Presence Of Solid Acid Catalysts Research Articles

Conversion of Biomass-Derived Molecules into Alkyl Levulinates Using Heterogeneous Catalysts

Alkyl levulinates are promising and versatile biomass-derived chemicals, which are utilized as fuel additives, flavoring agents, fragrances, solvents, and precursors for synthesizing valuable γ-valerolactone. A method for synthesizing alkyl levulinates involves the esterification of levulinic acid with the corresponding alkyl alcohols in the presence of solid acid catalysts that have abundant Brønsted acid sites. Alkyl levulinates can also be synthesized from other biomass-derived molecules such as furfuryl alcohol and furfural via alcoholysis and one-pot conversion, respectively. Thus far, various heterogeneous catalysts have been developed for the conversion of the biomass-derived molecules (levulinic acid, furfuryl alcohol, and furfural) into alkyl levulinates. To obtain the target products in high yields, numerous strategies have been employed including increasing Brønsted acidity, dispersing and incorporating Brønsted acid sites, inducing the formation of mesopores, and inducing a synergistic effect of metal–Brønsted acid sites that are present on a catalyst surface. Here, we summarily reviewed the performances of the heterogeneous catalysts in the conversions, describing the design and development of the heterogeneous catalysts that ensured the excellent yield of alkyl levulinates.

A non-conventional sustainable process route via methyl acetate esterification for glycerol-free biodiesel production from palm oil industry wastes

In the present study, a sustainable and environmentally safe process was utilized for production of biodiesel free of glycerol via methyl acetate esterification by employing the beneficial usage of palm oil industrial waste products. A non-conventional novel approach was then investigated for the esterification process using methyl acetate as the esterifying agent in the presence of solid acid catalyst prepared via impregnation on spent bleaching earth as catalyst support. The new solid acid catalyst was synthesized by calcination and sulfonation of the spent bleaching earth. The catalyst was characterized via Hammett Indicator, X-ray Fluorescence, Thermogravimetric Analysis, X-ray Diffraction, Nitrogen adsorption-desorption analysis, and Ammonia-temperature programmed desorption techniques. Optimization study was carried out for reaction parameters such as reaction temperature (60–110 °C), catalyst amount (2–14 %), PFAD/MA molar ratio (1:3–1:18) and reaction time (1–6 h). The maximum free fatty acid conversion of 89.89 % was obtained at optimized reaction conditions: catalyst amount 12 w/w%, reaction time 3 h, reaction temperature 100 °C and PFAD/MA molar ratio 1:12. A plausible mechanism for the esterification of palm fatty acid distillate using methyl acetate in the presence of the synthesized acid catalyst has also been proposed. This study also ascertained the effectiveness of methyl acetate as a suitable alternative esterifying agent for esterification of palm fatty acid distillate.

Fluoride-treated IM-5 zeolite as a highly active catalyst for the production of jet fuels by the oligomerization of 1-hexene

Light alkenes oligomerization, performed in the presence of solid acid catalysts, is an important alternative for the production of clean jet fuels. For 1-hexene oligomerization, the current catalyst often suffers from low activity and selectivity. The developed process is upgraded by zeolite catalyst, targeting high-concentration of jet-range hydrocarbons. An efficient and selective IM-5 zeolite-derived catalytic system has been developed for the oligomerization of 1-hexene. The treatment in an aqueous NH4F solution led to dealumination without structure degradation. The IM-5 zeolite with a unique two-dimensional IMF structure and 2.5 nm nanoslab showed rapid diffusion ability than ZSM-5 zeolite. Enhance acidities were observed in the NH4F-treated IM-5 zeolites owing to fluoride residue and the removal of Al atoms. The strong Brønsted acid sites exerted a positive effect on both the cracking and the oligomerization reactions with the increasing of the yields of dimers. The contact time and partial pressure between the 1-hexene and the IM-5 zeolites were used to analyze the competition of cracking reactions. High 1-hexene conversion (62%), optimal oligomerization to C3-C5 ratio (O/C = 32), and reasonable stability were obtained over the etched IM-5 catalyst at 240 °C, 4 MPa, and the flow rate of N2 was 50 mL/min.

Biomass hydrolysis with phosphotungstic acid

In this study, the effect of phosphotungstic acid on the biomass hydrolysis was investigated. Hydrolysis experiments were carried out in four different concentration ranges (1–4%) and at two different temperatures (200 and 250 °C) in the batch reactor. Biomass hydrolysis was investigated by determining the total organic carbon content and polysaccharides average molecular weights of hydrolysates. The hydrolysis efficiency and total organic carbon content increased with increasing phosphotungstic acid percentage, while polysaccharides average molecular weights were decreased at 200 °C.Increase of temperature in the presence of solid acid catalyst caused a significant increase on the biomass hydrolysis percentage.

Recovery of pentoses-containing olive stones for their conversion into furfural in the presence of solid acid catalysts

Olive stones were employed as feedstock for furfural production in two stages: 1) autohydrolysis of hemicellulosic fraction to recover their pentoses, mainly xylose, and 2) subsequent dehydration of pentoses into furfural. Autohydrolysis step was optimized by using different experimental conditions (temperature: 160−200 °C and time: 30−75 min), giving rise to liquors with different xylose concentrations, since hydrolysis was incomplete in some cases. The combined use of a commercial γ-Al2O3 and CaCl2 led to total hydrolysis of non-hydrolyzed pentosans after autohydrolysis step, and the subsequent dehydration of pentoses into furfural. The maximum values of furfural yield and efficiency were 23 and 96 %, respectively, after only 60 min at 150 °C by using liquor obtained by autohydrolysis at 180 °C and 30 min (L5.1) as source of pentoses. This liquor, L5.1, provided better catalytic results than other liquors which had shown higher xylose concentration after autohydrolysis, probably due to these latter also exhibited a higher concentration of organic acids; thus, the presence of organic acids, such as acetic and lactic acids, could promote undesired reactions leading to lower furfural yields. Finally, γ-Al2O3 was more effective for furfural production under these experimental conditions than other solid acid catalysts, such as mesoporous Nb2O5, Nb-doped SBA-15 and Zr-doped HMS silicas, probably due to alumina has a higher density of acid sites.

Pyrolysis of the Cellulose Fraction of Biomass in the Presence of Solid Acid Catalysts: An Operando Spectroscopy and Theoretical Investigation

Biomass pyrolysis by solid acid catalysts is one of many promising technologies for sustainable production of hydrocarbon liquid fuels and value-added chemicals, but these complex chemical transformations are still poorly understood. A series of well-defined model SiO2 -supported alumina catalysts were synthesized and molecularly characterized, under dehydrated conditions and during biomass pyrolysis, with the aim of establishing fundamental catalyst structure-activity/selectivity relationships. The nature and corresponding acidity of the supported AlOx nanostructures on SiO2 were determined with 27 Al/1 H NMR and IR spectroscopy of chemisorbed CO, and DFT calculations. Operando time-resolved IR-Raman-MS spectroscopy studies revealed the molecular transformations taking place during biomass pyrolysis. The molecular transformations during biomass pyrolysis depended on both the domain size of the AlOx cluster and molecular nature of the biomass feedstock. These new insights allowed the establishment of fundamental structure-activity/selectivity relationships during biomass pyrolysis.

Cutting the Green Waste. Structure‐Performance Relationship in Functionalized Carbon Xerogels for Hydrolysis of Cellobiose

AbstractThe hydrolysis of cellulose and hemicelluloses in the presence of solid acid catalysts is of great importance as an entry process for the production of biofuels and chemicals. In this work, the effect of carbon surface chemistry on the catalyst conversion and selectivity in hydrolysis of cellobiose to glucose was studied. Solid catalysts based on carbon xerogels (CXs) containing various functionalities incorporating heteroatoms (S, P, N, O), as confirmed by XPS, TPD, ICP and EA analyses, were successfully prepared. CXs containing 3.4 wt % of phosphorus showed the best catalytic performance, reaching 90 % conversion of cellobiose with 72 % selectivity to glucose, under oxidative atmosphere and in a short reaction time of only 4 h. The presence of phosphonates (−P−C−) was found to increase the selectivity to glucose up to unprecedented 87 %. On the contrary, carbonyls, quinones, pyrydinic, pyrrolic and sulfonic groups were found to promote glucose degradation, leading to a final low yield of this product. Additionally, the increased concentration of oxygen in the reaction atmosphere was shown to significantly weaken the β (1–4)‐glycosidic bond, increasing the final yield of glucose.

Solid acid catalyst supported synthesis and fuel properties of ethyl decanoate

Decanoic acid, found in naturally occurring coconut and palm kernel oils, and in genetically modified cuphea plant species, is gaining increasing importance as platform chemical for the development of many useful products. Although perceived to be an important starting molecule for production of biodiesel, the process of production of and fuel properties of its ethyl ester have never been explored before. In this article, we have reported about laboratory-based studies for esterification of decanoic acid with ethanol in presence of solid acid catalysts. Activation energy of the esterification reaction was found to be 38.5 KJ/mol. The studies showed that the conversion of decanoic acid to its ethyl ester can be performed at optimal temperature 348 K in presence of solid acid catalyst. We have also investigated salient fuel properties of ethyl decanoate and its several blends with conventional fossil-derived diesel and found that use of ethyl decanoate with conventional diesel could become economically attractive.

Synthesis of Biolubricant Basestocks from Epoxidized Soybean Oil

This work deals with the preparation of biolubricant basestocks through the ring-opening reaction of epoxidized soybean oil (ESO) by alcohols in presence of solid acid catalysts (SAC-13 resin). To this end, different experimental runs were carried out in a lab-scale reactor, analyzing the effect of the alcohol (methanol, ethanol, 2-propanol, 2-butanol), catalyst mass loading (from 1 to 10 wt % with respect to the oil mass) and operating temperature (60–90 °C). The main focus of investigation was oxirane conversion. The study was complemented by FT-IR, 1H NMR and kinematic viscosity characterization of the different products of the ring-opening reaction. Experimental conversion data were fitted through a suitable kinetic model. Values of the best-fitting parameters in terms of rate constant, activation energy and catalyst reaction order were obtained, and were potentially useful for the design of an industrial process.

Biodiesel production in a continuous packed bed reactor with recycle: A modeling approach for an esterification system

The aim of this work is to propose and to validate a dynamical model for an esterification reaction that was carried out in a relatively new configuration for biodiesel production process: a packed bed reactor with input, output, and recycle. More specifically, the reagents of the esterification process were free fatty acids (FFA) contained in canola oil and low cost methanol (LCM), whereas a commercial cation exchange resin (Purolite CT725) was used as a solid-acid catalyst. The effects of both the LCM volumetric inflow rate and the inflow FFA molar fraction were investigated. The dynamical model was built considering the following assumptions: 1) the reactor was modeled as a CSTR due to the high ratio of recycling volumetric flow to reactor volumetric inflow and 2) the kinetic expression in the model is written in terms of activity coefficients in the light of the non-ideal behavior of the esterification reaction. A satisfactory agreement between the experimental data and the proposed model was obtained. Thus, the resulting model may be advised as a valuable tool for the analysis, control, and optimization of continuous packed bed reactors where the esterification of FFA in the presence of solid acid catalyst is carried out to produce biodiesel.

Facile, One-Pot, Two-Step, Strategy for the Production of Potential Bio-Diesel Candidates from Fructose

The production of bio-diesel fuels from carbohydrates is a promising alternative to fossil fuels with regard to the growing severity of the environmental problem and energy crisis. Potential bio-diesel candidates or additives, such as 5-(hydroxymethyl)-2-(dimethoxymethyl) furan (HDMF), 2-(dimethoxymethyl)-5-(methoxymethyl) furan (DMMF), and 5-(methoxymethyl)-2-furaldehyde (MMF) could be produced from the alcoholic solutions of both 5-HMF and fructose in the presence of solid acid catalysts. In the present study, a readily prepared, silica, gel-supported nitric acid (SiO2-HNO3) catalyst was found to be exceptionally reactive for the production of HDMF from fructose. A DMSO-methanol biphasic solvent system was developed and HDMF, DMMF, and MMF were observed at 150 °C, with maximum yields of 34%, 34%, and 25%, respectively. Meanwhile, a maximum HDMF yield of 77% was obtained from 5-HMF in methanol. Moreover, a sequential, one-pot, two-step dehydration/acetalization process, involving the dehydration of fructose to 5-HMF in dimethylsulfoxide (DMSO) at 150 °C, and followed by adding a certain amount of methanol to react with the formed 5-HMF to HDMF at 100 °C, was developed to promote the yield of HDMF. The optimum yield of HDMF reached 70% with the complete conversion of fructose. The reaction mechanisms of dehydration and acetalization have been proposed for the conversion of 5-HMF to HDMF. The two-step design allows for facile catalyst recycling while supplying as a promising method for the production of biodiesel from complex carbohydrates.

Solid Acid Catalysts: New Routes to Food Additives and Antibacterials

Mixture of mono- and di-glycerides can be obtained in the presence of solid acid catalysts starting from fatty acids and even in one single step starting from a residue of the edible oil industry, namely a mixture of free fatty acids and triglycerides. This is due to the Lewis acidity of amorphous solid catalysts promoting both the esterification of fatty acids and the transesterification of triglycerides. Selectivity to monoglycerides can be very high particularly in the case of butyric acid ones, useful as antibacterial and antiviral agents.

Dehydration of Xylose to Furfural in Alcohol Media in the Presence of Solid Acid Catalysts

AbstractDifferent solid acid catalysts, which include several zeolites, zirconium oxide based catalysts, and materials that contain sulfonic acids, have been evaluated in the dehydration of xylose to furfural in alcohol media. Alcohol media were selected to reduce side reactions, many of which occur in aqueous media. Among the tested alcohols, 2‐propanol provided better results and yielded a higher furfural production than ethanol and methanol. Catalyst screening evidenced that small‐pore‐size zeolites (H‐ZSM5) or catalysts that show weak acidity (tungstated zirconia) were unable to promote the desired transformation. Kinetic studies performed for the different types of materials revealed that the nature of the acid sites influenced the catalytic performance of the different solid acids to the extent of conditioning the main reaction pathway for the transformation of xylose into furfural. Thus, whereas Lewis acids seem to promote furfural production by the direct dehydration of xylose, Brønsted‐type catalysts lead to alkyl xylosides as intermediates in the overall transformation. Although both types of catalysts provide high furfural yields in short reaction times, especially at high temperatures, commercially available β‐zeolite with an adequate combination of Brønsted and Lewis acids sites seems to contain the right physicochemical properties to maximize furfural production.

Catalytic reaction of diethyl disulfide with methanol

Diethyl disulfide reacted with methanol in the presence of solid acid catalysts at 250–350°C to give dimethyl, ethyl methyl, and diethyl sulfides. The most active catalysts were those containing simultaneously moderate basic sites, strong Lewis acid sites, and some amount of strong protonic acid sites. These catalysts ensured a total selectivity of 99% for dialkyl sulfides.

Lignin conversion in supercritical ethanol in the presence of solid acid catalysts

The effects of sulfated ZrO2 and ZrO2-Al2O3 catalysts and acidic zeolite catalysts with various Si/Al ratios on the thermal conversion of alkali lignin in supercritical ethanol at 300–400°C and on the composition of the resulting products have been investigated. All of the catalysts enhance lignin conversion into liquid products. The strongest effect with the catalysts based on sulfated ZrO2 is attained at 400°C; with the zeolites, at 350°C. The catalysts diminish the concentration of phenol and its derivatives and increase the concentration of ethers (mainly the 1,1-diethoxyethane concentration) in the liquid products. The zeolite catalysts are preferable, since the reaction over the ZrO2-containing catalysts produces gaseous compounds in higher yields. The maximum lignin conversion and a high yield of low-boiling liquid products are achieved at 350°C with the zeolite catalyst with Si/Al = 30, which contains a high concentration of acid sites that are stable at elevated temperatures. The most abundant phenolic liquid products of lignin conversion over the zeolite catalysts at 350°C are methoxyphenols and their methylated and ethylated derivatives.

Synthesis and properties of trimethylolpropane trioleate as lubricating base oil

AbstractTrimethylolpropane trioleate (TMPTO) has been prepared by esterification of oleic acid with trimethylolpropane (TMP) without solvent in the presence of solid acid catalyst. The synthesised TMPTO was characterised by infrared spectroscopy, and its physicochemical properties were also evaluated. The compatibilities of TMPTO as lubricant base stock with several conventional additives for mineral oils were investigated. The results showed that the synthesised TMPTO exhibited excellent viscosity–temperature property and low temperature fluidity, high flash point, good foaming stability, hydrolytic stability, and lubricity. In addition, TMPTO possessed good compatibility with conventional additives designed for mineral oils. In particular, zinc dialkyl dithiophosphates as extreme pressure and anti‐wear additive exhibited good extreme pressure and anti‐wear properties in TMPTO. Therefore, the synthesised TMPTO can be used as potential lubricating base oil due to its excellent comprehensive performance. Copyright © 2014 John Wiley & Sons, Ltd.

Synthesis of 3-picoline from acrolein and ammonia through a liquid-phase reaction pathway using SO42−/ZrO2-FeZSM-5 as catalyst

Abstract The synthesis of 3-picoline from the liquid-phase condensation of acrolein and ammonium acetate under atmospheric pressure was conducted by first dissolving ammonium acetate in a C 2 C 6 carboxyl acid medium in the presence of solid acid catalyst, and then, feeding gradually a solution of acrolein in a C 2 C 6 carboxyl acid solvent. It was found that the employment of acetic acid, among various carboxyl acids tested, as both the reaction medium and solvent of acrolein, was most favorable, due to the obvious promotion to the formation of 3-picolind in liquid phase and retarding to the side reaction of acrolein polymerization in gas phase. The SO 4 2− /ZrO 2 -FeZSM-5 catalyst possesses the largest acid acidity and thus exhibited the largest yield of 3-picoline, among various solid acid catalysts. By employing the SO 4 2− /ZrO 2 -FeZSM-5 catalyst and acetic acid as both the reaction medium and solvent of acrolein, the influencing factors, including reaction temperature, molar ratio of ammonium acetate/acrolein/acetic acid, concentration and feeding rate of acrolein solution as well as usage of catalyst, were systematically investigated. The results indicated that an as high as 60% yield of 3-picoline could be achieved from a batch with molar ratio composition acrolein/ammonium acetate/acetic acid = 0.025/0.125/1.8, under the conditions of reaction temperature = 130 °C, concentration of acrolein solution = 14 wt%, feeding speed of acrolein solution = 12 mL/h and catalyst usage = 0.7 g/g (acrolein).

Hydrolysis of cellulose to produce glucose with solid acid catalysts in 1-butyl-3-methyl-imidazolium chloride ([bmIm][Cl]) with sequential water addition

Selective glucose production by cellulose hydrolysis with initial or sequential water addition in the presence of solid acid catalysts in 1-butyl-3-methyl-imidazolium chloride ([bmIm][Cl]) under microwave irradiation was investigated at 120 °C and 1.2 MPa of N2 atmosphere. For revealing the effect of water on cellulose hydrolysis in [bmIm][Cl], the phase behavior during the reaction was observed. Colored compounds formed at lower amounts of water, while some amounts of cellulose precipitated at higher amounts of water. Glucose yield was highest (65 mol%) at 25 wt% water in [bmIm][Cl] for the case of initial water addition. To improve the glucose yield, sequential water addition in which water was added in steps as the reaction proceeded was examined. Glucose yields in the presence of Amberlyst-15 in [bmIm][Cl] were 68.5 and 75.0 mol% by two-step and three-step water addition, respectively. Employing three-step water addition, Dowex 50wx8-100 (ion-exchange resin), hydrothermally synthesized carbon catalyst and three types of nano-zeolites were assessed. The carbon catalyst-modified fuming sulfuric acid and H-type zeolites (mordenite and faujasite) gave comparable glucose yields as Amberlyst-15. Sequential water addition is an effective technique for improving reaction efficiency in cellulose/solid acid catalyst/ionic liquid reaction systems.

Catalytic production of isosorbide from cellulose over mesoporous niobium phosphate-based heterogeneous catalysts via a sequential process

The catalytic valorization of cellulose as feedstock for the large-scale production of liquid fuels and value-added chemicals is currently subject to extensive research. Isosorbide as an important intermediate for the synthesis of a wide range of pharmaceuticals, chemicals and polymers, its efficient production from natural cellulose is very important. Here we report a two-step sequential process where cellulose is firstly depolymerized with Ru/NbOPO4-pH2 catalyst via hydrolysis and hydrogenation and then the resultant sorbitol and sorbitan are directly converted into isosorbide in the presence of solid acid catalyst. The influence of different solid catalysts is investigated in the direct dehydration of sorbitol to isosorbide and finds that NbOPO4-pH2 with the highest acid amount shows the best performance and is used in the sequential process. The reaction conditions (especially reaction temperature and reaction time) are systematically investigated and 56.7% isosorbide yield is obtained under optimal conditions, which is impressive compared with other systems reported with homogeneous or semi-heterogeneous catalysts. This effective catalytic system avoids the use of liquid acid and exhibits excellent cycling stability.

Acid-catalyzed olefination of bio-oil in the presence of ethanol

Background: Upgrading of bio-oil using acid-catalyzed olefination with added alcohol was explored. The previous approach of using a reagent such as 1-butanol to overcome the phase separation problem demonstrated excellent results. However, bio-based production of 1-butanol is still a low-yield process. In this work, a low-cost commodity solvent and reagent, ethanol, was used. Also, ethanol has lower viscosity than 1-butanol. Results & discussion: Bio-oil was reacted with excess 1-octene in the presence of solid acid catalysts and ethanol. Acid-catalyzed olefination induced changes in the resulting bio-oil by generating variety of alcohols, ethers, esters and oligomeric mixtures of the starting olefin. The reaction also decreased the water content and acid value, and increased the heating value of the bio-oil. However, the increase of the high heating value of the product bio-oil was moderate due to the presence of two phases in the reaction mixture. Conclusion: Ethanol is not as effective as less-polar 1-butanol at promoting 1-octene and bio-oil phase compatibility. This study shows the need for a low cost, better reagent than ethanol. The reagent should effectively decrease the phase separation to facilitate the reaction between bio-oil and the olefin. Solid acid catalysts with high hydrothermal stability are also needed to improve the upgrading process.