Hydrogen production via catalytic reforming of the bio-oil model compounds: Acetic acid,phenol and hydroxyacetone

Catalytic reforming of three typical bio-oil model compounds, phenol, acetic acid and hydroxyacetone, has been carried out over a Ni/nano-Al₂O₃ catalyst. Al₂O₃, in the form of nano-rods of length approximately 40 nm, was selected as the catalyst support. The catalyst showed superior performance in terms of activity and stability. The conversions for phenol, acetic acid and hydroxyacetone reached 84.2%, 98.2% and 98.7%, respectively, at the reaction temperature of 700 °C. The corresponding hydrogen yields were 69%, 87% and 97.2%. The catalyst maintained its high reactivity for more than 10 h in the catalytic reforming of three model compounds. The influences of steam to carbon ratio, catalyst loading and Ni content in the catalyst on the reforming performance were also investigated. In addition, the possible decomposition pathways for phenol, acetic acid and hydroxyacetone are proposed.     

Bio-oil catalytic reforming without steam addition: Application to hydrogen production and studies on its mechanism

A novel process for hydrogen production via bio-oil catalytic reforming without steam addition was proposed. The liquid feedstock was a distillation fraction from crude bio-oil molecular distillation. The fraction obtained was enriched with the low-molecular-weight organics (acids, aldehydes, and ketones), and contained nearly all of the water from crude bio-oil. The highest catalytic performance, with a carbon conversion of 95% and a H₂ yield of 135 mg g⁻¹ organics, was obtained by processing the distillate over Ni/Al₂O₃ catalyst at 700 °C. The steam involved in the reforming reaction was derived entirely from the water in the crude bio-oil. The fresh and spent catalysts were characterized by N₂-physisorption, thermogravimetric analysis, and high-resolution transmission electron microscopy. To further understand the reaction mechanisms, symmetric density functional theory calculations for decomposition were performed on four model compounds in bio-oil (acetic acid, hydroxyacetone, furfural, and phenol) over the Ni(111) surface. In addition, the decomposition of H₂O∗ to OH∗ and O∗ and their subsequent steam reforming reactions with carbon precursors (CH∗ and CH₃C∗) were also examined.     

Highly active Nd-promoted Ni@Al2O3 core-shell catalyst for steam reforming of acetic acid: Insights of the remarkable coke resistance

Aiming at enhancing the coke resistance of Ni-based catalysts, the Nd-doped Ni@A₂O₃ core-shell catalysts were prepared and their catalytic performance was evaluated in the steam reforming of acetic acid (SRAA). The catalysts were characterized by BET, XRD, XRF, HRTEM, H₂-TPR, NH₃-TPD, and DTG. The catalytic performance was greatly enhanced by the incorporation of Nd, with decreased yields of CO, CH₄, and acetone, increased yield of CO₂, and remarkable carbon resistance. The decoking behavior of the spent catalyst was elucidated by H₂O¹⁸-TSD. A low reaction temperature facilitates the formation of amorphous carbon, leading to catalyst deactivation. The decoking ability of the catalyst is greatly improved by the Nd incorporation but is also catalyzed by the exposed Ni surface. The Ni0.01Nd@Al catalyst greatly balanced the exposed Ni surface and the mobile lattice oxygen, showing the highest catalytic activity, lowest coke deposition, and superb decoking ability.     

Ni/Ru–Mn/Al2O3 catalysts for steam reforming of toluene as model biomass tar

The catalytic steam reforming of the major biomass tar component, toluene, was studied over two commercial Ni-based catalysts and two prepared Ru–Mn-promoted Ni-base catalysts, in the temperatures range 673–1073 K. Generally, the conversion of toluene and the H₂ content in the product gas increased with temperature. A H₂-rich gas was generated by the steam reforming of toluene, and the CO and CO₂ contents in the product gas were reduced by the reverse Boudouard reaction. A naphtha-reforming catalyst (46-5Q) exhibited better performance in the steam reforming of toluene at temperatures over 873 K than a methane-reforming catalyst (Reformax 330). Ni/Ru–Mn/Al₂O₃ catalysts showed high toluene reforming performance at temperatures over 873 K. The results indicate that the observed high stability and coking resistance may be attributed to the promotional effects of Mn on the Ni/Ru–Mn/Al₂O₃ catalyst.     

Furfural steam reforming over Ni-based catalysts. Influence of Ni incorporation method

Catalytic steam reforming of biomass-derived compounds as furfural could be a promising option to produce renewable hydrogen; however efficient catalysts are still under study. Different commercial supports (SiO₂, Al₂O₃, ASA, MgO, MgAl₂O₃, ZnO, TiO₂, Natural Sepiolite) incorporating Ni by incipient wetness impregnation have been initially tested in the Steam Reforming of Furfural (SRF). Among them, Ni supported in natural sepiolite exhibited the best catalytic activity. In order to improve the catalytic performance of this sepiolite-based catalyst an alternative method for the incorporation of Ni was explored (precipitation). Precipitation method led to a Ni-based catalyst highly active and selective in the production of hydrogen. In addition, the production of undesired products (CO and acetone) decreased significantly. Characterization by BET area, XRD, TEM and TPR shows that precipitation method allows to synthesize a Ni-based catalyst with higher BET surface area and smaller metallic nickel particles. These particular physico-chemical properties seem to be the major responsible of the better catalytic performance exhibited by the material prepared by precipitation.     

Steam reforming of gasoline promoted by partial oxidation reaction on novel bimetallic Ni-based catalysts to generate hydrogen for fuel cell-powered automobile applications

Steam reforming of gasoline fuels combined with partial oxidation reaction on ZSM-5-supported Ni-based bimetallic catalysts and Al₂O₃-supported Ni-Re bimetallic catalysts with different Ni/Re ratios for hydrogen generation at a relatively lower reaction temperature was studied. The ZSM-5-supported Ni-Ce and Ni-Mo bimetallic catalysts exhibited a higher activity than the Ni/ZSM-5 catalyst for the oxidative reforming of gasoline. Steam reforming of gasoline to produce hydrogen was remarkably promoted by partial oxidation reaction by addition of molecular oxygen to the reaction system on ZSM-5-supported Ni-Ce catalyst. Al₂O₃-supported Ni-Re catalyst with suitable Ni/Re ratios exhibits unique high activity and sulfur tolerance because of the alloying of Ni with Re to form a new active sites for oxidative steam reforming of gasoline to generate hydrogen. The crystal structure of Al₂O₃-supported bimetallic Ni-Re catalyst and monometallic catalysts of Ni and Re were characterized by XRD method. Structured changes resulting from the alloying of Ni with Re were found.     

A comparative study of catalytic behaviors of Mn,Fe, Co,Ni, Cu and Zn–Based catalysts in steam reforming of methanol,acetic acid and acetone

This study investigated the distinct catalytic behaviors of mono Mn, Fe, Co, Ni, Cu and Zn catalysts in the reforming of the small organics including methanol, acetic acid and acetone. The results showed that Mn, Fe or Zn-based catalysts showed almost no activity for steam reforming of either methanol, acetic acid or acetone, due to their low capacity to break the chemical bonds of the organics or to activate steam. Co and Cu-based catalysts were generally active for steam reforming of methanol. Nevertheless, Co-based catalysts promoted methanol decomposition to form a substantial amount of CO. Alumina as a support remarkably influenced catalytic stability of the catalyst. The unsupported Cu catalyst showed a much lower stability than Cu/Al₂O₃. Nevertheless, the unsupported Ni was more stable than Ni/Al₂O₃ catalyst, due to its high resistivity towards coking. The unsupported Co, however, was prone to coking. The C/H ratios in the coke formed over the unsupported and alumina-supported Ni or Co catalysts were distinct, indicating the involvement of alumina in the coking process. In addition, Ni and Co catalysts behaved differently. Ni/Al₂O₃ showed a superior stability than Co/Al₂O₃ in steam reforming of acetone. The coke formed on Ni/Al₂O₃ was more aromatic than that over Co/Al₂O₃ catalysts while morphologies of coke (nanotubes over Ni/Al₂O₃ versus fibrous coke over Co/Al₂O₃) were also different.     

Catalytic steam reforming of glycerol over Ni–La2O3–CeO2/SBA-15 catalyst for stable hydrogen-rich gas production

Ni-based catalysts (Ni, Ni–La₂O₃, and Ni–La₂O₃–CeO₂) on mesoporous silica supports (SBA-15 and KIT-6) were prepared by an incipient wetness impregnation and tested in glycerol steam reforming (GSR) for hydrogen-rich gas production. The catalysts were characterized by the N₂-physisorption, TPD, X-ray diffraction (XRD), SEM-EDS, and TEM techniques. N₂-physisorption results of calcined catalysts highlight that adding of La₂O₃ increased surface area of the catalyst by preventing pore mouth plugging in SBA-15, which was frequently observed due to the growth of NiO crystals. A set of GSR experiments over the catalysts were performed in an up-flow continuous packed-bed reactor at 650 °C and atmospheric pressure. The highest hydrogen concentration of 62 mol% was observed with a 10%Ni–5%La₂O₃ –5%CeO₂/SBA-15 catalyst at a LHSV of 5.8 h⁻¹. Adding of CeO₂ to the catalyst appeared to increase catalytic stability by facilitating the oxidative gasification of carbon formed on/near nickel active sites of Ni–La₂O₃–CeO₂/SBA-15 and Ni–La₂O₃–CeO₂/KIT-6 catalyst during the glycerol steam reforming reaction.     

Hydrogen production by steam reforming of liquefied natural gas (LNG) over nickel catalysts supported on cationic surfactant-templated mesoporous aluminas

Two types of mesoporous γ-aluminas (denoted as A-A and A-S) are prepared by a hydrothermal method under different basic conditions using cationic surfactant (cetyltrimethylammonium bromide, CTAB) as a templating agent. A-A and A-S are synthesized in a medium of ammonia solution and sodium hydroxide solution, respectively. Ni/γ-Al₂O₃ catalysts (Ni/A-A and Ni/A-S) are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of a mesoporous γ-Al₂O₃ support on the catalytic performance of Ni/γ-Al₂O₃ is investigated. The identity of basic solution strongly affects the physical properties of the A-A and A-S supports. The high surface-area of the mesoporous γ-aluminas and the strong metal–support interaction of supported catalysts greatly enhance the dispersion of nickel species on the catalyst surface. The well-developed mesopores of the Ni/A-A and Ni/A-S catalysts prohibit the polymerization of carbon species on the catalyst surface during the reaction. In the steam reforming of LNG, both Ni/A-A and Ni/A-S catalysts give better catalytic performance than the nickel catalyst supported on commercial γ-Al₂O₃ (Ni/A-C). In addition, the Ni/A-A catalyst is superior to the Ni/A-S catalyst. The relatively strong metal–support interaction of Ni/A-A catalyst effectively suppresses the sintering of metallic nickel and the carbon deposition in the steam reforming of LNG. The large pores of the Ni/A-A catalyst also play an important role in enhancing internal mass transfer during the reaction.     

Steam reforming of acetic acid for hydrogen production over Ni/CaxFeyO catalysts

Three Ni/Ca_xFe_yO (x/y = 2:1, 1:1, 1:2) catalysts are prepared by impregnation method and applied in steam reforming of acetic acid as the model compound of bio-oil for hydrogen production. The effects of reaction temperature, steam to carbon ratio (S/C), liquid hourly space velocity (LHSV) on gas contents and H₂ yield are carefully investigated and optimized. The fresh and used catalysts are characterized by BET, XRD, H₂-TPR, CO₂-TPD, SEM and TG methods. The experimental and characterization results show that the Ni/CaFe₂O₄ catalyst displays the best activity and stability among the three catalysts, providing 92.1% of H₂ yield under S/C = 5, LHSV = 3.4 h⁻¹ and at 600 °C. The strong interaction between Ni and CaFe₂O₄ support result in the formation of Ni–Fe alloy and Ca₂Fe₂O₅, which shows the synergistic effects on the resistant to carbon deposition and metal sintering, thereby improving the activity and stability of the Ni/CaFe₂O₄ catalyst.     

Renewable hydrogen production via steam reforming of simulated bio-oil over Ni-based catalysts

The production of hydrogen via steam reforming (SR) of simulated bio-oil (glycerol, syringol, n-butanol, m-xylene, m-cresol, and furfural) was investigated over Ni/CeO₂-Al₂O₃ and Me-Ni/CeO₂-Al₂O₃ (Me = Rh, Ru) catalysts. Monometallic (Ni) and bimetallic (Rh-Ni and Ru-Ni) catalysts were prepared by the wetness impregnation technique of the CeO₂-Al₂O₃ support previously synthesized by the surfactant-assisted co-precipitation method. The as-prepared powders were systematically characterized by N₂-physisorption, XRD, H₂-TPR, and TEM measurements to analyze their structure, morphology, and reducibility properties. Experiments were performed in a continuous fixed-bed reactor at atmospheric pressure, temperature of 800 °C, steam to carbon (S/C) ratio of 5, and WHSV of 21.15 h⁻¹. Then, the temperature was decreased to 700 °C and increased afterwards to 800 °C. After the experiments TPO and TEM analysis were performed on the spent catalysts to check any evidence of catalyst deactivation. The results showed that the incorporation of noble metal (Ru or Rh) promoter positively affected the activity of the Ni/CeO₂-Al₂O₃ catalysts by enhancing the reducibility of Ni²⁺ species. Ni-based catalyst deactivated under the studied conditions, whereas Ru- and mainly Rh-promoted systems showed increased resistance to carbon deposition by favouring the gasification of adsorbed carbon species. Between all tested catalysts, the Rh-Ni/CeO₂-Al₂O₃ provided the highest H₂ yield and coking-resistance in SR of simulated bio-oil.     

Hydrogen production from methane and natural gas steam reforming in conventional and microreactor reaction systems

Ni-based (over MgO and Al₂O₃) and noble metal-based (Pd and Pt over Al₂O₃) catalysts were prepared by wet impregnation method and thereafter impregnated in microreactors. The catalytic activity was measured at several temperatures, atmospheric pressure and different steam to carbon, S/C, ratios. These conditions were the same for conventional, fixed bed reactor system, and microreactors. Weight hourly space velocity, WHSV, was maintained equal in order to compare the activity results from both reaction systems. For microreactor systems, similar activities of Ni-based catalyst were measured in the steam methane reforming (SMR) activity tests, but not in the case of natural gas steam reforming tests. When noble metal-based catalysts were used in the conventional reaction system no significant activity was measured but all catalysts showed some activity when they were tested in the microreactor systems. The analysis by SEM and TEM revealed a carbon-free surface for Ni-based catalyst as well as carbon filaments growth in case of noble metal-based catalysts.     

生物油模型物乙酸水蒸汽催化重整制氢研究

选择乙酸作为生物质快速裂解油(生物油)的模型物,自制了一系列Ni基催化剂,进行水蒸汽催化重整制氢研究,实验结果表明Ni/Al_2O_3催化剂添加碱性氧化物MgO或(与)La_2O_3可以使得催化剂的活性有重大改善。Al_2O_3载体负载Ni金属后能够减缓碳的沉积速率,Ni/Al_2O_3添加MgO与(或)La_2O_3能够有效减少碳的沉积速率。选择催化剂Ni/MgO-La_2O_3-Al_2O_3以反应气中的H_2、CO、CH_4、CO_2产率为考察指标,考察反应温度、水碳比、进料流量对水蒸汽催化重整乙酸制氢反应的影响,获得较佳的条件为:反应温度为750～850℃,水碳摩尔比[W]/[C]为5～9,进料流量为15～25mL/h,H_2产率较高,大于80%。     

Hydrogen production by low-temperature reforming of organic compounds in bio-oil over a CNT-promoting Ni catalyst

Present study reports on high catalytic activity of CNTs-supported Ni catalyst (x% Ni-CNTs) synthesized by the homogeneous deposition–precipitation method, which was successfully applied for low-temperature reforming of organic compounds in bio-oil. The optimal Ni-loading content was about 15 wt%. The H₂ yield over the 15 wt% Ni-CNTs catalyst reached about 92.5% at 550 °C. The influences of the reforming temperature (T), the molar ratio of steam to carbon fed (S/C) and the current (I) passing through the catalyst, on the reforming process of the bio-oil over the Ni-CNTs' catalysts were investigated using the stream as the carrier gas in the reforming reactor. The features of the Ni-CNTs' catalysts with different loading contents of Ni were investigated via XRD, XPS, TEM, ICP/AES, H₂-TPD and the N₂ adsorption–desorption isotherms. From these analyses, it was found that the uniform and narrow distribution with smaller Ni particle size as well as higher Ni dispersion was realized for the CNTs-supported Ni catalyst, leading to excellent low-temperature reforming of oxygenated organic compounds in bio-oil.     

Development of activated biochar supported Ni catalyst for enhancing toluene steam reforming

Catalytic steam reforming of tar is considered to be an attractive pathway for tar removal and H₂ production in the modern world. In this study, activation of biochar (B) from pine wood pyrolysis was performed to boost its specific surface area and pore structure. The activated biochar (AB) was used as a catalyst support with the aim to enhance the catalytic activity. The catalytic reforming performance of toluene over Ni/AB catalyst was investigated, and the catalytic behavior of Ni/AB catalysts was compared with Ni/Al₂O₃ and Ni/B. The effect of potassium hydroxide (KOH) to biochar ratio, Ni loading, reforming temperature, weight hourly space velocity and steam to carbon ratio(S/C) on the performance of Ni/AB catalysts were studied. The results showed that Ni/AB catalysts exhibited a superior catalytic activity for carbon conversion and H₂ production to Ni/B and Ni/Al₂O₃ catalysts. In addition, high carbon conversion (86.2%) and H₂ production (64.3%) can be achieved with Ni/AB catalyst under the optimal operating conditions. Furthermore, in order to improve the stability of the Ni/AB catalyst, Ce was introduced to Ni/AB catalyst. According to stability tests, the H₂ concentration of Ni-Ce/AB catalysts was still higher than 2.24 mmol/min even after 20 hours reaction.     

Lanthanoid-containing Ni-based catalysts for dry reforming of methane: A review

Dry reforming of methane (DRM) is known to produce synthesis gas through the utilization of greenhouse gases to ensure environmentally benign process and rational use of natural resources. Many catalyst formulations operating at “ideal” conditions were proposed for DRM reaction, including those based on noble (Pt, Rh) and non-noble (Ni, Co) metals supported on various oxides. This review is focused on the recent advances in lanthanoid-containing Ni-based DRM catalysts. We consider the performance of Ni-based catalysts supported on LnO_x oxides (La₂O₃, CeO₂, etc.), promotion of the said composites by noble or transition metals, organization of pristine and promoted Ni–LnO_x interfaces on the surfaces of various supports, including ordered materials. Analysis of features of the high-performance DRM catalysts is provided. The outlook of the existing challenges and opportunities in the rational design of a new generation of lanthanoid-containing Ni-based catalysts for dry reforming of methane and other hydrocarbons is provided.     

Characterization and activity test of commercial Ni/Al2O3, Cu/ZnO/Al2O3 and prepared Ni–Cu/Al2O3 catalysts for hydrogen production from methane and methanol fuels

In this study, methane and methanol steam reforming reactions over commercial Ni/Al₂O₃, commercial Cu/ZnO/Al₂O₃ and prepared Ni–Cu/Al₂O₃ catalysts were investigated. Methane and methanol steam reforming reactions catalysts were characterized using various techniques. The results of characterization showed that Cu particles increase the active particle size of Ni (19.3 nm) in Ni–Cu/Al₂O₃ catalyst with respect to the commercial Ni/Al₂O₃ (17.9). On the other hand, Ni improves Cu dispersion in the same catalyst (1.74%) in comparison with commercial Cu/ZnO/Al₂O₃ (0.21%). A comprehensive comparison between these two fuels is established in terms of reaction conditions, fuel conversion, H₂ selectivity, CO₂ and CO selectivity. The prepared catalyst showed low selectivity for CO in both fuels and it was more selective to H₂, with H₂ selectivities of 99% in methane and 89% in methanol reforming reactions. A significant objective is to develop catalysts which can operate at lower temperatures and resist deactivation. Methanol steam reforming is carried out at a much lower temperature than methane steam reforming in prepared and commercial catalyst (275–325 °C). However, methane steam reforming can be carried out at a relatively low temperature on Ni–Cu catalyst (600–650 °C) and at higher temperature in commercial methane reforming catalyst (700–800 °C). Commercial Ni/Al₂O₃ catalyst resulted in high coke formation (28.3% loss in mass) compared to prepared Ni–Cu/Al₂O₃ (8.9%) and commercial Cu/ZnO/Al₂O₃ catalysts (3.5%).     

Ni/Pd-promoted Al2O3–La2O3 catalyst for hydrogen production from polyethylene terephthalate waste via steam reforming

Ni/Pd-co-promoted Al₂O₃–La₂O₃ catalysts for selective hydrogen production from polyethylene terephthalate (PET) plastic waste via steam reforming process has been investigated. The catalysts were prepared by impregnation method and were characterized using XRD, BET, TPD-CO₂, TPR-H₂, SEM, TGA and DTA. The results showed that Ni-Pd-co-impregnated Al₂O₃–La₂O₃ catalyst has excellent activity for the production of hydrogen with a prolong stability. The feed conversion of 87% was achieved over 10% Ni/Al₂O₃ catalyst which increased to 93.87% in the case of 10% Ni-1% Pd/Al₂O₃–La₂O₃ catalysts with an H₂ fraction of 0.60. The catalyst performance in term of H₂ selectivity and feed conversion was further investigated under various operating parameters, e.g., temperatures, feed flow rates, feed ratios and PET concentrations. It was found that the temperature has positive effects on H₂ selectivity and conversion, yet feed flow rate has the adverse effects. In addition, PET concentrations showed improved in H₂ selectivity in comparison to when only phenol as a solvent was involved. The Ni particles, which are the noble-based active species are more effective, thus offered good hydrogen production in the PET steam reforming process. Incorporation of La₂O₃ as support and Pd as a promoter to the Ni/Al₂O₃ catalyst significantly increased catalyst stability. The Ni–Pd/Al₂O₃–Al₂O₃ catalyst showed remarkable activity even after 36 h along with the production of carbon nanotubes, while H₂ selectivity and feed conversion was only slightly decreased.     

Production of hydrogen by steam reforming of phenol over Ni/Al2O3-ash catalysts

An improved method for hydrogen production by the steam reforming of phenol over novel fly ash-based catalysts is investigated. The Ni/Al₂O₃-ash catalysts are prepared by an equal-volume impregnation method and characterized by XRD, FESEM, BET and H₂-TPR techniques. The effects of various process parameters including mixing ratio of fly ash, temperature, support, gas hourly space velocity (GHSV) and steam-to-carbon molar ratio (S/C) on the catalytic activity are investigated. The results show that fly ash mixing at 50 wt% and choosing γ-Al₂O₃ as the support own the best performance. A maximum hydrogen yield of 83.8% is achieved at 450 °C with a S/C of 10 and a GHSV of 4968 h^?1 with a maximum phenol conversion of 98.6%. The stability of the Ni-ash1-γA1 catalyst is further investigated and it is shown to continuously and stably react for more than 20 h at 450 °C with excellent catalytic reaction stability.     

Hydrogen production from acetic acid steam reforming over Ti-modified Ni/Attapulgite catalysts

Steam reforming of bio-oil derived oxygenates is a green and sustainable method for hydrogen production. In this work, hydrogen production from steam reforming of acetic acid (SRAA) was investigated over Ti-modified Ni/Attapulgite (ATP) catalysts that prepared via sequential precipitation technique. The effects of Ti additive, precipitation sequence and Ti-salt precursors (TiCl₄, TiOSO₄) on the structural and physicochemical properties of catalysts were characterized by N₂ adsorption-desorption, XRD, FT-IR, HRTEM, XPS, H₂-TPR and NH₃-TPD. These results indicated that the interaction among Ti species, Ni active metal and ATP enhanced the reduction performance as well as weakened surface acidity of the Ni/ATP catalyst, and also promoted the electron transfer to form Ni^δ? species. Obviously, compared with Ti precursor salts, the precipitation sequences played a key role in determining the surface properties of Ti-modified catalysts. Among them, the Ni–Ti_S/ATP catalyst synthesized by co-precipitation method exhibited better reducibility and lower surface acidity, as well as produced more Ni^δ? species and Ni^δ?-O_v-Ti³⁺ interface sites. Then the synergistic effects among the above-mentioned characters made the Ni–Ti_S/ATP catalyst present highest carbon conversion (93.4%) and H₂ yield (77.6%) during SRAA reactions. The analyses of XRD, HRTEM and TG were implemented on used catalysts and discovered Ni–Ti_S/ATP catalysts shown promising metal sintering and coke resistance, which mainly caused by the presence of flat Ni–Ti@ATP structures. The possible conversion mechanism of acetic acid in the flat Ni–Ti@ATP structure of co-precipitation Ti-modified catalyst was also elucidated.