioxide Reforming of Methane at Low CO2

This work studied the composition of Ni-Co-ZrO2/Al2O3 catalyst on properties and efficiency of catalysts for carbon dioxide reforming of methane (CMR) when CO2 was fed as the limiting reagent and CH4 as the excess reactant. 9wt%Ni-1wt%ZrO2/Al2O3, 4.5wt%Ni-4.5%wtCo-1wt%ZrO2/Al2O3, 9wt%Co-1wt%ZrO2/Al2O3 and 7wt%Co-3wt%ZrO2/Al2O3 catalysts were prepared by wet impregnation method. The physicochemical properties of present catalysts were characterized by XRD, N2 adsorption-desorption H2-TPR and CO2-TPD. The CRM performance was determined in a tubular fixed-bed reactor at 600 °C for 6 h with limiting of carbon dioxide. The carbon deposition on spent catalysts were examined by TGA. The results showed that Co-ZrO2 catalysts provided greater activities, selectivity toward H2 and stability than Ni-ZrO2 and Ni-Co-ZrO2 catalysts. 9wt%Co-1wt%ZrO2/Al2O3 provided higher reactant conversions and H2/CO ratio than 7wt%Co-3wt%ZrO2/Al2O3 while the minimum coke formation was observed on spent 7wt%Co-3wt%ZrO2/Al2O3. It is because oxophilic properties and oxygen vacancy sites in Co-ZrO2 increase CO2 dissociative adsorption as well as oxygen transport on the catalyst surface. HIGHLIGHTS This work developed Ni-Co-ZrO2/Al2O3 catalysts for carbon dioxide reforming of methane (CMR) when CO2 is fed as the limiting reagent demonstrated petroleum refinery application. Remarkable points of this work are revealed below. Co-ZrO2 catalysts provided greater reactant activities, selectivity toward H2 and stability than Ni-ZrO2 and Ni-Co-ZrO2 The oxophilic property accompanied with oxygen vacancy sites in Co-ZrO2 increase CO2 dissociative absorption and oxygen transport on the catalyst surface. 9wt%Co-1wt%ZrO2/Al2O3 provided relative highest reactant conversions and highest H2/CO ratio. 7wt%Co-3wt%ZrO2/Al2O3 presented the minimum coke formation. GRAPHICAL ABSTRACT

Thermo-catalytic co-pyrolysis of waste biomass and non-recyclable polyethylene using ZSM-5 into renewable fuels and value-added chemicals

The present study deals with thermo-catalytic co-pyrolysis of peanut shells (PS) and non-recyclable polyethylene (NRPE) using ZSM-5 at varying ratios (5, 10 and 15 wt%). A tubular fixed bed reactor is used to pyrolyse at 500 °C, 50 °C min−1 heating rate and 100 mL min−1 inert gas flow rates. The feedstock was characterized via proximate analysis, elemental analysis, higher heating value (HHV), biochemical analysis, thermogravimetric analyser (TGA), Fourier transforms infrared spectroscopy (FTIR) viscosity, density, Gas chromatography-mass spectrometry (GC-MS), BET surface area, water holding capacity (WHC). Co-pyrolysis results confirmed maximum liquid yield (34.50 %) at 10 wt% of NRPE; however, adding 10 wt% ZSM-5 again boosted the liquid oil yield by 7.87 wt%. Pyrolytic oil characterization results confirmed that adding NRPE and ZSM-5 at 10 wt% decreased viscosity, acidity, and density. However, carbon content, heating value and ash content increased. FTIR examinations of PS confirmed hydrocarbons, acids, water, and oxygenated compounds. GC-MS results were confirmed by adding NRPE and ZSM-5 at 10 wt%; hydrocarbon and furfural increased by 5.31 and 5.46 %, whereas 6.01 % acids and oxygenated compounds decreased, respectively. The results of the char characterisation further supported the findings that adding NRPE (10 wt%) to PS enhanced carbon content and HHV by 11.86 % and 4.35 MJ kg−1 and decreased ash content, oxygen content, and bulk density by 0.75 %, 10.21%, and 71.98 kg m−3, respectively.

CO2 methanation over low-loaded Ni-M, Ru-M (M = Co, Mn) catalysts supported on CeO2 and SiC

The concentration of the major greenhouse gas CO2 is rapidly increasing in the atmosphere, leading to global warming and a range of environmental issues. An efficient circulation and utilization of CO2 is critical in the current environmental context. Methanation, an exothermic process, emerges as a critical strategy for effective CO2 utilization. On this front, there is a significant demand for rational design of catalysts that maintain high activity and methane selectivity over a wide temperature range (250–550 °C). The catalyst that can promise a consistent reaction even at 500 °C under an atmospheric pressure is thus obliged. The present study investigated bimetallic catalysts with SiC, which is known for its exceptional thermal conductivity, and CeO2, which is characterized by its CO₂ affinity, as base materials. We incorporated Ni-M and Ru-M (M = Co and Mn) as the active metals, each loaded at 2 %. Impressively, with merely 20 mg, the Ni-Co/SiC catalyst achieved a CO2 conversion rate of 77 % and CH₄ selectivity of 88 % at 500 °C, in a fixed-bed tubular reactor system with conditions of H2/CO2 = 4, a total flow rate of 70 ml min−1, and a steady GHSV of 12,000 h−1. Moreover, 2Ni-2Co/CeO2 catalyst demonstrated exceptional performance with a 76 % conversion of CO2 and a 83 % selectivity for CH4, all under identical conditions. The catalyst's durability was confirmed by a subsequent 40-hour stability test, which showed only a 3–5 % degradation. The developed catalysts were comprehensively characterized by BET/BJH, CO pulse chemisorption, H2-TPR, HAADF-STEM-EDS, SEM-EDS and XRD etc. to unveil their physicochemical and surface traits. It was found that Co and Mn, when integrated, effectively restrained the agglomeration of Ni and Ru particles, ensuring optimal metal dispersion on the support. In conclusion, our synthesized bimetallic catalysts shown a sustained catalytic capability, even in the high-temperature environment.

Profile of the Effectiveness Factor under Optimal Operating Conditions for the Conversion of Ortho-Xylene to Phthalic Anhydride in a Fixed-Bed Tubular Reactor

The objective of this research is to find the effectiveness factor of the catalyst particles for the most favorable conditions of the phthalic anhydride production in a fixed bed reactor, with the aim of achieving the highest rate of phthalic anhydride production compared to other secondary products and analyzing the areas of lower effectiveness for the modification of the reactor design. Initially, the material and the energy balances in the catalytic bed are solved to obtain the concentration and temperature profiles based on the radius and length of the reactor, using polymath software(Polymath® v6.2 Software Minitab 19 Matlab 2019) with the data from literature. Once the profiles reproducibility was verified using the initial data (inlet temperature, pressure in the reactor, reactor wall temperature, reactor radius and mass flow rate) the experimental design 35 carry out, which generates 243 “experiments”, whose response variable (phthalic anhydride concentration) was obtained using Matlab. Subsequently, the variables were analyzed using the Minitab 18® that, through the response surface analysis method, allowed us to obtain the optimal values of the tested variables. Then, Subsequently, material and energy balances coupled with Fourier and Fick’s laws, along with the effectiveness factor equation, were applied, resulting in the generation of 9 coupled differential equations. Upon implementing the finite difference method, this yielded 90 nonlinear algebraic equations, which were solved using the Polymath software. A total of 78 particles were preselected based on their radial and axial positions to determine the effectiveness factor profile, with values ranging from 0.83 to near unity. The lower values correspond to the points with higher temperature, as evidenced by the calculations performed.

Kinetic Modeling of the Direct Dimethyl Ether (DME) Synthesis over Hybrid Multi-Site Catalysts

This paper deals with the proposition of a kinetic model for the direct synthesis of DME via CO2 hydrogenation in view of the necessary optimization of the catalytic system, reactor design, and process strategy. Despite the fact that DME synthesis is typically treated as a mere combination of two separated catalytic steps (i.e., methanol synthesis and methanol dehydration), the model analysis is now proposed by taking into account the improvements related to the process running over a hybrid catalyst in a rational integration of the two catalytic steps, with boundary conditions properly assumed from the thermodynamics of direct DME synthesis. Specifically, the CO2 activation step at the metal–oxide interface in the presence of ZrO2 has been described for the first time through the introduction of an ad hoc mechanism based on solid assumptions from inherent studies in the literature. The kinetic modeling was investigated in a tubular fixed-bed reactor operating from 200 to 260 °C between 1 and 50 bar as a function of a gas hourly space velocity ranging from 2500 to 60,000 NL/kgcat/h, in a stoichiometric CO2/H2 feed mixture of 1:3 v/v. A well-detailed elementary mechanism was used to predict the CO2 conversion rate and identify the key reaction pathways, starting with the analysis of the implicated reactions and corresponding kinetic mechanisms and expressions, and finally estimating the main parameters based on an appropriate modeling of test conditions.

Study on the Flow Dead Zone in the Shell of an Industrial Tubular Fixed Bed Reactor

Study on the Flow Dead Zone in the Shell of an Industrial Tubular Fixed Bed Reactor

Spatiotemporal operando UV–vis spectroscopy: Development and mechanistic alternation of CO oxidation on Pt/Al2O3 on the reactor scale

Operando methodologies are widely used in heterogenous catalysis to understand unique state of catalyst materials emerging under specific reaction conditions and to establish catalyst structure-activity relationships. Recent studies highlight the importance of combining multiple operando techniques (multimodal approach) to gain complementary information as well as looking into chemical and material gradients and spatial variations on the reactor scale. In this work, we developed an operando UV–vis diffuse reflectance spectroscopy (DRS) setup compatible with a common fixed-bed tubular reactor. The design is based on optical calculations, validation experiments and signals considerations. A spatial resolution of 1 mm along the axial direction of the reactor was successfully demonstrated and combined with a time resolution of seconds with good signal to noise. CO oxidation over Pt/Al2O3 was performed as a proof of principle experiment demonstrating the capabilities of the new setup. The information gained by the space-resolved operando UV–vis DRS was combined with other space-resolved operando studies such as diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), gas sampling and temperature profiling. The study shows that the nature of active sites (Pt redox state) and thus the reaction mechanism alter with reaction temperature and also in space. Spatiotemporal UV–vis DRS is also demonstrated, showing the capability for transient studies with space-resolution.

Integral recycling of polyester based end-of-life fibre reinforced plastic waste towards syngas generation

Valorisation of chemical compounds derived from the thermal decomposition of the plastic matrix in fibre reinforced plastic waste is claimed as crucial for cost-effective recycling of this waste. This work, validated the application of a thermal treatment (900 °C) to the volatiles generated from the pyrolysis of four end-of-life glass fibre reinforced polyester waste in a fixed bed tubular reactor placed in series with the pyrolysis reactor. Thermal treatment of pyrolysis volatiles' improves current scenario by transforming the hazardous liquids and low quality gas into almost non-existent aqueous liquid and maximised synthesis gas stream (CO + H2).

Top-down vs. bottom-up synthesis of Ga–based supported catalytically active liquid metal solutions (SCALMS) for the dehydrogenation of isobutane

Supported catalytically active liquid metal solutions (SCALMS) catalysts consist of a liquid metal solution of an active metal (e.g., Pd, Rh, Pt, Ni) in a low melting metal (e.g., Ga, In, Sn) deposited on a porous support material. In the current study, we extend and optimize the recently developed top-down synthesis protocol (ultrasonication of gallium metal) to prepare GaPd, GaRh and GaPt SCALMS systems. We compare the morphological differences in the obtained catalyst materials achieved between this approach and the more traditional bottom-up synthesis protocol (in situ thermal decomposition of triethylamino-gallane complex) using electron microscopy. Moreover, the spatial distribution of the catalytically active material in the porous alumina support is evaluated using high resolution argon physisorption measurements. Both techniques strongly indicate that the bottom-up approach leads to a high degree of pore penetration while the gallium droplets are largely on the outer surface in case of the top-down method. Changes to the surface chemistry of the support were also investigated by means of NH3/CO2 temperature programmed desorption. All catalytic systems synthesized by the two synthesis methods, i.e., GaPd, GaRh and GaPt, were tested in a quartz, fixed-bed tubular reactor for isobutane dehydrogenation. All SCALMS materials, irrespective of their individual synthesis protocol, were significantly more active than their pure metal counterparts. The SCALMS catalyst prepared using the bottom-up approach showed initial productivity of 407gbutenes molM–1 min−1, 832gbutenes molM–1 min−1, and 963gbutenes molM–1 min−1 for the GaPd, GaRh and GaPt respectively. These values represent more than twice the initial activity obtained with the top-down synthesized counterparts. This activity difference can be explained by the analytically determined difference in liquid metal droplet size distribution.

Influence of alumina fixed-bed in steam reforming of glycerol for hydrogen production

In this study, hydrogen production by steam reforming was carried out in a tubular fixed-bed reactor. The influence of some operating variables such as temperature, flow rate of the feeding glycerol solution and space velocity on hydrogen production under a non-catalyzed reaction was analyzed. The results showed that the hydrogen yield increased with temperature and decreased with the space velocity. As the feedstock flow rate increased, the hydrogen yield decreased rapidly. Compared with a reference experiment without fixed-bed, the use of non-porous alumina fixed-bed showed better results. Under the best reaction conditions (900 °C and a feedstock flow rate of 0.85 g/min), 17 L/h of syngas were obtained, with a purity of about 55% of hydrogen and a production of 2.7 moles of hydrogen by mol of glycerol.

Response surface optimization of hydrogen-rich syngas production by the catalytic valorization of greenhouse gases (CH4 and CO2) over Sr-promoted Ni/SBA-15 catalyst

Dry reforming of methane (DRM) which utilizes CO2 and CH4, is a more efficient and environmentally friendly syngas production method. However, since the technique is endothermic, catalyst deactivation from sintering and carbon deposition has prevented its industrial implementation. This study investigated the effect of Strontium (Sr) promoter on Ni-based catalyst synthesized on SBA-15 support via the impregnation method. The incorporation of Sr as a promoter has demonstrated distinct advantages, primarily attributed to its remarkable capability to inhibit carbon formation. This property imparts a notable enhancement in the stability of the catalyst, thereby extending its operational lifespan and maintaining consistent catalytic performance. The physicochemical properties of the fresh catalyst were observed by using various characterization techniques such as X-Ray diffraction (XRD) analysis, N2 physisorption analysis, field emission scanning electron microscopy (FESEM), and temperature programmed reduction using hydrogen as the probing gas (TPR-H2). The catalysts were tested in DRM reaction using a tubular fixed bed reactor at 800 °C with an equimolar feed ratio. Overall, 1% Sr promoted Ni/SBA-15 showed enhanced performance having CO2 and CH4 initial conversions of 88.5% and 96.5%, respectively while remaining stable for 320 min on stream. Furthermore, the predicted optimal condition was 713.73 °C and a feed gas ratio (CH4:CO2) of 1.12, with CO2 and CH4 conversion rates of 69.59% and 84.83%, respectively, resulting in an H2:CO ratio of 1.00. Slight differences from the predicted values were considered insignificant, validating the Srb catalyst at a 95% confidence level with a 5% likelihood of error in the RSM model.

Non-Catalytic and Catalytic Conversion of Fruit Waste to Synthetic Liquid Fuel via Pyrolysis

Plum stone stands out as an alternative biomass source in terms of obtaining fuel and chemicals with or without catalysts under different conditions. Under variable heating rates (10, 50, and 100 °C min−1) and pyrolysis temperatures (400, 450, 500, 550, and 600 °C), plum stone was pyrolyzed at a constant rate in a constant sweep gas flow (100 cm3 min−1) in a tubular fixed-bed reactor. According to the results, an oil yield reaching a maximum of 45% was obtained at a heating rate of 100 °C min−1 and pyrolysis temperature of 550 °C in the non-catalytic procedure. The catalytic pyrolysis was carried out with two selected commercial catalysts, namely ZSM-5 and PURMOL-CTX and clinoptilolite (natural zeolite, NZ) under optimum conditions with a catalyst ratio of 10% of the raw material. With the addition of catalyst, the quantity and quality of bio-oil increased, including calorific capacity, the removal of oxygenated groups, and hydrocarbon distribution. In the presence of catalysts, an increase was observed in terms of desirable products such as phenol, alkene, and alkane, and a decrease in terms of undesirable products such as acids. Considering and evaluating all the results, the use of zeolite materials as catalysts in pyrolysis is a recommended option for obtaining enhanced chemicals and fuels.

Partial oxidation of dimethoxymethane to syngas over granular and structured Pt-based catalysts

The catalytic properties of supported Pt-containing catalysts for dimethoxymethane partial oxidation (DMM PO) into syngas was studied in a tubular fixed bed reactor at atmospheric pressure and relatively low temperatures (∼300–500 °C). Comparative studies of granular 0.5–1.9 wt % Pt/Ce0.75Zr0.25O2–δ and structured 0.08 wt% Pt/8 wt% Ce0.75Zr0.25O2–δ/6 wt% η-Al2O3/FeCrAl catalysts in DMM PO were performed. The SEM and STEM HAADF techniques were used for catalyst characterization. The structured catalyst was proved promising for producing syngas by the DMM PO reaction for SOFC feeding applications. In particular, at atmospheric pressure, temperature 400 °C, and the reaction mixture (28.6 vol% DMM, 14.3 vol% O2, 57.1 vol% N2) feed rate of 5 L/(g·h), this catalyst provided complete conversion of DMM and O2 to syngas with a total H2 and CO content of 69 vol% and syngas productivity of ∼8 L/(g · h).

Flexible operations of a multi-tubular reactor for methanol synthesis from biogas exploiting green hydrogen

The present modelling work studies the steady state and transient performances of a multi–tubular fixed bed reactor for methanol production from biogas. The modelled system comprises a methanol synthesis reactor, a flash unit, and accounts for the unconverted gas recycle. The novel concept herein proposed and assessed is the possibility to run a multi–tubular methanol synthesis reactor flexibly, i.e., using the carbon dioxide present in biogas, together with renewable H2, to increase methanol productivity, only when this is economically convenient. Accordingly, the methanol synthesis multi–tubular reactor under study is run in two operating conditions: when the cost of green hydrogen is high, the excess of CO2 present in biogas is vented and the reactor is fed with CO2-lean syngas only; conversely, in the presence of affordable renewable H2, CO2 and green H2 are cofed to the reactor. This study focuses in particular on the impacts of the two working conditions on the methanol productivity, as well as on temperature profiles and transient behaviour of the reactor. The effects of tube length and number are also simulated. The study shows that the multi–tubular reactor design well manages both operating conditions and that the steady-state conditions can be reached in a few hours after the switch from one condition to the other. In view of a small scale process, simulations show that it is better to reduce the tube number rather than their length, as the latter choice would lead to unacceptable temperature hotspots, due to a worsening of convective heat transfer.