Waste cooking oil processing over cobalt aluminate nanoparticles for liquid biofuel hydrocarbons production

The catalytic conversion of waste cooking oil (WCO) was carried out over a synthetic nano catalyst of cobalt aluminate (CoAl₂O₄) to produce biofuel range fractions. A precipitation method was used to create a nanoparticle catalyst, which was then examined using field-emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray, nitrogen adsorption measurements, high-resolution transmission electron Microscopy (HRTEM), infrared spectroscopy, while a gas chromatography-mass spectrometer (GC-MS) was used to analyze the chemical construction of the liquid biofuel. A range of experimental temperatures was looked at including 350, 375, 400, 425, and 450 °C; hydrogen pressure of 50, 2.5, and 5.0 MPa; and liquid hour space velocity (LHSV) of 1, 2.5, and 5 h^-1. As temperature, pressure, and liquid hourly space velocity increased, the amount of bio-jet and biodiesel fractional products decreased, while liquid light fraction hydrocarbons increased. 93% optimum conversion of waste cooking oil over CoAl₂O₄ nano-particles was achieved at 400 °C, 50 bar, and 1 h^-1 (LHSV) as 20% yield of bio-jet range,16% gasoline, and 53% biodiesel. According to the product analysis, catalytic hydrocracking of WCO resulted in fuels with chemical and physical characteristics that were on par with those required for fuels derived from petroleum. The study's findings demonstrated the nano cobalt aluminate catalyst's high performance in a catalytic cracking process, which resulted in a WCO to biofuel conversion ratio that was greater than 90%. In this study, we looked at cobalt aluminate nanoparticles as a less complex and expensive alternative to traditional zeolite catalysts for the catalytic cracking process used to produce biofuel and thus can be manufactured locally, which saves the cost of imports for us as a developing country.

CuAPO-5 as a Multiphase Catalyst for Synthesis of Verbenone from α-Pinene

Copper(II)-containing aluminum phosphate material (CuAPO-5) was synthesized hydrothermally and used as a multiphase catalyst for the oxidation of α-pinene to verbenone. The catalysts were analyzed using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area techniques, X-ray photoelectron spectroscopy (XPS), and ammonia temperature programmed reduction (NH₃-TPD). Scanning electron microscopy (SEM), X-ray energy spectrometry (EDS), inductively coupled plasma emission spectroscopy (ICP-OES), Fourier infrared spectroscopy (FT-IR), and ultraviolet-visible spectroscopy (UV-vis) were performed to characterize the material. The effects of reaction temperature, reaction time, n(α-pinene)/n(TBHP), and solvent on the catalytic performance of CuAPO-5 were investigated. The results show that all the prepared catalysts have AFI topology and a large specific surface area. Copper is evenly distributed in the skeleton in a bivalent form. The introduction of copper increases the acid content of the catalyst. Under the optimized reaction conditions, 96.8% conversion of α-pinene and 46.4% selectivity to verbenone were achieved by CuAPO-5(0.06) molecular sieve within a reaction time of 12 h. CuAPO-5(0.06) can be recycled for five cycles without losing the conversion of α-pinene and the selectivity to verbenone.

Direct synthesis of shaped MgAPO-11 molecular sieves and the catalytic performance in n-dodecane hydroisomerization

In industrial application, molecular sieves are usually used in a certain shape. This requires the addition of binder and causes the reduction of both the molecular sieve content and catalytic performance. Herein, pseudo-boemite was mixed with deionized water at room temperature, followed by the drop-wise addition of phosphoric acid, magnesium acetate solution, hydrofluoric acid, di-n-propylamine and 1-ethyl-3-methyl imidazolium bromide with vigorous stirring. The molar ratio of Al₂O₃ : P₂O₅ : MgO : HF : DPA : [EMIm]Br : H₂O in the gel was 1 : 1 : 0.03 : 0.18 : 0.4 : 1 : 45. Then the gel was dried, extruded and directly crystallized to form a shaped MgAPO-11 molecular sieve. X-ray diffraction, scanning electron microscopy, N₂ adsorption, ammonia temperature programmed desorption, pyridine adsorption infrared spectroscopy and nuclear magnetic resonance spectroscopy were used to investigate the physicochemical properties of the samples. X-ray diffraction, scanning electron microscopy and N₂ adsorption tests show that the shaped MgAPO-11 molecular sieve is fully crystallized and possesses hierarchical porosity. Mg is incorporated into the molecular sieve framework and the Pt catalyst supported by the obtained shaped MgAPO-11 exhibits excellent catalytic performance with n-dodecane conversion of 94% and isomer selectivity of 95% at 280 °C. Such a method for the direct synthesis of shaped molecular sieves shows potential for the green synthesis of molecular sieves in industry.

Shaped MgAPO-11 with hierarchical pores can be directly synthesized via a solid transformation route. Fewer synthesis steps and superior catalytic performance make the route possess great potential in practical applications.

Physicochemical characterization to assess Ni and Zn incorporation into zeotype SAPO-34 nanoparticles synthesized with different mixing methods through ultrasound-promoted crystallization

The effect of synthesis parameters on the properties of Ni- and Zn-containing SAPO-34 nanoparticles prepared by applying insonation was investigated to elucidate how the isomorphous substitution of metal ions was influenced by synthesis conditions.

Synthesis of highly stable metal-containing extra-large-pore molecular sieves

The isomorphic substitution of two different metals (Mg and Co) within the framework of the ITQ-51 zeotype (IFO structure) using bulky aromatic proton sponges as organic structure-directing agents (OSDAs) has allowed the synthesis of different stable metal-containing extra-large-pore zeotypes with high pore accessibility and acidity. These metal-containing extra-large-pore zeolites, named MgITQ-51 and CoITQ-51, have been characterized by different techniques, such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, UV-Vis spectroscopy, temperature programmed desorption of ammonia and Fourier transform infrared spectroscopy, to study their physico-chemical properties. The characterization confirms the preferential insertion of Mg and Co atoms within the crystalline structure of the ITQ-51 zeotype, providing high Brønsted acidity, and allowing their use as efficient heterogeneous acid catalysts in industrially relevant reactions involving bulky organic molecules.

Ionothermal Synthesis of MnAPO-SOD Molecular Sieve without the Aid of Organic Structure-Directing Agents

An SOD-type metalloaluminophosphate molecular sieve (denoted as SOD-Mn) was ionothermally synthesized by introducing manganese(II) cations into the reaction mixture via MnO-acid or MnO2-reductant reactions. Composition and structure analyses results show that two kinds of manganese(II) cations exist in the SOD-Mn structure. Part of the manganese(II) cations isomorphously substitute the framework aluminum(III) with a substitution degree of ∼30%. The rest of the manganese(II) cations occupy a fraction of the sod cages in their hydrated forms. A comprehensive investigation of the synthesis parameters, crystal sizes, and crystallization kinetics indicates that the in situ released hydrated manganese(II) cations direct the formation of SOD-Mn. Such structure-directing effect may be inhibited by both the fluorination of manganese(II) cations and the water accumulation during crystallization. In the fluoride anion-containing reaction mixture with a low ionic liquid content, the crystallization process is strongly suppressed, and large SOD-Mn single crystals of over 200 μm in size are yielded. SOD-Mn is free from organics and shows improved thermal stability compared with metalloaluminophosphates synthesized by using organic structure-directing agents.

Enhancement of catalytic properties and lifetime of nanostructured SAPO-34 by La isomorphous substitution and alteration of Si/Al ratio used in methanol conversion to light olefins

Methanol conversion to light olefins was investigated over SAPO-34 catalysts with La introduction exploring the effect of different Si/Al ratios.

Multipore zeolites: synthesis and catalytic applications

In the last few years, important efforts have been made to synthesize so-called "multipore" zeolites, which contain channels of different dimensions within the same crystalline structure. This is a very attractive subject, since the presence of pores of different sizes would favor the preferential diffusion of reactants and products through those different channel systems, allowing unique catalytic activities for specific chemical processes. In this Review we describe the most attractive achievements in the rational synthesis of multipore zeolites, containing small to extra-large pores, and the improvements reported for relevant chemical processes when these multipore zeolites have been used as catalysts.

Identification of synergistic Cu/V redox pair in VCu:AlPO-5; a comparison with VCu:ZSM-5

Vanadium(V) and copper(II) were co-deposited into AlPO-5 and H-ZSM-5 three-dimensional microporous carriers to yield VCu:AlPO-5 and VCu:ZSM-5. The materials, along with copper analogues were tested for the selective oxidation of propene, and the catalysts perform in the following order: VCu:AlPO-5 > Cu:AlPO-5 > VCu:ZSM-5 > Cu:ZSM-5. Acrolein was selectively formed over VCu:AlPO-5 and Cu:AlPO-5 over a very wide range from 300 to 450 °C, whereas VCu:ZSM-5 displays a limited temperature window for acrolein formation (300-350 °C). Hence, the choice of carrier and presence of vanadium as a co-cation greatly affects the acrolein selectivity and activity window. The vanadium and copper reduction events were monitored by in situ X-ray Absorption Spectroscopy (XAS) during C3H6-TPR (1.11%) to 450 °C. The Cu(II)/(I) redox pair initiates reduction of V(V) → V(IV) in VCu:AlPO-5 and VCu:ZSM-5 at 375 °C. Metallic copper is the major valence fraction above 400 °C in both samples while vanadium is present as V(IV)/V(III) species. In the monometallic copper analogues Cu(I) is the major valence fraction above 350 °C, hence synergistic effects between the Cu/V pair causes hyper-reduction of copper. EXAFS shows that copper and vanadium are in close proximity in VCu:AlPO-5 only, being linked by bridging oxygens (Cu-O-V) believed to interact with propene. By contrast, propene adsorbs on Brønsted sites in VCu:ZSM-5 inhibiting acrolein formation at elevated temperatures, as confirmed by DRIFTS. We believe the reactive Cu/V pair in neutral AlPO-5 generates extralattice oxygens favouring acrolein formation over a wide temperature range.

The beneficial use of ultrasound in synthesis of nanostructured Ce-doped SAPO-34 used in methanol conversion to light olefins

Methanol to olefins process is an interesting route for synthesis of light olefins over nanostructured catalysts. The present research deals with catalyst development by sonochemical method for methanol to olefins reaction with the aim of reaching the most efficient catalyst. The CeSAPO-34 catalyst was prepared via ultrasound assisted hydrothermal method and characterized by XRD, FESEM, PSD, EDX, BET and FTIR techniques. The characteristics and performance of this sample were compared to the catalyst prepared by conventional hydrothermal method. XRD patterns reflected the higher crystallinity of the catalyst synthesized by ultrasound application. In comparison, particles with smaller sizes obtained by applying ultrasonic irradiation. The catalyst obtained using ultrasound had the longer lifetime and sustained desired light olefins at higher values.

Energy-resolved electron-yield XAS studies of nanoporous CoAlPO-18 and CoAlPO-34 catalysts

Energy-resolved electron-yield X-ray absorption spectroscopy is a promising technique for probing the near-surface structure of nanomaterials because of its ability to discriminate between the near-surface and bulk of materials. So far, the technique has only been used in model systems. Here, the local structural characterization of nanoporous cobalt-substituted aluminophosphates is reported and it is shown that the technique can be employed for the study of open-framework catalytically active systems. Evidence that the cobalt ions on the surface of the crystals react differently to those in the bulk is found.

Synthesis of an extra-large molecular sieve using proton sponges as organic structure-directing agents

The synthesis of crystalline microporous materials containing large pores is in high demand by industry, especially for the use of these materials as catalysts in chemical processes involving bulky molecules. An extra-large-pore silicoaluminophosphate with 16-ring openings, ITQ-51, has been synthesized by the use of bulky aromatic proton sponges as organic structure-directing agents. Proton sponges show exceptional properties for directing extra-large zeolites because of their unusually high basicity combined with their large size and rigidity. This extra-large-pore material is stable after calcination, being one of the very few examples of hydrothermally stable molecular sieves containing extra-large pores. The structure of ITQ-51 was solved from submicrometer-sized crystals using the rotation electron diffraction method. Finally, several hypothetical zeolites related to ITQ-51 have been proposed.

Progress in heteroatom-containing aluminophosphate molecular sieves

Over the past 30 years, heteroatom-containing aluminophosphate molecular sieves as a prime class of heterogeneous single-site solid catalysts have been quickly developed since the first discovery of aluminophosphate molecular sieves in 1982, and a large variety of such materials with 48 unique zeotype structures have been prepared. This work mainly presents the progress in the development of heteroatom-containing aluminophosphate molecular sieves with new zeolite structures and variable framework compositions in recent years.

Distance measurements between paramagnetic centers and a planar object by matrix Mims electron nuclear double resonance

Frequency-domain electron nuclear double resonance (ENDOR), two time-domain electron nuclear double resonance techniques, and electron spin echo envelope modulation spectroscopy are compared with respect to their merit in measurements of small hyperfine couplings to nuclei with intermediate gyromagnetic ratio such as 31P. The frequency-domain Mims ENDOR experiment is found to provide the most faithful line shapes. In the limit of long electron-nuclear distances of more than 0.5 nm, sensitivity of this experiment is optimized by matching the first interpulse delay to the transverse relaxation time of the electron spins. In the same limit, Mims ENDOR efficiency scales inversely with the sixth power of distance. Hyperfine splittings as small as 33 kHz can be detected, corresponding to an electron-31P distance of 1 nm. In systems, where a certain kind of nuclei is distributed in a plane, measurements of intermolecular hyperfine couplings can be analyzed in terms of a distance of closest approach of a paramagnetic center to that plane. By applying this technique to spin-labeled lipids in a fully hydrated lipid bilayer it is found that for a fraction of lipids, chain tilt angles can be 25 degrees larger than the mean tilt angle of the lipid chains. This model of all-trans hydrocarbon chains with a broad distribution of tilt angles is also consistent with orientation selection effects in high-field ENDOR spectra.

A reactivity index study to rationalize the effect of dopants on Brönsted and Lewis acidity occurring in MeAlPOs

The influence of both bivalent and trivalent metal substituents from a range of metal cation (Co, Mn, Mg, Fe and Cr) on the acidic property (both Brönsted and Lewis) of metal substituted aluminum phosphate MeAlPOs is monitored. The influence of the environment of the acid site is studied both by localized cluster and periodic calculations to propose that the acidity of AlPOs can be predictable with accuracy so that AlPO material with desired acidity can be designed. A semi-quantitative reactivity scale within the domain of hard soft acid-base (HSAB) principle is proposed in terms of the metal substitutions using density functional theory (DFT). It is observed that for the bivalent metal cations Lewis acidity linearly increases with ionic size, where as the Brönsted acidity is solely dependent on the nearest oxygen environment. Intramolecular and intermolecular interactions show that once active site of the interacting species is identified, the influence of the environment can be prescribed. Mg(II)-doped AlPO-34 shows highest Brönsted acidity and whereas Cr(III)-doped species shows lowest acidity. Fe(II)/Fe(III)-doped AlPO-34 shows highest Lewis acidity, whereas Mn(III), Mg (II) shows lowest acidity.

Synthesis and Characterization of Stabilized Subnanometric Cobalt Metal Particles

Subnanometric cobalt metallic particles, with an average size of 0.8 nm and an estimated number of 50 atoms, have been stabilized in the confined spaces within the nanopores of crystalline molecular sieves. Remarkably, these clusters show a rapid vanishing of the magnetization as the temperature is increased from 10 to 20 K because of the ferromagnetic-paramagnetic transition together with thermal fluctuations of the remaining moment. This dramatic reduction of the transition temperature is due to strong finite size effects. Such behavior, predicted for very small metallic particles, was never observed before due to the inherent difficulty in achieving subnanometric stable metallic particles.

31P NMR as a Tool for Studying Incorporation of Ni, Co, Fe, and Mn into Aluminophosphate Zeotypes

The incorporation of moderate amounts of Ni(II), Co(II), Fe(II/III), and Mn(II/III) into aluminophosphate zeotype AlPO4-34 and Fe(II/III) into aluminophosphate zeotype AlPO4-36 was studied by broadline 31P NMR. The technique provided direct evidence on isomorphous substitution of framework aluminum by transition metals and allowed us to determine the extent of the substitution. 31P NMR proved to be complementary to other spectroscopic techniques such as X-ray absorption spectroscopy (XAS), Mössbauer, electron paramagnetic resonance (EPR), and electron nuclear double resonance (ENDOR) spectroscopies. The position of the NMR signal belonging to phosphorus in the P(OAl)3(OMe) environment depended mostly on the magnitude of the hyperfine interaction between a phosphorus nucleus and an unpaired electron, which was delocalized from the transition metal atom Me by covalent bonding. The width of the NMR signal was dominated by dipolar coupling among phosphorus nuclei and nearest paramagnetic centers. In addition, broadline NMR of ethylenediamine-templated manganese phosphate (C2H10N2)[Mn2(HPO4)3(H2O)], which was used as a model compound, showed that on the basis of line positions and line widths different 31P signals could easily be assigned to different phosphorus crystallographic sites. The technique could thus be applied to extract valuable structural information about metal phosphates as well.