生物原油炼制： 副产物内循环及水热自催化

利用高温高压条件模拟石油生成的生物质水热液化技术可用于制备生物原油,以替代日益枯竭的石油资源,然而副产物处置问题制约了其可持续发展。解决该问题的方法首先是通过水热定向催化调控减少副产物,然后集成各种技术将副产物尽可能原位资源化。基于此并依据生物炼制的思想,本文对一种集成几种水热技术炼制生物原油的模式进行了讨论。依据生物质水热液化副产物的特性,通过对固体产物水热合成制备催化剂、水相产物回用产生有机酸、气体产物分离或彻底氧化后水热还原生产有机酸等,可实现副产物内循环并强化自催化生成生物原油。指出该模式符合绿色化工的理念,对于加快规模化生产可替代石油的生物原油、缓解能源危机具有重要的参考意义。     

Asymmetric Autocatalysis Triggered by Chiral Crystals Formed from Achiral Compounds and Chiral Isotopomers

Asymmetric autocatalysis with amplification of enantiomeric excess is found in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde using pyrimidyl alkanol as an asymmetric autocatalyst. Asymmetric autocatalysis has been employed as a method for clarifying the origin of homochirality. Circularly polarized light, inorganic chiral crystals and statistical fluctuation of enantiomeric imbalance act as chiral initiators in asymmetric autocatalysis to afford highly enantioenriched products. We have investigated asymmetric autocatalysis using chiral crystals formed from achiral and racemic compounds as an origin of chirality. Absolute control of the crystal chirality of cytosine was achieved by the removal of crystal water. Enantioselective carbon-carbon bond formation at the enantiotopic crystal face of aldehydes was established using diisopropylzinc vapor. In addition, asymmetric autocatalysis triggered by chiral compounds arising from H, C and O isotope substitution has been achieved.     

Kinetic modeling of hemicellulose hydrolysis in the presence of homogeneous and heterogeneous catalysts

Kinetic models were developed for the hydrolysis of O‐acetyl‐galactoglucomannan (GGM), a hemicellulose appearing in coniferous trees. Homogeneous and heterogeneous acid catalysts hydrolyze GGM at about 90°C to the monomeric sugars galactose, glucose, and mannose. In the presence of homogeneous catalysts, such as HCl, H₂SO₄, oxalic acid, and trifluoroacetic acid, the hydrolysis process shows a regular kinetic behavior, while a prominent autocatalytic effect was observed in the presence of heterogeneous cation‐exchange catalysts, Amberlyst 15 and Smopex 101. The kinetic models proposed were based on the reactivities of the nonhydrolyzed sugar units and the increase of the rate constant (for heterogeneous catalysts) as the reaction progresses and the degree of polymerization decreases. General kinetic models were derived and special cases of them were considered in detail, by deriving analytical solutions for product distributions. The kinetic parameters, describing the autocatalytic effect were determined by nonlinear regression analysis. The kinetic model described very well the overall kinetics, as well as the product distribution in the hydrolysis of water soluble GGM by homogeneous and heterogeneous catalysts. The modelling principles developed in the work can be in principle applied to hydrolysis of similar hemicelluloses as well as starch and cellulose. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1066–1077, 2014     

自催化生化反应系统中的极限环

本文研究一类描述自催化生化反应系统的微分方程数学模型。文章从理论上讨论了极限环的存在性问题，给出了存在极限环的充分条件，同时给出了一个存在极限环的具体的例。     

The evolution of travelling waves from chemical-clock reactions

A clock-reaction is a chemical reaction which gives rise to an initial induction period before a significant change in concentration of one of the chemical species occurs. In this paper the development of travelling waves from a particular class of inhibited autocatalytic clock-reactions is analysed. The numerical solutions show that, after the induction period, a propagating reaction-diffusion front is initiated. This front is seen to accelerate initially and then to become a constant-speed travelling wave. An asymptotic analysis of the large-time travelling-wave behaviour is given and from this it is possible to fix a minimum wave speed. The asymptotic predictions of the wave speed are found to agree well with those of the numerical solution.     

Quartic autocatalysis of homogeneous and heterogeneous reactions in the bioconvective flow of radiating micropolar nanofluid between parallel plates

This study deals with the quartic autocatalysis of homogeneous–heterogeneous chemical reaction that occurs in the bioconvective flow of micropolar nanofluid between two horizontally parallel plates. The quartic autocatalysis is found to be more effective than cubic autocatalysis since the concentration of the homogeneous species is substantially high. The upper plate is assumed to be in motion and the lower plate is kept stationary. Such a flow of micropolar fluid finds application in the pharmaceutical industry, microbial enhanced oil recovery, hydrodynamical machines, chemical processing, and so forth. The governing equations for this flow are in the form of the partial differential equation and their corresponding similarity transformation is obtained through Lie group analysis. The governing equations are further transformed to coupled nonlinear differential equations that are linearized through the Successive linearization method and are solved using the Chebyshev Collocation method. The effects of various parameters, such as micropolar coupling parameter, spin gradient parameter, reaction rates, and so forth, are analyzed. It is observed that the fluid flows with a greater velocity away from the channel walls, whereas near the channel walls the velocity decreases with an increase in the coupling parameter. Furthermore, the spin parameter increases the spin gradient viscosity that reduces the microrotation of particles that further decreases the microrotation profile.     

On the Chiral Homogeneity of Nature: From Atoms to Small Molecules

The genesis of enantiopurity in nature, as exemplified by terrestrial amino acids and sugars, has fascinated scientists for more than 150 years. This is a field where we know what we do not know. Starting from theoretical treatments postulated more than 50 years ago, numerous hypotheses, theories, and experiments have been formulated to claim niches of logic and truth. Such arguments vary from purely speculative, often bizarre, to sound enough in terms of reproducibility and feasible generation of mirror symmetry breaking. Although we cannot exclude a biotic origin (i.e,. homochirality was an a posteriori event where one enantiomer tripped and the other survived and evolved, in close resemblance to a Darwinian-like process), most data and models available are consistent with an abiotic origin that amplified small and stochastic imbalances to produce enantiopure homogeneity prior to life. This analysis revisits recent theoretical background and experiments, which appear to be prebiotically credible, and focuses on primordial molecules such as amino acids. This by no means implies a recreation of the origin of life on Earth, as this task will likely be a surmise forever. These strategies reveal a high degree of robustness and prove how home-made enantiopurity can be accomplished. Such routes should, in addition, be of enormous practical interest for the production of chiral materials and drugs.     

Kinetic instabilities in man-made and natural reactors

Kinetic instabilities and self-organization phenomena in chemical and biological systems are reviewed and discussed from the point of view of the unified qualitative theory of non-equilibrium processes.     

基于数值计算方法计算最大反应速率到达时间

最大反应速率到达时间(TMR_ad)是化工工艺热风险评估中一个十分重要的参数。一般计算TMR_ad的方法是基于N级模型的分析。但对于复杂的反应过程统一采用N级模型分析计算可能会引起较大偏差甚至得到错误的评估。因此,提出运用基于反应类型的数值计算方法进行TMR_ad和T_D24的评估,通过分别代表N级反应和自催化反应的20% DTBP甲苯溶液和CHP的ARC测试分析表明：对于N级反应,该方法能可靠地用于TMR_ad和T_D24的求取;而对于自催化反应,尽管拟合效果很好,原有方法计算偏差很大,原因是不同模型下动力学参数不同,还进行偏差大小分析。由此可知该数值计算方法有广泛的适用性,对于放热曲线,需在了解其反应类型的基础上利用该方法进行TMR_ad和T_D24的评估,由此评估的结果更为可靠准确。     

How Catalytic Order Drives the Complexification of Molecular Replication Networks

Catalytic replication networks have frequently served to study emergent phenomena in complex mixtures. In a series of recent research papers, we have analyzed the effects of the autocatalytic reaction order on various behaviors of these networks, and in particular, on their possibility to evolve and mimic functions often observed in cell biochemistry. In this review, we first discuss and derive properties of minimal self-replication, with an emphasis on catalytic order, reaction order, and properties directly affected by the order. We then expand our discussion to include catalytic networks, and review some of the implications of symmetry and order in these networks. Consequently, we look at open catalytic networks and their oscillations in replication product formation, again emphasizing the critical role played by the catalytic order. Finally, we describe an extension of the catalytic networks research using the quasispecies model, where we note the implications of the order on the phase transitions observed in these systems. Further implications of these results for emergence and evolution are discussed.