Abstract:Polyurethane materials are considered ideal self-healing materials due to their inherent hydrogen bonding structure. Researchers have found that introducing supramolecular chemistry into polyurethane can result in even better self-healing materials with superior performance. These supramolecular-based self-healing polyurethane materials can recover most of their physical and chemical properties after being damaged, demonstrating excellent performance. This article reviews recent advances in supramolecular-based self-healing polyurethane materials from different healing mechanisms, including widely used hydrogen bonding systems, aromatic π-π stacking systems, ion-crosslinked polymer systems with ionic side chains that form interlocking points, metal-ligand interaction systems that crosslink materials through coordination of metal ions and ligands, and host-guest interaction systems where macrocyclic molecules interact with specific sized molecules. Finally, the future development advantages of self-healing polyurethane are discussed.

Abstract:The design and fabrication of bio-inspired bionic functional surfaces has become an important and fascinating research topic with a wide range of applications in daily life, industry and agriculture in recent years. Benefitting from its high flexibility, low surface energy and chemical stability, polydimethylsiloxane (PDMS) is widely used as a functional modification of bionic surfaces. This article reviews the preparation methods of PDMS-based biomimetic surfaces and their research progress in protective fields such as anti-corrosion, anti-icing, anti-biofouling and optical. Furthermore, the existing issues and development trends are summarized and prospected.

Abstract:Among various heavy oil recovery technologies, physical viscosity reduction has the advantages of simple process and good adaptability, but it has the disadvantages of high production cost and shortage of thin crude oil resources. Chemical viscosity reduction has the advantages of fast effect and low energy consumption, but it has the disadvantages of complex treatment process. Oil-soluble viscosity reducer technology combines the advantages of physical viscosity reduction and chemical viscosity reduction. It has many advantages such as less addition, good effect, low cost and simple post-treatment. In recent years, it has attracted the attention of experts in the industry. This paper introduces the reasons for the high viscosity of heavy crude oil, analyzes the viscosity reduction mechanism of oil-soluble viscosity reducer, summarizes the synthesis process of various oil-soluble viscosity reducers, and reviews the advantages and disadvantages of different types of viscosity reducer. Compared with binary and ternary oil-soluble viscosity reducers, a variety of polar groups of quaternary oil-soluble viscosity reducer can act better on macromolecules in heavy crude oil and destroy the layered structure of resin and asphaltene, so that the viscosity of heavy oil can be significantly reduced. The composite and compound use of viscosity reducer can enhance the viscosity reduction effect. The development trend of oil-soluble viscosity reducer is prospected. It is believed that it is necessary to further study the viscosity reduction mechanism at the molecular level and optimize the synthesis process of viscosity reducer from the perspective of green environmental protection. The solution of the above problems will contribute to the design, preparation and wide application of high-efficiency oil-soluble viscosity reducer molecules.

Abstract:Microbial desalination cells (MDCs) are an emerging green and sustainable energy recycling technology, which utilize microbial extracellular respiration to simultaneously drive salinity removal, electricity generation and degradation organic pollutants. Firstly, the energy consumption and limitations of conventional energy-intensive desalination techniques (thermal and membrane processes) are summarized. Secondly, the MDCs was systematically analyzed from the aspects of work mechanism, configuration evolution, operative parameters and microbial community of the classic MDC system. The collaborative efficient treatment of wastewater by multiple MDC coupled technologies and its challenges for sustainable development are described in detail. Finally, the future strategies are prospected from the perspective of MDCs in efficient, sustainable and low-carbon wastewater treatment, saltwater desalination and energy/resource recovery.

Abstract:Curdlan is a kind of a microbial extracellular exopolysaccharide, which has been widely used in the field of meat processing and preservation due to its good thickening, water retention, gelation and film formation properties. This paper reviews the functional properties of curdlan, focusing on the effect of curdlan on the quality characteristics of meat and meat products and the mechanism of improving the quality of meat products, finally, summarizes the fresh-keeping effect of different types of edible composite films prepared from curdlan in meat foods, in order to provide a theoretical reference for the wide application of curdlan in the processing and preservation of meat foods.

Abstract:Hydrogen energy is an important direction to promote the low-carbon transformation of fossil energy under " double carbon ".Dark fermentation of microorganisms is an effective way to achieve green hydrogen conversion of biomass. Among them, the use of metal nanoparticles ( MNPs ) with quantum size effect, large specific surface area and high conductivity to optimize dark fermentation hydrogen production technology is a research hotspot in recent years. The mechanism, technical difficulties and hydrogen production effects of adding MNPs to optimize the performance of hydrogen production by dark fermentation at home and abroad are reviewed and commented. The effects of three popular MNPs optimization strategies of iron, nickel and zinc on improving the activity of hydrogenase system, enhancing the metabolic hydrogen production pathway and optimizing the microbial community structure are emphatically expounded and compared. The research directions and application prospects of dark fermentation hydrogen production are prospected, such as optimizing the activity of hydrogenase by MNPs, broadening the substrate of biomass fermentation, screening and reactor design of hydrogen-producing bacteria, and developing biomass fermentation technology.

Abstract:Layered double hydroxides (LDHs) are anionic clay with a special layered structure, which are of great interest for wastewater treatment because of their adjustable chemical composition, large specific surface area and unique structural memory effect. Tuning the structure of LDHs is an effective way to further expand its application and improve its adsorption performance. The special layered structure of LDHs and their own properties are firstly introduced. Secondly, the five most commonly used preparation methods of LDHs, namely co-precipitation, ion exchange, urea hydrolysis, calcination recovery and sol-gel method, are mainly summarized, and the principles and characteristics of each preparation method are introduced respectively. Then the influence of structural tuning of LDHs on their adsorption performance for heavy metal ions are reviewed, and the adsorption mechanism of LDHs on heavy metal ions is summarized. Finally, the challenges faced by the current research on LDHs in the treatment of wastewater containing heavy metal ions are pointed out, and the future research directions and development trends of the materials are prospected.

Abstract:Hydroxyapatite (HA) has excellent biological activity and biocompatibility, which widely used in bone repair, regeneration as well as replacement in bone tissue engineering. However, the intrinsic dispersibility, low mechanical properties, poor integration with polymer materials limit its application. In order to overcome their shortcomings, many researchers have explored the modify/composite methods of HA to improve the dispersion, hydrophilicity, antibacterial and mechanical strength for the clinical applications. This review introduces commonly modification methods of HA nanoparticles, such as ions doping, surface modification and material composite. Finally, we also discuss the current research hotspots so that provide more enlightenment and instructive effect on fundamental research of HA composite materials.

Abstract:As a natural material, leather is easy to breed colonies or mold during storage, which impacts human health. Recently, antibacterial nanomaterials have been widely used in leather processing because of their excellent heat resistance, high stability, large specific surface area, and high reactivity. Based on this, the types, characteristics, and preparation methods of antibacterial nanomaterials were summarized in this paper. Then, the antibacterial mechanism of antibacterial nanomaterials was described, and the application of antibacterial nanomaterials as fatliquoring agents, tanning agents, and finishing materials in the leather industry was discussed in detail. Finally, the problems existing in the current stage of antibacterial nanomaterials in the process of leather processing and the future research direction were analyzed and prospected, to providing theoretical and practical guidance for promoting the promotion and application of new materials in the leather industry.

Abstract:In this paper, SiO2 composite particles prepared by Stober method combining colloidal SiO2 particles and powder SiO2 particles are used to construct rough surface on glass substrate, acidic organosilicon oligomer prepared by prepolymerization of triethoxymethylsilane (MTES) and ethyl orthosilicate (TEOS) is used as bonding agent, modified by using coupling agent KH540 and fluorosilane PFDT, and SiO2 composite particles/acidic organosilicon oligomer composite superhydrophobic coating is prepared on glass substrate by spraying method. The SiO2 composite particle/acidic silicone oligomer composite superhydrophobic coating was prepared on glass substrate by spraying method, and then the effects of SiO2 composite particle, acidic silicone oligomer, coupling agent KH540 and fluorosilane PFDT on the composite coating were investigated. The study shows that when the SiO2 composite particles consist of two kinds of particles, namely, colloidal SiO2 particles with a particle size of 110 nm and powder SiO2 particles with a particle size of 50 nm, and the mass ratio of SiO2 composite particles solution to acidic silicone diluent is 4:1, and the mass ratio of coupling agent KH540 to fluorosilane PFDT is 1% of the mixture, the composite coating can achieve a light transmission rate of 88% in the visible light wavelength range. The composite coating can reach 88% light transmittance in the visible wavelength range, 155° static contact angle, and maintain superhydrophobicity after 60 cm abrasion on 800-grit sandpaper, with good self-cleaning property, providing a simple and low-cost solution for the preparation of transparent superhydrophobic coatings.

Abstract:Therefore, NCO-terminated two-component microporous polyurethane elastomers with low viscosity (LVMPU) prepolymer was synthesized by prepolymer method using isophorone diisocyanate (IPDI) and polytetramethylene ether glycol (PTMEG) as raw materials. Secondly, 1,4-butanediol (BDO) and trimethylolpropane (TMP) were used as chain extenders, and a small amount of water in the air was used as foaming agent, two-component LVMPU has excellent mechanical properties, yellowing resistance, and light resistance was obtained by reaction curing at high temperature(130℃) after static defoaming at room temperature in the mold. The effects of different mass ratio of IPDI and PTMEG, TMP and BDO and residual NCO content on the properties of two-component LVMPU was investigated. The results show that when the mass ratio of IPDI and PTMEG is less than 250:300 and the residual NCO content is less than 2.4%, two-component LVMPU elastomer without NCO groups can be obtained; When the mass ratio of IPDI and PTMEG is 200:300, the mass ratio of TMP and BDO is 0:1, and the residual NCO content is 1.4%, the mechanical properties of the two-component LVMPU elastomer are the best; With the increase of the residual NCO content, the surface of the two-component LVMPU has no cell structure, and the cross-sectional cells increase gradually, and most of them are circular closed-cell structures with large pore sizes; When the mass ratio of TMP and BDO increases gradually, most of open-cell structures appear on the surface of the two-component LVMPU, the circular open-cell structures of the section increase gradually, the pore size distribution is relatively uniform, and the average pore size decreases.

Abstract:A eutectic hydrate salt (EHS) with low supercooling degree and no phase separation was prepared using decahydrate sodium carbonate (SCD) and dodecahydrate sodium hydrogen phosphate (DHPD) as the main phase-change materials. Adding nonahydrate sodium silicate as a nucleating agent. A shape-stabled phase-change material (SSPCM) of the fixed EHS/SiO₂ was prepared by adsorbing EHS on gas-phase SiO₂ with impregnation method. The transition temperature of SSPCM was 24.08 ℃, the enthalpy value was 146.6 J/g, the supercooling degree was 0.55 ℃ and the thermal conductivity was 0.5454 W/m?K. Compared with insulation foam, the SSPCM extended the warming time of the central temperature in the building by 3.26 times and the cooling time by 1.39 times, showing excellent"thermal buffering", which have broad application prospects in building energy efficiency.

Abstract:A new aromatic diamine monomer with phenolphthalein and methyl groups was prepared by o-cresolphthalein and 2-chloro-5-nitrotrifluorotoluene through aromatic nucleophilic substitution and oxidation-reduction reaction. Then a series of copolymerized polyimides which contains phenolphthalein structure and bulky groups were prepared by diamine monomer (2d) and commercial 2,6-diaminotoluene (TDA) with ODPA in different proportions through using a variety of monomer copolymerization methods, the structure and performance of copolymerized polyimides were tested. The series copolymerized polyimides had excellent solubility, they were not only dissolved in high boiling point solvents, such as NMP、DMAc、DMF and DMSO, but also could dissolve in low boiling point solvents, such as CHCl₃, CH₂Cl₂ and THF at room temperature. Their glass transition temperatures were between 275~314 ℃, and their temperatures of 10% weight loss were in the range of 477~507 ℃ and 477~490 ℃, respectively. Meanwhile, these polyimides had low dielectric constants and good thermal properties. The dielectric constants of the polymer films ranged from 2.69 to 2.92 at 1MHz. The tensile strength, elastic modulus and elongation at break of copolyimides ranged from 80 MPa to 92 MPa, 1.7 GPa to 2.0 GPa, and 9.2% to 13.0%, respectively.

Abstract:Glycogen derivative with strong positive was synthesized by two steps. Firstly, the glycogen was modified by ethylenediamine to obtain the aminated glycogen derivative (N-Gly). Secondly, N-Gly was modified by 2, 3-epoxypropyl trimethyl ammonium chloride (GTA) to obtain the cationic quaternary ammonium glycogen derivative (QA-N-Gly). Then, quaternary ammonium glycogen derivative-gelatin composite hydrogel (QA-N-Gly/Gel) was prepared by amide central crosslinking. The chemical structure of glycogen derivative was characterized by FTIR and 1H-NMR. The particle size distribution, Zeta potential and morphology of glycogen derivative were also investigated. The results showed that glycogen was successfully aminated and quaternary ammonium modified. The QA-N-Gly were dispersed nanoparticles with a size distribution of 100-200 nm and a Zeta potential of 90-100 mV. QA-N-Gly exhibited antibacterial effect because of significant positive charge. The physicochemical and biological properties of QA-N-Gly/Gel hydrogel were evaluated. The results showed that the addition of glycogen derivatives could improve the mechanical strength and stability of gelatin-based hydrogel. The fracture stress of QA-N-Gly/Gel was 66.8 KPa, and the compression modulus was 13.3 KPa. QA-N-Gly/Gel showed obvious antibacterial effect on Staphylococcus aureus and Escherichia coli, and the inhibition rate reached 97% and 50%, respectively. In addition, QA-N-Gly/Gel showed no hemolysis and low cytotoxicity, the 48 h survival rate of NIH-3T3 cells was more than 80%.

Abstract:Two iridium phosphorescent complexes IV and IV.-d₂₀ were synthesized by modifying the 2-methyl-8-(2-pyridyl)benzofuran[2,3-B]pyridine auxiliary ligand, introducing electron-absorbing group phenyl at the 4th position of pyridine, and fully deuterated the two methyl groups of the 5-methyl-2-p-tolylpyridine main ligand, and characterizing and confirming their structures by elemental analysis, mass spectrometry and nuclear magnetic resonance hydrogen spectroscopy. The photophysical properties and energy level structure were studied by UV-Vis spectroscopy, fluorescence emission spectroscopy (PL) and cyclic voltammetry. The results showed that the emission wavelengths of IV and IV-d₂₀ photoluminescence spectra of iridium complexes were 546.85nm and 548nm, respectively, and their HOMO and LUMO energy levels were -5.237ev and -2.645ev, -5.082ev and -2.50ev, respectively, which were potential yellow-green phosphorescent materials. OLED devices with the structure of ITO/HT:NDP-9(100nm, 2%)/HT(130nm)/EB(10nm)/GH:compound IV or IV-d₂₀(40nm, 5%)/HB(10nm)/ET:Liq (35nm, 50%)/Liq(10nm)/Al (150nm) were prepared with iridium complexes IV and IV-d₂₀/HB(10nm)/ET:Liq (35nm, 50%)/Liq(10nm)/Al(150nm), and their device performance was studied. The results showed that iridium complex IV-d₂₀ showed better device performance. At a current density of 20mA/cm₂^{, the device of iridium complex IV-d}₂₀ emits at a wavelength of 552nm, a CIE coordinate of (0.422, 0.569), a current efficiency of 87.00cd/A, and an external quantum efficiency (EQE) of 23.82%.

Abstract:In order to improve the compatibility of graphene with bismaleimide (BMI) resin matrix and to enable the rapid formation of high-quality self-lubricating transfer films during friction. This paper prepared HBPSi/Ni/GNRs com-posite particles by comodifying graphene nanoribbons (GNRs) with hyperbranched polysiloxane (HBPSi) and Ni nanoparticles, and introduced them into BMI resin to prepare HBPSi/Ni/GNRs/BMI composites, and introduced them into BMI resin to prepare HBPSi/Ni/GNRs/BMI composites. FT-IR, SEM, TEM, tribological wear testing ma-chine and molecular dynamics simulation were used to investigate the effects of the structure, morphology and in-troduction of the composite particles and the tribological properties of the composites, and the tribological wear mechanism was investigated. The results showed that HBPSi and Ni nanoparticles were successfully loaded onto the surface of GNRs. HBPSi/Ni/GNRs were able to significantly improve the tribological properties of their BMI composites compared to GNRs. When the filler addition is 0.6 wt%, the friction coefficients and volume wear rate of the HBPSi/Ni/GNRs composites reach their lowest values of 0.18 and 4.5×10-6 mm3/(N.m), respectively. In ad-dition, the molecular dynamics results indicate that the strong interfacial interaction between HBPSi/Ni/GNRs and BMI is the key leading to the enhanced shear resistance of their composites.

Abstract:Vinyl terminated polysiloxane (FSI) was prepared by ring opening polymerization of 1,3,5-trimethyl-1,3,5 (trifluoropropyl) cyclotrisiloxane(D3F), octamethylcyclotetrasiloxane(D4), and tetramethyltetravinylcyclotetrasiloxane(D4Vi). Then, the perfluorohexanyl(TE-6) was grafted into the structure of FSI to construct fluorinated polysiloxane(FSI-F) through free radical polymerization. The structure and relative molecular weight of FSI-F were characterized by NMR, GPC, and FTIR. Using FSI-F as a hydrophobic material, plastic grade polypropylene (PP) as a base material, and n-hexadecyltrimethoxysilane(Dynasylan 9116) as a compatibility modifier, respectively. The effects of FSI-F mass fraction, the mole ratio between TE-6 and D4Vi, and the amount of Dynasylan 9116 addition on the hydrophobic and mechanical properties of FSI-F/PP composites were discussed using orthogonal experimental methods. The intrinsic relationship between the morphology, thermal properties of FSI-F/PP composites and their comprehensive performances was revealed by means of SEM, AFM, and TG-DSC. Finally, a type of hydrophobic materials with hydrophobic angle, hydrophobic angle, tensile strength, and elongation at break of 130.4, 52.8, 37.56 MPa, and 1125.67% was prepared, while the n(D4Vi)：n(TE-6) = 1:2, 6 % mass fraction of FSI-F, and 2 % mass fraction of Dynasylan 9116. This study would shed light on the development of the hydro-oleophobic materials for applications in fields such as self-cleaning and pipeline drag reduction.

Abstract:Pd/ZrO2 and alkali metal doped Pd/M/ZrO2 catalysts were prepared by incipient-wetness impregnation with ZrO2 from Zr(OH)4 calcination as the support. These catalysts were applied to the selective hydrogenation of 1,4-butynediol (BYD) to 1,4-butenediol (BED). The structures and properties of the catalysts were characterized by BET, XRD, CO2-TPD, XPS, and TEM. The effects of reaction atmosphere and alkali metal dopant on the activity, selectivity and stability of the catalysts in hydrogenation of BYD to BED were investigated. 1.0% Pd/ZrO2 exhibited high catalytic activity (0.048 molBYD/(gPd·s)) and reasonable selectivity of BED (xBYD≈100%，SBED=91.2%) under the conditions of 50 ℃, 2.40 MPa H2 pressure. The presence of ammonia into the reaction mixture inhibits the hydrogenation activity but improves the selectivity of BED. 95.6% selectivity of BED was achieved with complete conversion of BYD. The doping of alkali metals (Li, Na, K, Rb, Cs) onto ZrO2 support improves the selectivity of BED, and Rb is the most effective dopant with BED selectivity up to 94.1%.

Abstract:Based on the double activation model of the epoxide, zinc phthalocyanine-based porous organic polymer (denoted as ZnPc-POP) was prepared by Schiff-base condensation reaction with zinc tetraminophthalocyanine and 1,3,5-benzenetricarboxaldehyde under solvothermal conditions. The structure was characterized by FTIR, 13CMAR NMR, XPS, TEM and nitrogen adsorption desorption. Using the cycloaddition reaction of epichlorohydrin (ECH) and CO2 as the model and tetrabutylammonium bromide (TBAB) as the cocatalyst, the catalytic performance, recycling ability and substrate applicability of ZnPc-POP were investigated, and the catalytic mechanism was also explored. The results show that ZnPc-POP has abundant mesoporous structure (pore volume is about 0.64 cm3/g, average pore size is about 20 nm) and high specific surface area (171.6 m2/g). At 100 ℃ and 1.0 MPa, the selectivity of ECH to produce cyclic carbonate was more than 99%, the yield was 96%, and the conversion frequency (TOF) was up to 533.3 h-1. ZnPc-POP can be recycled at least 5 times without significant decrease in the catalytic activity. The oxygen atom in the epoxide is activated effectively by coordination with the the Lewis acidic zinc center of ZnPc-POP, and the bromine ion in the co-catalyst TBAB promotes the ring-opening of the epoxide through nucleophilic attack. This double activation of epoxide ring-opening is the rate-controlling step of the CO2 cycloaddition reaction.

Abstract:Improving visible light utilisation and suppressing the rapid complexation of photogenerated carriers is a major challenge for the efficient activation of graphite-phase carbon nitride (g-C3N4) for the degradation of pollutants by peroxynitrite (PMS). The interfacial interaction between P-doped g-C3N4 nanosheets (PCN) and cobalt phthalocyanine (CoPc) was enhanced to achieve efficient activation of PMS for tetracycline (TC) degradation. PCN was prepared from urea and sodium hypophosphite by high temperature phosphating process, and then calcined with CoPc in muffer furnace to construct heterojunction. The results showed that the construction of the heterojunction not only extended the light absorption edge to the visible light region, but also made the degradation rate of TC(10 mg/L) reached 98.8% after 40 minutes in 50 mL solution activated by 20 mg of optimal catalyst and 30 mg of PMS, and the degradation rate was 0.087 min-1. This is due to the heterojunction potential at the interface between PCN and CoPc accelerating the separation of photogenerated carriers. At the same time strong interfacial interactions provide channels for electron transfer, allowing the reduction of O2 to generate large amounts of ?O2? radicals and activation of PMS to generate ?SO4? and ?OH radicals to degrade TC.

Abstract:Lycopene is a fat-soluble bioactive substance, which is easy to degraded and isomerized during food processing. Natural surfactants were screened, the high cis-lycopene nano emulsion was prepared by high speed shear method using the prepared high cis-lycopene as the embedding object. The preparation process of high cis-lycopene nano emulsion was optimized by single factor and response surface experiments, and the reasonable storage method of high cis-lycopene nano emulsion was explored by stability experiments. The results showed that under the conditions of 1:3 oil-water ratio, 6% sodium caseinate solution concentration, 12 000 r/min shear speed and 15 min shear time, the highest embedding rate of high cy-lycopene nano emulsion was (88.09±0.92) %. The stability experiments showed that high cis-lycopene nano emulsion were stored in low temperature, dark, nitrogen-filled, neutral or weakly alkaline environment. metal ion Al3+, salt ion NaCl, antioxidants (tetra-butylhydroquinone and dibutyl hydroxy toluene) and sucrose were added. The oxidative degradation and retro-isomerization of lycopene isomers could be reduced and inhibited. This scheme can effectively improve the stability and solubility of high cis lycopene nano emulsion, and improve the bioavailability of lycopene.

Abstract:Using waxy corn starch as raw material and stannous isooctanoate as catalyst, polylactic acid modified waxy corn starch was prepared in the melting system of lactide. A 1H-NMR method for determining the degree of substitution of polylactic acid modified waxy corn starch was established. With the degree of substitution as the response value, reaction time, reaction temperature and the amount of lactide as the investigation factors, the synthesis process of polylactic acid modified waxy corn starch was optimized through single factor and response surface experiments. The optimum process was obtained as follows: reaction time 12.46h, reaction temperature 111.75 ℃, lactide content 258% of starch. The predicted maximum degree of substitution is 0.0253, and the actual degree of substitution is 0.0238. Through a series of characterization of polylactic acid modified starch prepared under the optimal conditions, it is proved that the particle structure of polylactic acid modified waxy corn starch has not been completely destroyed, and its crystal form and molecular weight are better than those of traditional solvent technology. It will have a broad application prospect in the fields of degradable materials and drug carriers.

Abstract:A series of catalysts with different contents of K, Na and Cs for vapor phase condensation of ester aldehydes were prepared by impregnation method using γ-Al2O3 and SiO2 as carriers. The structure, acid and basic sites of the catalysts were characterized by XRD, BET, NH3-TPD and CO2-TPD. The condensation performance of catalysts for methyl propionate and formaldehyde in vapor phase was investigated. The results showed that the activity of 10% Cs/SiO2 catalyst was better under the same reaction conditions (pressure 0.2 MPa, temperature 370 ℃, weight hourly space velocity 1.2 h-1), the conversion of methyl propionate was the highest (41.03%) and the selectivity was 99.20%. Under the premise of abundant alkali center, there was a positive correlation between the proportion of weakly basic sites on the surface of the catalyst and its catalytic performance for condensation of ester aldehydes in vapor phase. The presence of acidic and moderately strong alkaline sites of the catalyst could lead to a decrease in activity and selectivity of the catalyst.