Trace Olefins Research Articles

Alkylation for removing trace olefins from reforming aromatics over novel Al2O3@SO42-/ZrO2 catalysts derived from the ZrO2-coated γ-Al2O3 strategy

Sulfated zirconia, as a promising catalyst in various acid-catalytic reactions, still suffer from unsatisfactory catalytic stability and regeneration performance due to severe leaching of sulfur species, while aluminum modification can effectively overcome these drawbacks. Unfortunately, the limited acceptability of aluminum content by co-precipitation and milling methods remains a critical issue. Herein, an effective strategy of coating sulfated zirconia on the surface of γ-Al2O3 was developed to synthesize the novel Al2O3@SO42-/ZrO2 catalyst with high aluminum content. The synthesis variables were investigated and systematically optimized. The structural and acidic properties of Al2O3@SO42-/ZrO2 were determined by XRD, HR-TEM equipped with EDX, N2 adsorption-desorption isotherms, EA, FT-IR, NH3-TPD and Py-FTIR. Results indicated that the unique structure constructed by sulfated zirconia coated on γ-Al2O3 not only realized the stabilization of favorable tetragonal zirconia phase even at exceedingly high aluminum content but also promoted Brønsted acid sites. Accordingly, the optimal Al2O3@SO42-/ZrO2-50% performed outstanding catalytic activity and stability, given the olefins conversion of 98%-75% during the continuous reaction experiment. Owing to the alleviation of sulfur loss by Al-promoting effects, excellent regeneration performance, with olefins conversion only slightly declining after 4 consecutive reaction-regeneration cycles, was also obtained. The mechanistic pathway for the alkylation of olefins with aromatics over Al2O3@SO42-/ZrO2 was also investigated and proposed by GC–MS analysis.

Highly efficient mesoporous ZSM-5 for trace olefin removal from aromatic stream

Steam cracking and reforming processes always produce aromatic streams containing trace amounts of olefins, which are harmful to certain processes and applications in the petrochemical industry. In the aromatics complex, clay is used to remove trace olefins. Unfortunately, it has a limited lifespan and must be replaced frequently. In this study, mesoporous ZSM-5 is investigated for its application in the removal of trace olefins. It is prepared using two templates: Tetrapropylammonium bromide and Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, resulting in a mesoporous structure with a high pore volume and external surface area. There is an optimum amount of DMOD necessary to achieve the desired degree of mesoporosity within a zeolite. Even though mesoporous ZSM-5 has a similar surface area to microporous ZSM-5, its external surface area is 1.3 to 2.0 times greater than conventional ZSM-5. Consequently, mesoporous ZSM-5 has a higher activity when it comes to removing trace olefins from an aromatic stream than microporous ZSM-5.

Application of supported Cu–Ru catalysts for the removal of trace olefins in aromatics

AbstractExploring reliable hydrogenation catalysts to remove trace olefins in aromatic hydrocarbons through hydrogenation is an important topic. In this paper, a bimetallic Cu–Ru/montmorillonite (Cu–Ru/M) catalyst was prepared using a step-by-step impregnation method, and the effects of bimetallic catalysts on removing olefins were assessed. The catalysts were characterized using X-ray diffraction, Brunauer–Emmett–Teller specific surface area, inductively coupled plasma atomic emission spectrometry, high-resolution transmission electron microscopy and temperature-programmed reduction of H2. The results show that there is a strong interaction between Cu and Ru on the Cu–Ru/M catalyst, which improves the dispersion of the metals on the surface of the support M. The hydrogen spillover phenomenon of Cu–Ru/M enhances its activity and adsorption capacity for hydrogen species. The catalytic performance test confirmed that the bimetallic catalyst has significantly greater activity and stability. The optimal loadings are 5% copper and 1% ruthenium, and the performance of this catalyst is comparable to those of noble-metal Pt/M catalysts.

Effective Catalyst for Removing Trace Olefins from Reforming Aromatics: Sulfated Zirconia with High Sulfur Content Synthesized by Sulfonation with Chlorosulfonic Acid

Effective Catalyst for Removing Trace Olefins from Reforming Aromatics: Sulfated Zirconia with High Sulfur Content Synthesized by Sulfonation with Chlorosulfonic Acid

Efficient removal of trace olefins in aromatics by novel acetamide-based acidic deep eutectic solvents

The alkylation of olefins with aromatics (AOA) is considered an attractive method for removing trace olefins from aromatics. The catalyst with appropriate acidity is an important feature to control the alkylation reaction. In this work, a series of innovative acetamide (AC)-based acidic deep eutectic solvents (ADESs) with different organic sulfonic acids as hydrogen-bond donors (HBDs) were synthesized and used in AOA. The formation mechanism of ADES was investigated utilizing FT-IR spectroscopy, 1H NMR, and quantum chemistry calculations combined with the phase diagram. In addition, the factors affecting the removal of olefins were further studied. Under optimal conditions, the most effective ADES ([AC:2TfOH]) can achieve 100% olefin conversion, and it can still reach 90% after 8 cycles. Finally, the mechanism of ADES ([AC:2TfOH]) catalyzed alkylation of aromatics and olefins was first investigated and proposed by in-situ diffuse reflectance infrared spectroscopy (in-situ DRIFT) and gas chromatography-mass spectrometry (GC–MS).

Synthesis of Al-incorporated sulfated zirconia with improved and stabilized surface sulfur species for removal of trace olefins from aromatics

Incorporating Al into zirconia significantly improves and stabilizes the surface sulfur species. The outstanding catalytic performance of Al-incorporated sulfated zirconia was obtained when it was applied in removing trace olefins from aromatics.

Alkylation for Removing Trace Olefins from Reforming Aromatics Over Novel Al2o3@So42-/Zro2 Catalysts Derived from the Zro2-Coated Γ-Al2o3 Strategy

Alkylation for Removing Trace Olefins from Reforming Aromatics Over Novel Al2o3@So42-/Zro2 Catalysts Derived from the Zro2-Coated Γ-Al2o3 Strategy

Optimizing temperature and introducing new process arrangements for elevating clay's longevity based on the known poisons in the separation process of trace olefins from aromatics

AbstractBACKGROUNDThe clay treatment widely utilized to reduce unsaturated components in aromatic stream has a detrimental effect on catalyst lifetime. Due to the short lifetime of commercial clay, a huge number of studies have been carried out to address this problem over the last decade. This study aims to optimize the temperature for longer serviceability of clay by removal of unsaturated aliphatic components from aromatic streams through the adsorption and catalytic properties of clay. A novel process arrangement is introduced by scheduling the reuse of deactivated clay that is discarded after deactivation.RESULTSResults showed that the suitable range of temperature for olefin removal is 155–205 °C, and the optimum temperature with the lowest operational cost was 185 °C, which is then gradually elevated to 205 °C.CONCLUSIONThe new process arrangements utilize these results and elevate clay's lifetime by almost 3.5 times, leading to an economical solution on an industrial scale. © 2021 Society of Chemical Industry (SCI).

Selection of suitable bentonite and the influence of various acids on the preparation of a special clay for the removal of trace olefins from aromatics

AbstractAcid-activated clays are inexpensive materials that are used extensively in the removal of unsaturated compounds on an industrial scale. The performance of bentonitic clays in removing these compounds relies heavily on the types of raw clays and acids used in the activation process. In this work, we report on the removal of olefins from aromatic streams by bentonitic clays activatedviatwo different routes. After preliminary tests of four different natural clays, the best clay was selected in terms of it having high swelling index, cation-exchange capacity, specific surface area and suspension stability values. Activation was achieved with hydrochloric acid (HCl) and sulfuric acid (H2SO4), and olefin removal was evaluated after holistic clay characterization by means of X-ray diffraction, X-ray fluorescence, Brunauer–Emmett–Teller (BET) specific surface area analysis, ζ-potential analysis, Fourier-transform infrared (FTIR) spectroscopy after treatment with pyridine, scanning electron microscopy and transmission electron microscopy. The increased basal spacing, replacement of H+with interlayer cations and retained structural stability of the clay after acid treatment contributed to the improvement of olefin removal for HCl-activated clay. The HCl-activated clay was more efficient in terms of olefin removal than its H2SO4-activated counterpart, removing up to 90% of olefin components after 40 h. Based on pyridine-FTIR spectra and quantitative measurement of the acidic properties of the samples, HCl treatment increased the total number acid sites (Brønsted and Lewis) by approximately ninefold compared to the pristine natural clay and by approximately fourfold compared to the H2SO4-activated clay.

Gas-assisted exfoliation montmorillonite into mono-layered nanosheets for the removal of olefins from aromatics

To date, the scalable exfoliation of the resource-rich montmorillonite (MMT) into high-quality few-layered nanosheets still remains a grand challenge. Herein, a simple, nontoxic, and efficient strategy is proposed to exfoliate layered MMT into mono-layered MMT nanosheets (MMTNS) via thermal expansion gas-assisted exfoliation method. The essence of this method is that the high temperature expands the interlayer distance while weakens the van der Waals force between interlayer of bulk MMT and then the liquid nitrogen (L-N2) penetrated the interlayers can be quickly vaporized to exfoliate the MMT. With a high mass yield of 18–20%, the prepared MMTNS has a thickness around 1.9 nm and a reasonable aspect ratio (lateral dimension of 0.5 µm-3 µm). Meanwhile, no impurities were introduced during the whole procedure. Additionally, the exfoliated MMTNS with high specific surface area (402 m2 g−1) and more exposed acid sites is further applied for the removal of trace olefins from aromatics, the result shows higher olefin conversion (76.97%) than its parent bulk phase (50.66%). The possible reaction mechanism of removing olefins from aromatics was further proposed and investigated by gas chromatography-mass spectrometry (GC–MS).

Developing an Efficient Catalyst Based on Thermal and Acid-Treated Clay for the Removal of Trace Olefins From Aromatic Compounds

AbstractBentonite is used as a catalyst in the removal of olefins from aromatic compounds and the present study was designed to investigate how its performance might be improved by various treatments. Bentonite from Semnan mine, Iran, was used in the study following initial characterization. In order to investigate the effect of acid and thermal treatments on the removal of olefins from aromatic compounds, bentonite samples were modified using HNO3 at different concentrations (0.15, 0.3, 0.5, 0.7, 1, and 2 M) and were also at temperatures between 100 and 340°C for 3 h. To examine the catalytic activity of bentonite-based catalysts, the samples were evaluated after running batch and continuous experiments. The optimum catalyst was characterized using thermo-programmed desorption (TPD) of NH3 to examine the acidic sites. Scanning Electron Microscopy (SEM) images, nitrogen adsorption-desorption isotherms (BET analysis), and X-ray diffraction (XRD) patterns were used to study the structural changes of the bentonite produced by the acid and thermal activation. The removal of olefins by the catalysts in batch and continuous systems revealed that the sample modified with 0.3 M Nitric acid at 150°C had superior catalytic activity, with olefin conversion remaining at >50% for up to 20 h. Nitrogen adsorption-desorption isotherms showed that acid treatment can produce a mesoporous structure. On the other hand, the TPD analysis indicated that during weak acid treatment, some cations, such as Al3+ and Fe3+, were leached from octahedral sheets and the interlayers of the clay mineral resulting in weak acid sites being generated. Finally, a novel method was proposed and tested for measuring the Bromine Index (BI) using potentiometric titration.

Efficient Removal of Trace Olefins in Aromatics by Novel Acetamide-Based Acidic Deep Eutectic Solvents

Efficient Removal of Trace Olefins in Aromatics by Novel Acetamide-Based Acidic Deep Eutectic Solvents

Research and application of a non-noble metal catalyst in the removal of trace olefins from aromatics

Cu/ZnO/montmorillonite is a high-performance catalyst in the removal of trace olefins from aromatics.

Zeolite-based catalysts for the removal of trace olefins from aromatic streams

Removal of trace olefins from aromatic liquids was investigated on UZM-8 and MCM-22, which are the family of MWW zeolites. Both these zeolites were synthesized with similar Si/Al ratio and characterized by various techniques such as XRD, SEM, ICP, N2 adsorption, Ammonia TPD and solid-state MAS-NMR. Olefin conversion activity over UZM-8 was found to be significantly higher than that of MCM-22. In addition to this, deactivation of UZM-8 was slower than the MCM-22. UZM-8 with irregular stacking of MWW layers possess high external surface area and exposes more number of active sites to the reactant molecules. Mesopores generated due to the disordered layers of UZM-8 allows the fast diffusion of the substrate molecules in which pore clogging does not occur, thus making it more active and slow deactivation than that of MCM-22.Graphic abstract

Synthesis of Ce-MCM-22 and its enhanced catalytic performance for the removal of olefins from aromatic stream

Cerium incorporated MCM-22 (Ce-MCM-22) was successfully synthesized by hydrothermal method. Incorporation of Ce is achieved by the optimization of method for synthesis by varying (i) Concentration of sructure directing agent or template, (ii) Silica to ceria ratio and (iii) Crystallization time. Change in phases during crystallization, variation of physico-chemical properties with respect to gel composition and framework substitution of cerium are evidenced by XRD, UV–Vis DRS, SEM, N2 adsorption, FT-IR, Ammonia TPD and solid-state MAS-NMR characterisations. It is found that incorporation of Ce into the zeolite frame work has successfully occurred by simple method of optimisimg molar gel composition. Interestingly, prepared samples of Ce-MCM-22 have also been found to be more effective catalysts for the removal of trace olefins from aromatic streams.

Removal of Olefins from Reforming Aromatic Hydrocarbons over Metal-Halide-Modified Acid-Activated Palygorskite

A series of acid-activated palygorskite (PAL)-supported metal halides catalysts were synthesized and applied to remove trace olefins from aromatic hydrocarbons. The structural properties and surfac...

Detecting and Evaluating Detrimental Factors of Clay’s Longevity, Selecting, and Optimizing an Appropriate Adsorbent for Operating Time Elevation in the Separation Process of Trace Olefins from Aromatics

Industrial-scale production of aromatic materials is confronted by the problem of removal of impurities such as olefins. Their removal is an essential requirement in marketability. Catalytic adsorbent clay is the most common material used for the removal of olefins from aromatic streams. The current study is focused on increasing the lifetime of a commercial type of clay by identifying the effective parameters in reducing the adsorbent lifetime. An analysis of 3 years of data from a petrochemical complex showed that water, morpholine, and N-formyl morpholine (NFM) contents in the feed stream are the factors reducing the clay lifetime. Various experiments have been performed to determine the individual impacts of these parameters on the clay lifetime. Reducing the water content from 150 to 70 ppm led to a 20% increase in lifetime, while increasing morpholine content from 55 to 160 ppm and NFM content from 0.55 to 91 ppm resulted in 40 and 75% reduction in lifetime, respectively. Also, six types of conventional commercial adsorbents have been tested to minimize the contents of the above-mentioned components before olefin removal by clay. Among them, silica gel showed the best performance. The optimum weight percentage of silica gel relative to the total loaded clay mass was determined to be 10%, which led to a 2.1-fold increase of clay lifetime if silica gel was loaded into the reactor prior to clay loading.

Iron modified /ZrO2 in application of removing trace olefins from aromatics

A solid super-acid catalyst /Fe2O3-ZrO2 (FeSZ) was prepared by coprecipitation method to remove olefins from aromatics. Effects of iron sources and Fe2O3 content were studied. FeSZ and /ZrO2 (SZ) were characterized by XRD, FT-IR and NH3-TPD. The characterization of the catalysts revealed that the addition of iron purified the tetragonal phase of ZrO2, increased the strength of the acid sites. Catalytic activity test showed that FeSZ with 5 wt% Fe2O3, using Fe2 (SO4)3 as iron source, exhibited the highest activity for removal of olefins. Compared with SZ, the catalytic activity of FeSZ increased 6.1%.

The effects of ammonium sulfate and sulfamic acid on the surface acidity of sulfated zirconia

In this work, sulfated zirconia (SZ) was prepared by a solvent-free method, ammonium sulfate ((NH4)2SO4) and sulfamic acid (NH2SO3H) were as sulfur sources, respectively. The resulting catalysts were characterized by powder X-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), N2 adsorption–desorption isotherms, inductively coupled plasma (ICP) and pyridine-FTIR. The characterization of the catalysts revealed that SZ prepared with (NH4)2SO4 as sulfur source contained more Lewis acid sites and less Brønsted acid sites. The effects of sulfur sources on the catalytic activity of catalysts were studied. Catalytic testing showed that SZ prepared with (NH4)2SO4 as sulfur source had a better catalytic performance for removing trace olefins from aromatics.

Mesoporous Zirconium Phosphonate Hybrid Bentonite as a Novel Efficient Catalyst for the Removal of Trace Olefins from Aromatics

A nove l mesoporous zirconium phosphonate hybrid bentonite (MZrPHB ) catalyst was prepared for the removal of trace olefins from refining aromat ic oil. Pyridine-FTIR, NH3‒TPD, XRD, and N2 adsorptiondesorption analysis were applied to characterize acidic properties and textural properties of catalysts. And its olefins removal performance of MZrPHB catalyst was evaluated in comparison with commercial clay catalyst. It is found that the MZrPHB catalyst possesses an abundance of weak Lewis acid centers, large surface area, and regular mesopore, and thus, exhibits a longer treat life and higher olefins conversion compared to commercial clay catalyst. MZrPHB prepared in this report can be considered as a promising and superior alternative material to commercial clays for the purification of aromatics.