Thermodynamic Study of One-step Production from Isobutene to Methyl Methacrylate

Methyl methacrylate (MMA) has emerged as an essential industrial monomer. However, the toxic by-production and shortage supply of MMA in the global market has gained great attention. Herein, a one-step synthesis to produce MMA from isobutene via a direct oxidative esterification process has been demonstrated to curb the aforementioned downsides. Thermodynamic analysis via Gibbs free energy minimization method proved the feasibility of this route via the equilibrium constant. Despite tert-butanol and isobutane showed higher equilibrium constant than isobutene, they should be avoided. Isobutane is highly flammable while the precursor of tert-butanol is exorbitant. Thus, isobutene was selected for the equilibrium compositions screening. Isobutene conversion was 90% and 15% MMA yield at 700 °C and IBN: O2: MeOH ratio with 1:7:1. This route is mainly limited by the generation of side reactions from the reaction of CH3OH and O2. By varying the feedstock ratio at 1:2:1, the MMA yield increased to ~25%. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Effective catalytic deoxygenation of palm fatty acid distillate for green diesel production under hydrogen-free atmosphere over bimetallic catalyst CoMo supported on activated carbon

Palm fatty acid distillate (PFAD) is considered as an inedible and renewable feedstock for the production of green diesel. In the current study, green diesel was successfully synthesised via catalytic deoxygenation of PFAD in an environment free of H2 using a mesoporous activated carbon (AC) supported CoMo catalyst with various molybdenum (Mo) concentrations (5–20 wt%). Based on the study results, bimetallic catalyst Co10Mo10/AC formulation exhibited excellent catalytic performance with 92% hydrocarbon components (C8-C20) yield and 89% selectivity for n-(C15 + C17) with a total acid number of 24 mg KOH mg−1 . Based on a comparison study with various supports (AC, γ-Al2O3, TiO2), the AC-supported CoMo catalyst showed higher deoxygenation activity than both Co10Mo10/γ-Al2O3 and Co10Mo10/TiO2 owing to the super acid-base sites as a result of synergism between the CoMo and AC support. The Co10Mo10/AC catalyst demonstrated excellent stability during the study as it maintained the hydrocarbon components yield and selectivity of n-(C15 + C17) > 80% until the sixth run

Potassium-modified bifunctional MgAl-SBA-15 for aldol condensation of furfural and acetone

The aldol condensation of furfural and acetone followed by hydrodeoxygenation into bio-jet fuel range alkanes and bio-polyester diols has attracted intensive interest in recent years. Such sequential reactions require a careful tailoring of one or more catalysts consisting of metal and acid–base active sites that can efficiently promote the two step cascade aldol condensation and hydrodeoxygenation. Here, we have begun developing a prominent base catalyst for mild aldol condensation of furfural and acetone by synthesizing acid–base bifunctional MgAl-SBA-15 and further modifying it with potassium. The catalyst with the highest basic site loading of 0.27 mmol g−1 showed a furfural conversion of 83% and 99% total selectivity to products comprising 54% 4-(2-furyl)-4-hydroxy-butan-2-one (FAc-OH, a C8 alcohol intermediate) and 23% of each 4-(2-furyl)-3-buten-2-one (FAc) and 1,4-pentadiene-3-one,1,5-di-2-furanyl (F2Ac) (C8 and C13 aldol condensation products, respectively) after 3 hours of reaction, at 50 °C. Though a higher loading of potassium causes severe blockages of mesopores and inaccessible acid sites, the catalyst could still be regenerated by open-air calcination and be re-used for considerable cycles with fair catalytic performances. Overall, the present study can be the stepping stone for future investigations on further tuning of non-interfering active sites in SBA-15 to promote an efficient one-pot transformation of furfural and acetone via the two-step cascade aldol condensation and hydrodeoxygenation

Chemoenzymatic epoxidation of alkenes and reusability study of the phenylacetic acid

Here, we focused on a simple enzymatic epoxidation of alkenes using lipase and phenylacetic acid. The immobilised Candida antarctica lipase B, Novozym 435 was used to catalyse the formation of peroxy acid instantly from hydrogen peroxide (H2O2) and phenylacetic acid. The peroxy phenylacetic acid generated was then utilised directly for in situ oxidation of alkenes. A variety of alkenes were oxidised with this system, resulting in 75–99% yield of the respective epoxides. On the other hand, the phenylacetic acid was recovered from the reaction media and reused for more epoxidation. Interestingly, the waste phenylacetic acid had the ability to be reused for epoxidation of the 1-nonene to 1-nonene oxide, giving an excellent yield of 90%

Catalytic deoxygenation by H2-free single-step conversion of free fatty acid feedstock over a Co-Ag carbon-based catalyst for green diesel production

A family of activated carbon-supported Co-Ag catalysts, synthesised through incipient wetness impregnation, have been evaluated for the deoxygenation of palm fatty acid distillate (PFAD) and inedible feedstocks (jatropha oil and waste cooking oil) to green diesel. High deoxygenation efficiency and conversion of PFAD to hydrocarbon liquid products through decarboxylation/decarbonylation (deCOx) is observed, with Co(10wt.%)-Ag(5− 20wt.%)/AC exhibiting the greatest hydrocarbon (C8–C20) fractions yield of 92 % and 95 % (C15+C17) selectivity after 120 min reaction at 350 ◦C. These results suggested the synergistic effect between the active metals, Co-Ag, and the activated carbon support, creating acid-base Bronsted ¨ sites, which significantly facilitated the selective deCOx pathway of the fatty acid. The catalyst Co(10wt.%)-Ag(10wt.%)/AC was capable of deoxygenation the PFAD over eight cycles. Thus, it can be believed a potentially promising catalyst for the production of green diesel, at the same time providing economic opportunities and added value to the palm oil industry

Synthesis of hierarchical nanozeolites beta and ZSM-5 for green diesel production via hydrodeoxygenation

The application of the conventional zeolites has been limited due to its large crystal size (micrometer) and also due to the microporosity (size < 2nm). Hence, this study has been conducted to produce enhanced nanozeolites to overcome the above mentioned limitations. Herein, two microporous nanozeolites namely Beta and ZSM-5 were synthesized via hydrothermal method. Moreover, the enhanced hierarchical nanozeolites have been produced via a green solvothermal approach with the following attributes such as narrow particle size distribution and appropriate mesopores. The synthesis was based on reducing the growth of zeolite crystals by surface silanization of zeolitic seeds using organosilane (hexadecyltrimethoxysilane) as a growth inhibitor. The activities of these nanozeolites and hierarchical nanozeolites were evaluated with catalytic hydroprocessing of oleic acid to green diesel by incorporating Ni metals on these supports. Moreover, extensive characterizations and initial rate investigation were conducted to determine the nature of acid sites and their structuralfunctional relationship in selective hydrodeoxygenation (HDO) of octanoic acid. The results showed hydrothermally synthesized nanozeolites were made of globular aggregates with broader particle size distributions (48-1273 nm for zeolite Beta) and (60-135 nm for zeolite ZSM-5). A much smaller and narrower distributions of globular aggregates of hierarchical nanozeolites are formed using solvothermal approach with sizes of 65–120 nm (for Beta using acetone) and 30-100 nm (for ZSM-5 using 1-decanol). These globular aggregates are actually made by quite smaller primary nanounits ranging 4–11 nm size. The hierarchical nanozeolites exhibited secondary porosity, especially larger mesopores found in zeolite Beta (with pore diameter 8.1 nm) due to efficient functionalization of HDTM in polar solvent environment (acetone). Whereas, moderate mesopores observed in zeolite ZSM-5 (with pore diameter 7.8 nm) caused by the alkoxylation of alcohol based solvent (1-decanol). Catalytic hydroprocessing of oleic acid pointed out higher yields of 60% (consisting of straight and isomeric alkanes C18 and C17) obtained over the microporous nanozeolites than hierarchical nanozeolites at 350 ◦C and 50 bar pressure. This is due to high surface activities demonstrated by the larger external surface areas of microporous nanozeolites. In contrast, the recyclability test of catalysts revealed that hierarchical nanozeolites minimized catalyst deactivation as they were capable of retaining their activities, over 40% (for HZSM-5) and 20% (for HBEA) yields even regenerated after four cycles. As for the initial rate study, all the Ni/zeolite catalysts exhibited higher selectivity towards the octane over the heptane, indicating conversion of octanoic acid occurred preferably via HDO than decarbonylation (DCN) route. The selectivity of the HDO pathway was strongly influence by the Bronsted acid sites of the zeolites. The initial rate studies revealed small Ni metal particles and it’s highly dispersibility over support facilitate high initial catalytic activity. The fatty acid substrate can be quantitatively hydrodeoxgenated to alkanes by cascade reaction on bifunctional catalysts based on Ni and an acidic zeolite. The findings of this study discovered more effective and benign way of producing nanozeolites with high external surface area and hierarchical porosity that provide remarkable HDO activity and better catalyst stability as compared to other commercial support catalysts

Chemo-enzymatic epoxidation of 1-nonene, 1-heptene and styrene

In view of the emerging importance of enzyme as a promising biocatalyst in fine organic synthesis, we focused on the synthesis of epoxides for their potential applications in chiral synthesis, including asymmetric synthesis and optical resolution of racemates. Epoxides are increasingly used as intermediates in many industrial processes and have wide applications in food, polymer and pharmaceutical formulations due to their excellent ability to facilitate ring opening reactions to various desirable functional groups. The enzymatic synthesis of epoxides has received much attention for its clean production due to its high-regioselectivity and low production of by-products. Furthermore, hydrogen peroxide (H2O2) as green oxidant and mild operating temperature, hence, low energy requirement, are becoming two important advantages of this enzymatic reaction. Herein, we describe an improved enzyme-facilitated epoxidation of a simple alkene (1-nonene) using a conventional water bath shaker. The lipase was used to catalyse the formation of peroxy acids instantly from H2O2 and various perhydrolysis substrates. The peroxy acid generated was then utilised directly for in-situ oxidation of 1-nonene to 1-nonene oxide. Various reaction parameters affecting the synthesis of epoxide, including the nature of peroxy acids, organic solvents, enzyme’s sources, enzyme concentrations, reaction temperatures, initial concentrations and rate additions of the H2O2, stirring rates (rpm), and amounts of H2O2 and peroxy acid, were investigated. Highest conversion was achieved using phenylacetic acid as an oxygen carrier. 1-nonene was converted most efficiently with maximum yield of 97% by Novozym 435, an immobilised Candida antarctica lipase B (CALB) and chloroform as reaction media. A minimum amount (1.4% w/w, 19 mg) of Novozym 435 was needed to maintain the catalytic activity (190.0 Ug-1). The highest yield was successfully obtained within 12 h reaction time at optimal synthesis conditions (35°C, 4.4 mmol of H2O2 (30%) in a single step addition, stirring rate 250 rpm and 8.8 mmol of phenylacetic acid). Subsequently, the optimised conditions were employed for the epoxidation of an array of aliphatic (1-heptene) and aromatic (styrene) alkenes which gave 94% to 99% yield and quantitative purity. In addition, a simple and rapid gas chromatography – mass spectrometry (GC-MS) selective ion monitoring (SIM) method was developed using an HP-5ms column for determining the epoxide yields. For 1-nonene oxide, the method was found to be linear in the range of 29.9 - 298.8 mg/L with R2 = 0.9960

Optimization of lipase-mediated synthesis of 1-nonene oxide using phenylacetic acid and hydrogen peroxide

Herein, an efficient epoxidation of 1-nonene is described. In a simple epoxidation system, commercially available Novozym 435, an immobilized Candida antarctica lipase B, and hydrogen peroxide (H2O2) were utilized to facilitate the in situ oxidation of phenylacetic acid to the corresponding peroxy acid which then reacted with 1-nonene to give 1-nonene oxide with high yield and selectivity. The aliphatic terminal alkene was epoxidised efficiently in chloroform to give an excellent yield (97%–99%) under the optimum reaction conditions, including temperature (35 °C), initial H2O2 concentration (30%), H2O2 amount (4.4 mmol), H2O2 addition rate (one step), acid amount (8.8 mmol), and stirring speed (250 rpm). Interestingly, the enzyme was stable under the single-step addition of H2O2 with a catalytic activity of 190.0 Ug−1. The entire epoxidation process was carried out within 12 h using a conventional water bath shaker

Mercerizing Extraction and Physicochemical Characterizations of Lignocellulosic Fiber from the Leaf Waste of Mikania micrantha Kunth ex H.B.K

Invasive plants can grow rampantly and spread fast in large amount, which can be economically invoked for generating value-added products. In this study, lignocellulosic fiber was extracted from the leaf waste of a luxuriant invasive plant, Mikania micrantha Kunth-ex H.B.K. by mercerization process. After the alkaline treatment, the lignocellulosic biomass remained at 38.54% resulting from the large removal of extractive impurities. The lignocellulosic fraction in the mercerized leaf fiber was improved from 56.59% to 83.96%. The chemical composition analysis showed the cellulose fraction was increased by 11.17% while the hemicellulose and lignin fractions were found to be decreased by 4.89% and 6.28%, respectively. The FT-IR and TGA results further affirmed the change in chemical composition of the lignocellulosic fiber. Furthermore, an increase in cellulose fraction raised the fiber crystallinity index from 11.0% to 36.7%. The SEM study revealed that the surface morphology of lignocellulosic fiber changed from smooth surface into rough corrugated ridges, which affirmed the increase in crystallinity, resulting from the removal of wrapped cementing materials. In subsequent, the lignocellulosic fiber exhibited more pervious to water attack with an increase in moisture absorption from 119.22% to 410.19%

Photocatalytic remediation of organic waste over Keggin-based polyoxometalate materials: A review

Photocatalytic remediation of industrial water pollution has courted intense attention lately due to its touted green approach. In this respect, Keggin-based polyoxometalates (POMs) as green solid acids in photocatalytic reaction possess superior qualities, viz. unique photoinduced charge-transfer properties, strong photooxidative-photoreductive ability, high chemical and thermal stability, and so forth. Unfortunately, it suffers from a large bandgap energy, low specific surface area, low recoverability, and scarce utilization in narrow absorption range. Therefore, the pollutant degradation performance is not satisfactory. Consequently, multifarious research to enhance the photocatalytic performance of Keggin-based POMs were reported, viz. via novel modifications and functionalizations through a variety of materials, inclusive of, inter alia, metal oxides, transition metals, noble metals, and others. In order to advocate this emerging technology, current review work provides a systematic overview on recent advancement, initiated from the strategized synthetic methods, followed by hierarchical enhancement and intensification process, at the same time emphasizes on the fundamental working principles of Keggin-based POM nanocomposites. By reviewing and summarizing the efforts adopted global-wide, this review is ended with providing useful outlooks for future studies. It is also anticipated to shed light on producing Keggin-based POM nanocomposites with breakthrough visible- and solar-light-driven photocatalytic performance against recalcitrant organic waste