Sulfuric Acid Loading Research Articles

Effect and mechanism of ultrasound on acid loading in the preparation of silicon-based sulfonic solid acids

Silicon-based sulfonic solid acids have the advantages of high catalytic activity and selectivity, easy separation from products, low equipment corrosion, and environmental protection, and sulfuric acid loading is the key to their preparation. To overcome the shortcomings of low acid loading and uneven distribution in the existing preparation methods of micron-sized silicon-based sulfonic solid acids, a method was proposed to prepare micron-sized silicon-based sulfonic solid acids using ultrasonic enhanced technology. The effect of different reaction parameters, such as time, power, and temperature of ultrasonication, sulfonation temperature and time, and sulfuric acid concentration, on acid loading in solid acid was investigated in this work. The results showed that a micron-sized mesoporous silica-based solid acid was successfully synthesized with a high acid content of 0.8633 mmol/g, uniform acid distribution, high specific surface area of 269.332 m2/g, and large average particle size of 172.142 μm in this work. The introduction of ultrasound was found to expand the carrier's pore volume and increase the carrier's specific surface area and the number of hydroxyl groups, thereby increasing the acid loading capacity and the specific surface area of the solid acid sample by 66.6 % and 10.97 % respectively, compared with the case without ultrasound.

Insights into enhancing SO2 tolerance for catalytic combustion of toluene over sulfated CeZrOx supported platinum catalysts

Supported platinum catalysts are widely used in the catalytic combustion of volatile organic compounds due to their excellent catalytic activity, but SO2 poisoning is one of the critical problems for the industrial application. In this work, a series of sulfated ceria-zirconia composite oxides (CeZrOx) supported platinum catalysts (Pt/CeZr-S) were prepared through the support sulfation strategy. In the catalytic combustion of toluene, the Pt/CeZr-S catalyst with 0.5 wt% Pt and 15 wt% sulfuric acid loading amounts exhibited the significantly increased activity compared with the reference Pt/CeZr catalyst. Moreover, the tolerance to SO2 poisoning of Pt/CeZr-S catalyst was greatly improved in the presence of 50 ppm SO2. Various characterization methods including XPS, NH3-TPD and in-situ DRIFTS were performed to reveal the structure-activity relationship and SO2 tolerance mechanism. The higher concentration of metallic Pt0 species resulting from the interaction of Pt species and acidic CeZr-S support contributed to the enhanced catalytic activity. Meanwhile, the increased acidity strength and total acidity amounts over Pt/CeZr-S catalysts could affect the sulfation process, resulting in significant inhibition of the adsorption and further accumulation of sulfur species.

Biodiesel production by esterification of ricinoleic acid over a series of synthesized sulfated zirconia catalysts

A series of sulfated zirconia (SZ) were synthesized and evaluated for catalytic esterification of ricinoleic acid obtained from the castor oil with butanol at 110 °C. The effect of alcohols’ chain length was studied using butanol (C4), propanol (C3), ethanol (C2) and methanol (C1) at 65 °C, and reflux of corresponding alcohol boiling points. The synthesized catalysts were characterized using nitrogen porosimetry, X-ray powder diffraction, thermogravimetric analysis and Diffuse Reflectance Infrared Fourier Transform Spectroscopy. Analysis of ricinoleic conversion was performed using gas chromatography. Sulfuric acid loading improved the surface area of zirconia at a lower dose. The surface areas of the catalysts increased as the concentrations of sulfuric acid solution were increased from 0.025 to 0.10 M, after which the decline was observed. SZ obtained at 0.05 M H2SO4 (0.05SZ) gave the optimal catalytic activity compared to the other series of SZ used. The ricinoleic acid conversion decreased with increase of alcohol alkyl chain from C1-C4 at 65 °C, but increased under the reflux temperature of the corresponding alcohols, with the maximum conversion being 47% at 118 °C for the reaction involving butanol. Overall, the synthesized SZ catalysts are deployable in biodiesel production from castor oil upon optimizing other conditions.
 Keywords: Ricinoleic acid; Sulfated zirconia; Biodiesel production

Influence of preparation method on the adsorptive performance of silica sulfuric acid for the removal of gaseous o-xylene

Two types of silica supported sulfuric acid (SSA), with same sulfuric acid loading of 3.4 mmol g−1, were prepared by sol-gel processing (SSAI) and impregnation method (SSAII). The TG/DSC and FTIR characterization revealed that two anchoring states coexisted for the sulfuric acid supported on the silica surface: a physiosorbed (P)-state and a chemically bonded (C)-state. The dynamic adsorption analysis demonstrated that both SSAI and SSAII possessed a significant removal capacity for gaseous o-xylene in the reactive temperature regions (120–200 °C and 130–200 °C), which could be attributed to the sulfonation reaction between o-xylene and anchored sulfuric acid. The optimum temperatures were noted to be 150 °C and 160 °C for SSAI and SSAII respectively. Further, SSAI exhibited a higher breakthrough adsorption capacity (QB, 184.9 mg g−1) as compared to SSAII (142.8 mg g−1). QB was noted to be closely associated with the amount or proportion of the C-state sulfuric acid on the SSA surface. The optimal values of breakthrough time and QB were obtained by enhancing the bed height and decreasing the flow rate and inlet concentration. Both SSAI and SSAII exhibited excellent recyclability and reuse performance over eight consecutive adsorption/regeneration cycles, thus, suggesting that the SSAs prepared using different methods, especially SSAI, have a significant potential of application as adsorbents for the removal of BTEX pollutants.

A comparative study of the removal of o-xylene from gas streams using mesoporous silicas and their silica supported sulfuric acids

The three types of silica supported sulfuric acids (SSA), with the same sulfuric acid loading of 9.25 mmol g−1, were prepared by a wet impregnation method from silica gel (SG), SBA-15 and MCM-41. Characterization of the prepared SSA showed that two anchoring states coexisted for sulfuric acid supported on the surface of the silicas: A physiosorbed (P)-state sulfuric acid; and a chemically bonded (C)-state sulfuric acid. Dynamic adsorption results showed that each SSA had a significant removal capacity for o-xylene gas in the reactive temperature regions. The ranges of the reactive regions were 120–220 °C (SSA/SG), 120–230 °C (SSA/SBA-15) and 120–250 °C (SSA/MCM-41), and this could be attributed to the sulfonation reaction between o-xylene and the anchored sulfuric acid. SSA/MCM-41 showed the highest theoretical breakthrough adsorption capacity (QB, th, 526.71 mg g−1) compared with SSA/SBA-15 (363.54 mg g−1) and SSA/SG (239.15 mg g−1). QB, th was closely associated with the amount or proportion of the C-state sulfuric acid on the surface of each SSA. Optimum breakthrough time and QB, th was obtained by increasing the bed height and decreasing flow rate and inlet concentration. The SSA exhibited excellent recyclability and reuse performance over eight consecutive adsorption/desorption/regeneration cycles. The results suggested that the SSA, especially SSA/MCM-41, might have good potential in applications using adsorbents for the removal of BTEX pollutants.

Esterification of Levulinic Acid to Ethyl Levulinate Using Liquefied Oil Palm Frond-Based Carbon Cryogel Catalyst

Oil palm biomass, which is abundantly available in Malaysia, has many types of applications in various industries. In this study, oil palm frond (OPF) was liquefied with 1-butyl-3-methylimidazole hydrogen sulfate ([BMIM][HSO4]) ionic liquid (IL) at optimum conditions. The liquefied OPF-ionic liquid (LOPF-IL) was mixed with furfural at a ratio of 0.8 (w/w), water-to-feedstock ratio of 0.125 (w/w), and sulfuric acid loading of 0.5 mL at 100 °C for 1 h to form a gel. Carbon cryogel liquefied oil palm frond (CCOPF) was prepared using a freeze-dryer followed by calcination. CCOPF was further characterized using N2 sorption, NH3-TPD, TGA, XRD, FTIR, and FESEM to determine its physical and chemical properties. The thermally stable CCOPF exhibited a large total surface area (578 m2/g) and high total acidity (17.6 mmol/g). Next, CCOPF was tested for levulinic acid catalytic esterification by varying the parameters including ethanol-to-levulinic acid molar ratio, catalyst loading, and reaction time at 78 °C. At the optimum conditions, the conversion of levulinic acid and ethyl levulinate yield was 70.9 and 71.7 mol%, respectively. CCOPF was reusable up to five runs with no significant conversion drop. Accordingly, CCOPF is conferred as a potential biomass-derived acid catalyst for ethyl levulinate production.

Synthesis and characterization of porous microspherical ionic liquid carbon cryogel catalyst for ethyl levulinate production

A new type of carbon cryogel was synthesized from ionic liquid, a green solvent, and furfural mixtures. Initially, the gel, formed via sol-gel polycondensation reaction, was freeze-dried, calcined and denoted as CCIL. The effect of furfural to IL (F/IL) ratio, water to IL (W/IL) ratio and sulfuric acid loading on the synthesis of gel was investigated. In addition, the effect of calcination temperature and time were also studied for CCIL preparation. The physical and chemical properties were evaluated with nitrogen physisorption, temperature programmed desorption of ammonia (NH3-TPD), and thermogravimetric analyzer (TGA). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy with energy dispersive X-ray spectrometry (FESEM-EDX), CHNS analysis, total organic carbon (TOC) and nuclear magnetic resonance spectroscopy (NMR) results were also analyzed. Catalytic testing, conducted to evaluate the performance of CCIL in esterification of levulinic acid with ethanol, inferred large total surface area and high acidity corroborated with good activity. The selected CCIL registered ethyl levulinate yield of 66.9 mol%. The experimental results demonstrated the catalyst, derived from new feedstocks, is a potential solid acid catalyst for biomass conversion.

Influence of Ethanol Organosolv Pulping Conditions on Physicochemical Lignin Properties of European Larch

Over the years, the organosolv pulping process has proven to be a valuable pretreatment method for various lignocellulosic feedstocks. The objective of this study was to characterize and assess the potential applicability of the organosolv lignin fraction from European larch sawdust, as no research has been conducted in this field so far. Eight different samples were prepared from the European larch sawdust under varied reaction conditions and one milled wood lignin sample as reference. The reaction temperature and sulfuric acid loading were varied between 420 and 460 K and 0.00 and 1.10% (w/w on dry wood basis) H2SO4, respectively. The antiradical potential (via DPPH• method), chemical structure (via ATR-FTIR, 1H NMR, 31P NMR, and thioacidolysis), as well as the molecular weight distribution of the isolated lignins were analyzed and compared. Results from thioacidolysis show a direct correlation between the amount of β-ether bonds broken and pulping process severity. Similarly, both antiradical potential and phenolic hydroxyl group content exhibit a direct relationship to reaction temperature and catalyst loading. On the contrary, the content of aliphatic hydroxyl groups and the average molecular weights both decreased with increasing process severity. The high content of phenolic hydroxyl groups and antioxidative potential of the larch organosolv fractions, especially for the sample isolated at 460 K and 1.10% H2SO4 loading, indicate good applicability as antioxidants as well as feedstocks for further downstream valorization and require additional research in this area.

Microwave Assisted Glycerolysis Of Neem Oil

Biodiesel is considered as a viable alternative to diesel fuels since it is renewable and eco-friendly. Edible oils account for majority of feedstock oils used in biodiesel production since their free fatty acids (FFA) levels are below 1%. However, these oils are expensive and compete with food demand. Low cost feedstock oils may be used but they must undergo a pre-treatment process (glycerolysis) to reduce their FFA content to less than 1%. Conventional glycerolysis requires long reaction times so microwave irradiation is used to speed up the process. Neem oil with an initial %FFA of 1.138% was used to determine the effect of microwave irradiation on different factors that would affect the FFA reduction. The following factors are investigated: reaction time (5 and 9 minutes), reaction temperature (100°C and 120°C), oil to glycerol molar ratio (1:1 and 1:2) and sulfuric acid catalyst concentration or loading (2% and 4.5%). This study reports that reaction temperature was the only significant factor on FFA reduction. A higher temperature resulted in a higher FFA reduction. The optimum factors achieved are: oil to glycerol molar ratio of 1:1, a catalyst loading of 2%, a time of 5.58 minutes and a reaction temperature of 120°C resulting in a 91.81% FFA reduction

Intensification of esterification of non edible oil as sustainable feedstock using cavitational reactors

Using sustainable feed stock such as non-edible oil for the biodiesel production can be one of the cost effective approaches considering the ever growing interest towards renewable energy and problems in existing approaches for production. However, due to the high free fatty acid content, non-edible oils require considerable preprocessing before the actual transesterification reaction for biodiesel production. The present work focuses on intensification of the esterification reaction used as preprocessing step based on acoustic and hydrodynamic cavitation also presenting the comparison with the conventional approach. Karanja oil with initial acid value as 14.15mg of KOH/g of oil has been used as a sustainable feedstock. Effect of operating parameters such as molar ratio, catalyst loading, temperature and type of catalyst (sulfuric acid and Amberlyst-15) on the acid value reduction has been investigated. The maximum reduction in the acid value (final acid value as 2.7mg of KOH/g of oil) was obtained using acoustic cavitation at optimum molar ratio of oil to methanol as 1:5 and 2% sulfuric acid loading at ambient temperature. In the case of hydrodynamic cavitation, acid value reduced upto 4.2mg of KOH under optimized conditions of first stage processing. In the second stage esterification using hydrodynamic cavitation and conventional approach, the final acid value was 3.6 and 3.8mg of KOH/g of oil respectively. Energy requirement analysis for ultrasound and conventional approaches clearly established the superiority of the ultrasound based approach. The present study clearly demonstrated that significant intensification benefits can be obtained in terms of the reduction in the molar ratio and operating temperature for the case of acoustic cavitation as compared to the conventional approach with somewhat lower effects for the hydrodynamic cavitation.

Crude glycerol-mediated liquefaction of saccharification residues of sunflower stalks for production of lignin biopolyols

Biopolyol was produced by the liquefaction of the sunflower stalk saccharification residues using a biodiesel-derived crude glycerol as a liquefaction solvent. Biopolyol was produced under the optimal conditions of 10% (w/w) biomass loading, 4% (w/w) sulfuric acid loading at 150°C and for 60min. Biomass conversion was 59%, and the hydroxyl and acid number numbers were 1460 and 11mgKOH/g biopolyol, respectively. The bio-PU was synthesized from the biopolyol and methylene diphenyl diisocyanate (MDI). Fourier transform infrared spectroscopy (FTIR) showed that bio-PU was successfully synthesized from biopolyols and MDI.

Liquefaction of Red Pine Wood, Pinus densiflora , Biomass Using Peg-400-Blended Crude Glycerol for Biopolyol and Biopolyurethane Production

Red pine wood, Pinus densiflora, biomass was liquefied through liquefaction using a solvent mixture of crude glycerol and PEG-400 with a sulfuric acid catalyst. The liquefaction process parameters of crude glycerol/PEG-400 blending ratio, biomass loading, acid loading, reaction temperature, and reaction time were optimized. Biopolyol with 61.9% biomass conversion was produced at 170°C within 1 h using a co-solvent of crude glycerol and PEG-400 (5/5, w/w), 15% biomass loading, and 3% sulfuric acid loading. The biopolyol possessed a 4.2 mg KOH/g acid number and 892.4 mg KOH/g hydroxyl number. Polyurethane foam was successfully synthesized from the liquefied red pine wood biomass with toluene diisocyanate. The synthesis of biopolyurethane derived from red pine wood biopolyol was confirmed with FT-IR.

Impact of combined acid washing and acid impregnation on the pyrolysis of Douglas fir wood

This study reports the impact of acid washing (to remove alkali and alkaline earth metals) followed by mild acid impregnation on the pyrolysis of Douglas fir wood. Dilute nitric acid was used in the washing and sulfuric acid, acetic acid, nitric acid, and phosphoric acid at acid loading levels of 0.05, 0.1, 0.3, and 0.5wt.% were used for the acid impregnation to improve the yield of levoglucosan. A Py–GC/MS instrument was used to semi-quantitatively measure the impact of various acids and concentrations on the yield of low molecular weight compounds released during pyrolysis at 500°C. The nitric acid wash removed 56% of the metal content. The results confirmed all the acids studied increased the production of levoglucosan, likely due to the mitigation of undesirable interactions between the cellulose and the other constituents of the lignocellulosic matrix. The highest yields of levoglucosan were achieved with the strong acids: sulfuric acid loading of 0.05wt.%, nitric acid 0.05wt.% and phosphoric acid 0.3wt.%. Sulfuric and phosphoric acid also enhanced dehydration reactions in cellulose products and decreased the production of methoxylated phenolics from lignin. The very small range of concentration at which these acids increase levoglucosan yield makes it very difficult to control the process. In the case of acetic acid, it is not strong enough to catalyze dehydration reactions. Consequently a much wider range of concentrations can be used thus facilitating the control of the process. Acetic acid also does not affect the yield of lignin products. Therefore, acetic acid appears to be the most practical for acid impregnation (following mineral removal) in wood pyrolysis.

Preparation and Characterization of Biopolyols and Polyurethane Foams from Liquefied Faba Bean Stalk

In this study, Faba bean stalk was liquefied for the production of biopolyols and polyurethane (PU) foams. The influences of various reaction conditions on biopolyols and PU foams were examined. Furthermore, the property relationships between biopolyols and PU foams were investigated. Biopolyols produced under the liquefaction conditions of 160°C, 90 min, 3% sulfuric acid loading, and 20% Faba bean stalk loading showed promising material properties (i.e. hydroxyl number, 496.1 mg KOH/g, acid number, 17.9 mg KOH/g, and viscosity, 1.1 Pa.s). PU foams produced from promising biopolyols showed compressive strength of 205 kPa and density of 0.035 g/cm3. The results suggested that in addition to density, the compressive strength of PU foams might also be affected by factors such as biomass residues or the chemical structures of biopolyols. The biopolyols and PU foams produced showed material properties comparable to those of conventional PU foams.

Acid Bisulfite Pretreatment of Eastern Redcedar for Fermentable Glucose Production: Optimization through Response Surface Methodology

<abstract> <bold><sc>Abstract.</sc></bold> Eastern redcedar is considered a nuisance by many landowners in the U.S. Central Plains, and processes that add value to this softwood tree are actively being sought. The primary goal of this study was to determine the optimal pretreatment conditions to efficiently obtain glucose from eastern redcedar. Response surface methodology (RSM) based on a uniform precision rotatable central composite design (CCD) was used to design the experiments and analyze the influence of four pretreatment process variables (pretreatment temperature, hold time, sulfuric acid loading, and sodium bisulfite loading) on wood glucan-to-glucose yields. The highest wood glucan-to-glucose yield of 91% was predicted at the optimum conditions of 200°C, 7.5 min of hold time, 3.75 g sulfuric acid 100 g^-1 dry wood, and 22.5 g sodium bisulfite 100 g^-1 dry wood. The prediction model was validated by conducting experiments at the optimized conditions, resulting in 87% ±2% of theoretical wood glucan-to-glucose yield. Mass balances calculated 70% delignification and 89% to 100% loss of hemicellulose polymers during pretreatments.

High dry matter whole-plant corn as a biomass feedstock

This research investigated the harvest, ambient pre-treatment, and storage of whole-plant corn as an alternative to conventional systems where corn grain and stover are fractionated at harvest. Harvesting the whole-plant, both grain and most of the above ground stover, after physiological maturity can reduce the intense logistics challenges typically associated with corn harvest and expand the harvest window. To determine the feasibility of the proposed system, corn was harvested at 350–840 g kg−1 whole-plant dry matter (DM) using a forage harvester and then ensiled in pilot-scale silos. Ambient pretreatment during storage was investigated using both dilute acid and lime. Both pretreated and control whole-plant silages were very well conserved during anaerobic storage with DM losses generally less than 40 g kg−1. Hydrodynamic separation of the grain and stover fractions after storage was found to be more effective at fractionating starch and fiber than conventional dry grain harvest, and both fractions had desirable composition. The effects of pretreatment on the silage were very pronounced at 30 and 100 g (kg DM)−1 sulfuric acid loading with less than 100 g (kg DM)−1 of the hemicellulose still bound in the cell wall at DM contents greater than 500 g kg−1. The whole-plant harvest and storage system was shown to be a viable alternative to conventional corn grain and stover systems for producing feedstocks for biochemical conversion.

Thermochemical conversion of crude glycerol to biopolyols for the production of polyurethane foams

This study aimed to produce biopolyols from crude glycerol via a novel thermochemical conversion process. The effect of operational parameters, including sulfuric acid loading and reaction temperature and time, on the properties of the produced biopolyols was investigated. Biopolyols produced under preferred reaction conditions of 200°C, 90 min, and 3% sulfuric acid loading showed a hydroxyl number of around 481 mg KOH/g, an acid number of around 5mg KOH/g, and a viscosity of around 25.0 Pas. The resulting polyurethane (PU) foams showed a compressive strength of around 184.5 kPa and a density of around 43.0 kg/m(3), comparable to those of some petroleum-based analogs. Characterization of the biopolyols via pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), gas chromatography (GC), and thermogravimetrical analysis (TGA) showed that the major reactions of this process were the formation of monoglycerides and diglycerides through the esterification and transesterification of different components in crude glycerol.

Development of an efficient pretreatment process for enzymatic saccharification of Eastern redcedar

This study investigates the potential for extracting sugars from the polysaccharides of Eastern redcedar. Pretreatment temperature, time, sulfuric acid loading, sodium bisulfite loading and impregnation time were varied using factorial treatment design experiments for identifying near optimal overall wood glucan-to-glucose yields during acid bisulfite pretreatments. The highest overall wood glucan-to-glucose yield of 87% was achieved when redcedar was impregnated with pretreatment liquor containing 3.75g of sulfuric acid/100g of dry wood and 20g of sodium bisulfite/100g of dry wood at 90°C for 3h followed by increasing the temperature to 200°C with a hold time of 10min. Hemicellulose and lignin removal during pretreatments made the substrate amenable to enzymatic hydrolysis using 0.5ml of Accelerase® 1500/g of glucan at 2% (w/w) solid loading. Preliminary mass balances showed 97% glucan recovery at pretreatment condition with 87% overall wood glucan-to-glucose yield and 59% delignification.

Preparation of levoglucosenone through sulfuric acid promoted pyrolysis of bagasse at low temperature

Fast pyrolysis of bagasse pretreated by sulfuric acid was conducted in a fixed bed reactor to prepare levoglucosenone (LGO), a very important anhydrosugar for organic synthesis. The liquid yield and LGO yield were studied at temperatures from 240 to 350°C and sulfuric acid loadings from 0.92 to 7.10wt.%. An optimal LGO yield of 7.58wt.% was obtained at 270°C with a sulfuric acid pretreatment concentration of 0.05M (corresponding to 4.28wt.% sulfuric acid loading). For comparison, microcrystalline cellulose pretreated by 0.05M sulfuric acid solution was pyrolyzed at temperature from 270°C to 320°C, and bagasse loaded with 3–5wt.% phosphoric acid was pyrolyzed at temperature from 270°C to 350°C. The highest yield of LGO from bagasse was 30% higher than that from microcrystalline cellulose, and treatment with sulfuric acid allowed a 21% higher yield than treatment with phosphoric acid.

Production and characterization of biopolyols and polyurethane foams from crude glycerol based liquefaction of soybean straw

The feasibility of using crude glycerol to liquefy soybean straw for the production of biopolyols and polyurethane (PU) foams was investigated in this study. Liquefaction conditions of 240°C, >180min, 3% sulfuric acid loading, and 10–15% biomass loading were preferred for the production of biopolyols with promising material properties. Biopolyols produced under preferential conditions showed hydroxyl numbers from 440 to 540mg KOH/g, acid numbers below 5mg KOH/g, and viscosities from 16 to 45Pa.s. PU foams produced under preferential conditions showed densities from 0.033 to 0.037g/cm3 and compressive strength from 148 to 227kPa. These results suggest that crude glycerol can be used as an alternative solvent for the liquefaction of lignocellulosic biomass such as soybean straw for the production of biopolyols and PU foams. The produced biopolyols and PU foams showed material properties comparable to their analogs from petroleum solvent based liquefaction processes.