Hβ Catalysts Research Articles

Microwave-assisted pyrolysis of low-density polyethylene (LDPE)to value-added products over HY, HZSM-5 and Hβ catalyst

To reduce carbon emissions, environmental pollution, and to improve the circular economy, a microwave (MW) assisted pyrolysis of low-density polyethylene (LDPE)was carried out to yield valuable products such as aromatics, hydrogen, ethylene, and propylene gas. All three catalysts HY, HZSM-5 and Hβ were used as in-situ catalysts. Catalytic pyrolysis with HY, HZSM-5, and Hβ exhibited a lower liquid yield compared to non-catalytic pyrolysis. Gaseous fraction was mainly comprised of hydrogen, methane, ethylene, ethane, propylene, propane, and butane. It was found that methane (30.77 vol%) and hydrogen (55.24 vol%) were dominating gaseous products at 400 °C and 450 °C respectively using HY to LDPE ratio of 1:10. Whereas HZSM-5 facilitates formation of methane (65.94 vol%) at 400 °C and Ethylene (43.55 vol%) at 550°C. Hβ contributes to formation of alkanes and aromatics and gaseous products consist of majorly C3-C4 hydrocarbon gases which consist of 69.35 % propylene at 450°C. No sign of catalyst deactivation was observed even after 3 repetitive cycles.

Catalytic performance of Cu/Hβ catalysts for selective catalytic reduction of NO with NH3

A series of Cu(x)/Hβ catalysts were prepared by the impregnation method and the effect on the performance of the catalysts for the selective catalytic reduction of NO with NH3 (NH3-SCR) was investigated. Characterization techniques such as XRD, N2 adsorption-desorption, NH3-TPD, NO-TPD, H2-TPR, EDS and XPS were used to investigate the physical and chemical properties of the catalysts and the reason of the decrease of catalyst activity in the presence of SO2. It was shown that the catalyst Cu(3)/Hβ, the Cu loading was 3% and Cu(2)/Hβ, the Cu loading was 2%, exhibited the better catalytic activity when the initial reaction material contained no SO2 and SO2, and t95 was 169 and 225 °C, respectively. The analysis results of the catalyst before and after the reaction showed that the main reason for the decrease of catalyst activity in the presence of SO2 was that the ammonium sulfur salt which was formed by the reaction of SO2 and NH3 in the low reaction temperature covers the catalyst active center.

Ru-RuO2–Nb2O5/Hβ zeolite catalyst for high-active hydrogenation of lignin derivatives at room temperature

Cyclohexanol is an important intermediate used in the synthesis of a variety of high value-added chemicals. In this work, a novel Ru-RuO2-Nb2O5/Hβ catalyst was prepared and employed to directly hydrogenate phenol to cyclohexanol at room temperature. Moreover, the influence of Nb content and the reduction time on the activity of Ru-RuO2-Nb2O5/Hβ was investigated for obtaining the catalytic mechanism as well as the structural characteristics of the catalyst. The results showed that the phenol was almost converted into cyclohexanol with a high yield of 98.2 % via 0.3 %Ru2%Nb-Hβ-1 h catalyst at 30 °C and 2 MPaH2. The high hydrogenation activity at room temperature was attributed to the Ru-RuO2-Nb2O5 interface in catalyst via TEM, XPS, H2-TPR and NH3-TPD analysis. Moreover, the DFT calculation results showed that Nb2O5 inhibited the reduction of RuO2 species, resulting in the formation of Ru-RuO2-Nb2O5 interface and the adsorption of phenol on the Ru-RuO2 interface was stronger than Ru sites.

A study on the production and engine analysis of organic liquid fuel from jatropha and castor oil by catalytic cracking over solid acid catalysts

Catalytic cracking of non-edible oils such as jatropha and castor was done in fixed bed catalytic reactor. The microporous catalysts such as Hβ, HY and HZSM-5 and mesoporous catalyst like AlMCM-41 were synthesised and characterised by XRD and BET surface area analyzer. The reaction parameters such as temperature of reaction, WHSV (Weight hourly space velocity) and reaction time were optimised over Hβ catalyst using jatropha oil. Organic liquid products (OLP) comprising of green gasoline (GG), green kerosene (GK) and green diesel (GD) and gaseous products were found to be major products. The liquid products were analysed using gas chromatograph (Shimadzu GC-9A) fitted with Apeizon-L packed column and gaseous products were analysed using Poropak Q column. The % conversion, yield of OLP and selectivity towards GG, GK and GD were found to be higher at temperature of 400 °C, WHSV of 4.8 h−1 and reaction time of 1 h. The cracking of jatropha oil was done over HY, HZSM-5 and AlMCM-41 at this optimised condition. Among the microporous materials HZSM-5 produced more OLP with more selectivity towards GG fraction (50%) but yielded higher % of gaseous products. While AlMCM-41 (Si/Al = 25) was selective towards middle distillates fraction like GK (45%) & GD (35%) and yielded low gaseous products. The mechanism of reaction proceeds via carbocation formation. The activity of HZSM-5 and AlMCM-41 were examined with castor oil. The OLP viability as a replacement fuel in a single-cylinder diesel engine under various loads was evaluated in an IC engine test. Here, we look at how different engine operating conditions affect fuel efficiency, Brake Thermal Efficiency (BTE), and emissions of Carbon Monoxide (CO), Carbon-di-oxide (CO2) and Nitrogen Oxide (NOx). Overall analysis indicates that OLP cracked from Jatropha oil serves as a best fuel in comparison with OLP obtained from Castor oil.

Dealuminated Hβ zeolite for selective conversion of fructose to furfural and formic acid

The fructose-to-furfural transformation is facing major challenges in the selectivity and high efficiency. Herein, we have developed a simple and effective approach for the selective conversion of fructose to furfural using Hβ zeolite modified by organic acids for dealuminization to regulate its textural and acidic properties. It was found that citric acid-dealuminized Hβ zeolite possessed high specific surface areas, wide channels and high Brønsted acid amount, which facilitated the selective conversion of fructose to furfural with a maximum yield of 76.2% at 433 K for 1 h in the γ-butyrolactone (GBL)-H2O system, as well as the concomitant formation of 83.0% formic acid. The 13C-isotope labelling experiments and the mechanism revealed that the selective cleavage of C1–C2 or C5–C6 bond on fructose was firstly occurred to form pentose or C5 intermediate by weak Brønsted acid, which was then dehydrated to furfural by strong Brønsted acid. Also this dealuminized Hβ catalyst showed the great recycling performance and was active for the conversion of glucose and mannose.

One-pot synthesis of 2-ethylanthraquinone from phthalic anhydride and ethylbenzene over a Sc-modified Hβ catalyst

2-Ethylanthraquinone is frequently used for producing bulk consuming chemicals. However, the synthesis of 2-ethylanthraquinone is still restricted by expensive raw materials, complex preparation process and poor-cycling catalyst. Herein, a one-pot method is developed to synthesize 2-ethylanthraquinone using phthalic anhydride and ethylbenzene as feedstock by combination of acylation and dehydration over a Sc-modified Hβ catalyst. Sc-modified Hβ was prepared via impregnation and catalyzed conversion of phthalic anhydride about 58.8% and 2-ethylanthraquinone selectivity up to 78.5% which is better than the results by other metals-modified Hβ zeolites. By adjusting Sc loading amount in Hβ, more acids are created especially strong Lewis acid and an appropriate synergistic effect of Lewis/Bronsted acids is obtained for cascade reactions of acylation and dehydration. Then, the reaction conditions were investigated and the catalyst can be reused in 4 runs. This work provides a green and simple way for 2-ethylanthraquinone synthesis.

Stereoselective Hydrogenation of Platform Molecule α‐Pinene Under Solvent‐Free Conditions

AbstractStereoselective hydrogenation of α‐pinene over heterogenous catalysts under solvent‐free conditions is promising for biomass conversion but challenging. Herein, we prepared the Ru‐NiO/Hβ catalysts using chemical reduction and galvanic replacement methods. With the increase of Ni content, the selectivity of cis‐pinane was significantly improved. A high conversion of 100 % and a high cis‐pinane selectivity of 98 % were achieved after 4 h reaction at 80 °C. It has been verified that the addition of Ni can adjust the ratio of Brønsted and Lewis acid, regulate the hydrogen spillover between Ru and support, change the adsorption site of substrate and form steric hindrance effect. All these contribute to the better selectivity of the catalyst. In addition, catalysts presented good stability in the 900 h test.

Selective organic phase hydrodeoxygenation of typical phenolic monomers and two lignin oils over highly active Pd/Hβ catalyst for high-grade bio-fuel production

The selective hydrodeoxygenation (HDO) of lignin-derived bio-oil still meets the great challenges due to its complex oxygenated organic component. In this research, first time, Pd-based zeolite catalysts were prepared by the modified deposition-precipitation (DP) method for the HDO conversion of guaiacol. Notably, for the same Si/Al ratio of zeolite, Pd2%/Hβ catalyst showed the higher catalytic activity on the HDO of guaiacol than that Pd2%/M and Pd2%/HZSM-5 catalyst, which mainly originated from the synergetic effect between metal nanoparticles size and acid sites of catalyst. As one of typical phenolic monomers, guaiacol can be converted into high yield of hydrocarbons under the condition of 220 °C, 3 MPa H2, and 4 h in n-hexane over Pd2%/Hβ (DP) catalyst. This highly active catalyst exhibited the good recyclability in the HDO conversion of guaiacol. In addition, other typical phenolic monomers can be converted into high yield of hydrocarbons over this highly active catalyst. Considering this, after HDO upgrading, real lignin oil (RLO) can be converted into high yield of hydrocarbons with the carbon number (CN) in range of C7-C15. This work highlighted that the depolymerization monomers from lignin can be further upgraded by this high active catalyst through HDO to obtain jet hydrocarbons fuel.

Catalytic and noncatalytic fast pyrolysis of waste tires to produce high-value monocyclic aromatic hydrocarbons

In this work, catalytic and noncatalytic fast pyrolysis of waste tires were studied in an analytical pyrolyzer coupled with gas chromatography-time-of-flight mass spectrometry to obtain valuable monocyclic aromatic hydrocarbons (MAHs), especially benzene, toluene, ethylbenzene, xylene etc. (BTEX). The various influencing factors such as the heating rate (10−20000 °C/s), atmosphere (He, H2, N2, CH4, O2), temperature (500−800 °C), and time (5−30 s) were explored. The heating rate and temperature had the greatest influence on the distribution of pyrolysis products, where 40.91 % MAHs were obtained at 500 °C/s and 750 °C in helium atmosphere. In the process of catalytic fast pyrolysis, the nine zeolite catalysts were investigated. The Hβ catalyst is conducive to the formation of MAHs (up to 53.09 %), while the content of BTEX was only 9.05 %. The MCM-41Q catalyst is beneficial to the formation of BTEX (22.35 %), as the content of MAHs was 46.09 %.

Cleaner Production of Methyl Benzoate Using Solid Heterogenous Catalyst via Electromagnetic Waves as an Energy Source

Methyl benzoate (MB) is synthesized in a batch reactor conventionally and with the use of microwave (MW) energy as a source of heat. MW-assisted esterification has added advantage of competent energy use in volumetric region which provides a safe, economic and green method of heating. In microwave-assisted MB esterification, the amount of solvent is minimized. Also this work aims to study the product distribution and selectivity using heterogeneous zeolite Hβ catalyst. The esterification is studied by variation in operating conditions such as reaction time, feed composition, microwave energy and reaction temperature. It has been found that 88% conversion of BA with 74% selectivity of MB is formed using a conventional batch reactor, while with the use of MW energy as a source of heating, at 70 °C, 300 W MW power, 99.99% conversion of BA was achieved within 10 min with the highest selectivity of 86% using sulfuric acid and 67% of MB using Hβ catalyst, respectively.

Bimetallic Bifunctional Pt-NiP/Hβ as a Novel and Highly Efficient Catalyst for n-Hexane Isomerization

A novel bimetallic bifunctional Pt–NiP/Hβ isomerization catalyst was successfully prepared by introducing a small amount of noble metal Pt into the NiP on the Hβ carrier. The catalyst demonstrated superior catalytic activity to Pt/Hβ and NiP/Hβ catalysts for n-hexane isomerization, due to the good surface property, the synergistic effect of the two metals, the suitable match between acid site and metal site, as well as good reduction stability. The effects of Pt loading and NiP addition amount on the surface property were studied comprehensively through a series of characterization, and the correlation among surface property with catalytic behavior was also analyzed. The results indicated that the Pt (0.1 mol%)–NiP (10 mol%)/Hβ catalyst had good structural characters, surface acid property and an uniform distribution of NiP and Pt active components on surface, which is helpful to obtain a highly efficient catalytic performance. Additionally, the influence of reduction/reaction conditions on the catalytic activity, as well as the catalyst tolerance to water and thiophene sulfur, was investigated furtherly.

Synthesis of Cumene from Lignin by Catalytic Transformation

Cumene is an important intermediate and chemical in chemical industry. In this work, directional preparation of cumene using lignin was achieved by a three-step cascade process. The mixture aromatics were first produced by the catalytic pyrolysis of lignin at 450 °C over 1%Zn/HZSM-5 catalyst, monocyclic aromatics with the selectivity of 85.7 wt% were obtained. Then, the catalytic dealkylation of heavier aromatics resulted in benzene-rich aromatics with 93.6 wt% benzene at 600 °C over Hβ catalyst. Finally, the cumene synthesis was performed by the aromatic alkylation, giving cumene selectivity of 91.6 C-mol% using the [bmim]Cl-2AlCl3 ionic liquid at room temperature for 15 min. Besides, adding a small amount of methanol to the feed can efficiently suppress the coke yield and enhance the aromatics yield. The proposed transformation potentially provides a useful route for production of cumene using renewable lignin.

Catalytic conversion of 2,5-dichlorotoluene over Hβ zeolite, Ag/Hβ and Cu/Hβ catalysts in N2 or H2 atmosphere

2,6-Dichlorotoluene (2,6-DCT), 2,4-dichlorotoluene (2,4-DCT), dichlorobenzenes (DCB), and dichloroxylene (DCX) were selectively synthesized through the catalytic conversion of 2,5-dichlorotoluene (2,5-DCT) over Hβ (SiO2/Al2O3 = 25) zeolite, Ag/Hβ, and Cu/Hβ catalysts in a N2 or H2 atmosphere. When Hβ zeolite was used as the catalyst at 310−350 °C in a N2 atmosphere, DCB, 2,6-DCT, 2,4-DCT, and DCX with the selectivities of ca. 28, 15, 17, and 22% were formed as the main products. When the Ag/Hβ catalysts with high Bronsted acid amount catalyzed the conversion of 2,5-DCT, 2,4-DCT with the selectivities of 71.9–83.9% was formed at 310 and 330 °C. The catalytic activities over the Cu/Hβ catalysts were similar to that over the Hβ catalyst. In a H2 atmosphere, the Ag2/Hβ and Cu10/Hβ catalysts favored the 2,5-DCT hydrogenation to DCB with the selectivities of around 40 and 58%, respectively. The acidity and metal type of the catalyst played important roles in the catalytic conversion of 2,5-DCT to chlorinated aromatics.

Catalytic pyrolysis of flame retarded high impact polystyrene over various solid acid catalysts

The catalytic pyrolysis of flame retarded high impact polystyrene (Br-HIPS) was performed in the presence of five different solid acid catalysts in order to remove the bromine from the derived pyrolysis oil. The catalysts were three zeolite materials (HY, Hβ and HZSM-5) and two mesoporous solids (all-silica MCM-41 and active Al2O3). The results showed that in the presence of HY and Hβ zeolites, a reduction of approximate 50wt.% in oil yield and a corresponding increase in wax and gas yields were obtained compared to thermal degradation. The addition of HZSM-5 showed less impact on product distribution and produced more oil compared with the other zeolites. The mesoporous catalyst of all-silica MCM-41 obtained the highest oil yield of 67.9wt.% and reduced the wax yield to 8.73wt.%. In terms of the composition of the pyrolysis oil, HZSM-5 and all-silica MCM-41 were favorable to produce more valuable single ring aromatics, such as toluene, ethylbenzene and cumene. Moreover, the catalysts exhibited pronounced debromination performance, especially the Hβ catalyst, achieving the debromination efficiency of 70.47%. The results confirmed the catalytic pyrolysis of Br-HIPS and debromination performance was well related to the textural properties of catalysts.

Methanol to hydrocarbons reaction over Hβ zeolites studied by high resolution solid-state NMR spectroscopy: Carbenium ions formation and reaction mechanism

Carbenium ions as active intermediates play very important roles in methanol conversion to hydrocarbons (MTH) reactions, while their observation and structure confirmation is of great difficulty. In this contribution, solid-state magic-angle-spinning (MAS) NMR spectroscopy has been applied in the investigation of methanol conversions over Hβ zeolite. By attempting the batch-like and continuous-flow reactions over the catalysts with varied acid site densities and under the condition of different reaction temperatures and atmosphere pressures, an optimized way for direct observation of carbenium ions has been developed. For the first time, two types of carbenium ions, including methylcyclopentenyl (MCP+) cations and heptamethylbenzenium (heptaMB+) cation, have been successfully captured by 13C MAS NMR during methanol conversion over Hβ zeolite. For the batch-like reactions, methanol conversion and carbenium ions observation have been promoted by using the Hβ catalysts with more Brönsted acid sites and performing the reaction under relatively high atmosphere pressure. The competitive adsorption from reactants and products on the catalyst surface may cause the deprotonation of the carbenium ions. In the continuous-flow reactions, both the heptaMB+ and MCP+ cations are formed and more easily observed compared with batch-like reactions due to the improved methanol conversion and the reduced competitive adsorption on the Brönsted acid sites. Based on the carbenium ions identification, a catalytic cycle is proposed to explain the generation of isobutene, a predominantly generated product on Hβ zeolite, during methanol conversion.

Vapor Phase Synthesis of Annelated Pyridines over Metal Modified Zeolite Beta

Vapor phase synthesis of annelated pyridines from cyclic ketones, aldehydes and ammonia was carried out over various zeolite molecular sieves like Hβ, HZSM-5 (240), HZSM-5 (40), HY, HX, HMCM-41 and Mordenite. The preliminary screening of catalyst clearly shows that Hβ catalyst was found to be more active for the vapor phase synthesis of annelated pyridines. Hβ was further modified with transition metals like Fe, Cu, Pb, Mo, Zn, Ni, Co, Ce, W and Sn to get higher yields.

The one-pot synthesis of methylene diphenyl-4,4′-dicarbamate

Methylene diphenyl-4,4′-dicarbamate (MDC) is an intermediate for the preparation of methylene diphenyl diisocyanate. This paper reports the one-pot synthesis of MDC using aniline, dimethyl carbonate, and formalin as raw materials. Phenyl N-methyl carbamate (MPC) synthesis was carried out in a batch reactor using Zn(OAc)2 as the catalyst, following which, without any separation, an Hβ catalyst and formalin were added to continue to MPC condensation to give MDC. It was found that there were interactions between the MPC synthesis and MPC condensation, such that the presence of aniline could inhibits MPC condensation. Zn(OAc)2 was also found to adsorb on the Hβ surface to form Si–O–Zn bonds during the condensation, decreasing the quantity of strong acid sites on the Hβ and reducing the catalytic performance. Under the optimal conditions for the one-pot synthesis of MDC, aniline conversion was 100% and the MDC yield was 73.9% (based on HCHO). The deactivated catalyst could be easily regenerated by treatment with acetic acid. The filter cake was dried and calcined to obtain regenerated Hβ and the filtrate was dried by vacuum rotary evaporation to obtain Zn(OAc)2. No significant loss in catalytic activity was observed for the regenerated catalyst.

Catalytic Cracking Using an Hβ Catalyst for the Production of Green Fuel: Optimization Studies

The present study reports the synthesis; characterization by X-ray diffraction, Brunauer, Emmett and Teller surface area analyzer, inductively coupled plasma, and temperature programmed desorption techniques of Hβ catalyst; and its catalytic cracking activity towards jatropha oil using a fixed bed flow reactor. The catalytic reaction parameters, such as influence of temperature (400–500°C), weight hourly space velocity (3.8–6.2 h−1), and time of reaction (1–4 h) on percentage conversion of jatropha oil and percentage yield of bio liquid products were studied and optimized over Hβ. Under the optimized conditions, Hβ showed 48% conversion and 30, 45, and 25% selectivities toward green gasoline, green kerosene, and green diesel, respectively.

Solvent Free Selective Isomerization Of p-diethylbenzene To m-diethylbenzene Using Modified Hβ Zeolites

Solvent free and selective isomerization of p-diethylbenzene (p-DEB) to m-diethylbenzene (m-DEB) was carried out using metal modified zeolite Hβ at high temperature. The metal modification of Hβ catalyst was carried out by using typical Lewis acidic cations Al 3+ , Fe 3+ , Ti 4+ , Sn 4+ and Sb 3+ . The catalysts were characterized by XRD, FE-SEM, HR-TEM, FT-IR, N2-desorption (BET), ICP-AES, NH3-TPD, pyridine-IR, and TGA techniques for structure, morphology, acidity and stability. Particle size of the crystallites was determined by HR-TEM and the size was in the range of 15 - 35 nm. At 250oC, Al-Hβ, Fe-Hβ and Ti-Hβ catalysts showed 69 - 75% conversion of p-DEB with 43 - 51% selectivity towards m-DEB. This process is a greener alternative to the classical AlCl3 process. Further, such an isomerization would make the styrene manufacture more economic.

Condensation Reaction of Methyl N-Phenylcarbamate with Formaldehyde over Hβ Catalyst

The condensation reaction between methyl N-phenylcarbamate (MPC) and HCHO to form methylene diphenyl-4,4′-dicarbamate (MDC) over different solid acid catalyst was studied. The results showed that t...