Sn-Beta is a good Lewis acid catalyst. Typically, the organic template in as-made Sn-Beta was removed by calcination in air atmosphere at high temperature (>= 500 degrees C). The fast combustion of organic template in air would lead that the actual temperature of sample is out of control, which will result in the partial disintegration of framework Sn species that are the active centers for catalytic reactions. In this work, ozonization at mild conditions (<= 200 degrees C) was used to remove the organic template. It was found that the ozonization temperature greatly affected the template removal. The template removal efficiency reached 89 % at 120 degrees C for 3 h. The ozonized Sn-Beta has more framework Sn sites than Sn-Beta-C, for which the template was removed by traditional calcination route. However, the ozonized Sn-Beta showed slightly poor performance for conversion of glucose to methyl lactate (MLA) than Sn-Beta-C due to the presence of a few organic template. After the template residues were further removed by calcination of the ozonized Sn-Beta in air at 200-250 degrees C for 1 h, the catalytic performance of the ozonized Sn-Beta was significantly improved. Glucose conversion of 98.9 % with 48.7 % yield to MLA at 140 degrees C for 5 h was obtained over the ozonized Sn-Beta re-calcinated at 200 degrees C for 1 h.

Sn-Al-Beta zeolites with less silanol defects were synthesized in fluoride media. The effects of the amount of organic template (tetraethylammonium hydroxide, TEAOH), mineralizer (NH4F), Al and Sn on the synthesis, acidity and catalytic performance were systematically studied. The synthesized Sn-Al-Beta zeolites were characterized by XRD, SEM, 27Al MAS NMR, UV-vis DRS and FT-IR spectroscopy of hydroxy region and pyridine adsorption. The optimum values of nTEAOH/nSi and nF-/nSi were same (0.3) for synthesizing Sn-Al-Beta with high crystallinity at 140 oC for 7 d. Moreover, decreasing nF-/nSi facilitated the incorporation of Al into the framework. The crystallization rate of Sn-Al-Beta is similar with that of Sn-Beta. Sn was promoted to enter the framework with the increase of Al content, while elevating Sn content has no effect on the incorporation of Al into the framework. The catalytic performance of Sn-Al-Beta was investigated for conversion of glucose to 5-hydroxymethylfurfural in water-containing solvent. Sn-Al-Beta synthesized in fluoride media is more stable than the post-synthesized sample.

Sn-Beta zeolite is an excellent catalyst for the transformation of biomass derived carbohydrates. However, the long synthesis time restricted its application. Here, alkaline (earth) salt was used as promoter to accelerate the crystallization of Sn-Beta. Different alkaline (earth) salts and the amount of MgCl2 were investigated. The properties of the synthesized samples were characterized by various techniques and compared with Sn-Beta, and the catalytic performance was investigated for the conversion of glucose to methyl lactate (MLA). The results indicate that a small amount of alkaline (earth) salt, especially MgCl2, promoted dramatically the crystallization of Sn-Beta. The full crystallization time was shortened from 15 d to 5 d with the aid of MgCl2 (n(Mg)/n(Sn) of 1.0) for Sn-Beta with n(Si)/n(Sn) of 100. Sn4+ cations were incorporated into the framework sites, while Mg2+ cations replaced the protons of silanol defects. Mg-Sn-Beta with strong Lewis acid sites and less silanols showed high activity and selectivity for glucose conversion to MLA. The yield of MLA is 20% over the fully crystallized Sn-Beta at 120 C for 15 h and glucose concentration of 3.1 wt%, which increased significantly to 44% over the fully crystallized 1 Mg-Sn-Beta. Furthermore, Mg-Sn-Beta is stable and recyclable.

Sn-Beta zeolites were successfully synthesized through a quasi-solid-phase method by grinding the raw materials and then crystallizing in solid state. The method employed small amount of tetraethyl ammonium hydroxide (TEAOH) and no additional solvent, except for the water contained in template solution. The synthesis conditions including amount of TEAOH and water, and crystallization time were explored. Under optimized conditions, the obtained sample showed high crystallinity and capped square bipyramidal crystals. The diffuse reflectance ultraviolet-visible spectra and Fourier transform infrared spectra of CD3CN and pyridine adsorption were used to characterize the state of Sn and acidity in Sn-Beta sample. Sn4+ ions were introduced into the framework which generated strong Lewis acid sites. The sample synthesized by quasi-solid-phase method gave 38.5 % methyl lactate (MLA) yield for the conversion of glucose to MLA, which is comparable to that of Sn-Beta prepared with conventional hydrothermal method (39.4 %).

Sn-β samples with nSi/nSn from 1600 to 100 were hydrothermally synthesized, characterized and tested for transforming glucose to methyl lactate (MLA). Both the amount of framework Sn and extraframework Sn increased with raising Sn content in the synthesis gel; moreover the silanol defects also increased. For converting glucose to MLA, the TOF value of MLA production reduced as the Sn content rose due to the increased silanol defects and extraframework Sn. The maximum MLA productivity ( 104 g kgcatalyst‒1 h‒1) was achieved at nSi/nSn of 400–200 when the glucose concentration was 9.3 wt

Surface charge-transfer complex formed by TiO2 and phenols has showed a great potential in visible-light photocatalysis. However, back electron transfer limits the charge transfer efficiency and the activation of phenols in surface complex. Herein, we disclosed the efficient activation of phenols in surface complex by introducing the base. Both homocoupling reactions and butylated hydroxytoluene-trapped experiments clearly demonstrated the generation of phenolic radicals from various lignin-derived substrates. The addition of base caused the blue-shifted absorption of surface complex, while increased the visible light-induced electron excitation from substrate to TiO2. Vibrational spectra suggested that the interaction between phenolate and TiO2 was stronger than the interaction between neutral phenol and TiO2. This base-triggered strategy may be conducive to useful transformations or degradation of phenols via surface complex.

The development of selectivity control strategies based on external operational conditions without modification of catalyst is an attractive but challenging issue in photocatalysis. Herein we reported the substrate concentration‐switched selectivity in photocatalytic transfer hydrogenation of biomass‐derived aromatic aldehydes. With the same catalyst, hydrodeoxygenation was realized at low aldehyde concentration and reductive etherification was realized at high aldehyde concentration. Mechanistic studies revealed that the substrate concentration affected the electron density on catalyst, thus controlled the initial reduction of formyl group and types of intermediates. Competitive adsorption of these intermediates on the catalyst affected hydrogenolysis of C−O bonds in the later stage. This method is easy to handle, and achieved selective hydrogenation of diverse bio‐based aldehydes to corresponding deoxygenated products and unsymmetric ether products as potential fuel additives under mild conditions. This work sheds light on the effect of substrate concentration on the selectivity in photocatalysis.

Sn-Beta is a good solid Lewis acid catalyst. Seed-assisted hydrothermal synthesis is a popular method for its preparation. However, the mechanism of seeds in the crystallization process is not clear. Here, the role of seeds in the growth of crystal and the influence on the properties of the corresponding products were studied. The seeds and gel was characterized by XRD, SEM, FT-IR and TG. During the crystallization, it was observed that the seeds were partially dissolved and formed seed fragments in the initial stage. Then the seed fragments acted as the core of the crystals and promoted the crystallization process. Seeds greatly decreased the crystal size of the products as compared with the direct hydrothermal method in absence of seeds. The acidity and catalytic performance of Sn-Beta synthesized via seeds route are similar with those of none-seeds method.

Sn-beta with strong Lewis acid sites is considered as the state-of-the-art solid catalyst for converting glucose to alkyl lactate. However, the extensive use of organic template and mineralizing agent and long preparation period in the synthesis of Sn-beta brought serious environmental pollution and high synthesis cost. Herein, a cost-effective and fast synthesis strategy using fewer organic template and mineralizing agent, fumed silica as Si source, Mg2+ cation as crystallization promoter and without additional solvent, is proposed to alleviate the aforemen-tioned shortcomings. The results reveal that highly crystalline Mg-Sn-beta can be synthesized in 3 days from the gel of 0.005MgO/0.005SnO(2)/SiO2/0.15TEAOH/0.15NH(4)F/3.75H(2)O. Besides accelerating the crystallization, it is found that Mg2+ cation facilitated Sn(4+ i)ncorporation into the framework site and lessened the silanol defects of zeolite notably. For conversion of glucose to methyl lactate (MLA), a higher yield of MLA was obtained over 1Mg-Sn-beta-3d (54.4%) compared with Sn-beta-H-7d (37.2%) and Sn-beta-7d (41.3%).

Corncob is one of the main by-products of agricultural biomass in corn-producing area. Here, the valorization of corncob polysaccharide components to produce furfural and glucose was studied. Firstly, corncob was treated by high-pressure CO2-H2O; the in situ formed-carbonic acid catalyzed the selective hydrolysis of hemicellulose component with xylo-oligosaccharide and xylan as the main products. The obtained liquid fraction was further upgraded to furfural with H2SO4 as catalyst. After reaction at 140 °C for 1 h, 7.0 g L−1 of furfural was given. The conversion of C5 sugar and the selectivity of furfural was 56

Hydrolysis of cellulose to glucose is one of the most important processes for the conversion of biomass to fuels and chemicals. Besides cellulose, lignin is the third of the main components of native lignocellulose. It is essential to understand the role of lignin in the depolymerization process of cellulose using lignocellulose as raw material. Here, the role of lignin was studied by using a lignin dimer model with a β-O-4 linkage and an organsolv lignin as the additive, respectively, for depolymerization of cellulose via oxidation-hydrolysis method. The results showed that both lignin dimer model and organsolv lignin substantially promoted the oxidation of cellulose and increased the yield of glucose. 30.01% yield of glucose was given for microcrystalline cellulose in present of 10% organsolv lignin, compared to 22.64% glucose yield for pure microcrystalline cellulose. Additionally, the mechanism of the promotion effect of lignin on the oxidation of cellulose process was proposed.

Sn-Beta zeolite is a promising heterogeneous Lewis acid catalyst. Hydrothermal synthesis of Sn-Beta(TEOS) using tetraethyl orthosilicate (TEOS) as silica source is a classical method. However, the hydrolysis of TEOS generates considerable ethanol, which is unfavorable for scalable production of Sn-Beta. Herein, cheap fumed silica and silica sol were used as Si sources to synthesize Sn-Beta and compared with that synthesized from TEOS. The crystalline phase, morphology, physicochemical properties, and the state of Sn were characterized. It was found that Sn-Beta can be successfully prepared with fumed silica and silica sol as well as TEOS as silica source. Sn was introduced into the framework of these samples. Sn-Beta synthesized from fumed silica (Sn-Beta(FS)) and silica sol (Sn-Beta(Sol)) had similar crystallization behavior and full crystallization time as well as morphology, crystal size with that from TEOS. Sn-Beta(Sol) has less silanols and lowest ratio of open/closed tin site among these samples. It exhibited higher catalytic activity for the conversion of glucose to methyl lactate and lower catalytic activity for the isomerization of glucose as compared with the other two samples. Sn-Beta(FS) showed similar catalytic performance in the studied reactions with Sn-Beta(TEOS).

A facile approach has been developed to fabricate hierarchical SAPO-34 with large intracrystalline meso/macropores and excellent catalytic performance in the MTO reaction.

Correction for ‘Rational construction of hierarchical SAPO-34 with enhanced MTO performance without an additional meso/macropore template’ by Yafei Liang et al., J. Mater. Chem. A, 2021, DOI: 10.1039/d0ta08437a.

Mg-Sn-Beta zeolites with different Mg/Sn molar ratios were prepared from the parent deAl-Beta by a coimpregnation method. It shows higher selectivity for the conversion of glucose to methyl lactate than post-synthesized Sn-Beta.

Hydrothermally synthesized Sn-Beta is an excellent catalyst for the conversion of sugars to alkyl lactates. However, its catalytic performance is highly dependent on the synthesis parameters. In this work, the effects of the synthesis parameters such as the water amount of the synthesis gel and the crystallization time on the synthesis and properties and catalytic performance of Sn-Beta in the conversion of glucose to methyl lactate (MLA) were investigated. The crystallization rate was accelerated remarkably by reducing the water amount of the synthesis gel. With the aid of the Si-Beta seed, Sn-Beta was almost fully-crystallized after one day with nH2O/nSiO2 of 4.5, but seven days were needed with nH2O/nSiO2 of 7.5. However, Sn-Beta synthesized with nH2O/nSiO2 of 4.5 has more extraframework SnO2 due to the fast formation of the *BEA structure and the slow incorporation of Sn4+ into the framework sites, which resulted in the lower activity of MLA formation. More Sn4+ species were incorporated into the framework sites and thus more Lewis acid sites were generated with increasing crystallization time. At the same time, the ratio of open to closed Sn sites (RO/C) increased, which led to the decrease in the activity of MLA formation and due to that, the open Sn site with a proximal silanol is unfavorable for the conversion of glucose to MLA. During recycling study, it is surprisingly found that the yield of MLA increased gradually over the fully-crystallized Sn-Beta catalyst. Characterization results of the recovered catalyst from the eighth run indicate that the structure was preserved well, but the value of RO/C reduced due to the change of the state and microenvironment of Sn species.

Conversion of cellulose to chemicals is an economic and environmental route for biomass utilization. In this work, efficient conversion of cellulose to alkyl levulinates and levulinic acid was realized by oxidation pretreatment combined with alcoholysis over Al2(SO4)3 catalyst. Proper pre-oxidation conditions including oxidation temperature and time are important. By pre-oxidation, part of hydroxymethyl groups on cellulose was converted to carboxyl groups which provide the Brønsted acid sites near the glycosidic bonds to improve the depolymerization of cellulose to monosaccharide. Al2(SO4)3·18H2O can play both Brønsted and Lewis acid roles in methanol and catalyze the conversion of monosaccharide to alkyl levulinates and levulinic acid. After pre-oxidation at optimized conditions, cellulose can be converted into methyl levulinate and levulinic acid over Al2(SO4)3 in methanol efficiently, and total yield of methyl levulinate and levulinic acid can reach 66.8% at 180 °C for 3 h. Furthermore, the simple and cheap Al2(SO4)3 catalyst is recyclable which is important for the practical application.

Synthesis of light hydrocarbons from synthesis gas using bifunctional catalysts consisting of CuO–ZnO–Al2O3 methanol synthesis catalysts and SAPO-5 were investigated in a fixed bed reactor. The operating results showed that both the temperature and the ratio of CZA/SAPO-5 influenced the CO conversion and the selectivity of the catalysts. The effects of different dehydration component such as HZSM-5, HMOR and SAPO-5 and subsequently the impact of the zeolite acidity on the catalytic performance were also investigated. Experimental results indicated that zeolites in bifunctional catalysts played the crucial role for the distribution of hydrocarbons, and SAPO-5 was superior to the other zeolites in terms of better conversion and C3–C5 selectivity due to its suitable topology and proper acidic property. The efficiency of the CZA/SAPO-5 catalysts was found to be directly proportional to the Brönsted acid sites density of the zeolite and Brönsted acid sites are the likely zeolite active sites for DME dehydration. High time–space yield (461.6 mg mL−1 h−1) and high selectivity (88.1%) of light hydrocarbons (C3–C5) could be achieved on the CZA/SAPO-5-0.4 catalyst at 290 °C.

One-pot conversion of cellulose to valued-added platform chemicals such as alkyl levulinate is a promising and challenging process of biomass utilization due to the insolubility of cellulose in alcohol. In this work, commercial heteropoly acid combined with postsynthesized Sn-Beta zeolite was employed to transform cellulose to methyl levulinate (MLE) in one pot. The synergistic catalysis of the homogeneous strong Brønsted (B) acid and the solid strong Lewis (L) acid can effectively realize the depolymerization of solid cellulose and the subsequent isomerization, dehydration and hydration steps to MLE. 55% and 62% of MLE yields were obtained from α-cellulose and microcrystalline cellulose, respectively, at 160 °C for 10 h. Various carbohydrates besides cellulose can also be efficiently converted to MLE in high yields over the bifunctional catalyst system. The effects of the amount of B acid and L acid, the reaction temperature and time and the amount of cellulose on the production of MLE were investigated in detail. Finally, the reaction pathway of cellulose to MLE was revealed. Recyclability tests indicated that the binary catalyst can be reused without decrease of catalytic activity.