Liquid-phase esterification of methacrylic acid with methanol catalyzed by cation-exchange resin in a fixed bed reactor:Experimental and kinetic studies

The kinetic behavior of esterification between methacrylic acid and methanol catalyzed by NKC-9 resin was studied in a fixed bed reactor.The reaction was conducted in the temperature range of 323.15 to 368.15 K with the molar ratio of reactants from 0.8 to 1.4 under certain pressure.The measurement data were regression with the pseudo-homogeneous(P-H),Eley-Rideal(E-R),and Langmuir-Hinshelwood(L-H)heterogeneous kinetic models.Independent adsorption experiments were implemented to gain the adsorption equilibrium constants of four components.Among the above three models,the L-H model exhibited the best fitting results.The stability of NKC-9 was evaluated by long-term running with the yield of methyl methacrylate no decrease during 3000 h operation.The structure and physicochemical properties of the new and used catalyst were performed by several characterizations including thermogravimetric analysis(TG),scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)and so on.

In-situ generated ionic liquid catalyzed aldol condensation of trioxane with ester in mild homogeneous system

α, β-unsaturated esters were often synthesized from aldehydes and esters in the presence of strong organic base that was very sensitive to air and moisture via aldol reaction. Trioxane was very useful C1 resource, however, the decomposition of it was always the challenging problem that facing researchers. Herein, a novel synthetic methodology for α, β-unsaturated ester preparation from trioxane and ester with mild catalysis of generated ammonium trifluoromethanesulfonate ionic liquid. The enolization of ester as well as the decomposition of trioxane could proceed easily in the presence of boryl trifluoromethanesulfonate and amine at 20–25℃. Then the enolate and decomposed formaldehyde occurs aldol reaction to form α, β-unsaturated ester. With this strategy, the yield and selectivity of product from various substrates including aliphatic esters,lactones and thioester could reach up to 85.2% and 90.1%.

Ionic liquid catalyzed solvent-free synthesis of chalcone and its derivatives under mild conditions

An ionic liquid(IL)catalyzed solvent-free process was developed for the direct synthesis of chalcone and its derivatives by using substituted acetophenones and benzaldehydes via aldol reaction under mild conditions.A series of acidic and basic ILs were selected and screened.The influences of cations and reaction conditions on product yield and selectivity were systematically investigated.The[Bmim]OH was identified as the optimal IL,with the highest yield and selectivity reaching up to 96.7% and 100%,respectively.A reaction mechanism-based kinetic model was established and regressed with experimental data,revealing the β-Hydroxylketone dehydrolysis with activation barrier of 37.8 kJ·mol^(-1) was observed as the ratecontrolling step.

Comprehensive evaluation of an ionic liquid based deep purification process for NH_(3)-containing industrial gas

Ammonia(NH_(3))emission has caused serious environment issues and aroused worldwide concern.The emerging ionic liquid(IL)provides a greener way to efficiently capture NH_(3).This paper provides rigorous process simulation,optimization and assessment for a novel NH_(3)deep purification process using IL.The process was designed and investigated by simulation and optimization using ionic liquid[C_(4)im][NTF_(2)]as absorbent.Three objective functions,total purification cost(TPC),total process CO_(2)emission(TPCOE)and thermal efficiency(ηeff)were employed to optimize the absorption process.Process simulation and optimization results indicate that at same purification standard and recovery rate,the novel process can achieve lower cost and CO_(2)emission compared to benchmark process.After process optimization,the optimal functions can achieve 0.02726$/Nm~3(TPC),311.27 kg CO_(2)/hr(TP-COE),and 52.21%(ηeff)for enhanced process.Moreover,compared with conventional process,novel process could decrease over$3 million of purification cost and 10000 tons of CO_(2)emission during the life cycle.The results provide a novel strategy and guidance for deep purification of NH_(3)capture.

A novel kind of multiple steady states characteristics in the dividing wall column

In this article, one kind of multiple steady states(MSS) phenomenon was investigated for a dividing wall column(DWC). The four-section model constructed in Aspen Plus was employed to simulate two DWC cases: mixture of n-hexane, n-heptane and n-octane;system of methanol, ethanol and n-propanol. It can be seen that there is a range of vapor split ratio in which multiple solutions of reflux ratio exist for fixed DWC configuration with the same feed and product streams. The width and the curve shapes of the MSS region, and the number of solutions change with the liquid split ratio. This MSS phenomenon was further explained using the component recovery around the prefractionator and the component recycling flow inside the DWC. This MSS phenomenon is helpful for DWC design by knowing the probable existence of multiple solutions in advance.

Cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3)in Al_(2)O_(3)-AlPO_(4)for aldol condensation of methyl acetate with formaldehyde to methyl acrylate

The bare amorphous Al_(2)O_(3)-AlPO_(4)and Cs/Al_(2)O_(3)-AlPO_(4)catalysts were developed for the aldol condensation of methyl acetate with formaldehyde to methyl acrylate.The structure and property of catalyst were characterized by XRD,XPS,BET,Pyridine-IR,FT-IR,^(27)Al-MASNMR,NH_(3)-/CO_(2)-TPD and SEM.The correlation between structural features and acid-base properties was established,and the loading effect of the cesium species was investigated.Due to cooperative catalytic effects between the penta-coordinated Al and Al_(2)O_(3),the weak-Ⅱacid and medium acid site densities and the product selectivity were improved.While the basic site densities of these catalysts were almost in proportion to the conversion of methyl acetate.The loaded Cs could form new basic sites and change the distribution of acid sites which further enhance the catalytic performance.As a result,the 10Cs/8AlP was proved to be an optimal catalyst with the yield and selectivity of 21.2%and 85%for methyl acrylate respectively.During the reaction,a deactivation behavior was observed on 10Cs/8AlP catalyst due to the carbon deposition,however,it could be regenerated by thermal treatment in the air atmosphere at 400℃.

生物可降解离子液体预处理玉米秸秆

生物可降解的胆碱醋酸离子液体在玉米秸秆预处理过程中显示出高效的去木质素能力。通过该简单、无毒、绿色的工艺,可从离子液体-玉米秸秆溶液中,直接得到含综纤维素98.0%的富纤维产品,并且木质素含量从13.7%下降到2.0%。

温和条件下丙酸甲酯和甲醇一步合成甲基丙烯酸甲酯

近年来,由于煤化工行业产能过剩,煤基气相法一步合成甲基丙烯酸甲酯(MMA)工艺引起了研究者们的兴趣,但反应温度高、产物收率和选择性低、催化剂易积碳失活以及甲醛易挥发和聚合一度成为该研究领域的瓶颈问题.本文通过构建温和、高效的钴配合物催化借氢阻断体系,解决了甲醇脱氢生成甲醛、丙酸甲酯与甲醛羟醛缩合生成MMA以及氧气阻断MMA加氢相串联的难题,从而实现了以丙酸甲酯和甲醇为原料,在80℃下液相法一步合成MMA的新工艺,产物收率和选择性分别为25.7%和92.6%.通过核磁共振表征和动力学同位素效应实验验证了钴配合物催化剂活化与甲醇脱氢机理,并确定甲醇的C–H键活化与断裂为速率控制步骤,为煤基合成MMA提供了新的研究方向.

Effect of SiO_(2)/Al_(2)O_(3)ratio on the conversion of methanol to olefins over molecular sieve catalysts

A series of SAPO-34 molecular sieves with different SiO_(2)/Al_(2)O_(3)ratios have been synthesized for the methanol-to-olefin(MTO)reaction.Their physico-chemical properties are characterized by various techniques such as X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),Fourier transform infrared spectroscopy(FT-IR)and N2 adsorption-desorption.The results are compared with those of the commercial HZSM-5,which show that the crystallinity and particle diameter of SAPO-34 as well as HZSM-5 increase with SiO_(2)/Al_(2)O_(3)ratio.The variation of BET surface area of SAPO-34 is different from that of HZSM-5 and the sample with SiO_(2)/Al_(2)O_(3)ratio of 0.4 exhibits the highest BET surface area.FT-IR spectra indicate that HZSM-5 has both Brǿnsted and Lewis acid sites and Brǿnsted acid sites are stronger,whereas SAPO-34 samples are dominated only by Lewis acid sites.When the SiO_(2)/Al_(2)O_(3)ratio increases,propylene and butylenes become the predominant product of the MTO reaction over HZSM-5.In contrast,the main products of this reaction catalyzed by SAPO-34 are ethylene and propylene.According to the product distribution,the reaction mechanism over HZSM-5 catalysts is proposed.