Selection For Increased Production Research Articles

Hydroxyl radical-regulated crystallization of hierarchical H-ZSM-5 at low temperatures for palm oil conversion into high aromatic green gasoline

Biofuel is a sustainable fuel that is more environmentally friendly. Common biofuel processing is pyrolysis, which requires high energy. The use of appropriate catalysts can reduce the activation energy and increase product selectivity. H-ZSM-5 has excellent characteristics as a catalyst. However, hierarchical H-ZSM-5 has better characteristics because catalyst deactivation can be minimized and substrate diffusion increased. Generally, the H-ZSM-5 crystallization rate is relatively slow; in this research, OH radicals (OH) have successfully increased the crystallization rate of hierarchical H-ZSM-5. A successful synthesis of H-ZSM-5 was confirmed based on FTIR spectra and XRD diffractogram, which showed characteristic peaks in H-ZSM-5 for both TR-3 (H-ZSM-5 synthesized using OH for three days) and TN-3 (H-ZSM-5 synthesized without OH for three days). The use of OH shows an increase in the rate constant up to 3 times, producing highly crystalline TR-3. The use of OH also affected the morphology of H-ZSM-5, where TR-3 crystals tended to be more spheric with a larger size than TN-3. Porosity analysis showed higher porosity and better mesoporous features, where SBET increased from 309 to 373 m2/g, and Sext increased from 226 to 237 m2/g. This gave good effects on the catalytic ability of TR-3 compared to TN-3 by increasing gasoline yield in palm oil cracking from 35.91 wt% to 38.82 wt%, while the enhancement of the mesoporous features successfully inhibiting coke formation on the catalyst from 3.23 wt% becomes 2.02 wt% so that catalyst deactivation can be minimized.

The Catalytic Function of Phosphorus Enriched on the Surface of Vanadium‐based Catalysts in Selective Oxidations

AbstractVanadium phosphates are established as the benchmark system for the selective oxidation of n‐butane towards maleic anhydride. By varying the phosphorus content on the surface of three V‐based catalysts with diverse performance, this study experimentally elaborates on the catalytic function of phosphorus. Contact time variation and cofeed studies revealed, that surface phosphates, deposited in sub‐monolayers via atomic layer deposition, significantly contribute to an increased product selectivity. Furthermore, our results suggest that the phosphorus particularly suppresses the consecutive combustion of the (re‐)adsorbed product. The recently introduced solid solution catalyst V1‐xNbxOPO4 with medium maleic anhydride selectivity could be tuned by the surface enrichment with phosphorus towards product selectivities of up to SMAN=60 %, under optimized alkane‐rich feed conditions. Therefore, POx‐V0.3Nb0.7OPO4 is introduced as promising catalyst, which is not based on vanadyl(IV) pyrophosphate, to access significantly higher MAN formation rates at increased alkane partial pressures of cn‐butane>10 %vol in n‐butane oxidation.

The Effect of Adding Mg-Zn/Al Hydrotalcite on the Decarboxylation Product of Hydroxy Pelargonate Soap

Pelargonic acid is a by-product of the ozonolysis reaction of oleic acid to azelic acid. Pelargonic acid decarboxylation is the process of removing a carboxyl group (-COO-) from pelargonic acid (C9H18O2) to produce n-octane (C8H18) hydrocarbons, which are the main group of hydrocarbons that make up gasoline. The main parameter in gasoline is the octane number. The octane number of n-octane (C8H18) is 15, which is considered low, while good gasoline is desired to have a high octane number. To convert straight-chain alkanes and alkenes into branched alkanes and alkenes, an isomerization process can be carried out on vapor-cracking products using a solid catalyst. Transition metals and their compounds can be used as catalysts. Transition metals are able to change the oxidation state, create complex compounds, absorb other substances on the metal surface, and activate these substances. The transition metals used in this study are Zn and Al. The stages of the research process were the preparation of Mg-Zn/Al hydrotalcite base, the manufacturing of hydroxy pelargonate soap, and the decarboxylation of hydroxy pelargonate soap. The results of this study found that the highest product gain, namely 64.76%, occurred when Mg-Zn/Al = 5:5:2 hydrotalcite was in 300% excess. The highest product selectivity to 2.16% n-octane occurred in the use of a 300% excess of Mg-Zn/Al = 3:3:2 hydrotalcite. A low Al/Mg/Zn ratio of 2:10 can increase product yield; a high Al/Mg/Zn ratio of 2:6 can increase product selectivity and lower the freezing point.
 

Induction Heating of Magnetically Susceptible Nanoparticles for Enhanced Hydrogenation of Oleic Acid.

Radio frequency (RF) induction heating was compared to conventional thermal heating for the hydrogenation of oleic acid to stearic acid. The RF reaction demonstrated decreased coke accumulation and increased product selectivity at comparable temperatures over mesoporous Fe3O4 catalysts composed of 28–32 nm diameter nanoparticles. The Fe3O4 supports were decorated with Pd and Pt active sites and served as the local heat generators when subjected to an alternating magnetic field. For hydrogenation over Pd/Fe3O4, both heating methods gave similar liquid product selectivities, but thermogravimetric analysis–differential scanning calorimetry measurements showed no coke accumulation for the RF-heated catalyst versus 6.5 wt % for the conventionally heated catalyst. A different trend emerged when hydrogenation over Pt/Fe3O4 was performed. Compared to conventional heating, the RF increased the selectivity to stearic acid by an additional 15%. Based on these results, RF heating acting upon a magnetically susceptible nanoparticle catalyst would also be expected to positively impact systems with high coking rates, for example, nonoxidative dehydrogenations.

Hydrothermal Stable Pd/γ‐Al2O3 @PA for Selective Conversion of Glutamic Acid to Bio‐Based 2‐Pyrrolidone

AbstractGlutamic acid conversion to 2‐pyrrolidone provides significant effort in recycling nitrogen from nitrogen‐rich waste streams, particularly protein waste. Catalysts with good performance for this reaction have been suffered with unstableness and the disability in controlling the product selectivity. Here, by modifying the support with H3PO4 (PA), we got stable Pd/γ‐Al2O3 @PA catalyst, which not only enhanced 2‐pyrrolidone production from glutamic acid hydrothermal conversion, but more importantly, increased product selectivity by surface Brønsted acid sites. This study offered a robust and economic strategy to stabilize metal oxide‐supported catalysts, and could lead to additional merits in controlling the product selectivity by modulating the near‐surface environment.

Engineering of β-mannanase from Aspergillus niger to increase product selectivity towards medium chain length mannooligosaccharides

Mannooligosaccharides (MOSs) are one of the most commonly used biomass-derived feed additives. The effectiveness of MOS varies with the length of oligosaccharides, medium length MOSs such as mannotetraose and mannopentaose being the most efficient. This study aims at improving specificity of β-mannanase from Aspergillus niger toward the desirable product size through rational-based enzyme engineering. Tyr 42 and Tyr 132 were mutated to Gly to extend the substrate binding site, allowing higher molecular weight MOS to non-catalytically bind to the enzyme. Hydrolysis product content was analyzed by high-performance anion-exchange chromatography with pulsed amperometric detection. Instead of mannobiose, the enzyme variants yielded mannotriose and mannotetraose as the major products, followed by mannobiose and mannopentaose. Overall, 42% improvement in production yield of highly active mannotetraose and mannopentaose was achieved. This validates the use of engineered β-mannanase to selectively produce larger MOS, making them promising candidates for large-scale MOS enzymatic production process.

Large eddy simulation of tubular reactors with spherical dimples

Spherical dimples are implemented in heat exchanger channels to enhance heat transfer at a low pressure drop penalty. This combination of enhanced heat transfer and low pressure drop is also valuable for reactive applications such as steam cracking as this allows to increase product selectivity and reduce fouling. Large eddy simulations (LES) show the presence of asymmetric vortex structures inside the spherical dimples if they are implemented in a tubular reactor for steam cracking. Of all investigated geometric parameters, dimple depth and phase difference between consecutive rows is seen to have the greatest impact on the flow behavior. Spherical dimples in a tube enhance heat transfer up to 43% and increase pressure drop by only 54% relative to a bare tube. Relative to a ribbed tube, spherical dimples in tubes can reduce the pressure drop by half without impacting the heat transfer capabilities of the tube. The impact of these enhancements on product yields and run length is assessed via reactive simulations, benchmarking dimpled reactors against a non-enhanced reactor and industrially applied ribbed reactors. These simulations show the superior performance of dimpled reactors: the reduced fouling allows to increase the run length by up to 40% without a significant impact on product selectivities.

Enhanced Levoglucosan Yields from the Copyrolysis of Cellulose and High-Density Polyethylene

The wide availability of biomass resources could present a sustainable and alternative feedstock to fossil fuels for the production of energy sources and platform chemicals. Fast pyrolysis is one of the simplest methods for biomass conversion, but producing value-added chemicals via fast pyrolysis is still challenging due to diverse product distributions and low product selectivity. Thermoplastics that melt at high temperatures are potential candidates to trap escaping products from biomass pyrolysis, promoting secondary cellulose pyrolysis reactions for increased product selectivity. In this work, a strategy to promote the yields of levoglucosan (LG), a potential high-value chemical from cellulose pyrolysis, is presented using molten high-density polyethylene (HDPE) for the inhibition of product escape. Cellulose and HDPE mixtures were pyrolyzed with controlled mixing patterns in a custom-made laboratory reactor to investigate the interplay between chemical kinetics and mass transfer. Our experimental re...

Reactive Distillation: Stepping Up to the Next Level of Process Intensification

Reactive distillation (RD) is an efficient process intensification technique that integrates chemical reaction and distillation in a single apparatus. The process is also known as catalytic distillation when a solid catalyst is used. RD technology has many key advantages such as reduced capital investment and significant energy savings, as it can surpass equilibrium limitations, simplify complex processes, increase product selectivity, and improve separation efficiency. However, RD is also constrained by thermodynamic requirements (related to volatility differences and heat of reaction), the need to align the reaction and distillation operating conditions, and the availability of catalysts that are active, selective, and with sufficient longevity. This paper is the first to provide an overview and insights into novel integrated reactive distillation technologies that combine RD principles with other intensified distillation technologies—e.g., dividing-wall column (DWC), cyclic distillation, HiGee distilla...

Taking Reactive Distillation to the Next Level of Process Intensification

Reactive distillation (RD) is an efficient process intensification technique that integrates catalytic chemical reaction and distillation in a single apparatus. The process is also known as catalytic distillation when a solid catalyst is used. RD technology has many key advantages such as reduced capital investment and significant energy savings, as it can surpass equilibrium limitations, simplify complex processes, increase product selectivity and improve the separation efficiency. But RD is also constrained by thermodynamic requirements (related to volatility differences and heat of reaction), overlapping of the reaction and distillation operating conditions, and the availability of catalysts that are active, selective and with sufficient longevity.This paper is the first to provide insights into novel reactive distillation technologies that combine RD principles with other intensified distillation technologies – e.g. dividing-wall columns, cyclic distillation, HiGee distillation, and heat integrated distillation column – potentially leading to new processes and applications.

Enantioselective Heck-Matsuda Arylations through Chiral Anion Phase-Transfer of Aryl Diazonium Salts.

A mild, asymmetric Heck-Matsuda reaction of five-, six- and seven-membered ring alkenes and aryl diazonium salts is presented. High yields and enantioselectivities were achieved using Pd0 and chiral anion co-catalysts, the latter functioning as a chiral anion phase-transfer (CAPT) reagent. For certain substrate classes, the chiral anion catalysts were modulated to minimize the formation of undesired by-products. More specifically, BINAM-derived phosphoric acid catalysts were shown to prevent alkene isomerization in cyclopentene and cycloheptene starting materials. DFT(B3LYP-D3) computations revealed that increased product selectivity resulted from a chiral anion dependent lowering of the activation barrier for the desired pathway.

Enantioselective Heck–Matsuda Arylations through Chiral Anion Phase‐Transfer of Aryl Diazonium Salts

AbstractA mild, asymmetric Heck–Matsuda reaction of five‐, six‐ and seven‐membered ring alkenes and aryl diazonium salts is presented. High yields and enantioselectivities were achieved using Pd0 and chiral anion co‐catalysts, the latter functioning as a chiral anion phase‐transfer (CAPT) reagent. For certain substrate classes, the chiral anion catalysts were modulated to minimize the formation of undesired by‐products. More specifically, BINAM‐derived phosphoric acid catalysts were shown to prevent alkene isomerization in cyclopentene and cycloheptene starting materials. DFT(B3LYP‐D3) computations revealed that increased product selectivity resulted from a chiral anion dependent lowering of the activation barrier for the desired pathway.

Solvent effects in acid-catalyzed biomass conversion reactions.

Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural. A solvent of particular importance is γ-valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2-propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Brønsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Brønsted acid catalysts, such as H-mordenite and H-beta.

Solvent Effects in Acid‐Catalyzed Biomass Conversion Reactions

AbstractReaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid‐catalyzed conversion of xylose into furfural. A solvent of particular importance is γ‐valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2‐propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Brønsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Brønsted acid catalysts, such as H‐mordenite and H‐beta.

High selectivity of erythritol production from glycerol by Yarrowia lipolytica

The effect of different vitamins and nitrogen sources on the yield, productivity and selectivity of erythritol production from glycerol in batch and fed-batch cultures by Yarrowia lipolytica Wratislavia K1 strain was examined in the study.Thiamine was a vitamin necessary for efficient erythritol production and the yeast extract (YE) turned out to be its best source. The YE was additionally a very good source of nitrogen in this process. Erythritol production may be efficient in the media containing only yeast extract and crude glycerol. The application of a high substrate concentration (325 kg m−3) in the fed-batch system with pulsed addition of glycerol resulted in erythritol production of 201.2 kg m−3 after 168 h of cultivation. The mass fraction of by-products, such as other polyols and organic acids, did not exceed 10%. The study showed that by-products formation could be significantly reduced by the addition of a nitrogen source after glycerol depletion from the media. Wratislavia K1 strain does not utilize erythritol in the presence of other carbon sources and this feature was used in order to increase product selectivity up to 99.7% and protein content in yeast biomass up to 28.7%. The factors determining the use of biomass as animal feed, i.e. protein concentration and presence of metal ions, were discussed as well.

TAP Study of Adsorption and Diffusion of 2,2,4-Trimenthylpentane and 2,5-Dimethylhexane on β and USY Zeolites

The dimensionless equilibrium constant, apparent heats of adsorption, intraparticle diffusivities, and activation energies are determined under high vacuum conditions for 2,2,4-trimethylpentane and 2,5-dimethylhexane. These are representative of the products formed in the alkylation process of isobutane–butene mixtures on solid acid catalysts such as β and USY zeolites. It is observed that in the straight and zigzag channels of β zeolites, dimethyl-branched C8 isoalkane is strongly adsorbed and diffuses at a slower rate in comparison to trimethyl-branched C8 isoalkane. In contrast, in the super cages of USY zeolites, both C8 isoalkanes demonstrate similar sorption and transport properties. On the basis of this understanding, it is concluded that the ideal solid acid catalyst for alkylation processes requires super cages of USY zeolite rather than zigzag channels of β-zeolites in order to increase product selectivity, decrease catalyst deactivation, and decrease the energy requirement for regeneration.

Versatility of a new bioinorganic catalyst: Palladized cells of Desulfovibrio desulfuricans and application to dehalogenation of flame retardant materials

The versatility and reaction specificity of a novel bioinorganic catalyst is demonstrated in various reactions. Palladized cells (bioPd) of the sulphate‐reducing bacterium Desulfovibrio desulfuricans showed an increased product selectivity and a catalytic activity comparable to a commercial Pd catalyst in several industrially relevant hydrogenations and hydrogenolyses (reductive dehalogenations). The ability of palladized cells to promote the reductive debromination of a polybrominated diphenyl ether (PBDE #47) is demonstrated, although chemically reduced Pd(II) and commercial Pd(0) were more effective debromination agents. Polybrominated diphenyl ethers are being supplanted as flame retardants by other compounds, e.g. tris(chloroisopropyl)phosphate (TCPP), the concentration of which was seen to increase ∼10‐fold in groundwater samples between 2000 and 2004. BioPd dechlorinated TCPP in groundwater samples with >90% recovery of free chloride ion, and was five times more effective than using commercial Pd(0) catalyst. Examination of the spent groundwater using 31P NMR showed a phosphorus species novel to the bioPd‐treated solution, which was not evident in a commercial reference sample of TCPP.

Confinement effects on product selectivity in the pyrolysis of phenethyl phenyl ether in mesoporous silica

Pyrolysis of phenethyl phenyl ether confined in mesoporous silicas by covalent grafting results in significantly increased product selectivity compared with fluid phases.

Expression, purification, and characterization of recombinant amorpha-4,11-diene synthase from Artemisia annua L.

A cDNA clone encoding amorpha-4,11-diene synthase from Artemisia annua was subcloned into a bacterial expression vector in frame with a His 6-tag. Recombinant amorpha-4,11-diene synthase was produced in Escherichia coli and purified to apparent homogeneity. The enzyme showed pH optimum at pH 6.5, and a minimum at pH 7.5. Substantial activity was observed in the presence of Mg 2+, Mn 2+ or Co 2+ as cofactor. The enzyme exhibits a low activity in the presence of Ni 2+ and essentially no activity with Cu 2+ or Zn 2+. The sesquiterpenoids produced from farnesyl diphosphate in the presence of Mg 2+ were analyzed by GC-MS. In addition to amorpha-4,11-diene, 15 sesquiterpenoids were produced. Only small quantitative differences in product pattern were observed at pH 6.5, 7.5, or 9.5. Amorpha-4,11-diene synthase showed significant increased product selectivity in the presence of Mn 2+ or Co 2+. K m for farnesyl diphosphate was 3.3, 8.0, and 0.7 μM in the presence of Mg 2+, Mn 2+ or Co 2+, respectively. The corresponding k cat-values were 6.8, 15.0, and 1.3 × 10 −3 s −1, respectively. K m and k cat for geranyl diphosphate were 16.9 μM and 7.0 × 10 −4 s −1, respectively, at pH 6.5, in the presence of Mn 2+.

Catalytic membranes: alkene dimerisation by means of acidic porous thin-film composite membranes

Dimerisation of isobutene is of increasing interest to substitute oxygenated products such as MTBE or the like as fuel additives. Catalysts applied in commercial alkylation plants, e.g., hydrofluoric and sulfuric acid may be replaced by less harmful solid catalysts, for example by solid heteropolyacids (“super” acids) or polymeric sulfonic acids. To overcome decrease in catalyst performance by time and to increase product selectivity a membrane reactor approach is suggested and first successful results are presented.