Conversion Of Propionic Acid Research Articles

Enhancing corn stalk-based anaerobic digestion with different types of zero-valent iron added during the acidification stage: Performance and mechanism

Anaerobic digestion has been defined as a competitive approach to facilitate the recycling of corn stalks. However, few studies have focused on the role of direct interspecies electron transfer (DIET) pathway in the acidification stage under the addition of different particle sizes of zero-valent iron (ZVI). In this study, three types of ZVI, namely iron filings, iron powder and nanoscale iron, were investigated, respectively, to enhance its high-value conversion. Variations in volatile fatty acids (VFAs) and methane (CH4) production associated with the underlying mechanisms were emphatically determined. Results indicated that the addition of ZVI could increase the concentration of VFAs, with the most outstanding performance observed with the use of nanoscale iron. Importantly, the conversion of propionic acid to acetic acid was driven by adding ZVI with no between-group differences in acidizing phase. Conversely, the substrate was more fully utilized when supplied with iron powder compared with other groups in methanogenic phase, thereby displaying the maximum CH4 yield with a value of 263.1 mL/(g total solids (TS)). However, adding nanoscale iron could signally shorten the digestion time (T80), saving 7 days in comparison to the group of iron powder.

Neisseria meningitidis Sibling Small Regulatory RNAs Connect Metabolism with Colonization by Controlling Propionate Use.

Neisseria meningitidis (meningococcus) colonizes the human nasopharynx, primarily as a commensal, but sporadically causing septicemia and meningitis. During colonization and invasion, it encounters different niches with specific nutrient compositions. Small noncoding RNAs (sRNAs) are used to fine-tune expression of genes, allowing adaptation to their physiological differences. We have previously characterized sRNAs (Neisseria metabolic switch regulators [NmsRs]) controlling switches between cataplerotic and anaplerotic metabolism. Here, we extend the NmsR regulon by studying methylcitrate lyase (PrpF) and propionate kinase (AckA-1) involved in the methylcitrate cycle and serine hydroxymethyltransferase (GlyA) and 3-hydroxyacid dehydrogenase (MmsB) involved in protein degradation. These proteins were previously shown to be dysregulated in a ΔnmsRs strain. Levels of transcription of target genes and NmsRs were assessed by reverse transcriptase quantitative PCR (RT-qPCR). We also used a novel gene reporter system in which the 5' untranslated region (5' UTR) of the target gene is fused to mcherry to study NmsRs-target gene interaction in the meningococcus. Under nutrient-rich conditions, NmsRs downregulate expression of PrpF and AckA-1 by direct interaction with the 5' UTR of their mRNA. Overexpression of NmsRs impaired growth under nutrient-limiting growth conditions with pyruvate and propionic acid as the only carbon sources. Our data strongly suggest that NmsRs downregulate propionate metabolism by lowering methylcitrate enzyme activity under nutrient-rich conditions. Under nutrient-poor conditions, NmsRs are downregulated, increasing propionate metabolism, resulting in higher tricarboxylic acid (TCA) activities. IMPORTANCE Neisseria meningitidis colonizes the human nasopharynx, forming a reservoir for the sporadic occurrence of epidemic invasive meningococcal disease like septicemia and meningitis. Propionic acid generated by other bacteria that coinhabit the human nasopharynx can be utilized by meningococci for replication in this environment. Here, we showed that sibling small RNAs, designated NmsRs, riboregulate propionic acid utilization by meningococci and, thus, colonization. Under conditions mimicking the nasopharyngeal environment, NmsRs are downregulated. This leads to the conversion of propionic acid to pyruvate and succinate, resulting in higher tricarboxylic acid cycle activity, allowing colonization of the nasopharynx. NmsRs link metabolic state with colonization, which is a crucial step on the trajectory to invasive meningococcal disease.

Mechanism of Electron Acceptor Promoting Propionic Acid Transformation in Anaerobic Fermentation

To improve the conversion efficiency of propionic acid in the post-anaerobic fermentation of biogas slurry, the anaerobic fermentation process using biogas slurry with a high acid content was simulated in an anaerobic reactor at 35 ± 0.5 °C using sodium propionate as the sole substrate. The effects of different electron acceptors (NO3−, SO42− and Fe3+) on propionic acid conversion and the succession of microbial community structures were investigated. The results showed that the experimental group with the electron acceptor NO3− exhibited the best anaerobic fermentation effect, with a maximum propionate removal rate of 94%, which was 36% higher than the control group without an electron acceptor. The maximum methane production rate was 307.6 mL/g COD, an increase of 30% compared with the control group. Thauera, Aquabacterium, Desulfomicrobium, Clostridium_sensu_stricto_1, and other functional microorganisms were all enriched. The dominant functional genes related to redox reactions, such as K03711, K00384, and K03406, were highly enriched in the reactor when Fe3+ and NO3− were added. The study shows that adding an electron acceptor can enhance interactions between microorganisms, achieve efficient propionate conversion, and improve methane production in the system.

Preparation of Ti Material Supported SBA-15 Functionalized with Sulfonic Acid Environmental Friendly Catalyst: Application for Esterification Process

Kinetics of catalytic esterification between propionic acid and n-butanol has been studied in a batch reactor by using a Ti-supported SBA-15 catalyst with sulfonic acid. The synthesized catalyst is used to test the efficacy of catalyst for esterification reaction. The SBA-15 acidity is tied to incorporation of Ti and -SO3H groups through and the use of Si/Ti with Si/S molar ratios. The results are mesoporous materials with a typical hexagonal structure of the Ti SBA-15 and wide areas and high pore diameters that are operated with sulfonic groups. The addition of SBA to Ti leads mainly to catalytic materials with Bronsted and Lewis acid sites. Ti SBA-15 is the most effective catalyst for sulfonic acid, with the highest consents of Lewis acid sites and deactivation resistance and low hydrophilicity. The effect of temperature, catalyst amount, and molar ratio on reaction kinetics has been studied. The conversion of propionic acid is found to be 91% at 115°C at a 2 : 1 ratio of n-butanol to propionic acid molars with 2% of sulfonic acid supported Ti SBA-15. The Eley-Rideal kinetic model is used to fit the experimental data. The activation energy and kinetic factor are found to be 29.63 kJ mol–1 and k o 0.549 L2 g-1 mol-1, respectively.

Comparison of cobalt ferrate-based nanoparticles for promoting biomethane evolution from lactic acid anaerobic digestion

Some inhibition of biomethane (bioCH4) production system can be observed, which is due to the propionic acid generation from lactic acid degradation. In this work, the three cobalt ferrate-based nanoparticles (NPs) such as CoFe2O4, CoAl0.2Fe1.8O4 and CoCu0.2Fe1.8O4 were synthesized to promote the bioCH4 evolution from lactic acid. The CH4 yields from the CoAl0.2Fe1.8O4, CoCu0.2Fe1.8O4 and CoFe2O4 groups at 300 mg/L of NPs were 431.52, 392.12 and 396.6 mL/g lactic acid, respectively. Moreover, the highest CH4 yield was 34.15% higher than that of the control reactor (321.67 mL/g lactic acid) without NPs. The three NPs accelerated lactic acid biodegradation and propionic acid conversion, thus obtaining more CH4. Surprisingly, microbial structure revealed that CoAl0.2Fe1.8O4 increased the abundance of Bacteroidetes_vadinHA17 to 16.6%, promoting the conversion from propionic acid to acetic acid. Meanwhile, the abundance of Methanobacterium in archaeal community from CoAl0.2Fe1.8O4 group rose from 45.81% to 68.45%, which facilitated bioCH4 production.

Kinetics on propionic acid catalytic esterification with N-butanol over SBA-15 (santa barbara amorphous-15 material) catalyst

A batch reactor was used to investigate kinetic behaviour of propionic acid withN-butanol over acidic ion-exchange resign SBA-15. The kinetic studies were performed for temperatures ranges 358oK to 388oK then feed varies 1–5 the molar proportions of propionic acid to N-butanol. The response rate was discovered to rise with rising temperature. However, propionic acid equilibrium conversions slightly change the entire reaction temperature suggesting this reaction's impact is negligible. It’s been discovered that propionic acid conversion improves with feed molar ratios rising from 1 to 5. Based on the outcomes of binary adsorption studies, relative sorption between two interacting species is determined. Water > n-butyl propionate > propionic acid > n-butanol follows the severity of adsorption strengths. The kinetic information was associated Langmuir Hinshelwood Haugan Watson modelsto assess kinetic variables for each model, respectively. The LHHW has produced the highest outcomes among these researched models.

Nanoscale zero-valent iron improved lactic acid degradation to produce methane through anaerobic digestion

Serious inhibition of methane production in an anaerobic digestion (AD) system can be caused by propionic acid, which is derived from lactic acid degradation. Nanoscale zero-valent iron (nZVI) was used in this study to improve conversion of propionic acid into acetic acid, thereby promoting methane production. The methane yield was markedly enhanced when nZVI concentration increased from 0 to 2 g/L; however, it decreased when nZVI concentration further increased to 8 g/L. At an nZVI concentration of 2 g/L, the methane yield increased by 37% from 398.5 to 546.4 mL CH4/g TVS. The abundance of Candidatus Cloacamonas in the bacterial community increased from 2.17% to 3.78%, which facilitated conversion of propionic acid into acetic acid. Meanwhile, the abundances of Methanomassiliicoccus and Methanosarcina in archaeal community increased, which was beneficial to methane production. Cyclic voltammetry showed that the electron transfer coefficient in the AD system increased from 0.029 to 0.034 s−1.

Sulphonated Tea Waste Carbon Catalyzed Esterification of Propionic Acid with Ethyl Alcohol: Modulus and Rate Constant Estimation

In this research paper, sulphonated carbon catalyst was prepared from left over (used) tea waste obtained after extraction of tea. The surface morphology of sulphonated tea waste carbon catalyst (STWCC) was accomplished using FTIR, SEM and BET. The structure of catalyst was found porous and exhibited excellent catalytic properties. The surface area of STWCC was estimated as 381m2/g. Moreover, catalyst was abound with the existence of many functional elements and most of them belonged to electron withdrawing groups, whose presence can be availed in hindering the leaching of catalyst. STWCC was employed in the esterification of propionic acid and ethyl alcohol at 1 to 3% (wt/wt) catalyst concentration and at temperatures 328 to 348 K. It was observed that, the rate of reaction as well as conversion of propionic acid increased with increasing catalyst loading and reaction temperature. The values of effectiveness factor, porosity / tortuosity ratio was also estimated and obtained as 0.99, 0.2 respectively. The effective diffusivity of STWCC was estimated at different temperature. The internal as well as external diffusion limitation were determined by Weisz-Prater criterion and found to be absent. Concisely, the novelty of present work is claimed on the basis of source of tea waste available, legal aspects, cost and end product application. The previous researchers reported the cost of tea waste from processing industries approximately Rs 25 to 30 per kg. Whereas the leftover tea waste mentioned in the present work is available for free of cost. Moreover, industrial tea waste producers are bound to follow the various protocols of waste management. Furthermore, the yield and surface area of activated carbon reported by them was low. Another inference that can be drawn that all the previous research focused their attention on synthesis of the adsorbent for purification of biodiesel, wastewater, etc. Thus, we claim for the novelty to reuse leftover tea waste to synthesize catalyst and subsequently apply in the esterification of propionic acid.

Unraveling the mechanism of the hydrodeoxygenation of propionic acid over a Pt (1 1 1) surface in vapor and liquid phases

Microkinetic models based on first principles calculations have been developed for the vapor and liquid phase hydrodeoxygenation of propionic acid over a Pt (1 1 1) surface. Calculations suggest that decarboxylation does not occur at an appreciable rate. In the vapor phase, decarbonylation products, propanal and propanol are all produced at similar rates. However, in both liquid water and 1,4-dioxane, propanol and propanal are favored over decarbonylation products. While a condensed phase can shift the reaction rate and selectivity significantly, the dominant pathways towards the various products are hardly affected. Only for propanal production do we observe a shift in mechanism. At 473 K, the propionic acid conversion rate is increased by one order of magnitude in liquid 1,4-dioxane relative to the gas phase. In liquid water, the conversion rate is similar to the vapor phase since adsorbed propionic acid blocks a large fraction of the surface sites.

Enhancement of methanogenic activity in anaerobic digestion of high solids sludge by nano zero-valent iron

This study evaluated the effects of nano zero-valent iron (NZVI, 50 nm) on anaerobic digestion of high solids sludge (10 ± 0.5%). Compared to the blank group without NZVI, the group with NZVI at all levels (10, 20 and 30 mM) played a driving role in methane production. The maximal methane production was increased by 37.5% in the group of 30 mM NZVI. The dynamic changes of hydrogen content and VFAs showed that rapid hydrogen evolutional corrosion of NZVI made lower hydrogen partial pressure in the later stage, which was more conducive to conversion of propionic acid. The microscopic analysis indicated that NZVI could flocculate and adsorb on the extracellular polymeric substances (EPS) around the anaerobic microorganisms, protecting most active microbial cell membrane from contact damage. On the other hand, some decaying microbial cells membrane could be destroyed by NZVI and intracellular substances would be released due to the reduction of EPS.

NiCuMo-SiO2 catalyst for pyrolysis oil upgrading: Model acidic treatment study

The main reasons of catalysts deactivation in hydro-processing pyrolysis liquids are by coke deposition, poisoning by bio-oil impurities (S, N, K, Cl, etc.), leaching of catalyst components, structural degradation in the presence of H2O, and sintering. The deactivation of catalysts by the acidity of the pyrolysis liquid is a specific concern, and this deactivation mechanism was studied by treating newly developed NiCuMo-SiO2 catalysts in 1 M acetic acid water solution (pH = 2–3). The activity of the acid-treated catalysts was subsequently investigated in the hydrodeoxygenation of gaseous propionic acid, in a tubular reactor at 225 °C with n-hexane and n-octane serving as diluent and internal standard, respectively.The samples treated by acid at different times (15–360 min) were characterized by X-ray diffraction (XRD), high resolution transition electron microscopy (HRTEM), X-ray fluorescence (XRF), CO chemisorption, N2 physical adsorption, and X-ray photoelectron spectroscopy (XPS). XRF and HRTEM studies together with the residual mass of catalyst pointed out at gradual leaching of catalyst components. Among the catalyst components, dissolution of nickel was the most pronounced, while molybdenum content decreased to a lesser extent. This is due to the formation of more acid stable molybdenum blues. The amount of copper decreased only slightly, due its higher electrochemical potential. Oxidation of metalliс species Cu and Ni is shown to obtain Cu2O, NiO and Ni(OH)2-like phases. Interestingly, the acidic treatment resulted in increasing active surface of the catalyst, nevertheless, the catalyst activity in propionic acid conversion irreversibly decreased in time by the acetic acid treatment due to loss of the active components (substantially nickel).

Reduction of Propionic Acid over a Pd-Promoted ReOx/SiO2 Catalyst Probed by X-ray Absorption Spectroscopy and Transient Kinetic Analysis

A Pd-promoted Re/SiO2 catalyst was prepared by sequential impregnation and compared to monometallic Pd/SiO2 and Re/SiO2. All samples were characterized by electron microscopy, H2 and CO chemisorption, H2 temperature-programmed reduction, and in-situ X-ray absorption spectroscopy at the Re LIII and Pd K-edges. The samples were also tested in the reduction of propionic acid to 1-propanol and propionaldehyde at 433 K in 0.1-0.2 MPa H2. Whereas monometallic Pd was inactive for carboxylic acid reduction, monometallic Re catalyzed aldehyde formation, but only after high-temperature pre-reduction that produced metallic Re. When Pd was present with Re in a bimetallic catalyst, Pd facilitated the reduction of Re in H2 to ~4+ oxidation state at modest temperatures, producing an active catalyst for the conversion of propionic acid to 1-propanol. Under the conditions of this study, the orders of reaction in propionic acid and H2 were approximately zero and one, respectively. Transient kinetic analysis of the carboxyl...

A comparative study on the synthesis of ethyl propionate in a pervaporation membrane reactor

In this study, esterification of propionic acid with ethanol over a tungstophosphoric acid catalyst was conducted in a batch reactor and in a pervaporation membrane reactor (MR). The performance of the esterification was determined in terms of the propionic acid conversion. Effects of the reaction temperature within the range of 50 °C–70 °C, the initial molar ratio of reactants (1:1, 2:1, 3:1), and the catalyst concentration (10–20 g cat/kg reactant) on the propionic acid conversion were investigated. A poly(vinyl alcohol) membrane was prepared and used to remove the water from the reaction media simultaneously. Conversion results of the batch reactor (BR) and the MR were compared. Results showed that the conversion of the reaction was improved by using MR. As the highest conversion of 80.7% was obtained in the BR, 92.9% of acid conversion was achieved in the MR at 70 °C when the alcohol:acid molar ratio was 3:1. The conversion of the propionic acid-ethanol esterification was enhanced between the values from 15% to 27% by using MR. Activation energy of the reaction carried out in the MR was found as 39.6 kJ/mol.

Conversion of propionic acid and 3-pentanone to hydrocarbons on ZSM-5 catalysts: Reaction pathway and active site

Conversion of propionic acid to gasoline-range molecules was investigated at 350°C on a series of ZSM-5 catalysts with varying density of Brønsted acid sites (BAS), achieved by ion exchange of proton with Na+. Ketonization of propionic acid to 3-pentanone is the primary reaction, with the sequential aldol condensation to dipentanone alcohol being the secondary. The major reaction pathway for forming the aromatics involves dehydration, cyclization, dehydration and hydride transfer from dipentanone alcohol, leading to the formation of C10 aromatics before being dealkylated to lighter aromatics. Temperature programmed desorption of propionic acid indicates that the reaction initiates with acylium cation formation on BAS through dehydration. Comparing the turnover frequencies of ketonization and aldol condensation on ZSM-5 with varying density of BAS indicates that BAS is the active site for both reactions. The propionic acid feed deactivates the catalyst faster than the 3-pentantone feed due to a stronger adsorption of propionic acid on the acid sites of ZSM-5.

Steam reforming of propionic acid: Thermodynamic analysis of a model compound for hydrogen production from bio-oil

The thermodynamic equilibrium of steam reforming of propionic acid (HPAc) as a bio-oil model compound was studied over a wide range of reaction conditions (T = 500–900 °C, P = 1–10 bar and H2O/HPAc = 0–4 mol/mol) using non-stoichiometric equilibrium models. The effect of operating conditions on equilibrium conversion, product composition and coke formation was studied. The equilibrium calculations indicate nearly complete conversion of propionic acid under these conditions. Additionally, carbon and methane formation are unfavorable at high temperatures and high steam to carbon (S/C) ratios. The hydrogen yield versus S/C ratio passes a maximum, the value and position of which depends on temperature. The thermodynamic equilibrium results for HPAc fit favorably with experimental data for real bio-oil steam reforming under same reaction conditions.

Process optimization and kinetic modeling for esterification of propionic acid with benzyl alcohol on ion-exchange resin catalyst

Benzyl propionate, an ester with floral and fruity odor, has significant applications in perfumery and flavor industries. This paper describes the optimization of the synthesis of benzyl propionate catalyzed by Amberlyst-15. The effects of various process parameters such as catalyst loading, alcohol-to-acid molar ratio and reaction temperature on propionic acid conversion and yield of ester were assessed by response surface methodology (RSM). The external and internal mass transfer limitations were found to be absent. Analysis of variance (ANOVA) showed that the acquired quadratic model successfully interpreted the experimental data with the coefficient of determination values, (R2>0.98) and adjusted R2 values, (>0.97). The RSM model was validated by good agreement between the model predicted and experimental values for responses. Pseudohomogeneous (PH) kinetic model was used and validated (R2>0.95) with the experimental data. The activation energy and frequency factor were evaluated as 42.07 kJ mol−1 and 19,874.64 L mol−1 min−1, respectively.

Enhancement of esterification conversion using pervaporation membrane reactor

In the present study, the esterification reaction of propionic acid with isobutyl alcohol to produce isobutyl propionate and water was studied. The performance of esterification reaction was compared by using the batch process and the pervaporation assisted hybrid process which performs the reaction and separation simultaneously. A polyvinyl alcohol–polyethersulphone (PVA–PES) hydrophilic polymeric membrane was used in the study to separate water and also to shift the equilibrium. The influence of process parameters such as catalyst loading, molar ratio of acid to alcohol, reaction temperature and ratio of membrane area to initial reaction volume (S/V) was studied. The results showed that the pervaporation assisted esterification process gave more conversion than the batch process of esterification. The membrane showed high selectivity to the removal of water in the propionic acid, isobutyl alcohol, isobutyl propionate and water mixture. Moreover, the conversion of propionic acid was enhanced by enhancing the catalyst amount, molar ratio of acid to alcohol, reaction temperature and S/V ratio.

Enhancement of esterification conversion using pervaporation membrane reactor

In the present study, the esterification reaction of propionic acid with isobutyl alcohol to produce isobutyl propionate and water was studied. The performance of esterification reaction was compared by using the batch process and the pervaporation assisted hybrid process which performs the reaction and separation simultaneously. A polyvinyl alcohol–polyethersulphone (PVA–PES) hydrophilic polymeric membrane was used in the study to separate water and also to shift the equilibrium. The influence of process parameters such as catalyst loading, molar ratio of acid to alcohol, reaction temperature and ratio of membrane area to initial reaction volume (S/V) was studied. The results showed that the pervaporation assisted esterification process gave more conversion than the batch process of esterification. The membrane showed high selectivity to the removal of water in the propionic acid, isobutyl alcohol, isobutyl propionate and water mixture. Moreover, the conversion of propionic acid was enhanced by enhancing the catalyst amount, molar ratio of acid to alcohol, reaction temperature and S/V ratio.

Sulfate addition as an effective method to improve methane fermentation performance and propionate degradation in thermophilic anaerobic co-digestion of coffee grounds, milk and waste activated sludge with AnMBR

This study was conducted to investigate the effects of sulfate on propionate degradation and higher organic loading rate (OLR) achievement in a thermophilic AnMBR for 373days using coffee grounds, milk and waste activated sludge (WAS) as the co-substrate. Without the addition of sulfate, the anaerobic system failed at an OLR of 14.6g-COD/L/d, with propionate accumulating to above 2.23g-COD/L, and recovery by an alkalinity supplement was not successful. After sulfate was added into substrates at a COD/SO42− ratio of 200:1 to 350:1, biogas production increased proportionally with OLR increasing from 4.06 to 15.2g-COD/L/d. Propionic acid was maintained at less than 100mg-COD/L due to the effective conversion of propionic acid to methane after the sulfate supplement was added. The long-term stable performance of the AnMBR indicated that adding sulfate was beneficial for the degradation of propionate and achieving a higher OLR under the thermophilic condition.

Phosphorus limitation strategy to increase propionic acid flux towards 3-hydroxyvaleric acid monomers in Cupriavidus necator

Properties of polyhydroxybutyrate-co-hydroxyvalerate (P(3HB-co-3HV)) depend on their 3HV content. 3HV can be produced by Cupriavidus necator from propionic acid. Few studies explored carbon distribution and dynamics of 3HV and 3HB monomers production, and none of them have been done with phosphorus as limiting nutrient. In this study, fed-batch cultures of C. necator with propionic acid, as sole carbon source or mixed with butyric acid, were performed. Phosphorus deficiency allowed sustaining 3HV production rate and decreasing 3HB production rate, leading to an instant production of up to 100% of 3HV. When a residual growth is sustained by a phosphorus feeding, the maximum 3HV percentage produced from propionic acid is limited to 33% (Mole.Mole(-1)). The association of a second carbon source like butyric acid lead to higher conversion of propionic acid into 3HV. This study showed the importance of the limiting nutrient and of the culture strategy to get the appropriate product.