促溶剂法制备光皮树油生物柴油研究

以光皮树油和甲醇为原料制备生物柴油,以丁酮作促溶剂,KOH做催化剂,考察反应时间、温度、催化剂、甲醇与油脂摩尔比对光皮树油转化为生物柴油得率的影响。得到光皮树油制备生物柴油的工艺条件:醇油摩尔比为6,温度65℃,催化剂为油脂质量的0.8%,反应时间为8 min,精制生物柴油得率为96%。     

萃取-酯交换耦合法制备生物柴油过程催化剂应用研究进展

传统的生物柴油生产过程通常包括油脂提取、提纯精炼、酯化/酯交换等步骤,需要消耗大量的能源与化学品。萃取-酯交换耦合技术是近年来开发的一种简单有效、具有较大应用潜力的生物柴油制备方法,该方法直接以含油固体为原料,以短链醇等作为萃取溶剂和酯交换反应试剂,油脂萃取与酯化/酯交换反应同时进行,提高了生产效率,降低了生产成本,减少了环境污染。萃取-酯交换耦合法中催化剂的选择是反应能否实现高效转化的关键。酯交换反应的催化剂种类繁多,但大多数针对的原料是浸提过的液体油脂,较少用来催化固体原料原位酯交换反应。笔者综述了近年来萃取-酯交换耦合技术制备生物柴油的研究进展,包括酸催化法、碱催化法、离子液体催化法、超临界法和生物酶法,探讨了各种方法的优缺点,同时提出了萃取-酯交换耦合法制备生物柴油过程中催化剂制备与应用方面需要解决的主要问题及今后的发展方向。     

油茶籽残饼油制备生物柴油研究及工艺优化

研究了油茶籽残饼油制备生物柴油碱催化酯交换反应动力学过程,探索了反应动力学因素醇油物质的量比、催化剂用量、反应温度和反应时间对生物柴油得率的影响.正交试验结果表明,油茶籽残饼油酯交换反应的理想条件为:反应温度70℃,醇油物质的量比为6:1,催化剂用量为油质量的0.6%,反应时间90 min;此条件下生物柴油得率为94.43%.经权威机构检测,所制得生物柴油主要性能指标完全符合国家标准GB/T 20828-2007,具有广阔的应用前景.     

静态混合管式反应器连续化制备生物柴油的动力学研究

以棉籽油和甲醇为原料,利用自制的静态混合管式反应器,在催化剂和共溶剂的共同参与下连续化制备生物柴油,研究其反应动力学。当催化剂KOH用量为油脂质量的0.6%,甲醇和棉籽油物质的量之比(醇油比)为28∶1,共溶剂丁酮与油脂体积比为1.5∶1,反应温度分别为45、50、55、60、65℃时,进行酯交换反应动力学研究。结果表明利用静态混合管式反应器连续化制备生物柴油反应的表观反应级数为1.3,活化能为11.74 kJ/mol。连续化反应的时间可控制在15 min内,并且在适宜的反应条件下,酯交换反应的转化率高于98%。     

管道式连续化制备生物柴油节能及经济性评估

对年产1000t管道式反应过程进行了节能分析,利用中试相关数据,讨论了管道式连续化制备生物柴油能耗状况.结果表明,与传统釜式酯交换反应相比,管道式反应由于采用了共溶剂技术,使油脂酯交换反应时间由2h缩短到20 min,大大缩短了反应周期,提高了生产工段安全性,使生物柴油产品综合能耗由釜式反应的28.669 kg/t(以...     

富酸油脂无催化快速酯化降酸工艺研究

对富酸油脂进行了甘油无催化酯化降酸的研究,通过实验优化得到了最佳反应条件：甘油与脂肪酸的物质的量比为1.2∶1,反应温度为240℃,反应2 h,酸值即可降至1.66 mg/g以下。优化工艺实现了富酸油脂2 h内快速降酸的目的,且所得产品可直接通过酯交换反应制备生物柴油,FT-IR分析确认了羧酸的消失和甘油酯的形成。GPC分析结果表明了降酸后油脂的组成为甘油三酯21.93%、甘油双酯37.93%和甘油单酯40.14%,所得生物柴油组成仅为脂肪酸甲酯。此外,该工艺的完善还直接补全了“不同酸值油脂制备生物柴油的工艺路线图”,对生物柴油行业发展具有一定的借鉴价值。     

高酸价酸化油制备生物柴油研究

以酸化油为原料两步法制备生物柴油,以对甲苯磺酸作为催化剂,采用分段反应的预酯化工艺先将酸化油脂中的脂肪酸转变为脂肪酸甲酯(FAME),然后再碱催化酯交换反应得到生物柴油.考察了甲醇与脂肪酸物质的量之比(醇酸比)等不同条件对预酯化反应的影响.通过正交试验得到最佳的预酯化反应条件并研究了油脂酸价对碱催化酯交换的影响.试验结果表明,各因素对酯化反应影响大小依次为反应温度、催化剂用量、醇酸比和反应时间,预酯化最优化的工艺条件为:醇酸比10∶1,催化剂用量3%,反应时间150min,反应温度70℃,通过分段反应的预酯化工艺,反应时间缩短了1h,催化剂回收率达到90%以上.进行碱催化酯交换的油脂要求酸价不能大于4mg/g.     

固体碱催化沉香籽油制备生物柴油的研究

沉香籽在南方资源量大,内含油脂丰富,其中C18组分高达80.4%,在我国能源短缺的大背景下具有重要的开发意义。本研究自制负载型固体碱催化剂KF/CaO用于催化沉香籽油进行酯交换反应制备脂肪酸甲酯类生物柴油。通过表征发现催化剂KF/CaO微观呈多层片状结构,比表面积为107±0.5 m2/g,碱强度H_=15.0~18.4。通过酯交换反应发现KF/Ca O催化剂具有较好的催化效果,酯交换转化率达到98.7%,能够保持高转化率重复使用3次。生物柴油产品主要指标符合GB/T 20828-2014的要求,红外谱图显示符合脂肪酸甲酯官能团的特征。     

光皮树油催化裂解制备生物液体燃料试验

以光皮树油为原料，采用自制负载型催化剂氧化镧进行催化裂解反应，通过单因素试验优化催化裂解工艺。结果表明：自制负载型催化剂氧化镧具有很好的催化效果。光皮树油催化裂解生物燃料最佳工艺参数为反应温度500℃，反应催化剂用量1.0％，反应时间80min。在此优化条件下，光皮树油催化裂解液相燃料油产品得率在82．0％以上。     

含钙微胶囊粉末光皮树油的制备及其性能

光皮树是一种高产的木本油料树种,其树油的不饱和脂肪酸含量高,具有很高的应用价值。利用微胶囊技术制备微胶囊粉末光皮树油,研究了不同质量配比的硬脂酰乳酸钙和甜菜碱复配乳化剂对光皮树油微胶囊化效率和载油量的影响,确定了喷雾干燥技术制备微胶囊粉末光皮树油产品的工艺条件。结果表明:当硬脂酰乳酸钙/甜菜碱质量比为2/3时复配乳化剂乳化光皮树油形成的乳液不分层,具有较好的乳化稳定性,粒径大小为16.37μm,且喷雾干燥制备的微胶囊粉末光皮树油产品颗粒均匀、细腻、干燥。经扫描电镜观察,以该乳化剂质量比例制备的微胶囊粉末光皮树油颗粒外形较圆整,大小分布较均匀,表面光滑,含水量为4.28%,对光皮树油具有较好的包埋效果,其包埋率及载油量分别为91.2%和28.0%,硬脂酰乳酸钙/甜菜碱(质量比为2/3)这一复配组合的乳化剂是制备高包埋率及高载油量微胶囊粉末光皮树油的理想乳化剂。制备的微胶囊可同时补能和补钙,对于提高微胶囊油脂粉品质具有极为重要的意义。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.