Substitution Of Phenol Research Articles

A Comparison among Lignin Modification Methods on the Properties of Lignin-Phenol-Formaldehyde Resin as Wood Adhesive.

The research aim of this work is to determine the influence of lignin modification methods on lignin–phenol–formaldehyde (LPF) adhesive properties. Thus, glyoxal (G), phenol (P), ionic liquid (IL), and maleic anhydride (MA) were used to modify lignin. The modified lignins were used for phenol substitution (50 wt%) in phenol–formaldehyde adhesives. The prepared resins were then used for the preparation of wood particleboard. These LPF resins were characterized physicochemically, namely by using standard methods to determine gel time, solids content, density, and viscosity, thus the physicochemical properties of the LPF resins synthesized. The panels dimensional stability, formaldehyde emission, bending modulus, bending strength, and internal bond (IB) strength were also measured. MA-modified lignin showed by differential scanning calorimetry (DSC) the lowest temperature of curing than the resins with non-modified lignin and modified with IL, phenolared lignin, and glyoxal. LPF resins with lignin treated with maleic anhydride presented a shorter gel time, higher viscosity, and solids content than the resins with other lignin modifications. Equally, the particleboard panels prepared with LPF resins with maleic anhydride or with ionic liquid had the lowest formaldehyde emission and the highest mechanical strength among all the synthesized resins. The dimensional stability of all panels bonded with modified lignin LPF resins presented no difference of any significance.

Catalytic Hydrodeoxygenation of Model Bio‐oils Using HZSM‐5 and Ni2P/HZM‐5 Catalysts: Comprehension of Interaction

AbstractHydrodeoxygenation (HDO) of Mixture 1 (acetic acid and phenol) and Mixture 2 (acetone, acetic acid, phenol, 4‐ethylguaiacolis, furfural, and water) as model bio‐oils was performed to investigate the interactions. Ni2P/HZSM‐5 catalysts exhibited higher activity than blank HZSM‐5. The conversion rate of acetic acid enhanced with the increase of temperature, contrary to the value of phenol due to the differential adsorption capacity on active phases. Acetone can be formed by self‐ketonization of acetic acid. Low temperatures favored esterification, while high temperatures promoted the synthesis of alkyl‐substituted phenols and aromatic hydrocarbons via mainly alkyl substitution of phenol and benzene, respectively. Two reaction networks of model bio‐oil HDO with the main reactions were proposed.

Hydrogen bond assisted anchoring transitions in nematic liquid crystals at the aqueous interface

Homeotropic alignment of liquid crystals (LCs) at the aqueous interface and their fundamental understanding is still limited known, which is a prerequisite for the development of new kinds of LC-based sensors for the detection of biomolecules in the aqueous phase. Herein, we have investigated the orientational ordering of nematic LC at LC-aqueous interface in contact with the different hydrogen bonding strength of para-substituted phenol derivatives (X; functional group attached to phenol at para position = -NO2, -CN, -Cl, -F, -CHO, -H) intending to understand how the intermolecular hydrogen bonding interactions at LC-aqueous interface amplified into supramolecular ordering in LCs. The hydrogen bonding interactions between -CN group of 5CB and -OH group of phenol derivatives lead to a change in tilt angle from planar to homeotropic ordering of 5CB molecules at LC-aqueous interface. Raman measurement of different mixtures between 5CB and para-substituted phenol derivatives have been recorded to correlate the experimental observations at the LC-aqueous interface as well as direct evidence of hydrogen bonding at the LC-aqueous interface. Density functional theory (DFT) has been used to calculate hydrogen bonding strength and charge transfer mechanism between 5CB and phenol derivatives. The orientation of LC at the aqueous interface depends on the strength of the interfacial hydrogen bonding between phenol derivatives and LC, which varies on substitution of phenol and concentration of the phenol molecules.

Investigating the formation of iodinated aromatic disinfection by-products in chlorine/phenol/iodide system

Iodinated disinfection by-products (DBPs) have been attracting great attention due to their potential high toxicity to human health. Understanding of formation mechanisms and transformation process of iodinated aromatic DBPs during the chlorination of iodide-containing water is crucial. Phenol was therefore chosen as a representative of phenolic compounds to investigate the generation of iodinated aromatic DBPs in a chlorine/phenol/iodide system. The presence of iodide in water could enhance the removal of phenol by chlorine due to higher second order rate constants of HOI with phenol than that of HOCl with phenol. Fourteen kinds of iodinated aromatic DBPs were identified, which were generated from oxidation and electrophilic substitution of phenol by HOCl and HOI. Iodinated phenolic DBPs were sources of iodinated quinone DBPs and chlorinated/iodinated phenolic DBPs. Alkaline condition favored the formation of iodinated phenolic DBPs, while acid condition favored the production of iodinated quinone DBPs. Neutral condition might be the most suitable pH condition to control the formation of iodinated aromatic DBPs. The relative concentration of almost all iodinated aromatic DBPs first increased and then decreased with time, indicating iodinated aromatic DBPs might be further converted into halogenated aliphatic DBPs during the chlorination. This research provides a research basis for the removal of phenol in water.

Techno‐economic analysis of novolac resin production by partial substitution of petroleum‐derived phenol with bio‐oil phenol

AbstractNovolac resins are produced by reacting phenol and formaldehyde, which are both conventionally obtained from petroleum refining. However, phenolic compounds present in bio‐oil obtained via fast pyrolysis of lignocellulosic biomass can be used to partially substitute petroleum‐derived phenol. Thus, the objective of this study was to analyze the techno‐economic feasibility of producing novolac resin by partially substituting petroleum‐derived phenol with biomass‐based phenol in the U.S. The analysis was done at two different annual novolac resin production capacities of 25, 000 and 100, 000 t, respectively, representing the existing small‐ and large‐scale resin production facilities in the U.S. Mass balance and energy analyses of the system were performed to estimate resources (equipment, raw materials, consumables, utilities, and labor) requirements, capital and operating costs, and the financial parameters, including the minimum selling price (MSP). The MSPs for biomass‐based novolac resin for 25, 000 and 100, 000 t capacities were estimated to be $1,585 t–1 and $1,250/t–1, respectively, which falls below its current market price range ($1,700‐3,200 t–1). The bio‐oil to phenol substitution ratio, phenol content in bio‐oil, phenol cost, plant size, biomass feedstock cost, and resin synthesis residence time were the most sensitive parameters affecting the production cost and MSP of novolac resin. The production of biobased novolac resin has the potential to be economically feasible at the current state of technology, and could be an important outlet for diversifying the use of bio‐oil. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Prediction of Viscoelastic Properties of Enzymatically Crosslinkable Tyramine-Modified Hyaluronic Acid Solutions Using a Dynamic Monte Carlo Kinetic Approach.

The present study deals with the mathematical modeling of crosslinking kinetics of polymer–phenol conjugates mediated by the Horseradish Peroxidase (HRP)-hydrogen peroxide (H2O2) initiation system. More specifically, a dynamic Monte Carlo (MC) kinetic model is developed to quantify the effects of crosslinking conditions (i.e., polymer concentration, degree of phenol substitution and HRP and H2O2 concentrations) on the gelation onset time; evolution of molecular weight distribution and number and weight average molecular weights of the crosslinkable polymer chains and gel fraction. It is shown that the MC kinetic model can faithfully describe the crosslinking kinetics of a finite sample of crosslinkable polymer chains with time, providing detailed molecular information for the crosslinkable system before and after the gelation point. The MC model is validated using experimental measurements on the crosslinking of a tyramine modified Hyaluronic Acid (HA-Tyr) polymer solution reported in the literature. Based on the rubber elasticity theory and the MC results, the dynamic evolution of hydrogel viscoelastic and molecular properties (i.e., number average molecular weight between crosslinks, Mc, and hydrogel mesh size, ξ) are calculated.

Autothermal fast pyrolysis of waste biomass for wood adhesives

Biomass fast pyrolysis was performed in a bubbling fluidized bed reactor that incorporated two crucial innovations. A fractional condensation train provided dry bio-oils with only 1% of moisture and much reduced acidity. Autothermal pyrolysis with partial oxidation enhanced dry bio-oil quality while reducing the capital and operating costs by eliminating the need for external heating. Both endothermic pyrolysis with pure N2 and autothermal pyrolysis with oxidant fluidization gases were carried out at 500 °C. Dry bio-oils of birch wood, birch bark or hydrolysis lignin, from both endothermic and autothermal pyrolysis, could substitute up to 65 % of phenol in reacting with formaldehyde to produce wood adhesives that met the international standard specifications on mechanical strength and formaldehyde emissions. Therefore, autothermal pyrolysis did not harm the bio-oil quality for phenol substitution. Dry bio-oil from autothermal pyrolysis of kraft lignin was able to replace 80 % of the phenol.

Bio-oil-based phenol–formaldehyde resin: comparison of weight- and molar-based substitution of phenol with bio-oil

The objectives of this study were (i) to synthesize bio-oil-based phenol–formaldehyde resin to be used for the wood products industry, and (ii) to investigate the effect of phenol substitution (molar-based vs. weight-based) with bio-oil on the properties of resulting PF resin. Bio-oil was produced by hydrothermal liquefaction (HTL) process using sweetgum hardwood, and utilized as a bio-based phenolic feedstock as an alternative for petroleum-based phenol in the synthesis of PF resin. Phenol was substituted with bio-oil (both as weight- and molar-based). The resulting PF resin was noted as BPF-W and BPF-M when bio-oil was used to replace 50% of phenol in weight- and molar-based, respectively, and then compared with neat PF resin in terms of free formaldehyde content, gel time, pH of the resin, solid content, bond strength and thermal stability. Results showed that BPF-M resin had less free formaldehyde content and longer gel time than BPF-W resin. No significant difference in pH and solid content was observed between bio-oil-based PF resins. Moreover, molar-based substitution resulted in a resin with higher bonding strength than that of weight-based substitution, and both BPF-W and BPF-M showed higher bonding strength then neat PF resin. TGA analysis of the resin revealed that substitution of phenol with bio-oil lowered the thermal stability of bio-oil derived PF resins. However, molar-based substitution of phenol with bio-oil could enhance the thermal stability.

Formaldehyde and VOC emissions from plywood panels bonded with bio-oil phenolic resins

Pyrolysis bio-oil was used to partially substitute for phenol in reacting with formaldehyde for the production of bio-oil phenol formaldehyde plywood (BPFP) panels, with the phenol substitution ratio being 20%, 40%, or 60%. Emissions of formaldehyde and volatile organic compounds (VOCs) from the BPFP panels were studied using solid-phase micro-extraction (SPME) followed by headspace gas chromatography/mass spectrometry (GC/MS), and were compared to those from the phenol formaldehyde plywood (PFP) panels. The sources for VOCs were analyzed, and the health risks associated with the BPFP were examined. Results showed that at 80 °C: (1) Formaldehyde emissions from the BPFP panels were increased to about 4 times that of PFP; (2) VOCs emissions were significantly reduced by up to 84.9% mainly due to the greatly reduced phenol emissions, although the total number of VOCs was increased from 20 to 35; (3) BPFP presents greatly increased carcinogenic and non-carcinogenic health risks because of its much stronger emissions of formaldehyde, N,N-dimethylformamide, benzofuran, furfural, and many chemicals from the bio-oil. It is highly advisable that the health risks are properly taken care of before the wide application of BPFP, or similar bio-oil based engineered wood products.

Phenol-formaldehyde resins with suitable bonding strength synthesized from “less-reactive” hardwood lignin fractions

AbstractThe substitution of phenol by lignin in phenol-formaldehyde (PF) resins is one of the most promising end uses of lignin valorization. Lignin from grasses and softwood has been the focus of the studies in this field as they present a higher number of theoretical reactive sites for resin synthesis. Herein we examined the composition and chemical reactivity of “less-reactive” hardwood lignin fractions and their performance in PF resins, synthesized by substituting 50 wt% of the phenol with lignin. Before resin synthesis, the samples were hydroxymethylated and the maximum formaldehyde consumption was recorded. By doing so, we observed that hardwood fractions consumed formaldehyde close to the theoretical calculation, whereas the reference softwood lignin consumed only about ¼ of the theoretical value. In the resin synthesis, we added formaldehyde to the formulation according to the measured maximum formaldehyde consumption. Thus, low values of free formaldehyde in lignin-PF (LPF) resins were achieved (<0.23%). Moreover, the resin bonding strength displayed similar performance irrespective of whether the LPF resins were made with softwood or hardwood lignin (range of 3.4–4.8 N mm−2 at 150°C and 45–480 s of press time). Furthermore, we concluded that hardwood kraft lignins present no disadvantage compared to softwood lignins in PF resin applications, which have significant practical implications.

Suitability of a lignin-derived mono-phenol mimic to replace phenol in phenol-formaldehyde resin for use in wood treatment

Abstract The goal of this study was to assess the suitability of a single mono-aromatic for substitution of petroleum-based phenol for phenol-formaldehyde (PF) resin synthesis and the usage of a new resin for wood treatment. After proper thermal decomposition of wood-based lignin, pyrolysis oil can be obtained. Due to the heterogeneity of the lignin macromolecule, oil contains large variety of organic-based compounds, mainly mono-aromatics, which are proposed to be used for replacement of phenol during PF resin synthesis. Therefore, for this purpose, nine of the most abundant mono-aromatic compounds in bio-oil were selected: ortho-, meta-, para-cresol, guaiacol, catechol, 4-methylcatechol, resorcinol, syringol, 4-ethylphenol and resol-type resin from each mono-aromatic were synthesized. Relevant features of the resin such as pH, viscosity, average molecular weight and curing behavior of resins using differential scanning calorimetry (DSC) were analyzed. Scots pine (Pinus sylvestris L.) sapwood samples were used to evaluate the suitability of resin for wood treatment in terms of dimensional stability and were compared with the PF resin-treated wood. From all tested resins, those made of guaiacol or ortho-, or meta-, or para-cresol and/or 4-ethylphenol proved to be suitable for wood treatment, whereas resins made of catechol or 4-methylguaiacol and syringol did not. Suitability of mono-aromatics for synthesis of resol-type resin depends on chemical structure, where the reactivity of the mono-aromatic (derivative of hydroxybenzene) is defined by the type, location and number of substituents.

Production of Novolac Resin after Partial Substitution of Phenol from Bio-Oil

HighlightsBio-oil was used to produce novolac resin.Bio-oil interacted with phenol and altered the reaction rate and equilibrium.Comparable performance was observed with a low amount of substitution.Abstract. Commercially produced bio-oil with a high content of pyrolytic lignin was substituted for phenol in novolac phenol-formaldehyde (PF) resin production. The reaction progress was tracked, and products were analyzed. Bio-oil substitution resulted in lower conversion rates for both formaldehyde and phenol. Substitution higher than 10 mol% increased the ortho to para ratio and enhanced thermal decomposition of resin by providing an oxidative environment, while 10 and 20 mol% of substitution did not reduce the shear strength of the novolac resin. When mixed with hexamethylenetetramine (HMTA), the bio-oil substituted resins precipitated quickly around char particles, which allowed more resin application on the wood bonding surface. Further investigation found that bio-oil substitution (higher than 10 mol%) might have changed the reaction equilibrium and promoted reverse reactions releasing formaldehyde. Overall, less than 20 mol% phenol substitution by bio-oil with a high content of pyrolytic lignin can be effective in producing novolac resin. Keywords: Bio-oil, Formaldehyde, Lignocellulosic biomass, Novolac, Phenol, Pyrolysis.

Impregnated Paper-Based Decorative Laminates Prepared from Lignin-Substituted Phenolic Resins

High Pressure Laminates (HPL) panels consist of stacks of self-gluing paper sheets soaked with phenol-formaldehyde (PF) resins. An important requirement for such PFs is that they must rapidly penetrate and saturate the paper pores. Partially substituting phenol with bio-based phenolic chemicals like lignin changes the physico-chemical properties of the resin and affects its ability to penetrate the paper. In this study, PF formulations containing different proportions of lignosulfonate and kraft lignin were used to prepare paper-based laminates. The penetration of a Kraft paper sheet was characterized by a recently introduced, new device measuring the conductivity between both sides of the paper sheet after a drop of resin was placed on the surface and allowed to penetrate the sheet. The main target value measured was the time required for a specific resin to completely penetrate the defined paper sample (“penetration time”). This penetration time generally depends on the molecular weight distribution, the flow behavior and the polarity of the resin which in turn are dependent on the manufacturing conditions of the resin. In the present study, the influences of the three process factors: (1) type of lignin material used for substitution, (2) lignin modification by phenolation and (3) degree of phenol substitution on the penetration times of various lignin-phenolic hybrid impregnation resins were studied using a complete twolevel three-factorial experimental design. Thin laminates made with the resins diluted in methanol were mechanically tested in terms of tensile and flexural strains, and their cross-sections were studied by light microscopy.

A Mechanistic Study of Protonated Aniline to Protonated Phenol Substitution Considering Tautomerization by Ion Mobility Mass Spectrometry and Tandem Mass Spectrometry.

We report the use of ion mobility mass spectrometry (IMMS) and energy-resolved collisional activation to investigate gas-phase reactions of protonated aniline and protonated phenol. Protonated aniline prototropic tautomerization and nucleophilic substitution (SN1) to produce phenol with traces of water in the IMMS cell are reported. Tautomerization of protonated phenol and its ability to form protonated aniline in presence of ammonia in the gas phase are also observed. These results are supported by energy landscapes obtained from computational chemistry. These structure modifications in the IMMS cell affected the measured collision cross section (CCS). A thorough understanding of the gas-phase reactions occurring in IMMS appears mandatory before using the experimental CCS as a robust descriptor which is stated by the recent literature.

Long-term impact of environmental regulations and eco-conscious customers in the chemical industry: A system dynamics approach to analyze the effect of multiple disruptions

The chemical industry is characterized by a complex production network in which all chemicals are more or less tightly connected to each other. The future development of selected parts of this network heavily depends on external influences such as environmental regulations and changes in consumer requirements. Two examples for such influences are a bisphenol A ban and the substitution of phenol by lignin. In this paper, the ability of system dynamics to model multiple disruptions in complex chemical production networks is demonstrated and a routine to calculate the effect of nonlinearity arising from their interplay is presented. It makes use of a case study taking the position of a company buying acetone. Combinations of the bisphenol A ban and the phenol substitution by lignin were tested in simulation runs up to 2030. The results are analyzed with respect to the long-term behavior of the acetone price and managerial implications are deduced. The approach presented in this paper is a suitable tool to deal with the highly uncertain and dynamic developments within the chemical industry to support long-term strategic planning.

Phenolic foams: A review of mechanical properties, fire resistance and new trends in phenol substitution

Phenolic foams (PF) have a combination of properties that make them attractive for a number of engineering applications such as insulation, lightening, energy absorption and fire protection. Phenolic foams exhibit excellent fire-retardant behaviour but have insufficient mechanical properties (e.g. fatigue, flexural properties and friability) for different applications in comparison to other foam materials. Hence, numerous studies have tried to improve these mechanical properties without deteriorating its excellent fire-retardant behaviour. Different approaches have been investigated, such as the addition of fibres and particles or the chemical modification of the PF base resin. This work will first briefly present generalities from resin synthesis to foam production. The main part will review the existing papers dealing with the improvement of the compressive and flexural strength as well as the friability. Moreover, evolution of the cell size with these mechanical properties will be presented, although there is no well-defined link between them. Then, the influence of these modifications on the fire-retardant behaviour of PF will be discussed. Finally, the last part will present work to substitute phenol from petroleum sources to environmental friendly sources.

Lignin Phenol Formaldehyde Resoles Using Base-Catalysed Depolymerized Kraft Lignin.

Lignin phenol formaldehyde (LPF) resols were produced using depolymerized lignin fractions at various levels of phenol substitution (50 to 70 wt %). To produce monomeric-rich (BCD-oil) and oligomeric (BCD-oligomers) bio-based phenolic compounds, softwood kraft lignin was base-catalysed degraded. These base-catalysed depolymerized (BCD) building blocks were further used to substitute phenol in the synthesis of phenolic resins and were characterized in detail (such as viscosity, free formaldehyde and phenol content, chemical composition, curing and bonding behaviour). The adhesive properties were compared to a phenol formaldehyde (PF) reference resin and a LPF with untreated kraft lignin. The resins synthesized with the two depolymerized lignin types differ significantly from each other with increasing phenol substitution. While with LPF-BCD-oligomers the viscosity increases and the bonding strength is not effected by increasing lignin content in the resin, a reduction of these properties could be observed with LPF-BCD-oil. Furthermore, LPF-BCD-oil showed similar curing behaviour and ultimate strength as the reference LPF. Adhesive bonds made using LPF-BCD-oligomers exhibited similar strength to those made using PF. Compared to the reference resins, it has been demonstrated that modified renewable lignin based phenolic components can be an equally performing alternative to phenol even for high degrees of substitution of 70%.

The influence of two‐stage variable temperature suspension polymerization on polyvinyl chloride resin: The molecular chain segment structure and thermal stability

The suspension polymerization of polyvinyl chloride (PVC) was carried out at two different constant temperature conditions (52.5°C and 57.5°C) and at two‐stage variable temperature conditions (52.5–57.5°C). The molecular weight and molecular weight distribution were characterized by gel permeation chromatography (GPC). The unstable chlorine content, total double bond content, and conjugated diene content were explored via phenol substitution, catalytic bromine addition, and ultraviolet–visible spectroscopy (UV–Vis). pH meter and thermogravimetric analyzer (TGA) were used for the determination of the thermal stability. According to the results, due to the gradual consumption of the impurities and the effect of the local high temperature in the early stage of polymerization, which caused more molecular chain‐transfer and more structural defects, a large number of oligomers generated. A rapid increase in the molecular weight could be found until the conversion was close to 23%. A lower temperature should be conducive to reducing the structural defects in molecular segments. Based on these observations, we applied two‐stage variable temperature polymerization and compared the PVC resin at a similar molecular weight at a constant temperature of 56°C. The PVC resin produced by the two‐stage variable temperature polymerization process obtained a similar Polydispersity index (PDI), reduced the unstable chlorine content by 15.11%, reduced the total double bond structure content by 8.81%, reduced the conjugated diene structure content by 13.86%, and increased the thermal stability time by 13.91%, thereby improving the thermal stability of the PVC resin. J. VINYL ADDIT. TECHNOL., 25:E80–E87, 2019. © 2018 Society of Plastics Engineers

Oxidative Depolymerizaton of Kraft Lignin and its Application in the Synthesis of Lignin-phenol- formaldehyde Resin

Kraft lignin (KL) was valorized by introducing phenolic hydroxyl groups and adjusting the molecular weight by oxidative depolymerization. Hydrogen peroxide with copper sulfate as a catalyst was employed in this process. The depolymerized lignin (DL) was characterized with differential ultraviolet spectrum (UV), Fourier transform infrared (FT-IR) spectrometry, gel permeation chromatography (GPC), and heteronuclear single quantum correlation (HSQC) spectra. Both the molecular weight (Mw and Mn) and the polydispersity of the depolymerized lignin decreased compared with default kraft lignin. The content of phenolic hydroxyl groups increased from 1.55 to 2.66 mmol/g. The depolymerized lignin was used in the synthesis of lignin-phenol-formaldehyde (LPF) resin as a substitution of phenol. The physical properties including viscosity, bonding strength, and free formaldehyde content of the adhesive met the GB/T 14704-2006 standard with the substitution of 50% phenol with DL.

Impact of Molecular Weight of Kraft Lignin on Adhesive Performance of Lignin-Based Phenol-Formaldehyde Resins*

Abstract This study describes the influence of improved lignin homogeneity on the adhesive properties of lignin-based phenolic resins. Softwood kraft lignin was separated by applying an ethanol-based solvent fractionation to obtain three lignin fractions with a narrow molar mass distribution (smallest [Mw 1,590 g/mol] to largest [9,570 g/mol]). Lignin-phenol-formaldehyde (LPF) adhesives were prepared by 50 percent (by weight) substitution of phenol with an adjusted formaldehyde-to-phenol molar ratio. For investigating the storage stability of the resin, viscosity was monitored, curing behavior was determined by differential scanning calorimetry (DSC), and development of the bonding strength was analyzed via tensile shear strength as a function of press time. An acceleration of the condensation process for LPFs with higher molecular mass was observed. DSC signal indicated that LPFs need a slightly higher temperature for a complete curing than the phenol-formaldehyde reference resin. Furthermore, it was found that the tensile shear strength decreases with the use of fractionated kraft lignin in phenolic adhesives. No significant difference in reactivity was found for the resins making up the different lignin fractions.