调控铝在ITH沸石骨架中的位置以用于催化甲醇制烯烃

随着低碳烯烃需求量的增加,甲醇制烯烃(MTO)成为由非石油资源制取低碳烯烃的关键技术,其中沸石由于具有可调节的酸度、有序的微孔结构和较好的择型性能而被广泛用作MTO反应催化剂.ITQ-13沸石(ITH拓扑结构)由于其独特的九元环结构在MTO反应中表现出较好的丙烯选择性和反应寿命,引起了广泛关注.研究表明,分子筛的酸中心分布与MTO反应性能密切相关,因此,研究ITQ-13沸石中铝分布与MTO反应性能的关系,对进一步提升其MTO催化性能具有重要意义.本文分别以与ITH具有共同基本结构单元(双四元环,D4Rs)的LTA沸石(LTA-ITH)和薄水铝石(C-ITH)为铝源,合成了两类铝硅酸盐ITH沸石.X射线衍射、扫描电子显微镜以及氮气吸脱附表征结果表明,这两类分子筛具有相似的片状形貌和微孔性质.氨气程序升温脱附结果表明,具有相近硅铝比的两类ITH沸石具有相近的酸量.进一步采用27Al魔角旋转核磁共振(MAS NMR)、密度泛函理论计算和1-己烯裂解反应对两类ITH分子筛的铝分布进行研究.结果表明,两类分子筛具有不同的铝分布,LTA-ITH中有更多的铝进入ITH的正弦孔道与直孔道,而C-ITH中有更多的铝分布在交叉孔道.当前,研究者普遍认为MTO反应过程遵循双循环烃池机理,ITH交叉孔道由于具有较大的空间,相比于正弦孔道和直孔道,更有利于芳烃循环中间体的产生,从而有利于形成芳烃循环产物(乙烯),而正弦孔道和直孔道却更有利于烯烃循环过程,导致产生更多的丙烯.对两类ITH进行了MTO催化性能测试,结果表明,LTA-ITH比C-ITH表现出更高的丙烯选择性,并且表现出更高的丙烯与乙烯的比率,表明其烯烃循环过程得到加强,这与^(27)Al MAS NMR以及1-己烯裂解反应得到的结论一致,进一步证明ITH分子筛的铝分布得到有效调控.综上,本文阐明了ITH沸石中铝分布与其反应性能的关系,为调整沸石骨架中的Al位点提供一种新策略,为未来制备高效的MTO沸石基催化剂提供参考.

利用择形分子筛异构化亚甲基二苯胺

亚甲基二苯胺(MDA)被广泛用作生产聚氨酯和聚异氰脲酸酯的中间体.然而,当前MDA的生产工艺在控制(4,4’/(2,4’+2,2’))异构体比例方面还存在局限.其中,4,4’-MDA被认为是最有价值的异构体.尽管2,4'-MDA在市场上也有一定的需求,但如果能将其有效地转化为4,4'-MDA,将能显著提升其附加值.本文在使用苯胺的条件下,利用β分子筛等催化剂,通过双分子机制,可以选择性地将2,4'-MDA异构化为4,4'-MDA.尽管实验显示,多种酸性沸石具有较高的异构化活性,但MCM-68(具有MSE拓扑结构)的催化性能尤为出色,它不仅展现出高异构化活性,而且具有很好的选择性.MCM-68主要催化2,4'-MDA异构化为4,4'-MDA,而2,2'-MDA和低聚物的形成则可以忽略不计.本文还深入探讨了该择形作用的原因,并详细研究了酸位置在MSE分子筛孔道限制中的关键作用.

Selective conversion of syngas to propane over ZnCrO_x-SSZ-39 OX-ZEO catalysts

Oxide-Zeolite(OX-ZEO) bifunctional catalyst design concept has been exemplified in several processes to direct conversion syngas to value-added chemicals and fuels such as mixed light olefins, ethylene, aromatics and gasoline.Herein we demonstrate that the product can be steered toward liquefied petroleum gas(LPG) with a selectivity up to 89% in hydrocarbons especially propane selectivity reaching 80% at CO conversion of 63% using ZnCrOx-H-SSZ-39 catalyst.Interestingly, the quantity of the acid sites of SSZ-39 does not influence obviously the hydrocarbon distribution but the strength is crucial for selective formation of propane.This finding provides an alternative route of LPG synthesis from a variety of carbon resources via syngas.

Emerging R&D on membranes and systems for water reuse and desalination

Sustainable production of clean water is a global challenge.While we firmly believe that membrane technologies are one of the most promising solutions to tackle the global water challenges,one must reduce their energy consumption and fouling propensity for broad sustainable applications.In addition,different membranes face various challenges in their specific applications during long-term operations.In this short review,we will summarize the recent progresses in emerging membrane technologies and system integration to advance and sustain water reuse and desalination with discussion on their challenges and perspectives.

New High Viscosity Ester Base Stocks for Superior Lubricant Formulations

BASF presents a new high viscosity ester base stock technology.Viscosity profiles of these new candidates are comparable to market-known high viscosity PAO types such as PAO 40 and PAO 100.Due to the more polar nature of the new ester base stocks additional benefits can be achieved in terms of friction reduction,energy efficiency or facilitated additive solubilisation against high viscosity PAOs.The superior performance of the new high viscosity ester base stock technology is demonstrated in direct comparison against high viscosity PAO counterparts in industrial gear applications.The basic advantages found herein in industrial gear applications are also of relevance for other lubricant applications such as automotive driveline oil or engine oil applications.As one exemplary area industrial gear applications play a dominant role in modern wind turbines.The latest generation of lubricants used in these turbine gear boxes are required to provide a greater performance in terms of wear protection,durability,foam resistance,shear stability,and oxidation resistance.Common formulations are based on a PAO base stock thickened with high molecular weight PAO polymers to achieve a viscosity of ISO 320 combined with additives to provide wear protection,foam resistance etc.A recent plant outage coupled with high demand for high molecular weight PAO polymers has led to the market becoming aware of potential availability issues.In response to this important challenge BASF has developed a new formulation strategy-based on the new high viscosity ester technology and upon a widely available low molecular weight PAO base stock employing a new concept in a thickening system that avoids the use of high molecular weight PAO polymers.The novel ester base stock can be manufactured at multiple locations and is based on sustainable raw materials that can be sourced from a wide supplier base.

巴斯夫9%吡唑醚菌酯微囊悬浮剂技术特点分析

9%吡唑醚菌酯微囊悬浮剂(稻清~?)是巴斯夫公司研制的一种将吡唑醚菌酯专用于防治水稻病害,并显著降低其对水生生物潜在影响的创新剂型产品。该剂型可以将吡唑醚菌酯在植物表面的迅速释放与胶囊在水中的稳定性完美的结合,这点通常是常规微囊悬浮剂型所无法达到的。有了这种双重特性,稻清~?可以提供优异的杀菌效果和植物健康功效(通过对植物生理效应的影响提高作物的产量和品质),并能显著降低对水生生物的毒性。为了印证这种特殊微囊悬浮剂型在水稻田中使用的安全性,巴斯夫公司进行了一系列不仅限于法规登记要求的深度研究,其涵盖了对水生生物影响的实验室研究,水稻半田间试验,以及水稻田环境监测试验等。

MAPPING THE DAMAGED ZONE AROUND THE CRACK TIP IN HIGH DENSITY POLYETHYLENE WITH SYNCHROTRON MICROFOCUS SMALL ANGLE X-RAY SCATTERING TECHNIQUE

The structural changes around a crack tip in a high density polyethylene were investigated by means of scanning synchrotron microfocus small-angle X-ray scattering technique. The scattering data confirm the process of craze structure development near a crack tip based on the evolution of voids. In addition, it was found that the main stress in the plastic zone near a crack tip exhibited a gradient distribution with respect to its strength and direction. The whole damaged area showed a strain distribution indicating a flow behavior toward the crack tip.

Industrial Outlook on Zeolites and Metal Organic Frameworks

水晶的 nanoporous 材料在工业化学服务众多的枢轴的功能。他们为工业应用程序提供关键特征，例如高表面区域，一致的孔，互连的毛孔 / 隧道系统，可存取的毛孔卷，高吸附能力，离子交换能力，提高的催化活动，和形状 / 尺寸选择。作为 nanoporous 材料的一个生长得很好的家庭，沸石具有为化学、石油化学的工业的重要重要性。多孔的材料的一个新兴的班叫了器官的框架(MOF ) 也在各种各样的应用为诺言提供的金属。沸石和 MOF 能在为我们的工业化社会的未来是批评的地里起重要作用。在为原料变化的探索，沸石用作向基础化学药品提供要求的形状 / 尺寸选择的催化剂。在转移进象氢那样的另外的交通燃料的全球努力， MOF 用作精力存储媒介。在对环境污染的战斗，沸石不仅参加有害物质的俘获和消退，而且为许多工业过程提供环境地良性的选择。在这评论，为现在和将来的应用的沸石和 MOF 的合成和利用上的一个工业观点被介绍。

非离子表面活性剂与膜材料的兼容性及对膜的清洗研究

当工业膜在工业生产(比如海水脱盐淡化、乳制品和饮料工业)中应用时,经常不可避免地面临着由于污染所带来的膜分离效率的降低、流通不畅等问题。为了保障膜的高流通性,需要经常进行膜的清洗。其中无机物主要通过酸洗去除,有机物则用表面活性剂在碱性条件下去除。当前,使用最广泛的表面活性剂主要是离子表面活性剂或烷基酚乙氧基化物,而对于其他非离子表面活性剂,由于传统认为它们会不可逆地吸附在膜的薄膜堵塞孔道,不适合用作膜的清洗剂。通过对各种非离子表面活性剂在膜材料上的吸附实验研究,我们发现非离子表面活性剂对膜的亲和力主要取决于它们的分子结构。直链烷基乙氧基化物在膜表面极易发生不可逆吸附,而支链结构的乙氧基化物则不会。与吸附实验的结果相似,各种非离子表面活性剂对膜的清洗效果也与它们的分子结构有关,支链烷基乙氧基化物往往表现出更强的清洗能力。将非离子表面活性剂与螯合剂、酶混合使用可以显著提高对膜的清洗效率,特别是被细菌污染的薄膜。

CHARACTERIZATION OF NANOSTRUCTURES:TOOLS AND CHALLENGES

Apart from long-known and applied nanostructures like carbon black for tyres or pigments for coatings nanotechnology has created highly sophisticated structures used for nano/molecular electronics,diagnostics,drug delivery, UV-absorbers etc.Often the main question to be solved analytically is the local determination of tiny amounts of chemicals resulting in an ever increasing need for highly sensitive as well as locally resolved techniques.Applications of techniques like mass spectroscopy,transmission elect...

MFI/MEL分子筛催化甲醇制烯烃反应关键参数的集成方法

了解与关键催化性能参数(如选择性和稳定性)相关的催化剂特性对于合理设计催化剂是非常重要的.本文重点考察了甲醇制烯烃(MTO)过程中MFI、MEL及其共生沸石分子筛的催化行为和构效关系.表征结果表明,丙烯和丁烯的高产率和MeOH的高转化率均与Pentasil分子筛结构中晶格Al位的富集相关,这也被27Al MAS NMR结果和3-甲基戊烷裂解结果证实.催化剂对MTO反应的催化性能与其晶体尺寸、外部B酸中心和铝配对等性质之间缺乏相关性,表明它们对提高丙烯选择性的作用不大.本文分析表明,催化剂失活非常复杂,受交叉点处晶格铝富集、总铝含量和晶体尺寸影响较大,且MFI和MEL相共生加速了催化剂失活.

Towards greener polymers:Trends in the German chemical industry

Global plastics production is expected to exceed 400 million tons and reach 600 million tons by 2060.Their synthesis currently accounts for approximately 3%of global greenhouse gas emissions.Approximately 60%of all polymers are produced for single-use.Examples include shopping bags,packaging materials,mulch films,and soluble polymers for cosmetics and other purposes.Currently,only a portion of single-use plastic is recycled or disposed of in incinerators or landfills.An estimated 20%is not disposed of properly and pollutes the global environment,especially the oceans.In response to these challenges,the United Nations,European Union,and many nation-states are developing regulatory frameworks that encourage the chemical industry to produce plastics with a smaller environmental footprint and often support this through research funding.Possible solutions include:(1)the use of green energy,green hydrogen,bio-based feedstocks,or CO_(2) in synthesis;(2)the reuse or recycling of plastics through conversion or pyrolysis;and(3)the production of biodegradable polymers.The German chemical industry contributes approximately one-third of polymer production in the EU.It is embedded in the EU regulatory and research landscape and anchored in the European Green Deal,which aims for carbon neutrality by 2050.In this paper,we describe how BASF and Evonik,two leading German chemical companies with strong but different polymer portfolios,respond to the call for greener polymers and how technologies are being developed to make polyurethanes,a particularly important and difficult-to-recycle family of elastomers and duromers,renewable and circular.Reducing the environmental footprint of plastics requires not only innovative materials but also proper governance,regulatory and collection systems,and public willingness to cooperate.In an international comparison of these competencies,expressed by the"polymer management index"(PMI),Germany achieved a top position.

Segregation of particulate solids: Experiments and DEM simulations

Segregation of granular materials is a complex phenomenon, difficult to measure quantitatively and to predict. Discrete element method （DEM） can be a useful tool to predict segregation effects and to support the industrial design. In this context, a very challenging idea is the characterization of the granular solids to provide the key parameters needed for a successful DEM simulation of segregation processes. Rolling friction, sliding friction and the coefficient of restitution are the critical parameters to be studied. These microscopic simulation parameters are calibrated by comparing the macroscopic behavior of granular matter in standard bulk experiments, which have the advantage of being highly repeatable and reliable. An experimental method is presented to characterize free surface segregation. The effects of different particle properties, particularly, shape and size, on segregation of cohesionless materials were investi- gated. From the experiments, particle size demonstrated a stronger effect on segregation than particle shape. Finally, the corresponding DEM simulations of the segregation experiments were presented. The parameters obtained by calibration were validated by the comparison of the modeled segregation behav- ior with the experimental results. Thus, calibrated DEM simulations are capable of predicting segregation effects.

The flow of non-starch polysaccharides along the gastrointestinal tract of broiler chickens fed either a wheat-or maize-based diet

The present study characterised the types and amounts of non-starch polysaccharides(NSP)remaining undigested along the gastrointestinal tract(GIT)of broiler chickens offered a typical wheat-or maizebased diet.One-day old Cobb 500 mixed-sex chicks were assigned to 24 pens,with 10 birds/pen and 12 pens/treatment.Birds were offered the experimental diets in 3 phases(starter,day 0 to 10;grower,day 11 to 24 and finisher,day 25 to 35).Excreta and digesta samples from the crop,gizzard,duodenum,jejunum,ileum and caeca were collected at 12 and 35 days of age,and analysed for the NSP flow.The wheat-based diet contained higher levels of soluble NSP than the maize-based diet,whereas insoluble NSP levels were similar between the 2 diets.Detailed analysis of NSP constituents revealed that arabinoxylans were the primary NSP in the wheat-based diet,mostly in insoluble form.Pectins were the predominant NSP in the maize-based diet,followed by arabinoxylans.Overall,birds offered the wheatbased diet presented higher levels of soluble NSP remaining in all gut sections compared to birds offered the maize-based diet,at both 12 and 35 days of age(P<0.050).Accumulation of insoluble NSP in the gizzard was noted in birds fed both diets,but was more pronounced in birds offered the maize-based diet compared to the wheat-based diet,at both 12 and 35 days of age(P<0.001).The present study highlights marked differences in the amounts and types of NSP delivered to the different gut sections when feeding wheat-compared to maize-based diets,particularly in the gizzard and the lower GIT of birds.

The effect of hydrogen bond acceptor properties of ionic liquids on their cellulose solubility

It is nowadays well-known that ionic liquids can dissolve cellulose. However, little systematic data has been published that shed light onto the influence of the ionic liquid structure on the dissolution of cellulose. We have conducted 1H NMR spectroscopy of ethanol in a large number of ionic liquids, and found an excellent correlation of the data obtained with the hydrogen acceptor properties (β-values). With this tool in hand, it is possible to distinguish between cellulose-dissolving and non-dissolving ionic liquids. A modulating effect of both, the anion of the non-dissolving ionic liquid and its cation was found in solubility studies with binary ionic liquid mixtures. The study was extended to other non-dissolving liquids, namely water and dimethylsulfoxide, and the effect of the cation was also investigated.

Characterisation of undigested components throughout the gastrointestinal tract of broiler chickens fed either a wheat-or maizebased diet

This study was to characterise the undigested nutrients present along the gastrointestinal tract of birds offered common wheat-or maize-based diets,with the goal of optimising utilisation of enzymes to enhance digestive efficiency.Wheat-and maize-based diets were offered to 240 mixed-sex broilers(10 birds/pen;n=12)from 1 to 35 d postehatch.Digestibility of dry matter,starch,crude protein and nonstarch polysaccharides(NSP)were measured in the crop,gizzard,duodenum,jejunum,ileum,caeca and excreta at d 12 and 35 postehatch.Analysis of nutrient levels in the excreta presented that more than 30%of nutrients provided in the feed was wasted,irrespective of wheat or maize diet type.On average,92 g/kg crude protein,92 g/kg insoluble NSP and 14 g/kg oligosaccharides were not utilised by birds at d 12 postehatch.The quantity of water-insoluble NSP in the small intestine at d 12 was lower in birds offered the wheat-based diet compared to those fed the maize-based diet(P<0.05),with the reverse being true for water-soluble NSP(P<0.001).On average,84 g/kg crude protein,79 g/kg insoluble NSP and 9 g/kg oligosaccharides remained in the excreta at 35 d of age.At this time period,accumulation of feed in the gizzard was noted for birds offered both diets,but was more pronounced in those offered the maize-based diet(P<0.001).Birds offered the maize-based diet demonstrated improved utilisation of oligosaccharides compared to those fed the wheat-based diet at both d 12 and 35(P=0.087 and P=0.047,respectively).Protein utilisation in the jejunum and ileum was greater in birds offered the wheat-based diet compared to those fed the maize-based diet(P=0.004 and P<0.001,respectively).Thus,while both diets supported standard growth performance of birds,the degree and flow of nutrient disappearance along the gastrointestinal tract was influenced by cereal type and bird age.

Non-starch polysaccharide-degrading enzymes may improve performance when included in wheat- but not maize-based diets fed to broiler chickens under subclinical necrotic enteritis challenge

The present study investigated whether supplementing fibre-degrading enzymes can ameliorate the severity of subclinical necrotic enteritis(NE)in broiler chickens offered wheat-or maize-based diets.A total of 1,544 mixed-sex broiler chickens were assigned to 16 experimental treatments as a 2×2×4 factorial arrangement of treatments.The factors were the following:NE challenge,yes or no;diet type,wheat-or maize-based;and enzyme supplementation,control(no enzyme),family 10 xylanase(XYN10),family 11 xylanase(XYN11)or b-mannanase(MAN).Each treatment was replicated 6 times,with 16 birds per replicate pen.A three-way challenge×diet type×enzyme interaction occurred for body weight at 21 d of age(P=0.025)and overall feed conversion ratio(P=0.001).In the non-challenged birds fed the wheat-based diet,supplementing MAN increased d 21 body weight compared to the control.In challenged birds fed the maize-based diet,supplemental XYN11 impeded body weight and overall FCR compared to the control.Birds offered the maize-based diet presented heavier relative gizzard weights at both 16 and 21 d of age(P<0.001)and reduced liveability(P=0.046)compared to those fed the wheatbased diet.Enzyme supplementation reduced ileal and jejunal digesta viscosity at 16 d of age only in birds fed the wheat-based diet(P<0.001).XYN11 increased ileal digesta viscosity in birds fed the maizebased diet,and MAN reduced it in birds fed the wheat-based diet at 21 d of age(P=0.030).Supplementing XYN11 improved ileal soluble non-starch polysaccharides(NSP)digestibility in birds fed the wheat-based diet compared to non-supplemented birds(P<0.001).Birds fed the wheat-based diet displayed a higher abundance of Bifidobacterium,Lactobacillus and Enterobacteriaceae and butyric acid in the caeca at 16 d of age compared to birds fed the maize-based diet(P<0.05).In conclusion,supplemental XYN11 exacerbated the negative impact of NE on growth performance in birds fed the maizebased diet.Supplementing wheat-based diets with fibre-degrading enzymes ameliorates production losses induced by NE.

Ileal profile of non-starch polysaccharides and oligosaccharides in response to exogenous enzymes in broiler chickens offered wheat-or maize-based diets under subclinical necrotic enteritis challenge

The present study evaluated the impacts of fibre-degrading enzymes on the profiles of non-starch polysaccharides(NSP)and oligosaccharides(OS)in the ileum of broiler chickens offered wheat-or maize-based diets under subclinical necrotic enteritis(NE)challenge.A 224 factorial arrangement of treatments was used.Factors were the following:NE challenge,no or yes;diet type,wheat-or maizebased;and supplemental enzymes,control(no enzyme),family 10 xylanase(XYN10),family 11 xylanase(XYN11)or b-mannanase(MAN).Birds in the challenged group were inoculated with Eimeria on d 9 and Clostridium perfringens on d 14 and 15.A 3-way interaction(P=0.047)occurred on overall(d 0 to 16)weight gain.When NE was present,all the supplemental enzymes increased weight gain in birds fed the wheat-based diet;whereas in those fed the maize-based diet supplemental XYN10 and XYN11 decreased weight gain.When NE was absent,birds fed the wheat-based diet supplemented with XYN10 or MAN presented increased weight gain compared to non-supplemented birds,but no improvements with enzyme addition were observed in birds fed the maize-based diet.A 3-way interaction(P=0.002)was observed on insoluble NSP level in the ileum.When NE was absent,all the supplemental enzymes reduced the ileal level of insoluble NSP,regardless of diet type.In the challenged birds,supplementing XYN10 and MAN reduced insoluble NSP level in the ileum,but only in birds fed the wheat-based diet.Ileal soluble NSP level was reduced by supplemental XYN11 and MAN,but only in birds fed the wheatbased diet,resulting in a 2-way diet typeenzyme interaction(P<0.001).Ileal OS arabinose(P=0.030)level was highest in birds offered the wheat-based diet supplemented with XYN11.Collectively,supplementation of NSP-degrading enzymes to the wheat-based diet enhanced bird performance regardless of NE challenge,with XYN11 significantly increasing oligosaccharide release.However,enzyme addition did not improve growth performance in birds fed maize-based diet,with supplemental XYN10 and XYN11 impeding weight gain when NE was present.

Deep convolutional neural network for damaged vegetation segmentation from RGB images based on virtual NIR-channel estimation

Performing accurate and automated semantic segmentation of vegetation is a first algorithmic step towards more complex models that can extract accurate biological information on crop health,weed presence and phenological state,among others.Traditionally,models based on normalized difference vegetation index(NDVI),near infrared channel(NIR)or RGB have been a good indicator of vegetation presence.However,these methods are not suitable for accurately segmenting vegetation showing damage,which precludes their use for downstream phenotyping algorithms.In this paper,we propose a comprehensive method for robust vegetation segmentation in RGB images that can cope with damaged vegetation.The method consists of a first regression convolutional neural network to estimate a virtual NIR channel from an RGB image.Second,we compute two newly proposed vegetation indices from this estimated virtual NIR:the infrared-dark channel subtraction(IDCS)and infrared-dark channel ratio(IDCR)indices.Finally,both the RGB image and the estimated indices are fed into a semantic segmentation deep convolutional neural network to train a model to segment vegetation regardless of damage or condition.The model was tested on 84 plots containing thirteen vegetation species showing different degrees of damage and acquired over 28 days.The results show that the best segmentation is obtained when the input image is augmented with the proposed virtual NIR channel(F1=0:94)and with the proposed IDCR and IDCS vegetation indices(F1=0:95)derived from the estimated NIR channel,while the use of only the image or RGB indices lead to inferior performance(RGB(F1=0:90)NIR(F1=0:82)or NDVI(F1=0:89)channel).The proposed method provides an end-to-end land cover map segmentation method directly from simple RGB images and has been successfully validated in real field conditions.

CO_(2)微气泡强化纳米碳酸钙的制备及传递-反应分析

控制碳酸钙的粒径大小和粒径分布是碳化法制备高质量纳米碳酸钙的关键。采用间歇鼓泡碳化法制备纳米碳酸钙,考察了操作参数(气体流量、初始浆料浓度)、气泡类型(普通气泡、微气泡)对碳酸化反应速率和沉淀碳酸钙的粒径大小及分布的影响规律,同时深入分析了反应过程中稳定区和突变区随气泡类型的变化规律。结果表明,在使用普通气泡时,增加二氧化碳气体流量有利于二氧化碳的吸收和碳酸钙粒径的减小;在小塔中使用普通气泡,随着初始浆料浓度增加,在低浓度下,减小碳酸钙粒径,当浓度升高到一定程度后,对反应时长和物质混合的影响会促进晶体增长,使碳酸钙粒径增加。采用微气泡后会显著减小沉淀碳酸钙的粒径,同时,二氧化碳气体流量不再影响碳酸钙的粒径分布,表明气液传质过程不再是控制步骤。