High selective production of tetrahydrofurfuryl alcohol: Catalytic hydrogenation of furfural and furfuryl alcohol

Tetrahydrofurfuryl alcohol could be obtained by catalytic hydrogenation of either furfural or furfuryl alcohol using Pd-, Ru-, Rh- and Ni-supported catalysts as well as their mixtures with a Cu-supported catalyst. In the case of furfural hydrogenation, the best results (97 % yield, 100 % conversion, 98 % selectivity) were obtained in the presence of Ni and Cu. However, this catalytic mixture could not be recycled. In the case of furfuryl alcohol hydrogenation, Ni-supported catalysts were the most active. Nickel-onsilica-alumina catalyst containing 59 % of metal lead to the best results (98–99 % yield, selectivity and conversion >99 %). Moreover, it could be recycled. Hydrogenation of furfuryl alcohol in the presence of this catalyst was the best procedure for the production of tetrahydrofurfuryl alcohol.     

铬形态及使用条件对糠醛催化加氢反应产物分布的影响

采用共沉淀法制备系列Cu-Cr糠醛加氢催化剂,考察不同铬形态对催化剂反应性能的影响。采用管式连续流动固定床积分反应器, 研究糠醛在Cu-Cr催化剂上的气-液相加氢反应规律。结果表明,制备催化剂时的铬原料不同,将极大地影响催化剂的加氢活性和产物选择性,以硝酸铬形式加入制备的催化剂对糠醇的生成较为有利,而以醋酸铬形式加入制备的催化剂对甲基呋喃的形成有利;在(70～110) ℃,随着温度升高,糠醛转化率和糠醇选择性增加,2-甲基呋喃选择性降低;糠醛流速为(0.01～0.06) mL·min^-1时,随着流速的增加,糠醛转化率下降,0.03 mL·min^-1时糠醇选择性出现极大值,而副产物2-甲基呋喃和呋喃类则在此处出现极小值。副产物戊二醇和四氢康醇的选择性则随着糠醛流速的增大上升。     

A highly efficient Cu/MgO catalyst for vapour phase hydrogenation of furfural to furfuryl alcohol

A highly efficient Cu/MgO catalyst for the vapour phase hydrogenation of furfural at atmospheric pressure has been prepared by coprecipitation method. The high conversion of furfural (98%) and high selectivity towards furfuryl alcohol (98%) is attributed to the more number of surface Cu sites as evidenced from N₂O pulse chemisorption technique and the defective sites at Cu and MgO interfacial region.     

糠醇加氢制四氢糠醇催化剂的研究

制备了负载型镍催化剂 ,并加入碱性和过渡金属氧化物助剂 ,各种氧化物总负载量低于催化剂质量的 30 %。在 393～ 413K、0 .2 5～ 0 .4h-1、2 .0～ 4.0MPa条件下 ,用上述催化剂加氢还原糠醇制备四氢糠醇。对于含少量助剂的镍催化剂Ⅱ ,在 393K、4.0MPa和空速 0 .2 5h-1时 ,糠醇转化率可达 99%以上 ,四氢糠醇收率和选择性都达到或接近 97%。在相同反应条件和糠醇转化率条件下 ,四氢糠醇收率和选择性均比没有助剂的镍催化剂Ⅰ高 2 .0 % ,比骨架镍催化剂高3.0 %     

非晶态CoNiB能催化糠醛液相加氢制糠醇

采用化学还原法制备了CoNiB非晶态合金催化剂,并用于糠醛液相加氢制糠醇反应。考察了Ni／Co摩尔比,NaBH4滴加速率等催化剂制备条件对催化性能的影响,以及反应压力、反应时间、反应温度等反应条件对糠醛转化率和糠醇选择性的影响。结果表明：最佳的催化剂制备条件是Ni／Co摩尔比为5／5,NaBH;滴加速率为2．6mL·min2;最佳的反应条件为反应压力2MPa,反应时间3h,反应温度80℃。在此条件下糠醛的转化率为46．2％,糠醇的选择性为90．4％。     

Highly dispersed and confined Ni/MMO catalyst synthesized in a rotating packed bed for hydrogenation of maleic anhydride

Catalytic hydrogenation of maleic anhydride (MA) into succinic anhydride (SA) is one of the most important transformations in synthetic organic chemistry. Herein, we firstly synthesized well-dispersed nickel particles confined by mixed metal oxides (Ni/MMO) derived from in situ transformation of Ni-Al hydrotalcite in a rotating packed bed (RPB) to catalyze this process. A series of Ni/MMO catalysts (63 wt%–89 wt% Ni) were effectively fabricated and the structure–activity relationship was established. Results showed that a Ni/MMO catalyst (82 wt% Ni) with substantial surface defect sites and the highest Ni surface area among the prepared Ni/MMO catalysts, demonstrates the highest activity with ~100% MA conversion and ~100% selectivity to SA under 25°C within 77 min. This is, to our knowledge, the highest conversion and selectivity under room temperature to date. Moreover, the Ni/MMO catalyst prepared by RPB has higher specific surface area and Ni surface area, therefore possessing a higher hydrogenation rate compared to that by stirred tank reactor (1.69 vs. 1.36, 10⁻³·mol_MA/g_cat/min). These results will provide an attractive option of the catalysts for MA hydrogenation, and a novel strategy for synthesizing nickel catalyst derived from Ni-Al hydrotalcite.     

高活性、高选择性骨架镍在糠醇加氢中的应用研究

研究了以骨架镍为加氢催化剂,以糠醇为原料制备四氢糠醇。在中温和高温下制备了两种骨架镍催化剂A和B,研究了不同的反应条件对两种骨架镍催化剂的影响,确定了最佳反应条件。骨架镍催化剂A在60℃,7MPa,用量为4g/100mL糠醇时,四氢糠醇选择性99 56%,收率可达99 41%。骨架镍催化剂B在60℃,5MPa,用量为4g/100mL糠醇时,四氢糠醇的选择性、收率可接近100 00%。     

CO preferential oxidation over Au/MnOx-CeO2 catalysts prepared with ultrasonic assistance: Effect of calcination temperature

The Au/MnO_x-CeO₂ catalysts used for CO preferential oxidation were prepared by deposition-precipitation with ultrasonic assistance. The effect of calcination temperature (150-350 °C) on the structures and catalytic performance of the catalysts was systematically investigated. It is found that the catalyst Au/MnO_x-CeO₂ calcined at 250 °C exhibits the best catalytic performance, giving not only the highest CO conversion of 90.9% but also the highest selectivity of oxygen to CO₂ at 120 °C. The results of XRD, TEM and XPS indicate that this catalyst possesses the smallest particle size, the highest dispersion of Au species and the largest amount of surface adsorbed oxygen species, which are favorable to CO oxidation. The H₂-TPR results reveal that the selectivity of oxygen to CO₂ is mainly determined by the reducibility of Au species in the catalysts. The strong interaction between Au species and the support in Au/MnO_x-CeO₂-250 decreases its capability for H₂ dissociation and oxidation, leading to high selectivity of oxygen to CO₂.     

Synthesis of Biodiesel from Canola Oil Using Heterogeneous Base Catalyst

A series of alkali metal (Li, Na, K) promoted alkali earth oxides (CaO, BaO, MgO), as well as K₂CO₃ supported on alumina (Al₂O₃), were prepared and used as catalysts for transesterification of canola oil with methanol. Four catalysts such as K₂CO₃/Al₂O₃ and alkali metal (Li, Na, K) promoted BaO were effective for transesterification with >85 wt% of methyl esters. ICP-MS analysis revealed that leaching of barium in ester phase was too high (~1,000 ppm) when BaO based catalysts were used. As barium is highly toxic, these catalysts were not used further for transesterification of canola oil. Optimization of reaction conditions such as molar ratio of alcohol to oil (6:1–12:1), reaction temperature (40–60 °C) and catalyst loading (1–3 wt%) was performed for most efficient and environmentally friendly K₂CO₃/Al₂O₃ catalyst to maximize ester yield using response surface methodology (RSM). The RSM suggested that a molar ratio of alcohol to oil 11.48:1, a reaction temperature of 60 °C, and catalyst loading 3.16 wt% were optimum for the production of ester from canola oil. The predicted value of ester yield was 96.3 wt% in 2 h, which was in agreement with the experimental results within 1.28%.     

Benzoylation of anisole over borate zirconia solid acid catalyst

B₂O₃/ZrO₂ solid catalyst containing 30 mol% boron oxide prepared by wet impregnation method and calcined at 500 °C showed efficient catalytic activity in liquid phase benzoylation of anisole with benzoyl chloride (BOC) in nitrobenzene solvent at 150 °C. B₂O₃/ZrO₂ catalyst under study has shown comparable performance with conventional homogeneous AlCl₃ catalyst as well as heterogeneous catalysts such as zeolite H-beta and sulphated zirconia with maximum conversion and selectivity to the corresponding 4-methoxy benzophenone (4-MBP). The effect of various experimental parameters such as temperature, nature of solvent, reaction time and the effect of various benzoylating agents has been discussed. The conversion of anisole to 4-MBP increases significantly with increasing reaction time and temperature. The maximum conversion of about 91% with yield of acylated product >96% and selectivity for 4-MBP >94% was observed after 22 h. 2-MBP was found to be <4%. The phenyl benzoate (3%) formed by the O-benzoylation of anisole was found to be a major side product. The catalyst was recycled three times without any appreciable decrease in the anisole conversion showing its stability.     

Supported Vanadia Catalysts for Dehydrogenation of Ethylbenzene with CO2

Alumina supported vanadia catalysts (V/Al) for selective oxidehydrogenation of ethylbenzene with CO₂ were prepared by impregnation method. During preparation the effect of promoters and calcined temperature was investigated, it was found these two items had a strong influence on the activity of V/Al catalysts. Dehydrogenation reaction with CO₂ was happened in the fixed-bed reactor at 450 °C. Results showed that 15.2% ethylbenzene conversion and 99.2% styrene selectivity were acquired when V₂K/Al catalyst was used.     

糠醛催化加氢制糠醇催化剂Cu/Al2O3的改性研究

研制了一种新型糠醛催化加氢制糠醇的负载型无铬铜基催化剂,并研究了不同助剂以及助剂含量对催化剂性能的影响。发现助剂Ca的加入使得该催化剂在反应温度150℃、反应压力1.0 MPa、氢醛摩尔比8.0的条件下,糠醛转化率为100%、糠醇的选择性为98.9%。     

Structured Ni@NaA zeolite supported on silicon carbide foam catalysts for catalytic carbon dioxide methanation

Carbon dioxide (CO₂) conversion is an important yet challenging topic, which helps to address climate change challenge. Catalytic CO₂ methanation is one of the methods to convert CO₂, however, it is limited by kinetics. This work developed a structured Ni@NaA zeolite supported on silicon carbide (SiC) foam catalyst (i.e., Ni@NaA-SiC), which demonstrated an excellent performance with a CO₂ conversion of ~82%, being comparable to the corresponding equilibrium conversion, and CH₄ selectivity of ~95% at 400°C. The activation energy for CO₂ conversion over the 15Ni@NaA-SiC catalyst is about 31 kJ mol⁻¹, being significantly lower than that of the 15Ni@NaA pelletized catalyst (i.e., ~84 kJ mol⁻¹). Additionally, the structured catalyst was highly stable with sustained CO₂ conversion at 78.7 ± 1.4% and selectivity to CH₄ at 97.7 ± 0.2% over an 80 hr longevity test. In situ diffuse reflectance infrared Fourier transform spectroscopy-mass spectroscopy characterization revealed that catalysis over the structured catalyst proceeded primarily via the CO free mechanism.     

Liquid phase hydrogenation of adiponitrile over directly reduced Ni/SiO2 catalyst

Liquid phase hydrogenation of adiponitrile (ADN) to 6-aminocapronitrile (ACN) and hexamethylenediamine (HMD) was investigated on Ni/SiO₂ catalysts prepared under different conditions. In this reaction, the highly reactive imine intermediate forms condensation byproducts by reacting with the primary amine products (ACN and HMD). A highly dispersed Ni/SiO₂ catalyst prepared by the direct reduction of Ni(NO₃)₂/SiO₂ was found to suppress the condensation reactions by promoting the hydrogenation of adsorbed imine, and it gave excellent hydrogenation activity and primary amine selectivity. Addition of NaOH increased the primary amine selectivity to 79% at the ADN conversion of 86%.     

Influence of alkali metal doping on selectivity behaviour of platinum catalysts for hydrogenation of 2-butyne-1,4-diol

Hydrogenation of 2-butyne-1,4-diol to 2-butene-1,4-diol (B₂D) and butane-1,4-diol (B₁D) using Pt catalysts doped with alkali metals was studied. These catalysts showed higher selectivity to the olefinic diol (B₂D) compared to that with monometallic platinum catalyst. Among various alkali metals, Cs-doped catalyst showed highest selectivity (>99%) to B₂D. The selectivity to B₂D increased (up to 99.9%) with increase in the concentration of Cs from 0.25% to 1%. The increase in the basic strength of alkali doped catalysts measured by CO₂-TPD, would be responsible for the increase in electron density of Pt hence, faster desorption and higher selectivity to the intermediate olefinic diol (B₂D). The reaction parameters, such as temperature, H₂ pressure and substrate concentration have strong influence on the catalyst activity but almost no effect on the selectivity to B₂D.     

Activity of Gold Catalysts in the Liquid-Phase Oxidation of O-Hydroxybenzyl Alcohol

Gold catalysts prepared by impregnation of HAuCl₄ on Fe₂O₃, ZnO, CaO, and Al₂O₃ and aged in a solution of Na₂CO₃ (IWI/Na₂CO₃ method) are able to catalyze the oxidation of o-hydroxybenzyl alcohol (salicylic alcohol) under mild conditions. The reaction rate is even higher than that using analogous catalysts prepared by co-precipitation. Salicylic aldehyde is the main reaction product with a selectivity >90% at 90% conversion. The influence of the reaction conditions on the catalytic activity is also discussed.     

4-OH-TEMPO radical grafted onto a novel polyaromatic ether sulfone containing carboxyl side chains as solid catalyst for alcohol oxidation

2,2,6,6-Tetramethylpiperidinium-nitroxide (TEMPO) is a mild and efficient catalyst, which is important in the industrial production of selective oxidation of alcohols to the corresponding aldehyde or ketone compounds. However, it is a challenge to recover the expensive TEMPO catalyst in homogeneous catalytic systems. In this study, a novel polymer-supported catalyst was prepared using 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxy (4-OH-TEMPO) and polyaromatic ether sulfone (PAES). The successful grafting of 4-OH-TEMPO in PAES-C was demonstrated by ¹H nuclear magnetic resonance (¹H NMR) and Fourier transform infrared (FT-IR), load capacity can be calculated by elemental analysis (EA). BET and scanning electron microscopy (SEM) to depict the structure-performance relationship. Herein, SEM images revealed the existence of porous structure. This structure can effectively adsorb NO molecules to form a PAES-TEMPO/NO_x catalytic system to selectively oxidize benzyl alcohol. The experimental results indicated the high activity, the subsequent benzyl alcohol oxidation cycle can reach more than 93% conversion without showing a large loss of selectivity. More importantly, the as-prepared catalyst exhibited the attractive recyclability (recovery rate is 98%). After 10 consecutive runs, no significant loss of conversion and selectivity was observed (the conversion rate of benzyl alcohol was more than 93% and the selectivity was more than 95%). This study might provide some recommendation on the development of highly efficient catalysts for alcohol oxidation.     

Methane oxidative coupling over promoted Pb/Ca catalysts

A series of Pb/Ca catalysts, promoted with Li, K and La, and prepared by different procedures, have been examined for the oxidative coupling of methane. The Li promoted Pb/Ca had the highest C₂ selectivity and yield of the catalysts studied, including the unpromoted Pb/Ca. For the Li/Pb/Ca catalyst, CO₂ added to the feed resulted in a decreased CH₄ conversion and an increased C₂ selectivity. Addition of H₂O to the feed with the same catalyst, increased C₂ yield. These effects are discussed in terms of deactivation and regeneration of the active sites by CO₂ and H₂O, respectively.     

The effects of mineral salt catalysts on selectivity of phenolic compounds in bio-oil during microwave pyrolysis of peanut shell

Catalytic microwave pyrolysis of peanut shell (PT) using Fe₃O₄, Na₂CO₃, NaOH, and KOH for production of phenolic-rich bio-oil was investigated. The effects of catalyst type, pyrolysis temperature, and biomass/catalyst ratio on product distribution and composition were studied. Among four catalysts tested, Na₂CO₃ significantly increased the selectivity of phenolic compounds in bio-oil during microwave pyrolysis. The highest phenolics concentration of 57.36% (area) was obtained at 500 °C and PT:Na₂CO₃ ratio of 8: 1. The catalytic effect to produce phenolic compounds among all the catalysts tested can be summarized in the order Na₂CO₃>Fe₃O₄>KOH>NaOH. Using KOH and NaOH as catalyst resulted in formation of bio-oil with enhanced higher heating value (HHV) and lower oxygen content, indicating that these catalysts enhanced the deoxygenation of bio-oil. The scanning-electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) analysis of char particles showed the melting of magnetite and vaporizationcondensation of mineral salt catalysts on char particle, which was attributed to extremely high local temperatures during microwave heating.     

Preparation of Titanium-Containing Carbon–Silica Composite Catalysts and Their Liquid-Phase Epoxidation Activity

Titanium-containing catalysts have been prepared by two different post-synthesis methods using activated carbon and carbon-silica composite as catalyst supports. They have been applied to the liquid-phase epoxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) and H₂O₂. The carbon-silica composite catalyst showed a high conversion and selectivity to epoxide compared to the Ti-carbon catalyst and silica-based catalysts for the cyclohexene epoxidation with H₂O₂. The highest values of cyclohexene conversion and epoxide selectivity were obtained with the carbon-silica composite catalyst having a titanium content of 3 wt%.