Total Acid Sites Research Articles

Effects of nickel-deactivations on zeolites-Y of different SiO2/Al2O3 ratios in catalytic cracking of hydrocarbons

Effects of nickel deactivation on catalytic activities of three types of zeolites-Y (Y-5.1, USY-5.2, and VUSY-12) with varying SiO2/Al2O3 ratios were studied in cracking of hydrocarbons. Physicochemical characteristics such as crystalline phases, Ni oxidation states, morphology, acidity, surface area, and thermal stability of the samples were analysed. XRD revealed the absence of observable nickel compounds below 5 wt%, with NiO phase emerging at higher concentrations. Surface areas decreased from 826 to 615 m2/g (Y-5.1), 786–686 m2/g (USY-5.2), and 762–571 m2/g (VUSY-12) at 30 wt% Ni. The total acid sites also reduced from 17.247 to 9.826 µmol/g (Y-5.1), 15.464–8.854 µmol/g (USY-5.2), and 7.094–4.876 µmol/g (VUSY-12). XPS confirmed Ni2+ states. Catalytic cracking tests using n-Heptane demonstrated increases in C5-C6 alkanes, olefins, hydrogen, and methane yields as nickel concentration increased, with respective values of 64 %, 28 %, 79 % and 68 % for Y-5.1; 62 %, 28 %, 76 %, and 62 % for USY-5.2; and 58 %, 21 %, 75 %, and 60 % for VUSY-12. A corresponding decrease in heavier components were observed. The study demonstrates that nickel modification significantly impacts the physicochemical properties and catalytic performance of zeolite-Y and these depend strongly on the SiO2/Al2O3 ratios. The study gives further insights into the structural and catalytic modifications induced by nickel doping in zeolites, highlighting the potential of nickel-modified zeolites in promoting undesirable hydrogen and gas.

Layered silicate PLS-3 with PREFER structure supported Pd nanoparticles: A recyclable catalyst for the synthesis of furfuryl ethyl ether

Supported Pd catalysts has found wide applications in reductive etherification of aldehydes. However, the synthesis of furfural-derived ethers on Pd catalysts has encountered great challenges because several side reactions such as over-hydrogenation of furan ring and decarbonylation always occur simultaneously under the reaction conditions. We herein reported the catalytic performance of Pd nanoparticles (∼4 nm) supported on the external surface of layered structured PLS-3 zeolite with narrow pore size (<0.4 nm) and large external surface area (80–100 m2/g). The PLS-3 with Si/Al of 92 having total acid sites of 93 μmol/g showed satisfied ether selectivity. Pd nanoparticles located on the external surface showed better etherification selectivity than those confined in the framework, due to the less diffusion limitation of furfural acetal as an intermediate.

Effects of adding metals to Beta zeolite on ethanol conversion to hydrocarbons

This study investigated the effects of Beta zeolite ion exchange with Fe, Zn, and Co on ethanol conversion to hydrocarbons. Various characterization techniques such as X-ray fluorescence (XRF), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray diffraction (XRD), magic angle rotation nuclear magnetic resonance spectrometry (MAS NMR) of 29Si and 27Al, scanning electron microscopy (SEM), nitrogen physisorption, ammonia temperature-programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR) were employed. Catalytic tests were performed at temperatures from 475 to 550 °C under ambient pressure. The metal addition to Beta zeolite reduced micropore area and volume, decreased the concentration of the extra-framework aluminum, and increased total acid site density and Lewis acid sites, except for Fe. For all catalysts, ethylene was identified as the primary product. However, catalysts containing Zn and Co displayed the formation of propylene and C1 to C3 paraffins. The catalyst with Fe exhibited the highest deactivation and a significant decrease in acidity, attributed to the formation of extra-framework aluminum, resulting in exclusive ethylene production.

Catalytic upgrading of Naomaohu coal pyrolysis volatiles over NiAl and NiLiAl oxides

Catalytic upgrading of volatiles is an essential technology to improve the product distribution of pyrolysis for the clean and efficient utilization of low-rank coals. In this work, novel acid-base bifunctional catalysts composed of Ni/Li/Al oxides were designed and prepared using LDH precursors with tunable chemical composition and structural properties. The catalysts were systematically characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), physisorption, NH3-temperature programmed desorption (NH3-TPD), CO2-temperature programmed desorption (CO2-TPD), H2-temperature programmed reduction (H2-TPR), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). A two-stage fixed bed reactor was employed to evaluate the performance of the catalysts. Characterization results suggest that the crystal size of NiO and the surface area of the catalyst decreased with increasing Li content and decreasing Ni content in the catalyst, while the pore volume and pore diameter were positively correlated with Li content. Moreover, the addition of Li reduced the amount of weak acid sites and raised the amount of total basic sites. Consequently, the bifunctional catalysts boosted the yield of light tar and the contents of aromatics and phenols in tar. Specifically, with the highest total acid sites (569 μmol/g) promoting the cracking of heavy pitch components, Ni2.5Li0.5Al1 decreased the content of pitch in tar to 23.8 wt%, representing a 42.7 % drop from the corresponding non-catalytic pyrolysis. Accordingly, it improved the light tar yield to 7.2 wt%, which was 18 % higher than non-catalytic pyrolysis. 450 °C is identified as a suitable temperature for the catalytic upgrading of volatiles from Naomaohu coal; higher catalysis temperatures at 500 °C and 550 °C led to lower tar yield and lower phenols content, along with higher gas yield and more carbon deposition.

Catalytic pyrolysis of rape straw to produce light aromatic hydrocarbons over HZSM-5 loaded by metal ions from spent lithium batteries extracted with citric acid

In this study, metal-loaded HZSM-5 was prepared with metal ion extracted from the cathode materials of spent lithium batteries (lithium iron phosphate, LFP; lithium nickel-cobalt manganate, NCM) with citric acid for the improved production of light aromatic hydrocarbons by catalytic pyrolysis of rape straw. Because of the dealuminization effect of citric acid on HZSM-5, mesopores were introduced, and the diffusion and conversion of pyrolysis gas over acid sites were improved. After metal loading with acid-leaching solution, the amount of weak and total acids in metal-loaded HZSM-5 increased a lot, which was conducive to the dehydration, deoxygenation, decarbonylation and aromatization of pyrolysis, and the production of monocyclic aromatic hydrocarbons (MAHs). With 0.1 mol/L citric acid for LFP and NCM treatment, the metal-loaded catalyst showed a higher yield of benzene, toluene and xylene (BTX) of 11.10 wt% during catalytic pyrolysis of rape straw. Compared with 0.1-NCM-H5, a higher yield of MAHs was obtained over 0.1-LFP-H5 with a more favorable pore structure and higher amounts of weak and total acid sites. In general, the high-valued utilization of agricultural wastes and spent lithium batteries was realized in this study to produce clean energy.

Selective hydrogenation of furfural to tetrahydrofurfuryl alcohol in isopropanol over hydrotalcite-derived nickel-based catalyst

A series of hydrotalcite-derived nickel-based catalysts were synthesized by coprecipitation, drying, calcination and reduction, and used for the selective hydrogenation of furfural to tetrahydrofurfuryl alcohol. Ni1Zr1Al2-R, with specific surface area (SBET) of 145.6 m2, narrow pore size distribution of 7.1 nm, and small Ni0 particle size of 7.31 nm, showed 100 % furfural conversion and 94.5 % tetrahydrofurfuryl alcohol selectivity under mild conditions (140 °C, 2 h). It was found that furfural was first hydrogenated to furfuryl alcohol, which was further hydrogenated to tetrahydrofurfuryl alcohol. XRD and TEM showed that Ni0 (111) plane played an important role on the catalytic hydrogenation process. Al increased the specific surface area (SBET) and total acid sites of the catalyst, providing more possibilities for the catalyst to contact the substrate. The introduction of Zr improved the ratio of medium acid sites and decreased the size of metal nickel particles, improving the resistance to carbon deposition and allowing the structure and catalytic performance to remain stable after five recycles.

Effect of thermal treatment on zeolite for real-time gas sensing of oxygenated volatile organic compounds

The breathable air is severally polluted due to the emission of various pollutants like volatile organic compounds (VOCs) and dust particles of submicron sizes. These pollutants have several adverse health hazards, which can cause fatal accidents and mortalities. In the current study, we have modified the FAU type of Zeolite (ZE) with the Si/Al to 1 and treated at different temperatures (300–600 °C) in a 10% H2 + 90% N2 mixture to achieve different distributions of oxygen vacancies. The presence of oxygen vacancy and electrons in the lattice is confirmed by EDAX, XPS and ESR techniques. The charge irregularities generated due to trapped electrons are exploited for detection of different VOCs like acetone, ethyl methyl ketone, isopropyl alcohol, ethanol, n-hexane, and benzene using the scanning kelvin probe (SKP) technique. The oxygen vacancies raise the distribution of Lewis and Brønsted basic sites, which impacts the interaction of VOCs with the sample surface and the amount of VOCs uptake. The untreated ZE and treated at 600 °C (ZE600) exhibited n-type behavior with 13.8% oxygen deficient sites with ∼1.9 μmol/g of total basic sites and 3 μmol/g of total acidic sites. The thermal treatment for ZE600 leads to ∼280 folds enhancement in surface photovoltage towards acetone with ∼ 67% of recovery concerning untreated ZE.

Ultrafast Synthesis and Regulating Al Status of Mesoporous ZSM-48 Zeolite via a Pretreated-Seed-Solution-Assisted Strategy

Ultrafast synthesis of nanocrystal assembled mesoporous ZSM-48 zeolite spheres of highly crystalline was achieved within 1.5 h by using pretreated-seed-solution-assisted strategy. Interestingly, by altering the introducing sequence of aluminum source (in the pretreated seed solution or in the synthesis gel), the obtained ZSM-48 with similar particle size and total acid sites exhibited quite different crystallization behavior and acid property in terms of Al distribution and acid strength, because of the distinct local microenvironment (Al-rich or Al-free) in the pretreated seed solution. The HZ48-Al-pre (introduce an Al source to the pretreated seed solution) had more framework Al(IV) content and stronger acid strength than that of the HZ48-Al-post (synthesized by the Al-free pretreated seed solution). The corresponding Pt supported catalysts showed a great difference in the n-C12 hydroisomerization reation. The Pt/HZ48-Al-pre catalyst had a very low selectivity (41.1%), and the maximum iso-yield was only 35.5%. However, the ultrafast synthesizedPt/HZ48-Al-post-1.5h catalyst exhibited a superior selectivity (90.1%) with a total i-C12 yield of 82.3% at 330 °C, which was a high level in the exist literature reports.

Enhanced CO2 desorption rate for rich amine solution regeneration over hierarchical HZSM-5 catalyst

High energy consumption during the carbon dioxide (CO2) desorption process in amine-based CO2 capture technology is a crucial hindrance to achieving carbon neutrality. HZSM-5 is one of the most widely reported solid acid catalysts used in primary amine regeneration. This work compared a series of HZSM-5 zeolites with different Si/Al ratios in terms of CO2 desorption performance. To further enhance catalytic activity, hierarchical HZSM-5 was synthesized by the dealumination and desilication re-assembly method with different acid and alkali concentrations. The experimental results suggested that desilication by modification in sodium hydroxide resulted in a significant improvement of mesoporous surface area. The NaOH-0.4 catalyst could improve the amount of desorbed CO2 by 40.3% and decrease the relative heat duty by 28.5%. And the cyclic tests revealed that catalytic activity was well preserved in the recycling process. Moreover, the structure and acidity of modification samples were characterized by X-Ray diffraction (XRD), Fourier transforms infrared (FT-IR), Nitrogen adsorption–desorption experiment, temperature programmed desorption of ammonia (NH3-TPD), Pyridine-adsorption infrared spectroscopy (Py-IR), and scanning electron microscopy (SEM). The characterization results suggested that the synergistic effect of larger mesoporous surface area and total acid sites was important to enhance catalytic CO2 desorption performance. These results showed a new understanding of catalyst design for CO2 capture technology by modifying the structure of the catalyst support.

Investigation on site-specific tolerance to water for solid acid catalysts employed for a model reaction of solketal formation

The glycerol value addition by ketalization with acetone leads to solketal. Herein, we demonstrate the comparative efficiency of Brønsted and Lewis acid sites, using Hβ-zeolite & sulfated zirconia (SO42--ZrO2) as Brønsted and Lewis acid catalysts, respectively, for ketalization of glycerol to solketal. The catalysts were characterized using conventional techniques. Total acidity of both catalysts was ascertained with NH3-TPD. The sulfur content of SO42--ZrO2 was determined by CHNS analysis. The Brønsted/Lewis character of total acid sites for both catalysts was determined using FTIR of pyridine-Chemisorbed catalysts. Studies revealed that 5% (w/w) catalyst, 25 °C temperature and 2-hour reaction time were optimum parameters for Hβ-zeolite while, SO42--ZrO2 required 50 °C to match the performance. Hβ-zeolite exhibited higher selectivity at lower temperatures towards ketal and reusability without any performance drop upto 10 cycles. The performance-edge vis-à-vis reusability of catalysts indicated tolerance of Lewis acid sites towards hydration, where Hβ-zeolite outperforms SO42--ZrO2.

Bioprocess development for levulinic acid production using sugarcane biomass

Developing technologies for converting lignocellulosic biomass to products such as energy, fuels, and value-added chemicals is an important step in making biorefineries a feasible alternative to the current oil-based productive system. In this study, the conversion of lignocellulosic biomass composed of a mixture of bagasse and sugarcane straw into a cellulose pulp and a sulfonated carbonaceous solid catalyst synthesized from lignin fraction were investigated, as well as the use of this solid acid catalyst to convert cellulose to levulinic acid, an important chemical platform. To overcome this challenge, firstly, the fractionation of lignocellulosic biomass was optimized. Then, tests were carried out to find the best condition for isolation of the soluble lignin from black liquor produced in the optimal condition of delignification. The lignin precipitate was subjected to carbonization tests followed by functionalization tests with concentrated sulfuric acid to synthesize the catalyst. This catalyst was then used to convert cellulose into levulinic acid (LA). The experimental design for cellulose recovery and lignin removal showed that under relatively mild reaction conditions of 110 °C, 117 min, and a solid/NaOH (4.4% w/v) ratio of 1:20, more than 91% of the lignin was dissolved into the black liquor, recovering a solid with a cellulose content higher than 78%. Lignin was fully recovered in the form of precipitate by simply reducing the pH of the black liquor to 3 (under this condition 11 g of precipitate were recovered per liter of liquor). Having the recovered lignin, it was then possible to synthesize a solid carbonaceous catalyst with a total acid site density of 1.48 mmol/g which was able to convert up to 17.11% of the cellulose and obtain yields of up to 38.55% of levulinic acid when a catalyst/cellulose ratio of only 8:10 (w/w) was used. Overall, the future of LA production using carbonaceous acid catalysts looks promising. As research in this area continues, there is the potential to further improve the production process and make it more cost-effective and sustainable. This could lead to wider adoption of this technology and increased use of levulinic acid in various industrial applications, including as a platform chemical to produce a range of chemicals and materials.

Influence of hot liquid flowing water on Zeolite Y stability

Zeolite Y is used in a wide field of catalysis because of its high surface area and strong acidity. Since flowing water is present in many catalytic liquid phase reactions, its impact was investigated. For that, the zeolite Y was treated with water at 200 °C and 42 bar in a flow reactor. The resulting characterization showed strong structural changes at high water flows. The typical zeolite structure was almost completely lost, but an amorphous phase similar to the faujasite framework was formed. Due to this, the characteristic micropores were destroyed (d = 0.7 nm, volume was reduced from 0.18 to 0.01 cm3/g) and small mesopores were created (d = 2–3 nm, volume was increased from 0.25 to 0.51 cm3/g). As a result, the specific surface area was not greatly reduced and was still at around 250 m2/g. In addition, the amount of octahedrally coordinated EFAl increased from 54 to 70% and a γ-Al2O3 as well as a kaolinite phase was observed. The formed tetrahedrally coordinated EFAl is responsible for EFAl-OH groups, which are strong Brønsted acid sites. In general, the total acid sites of the zeolite Y were not strongly reduced and the ratio of Lewis to Brønsted acid sites slightly increased from 70:30% to 80:20%. For all Al species, the oxygen coordination was strongly distorted. After water treatment, on Si a large number of coordinated OSi and OAl groups were substituted with OH groups. The ratio of Si to Al decreased from 1 to 0.7, because Si was dissolved out of the zeolite by the water. On the surface, it was vice versa, there the Si accumulated (the Si/Al ratio increased from 0.2 to 0.8), presumably as silica gel.

Graphitic carbon nitride (g-C3N4) as a super support for Mn–Ce based NH3-SCR catalyst: Improvement of catalytic performance and H2O/SO2 tolerance for NOx removal

Low temperature NH3 selective catalytic reduction (NH3-SCR) technology is an efficient and economical strategy for NOx removal. In this study, Mn–Ce oxides supported on graphitic carbon nitride (g-C3N4) was applied to the NH3-SCR of NOx at low temperature compared with Mn–Ce oxides supported on commercial TiO2, γ-Al2O3, and montmorillonite (MNT). The NOx conversion and H2O/SO2 tolerance of 8% Mn–Ce/g–C3N4–300 were superior to those of 8% Mn–Ce/TiO2-300, 8% Mn–Ce/γ-Al2O3-300 and 8% Mn–Ce/MNT-300 in the temperature window of 100–300 °C, and more than 95% NOx conversion could be obtained within the whole temperature range. According to the experimental and characteriazation results, the superior low temperature NH3-SCR performance of 8% Mn–Ce/g–C3N4–300 could be attributed to the formation of Ce–O–Mn solid solution structure, the higher concentrations of the surface elements, the optimun low-temperature reduction behavior, the largest amount of total acid sites, the highest (Mn4++Mn3+)/(Mn4++Mn3++Mn2+) and (Ce3+)/(Ce3++Ce4+) ratios, and the modest Oα/(Oα+Oβ) ratio.

Different alkali metals promoted Cr/Al2O3 catalysts for propane dehydrogenation

Unmodified Cr/Al2O3 and Cr/Al2O3 doping with different alkali metals (Li, Na, K) were prepared by the incipient wetness impregnation method. The surface elements of all the catalysts are evenly distributed and well loaded, and the addition of alkali metals does not change the crystal structure and surface texture. Both Cr6+ and Cr3+ species exist on all catalysts, and the addition of alkali metals can increase the amount of Cr6+ species, and Cr6+ species are basically converted into active Cr3+ species in the reaction thus increasing the initial propane conversion in the reaction. The addition of alkali metals reduced the amount of total acid sites and the strong acid sites of the catalyst, thus inhibiting the occurrence of side reactions and the formation of carbon deposition, and reducing the deactivation rate of the catalyst. Cr-0.5Na/Al2O3 exhibited the best catalytic performance and the lowest carbon deposition.

Graphite supported heteropolyacid as a regenerable catalyst in the dehydration of 1-butanol to butenes

1-butanol dehydration reaction has recently emerged as a sustainable route to produce butenes which can be further oligomerized to be applied as jet fuel. However, the high catalyst deactivation rates observed during this reaction due to coke deposition is still a pending matter. As promising catalysts for this reaction, we have supported two heteropolyacids (HPA), i.e. H4SiW12O40 (STA) and H3PW12O40 (TPA), on two commercial carbon materials: an activated carbon (AC) and a high surface area graphite (HSAG). Aiming to evaluate the role of HPA-support interactions, the STA was also dispersed over metallic oxides of different acidic nature, namely SiO2, Al2O3 and ZrO2. An exhaustive physicochemical characterization revealed that after the HPA dispersion thorough the support, the Keggin structure was maintained and an increase in the amount and strength of acid sites was provoked, but in different degree according to the HPA type and support’s nature. While the TPA-based catalysts developed less quantity of total acid sites, but higher strength than their STA-carbon counterparts, the STA/AC and TPA/AC samples exhibited a slight major amount of acid sites than STA/HSAG and TPA/HSAG. The HPA-support interactions have ultimately modulated to some extent the activity, selectivity, stability and regeneration ability of the synthesized catalysts, when applied in the gas phase butanol dehydration reaction at 275 °C. The higher STA decomposition temperature prompted by the graphitic support, among other factors, allowed the total regeneration of the highly active (39 mmolBuOH∙min−1∙ga.p) and n-butenes selective (>98 %) STA/HSAG catalyst by means of combustion of carbon deposits at 400 °C.

Understanding the cation exchange affinity in modified-MMT catalysts for the conversion of glucose to lactic acid.

This study investigated the exchange affinity of Fe3+, Cu2+, and Zn2+ cations in sulfuric acid-purified montmorillonite (S-MMT) to enhance Lewis acid sites and subsequently improve the catalytic conversion of glucose to lactic acid. XRD analysis suggested the successful cation exchange process, leading to structural expansion of the resultant cation exchanged-MMTs (CE-MMTs). XRF and TGA indicated that Zn2+ had the highest exchange affinity, followed by Cu2+ and then Fe3+. This finding was further supported by the results of TPD-NH3 analysis and pyridine-adsorption test, which demonstrated that Zn-MMT had the highest total acid sites (TAS) and the ratio of Lewis acid-to-Brønsted acid surface site (LA/BA). These results indicated dominant presence of Lewis acid sites in Zn-MMT due to the higher amount of exchanged Zn2+ cations. Consistently, time-dependent catalytic studies conducted at 170 °C showed that a 7 h-reaction generated the highest lactic acid yield, with the catalytic performance increasing in the order of Fe-MMT < Cu-MMT < Zn-MMT. The study also observed the impact of adding alcohols as co-solvents with water at various ratios on the conversion of glucose to lactic acid catalysed by Zn-MMT. The addition of ethanol enhanced lactic acid yield, while methanol and propanol inhibited lactic acid formation. Notably, a water-to-ethanol ratio of 30 : 70 v/v% emerged as the optimal solvent condition, resulting in ca. 35 wt% higher lactic acid yield compared to using water alone. Overall, this study provides valuable insights into the cation exchange affinity of different cations in MMT catalysts and their relevance to the conversion of glucose to lactic acid. Furthermore, the incorporation of alcohol co-solvent presents a promising way of enhancing the catalytic activity of CE-MMTs.

A comparative performance of heterogeneous catalyst derived from diatomaceous earth, empty fruit bunch, and montmorillonite treated by acid and metal oxide for ethyl lactate production

BackgroundCurrently, the rising demand for green chemistry and sustainable development encourages the creation and use of eco-friendly resources (industrial and agricultural wastes) for the production of high-value substants. In this study, solid-acid heterogenous catalysts derived by diatomaceous earth (DE), empty fruit branch (EFB), and montmorillonite (MMT) treated by sulfuric acid, phosphoric acid, and tungsten metal, respectively, were examined. Microwave-induced radiation was then used to improve both the DE and EFB surface. MethodsAll modified catalysts were accordingly used to produce ethyl lactate by esterification. Characteristics of sulfonated diatomaceous earth (DE-AC), phosphorous treated empty fruit branch (EFB-AC), and tungsten-supported montmorillonite (W/MMT) were analyzed using FTIR, XPS, NH3-TPD, XRD, SEM-EDX, BET, and TGA in order to examine their physical and chemical characteristics. Significant findingsThe DE-AC and W/MMT showed a high potential for usage as solid acid catalysts, containing 2981 and 1298 µmol/g of the total acid site, respectively. The yields of ethyl lactate for DE-AC, W/MMT, and EFB-AC were 58.55, 47.56, and 32.75%, respectively. Furthermore, DE-AC and W/MMT exhibit outstanding reusability for five consecutive cycles, indicating their potential as solid catalysts for ethyl lactate synthesis.

Ammonium Hexafluorosilicate (AHFS) Modified HMCM‐22 As Efficient Catalysts for Alkylation of Phenol with Methanol

AbstractA series of xAHFS/HMCM‐22 (x denotes the amount of AHFS treatment on HMCM‐22, AHFS is the abbreviation for ammonium hexafluorosilicate) were prepared and evaluated in the catalytic synthesis of p‐cresol by alkylation of phenol with methanol. Several characterization techniques including N2 adsorption‐desorption, XRD, FT‐IR, 27Al MAS NMR, Pyridine‐IR, and NH3‐TPD have been used to analyze the physicochemical properties of the xAHFS/HMCM‐22 catalyst. The conversion of phenol decreased with increasing x of xAHFS/HMCM‐22 catalyst; while the selectivity for p‐cresol maximized at x=0.07. The 0.07AHFS/HMCM‐22 catalyst was identified as the most efficient catalyst, showing the highest p‐cresol selectivity (53.3 %) for longer than 24 h under optimized reaction conditions (325 °C, WHSV=2 h−1), which is much higher than that of parent HMCM‐22 catalyst (37.1 %). The high p‐cresol selectivity of the catalyst is attributed to AHFS removing part of the acid sites on the external surface of the HMCM‐22, and preserving the acid sites in the micropores of zeolite. By contrast, the decrease in catalyst activity is due to the decrease in total acid sites.

WO3-based porous MCM-48 catalysts for renewable acrolein synthesis by the dehydration of glycerol

The gas-phase selective dehydration of glycerol to acrolein was studied over x%W (x: 5, 15, 25, and 35 %, w/w) supported on MCM-48. Microporous silica MCM-48 was synthesized to produce three-dimensional cubic crystals with a high surface area and resistance to hydrolytic pressure. Tungsten oxide (WO3) based solid acid catalysts supported on MCM-48 were prepared by two distinct synthesis methods, namely, oxalic acid added sol–gel (HSG) and nonhydrolytic sol–gel (NHSG) methods. The morphological and textural properties of catalysts were characterized by XRD, BET, SEM, Raman, XPS, and FT-IR techniques. The acidic properties of catalysts were elucidated by FTIR pyridine-adsorption and NH3-Temperature Programmed Desorption (NH3-TPD). The total surface acid sites’ concentration, Brønsted (B) and Lewis (L) acid concentrations, and B/(B+L) ratios were calculated from NH3-TPD and pyridine-FTIR. The steady acrolein yields were obtained with the optimal catalysts (15 %W and 25 %W loaded MCM-48 for HSG and NHSG, respectively). This study demonstrated that the medium-strength surface acidity and B/(B+L) ratios for glycerol dehydration to acrolein were correlated with both the activity and the selectivity of acrolein.

The Research on Anti-Nickel Contamination Mechanism and Performance for Boron-Modified FCC Catalyst.

Fluid catalytic cracking (FCC) is still a key process in the modern refining area, in which nickel-contamination for an FCC catalyst could obviously increase the dry gas and coke yields and thus seriously affect the stability of the FCC unit. From the points of surface acidity modification and Ni-passivation, in this paper, a boron-modified FCC catalyst (BM-Cat) was prepared using the in situ addition method with B2O3 as a boron source and emphatically investigated its mechanism and performance of anti-nickel contamination. The mechanism research results suggested that, in calcination, boron could destroy the structure of the Y zeolite and thus decrease the total acid sites and strong acid sites of the Y zeolite from 291.5 and 44.6 μmol·g−1 to 244.2 and 32.1 μmol·g−1, respectively, which could obviously improve the dry gas and coke selectivity of the catalyst and thus enhance the nickel capacity for BM-Cat; on the other hand, under hydrothermal conditions, boron could react with NiO and form into NiB2O4, which could obviously raise the range of the reduction temperature for NiO from 350–600 °C to 650–800 °C and thus promote the nickel-passivation ability for BM-Cat. Therefore, evaluation results of heavy oil catalytic cracking indicated that, under the same nickel-contamination condition, in contrast to the compared catalyst (C-Cat), the dry gas yield, coke yield, and H2/CH4 of BM-Cat obviously decreased by 0.77 percentage points, 2.09 percentage points, and 13.53%, respectively, with light yield and total liquid yield increasing by 3.25 and 2.08 percentage points, respectively, which fully demonstrates the excellent anti-nickel contamination performance of BM-Cat.