Yield Of Oligomers Research Articles

Fractionation of High-Yield Noncondensed Lignin and Glucan Oligomers from Lignocellulose in a Novel Biphasic System.

Effective fractionation of lignocellulose into hemicellulose, cellulose, and lignin is the precondition for full-component valorization. Generally, harsh reaction conditions are used to improve fractionation efficiency, which leads to severe lignin condensation and inhibits its value-added applications. To address this issue, a novel biphasic system consisting of molten salt hydrates (MSHs) and n-butanol was developed for birch fractionation. After the removal of hemicellulose in dilute acid, the solid residue composed of cellulose and lignin was carried out in biphasic system conversion. Cellulose was selectively converted into 73.3% yield of glucan oligomers and 16.8% glucose in the MSH phase, while lignin was in situ-extracted into the n-butanol phase with a high yield of 98.1%. Mechanism studies revealed that the in situ extraction together with Cα-OH group modification by n-butanol synchronously protected lignin β-O-4 linkages from cleavage, resulting in a high β-O-4 content of 53.7%, indicating that 87.7% of β-O-4 linkages in birch has been preserved. After depolymerization, a promising monophenol yield of 22.4% was obtained, which was 81.5% of the theoretical maximum monophenol yield obtained from birch. This fractionation strategy can also be used in softwood and herbaceous, showing a splendid separation efficiency as well as a high yield of noncondensed lignin production.

Synthesis of sustainable aviation fuels via (co–)oligomerization of light olefins

Within this study, the (co–)oligomerization of methanol-based olefins in the C2-4 range was investigated. The main objective was to increase the yield of oligomers with carbon chain lengths in the range of kerosene (C9-16). Commercially available mesoporous amorphous mixed silicon-aluminum oxides, optionally modified with nickel species, were applied as catalysts. Initially, single olefin feeds were employed, i.e. homo-oligomerization reactions of pure propylene and pure 1-butylene were studied at 120 °C and 32 bar olefin partial pressure, respectively. The co-oligomerization of olefin mixtures (C3+4 and C2+3+4), which can be obtained in Methanol-to-Olefins (MtO) processes, yields product mixtures with reduced selectivities to specific chain lengths. However, selectivities to kerosene-like olefins up to 85 % have been achieved and the main side product is gasoline. Investigations with varying reaction conditions reveal comparable effects as in the case of homo-oligomerization. The use of nickel-free catalysts resulted in the highest selectivities of kerosene-like olefins, but no ethylene was converted. The negative effects of nickel catalysts on fuel quality can be compensated by two consecutive catalyst beds, the first catalyst bed with a nickel-loaded silicon-aluminum oxide for ethylene conversion followed by a catalyst bed of neat silicon-aluminum oxide for the synthesis of highly branched, long chain oligomers. The reaction network for olefin oligomerization reactions is depicted, which can be simplified remarkably in the case of catalysts without nickel. A long-term experiment lasting for more than 200 h was conducted revealing a deactivation of the acid sites of the catalysts, but also the possibility of reactivation. Selectivity to kerosene-like olefins remained above 63 % and fuel characterization showed that the resulting kerosene fraction will be suitable for blending with conventional fuels.

Continuous-Flow Microreactor Accelerates Molecular Collisions for Lignin Depolymerization to Phenolic Monomers and Oligomers.

Effective depolymerization of lignin is the most important step for its comprehensive utilization. So far, most of the studies on depolymerization of lignin focused on batch processing, whereas only a few studies relied on the microreactor. In this study, we developed a continuous-flow microreactor for depolymerization of lignin into monomeric and oligomeric compounds. The yields of monomers and oligomers can be adjusted by varying the temperature, pressure, residence time, NaOH dosage, and solvent. Under optimized conditions, the lignin conversion rate was 77.73 wt %, and the monomer yield was 13.26 wt %, with 77.81% being phenolic compounds. In addition, comparative characterizations on the raw lignin and products demonstrated that the oil products were mainly composed of phenolic tetramers and trimers, and the effective cleavage of the β-O-4 linkage of S-type lignin was responsible for the high yield of 2,6-dimethoxyphenol. It indicated that raw lignin could be effectively depolymerized continuously using the continuous-flow microreactor, and it will be a new strategy for comprehensive utilization of lignin to produce fine-chemical intermediates.

Controlled Glycolysis of Poly(ethylene terephthalate) to Oligomers under Microwave Irradiation Using Antimony(III) Oxide.

We report here the production of higher-order oligomers from the glycolysis of poly(ethylene terephthalate) (PET) by using microwave irradiation in a controlled fashion, instead of its fully glycolyzed product, bis(2-hydroxyethyl)terephthalate (BHET). We show that different catalysts can generate either BHET as the ultimate glycolysis product or higher oligomers of PET under microwave irradiation. Depolymerization of waste PET with an average degree of polymerization (DP) of 417 from water bottles was performed in the presence of 0.25 wt % antimony(III) oxide (Sb2O3) as the catalyst at 240 °C and 400 W microwave power, resulting in an oligomer yield of 96.7% with an average DP of 37. Under these conditions, the conversion of PET to oligomers reached 100% in only 5 min at 240 °C (with a 10 min ramping time) and with a ethylene glycol to PET weight ratio of 2.5. In comparison, under the same reaction conditions, 0.04 wt % of zinc acetate (Zn(OAc)2), a well-known catalyst for PET glycolysis, produces only the BHET monomer in 96.3% yield. Our results demonstrated that by using Sb2O3, the same catalyst that is used extensively for PET synthesis from BHET, under microwave irradiation, the PET glycolysis can be controlled to produce higher PET oligomers as an alternative for a complete chemical depolymerization to the BHET monomer. These oligomers are more suitable for being used as additives for many applications and to produce high-quality second-generation products, including regenerated PET.

Controlling PET oligomers vs monomers via microwave-induced heating and swelling

The production of polyethylene terephthalate (PET) bottles and fibers, and their subsequent mismanagement, have created an urgent need to develop strategies to handle the resulting waste. Here, glycolysis of PET using manganese oxide catalysts under microwave-assisted heating is demonstrated to form oligomers and the monomer bis(2-hydroxyethyl) terephthalate (BHET) at moderate conditions. Higher surface area catalysts achieve faster overall rates of depolymerization to the monomer. Oligomers form homogeneously and depolymerize to monomers over manganese oxide. The polymer-to-solvent ratio and reaction temperature affect the overall oligomer yield. The swelling of PET, caused by the diffusion of ethylene glycol into the polymer matrix, causes the dissolution of the PET to form oligomers. Oligomers are characterized and show similar physical properties to the starting PET despite having 1/20th of the molecular weight.

Heterocene Catalysts and Reaction Temperature Gradient in Dec-1-ene Oligomerization for the Production of Low Viscosity PAO Base Stocks

Hydrogenated oligomers of higher α-olefins (primarily, dec-1-ene) with uniform structure represent high-quality poly-α-olefin oil (PAO) base stocks. High yields of lightweight dec-1-ene oligomers (DPn = 3–4) can be achieved by using 5,10-dihydroindeno[1,2-b]indole-based zirconium ansa-complexes, “heterocenes”. Unusual catalytic behavior of heterocenes served as a starting point for the present study, during which new, more synthetically available and active heterocene precatalysts were synthesized, and a novel oligomerization method, based on a reaction temperature gradient, was developed. A gradual decrease of the oligomerization temperature as dec-1-ene was consumed resulted in decreased dimer formation (down to 10%) and increased oligomer yields (up to 84%). After hydrogenation, low- and medium-viscosity PAO base oils with uniform structure and high viscosity indexes were obtained.

Acid-promoted lignin reductive depolymerization under mild conditions via a condensation minimizing approach: From organosolv lignin to woody biomass

Lignin reductive depolymerization into phenolic monomers is a critical step for the scale-conversion of lignin into liquid fuels but its scale-up is still compromised by harsh reaction conditions (e.g. high temperature and high external H2 pressure) and inevitable condensations. Herein, we present an efficient acid-promoted reductive depolymerization of lignin over Ni/C without external H2 via a condensation minimizing approach using lignin monomer analogue (p-hydroxybenzyl alcohol, HBA) as the capping agent. With addition of 0.4 % H2SO4 and 0.4 mmol/g HBA, 20.42 % of phenolic monomer yield along with 31.70 % oligomer yield was achieved at 160 °C while the condensated/undepolymerized lignin yield was less than 10 %. HBA inhibited the acid-induced condensation by competitive reaction with the nucleophilic C6 in guaiacyl unit. When the approach was applied in lignin-first reductive fractionation of poplar, 32.72 % of phenolic monomer yield and 76.59 % of delignification were achieved at 160 °C in the presence of acid and HBA. Additionally, xylan was dissociated concurrently owing to the acid-catalyzed hydrolysis, resulting in a cellulose-rich solid residue. Consequently, this work proposes an efficient approach for lignin reductive depolymerization and lignin-first biomass fractionation under mild conditions through the synergism of acid and capping agent.

Kraft pulping of softwood chips with mild hot water pre-hydrolysis to understand the effects of wood chip thickness

Hemicelluloses consume alkali during kraft pulping and dissolve in the black liquor as a low energy fuel. Acidic pre-hydrolysis of softwood chips removes hemicelluloses but preserves cellulose content prior to pulping. This study compared mild pre-hydrolysis (140 °C) kraft pulping with conventional kraft pulping of commercial softwood chips at two H-factors for wood chips with thickness ranging from less than 2 mm to over 6 mm. The chip thickness less than 2 mm increased hemicelluloses oligomer yield and showed little influence on pulp fiber yield. However, the kraft pulp fiber length decreased 5.6%. Kappa number and fiber reject increased dramatically when chip thickness was greater than 6 mm. The detailed compositional analysis of kraft pulp and fiber quality analysis indicate that pre-hydrolysis followed by kraft pulping enhanced delignification with limited reduction of fiber length and width, and increased kinks. Strategic considerations for the integration of pre-hydrolysis into kraft pulping for future biorefineries were outlined.

Stable Oligomer Formation from Lignin by Pyrolysis of Softwood in an Aprotic Solvent with a Hydrogen Donor.

Pyrolysis of Japanese cedar wood in diphenoxybenzene (an aprotic solvent) with a hydrogen donor was investigated between 270–380 °C. Under these conditions, re‐condensation via radical and quinone methide intermediates was efficiently suppressed and a thermally stable oligomer was obtained. The oligomer was stable even after the treatment time was extended. Yields of lignin‐derived products at 270 °C were limited to approximately 20 wt %, but increased to >80 wt % (lignin basis) at the higher temperatures. The oligomer yield increased directly with the extent of the cellulose degradation at 350 °C. Based on the NMR analysis results, the ether bonds in lignin were largely cleaved, but condensed linkages such as β‐aryl and β‐β and 5‐5’ types remained. The γ‐hydroxypropyl group was identified as a typical side chain, formed by hydrogenation of the double bond of a coniferyl alcohol‐type structure.

A competetive way to low-viscosity PAO base stocks via heterocene-catalyzed oligomerization of dec-1-ene

Hydrogenated oligomers of higher α-olefins (primarily, dec-1-ene) represent base stocks for high-quality polyolefin oils (PAOs), transmission fluids, lubricants and greases. Competitive advantages of zirconocene catalysts in oligomerization of α-olefins have been already demonstrated and industrially implemented for higher oligomers. However, the problem of the selective synthesis of α-olefin oligomers that have degree of polymerization (DPn) 3 and 4, remains unresolved. A series of –CH2CH2– bridged ansa-zirconocenes derived from 5,10-dihydroindeno[1,2-b]indole, 'heterocenes' Zr4–Zr6, were synthesized and characterized by NMR spectroscopy and X-ray diffraction (XRD) analysis. New complexes Zr4–Zr6 and known –SiMe2– bridged ansa-heterocenes Zr1–Zr3 were investigated in oligomerization of dec-1-ene using MMAO-12 or [PhNMe2H][B(C6F5)4] activators. In the atmosphere of molecular hydrogen, at [dec-1-ene]/[Zr] ratios up to 4·105, rac-forms Zr4r–Zr6r provided more than 85% yields of dec-1-ene oligomers without skeletal rearrangements. In some experiments, at least 50% yields of lightweight oligomers (DPn=3–4) were achieved. After activation of Zr6r by TIBA and [PhNMe2H][B(C6F5)4] and completion of dec-1-ene oligomerization, we isolated new cationic complex Zr6r-Al containing Zr-(μ-Cl)2-Al fragment, as confirmed by XRD. Zr6r-Al alone was inactive against dec-1-ene, but after addition of TIBA oligomerization started. Due to uniform molecular structure of oligomers, complete catalytic hydrogenation of oligo(dec-1-ene)s was conducted using Ni/Al2O3 catalyst under mild conditions (150°C, 3 h, 20 bar). Hydrogenated dec-1-ene oligomers turned out to be high-quality PAO base stocks far exceeding industrial dec-1-ene PAOs in terms of viscosity characteristics.

Oligomerization of C9 hydrocarbon fraction initiated by amino peroxides with cyclic substitute

This paper investigates the production of hydrocarbon resins by oligomerization in solution and suspension of the C9 fraction of by-products from oil refining. The disadvantage of existing technologies for oligomers by free radical oligomerization is the use of high reaction temperatures. The application of N-replaced amino peroxides as low-temperature initiators and a suspension oligomerization technology can reduce the temperature and duration of the reaction. The correlation between oligomerization parameters and yield and characteristics of oligomers has been established. Owing to this, it will be possible to set optimal conditions and predict the properties of the resulting products. The high values of the yield and bromine number correlation in oligomerization in solution (–0.98 and –0.95) and suspension (–0.83 and –0.80) indicate the course of the oligomerization reaction. The main factor influencing oligomerization in solution is the reaction temperature (correlation 0.80). The softening temperature of oligomers is in the range of 349‒353 K and does not depend on the oligomerization conditions in the solution (correlation indicator 0.18). Suspension oligomerization in the studied intervals does not depend on temperature (correlation −0.08) and initiator concentration (correlation 0.40). It is proved that in the studied intervals of variables, the yield of oligomers depends on the duration of the reaction (correlation 0.88). The color indicator of suspension oligomerization products at the studied intervals varies slightly and is 20–30 mg I2/100 ml. The established optimal conditions make it possible to effectively use oil refining by-products by synthesizing light oligomers. Under the established optimal conditions, the product yield is 22.7 % with oligomerization in solution and 19.4 % with suspension oligomerization.

Chemical and Enzymatic Synthesis of Biobased Xylo-Oligosaccharides and Fermentable Sugars from Wheat Straw for Food Applications.

Xylo-oligosaccharides are sugar oligomers with 2~7 xylose units considered non-digestible fibers that can be produced from biodegradable and low-cost biomass like wheat straw. An integrated approach consisting of hydrothermal pretreatment, alkaline treatment, enzymatic treatment and the combinations thereof was applied to overcome the recalcitrance structure of the wheat straw and allow selective fractioning into fermentable sugars and xylo-oligosaccharides. The hydrolysates and processed solids were chemically characterized by High-performance liquid chromatography and Ion chromatography, and the results were expressed as function of the severity factor and statistically interpreted. The concentration of fermentable sugars (glucose, xylose, arabinose) was the highest after the combination of alkaline and enzymatic treatment with xylanase (18 g/L sugars), while xylo-oligosaccharides (xylotriose and xylotetraose) were released in lower amounts (1.33 g/L) after the same treatment. Refining experiments were carried out to obtain a purified fraction by using anion and cation exchange chromatography. The polymer adsorber resin MN-502 showed efficient removal of salts, phenols and furan derivatives. However, the xylo-oligosaccharides yields were also slightly reduced. Although still requiring further optimization of the treatments to obtain higher purified oligomer yields, the results provide information on the production of xylo-oligosaccharides and fermentable sugars from wheat straw for potential use in food applications.

Lipid Peroxidation Products HNE and ONE Promote and Stabilize Alpha-Synuclein Oligomers by Chemical Modifications.

The aggregation of α-synuclein (αSN) and increased oxidative stress leading to lipid peroxidation are pathological characteristics of Parkinson's disease (PD). Here, we report that aggregation of αSN in the presence of lipid peroxidation products 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) increases the stability and the yield of αSN oligomers (αSO). Further, we show that ONE is more efficient than HNE at inducing αSO. In addition, we demonstrate that the two αSO differ in both size and shape. ONE-αSO are smaller in size than HNE-αSO, except when they are formed at a high molar excess of aldehyde. In both monomeric and oligomeric αSN, His50 is the main target of HNE modification, and HNE-induced oligomerization is severely retarded in the mutant His50Ala αSN. In contrast, ONE-induced aggregation of His50Ala αSN occurs readily, demonstrating the different pathways for inducing αSN aggregation by HNE and ONE. Our results show different morphologies of the HNE-treated and ONE-treated αSO and different roles of His50 in their modification of αSN, but we also observe structural similarities between these αSO and the non-treated αSO, e.g., flexible C-terminus, a folded core composed of the N-terminal and NAC region. Furthermore, HNE-αSO show a similar deuterium uptake as a previously characterized oligomer formed by non-treated αSO, suggesting that the backbone conformational dynamics of their folded cores resemble one another.

Metal-alkali catalytic valorization of lignocellulose towards aromatics and small molecular alcohols and acids in a holistic approach

In this work, we developed an approach of one-pot complete catalytic conversion of woody biomass into two value product streams: lignin-derived aromatics (monomer yield of 68.54% and oligomer yield of 29.65% based on lignin mass) and (semi-)cellulose-derived small molecular alcohols (about 59.60% of biomass mass). These could be afforded by conducting lignocellulose depolymerization over metal-alkaline catalysts in a mixed n-butanol/H2O solvent system at 250 °C and 30 bar H2. In the valorization process, the homogenous mixture of n-butanol-H2O solvents extract and depolymerize both lignin and hemicellulose, while the catalysts and H2 are essential to cleave the inter-/intramolecular linkage of lignocellulose into target products. After the reaction, the phase separation of n-butanol and H2O takes place when system temperature drops below 125 °C, providing a mild and effective strategy to isolate lignin-derived aromatics (n-butanol phase) from small molecular alcohols/acids (aqueous phase). Ru/C and alkali catalysts are collected by filtration from n-butanol phase and H2O phase, respectively. Meanwhile, the effect of metal-alkali coupled catalysts facilitates the cleavage of β-O-4 linkage of lignin and increases the attainability of (semi-)cellulose-derived oligomers and the small molecular alcohols. This catalytic system provides a versatile valorization approach for biomass catalysis to bio-based chemicals.

Adsorption-Enhanced Glucan Oligomer Production from Cellulose Hydrolysis over Hyper-Cross-Linked Polymer in Molten Salt Hydrate.

Selective saccharification of cellulose into glucose is a critical step for utilization of lignocellulosic biomass. Molten salt hydrates (MSHs) have shown promising performance in selectively converting cellulose into glucose because of the high solubility of cellulose in the solvent. However, the separation of formed glucose from the MSHs is still a grand challenge. To address this issue, we developed a two-step process, where crystalline cellulose is hydrolyzed into short-chain glucan oligomers in MSHs followed by separation and subsequent hydrolysis of the formed oligomers into glucose under mild conditions. The two-step method provides an easy separation for glucan oligomers from the MSHs without sacrificing the selectivity to glucose. Application of the method for crystalline cellulose is, however, limited to a relatively low concentration, 26.2 mg/mL, because of the formation of byproducts in the MSH that facilitate oligomers degradation. In this work, reactive adsorption was employed to in situ remove the byproducts formed during cellulose hydrolysis in the MSH. It was found that hyper-cross-linked polymer (HCP) made from the polymerization of 4-vinylbenzyl chloride and divinylbenzene can selectively adsorb 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) while showing negligible sugar adsorption in both water and the MSH. With the reactive adsorption approach, byproducts including 5-HMF and LA were removed from the reaction media under reaction conditions, and their negative effects on oligomer degradation were inhibited. In the presence of the HCP, the obtained glucan oligomer concentration was enhanced from less than 54.2 to 247.1 mg mL-1 when the weight ratio of cellulose was increased to MSH from 1:60 to 1:4, exhibiting an oligomer yield of 69.5%. The HCP can be effectively separated from the reaction media by filtration and regenerated by oxidation with hydrogen peroxide. Application of reactive adsorption with HCP for cellulose hydrolysis in the MSH provides a promising method to produce glucan oligomers and glucose with an improved yield and efficiency.

Correlation between the emulsion oligomerization parameters for C9 fraction and the characteristics of hydrocarbon resins

This paper investigates the production of hydrocarbon resins by emulsion oligomerization of the С9 fraction hydrocarbons in liquid by-products of oil refining. Such oligomers have a wide range of applications as film-forming agents in paints and anti-color coatings. Emulsion oligomerization was carried out using emulsifiers of the first and second kind. The study was performed at different values of the reaction temperature of the reaction duration, the intensity of agitation; concentrations of the emulsifier; С9:water fraction ratio. The resulting products were estimated according to the following indicators: the yield, unsaturation degree, softening temperature, mean molecular weight, color. Statistical analysis was carried out, the correlation of parameters of emulsion oligomerization and the yield and characteristics of oligomers was established. Given that, it would be possible to establish the optimal conditions for emulsion oligomerization and predict the properties of the products obtained. Specifically, it was established that the yield of hydrocarbon resins does not correlate with the reaction temperature (0.15 and 0.30) and the concentration of emulsifiers (0.08 and 0.03). It was proven that in the intervals studied the variable yield of oligomers depends on the duration of the reaction (correlation 0.88 and 0.81). In the case of oligomerization in the reverse emulsion, a significant correlation with the yield is also demonstrated by agitation intensity (0.51) and a С9:water fraction ratio (0.51). That has made it possible to derive an equation of the yield multiple linear regression dependent on the most significant process parameters. The high values of the yield and bromine number correlation (0.94 and 0.93) give grounds to argue about the progress of oligomerization reaction. The relationship among the characteristics of oligomers has been confirmed. This indicates the possibility of directed adjustment of certain characteristics of hydrocarbon resins.

C9 Fraction inverse emulsion oligomerization conditions and characteristics of petroleum resins correlation

It has been studied the production of petroleum resins by low-temperature inverse emulsion oligomerization of C9 fraction of diesel fuel pyrolysis liquid by-products. It is established that the determining factors of the C9 fraction of the inverse emulsion oligomerization are the following: reaction time, emulsifier concentration and phase ratio. Yield and physicochemical characteristics of oligomers сorrelations were established. Multiple linear regression of oligomer yield depends on the main significant parameters of the fraction C9 inverse emulsion oligomerization is proposed.

Enzymatic Polymerization of Dihydroquercetin (Taxifolin) in Betaine-Based Deep Eutectic Solvent and Product Characterization

Deep eutectic solvents (DESs) are an alternative to conventional organic solvents in various biocatalytic reactions. Meanwhile, there have been few studies reporting on synthetic reactions in DESs or DES-containing mixtures involving oxidoreductases. In this work, we have studied the effects of several DESs based on betaine as the acceptor of hydrogen bonds on the catalytic activity and stability of laccase from the basidial fungus Trametes hirsuta and performed enzymatic polymerization of the flavonoid dihydroquercetin (DHQ, taxifolin) in a DES–buffer mixture containing 60 vol.% of betaine-glycerol DES (molar ratio 1:2). The use of the laccase redox mediator TEMPO enabled an increased yield of DHQ oligomers (oligoDHQ), with a number average molecular weight of 1800 g mol−1 and a polydispersity index of 1.09. The structure of the synthesized product was studied using different physicochemical methods. NMR spectroscopy showed that oligoDHQ had a linear structure with an average chain length of 6 monomers. A scheme for enzymatic polymerization of DHQ in a DES–buffer mixture was also proposed.

Homogeneously catalyzed depolymerization of lignin from organosolv medium: Characterization, optimization, and minimization of coke formation

AbstractThis study focused on maximizing yields of oligomeric and monomeric products while minimizing coke formation in the depolymerization of lignin from an organosolv medium. A design of experiments (DoE) with temperature, time, and ethanol‐water ratio as factors was established and tested. Optimized reaction conditions were found at 185.4°C with 7.5 wt% sodium hydroxide as catalyst, an ethanol‐water ratio of 48.6% (v/v), and a residence time of 30 minutes. With these optimized parameters, maximum monomer and oligomer yields of 9.4 wt% and 86.2 wt% and minimized coke formation of 0.5 wt% were achieved. The oligomeric and monomeric products were characterized by GPC, GC‐MS, and OH‐group determination (Folin‐Ciocalteu).

Isoamylene Oligomerization over Zeolite Catalysts

The study of isoamylene oligomerization over a number of microporous zeolites\t\t\t\t\tsuch as H–Y, H–MOR, H–Beta, H–ZSM-12, and H–ZSM-5 revealed that the isoamylene\t\t\t\t\tconversion rate decreases in the following order: H–MOR > H–Y > H–Beta-40\t\t\t\t\t>> H–ZSM-12 > H–ZSM-5. The maximum yields of isoamylene oligomers were\t\t\t\t\tachieved by using H–MOR (85.0%), H–Y (80.1%), and H–Beta-40 (79.8%). The\t\t\t\t\tpredominant isoamylene oligomers are dimers regardless of the zeolite catalyst\t\t\t\t\tused. The trimer yield reaches its highest when wide-pore zeolites like H–MOR,\t\t\t\t\tH–Y, or H–Beta-40 are employed. An increase in the number of acid sites enhances\t\t\t\t\tmonomer conversion rate, oligomer yield, and oligomer molecular weight.\t\t\t\t\tConditions for producing isopentene dimers and trimers with the maximum possible\t\t\t\t\tyield were determined.