Ethanol Conversion Research Articles

Production of Sugars and Ethanol from Acid–Alkaline-Pretreated Agave sisalana Residue

Drylands in Brazil have been exploring sisal (Agave sisalana) as an essential source of income. However, the solid residues generated because of this activity still need suitable destinations; therefore, research has been carried out to transform them into added-value products. Therefore, the present study evaluated the potential of sisal or agave solid residue as a precursor feedstock for second-generation ethanol production. Acid and acid–alkaline pretreatments were carried out on sisal residues to enrich the biomass with cellulose and maximize enzymatic digestibility. Second-generation ethanol production was carried out using Semi-simultaneous saccharification and fermentation (SSSF). Regardless of catalyst dosage and incubation time, oxalic acid pretreatments generated samples with a similar chemical composition to those pretreated with sulfuric acid. However, samples pretreated with oxalic acid showed lower enzymatic digestibility. Samples pretreated with oxalic acid and sodium hydroxide obtained 14.28 g/L of glucose and cellulose conversion of 79.1% (at 5% solids), while 21.49 g/L glucose and 91.2% of cellulose conversion were obtained in the hydrolysis of pretreated samples with sulfuric acid and sodium hydroxide combined pretreatments. The pretreatment sequence efficiently reduced cellulase dosage from 20 to 10 FPU/g without compromising sugar release. SSSF achieved maximum production of 40 g/L ethanol and 43% ethanol conversion using 30% solids and gradually adding biomass and cellulases.

Simultaneous construction of Zr-β zeolite with high content and high accessibility of framework Zr sites in the conversion of ethanol to 1,3-butadiene: Mechanisms and synergistic effects

Metallosilicate zeolites, represented by Zr-β zeolite, possess unique porosity and tunable acidity, showing great potential in the conversion of ethanol to 1,3-butadiene. However, there still remains potential for further improvement of catalytic activity and stability by breaking the bottleneck framework metal site content and microporosity diffusion. In this paper, a novel Zr-β zeolite with both high content and high accessibility of framework Zr sites was successfully synthesized via the combination strategy of “Improved Decomposition Reconstruction” and “Silanization.” Based on the activity evaluation experiments of key reaction steps and in situ DRIFTS in the conversion of ethanol to 1,3-butadiene, the enhanced activity and stability are due to the synergistic effects of the content and accessibility of framework Zr sites, which both facilitate reactant conversion and inhibit the covering of active sites or the plugging of pore channels by polymerized heavy compounds. The prepared zeolite demonstrates excellent performance with a total conversion of 66 % and a 1,3-butadiene selectivity above 67 % in 100 h, along with good regenerability.

Boron vs. aluminum in ZSM-5 zeolites: Solid-state NMR, acidity, and C1/C2 reactant conversion

Three zeolite catalysts with comparable amounts of aluminum and/or boron ([Al]ZSM-5, [B,Al]ZSM-5, and [B]ZSM-5) are herein synthesized. Water (H2O), ammonia (NH3), acetonitrile-d3 (ACN), and trimethylphosphine oxide (TMPO) are applied as probe molecules to investigate the acidity of the respective materials in combination with 11B, 27Al, and 29Si MAS NMR spectroscopy. Ammonia is not protonated to ammonium on Si(OH)B groups and only LAS-bound ammonia persists desorption. Thus, ammonia gives a realistic, quantitative picture of the present acid sites. ACN interacts only with Si(OH)Al as desired. The strong base TMPO results in a misleading, not quantifiable picture. Subsequent hydration is unsuited to distinguish BAS and LAS densities. The samples were catalytically tested in the conversion of methanol, ethanol, and ethylene. [B]ZSM-5 is unreactive in hydrocarbon formation due to absence of BAS, instead LAS are present. The mixed [B,Al]ZSM-5 shows a decreased lifetime in MTO conversion compared to the [Al]ZSM-5, due to LAS presence. A sometimes reported superior reactivity of [B,Al]ZSM-5 catalysts is thus explained primarily by an optimized BAS density.

Ethanol steam reforming for hydrogen production over cobalt catalyst supported on the cerium oxide prepared via the one-step hard template method

This study describes a cobalt catalyst supported on highly porous cerium oxide beads (CeO2-XAD) prepared via the one-step hard template method (using resin Amberlite® XAD7HP as a template) for catalytic steam reforming of ethanol (SRE) for hydrogen production. For comparative purposes, Co catalyst supported on a commercial CeO2 is discussed (Co/CeO2-COM). Comprehensive studies, including TEM, XPS and H2-TPR analysis, reveal that the bare CeO2-XAD consists of tiny particles with highly damaged surfaces, which contain various forms of oxygen. The hierarchical structure of the support beads, fixed after calcination, ensures high mesoporosity favouring the formation of small, evenly dispersed Co3O4 crystallites on CeO2-XAD (∼3 times smaller than in Co/CeO2-COM), which then, after reduction, transformed into fine, homogenously dispersed Co particles that strongly interact with the support. Consequently, the Co catalyst supported on CeO2-XAD exhibits high catalytic activity in SRE (much higher than Co/CeO2-COM). Although both catalysts deactivate during SRE due to carbon deposition the process is less severe for the catalyst with smaller Co crystallites and nanostructured support. This study reveals the huge role played by the appropriate morphology and nanostructure of the catalyst support in SRE since they affect not only the ethanol conversion efficiency but also increase the selectivity of the process and thus limit the deactivation of the catalyst.

Effects of adding metals to Beta zeolite on ethanol conversion to hydrocarbons

This study investigated the effects of Beta zeolite ion exchange with Fe, Zn, and Co on ethanol conversion to hydrocarbons. Various characterization techniques such as X-ray fluorescence (XRF), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), magic angle rotation nuclear magnetic resonance spectrometry (MAS NMR) of 29Si and 27Al, scanning electron microscopy (SEM), nitrogen physisorption, ammonia temperature-programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR) were employed. Catalytic tests were performed at temperatures from 475 to 550 °C under ambient pressure. The metal addition to Beta zeolite reduced micropore area and volume, decreased the concentration of the extra-framework aluminum, and increased total acid site density and Lewis acid sites, except for Fe. For all catalysts, ethylene was identified as the primary product. However, catalysts containing Zn and Co displayed the formation of propylene and C1 to C3 paraffins. The catalyst with Fe exhibited the highest deactivation and a significant decrease in acidity, attributed to the formation of extra-framework aluminum, resulting in exclusive ethylene production.

Sorption-enhanced ethanol steam reforming coupled with in-situ CO2 capture and conversion

The impacts of climate change and the issue of greenhouse gas emissions have sparked research into renewable energy alternatives to fossil fuels. Hydrogen has gained attention as a clean, renewable and environmentally friendly energy source. Enhanced-ethanol steam reforming has been proposed as a promising method for blue hydrogen production, addressing greenhouse gas emission issues. The use of catalysts enhances the adsorption of ethanol and water molecules on the surface, promoting the reaction rate. This study systematically explored the effects of different Fe loading and CaO addition ratios on the ethanol steam reforming and CO2 conversion processes to optimize catalyst performance. The experimental results showed that Fe/SiC catalysts effectively promoted the conversion of ethanol and generated high-purity hydrogen, exhibiting excellent catalytic activity. Specifically, a catalyst with 10 % Fe loading and mixed with 0.3g CaO significantly increased the hydrogen yield to 64.4 mmol/g, which was 2.88 times higher than that without the catalyst.

Advanced Statistical Optimization for Enhanced Medium-Chain Fatty Acid Production

In recent years, the development of feed ingredients with natural additives has gained significant importance in increasing the health and quality of animal products, as well as in promoting weight gain in animals. Since Salmonella infection is a significant disease that transmits from animals to humans, the inhibition of Salmonella species can be achieved particularly through the improvement of gastrointestinal metabolism in chickens. At this point, the effectiveness of using MCFA (Medium Chain Fatty Acids) as a feed additive has been proven. MCFA are composed of a mixture of various fatty acids, including acetic acid, butyric acid, hexanoic acid, etc. Highest portion of MCFA are hexanoic acid. Besides feed additives hexanoic acid play a crucial role as primary resources in various industries, including the chemical, food, agricultural, and biofuel sectors. It is typically obtained from petrochemical-based solutions but there has been a growing focus on biotechnological production and natural sources in recent years. One of the mostly known bioprocess to produce MCFA is chain elongation (conversion of acetate and ethanol into MCFA by β oxidation reaction) by Clostridium kluyveri. However, as in most biotechnological processes, there are low yields and high costs in these reactions as well. In this study, Box-Behnken Design, a statistical experimental design method, was used to optimize the concentrations of acetate, ethanol (the two primary components of chain elongation reactions) and pH for MCFA production via chain elongation reactions with Clostridium kluyveri. Batch experiments were performed at 30°C and 37°C to also see the effect of temperature. Higher values of hexanoic acid and bacterial growth were observed at 37°C. From an economic perspective, a 14% reduction in costs has been observed with optimized components.

Cu/MgO as an Efficient New Catalyst for the Non-Oxidative Dehydrogenation of Ethanol into Acetaldehyde

The non-oxidative dehydrogenation of ethanol into acetaldehyde is one of the efficient solutions for biomass upgrading. In this work, a series of copper catalysts supported on MgO with different Cu loadings ranging from 2.5% to 20% were prepared by an impregnation method. The as-synthesized Cu/MgO catalysts were characterized by N2 adsorption, XRD, TEM, CO2-TPD, XPS and TPR. These catalysts were found to be effective for ethanol dehydrogenation into acetaldehyde. As the Cu loading was increased, the ethanol conversion first increased and then leveled off. At a WHSV of 1.5 h−1 and 250 °C, the 20%Cu/MgO catalyst gave an initial conversion of 81.5%, with 97.7% selectivity toward acetaldehyde. Compared to 20%Cu/SiO2, the 20%Cu/MgO catalyst displayed an equivalent initial acetaldehyde yield, higher acetaldehyde selectivity and longer stability.

Enhancing bioethanol conversion from straw by a novel circulation promotion method

Crop straw, an inedible and abundant agricultural by-product, can be used for bioethanol production. However, ethanol conversion from straw is a series of complex processes and has encountered issues, which cause considerable restriction to the production of straw ethanol. Herein, the bioethanol conversion process was innovated. Ethanol as a reverse osmosis membrane accelerant was investigated to enhance the removal of inhibitors to increase ethanol production during conversion process. The results indicated that membrane accelerant used here could reduce the inhibitor retentions by 39.3 %–69.2 %. Then, an original innovation integrated method for the whole process of straw ethanol conversion was developed. The integrated method could increase 26.8 % the production of straw ethanol compared to the membrane process without an accelerant. A preliminary cost accounting indicated that the integrated method was economically feasible when total ethanol output exceeded 14000 kg. This study represents for the first time a circulation promotion method based on the whole process of straw ethanol conversion. The results showed that the integrated method was capable of effective conversion of straw ethanol.

Ethanol conversion to hydrocarbons over Sn-doped H-ZSM-5 zeolite catalysts

Sn-based zeolite have been prepared by incipient wetness impregnation by studying the role of the starting precursor either Sn(II) or Sn(IV) chlorides. Catalysts have been deeply characterized through XRD, FT-IR, UV–vis-NIR, SEM-EDXS, FE-SEM-EDXS, and IR of probe molecules i.e., pyridine and CO, by also investigating the reaction at the surface in static conditions. As well catalytic activity has been carried out by investigating the role of GHSV that has been varied between 2700 and 8500 h−1, obtaining linear variation of product distribution as a function of contact time. Small amounts of Sn improve the catalytic activity of H-ZSM-5 zeolite in converting ethanol to higher hydrocarbons. In particular, the addition of Sn4+ ions increases the conversion of ethanol to C6–C8 aromatic hydrocarbons up to a very interesting 34 % selectivity at 100 % ethanol conversion. In fact, bioethanol conversion over Sn–H-ZSM-5 zeolite represents a potentially interesting way to produce a high-octane biogasoline, as well as aromatic (BTX) cut useful as a renewable intermediate in future biorefinery-derived processes. It is proposed that ethylene, the main product, is the key intermediate in the acid-catalyzed route, and Sn-ions are favoring the cyclization and dehydrogenation of ethylene-derived oligomers.

Microbial biomass production from enzymatically saccharified organic municipal waste and present microbial inhibitors

AbstractThe study investigated the potential of the organic fraction of municipal solid waste (OFMSW) for microbial biomass production. The compositional analysis of OFMSW showed richness in sugars, proteins, lipids, organic acids, and ethanol, suggesting promising cheap cultivation feedstock if inhibitory compounds are sustainably detoxified. The enzymatic hydrolysis with Cellic® CTec3 and AMG® 300 L BrewQ (Novozymes A/S) demonstrated excellent saccharification of sugar polymer, reaching 92% glucan hydrolysis and 70% xylan hydrolysis. However, higher enzymatic dosages led to a rise in the total organic acids content, potentially causing increased microbial inhibition. Full hydrolysate and hydrolysate after solids removal were cultivated with seven robust microbial strains. Cultivation on hydrolysate with solids showed consumption of sugars and organic acids solely by commercial backer yeast Saccharomyces cerevisiae. Removal of solids from hydrolysate resulted in increased performance of tested strains, showing consumption of measured organic acids and ethanol by S. cerevisiae, Yarrowia lipolytica DSM 8218, and Cutaneotrichosporon oleaginosus ATCC 20509. Remarkably, the investigation of biomass production revealed superior cell mass formation and detoxification by S. cerevisiae, resulting in 18.9 g of biomass/L hydrolysate with 50% of crude protein (w/w) in shake flasks and 13.2 g/L of hydrolase with 46% of crude protein (w/w) in a 5-L bioreactor. Furthermore, bioreactor cultivation confirmed organic acids and ethanol conversion into biomass, highlighting S. cerevisiae’s suitability for utilizing OFMSW for microbial biomass production. These findings contribute to advancements in biowaste-to-fodder conversion, promoting the development of a more sustainable circular economy. Graphical abstract

Technoeconomic feasibility of producing clean fuels from waste plastics: A novel process model

Plastic waste is a problematic issue impacting the environment and human health. A proper recycling of plastics to valuable products is highly needed to meet the increase in energy demand. Plastics have high heating value; therefore, the thermochemical recycling of plastic waste is a valid and feasible approach. Recently, ethanol has attracted wide applications such as the conversion of ethanol to olefins, and hydrocarbons. It burns completely and cleanly, where it reduces the emissions of greenhouses compared to the usual fuels. Hydrogen and other higher hydrocarbons are also crucial in meeting the energy demand. In this study, the plastic waste, mainly polyethylene and polypropylene (due to their availability) were gasified using steam gasification process to produce syngas which then was further processed to hydrogen, ethanol, and other valuable liquid hydrocarbons. An alternative design is constructed integrating steam methane reforming (SMR) with plastic gasification to utilize the heat at the outlet of the gasifier and to enhance the syngas heating value. The two models were compared in terms of syngas heating value, energy analysis and economic analysis. The main parameters that have been evaluated are the production rate of fuel per total feedstock, total required heat, overall process efficiency, and fuel levelized production cost. The results indicated that Case 2 generates syngas with a higher heating value of 55 %, produces four times more H2, and comparable amount of ethanol and other fuels than Case 1. The analysis also revealed that Case 2 has a process efficiency that is 3 % better and a 37.5 % lower fuel production cost than Case 1. Overall, the design of Case 2 was found to be more efficient and cost-effective than the Case 1 design.

Efficient conversion of ethanol to acetaldehyde with induction heating at low temperature

The application of induction heating (IH) to provide heat for chemical reactions has received great attention due to its potential to electrify chemical reactions. Biomass-based production of acetaldehyde from ethanol has gained rising interest since it provides an alternative sustainable method instead of the fossil-fuel-based output using acetylene and formaldehyde in the presence of a catalyst. The dehydrogenation of ethanol can be catalyzed by supported copper catalysts. The reaction is typically carried out at high temperatures, around 250–300 °C, without oxygen. The resulting product mixture usually contains acetaldehyde, as well as other byproducts such as ethylene and hydrogen gas. The acetaldehyde can be separated from the other components using distillation or other separation techniques. In this work, we studied the catalyst activity with IH for the first time and achieved high ethanol conversion and acetaldehyde selectivity at a temperature of 30 ˚C lower than that with conventional furnace heating (CFH). A transport model was applied to design the catalyst bed configuration and improve the catalyst activity, stability, and energy efficiency by minimizing the temperature gradient. Our work suggests that the temperature distribution and the fast compensation of heat loss through IH are critical for the catalyst behavior. Both high production efficiency and energy efficiency can be achieved with IH, such that it can be an efficient and environment-friendly heating method for the chemical industry.

Design of dual-channel Swiss-roll reactor for high-performance hydrogen production from ethanol steam reforming through waste heat valorization

Steam reforming is one of the most economical and efficient methods for hydrogen production. However, one of its glaring issues is the heat supply, which is used to maintain the reactions. Among reactors for hydrogen production, Swiss-roll reactors have exhibited exceptional performance in sustaining the heat required for reactions. Furthermore, heat supply via waste heat recovery has been an attractive industrial prospect for improving the sustainability of hydrogen production. This study proposes a design of a novel Swiss-roll reactor with dual channels to harvest waste heat from the flue gas to sustain the steam reforming reactions. Ethanol is used as a feedstock due to its environmentally benign properties. Numerical simulations are conducted to establish the reactor's catalytic reactions and heat transfer phenomena under the variations of gas hourly space velocity (GHSV), steam-to-ethanol (S/E) ratio, and inlet flue gas temperature. Heat recovery improves at higher GHSVs and lower S/E ratios at the cost of less efficient hydrogen production, while high inlet flue gas temperature improves heat recovery and hydrogen production. The novel reactor design can fulfill complete ethanol conversion maintained by heat recovered from waste flue gas, achieving 86.6 % hydrogen production efficiency and 72.7 % heat recovery under optimal operating conditions.

Utilization of non-concentrated banana pseudostem sap waste for converting to bioethanol: In vitro and in silico evidence

The abundantly available waste banana pseudostem fibers have attracted the paper and textile industries, however the stem-sap extracted during fiber processing remains underutilized. Although this sap comprising cellulosic sugars holds potential as a feedstock, its commercial viability in the renewable energy sector remains a challenge. Our study delves into this untapped resource by mechanically extracting sap from banana pseudostems and enhancing its reducing sugar content to approximately 35.5 g/L through acid hydrolysis and detoxification without concentrating the sap. Using separate batch fermentations with pentose and hexose fermenting strains such as Pichia stipitis NCIM 3499 and Saccharomyces cerevisiae ATCC 2601, we achieved bioethanol production efficiencies of 67.5 % and 70.03 %, respectively. Yield and cost analyses confirmed the feasibility of this approach for industrial application in low-economy settings. Furthermore, gene-interaction network and functional enrichment analysis identified 63 key genes involved in carbohydrate metabolism and ethanol conversion pathways within the fermenting organisms. Among these, the PGK1 gene and its direct interactors emerged as promising targets for future biotechnological enhancements aimed at boosting bioethanol production. This study not only underscores the renewable energy potential of unconcentrated banana pseudostem sap but also paves the way for innovative genetic interventions to optimize bioethanol yields.

3D simulation in a fixed bed coupled pervaporation reactor for biodiesel production

In this study, a solid acid catalyst SO42−/TiO2/ZSM-5 (STZ) was prepared. Biodiesel was synthesized from tall oil fatty acid (TOFA) by the ethanol esterification. The fixed bed and pervaporation (PV) coupling increased the esterification conversion of TOFA and ethanol by about 16 %. The spherical STZ catalyst’s appearance, composition, and catalytic activity were assessed through TGA, XRD, SEM, BET, FTIR, NH3-TPD and XPS analyses. The reaction parameters of ethanol/TOFA molar ratio (10:1–20:1), reaction temperature (75–85 ℃), catalyst dosage (6–12 g) and flow rate (0.3–0.9 mL/min) were optimized by the response surface method (RSM). Under RSM optimization, the TOFA esterification reaction achieved a conversion rate of 99.56 ± 0.23 %. After five cycles of esterification, TOFA conversion remained above 87 %. A computational fluid dynamics (CFD) model was established to predict the esterification reaction behavior in the reactor, and the TOFA conversion rate was found to be close to the experimental results through systematic simulation, by reaction kinetics equation, continuity equation, Navier-Stokes equation, and Brinkman equation. In addition, the TOFA biodiesel prepared by this study complies with EN 14214 and ASTM D6751 standards.

A Study of the Effects of K-Modification and (Co, Ni, Fe)-Promotion on a Supported MoS2-Based Catalyst for Ethanol Conversion

A Study of the Effects of K-Modification and (Co, Ni, Fe)-Promotion on a Supported MoS₂-Based Catalyst for Ethanol Conversion

Photothermal dry reforming of ethanol over rod-like Ni/ZrO2 catalysts

Photo-assisted ethanol dry reforming (EDR) for syngas production was deeply studied over nanorod-like Ni/ZrO2 catalyst synthesized by precipitation and impregnation technique, respectively. The effect of light irradiation as well as catalyst preparation method on EDR reaction was investigated in detail with the stoichiometric feed ratios, over a temperature region of 350 to 550 °C. Photo-enhancement factor of ethanol conversion greatly increased from 10% (dark) to 40% (light) together with less formation of byproducts. Moreover, the experimental results depicted the better performance of P-Ni/ZrO2 catalyst due to its abundant oxygen vacancies and strong Ni-Zr interaction. Enriched interfacial oxygen defects and more light-excited electrons facilitated the activation/dissociation of ethanol and CO2, thereby enhancing the catalytic activity. In addition, the mean particle size of NiO in P-Ni/ZrO2 was (10.3 nm) which was smaller than that of the I-Ni/ZrO2 (16.5 nm), suggesting its higher dispersion of active metal. The calculated apparent activation energy of P-Ni/ZrO2 was 20.6 eV which was much less than the value of I-Ni/ZrO2 (37.7 eV). This work might provide the valuable insight for the development of highly-efficient photothermal catalyst to enhance the value-added utilization of greenhouse gas CO2.

Preparation and catalytic evaluation of phosphated zirconia nanopowder for ethanol dehydration into diethyl ether

Research on renewable energy development is intensified nowadays, including the production of diethyl ether (DEE) as a high-value alternative fuel. This study explored the catalytic conversion of ethanol into diethyl ether using a phosphated zirconia catalyst. We examined different concentrations of phosphoric acid (1, 2, 3, and 4 M) and calcination temperatures (400, 500, and 600 °C) applied to zirconia nanopowder to evaluate their influence on the acidity of the resulting phosphated zirconia. The catalysts were characterized by FTIR, XRD, SAA, SEM-EDX Mapping, and TG-DTA. Among the catalysts tested, the PZ-2-400 catalyst, prepared with a 2 M H3PO4 concentration and calcined at 400 °C, exhibited the highest acidity value of 0.56 g/mol pyridine. When operated at the optimum temperature of 225 °C, this catalyst achieved an ethanol conversion of 80.04 % and a diethyl ether yield of 1.00 %. These findings suggest that modification of ZrO2 with phosphoric acid acts as a solid acid catalyst for diethyl ether synthesis with better activity and selectivity than unmodified ZrO2.

THE ROLE OF Zn-Fe CATALYSTS IN THE REACTION OF ETHANOL CONVERSION TO ACETONE

Recently, processes for obtaining various organic compounds from ethanol, which is derived from the processing of plant raw materials, have become highly relevant. Acetone is a valuable monomer that can be obtained from ethanol. It has been previously demonstrated that catalysts based on zinc oxides exhibit high activity in the conversion of ethanol to acetone. A review of the literature has shown that catalysts based on iron oxides also demonstrate high activity in this reaction. Therefore, the aim of this work was to study the vapor-phase conversion of ethanol to acetone on various binary zinc-iron oxide catalysts. This article describes a process for studying the paraphase conversion of ethanol to acetone on zinc-iron oxide catalysts Zinc-iron oxide catalysts of various compositions have been synthesized. The activity of the obtained catalysts was studied in the reaction of ethanol conversion. It was shown that samples rich in zinc oxide exhibit the greatest activity in the studied reaction. It has been established that the yield of acetone on the best catalysts reaches its maximum yield. The zinc-iron oxide catalyst of composition 9:1 showed the highest activity. catalyst, the maximum yield of acetone reaches up to 80%. Keywords: catalyst, ethanol, acetone, zinc, iron, vapor-phase conversion, iron oxides, temperature, reaction rate.