Acidity Of Catalysts Research Articles

Selective toluene methylation to p-xylene: current status & future perspective

ABSTRACT Industrially, petroleum naphtha reforming and steam cracking are two major multistep and energy-intensive sources for p-xylene production. Additionally, p-xylene is also produced by selective toluene disproportionation, heavy (C9) aromatics trans-alkylation and isomerization of xylenes. Rapidly changing market dynamics from fuels to petrochemicals coupled with growing petrochemicals demand has led to the further exploration of economical and highly p-xylene selective processes by using surplus low-value aromatics. Methylation of toluene with methanol has been envisaged as one such potential opportunity to produce p-xylene. For the purpose, significant efforts have been made in the past forty years to develop suitable shape selective zeolite catalysts and technologies to make toluene methylation a highly p-xylene selective process. Current paper briefly highlights various advancements in the toluene methylation process development and aims to provide an extensive review of several works put up in the past to design suitable catalysts, catalyst’s limitations and developmental challenges for toluene methylation. Further, this paper provides an useful insight for two competing chemistries of toluene alkylation and side-by-side methanol reactions. Finally, motivated by competitive chemistry of methanol conversion reactions, existing catalytic limitations and novel synthesis opportunities in engineering shape selective zeolite catalysis, a way forward is proposed to arrive at a logical and futuristic catalyst design strategy for p-xylene production via toluene methylation. The proposed strategy is envisaged to offer low-to-moderate catalyst acidity, improved toluene methylation activity, high p-xylene selectivity and improved catalyst life which, otherwise, up till now have been the bottlenecks to develop distinctly economical toluene alkylation to p-xylene process.

Facile synthesis of Ni/Fe3O4 derived from layered double hydroxides with high performance in the selective hydrogenation of benzaldehyde and furfural

Efficient upgrading of biomass-derived platform chemicals plays a crucial role in the sustainable synthesis of fine chemicals. Herein, the noble-metal free and robust Ni/Fe3O4 catalysts originated from NiFe-layered double hydroxides (LDHs) was efficient for the selective upgrading of benzaldehyde (BzH) and furfural (Fur), accordingly, the highest yield of fine chemical benzyl alcohol (99.0%, BAL) and biofuel 2-methylfuran (78.4%, 2-MF) were obtained under mild conditions over the Ni/Fe ratio of 1, respectively. These performance is far superior to most of preciously reported candidates and their counterpartners. Systematic characterizations further revealed that Ni2+/Fe3+ ratio was closely related to the dispersion and the surface acidity of catalysts, which played crucial roles in achieving excellent catalytic performance. Besides, the solvent effect, reaction parameters and reusability of catalysts in the hydrogenation process of benzaldehyde were then studied as example. Finally, the reaction pathways of benzaldehyde and furfural hydrogenation were rationally proposed. This work provides a promising way to upgrade biomass-derived chemicals.

Al2O3 and phosphorus effect on the active phase and catalytic performance of Ni–Mo catalysts prepared by coprecipitation in hydrodesulfurization of benzothiophene

With the Mo, Ni acting as active constituents and Al2O3, phosphorus acting as additive, Ni-Mo-P-Al unsupported catalyst is synthesized by coprecipitation route. This catalyst is applied in the fluid-bed desulfurization process, with fluid catalytic cracking(FCC) diesel oil serving as the model sulfur compound. The catalysts are characterized by X-ray diffraction (XRD), specific surface area (BET), N2 adsorption and desorption, temperature-programmed desorption of ammonia (NH3-TPD), transmission electron microscopy (TEM), infrared Spectrum (FT-IR), H2 temperature-programmed reduction(H2-TPR), Laser Raman spectroscopy(LRS) and Gas chromatography(GC-PFPD) techniques. It shows that the introduction of Al2O3 contributes a higher surface area and pore volume to the catalysts. With phosphorus addition, the amount of tetrahedral Mo species decreased, and the number of octahedral Mo species increased. The catalyst acidity is changed from strong to weak, and more dispersed MoS2 particles formed with the formation of the Ni–Mo–S phase. At 280 °C, a hydrogen pressure of 4 MPa, an liquid hourly space velocity(LHSV) of 2.0 h−1 and a hydrogen-to-oil ratio of 500, the desulfurization rate reaches 99.8% and the sulfur concentrations decrease from 3950 μg/g to 7.9 μg/g.

Production of aromatics fuel additives from catalytic pyrolysis of cow manure over HZSM-5, HBeta, and HY zeolites

Catalytic pyrolysis of cow manure (CM) over HZSM-5, HBeta, and HY zeolites was conducted for the first time to produce valuable biofuels such as benzene, toluene, ethylbenzene, xylene, and naphthalene (BTEXN). HZSM-5 revealed the highest BTEXN production efficiency, followed by HBeta and HY, due to high acidity and proper pore structure of the catalysts. Greatly increased production of BTEXN (Peak area; 203.7 × 107 counts) was achieved by applying HZSM-5 to the catalytic pyrolysis of CM accompanied by a decrease in oxygen-containing compounds (O-CCs) due to effective deoxygenation and aromatization. Increasing the acidity of HZSM-5 by decreasing the SiO2/Al2O3 ratio (SAR) from 280 to 30 also increased BTEXN production efficiency with a proportional decrease in O-CCs, suggesting the importance of catalyst acidity. Increasing the reaction temperature from 550 ℃ to 600 ℃ and increasing the catalyst-to-feedstock (C/F) ratio from 1:1 to 5:1 also increased production of BTEXN and further decreased O-CCs. Between in-situ and ex-situ catalytic pyrolysis, in-situ reaction was more effective for aromatics formation.

Preparation of Beta-KIT-5 composite material supported ternary metal catalyst and its hydrodenitrogenation performance of quinoline

A series of Beta-KIT-5 (BK-x) composite materials with different Si/Al ratios were synthesized successfully with the nano-assembly method, and NiMoW catalysts were prepared for quinoline hydrodenitrogenation (HDN) reaction. The characterization results showed that BK composite materials possessed the ordered three-dimensional face-centered-cubic mesoporous structure and Beta topological structure; moreover the Beta structure units were embedded into the framework of KIT-5 material. The addition of Beta seed solution modified the textural properties and interaction between the support and active metals, thus improving the distribution of active metal species and enhancing the acidity of NiMoW catalysts, especially for Brønsted acid sites. The catalytic performance displayed that the NiMoW/BK-3 catalyst exhibited the highest HDN efficiency and maximum kHDN (21.6×10−5 mol g−1h−1), which was attributed to the excellent structural properties, moderate acid sites and suitable dispersion of Mo(W)S2 stacking slabs.

Preparation of Activated Carbon-Based Solid Sulfonic Acid and Its Catalytic Performance in Biodiesel Preparation.

With activated carbon as raw material, AC-Ph-SO3H was prepared after oxidation with nitric acid, modification with halogenated benzene and sulfonation with concentrated sulfuric acid. After modified by 10% bromobenzene with toluene as a solvent for 5 h, followed sulfonation with concentrated sulfuric acid at 150°C, the -SO3H content of prepared AC-Ph-SO3H was 0.64 mmol/g. Acid content test, infrared spectroscopy and Raman spectroscopy detection proved that the surface of AC-Ph-SO3H was successfully grafted with -SO3H group. When used as a catalyst for the methylation of palmitate acid, the catalytic performance of AC-Ph-SO3H was explored. When the reaction time was 6 h, the amount of catalyst acid accounted for 2.5 wt% of palmitic acid, and the molar ratio of methanol/palmitic acid was 40, the esterification rate of palmitic acid was 95.2% and the yield of methyl palmitate was 94.2%, which was much better than those of its precursors AC, AC-O, and AC-Ph (both about 4.5%). AC-Ph-SO3H exhibited certain stability in the esterification reaction system and the conversion rate of palmitic acid was still above 80% after three reuses.

Carbon-templated meso-design of nanostructured CeAPSO-34 for biodiesel production from free fatty acid and waste oil

The SAPO-34 zeotype with suitable physicochemical properties, was used to produce biodiesel as a clean fuel. The micropore nature of this catalyst limits the reaction because elainic acid molecules are too large to penetrate and access the internal pores of zeotype. The physicochemical properties of the synthesized catalysts were evaluated and compared using BET, XRD, TPD, EDX, FESEM, and HRTEM analyses. The simultaneous use of a carbon template and a heteroatom for doping in the synthesis of the catalyst (MCeAPSO-34) has a synergistic effect on increasing the pore diameter up to 4.1 nm. As expected, the MCeAPSO-34 zeotype gained 17, 12, and 27% more conversion rates than the CeAPSO-34 (doping effect), MSAPO-34 (carbon-template effect), and conventional SAPO-34 zeotypes in the production of biodiesel from elainic acid, respectively. Accommodation of CeO2 on the nanostructured MCeAPSO-34 zeotype by the solvothermal method increased the zeotype acidic sites from 73% to 89%. The use of ultrasound energy for distribution of the active phase increased the catalyst acidity and the conversion of 95% was obtained for the Ce/MCeAPSO-34 (U) catalyst. This catalyst has also converted 93% of the synthetic waste oil into biodiesel as a clean fuel.

Metal/acid bifunctional catalysts for the reductive catalytic fractionation of lignocellulose into phenols and holocellulose

Mongolian oak (MO), a lignocellulosic biomass feedstock comprising lignin, hemicellulose, and cellulose, was fractionated via reductive catalytic fractionation (RCF) into holocellulose-rich solid residue and lignin-derived phenol-rich liquid oil. To achieve an economically feasible RCF process, tungstate-zirconia (WZr)-supported metal catalysts, exhibiting bifunctionalities of hydrogen-adsorbing metal and acidic WZr, were used for depolymerizing and valorizing lignocellulose, and their catalytic activity was found to be highly dependent on the deposited metal. Ru/WZr exhibited excellent fractioning ability, achieving a maximum yield of 23.6 wt% of monomeric and dimeric compounds from MO and exhibiting the potential to be techno-economically viable. The superior activity of Ru/WZr can be attributed to the synergistic effects of metal and acid, which were studied by investigating the product distributions of aromatic small molecules depending on the properties of WZr-supported metal catalysts. The stabilization of reactive radical intermediates depending on the surface Brønsted acidity of acid catalysts and hydrogen-adsorbing ability of metals were also investigated. RCF reaction conditions were optimized for the maximum yield of monomeric compounds, which can be beneficial for the further development of industrial processes.

A highly effective approach to enhance the performance of biomass-derived acid for fructose conversion to 5-hydroxymethylfurfural

Synthesis of 5-hydroxymethylfurfural (HMF) from carbohydrate is one of vital step for bio-refinery development. In this work, a novel strategy was developed for catalytic conversion of fructose to HMF in 2-butanol. The inexpensive ionic liquids were used to adjust the acidity of biobased acid catalyst for enhancing the dehydration of fructose to HMF. The combination of 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) with oxalic acid afforded an excellent HMF yield of 97.1% at 98.7% fructose conversion under mild conditions of 100 °C and 60 min, owing to the enhanced dissociation ability of oxalic acid by [Bmim]Cl. A possible dissociation mechanism of oxalic acid induced by [Bmim]Cl was proposed based on control experiments and detailed analyses with NMR and FT-IR techniques. It involved that the [Bmim]Cl interacted with oxalic acid through hydrogen bond, which decreased the electron density of oxygen atom on hydroxyl group and weakened the O-H bond, thus making the hydrogen in the O-H group to easily dissociate in the form of H+. Moreover, the reusability of oxalic acid and [Bmim]Cl was demonstrated, and both could be reused up to six times without significant loss in activity

Gasoline and diesel-like fuel production via hydrocracking of hydrotreated tire pyrolytic oil over Ni-W/MCM-41 derived from blast furnace slag

This work reports the conversion of tire pyrolytic oil (TPO) to fuels via hydrotreatment followed by hydrocracking (HC) processes over Ni–W/MCM-41 and Ni–W/Al-MCM-41 catalysts. The catalysts were hydrothermally synthesized using the blast furnace slag (BFS) derived silica followed by precipitation of metals oxide. The catalysts physiochemical properties were investigated via several analysis tools. The TEM results revealed the ordered mesoporous MCM-41 formation and the metal oxide particles distribution on its surface. The XPS and TPR analyses confirmed the metals oxide existence on the MCM-41 support surface while incorporation into the support was observed for Ni–W/Al-MCM-41 catalyst. The Ni–W/Al-MCM-41 catalyst possessed the higher HC activity and 97.7% hydrodesulfurization. The high activity was explained via the surface area, pore size and catalyst acidity. Both catalysts have successfully produced gasoline and diesel-like fractions corresponding to the EN228 and EN590 specifications. The hydrocracked oil produced a 35 wt% of gasoline and 33% diesel upon fractionation.

Effect of acidic components (SO42- and WO3) on the surface acidity, redox ability and NH3-SCR activity of new CeO2-TiO2 nanoporous aerogel catalysts: A comparative study

• New CeTiSO 4 2- and WO 3 -CeTi nanoporous aerogel catalysts for NH 3 -SCR reaction. • SO 4 2- modifies the nature of Ce species and increases the acidity of the CeTi aerogel. • WO 3 generates more reactive surface oxygen and active redox sites at CeTi surface. • WO 3 -CeTi displays the highest SCR activity at 320–400 °C (NO conversion > 90 %) • CeTiSO 4 2- exhibits superior SCR performance at 450–500 °C (NO conversion > 90 %) Selective catalytic reduction (SCR) of nitrogen oxide (NO) by ammonia (NH 3 ) was studied in this work over new sulfate (SO 4 2- ) or tungsta (WO 3 ) modified CeO 2 -TiO 2 aerogel catalysts. The catalytic systems were elaborated via sol gel method then characterized by: XRD, N 2 -Physisorption at 77 K, DRUV–vis, NH 3 -TPD and H 2 -TPR. It was revealed that the nature of acidic components influences differently the texture, surface oxygen concentration, acidity, reducibility and NH 3 -SCR activity of new Ce-based catalysts. Hence, the incorporation of sulfate modifies the nature of Ce species, improves their dispersion through the Ce-SO 4 2- interactions and, particularly, generates new strong acid sites which display superior catalytic performance at high temperature NO reduction (NO conversion into N 2 > 90 % between 450 and 500 °C over CeO 2 -TiO 2 -SO 4 2- catalyst). However, the addition of tungsta affects slightly the surface acidity of CeO 2 -TiO 2 catalyst but it induces the creation of more reactive surface oxygen and new redox sites at its surface (mainly due to the existence of W-Ce interactions) leading to highly active WO 3 -CeO 2 -TiO 2 system for the low temperature NH 3 -SCR reaction with above 90 % NO conversion into N 2 between 320 and 400 °C.

Impacts of catalyst, inorganic and organic corrodants on corrosion under batch-mode catalytic biomass hydrothermal liquefaction conversion

Catalytic hydrothermal liquefaction (CHTL) is used to convert wet biomass for highly promising carbon conversion efficiency. This study investigated three major environmental factors, including catalyst, inorganic corrodants and organic acid on the corrosion of two candidate reactor steels (SS310 and P91) using autoclave methodology and advanced characterization techniques. The addition of 0.5 M K2CO3 resulted in a remarkable increase in corrosion rates and significantly changed the corrosion layers formed. The acetic acid generated from CHTL also noticeably enhanced corrosion while the presence of Cl- and S2- only had marginable influence. SS310 exhibited much better performance than P91 under the CHTL conditions.

Effect of Different Metal Modified Dolomite Catalysts on Catalytic Glycerol Hydrogenolysis towards 1,2-Propanediol

A series of metal modified dolomite catalysts (10%Ni-20%Cu/Dol, 10%Co-20%Cu/Dol, 10%Fe-20%Cu/Dol, 10%Zn-20%Cu/DolNi) were synthesized via method of impregnation, later calcined at 500 ℃ and reduced by 5%H2 at 600 ℃. Those catalysts were formerly tested for their physico-chemical properties by BET, BJH, XRD, H2-TPR, NH3–TPD, CO2-TPD and SEM, and followed by evaluation in catalytic performance of glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO). Among the examined catalysts, 10%Ni-20%Cu/Dol showed optimum hydrogenolysis activity owing to the good copper-nickel-dolomite interaction. The outcomes from the characterizations disclosed that the presence of nickel-copper species which principally enriched on dolomite surface thereby enhanced the properties of the catalyst in terms of good metal reducibility along with the presence of adequate catalyst acidity. All the good features of 10%Ni-20%Cu/Dolcatalyst added to its high activity with 83.5% glycerol conversion (GC) and 75% 1,2-PDO with low methanol as side reaction product under 200 ℃, 4 MPa H2 and 10 h duration test, 1 g catalyst dosage and 20 wt% glycerol concentration.

Upgradation of sugarcane bagasse lignin: Fractionation to cyclic alcohols production

Reductive catalytic fractionation (RCF) is a new class of process that produces mono phenolics close-to-theoretical maximum yield by preserving the biomass polysaccharides as solid residues under hydrogen atmosphere or hydrogen transfer conditions. Herein, hydrous ruthenium oxide deposited on carbon (HRO@C) and HY-zeolite (HRO@HYZ) catalysts are prepared and characterized by different analytical techniques (TGA, TPD, TPR, XRD, TEM, XPS, physisorption and chemisorption). Both catalysts have been used for the RCF of sugarcane bagasse (SCB). Effects of catalyst acidity, reaction time, pressure, temperature, and solvent on the RCF of SCB have been investigated. Solid residues after RCF are characterized by FT-IR, TGA, XRD, and fibertec to identify the effects of reaction conditions on lignin-first delignification efficiency (LFDE). High acidity of HRO@HYZ favors a high degree of LFDE (81.2 %) than HRO@C (55.8 %). However, alkyl-substituted phenolic monomers (ASPMs) selectivity is 69 % for HRO@C and 55.7 % for HRO@HYZ, respectively, under the same reaction conditions. NMR and GC-FID/GC-MS analysis indicate the presence of ASPMs in the resulted lignin bio-oil. Moreover, fractionated lignin bio-oil is used for upgradation and the upgraded product analysis confirms > 95 % conversion of lignin bio-oil, in which over 90 % selectivity is towards alkylated cyclic alcohols.

Study on activity and stability of Pt-Ru/WOx/Al2O3 catalyst in the glycerol selective hydrogenolysis to 1,3-propanediol

The deactivation of Pt/WOx/Al2O3 and Pt-Ru/WOx/Al2O3 catalysts in the glycerol hydrogenolysis to 1,3-propanediol (1,3-PDO) was investigated in autoclave. The selectivity of both catalysts toward 1,3-PDO was within 50–56% after the first five usages at 170 °C for 12 h with a H2 pressure of 9 MPa. With Pt/WOx/Al2O3, the conversion of glycerol decreased from 44.3% (1st reaction) to 27.2% (5th reaction), whereas a conversion of 52.4%, 48.0%, and 48.4% was obtained in the 1st, 5th, and 20th reactions, respectively, when Pt-Ru/WOx/Al2O3 was used. The characterizations of the catalysts showed that the pore structure of the catalyst changed because of the crystal structure of the catalyst support changing from γ-Al2O3 to pseudo-boehmite. However, the changes of the catalyst morphology were not responsible for the catalyst deactivation. Simultaneously, the acidity of catalysts was not shown to be a factor in their deactivation. On the other side, catalysts were not deactivated as a result of the loss of active components. Catalyst deactivation during glycerol hydrogenolysis was finally caused by the aggregation of active metal particles (Pt or Pt-Ru).

New insight on N2O formation over MnOx/TiO2 catalysts for selective catalytic reduction of NOx with NH3

High N2O selectivity of MnOx-TiO2 catalyst hinders its development in ammonia selective catalytic reduction (NH3-SCR) of NOx. Herein, a series of MnOx-TiO2 catalyst with different Mn/Ti ratio were prepared by wet-impregnation method to study the N2O formation during ammonia selective catalytic reduction (NH3-SCR) of NOx from the perspective of catalyst. It is found that MnOx and TiO2 species are the mainly redox and acid sites for the NH3-SCR denitration reaction over MnOx-TiO2 catalyst, respectively. As the Mn/Ti ratio increases, MnOx species layer expanded on TiO2 support, leading to increase of redox sites but decrease of surface acid sites. These changes contribute to the occurrence of the no-selective oxidation of NH3 on MnOx species and the over-activation of NH3 at Mn-Ti interface, resulting in the formation of N2O via the route of 2NH3 + 2O2 → N2O + 3H2O and 4NO + 4NH3 + 3O2 → 4N2O + 6H2O, respectively. Through this work, it can be speculated that both improving MnOx dispersion and increasing surface acidity of catalyst are feasible strategy for suppressing the N2O formation on MnOx-TiO2.

Highly Efficient One-Step Conversion of Fructose to Biofuel 5-Ethoxymethylfurfural Using a UIO-66-SO3H Catalyst.

In this study, a novel sulfonic acid-modified catalyst for MOFs (UIO-66-SO3H) was synthesized using chlorosulfonic acid as a sulfonating reagent and first used as efficient heterogeneous catalysts for the one-pot conversion of fructose into biofuel 5-ethoxymethylfurfural (EMF) in a cosolvent free system. The physicochemical properties of this catalyst were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and powder X-ray diffraction (XRD). The characterization demonstrated that the sulfonic acid group was successfully grafted onto the MOF material and did not cause significant changes to its morphology and structure. Furthermore, the effects of catalyst acid amount, reaction temperature, reaction time, and catalyst dosage on reaction results were investigated. The results showed that the conversion of fructose was 99.7% within 1 h at 140°C, while the EMF yield reached 80.4%. This work provides a viable strategy by application of sulfonic acid-based MOFs for the efficient synthesis of potential liquid fuel EMF from renewable biomass.

ALGLIQOL: A two stage integrated process towards synthesis of renewable transportation fuel via catalytic hydrothermal liquefaction of lipid enriched microalgae biomass and distillation

Present study demonstrates a two-stage integrated process for production of hydrocarbon oil designated as ALGLIQOL, with potential to be utilized as liquid transportation fuel. Stage-I involves in-situ catalytic hydrothermal liquefaction (HTL) of microalgae biomass to produce biocrude oil and stage-II involves distillation of biocrude to hydrocarbon oil. A strategic attempt has been implemented to develop stage-I, where improvement not only in the biocrude oil yield but also in its quality was achieved in three sequential steps. Step 1: statistical optimization of HTL process parameters i.e. retention time, biomass loading, and temperature; step 2: in-situ catalytic HTL under optimized process parameters, exploiting combinatorial effect of homogenous and heterogenous catalyst, Pd/Al2O3 and formic acid, respectively and step 3: catalytic HTL using lipid enriched biomass as feedstock. The maximum biocrude oil yield was 28.67 wt%, at optimal temperature 300.9 °C, retention time 71 min, biomass loading 8.86% w/v, Pd/Al2O3 loading 10 % w/w, formic acid loading 7.73% w/v and intracellular lipid percentage 20% w/w. The improvement in quality of biocrude oil was marked with improved hydrocarbon fraction and concomitant reduction in oxygenates and nitrogenates fractions. Systematically improved physical parameters of biocrude oil such as kinematic viscosity, density and TAN, were found to be comparable with the ASTM and EN specifications of the diesel fuel and biodiesel. Calorific value of the final product ALGLIQOL was estimated to be 41 MJ kg−1 with density 822 kg m−3, kinematic viscosity 1.61cSt and TAN 0.663 mg KOH g−1. GC–MS analysis of ALGLIQOL indicates a hydrocarbon fraction of 81.25%, with abundance of aromatics, alkene and alkane. Significant similarity in physiochemical properties of ALGLIQOL and gasoline or diesel fuel, indicates its suitability as transportation fuel.

Degradation of the mixed nuclear-grade cationic and anionic exchange resins using Fe2+/H+ homogeneous Fenton oxidation

To further improve the treatment capacity of actual wastes, H+ was introduced into the homogeneous Fenton system as a co-catalyst for dissolution and degradation of the mixed nuclear-grade cationic and anionic exchange resins. The effects of acid type and concentration, catalyst type and concentration, H2O2 dosage, initial temperature, antifoaming agent and resin ratio were studied. The concentration of inorganic acid, type and concentration of catalyst had significant influence on the decomposition of mixed resins. The experimental results showed that when the mixing ratio of resins was 1:1, the initial temperature was 96 ± 1 °C, the amount of H2O2 was 200 mL, and the concentration of H+/Fe2+ was 1 M/0.1 M, complete dissolution and 79% weight reduction of mixed resins were obtained. Combined with density functional theory (DFT) calculations, cationic exchange resin and anionic exchange resin showed different reactivity in the experiment. Hydroxyl radicals (•OH) tended to attack –SO3- groups with more negative charges, and the barrier energy of –SO3- ion dissociation was 8.2 kcal/mol, which caused the cationic exchange resin to be easily destroyed. According to the characterization results, the characteristic intermediates were determined, indicating that desulfonation, valence change of nitrogen atom, and cleavage of long-chain carbon skeleton existed during the reaction, but incomplete oxidation still remained.

Kinetics of Catalytic Decarboxylation of Naphthenic Acids over HZSM-5 Zeolite Catalyst

Naphthenic acids are naturally occurring carboxylic acids in crude oil with cyclic or aromatic rings in their structure. These carboxylic acids are responsible for the acidity of crude oil, leading to corrosion problems in refinery equipment and the deactivation of catalysts while creating a continuous need for maintenance. Therefore, removing naphthenic acids has become an important requirement in refining acidic crude oil. In this paper, experiments are conducted to investigate the use of HZSM-5 zeolite catalyst to reduce the total acid number (TAN) of a typical acidic crude oil obtained from Al-Fula blocks in Western Sudan. TAN is an important metric signifying the acidity of crude oil. A full factorial design of the experiment (DOE) framework enabled a better understanding of the efficacy of the catalyst at three parametric levels (reaction temperature: 250-270-300 °C, reaction time: 2-3-4 h, and oil:catalyst weight ratio: 20-22-25 g/g). The results demonstrate that the HZSM-5 zeolite catalyst provides up to 99% removal of naphthenic acids via the decarboxylation route. Additionally, the removal efficiency increases with increasing temperature and residence time. The acidity of the crude oil was shown to decrease after treatment with the catalyst for four hrs.; from 6.5 mg KOH/g crude to 1.24; 0.39 and 0.17 mg KOH/g at 250; 270 and 300 °C, respectively. A sharp decrease of TAN was observed at the oil catalyst mass ratio of 20 g/g at 250 °C, and almost complete conversion of acids was achieved after 4 hrs. Another experiment at 270 °C showed a converse relationship between the oil:catalyst ratio and acid removal; suggesting the activation of side reactions at higher temperature conditions catalyzed by excess acid. Finally; a Langmuir–Hinshelwood (LH) kinetic model has been developed to enable rapid prediction of the performance of the HZSM-5 zeolite catalyst for decarboxylation reaction. The model has also been validated and tested in ASPEN® software for future simulation and scalability studies.